aboutsummaryrefslogtreecommitdiffstats
path: root/erts/doc/src/erlang.xml
blob: daf3002ec707c99a8e9d6937fd35fd6be953b820 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
5775
5776
5777
5778
5779
5780
5781
5782
5783
5784
5785
5786
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
5817
5818
5819
5820
5821
5822
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
5857
5858
5859
5860
5861
5862
5863
5864
5865
5866
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
5903
5904
5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
5920
5921
5922
5923
5924
5925
5926
5927
5928
5929
5930
5931
5932
5933
5934
5935
5936
5937
5938
5939
5940
5941
5942
5943
5944
5945
5946
5947
5948
5949
5950
5951
5952
5953
5954
5955
5956
5957
5958
5959
5960
5961
5962
5963
5964
5965
5966
5967
5968
5969
5970
5971
5972
5973
5974
5975
5976
5977
5978
5979
5980
5981
5982
5983
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
6006
6007
6008
6009
6010
6011
6012
6013
6014
6015
6016
6017
6018
6019
6020
6021
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
6037
6038
6039
6040
6041
6042
6043
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
6059
6060
6061
6062
6063
6064
6065
6066
6067
6068
6069
6070
6071
6072
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
6098
6099
6100
6101
6102
6103
6104
6105
6106
6107
6108
6109
6110
6111
6112
6113
6114
6115
6116
6117
6118
6119
6120
6121
6122
6123
6124
6125
6126
6127
6128
6129
6130
6131
6132
6133
6134
6135
6136
6137
6138
6139
6140
6141
6142
6143
6144
6145
6146
6147
6148
6149
6150
6151
6152
6153
6154
6155
6156
6157
6158
6159
6160
6161
6162
6163
6164
6165
6166
6167
6168
6169
6170
6171
6172
6173
6174
6175
6176
6177
6178
6179
6180
6181
6182
6183
6184
6185
6186
6187
6188
6189
6190
6191
6192
6193
6194
6195
6196
6197
6198
6199
6200
6201
6202
6203
6204
6205
6206
6207
6208
6209
6210
6211
6212
6213
6214
6215
6216
6217
6218
6219
6220
6221
6222
6223
6224
6225
6226
6227
6228
6229
6230
6231
6232
6233
6234
6235
6236
6237
6238
6239
6240
6241
6242
6243
6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
6270
6271
6272
6273
6274
6275
6276
6277
6278
6279
6280
6281
6282
6283
6284
6285
6286
6287
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
6304
6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
6315
6316
6317
6318
6319
6320
6321
6322
6323
6324
6325
6326
6327
6328
6329
6330
6331
6332
6333
6334
6335
6336
6337
6338
6339
6340
6341
6342
6343
6344
6345
6346
6347
6348
6349
6350
6351
6352
6353
6354
6355
6356
6357
6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
6384
6385
6386
6387
6388
6389
6390
6391
6392
6393
6394
6395
6396
6397
6398
6399
6400
6401
6402
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
6438
6439
6440
6441
6442
6443
6444
6445
6446
6447
6448
6449
6450
6451
6452
6453
6454
6455
6456
6457
6458
6459
6460
6461
6462
6463
6464
6465
6466
6467
6468
6469
6470
6471
6472
6473
6474
6475
6476
6477
6478
6479
6480
6481
6482
6483
6484
6485
6486
6487
6488
6489
6490
6491
6492
6493
6494
6495
6496
6497
6498
6499
6500
6501
6502
6503
6504
6505
6506
6507
6508
6509
6510
6511
6512
6513
6514
6515
6516
6517
6518
6519
6520
6521
6522
6523
6524
6525
6526
6527
6528
6529
6530
6531
6532
6533
6534
6535
6536
6537
6538
6539
6540
6541
6542
6543
6544
6545
6546
6547
6548
6549
6550
6551
6552
6553
6554
6555
6556
6557
6558
6559
6560
6561
6562
6563
6564
6565
6566
6567
6568
6569
6570
6571
6572
6573
6574
6575
6576
6577
6578
6579
6580
6581
6582
6583
6584
6585
6586
6587
6588
6589
6590
6591
6592
6593
6594
6595
6596
6597
6598
6599
6600
6601
6602
6603
6604
6605
6606
6607
6608
6609
6610
6611
6612
6613
6614
6615
6616
6617
6618
6619
6620
6621
6622
6623
6624
6625
6626
6627
6628
6629
6630
6631
6632
6633
6634
6635
6636
6637
6638
6639
6640
6641
6642
6643
6644
6645
6646
6647
6648
6649
6650
6651
6652
6653
6654
6655
6656
6657
6658
6659
6660
6661
6662
6663
6664
6665
6666
6667
6668
6669
6670
6671
6672
6673
6674
6675
6676
6677
6678
6679
6680
6681
6682
6683
6684
6685
6686
6687
6688
6689
6690
6691
6692
6693
6694
6695
6696
6697
6698
6699
6700
6701
6702
6703
6704
6705
6706
6707
6708
6709
6710
6711
6712
6713
6714
6715
6716
6717
6718
6719
6720
6721
6722
6723
6724
6725
6726
6727
6728
6729
6730
6731
6732
6733
6734
6735
6736
6737
6738
6739
6740
6741
6742
6743
6744
6745
6746
6747
6748
6749
6750
6751
6752
6753
6754
6755
6756
6757
6758
6759
6760
6761
6762
6763
6764
6765
6766
6767
6768
6769
6770
6771
6772
6773
6774
6775
6776
6777
6778
6779
6780
6781
6782
6783
6784
6785
6786
6787
6788
6789
6790
6791
6792
6793
6794
6795
6796
6797
6798
6799
6800
6801
6802
6803
6804
6805
6806
6807
6808
6809
6810
6811
6812
6813
6814
6815
6816
6817
6818
6819
6820
6821
6822
6823
6824
6825
6826
6827
6828
6829
6830
6831
6832
6833
6834
6835
6836
6837
6838
6839
6840
6841
6842
6843
6844
6845
6846
6847
6848
6849
6850
6851
6852
6853
6854
6855
6856
6857
6858
6859
6860
6861
6862
6863
6864
6865
6866
6867
6868
6869
6870
6871
6872
6873
6874
6875
6876
6877
6878
6879
6880
6881
6882
6883
6884
6885
6886
6887
6888
6889
6890
6891
6892
6893
6894
6895
6896
6897
6898
6899
6900
6901
6902
6903
6904
6905
6906
6907
6908
6909
6910
6911
6912
6913
6914
6915
6916
6917
6918
6919
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
6931
6932
6933
6934
6935
6936
6937
6938
6939
6940
6941
6942
6943
6944
6945
6946
6947
6948
6949
6950
6951
6952
6953
6954
6955
6956
6957
6958
6959
6960
6961
6962
6963
6964
6965
6966
6967
6968
6969
6970
6971
6972
6973
6974
6975
6976
6977
6978
6979
6980
6981
6982
6983
6984
6985
6986
6987
6988
6989
6990
6991
6992
6993
6994
6995
6996
6997
6998
6999
7000
7001
7002
7003
7004
7005
7006
7007
7008
7009
7010
7011
7012
7013
7014
7015
7016
7017
7018
7019
7020
7021
7022
7023
7024
7025
7026
7027
7028
7029
7030
7031
7032
7033
7034
7035
7036
7037
7038
7039
7040
7041
7042
7043
7044
7045
7046
7047
7048
7049
7050
7051
7052
7053
7054
7055
7056
7057
7058
7059
7060
7061
7062
7063
7064
7065
7066
7067
7068
7069
7070
7071
7072
7073
7074
7075
7076
7077
7078
7079
7080
7081
7082
7083
7084
7085
7086
7087
7088
7089
7090
7091
7092
7093
7094
7095
7096
7097
7098
7099
7100
7101
7102
7103
7104
7105
7106
7107
7108
7109
7110
7111
7112
7113
7114
7115
7116
7117
7118
7119
7120
7121
7122
7123
7124
7125
7126
7127
7128
7129
7130
7131
7132
7133
7134
7135
7136
7137
7138
7139
7140
7141
7142
7143
7144
7145
7146
7147
7148
7149
7150
7151
7152
7153
7154
7155
7156
7157
7158
7159
7160
7161
7162
7163
7164
7165
7166
7167
7168
7169
7170
7171
7172
7173
7174
7175
7176
7177
7178
7179
7180
7181
7182
7183
7184
7185
7186
7187
7188
7189
7190
7191
7192
7193
7194
7195
7196
7197
7198
7199
7200
7201
7202
7203
7204
7205
7206
7207
7208
7209
7210
7211
7212
7213
7214
7215
7216
7217
7218
7219
7220
7221
7222
7223
7224
7225
7226
7227
7228
7229
7230
7231
7232
7233
7234
7235
7236
7237
7238
7239
7240
7241
7242
7243
7244
7245
7246
7247
7248
7249
7250
7251
7252
7253
7254
7255
7256
7257
7258
7259
7260
7261
7262
7263
7264
7265
7266
7267
7268
7269
7270
7271
7272
7273
7274
7275
7276
7277
7278
7279
7280
7281
7282
7283
7284
7285
7286
7287
7288
7289
7290
7291
7292
7293
7294
7295
7296
7297
7298
7299
7300
7301
7302
7303
7304
7305
7306
7307
7308
7309
7310
7311
7312
7313
7314
7315
7316
7317
7318
7319
7320
7321
7322
7323
7324
7325
7326
7327
7328
7329
7330
7331
7332
7333
7334
7335
7336
7337
7338
7339
7340
7341
7342
7343
7344
7345
7346
7347
7348
7349
7350
7351
7352
7353
7354
7355
7356
7357
7358
7359
7360
7361
7362
7363
7364
7365
7366
7367
7368
7369
7370
7371
7372
7373
7374
7375
7376
7377
7378
7379
7380
7381
7382
7383
7384
7385
7386
7387
7388
7389
7390
7391
7392
7393
7394
7395
7396
7397
7398
7399
7400
7401
7402
7403
7404
7405
7406
7407
7408
7409
7410
7411
7412
7413
7414
7415
7416
7417
7418
7419
7420
7421
7422
7423
7424
7425
7426
7427
7428
7429
7430
7431
7432
7433
7434
7435
7436
7437
7438
7439
7440
7441
7442
7443
7444
7445
7446
7447
7448
7449
7450
7451
7452
7453
7454
7455
7456
7457
7458
7459
7460
7461
7462
7463
7464
7465
7466
7467
7468
7469
7470
7471
7472
7473
7474
7475
7476
7477
7478
7479
7480
7481
7482
7483
7484
7485
7486
7487
7488
7489
7490
7491
7492
7493
7494
7495
7496
7497
7498
7499
7500
7501
7502
7503
7504
7505
7506
7507
7508
7509
7510
7511
7512
7513
7514
7515
7516
7517
7518
7519
7520
7521
7522
7523
7524
7525
7526
7527
7528
7529
7530
7531
7532
7533
7534
7535
7536
7537
7538
7539
7540
7541
7542
7543
7544
7545
7546
7547
7548
7549
7550
7551
7552
7553
7554
7555
7556
7557
7558
7559
7560
7561
7562
7563
7564
7565
7566
7567
7568
7569
7570
7571
7572
7573
7574
7575
7576
7577
7578
7579
7580
7581
7582
7583
7584
7585
7586
7587
7588
7589
7590
7591
7592
7593
7594
7595
7596
7597
7598
7599
7600
7601
7602
7603
7604
7605
7606
7607
7608
7609
7610
7611
7612
7613
7614
7615
7616
7617
7618
7619
7620
7621
7622
7623
7624
7625
7626
7627
7628
7629
7630
7631
7632
7633
7634
7635
7636
7637
7638
7639
7640
7641
7642
7643
7644
7645
7646
7647
7648
7649
7650
7651
7652
7653
7654
7655
7656
7657
7658
7659
7660
7661
7662
7663
7664
7665
7666
7667
7668
7669
7670
7671
7672
7673
7674
7675
7676
7677
7678
7679
7680
7681
7682
7683
7684
7685
7686
7687
7688
7689
7690
7691
7692
7693
7694
7695
7696
7697
7698
7699
7700
7701
7702
7703
7704
7705
7706
7707
7708
7709
7710
7711
7712
7713
7714
7715
7716
7717
7718
7719
7720
7721
7722
7723
7724
7725
7726
7727
7728
7729
7730
7731
7732
7733
7734
7735
7736
7737
7738
7739
7740
7741
7742
7743
7744
7745
7746
7747
7748
7749
7750
7751
7752
7753
7754
7755
7756
7757
7758
7759
7760
7761
7762
7763
7764
7765
7766
7767
7768
7769
7770
7771
7772
7773
7774
7775
7776
7777
7778
7779
7780
7781
7782
7783
7784
7785
7786
7787
7788
7789
7790
7791
7792
7793
7794
7795
7796
7797
7798
7799
7800
7801
7802
7803
7804
7805
7806
7807
7808
7809
7810
7811
7812
7813
7814
7815
7816
7817
7818
7819
7820
7821
7822
7823
7824
7825
7826
7827
7828
7829
7830
7831
7832
7833
7834
7835
7836
7837
7838
7839
7840
7841
7842
7843
7844
7845
7846
7847
7848
7849
7850
7851
7852
7853
7854
7855
7856
7857
7858
7859
7860
7861
7862
7863
7864
7865
7866
7867
7868
7869
7870
7871
7872
7873
7874
7875
7876
7877
7878
7879
7880
7881
7882
7883
7884
7885
7886
7887
7888
7889
7890
7891
7892
7893
7894
7895
7896
7897
7898
7899
7900
7901
7902
7903
7904
7905
7906
7907
7908
7909
7910
7911
7912
7913
7914
7915
7916
7917
7918
7919
7920
7921
7922
7923
7924
7925
7926
7927
7928
7929
7930
7931
7932
7933
7934
7935
7936
7937
7938
7939
7940
7941
7942
7943
7944
7945
7946
7947
7948
7949
7950
7951
7952
7953
7954
7955
7956
7957
7958
7959
7960
7961
7962
7963
7964
7965
7966
7967
7968
7969
7970
7971
7972
7973
7974
7975
7976
7977
7978
7979
7980
7981
7982
7983
7984
7985
7986
7987
7988
7989
7990
7991
7992
7993
7994
7995
7996
7997
7998
7999
8000
8001
8002
8003
8004
8005
8006
8007
8008
8009
8010
8011
8012
8013
8014
8015
8016
8017
8018
8019
8020
8021
8022
8023
8024
8025
8026
8027
8028
8029
8030
8031
8032
8033
8034
8035
8036
8037
8038
8039
8040
8041
8042
8043
8044
8045
8046
8047
8048
8049
8050
8051
8052
8053
8054
8055
8056
8057
8058
8059
8060
8061
8062
8063
8064
8065
8066
8067
8068
8069
8070
8071
8072
8073
8074
8075
8076
8077
8078
8079
8080
8081
8082
8083
8084
8085
8086
8087
8088
8089
8090
8091
8092
8093
8094
8095
8096
8097
8098
8099
8100
8101
8102
8103
8104
8105
8106
8107
8108
8109
8110
8111
8112
8113
8114
8115
8116
8117
8118
8119
8120
8121
8122
8123
8124
8125
8126
8127
8128
8129
8130
8131
8132
8133
8134
8135
8136
8137
8138
8139
8140
8141
8142
8143
8144
8145
8146
8147
8148
8149
8150
8151
8152
8153
8154
8155
8156
8157
8158
8159
8160
8161
8162
8163
8164
8165
8166
8167
8168
8169
8170
8171
8172
8173
8174
8175
8176
8177
8178
8179
8180
8181
8182
8183
8184
8185
8186
8187
8188
8189
8190
8191
8192
8193
8194
8195
8196
8197
8198
8199
8200
8201
8202
8203
8204
8205
8206
8207
8208
8209
8210
8211
8212
8213
8214
8215
8216
8217
8218
8219
8220
8221
8222
8223
8224
8225
8226
8227
8228
8229
8230
8231
8232
8233
8234
8235
8236
8237
8238
8239
8240
8241
8242
8243
8244
8245
8246
8247
8248
8249
8250
8251
8252
8253
8254
8255
8256
8257
8258
8259
8260
8261
8262
8263
8264
8265
8266
8267
8268
8269
8270
8271
8272
8273
8274
8275
8276
8277
8278
8279
8280
8281
8282
8283
8284
8285
8286
8287
8288
8289
8290
8291
8292
8293
8294
8295
8296
8297
8298
8299
8300
8301
8302
8303
8304
8305
8306
8307
8308
8309
8310
8311
8312
8313
8314
8315
8316
8317
8318
8319
8320
8321
8322
8323
8324
8325
8326
8327
8328
8329
8330
8331
8332
8333
8334
8335
8336
8337
8338
8339
8340
8341
8342
8343
8344
8345
8346
8347
8348
8349
8350
8351
8352
8353
8354
8355
8356
8357
8358
8359
8360
8361
8362
8363
8364
8365
8366
8367
8368
8369
8370
8371
8372
8373
8374
8375
8376
8377
8378
8379
8380
8381
8382
8383
8384
8385
8386
8387
8388
8389
8390
8391
8392
8393
8394
8395
8396
8397
8398
8399
8400
8401
8402
8403
8404
8405
8406
8407
8408
8409
8410
8411
8412
8413
8414
8415
8416
8417
8418
8419
8420
8421
8422
8423
8424
8425
8426
8427
8428
8429
8430
8431
8432
8433
8434
8435
8436
8437
8438
8439
8440
8441
8442
8443
8444
8445
8446
8447
8448
8449
8450
8451
8452
8453
8454
8455
8456
8457
8458
8459
8460
8461
8462
8463
8464
8465
8466
8467
8468
8469
8470
8471
8472
8473
8474
8475
8476
8477
8478
8479
8480
8481
8482
8483
8484
8485
8486
8487
8488
8489
8490
8491
8492
8493
8494
8495
8496
8497
8498
8499
8500
8501
8502
8503
8504
8505
8506
8507
8508
8509
8510
8511
8512
8513
8514
8515
8516
8517
8518
8519
8520
8521
8522
8523
8524
8525
8526
8527
8528
8529
8530
8531
8532
8533
8534
8535
8536
8537
8538
8539
8540
8541
8542
8543
8544
8545
8546
8547
8548
8549
8550
8551
8552
8553
8554
8555
8556
8557
8558
8559
8560
8561
8562
8563
8564
8565
8566
8567
8568
8569
8570
8571
8572
8573
8574
8575
8576
8577
8578
8579
8580
8581
8582
8583
8584
8585
8586
8587
8588
8589
8590
8591
8592
8593
8594
8595
8596
8597
8598
8599
8600
8601
8602
8603
8604
8605
8606
8607
8608
8609
8610
8611
8612
8613
8614
8615
8616
8617
8618
8619
8620
8621
8622
8623
8624
8625
8626
8627
8628
8629
8630
8631
8632
8633
8634
8635
8636
8637
8638
8639
8640
8641
8642
8643
8644
8645
8646
8647
8648
8649
8650
8651
8652
8653
8654
8655
8656
8657
8658
8659
8660
8661
8662
8663
8664
8665
8666
8667
8668
8669
8670
8671
8672
8673
8674
8675
8676
8677
8678
8679
8680
8681
8682
8683
8684
8685
8686
8687
8688
8689
8690
8691
8692
8693
8694
8695
8696
8697
8698
8699
8700
8701
8702
8703
8704
8705
8706
8707
8708
8709
8710
8711
8712
8713
8714
8715
8716
8717
8718
8719
8720
8721
8722
8723
8724
8725
8726
8727
8728
8729
8730
8731
8732
8733
8734
8735
8736
8737
8738
8739
8740
8741
8742
8743
8744
8745
8746
8747
8748
8749
8750
8751
8752
8753
8754
8755
8756
8757
8758
8759
8760
8761
8762
8763
8764
8765
8766
8767
8768
8769
8770
8771
8772
8773
8774
8775
8776
8777
8778
8779
8780
8781
8782
8783
8784
8785
8786
8787
8788
8789
8790
8791
8792
8793
8794
8795
8796
8797
8798
8799
8800
8801
8802
8803
8804
8805
8806
8807
8808
8809
8810
8811
8812
8813
8814
8815
8816
8817
8818
8819
8820
8821
8822
8823
8824
8825
8826
8827
8828
8829
8830
8831
8832
8833
8834
8835
8836
8837
8838
8839
8840
8841
8842
8843
8844
8845
8846
8847
8848
8849
8850
8851
8852
8853
8854
8855
8856
8857
8858
8859
8860
8861
8862
8863
8864
8865
8866
8867
8868
8869
8870
8871
8872
8873
8874
8875
8876
8877
8878
8879
8880
8881
8882
8883
8884
8885
8886
8887
8888
8889
8890
8891
8892
8893
8894
8895
8896
8897
8898
8899
8900
8901
8902
8903
8904
8905
8906
8907
8908
8909
8910
8911
8912
8913
8914
8915
8916
8917
8918
8919
8920
8921
8922
8923
8924
8925
8926
8927
8928
8929
8930
8931
8932
8933
8934
8935
8936
8937
8938
8939
8940
8941
8942
8943
8944
8945
8946
8947
8948
8949
8950
8951
8952
8953
8954
8955
8956
8957
8958
8959
8960
8961
8962
8963
8964
8965
8966
8967
8968
8969
8970
8971
8972
8973
8974
8975
8976
8977
8978
8979
8980
8981
8982
8983
8984
8985
8986
8987
8988
8989
8990
8991
8992
8993
8994
8995
8996
8997
8998
8999
9000
9001
9002
9003
9004
9005
9006
9007
9008
9009
9010
9011
9012
9013
9014
9015
9016
9017
9018
9019
9020
9021
9022
9023
9024
9025
9026
9027
9028
9029
9030
9031
9032
9033
9034
9035
9036
9037
9038
9039
9040
9041
9042
9043
9044
9045
9046
9047
9048
9049
9050
9051
9052
9053
9054
9055
9056
9057
9058
9059
9060
9061
9062
9063
9064
9065
9066
9067
9068
9069
9070
9071
9072
9073
9074
9075
9076
9077
9078
9079
9080
9081
9082
9083
9084
9085
9086
9087
9088
9089
9090
9091
9092
9093
9094
9095
9096
9097
9098
9099
9100
9101
9102
9103
9104
9105
9106
9107
9108
9109
9110
9111
9112
9113
9114
9115
9116
9117
9118
9119
9120
9121
9122
9123
9124
9125
9126
9127
9128
9129
9130
9131
9132
9133
9134
9135
9136
9137
9138
9139
9140
9141
9142
9143
9144
9145
9146
9147
9148
9149
9150
9151
9152
9153
9154
9155
9156
9157
9158
9159
9160
9161
9162
9163
9164
9165
9166
9167
9168
9169
9170
9171
9172
9173
9174
9175
9176
9177
9178
9179
9180
9181
9182
9183
9184
9185
9186
9187
9188
9189
9190
9191
9192
9193
9194
9195
9196
9197
9198
9199
9200
9201
9202
9203
9204
9205
9206
9207
9208
9209
9210
9211
9212
9213
9214
9215
9216
9217
9218
9219
9220
9221
9222
9223
9224
9225
9226
9227
9228
9229
9230
9231
9232
9233
9234
9235
9236
9237
9238
9239
9240
9241
9242
9243
9244
9245
9246
9247
9248
9249
9250
9251
9252
9253
9254
9255
9256
9257
9258
9259
9260
9261
9262
9263
9264
9265
9266
9267
9268
9269
9270
9271
9272
9273
9274
9275
9276
9277
9278
9279
9280
9281
9282
9283
9284
9285
9286
9287
9288
9289
9290
9291
9292
9293
9294
9295
9296
9297
9298
9299
9300
9301
9302
9303
9304
9305
9306
9307
9308
9309
9310
9311
9312
9313
9314
9315
9316
9317
9318
9319
9320
9321
9322
9323
9324
9325
9326
9327
9328
9329
9330
9331
9332
9333
9334
9335
9336
9337
9338
9339
9340
9341
9342
9343
9344
9345
9346
9347
9348
9349
9350
9351
9352
9353
9354
9355
9356
9357
9358
9359
9360
9361
9362
9363
9364
9365
9366
9367
9368
9369
9370
9371
9372
9373
9374
9375
9376
9377
9378
9379
9380
9381
9382
9383
9384
9385
9386
9387
9388
9389
9390
9391
9392
9393
9394
9395
9396
9397
9398
9399
9400
9401
9402
9403
9404
9405
9406
9407
9408
9409
9410
9411
9412
9413
9414
9415
9416
9417
9418
9419
9420
9421
9422
9423
9424
9425
9426
9427
9428
9429
9430
9431
9432
9433
9434
9435
9436
9437
9438
9439
9440
9441
9442
9443
9444
9445
9446
9447
9448
9449
9450
9451
9452
9453
9454
9455
9456
9457
9458
9459
9460
9461
9462
9463
9464
9465
9466
9467
9468
9469
9470
9471
9472
9473
9474
9475
9476
9477
9478
9479
9480
9481
9482
9483
9484
9485
9486
9487
9488
9489
9490
9491
9492
9493
9494
9495
9496
9497
9498
9499
9500
9501
9502
9503
9504
9505
9506
9507
9508
9509
9510
9511
9512
9513
9514
9515
9516
9517
9518
9519
9520
9521
9522
9523
9524
9525
9526
9527
9528
9529
9530
9531
9532
9533
9534
9535
9536
9537
9538
9539
9540
9541
9542
9543
9544
9545
9546
9547
9548
9549
9550
9551
9552
9553
9554
9555
9556
9557
9558
9559
9560
9561
9562
9563
9564
9565
9566
9567
9568
9569
9570
9571
9572
9573
9574
9575
9576
9577
9578
9579
9580
9581
9582
9583
9584
9585
9586
9587
9588
9589
9590
9591
9592
9593
9594
9595
9596
9597
9598
9599
9600
9601
9602
9603
9604
9605
9606
9607
9608
9609
9610
9611
9612
9613
9614
9615
9616
9617
9618
9619
9620
9621
9622
9623
9624
9625
9626
9627
9628
9629
9630
9631
9632
9633
9634
9635
9636
9637
9638
9639
9640
9641
9642
9643
9644
9645
9646
9647
9648
9649
9650
9651
9652
9653
9654
9655
9656
9657
9658
9659
9660
9661
9662
9663
9664
9665
9666
9667
9668
9669
9670
9671
9672
9673
9674
9675
9676
9677
9678
9679
9680
9681
9682
9683
9684
9685
9686
9687
9688
9689
9690
9691
9692
9693
9694
9695
9696
9697
9698
9699
9700
9701
9702
9703
9704
9705
9706
9707
9708
9709
9710
9711
9712
9713
9714
9715
9716
9717
9718
9719
9720
9721
9722
9723
9724
9725
9726
9727
9728
9729
9730
9731
9732
9733
9734
9735
9736
9737
9738
9739
9740
9741
9742
9743
9744
9745
9746
9747
9748
9749
9750
9751
9752
9753
9754
9755
9756
9757
9758
9759
9760
9761
9762
9763
9764
9765
9766
9767
9768
9769
9770
9771
9772
9773
9774
9775
9776
9777
9778
9779
9780
9781
9782
9783
9784
9785
9786
9787
9788
9789
9790
9791
9792
9793
9794
9795
9796
9797
9798
9799
9800
9801
9802
9803
9804
9805
9806
9807
9808
9809
9810
9811
9812
9813
9814
9815
9816
9817
9818
9819
9820
9821
9822
9823
9824
9825
9826
9827
9828
9829
9830
9831
9832
9833
9834
9835
9836
9837
9838
9839
9840
9841
9842
9843
9844
9845
9846
9847
9848
9849
9850
9851
9852
9853
9854
9855
9856
9857
9858
9859
9860
9861
9862
9863
9864
9865
9866
9867
9868
9869
9870
9871
9872
9873
9874
9875
9876
9877
9878
9879
9880
9881
9882
9883
9884
9885
9886
9887
9888
9889
9890
9891
9892
9893
9894
9895
9896
9897
9898
9899
9900
9901
9902
9903
9904
9905
9906
9907
9908
9909
9910
9911
9912
9913
9914
9915
9916
9917
9918
9919
9920
9921
9922
9923
9924
9925
9926
9927
9928
9929
9930
9931
9932
9933
9934
9935
9936
9937
9938
9939
9940
9941
9942
9943
9944
9945
9946
9947
9948
9949
9950
9951
9952
9953
9954
9955
9956
9957
9958
9959
9960
9961
9962
9963
9964
9965
9966
9967
9968
9969
9970
9971
9972
9973
9974
9975
9976
9977
9978
9979
9980
9981
9982
9983
9984
9985
9986
9987
9988
9989
9990
9991
9992
9993
9994
9995
9996
9997
9998
9999
10000
10001
10002
10003
10004
10005
10006
10007
10008
10009
10010
10011
10012
10013
10014
10015
10016
10017
10018
10019
10020
10021
10022
10023
10024
10025
10026
10027
10028
10029
10030
10031
10032
10033
10034
10035
10036
10037
10038
10039
10040
10041
10042
10043
10044
10045
10046
10047
10048
10049
10050
10051
10052
10053
10054
10055
10056
10057
10058
10059
10060
10061
10062
10063
10064
10065
10066
10067
10068
10069
10070
10071
10072
10073
10074
10075
10076
10077
10078
10079
10080
10081
10082
10083
10084
10085
10086
10087
10088
10089
10090
10091
10092
10093
10094
10095
10096
10097
10098
10099
10100
10101
10102
10103
10104
10105
10106
10107
10108
10109
10110
10111
10112
10113
10114
10115
10116
10117
10118
10119
10120
10121
10122
10123
10124
10125
10126
10127
10128
10129
10130
10131
10132
10133
10134
10135
10136
10137
10138
10139
10140
10141
10142
10143
10144
10145
10146
10147
10148
10149
10150
10151
10152
10153
10154
10155
10156
10157
10158
10159
10160
10161
10162
10163
10164
10165
10166
10167
10168
10169
10170
10171
10172
10173
10174
10175
10176
10177
10178
10179
10180
10181
10182
10183
10184
10185
10186
10187
10188
10189
10190
10191
10192
10193
10194
10195
10196
10197
10198
10199
10200
10201
10202
10203
10204
10205
10206
10207
10208
10209
10210
10211
10212
10213
10214
10215
10216
10217
10218
10219
10220
10221
10222
10223
10224
10225
10226
10227
10228
10229
10230
10231
10232
10233
10234
10235
10236
10237
10238
10239
10240
10241
10242
10243
10244
10245
10246
10247
10248
10249
10250
10251
10252
10253
10254
10255
10256
10257
10258
10259
10260
10261
10262
10263
10264
10265
10266
10267
10268
10269
10270
10271
10272
10273
10274
10275
10276
10277
10278
10279
10280
10281
10282
10283
10284
10285
10286
10287
10288
10289
10290
10291
10292
10293
10294
10295
10296
10297
10298
10299
10300
10301
10302
10303
10304
10305
10306
10307
10308
10309
10310
10311
10312
10313
10314
10315
10316
10317
10318
10319
10320
10321
10322
10323
10324
10325
10326
10327
10328
10329
10330
10331
10332
10333
10334
10335
10336
10337
10338
10339
10340
10341
10342
10343
10344
10345
10346
10347
10348
10349
10350
10351
10352
10353
10354
10355
10356
10357
10358
10359
10360
10361
10362
10363
10364
10365
10366
10367
10368
10369
10370
10371
10372
10373
10374
10375
10376
10377
10378
10379
10380
10381
10382
10383
10384
10385
10386
10387
10388
10389
10390
10391
10392
10393
10394
10395
10396
10397
10398
10399
10400
10401
10402
10403
10404
10405
10406
10407
10408
10409
10410
10411
10412
10413
10414
10415
10416
10417
10418
10419
10420
10421
10422
10423
10424
10425
10426
10427
10428
10429
10430
10431
10432
10433
10434
10435
10436
10437
10438
10439
10440
10441
10442
10443
10444
10445
10446
10447
10448
10449
10450
10451
10452
10453
10454
10455
10456
10457
10458
10459
10460
10461
10462
10463
10464
10465
10466
10467
10468
10469
10470
10471
10472
10473
10474
10475
10476
10477
10478
10479
10480
10481
10482
10483
10484
10485
10486
10487
10488
10489
10490
10491
10492
10493
10494
10495
10496
10497
10498
10499
10500
10501
10502
10503
10504
10505
10506
10507
10508
10509
10510
10511
10512
10513
10514
10515
10516
10517
10518
10519
10520
10521
10522
10523
10524
10525
10526
10527
10528
10529
10530
10531
10532
10533
10534
10535
10536
10537
10538
10539
10540
10541
10542
10543
10544
10545
10546
10547
10548
10549
10550
10551
10552
10553
10554
10555
10556
10557
10558
10559
10560
10561
10562
10563
10564
10565
10566
10567
10568
10569
10570
10571
10572
10573
10574
10575
10576
10577
10578
10579
10580
10581
10582
10583
10584
10585
10586
10587
10588
10589
10590
10591
10592
10593
10594
10595
10596
10597
10598
10599
10600
10601
10602
10603
10604
10605
10606
10607
10608
10609
10610
10611
10612
10613
10614
10615
10616
10617
10618
10619
10620
10621
10622
10623
10624
10625
10626
10627
10628
10629
10630
10631
10632
10633
10634
10635
10636
10637
10638
10639
10640
10641
10642
10643
10644
10645
10646
10647
10648
10649
10650
10651
10652
10653
10654
10655
10656
10657
10658
10659
10660
10661
10662
10663
10664
10665
10666
10667
10668
10669
10670
10671
10672
10673
10674
10675
10676
10677
10678
10679
10680
10681
10682
10683
10684
10685
10686
10687
10688
10689
10690
10691
10692
10693
10694
10695
10696
10697
10698
10699
10700
10701
10702
10703
10704
10705
10706
10707
10708
10709
10710
10711
10712
10713
10714
10715
10716
10717
10718
10719
10720
10721
10722
10723
10724
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1996</year><year>2017</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>erlang</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
    <file>erlang.xml</file>
  </header>
  <module>erlang</module>
  <modulesummary>The Erlang BIFs.</modulesummary>
  <description>
    <p>By convention, most Built-In Functions (BIFs) are included
      in this module. Some of the BIFs are viewed more
      or less as part of the Erlang programming language and are
      <em>auto-imported</em>. Thus, it is not necessary to specify the
      module name. For example, the calls <c>atom_to_list(Erlang)</c>
      and <c>erlang:atom_to_list(Erlang)</c> are identical.</p>

    <p>Auto-imported BIFs are listed without module prefix.
      BIFs listed with module prefix are not auto-imported.</p>

    <p>BIFs can fail for various reasons. All BIFs fail with
      reason <c>badarg</c> if they are called with arguments of an
      incorrect type. The other reasons are described in the
      description of each individual BIF.</p>

    <p>Some BIFs can be used in guard tests and are marked with
      "Allowed in guard tests".</p>
  </description>

  <datatypes>
    <datatype>
      <name>ext_binary()</name>
      <desc>
        <p>A binary data object, structured according to
          the Erlang external term format.</p>
      </desc>
    </datatype>
    <datatype>
      <name>iovec()</name>
      <desc>
        <p>A list of binaries. This datatype is useful to use
          together with <seealso marker="erl_nif#enif_inspect_iovec">
          <c>enif_inspect_iovec</c></seealso>.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="message_queue_data"></name>
      <desc>
        <p>See <seealso marker="#process_flag_message_queue_data">
          <c>process_flag(message_queue_data, MQD)</c></seealso>.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="timestamp"></name>
      <desc>
        <p>See <seealso marker="#timestamp/0">
          <c>erlang:timestamp/0</c></seealso>.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="time_unit"></name>
      <desc>
        <marker id="type_time_unit"/>
        <p>Supported time unit representations:</p>
        <taglist>
          <tag><c>PartsPerSecond :: integer() >= 1</c></tag>
          <item>
            <p>Time unit expressed in parts per second. That is,
              the time unit equals <c>1/PartsPerSecond</c> second.</p>
          </item>
          <tag><c>second</c></tag>
          <item>
            <p>Symbolic representation of the time unit
              represented by the integer <c>1</c>.</p>
          </item>
          <tag><c>millisecond</c></tag>
          <item>
            <p>Symbolic representation of the time unit
              represented by the integer <c>1000</c>.</p>
          </item>
          <tag><c>microsecond</c></tag>
          <item>
            <p>Symbolic representation of the time unit
              represented by the integer <c>1000000</c>.</p>
          </item>
          <tag><c>nanosecond</c></tag>
          <item>
            <p>Symbolic representation of the time unit
              represented by the integer <c>1000000000</c>.</p>
          </item>
          <tag><c>native</c></tag>
          <item>
            <p>Symbolic representation of the native time unit
              used by the Erlang runtime system.</p>
            <p>The <c>native</c> time unit is determined at
              runtime system start, and remains the same until
              the runtime system terminates. If a runtime system
              is stopped and then started again (even on the same
              machine), the <c>native</c> time unit of the new
              runtime system instance can differ from the
              <c>native</c> time unit of the old runtime system
              instance.</p>
            <p>One can get an approximation of the <c>native</c>
              time unit by calling
              <seealso marker="erlang:convert_time_unit/3">
              <c>erlang:convert_time_unit(1, second, native)</c></seealso>.
              The result equals the number
              of whole <c>native</c> time units per second. If
              the number of <c>native</c> time units per second does not
              add up to a whole number, the result is rounded downwards.</p>
            <note>
              <p>The value of the <c>native</c> time unit gives
                you more or less no information about the
                quality of time values. It sets a limit for the
                <seealso marker="time_correction#Time_Resolution">
                resolution</seealso> and for the
                <seealso marker="time_correction#Time_Precision">
                precision</seealso> of time values,
                but it gives no information about the
                <seealso marker="time_correction#Time_Accuracy">
                accuracy</seealso> of time values. The resolution of
                the <c>native</c> time unit and the resolution of time
                values can differ significantly.</p>
            </note>
          </item>
          <tag><c>perf_counter</c></tag>
          <item>
            <p>Symbolic representation of the performance counter
              time unit used by the Erlang runtime system.</p>
            <p>The <c>perf_counter</c> time unit behaves much in the same way
              as the <c>native</c> time unit. That is, it can differ between
              runtime restarts. To get values of this type, call
              <seealso marker="kernel:os#perf_counter/0">
              <c>os:perf_counter/0</c></seealso>.</p>
          </item>
	  <tag><seealso marker="#type_deprecated_time_unit"><c>deprecated_time_unit()</c></seealso></tag>
	  <item><p>
	    Deprecated symbolic representations kept for backwards-compatibility.
	  </p></item>
        </taglist>
        <p>The <c>time_unit/0</c> type can be extended.
          To convert time values between time units, use
          <seealso marker="#convert_time_unit/3">
          <c>erlang:convert_time_unit/3</c></seealso>.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="deprecated_time_unit"></name>
      <desc><marker id="type_deprecated_time_unit"/>
	<p>The <seealso marker="#type_time_unit"><c>time_unit()</c></seealso>
	type also consist of the following <em>deprecated</em> symbolic
	time units:</p>
	<taglist>
	  <tag><c>seconds</c></tag>
	  <item><p>Same as <seealso marker="#type_time_unit"><c>second</c></seealso>.</p></item>

	  <tag><c>milli_seconds</c></tag>
	  <item><p>Same as <seealso marker="#type_time_unit"><c>millisecond</c></seealso>.</p></item>

	  <tag><c>micro_seconds</c></tag>
	  <item><p>Same as <seealso marker="#type_time_unit"><c>microsecond</c></seealso>.</p></item>

	  <tag><c>nano_seconds</c></tag>
	  <item><p>Same as <seealso marker="#type_time_unit"><c>nanosecond</c></seealso>.</p></item>
	</taglist>
      </desc>
    </datatype>

    <datatype>
      <name name="dist_handle"></name>
      <desc>
        <p>An opaque handle identifing a distribution channel.</p>
      </desc>
    </datatype>

  </datatypes>

  <funcs>
    <func>
      <name name="abs" arity="1" clause_i="1"/>
      <name name="abs" arity="1" clause_i="2"/>
      <fsummary>Arithmetical absolute value.</fsummary>
      <type>
        <v>Float = float()</v>
        <v>Int = integer()</v>
      </type>
      <desc>
        <p>Returns an integer or float that is the arithmetical
          absolute value of <c><anno>Float</anno></c> or
          <c><anno>Int</anno></c>, for example:</p>
        <pre>
> <input>abs(-3.33).</input>
3.33
> <input>abs(-3).</input>
3</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="adler32" arity="1"/>
      <fsummary>Compute adler32 checksum.</fsummary>
      <desc>
        <p>Computes and returns the adler32 checksum for
          <c><anno>Data</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="adler32" arity="2"/>
      <fsummary>Compute adler32 checksum.</fsummary>
      <desc>
        <p>Continues computing the adler32 checksum by combining 
          the previous checksum, <c><anno>OldAdler</anno></c>, with
          the checksum of <c><anno>Data</anno></c>.</p>
        <p>The following code:</p>
        <code>
X = erlang:adler32(Data1),
Y = erlang:adler32(X,Data2).</code>
        <p>assigns the same value to <c>Y</c> as this:</p>
        <code>
Y = erlang:adler32([Data1,Data2]).</code>
      </desc>
    </func>

    <func>
      <name name="adler32_combine" arity="3"/>
      <fsummary>Combine two adler32 checksums.</fsummary>
      <desc>
        <p>Combines two previously computed adler32 checksums.
          This computation requires the size of the data object for
          the second checksum to be known.</p>
        <p>The following code:</p>
        <code>
Y = erlang:adler32(Data1),
Z = erlang:adler32(Y,Data2).</code>
        <p>assigns the same value to <c>Z</c> as this:</p>
        <code>
X = erlang:adler32(Data1),
Y = erlang:adler32(Data2),
Z = erlang:adler32_combine(X,Y,iolist_size(Data2)).</code>
      </desc>
    </func>

    <func>
      <name name="append_element" arity="2"/>
      <fsummary>Append an extra element to a tuple.</fsummary>
      <desc>
        <p>Returns a new tuple that has one element more than
          <c><anno>Tuple1</anno></c>, and contains the elements in
          <c><anno>Tuple1</anno></c>
          followed by <c><anno>Term</anno></c> as the last element.
          Semantically equivalent to
          <c>list_to_tuple(tuple_to_list(<anno>Tuple1</anno>) ++
          [<anno>Term</anno>])</c>, but much faster. Example:</p>
        <pre>
> <input>erlang:append_element({one, two}, three).</input>
{one,two,three}</pre>
      </desc>
    </func>

    <func>
      <name name="apply" arity="2"/>
      <fsummary>Apply a function to an argument list.</fsummary>
      <desc>
        <p>Calls a fun, passing the elements in <c><anno>Args</anno></c>
          as arguments.</p>
        <p>If the number of elements in the arguments are known at
          compile time, the call is better written as
          <c><anno>Fun</anno>(Arg1, Arg2, ... ArgN)</c>.</p>
        <warning>
          <p>Earlier, <c><anno>Fun</anno></c> could also be specified as
            <c>{Module, Function}</c>, equivalent to
            <c>apply(Module, Function, Args)</c>. <em>This use is
            deprecated and will stop working in a future release.</em></p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="apply" arity="3"/>
      <fsummary>Apply a function to an argument list.</fsummary>
      <desc>
        <p>Returns the result of applying <c>Function</c> in
          <c><anno>Module</anno></c> to <c><anno>Args</anno></c>.
          The applied function must
          be exported from <c>Module</c>. The arity of the function is
          the length of <c>Args</c>. Example:</p>
        <pre>
> <input>apply(lists, reverse, [[a, b, c]]).</input>
[c,b,a]
> <input>apply(erlang, atom_to_list, ['Erlang']).</input>
"Erlang"</pre>
        <p>If the number of arguments are known at compile time,
          the call is better written as
          <c><anno>Module</anno>:<anno>Function</anno>(Arg1, Arg2, ...,
          ArgN)</c>.</p>
        <p>Failure: <seealso marker="kernel:error_handler#undefined_function/3">
          <c>error_handler:undefined_function/3</c></seealso> is called
          if the applied function is not exported. The error handler
          can be redefined (see
          <seealso marker="#process_flag/2"><c>process_flag/2</c></seealso>).
          If <c>error_handler</c> is undefined, or if the user has
          redefined the default <c>error_handler</c> so the replacement
          module is undefined, an error with reason <c>undef</c>
          is generated.</p>
      </desc>
    </func>

    <func>
      <name name="atom_to_binary" arity="2"/>
      <fsummary>Return the binary representation of an atom.</fsummary>
      <desc>
        <p>Returns a binary corresponding to the text
          representation of <c><anno>Atom</anno></c>.
          If <c><anno>Encoding</anno></c>
          is <c>latin1</c>, one byte exists for each character
          in the text representation. If <c><anno>Encoding</anno></c> is
          <c>utf8</c> or
          <c>unicode</c>, the characters are encoded using UTF-8 where
          characters may require multiple bytes.</p>
        <note>
          <p>As from Erlang/OTP 20, atoms can contain any Unicode character
            and <c>atom_to_binary(<anno>Atom</anno>, latin1)</c> may fail if the
            text representation for <c><anno>Atom</anno></c> contains a Unicode
            character &gt; 255.</p>
        </note>
        <p>Example:</p>
        <pre>
> <input>atom_to_binary('Erlang', latin1).</input>
&lt;&lt;"Erlang"&gt;&gt;</pre>
      </desc>
    </func>

    <func>
      <name name="atom_to_list" arity="1"/>
      <fsummary>Text representation of an atom.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of <c><anno>Atom</anno></c>, for example:</p>
        <pre>
> <input>atom_to_list('Erlang').</input>
"Erlang"</pre>
      </desc>
    </func>

    <func>
      <name name="binary_part" arity="2"/>
      <fsummary>Extract a part of a binary.</fsummary>
      <desc>
      <p>Extracts the part of the binary described by
        <c><anno>PosLen</anno></c>.</p>
      <p>Negative length can be used to extract bytes at the end
        of a binary, for example:</p>
<code>
1> Bin = &lt;&lt;1,2,3,4,5,6,7,8,9,10&gt;&gt;.
2> binary_part(Bin,{byte_size(Bin), -5}).
&lt;&lt;6,7,8,9,10&gt;&gt;</code>
      <p>Failure: <c>badarg</c> if <c><anno>PosLen</anno></c> in any way
        references outside the binary.</p>
      <p><c><anno>Start</anno></c> is zero-based, that is:</p>
<code>
1> Bin = &lt;&lt;1,2,3&gt;&gt;
2> binary_part(Bin,{0,2}).
&lt;&lt;1,2&gt;&gt;</code>
      <p>For details about the <c><anno>PosLen</anno></c> semantics, see
        <seealso marker="stdlib:binary"><c>binary(3)</c></seealso>.</p>
      <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="binary_part" arity="3"/>
      <fsummary>Extract a part of a binary.</fsummary>
      <desc>
      <p>The same as <c>binary_part(<anno>Subject</anno>,
        {<anno>Start</anno>, <anno>Length</anno>})</c>.</p>
      <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="binary_to_atom" arity="2"/>
      <fsummary>Convert from text representation to an atom.</fsummary>
      <desc>
        <p>Returns the atom whose text representation is
          <c><anno>Binary</anno></c>.
          If <c><anno>Encoding</anno></c> is <c>latin1</c>, no
          translation of bytes in the binary is done.
          If <c><anno>Encoding</anno></c>
          is <c>utf8</c> or <c>unicode</c>, the binary must contain
          valid UTF-8 sequences.</p>
        <note>
          <p>As from Erlang/OTP 20, <c>binary_to_atom(<anno>Binary</anno>, utf8)</c>
            is capable of encoding any Unicode character. Earlier versions would
            fail if the binary contained Unicode characters &gt; 255.
            For more information about Unicode support in atoms, see the
            <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8
            encoded atoms</seealso>
            in section "External Term Format" in the User's Guide.</p>
        </note>
        <p>Examples:</p>
        <pre>
> <input>binary_to_atom(&lt;&lt;"Erlang"&gt;&gt;, latin1).</input>
'Erlang'
> <input>binary_to_atom(&lt;&lt;1024/utf8&gt;&gt;, utf8).</input>
'Ѐ'</pre>
      </desc>
    </func>

    <func>
      <name name="binary_to_existing_atom" arity="2"/>
      <fsummary>Convert from text representation to an atom.</fsummary>
      <desc>
        <p>As
          <seealso marker="#binary_to_atom/2"><c>binary_to_atom/2</c></seealso>,
          but the atom must exist.</p>
        <p>Failure: <c>badarg</c> if the atom does not exist.</p>
	<note>
	  <p>Note that the compiler may optimize away atoms. For
	  example, the compiler will rewrite
	  <c>atom_to_list(some_atom)</c> to <c>"some_atom"</c>. If
	  that expression is the only mention of the atom
	  <c>some_atom</c> in the containing module, the atom will not
	  be created when the module is loaded, and a subsequent call
	  to <c>binary_to_existing_atom(&lt;&lt;"some_atom"&gt;&gt;, utf8)</c>
	  will fail.</p>
	</note>
      </desc>
    </func>

    <func>
      <name name="binary_to_float" arity="1"/>
      <fsummary>Convert from text representation to a float.</fsummary>
      <desc>
        <p>Returns the float whose text representation is
          <c><anno>Binary</anno></c>, for example:</p>
        <pre>
> <input>binary_to_float(&lt;&lt;"2.2017764e+0">>).</input>
2.2017764</pre>
        <p>Failure: <c>badarg</c> if <c><anno>Binary</anno></c> contains a bad
          representation of a float.</p>
      </desc>
    </func>

    <func>
      <name name="binary_to_integer" arity="1"/>
      <fsummary>Convert from text representation to an integer.</fsummary>
      <desc>
        <p>Returns an integer whose text representation is
          <c><anno>Binary</anno></c>, for example:</p>
        <pre>
> <input>binary_to_integer(&lt;&lt;"123"&gt;&gt;).</input>
123</pre>
        <p>Failure: <c>badarg</c> if <c><anno>Binary</anno></c> contains a bad
          representation of an integer.</p>
      </desc>
    </func>

    <func>
      <name name="binary_to_integer" arity="2"/>
      <fsummary>Convert from text representation to an integer.</fsummary>
      <desc>
        <p>Returns an integer whose text representation in base
          <c><anno>Base</anno></c> is <c><anno>Binary</anno></c>, for
          example:</p>
        <pre>
> <input>binary_to_integer(&lt;&lt;"3FF"&gt;&gt;, 16).</input>
1023</pre>
        <p>Failure: <c>badarg</c> if <c><anno>Binary</anno></c> contains a bad
          representation of an integer.</p>
      </desc>
    </func>

    <func>
      <name name="binary_to_list" arity="1"/>
      <fsummary>Convert a binary to a list.</fsummary>
      <desc>
        <p>Returns a list of integers corresponding to the bytes of
          <c><anno>Binary</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="binary_to_list" arity="3"/>
      <fsummary>Convert part of a binary to a list.</fsummary>
      <type_desc variable="Start">1..byte_size(<c><anno>Binary</anno></c>)
      </type_desc>
      <desc>
        <p>As <c>binary_to_list/1</c>, but returns a list of integers
          corresponding to the bytes from position <c><anno>Start</anno></c> to
          position <c><anno>Stop</anno></c> in <c><anno>Binary</anno></c>.
          The positions in the
          binary are numbered starting from 1.</p>
        <note>
          <p><em>The one-based indexing for binaries used by
            this function is deprecated.</em> New code is to use
            <seealso marker="stdlib:binary#bin_to_list/3">
            <c>binary:bin_to_list/3</c></seealso>
            in STDLIB instead. All functions in module
            <c>binary</c> consistently use zero-based indexing.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="binary_to_term" arity="1"/>
      <fsummary>Decode an Erlang external term format binary.</fsummary>
      <desc>
        <p>Returns an Erlang term that is the result of decoding
          binary object <c><anno>Binary</anno></c>, which must be encoded
          according to the <seealso marker="erts:erl_ext_dist">
          Erlang external term format</seealso>.</p>
        <pre>
> <input>Bin = term_to_binary(hello).</input>
&lt;&lt;131,100,0,5,104,101,108,108,111>>
> <input>hello = binary_to_term(Bin).</input>
hello
</pre>
        <warning>
          <p>When decoding binaries from untrusted sources,
            consider using <c>binary_to_term/2</c> to prevent Denial
            of Service attacks.</p>
        </warning>
        <p>See also
          <seealso marker="#term_to_binary/1"><c>term_to_binary/1</c></seealso>
          and <seealso marker="#binary_to_term/2">
          <c>binary_to_term/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="binary_to_term" arity="2"/>
      <fsummary>Decode an Erlang external term format binary.</fsummary>
      <desc>
        <p>As <c>binary_to_term/1</c>, but takes these options:</p>
        <taglist>
          <tag><c>safe</c></tag>
          <item>
            <p>Use this option when receiving binaries from an untrusted
              source.</p>
            <p>When enabled, it prevents decoding data that can be used to
              attack the Erlang system. In the event of receiving unsafe
              data, decoding fails with a <c>badarg</c> error.</p>
            <p>This prevents creation of new atoms directly,
              creation of new atoms indirectly (as they are embedded in
              certain structures, such as process identifiers,
              refs, and funs), and
              creation of new external function references.
              None of those resources are garbage collected, so unchecked
              creation of them can exhaust available memory.</p>
        <pre>
> <input>binary_to_term(&lt;&lt;131,100,0,5,"hello">>, [safe]).</input>
** exception error: bad argument
> <input>hello.</input>
hello
> <input>binary_to_term(&lt;&lt;131,100,0,5,"hello">>, [safe]).</input>
hello
</pre>
          </item>
          <tag><c>used</c></tag>
          <item>
	    <p>Changes the return value to <c>{Term, Used}</c> where <c>Used</c>
	    is the number of bytes actually read from <c>Binary</c>.</p>
        <pre>
> <input>Input = &lt;&lt;131,100,0,5,"hello","world">>.</input>
&lt;&lt;131,100,0,5,104,101,108,108,111,119,111,114,108,100>>
> <input>{Term, Used} = binary_to_term(Input, [used]).</input>
{hello, 9}
> <input>split_binary(Input, Used).</input>
{&lt;&lt;131,100,0,5,104,101,108,108,111>>, &lt;&lt;"world">>}
</pre>
          </item>
        </taglist>
        <p>Failure: <c>badarg</c> if <c>safe</c> is specified and unsafe
          data is decoded.</p>
        <p>See also
          <seealso marker="#term_to_binary/1"><c>term_to_binary/1</c></seealso>,
          <seealso marker="#binary_to_term/1">
          <c>binary_to_term/1</c></seealso>, and
          <seealso marker="#list_to_existing_atom/1">
          <c>list_to_existing_atom/1</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="bit_size" arity="1"/>
      <fsummary>Return the size of a bitstring.</fsummary>
      <desc>
        <p>Returns an integer that is the size in bits of
          <c><anno>Bitstring</anno></c>, for example:</p>
        <pre>
> <input>bit_size(&lt;&lt;433:16,3:3&gt;&gt;).</input>
19
> <input>bit_size(&lt;&lt;1,2,3&gt;&gt;).</input>
24</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="bitstring_to_list" arity="1"/>
      <fsummary>Convert a bitstring to a list.</fsummary>
      <desc>
        <p>Returns a list of integers corresponding to the bytes of
          <c><anno>Bitstring</anno></c>. If the number of bits in the binary
          is not divisible by 8, the last element of the list is a bitstring
          containing the remaining 1-7 bits.</p>
      </desc>
    </func>

    <func>
      <name name="bump_reductions" arity="1"/>
      <fsummary>Increment the reduction counter.</fsummary>
      <desc>
        <p>This implementation-dependent function increments
          the reduction counter for the calling process. In the Beam
          emulator, the reduction counter is normally incremented by
          one for each function and BIF call. A context switch is
          forced when the counter reaches the maximum number of
          reductions for a process (2000 reductions in Erlang/OTP R12B).</p>
        <warning>
          <p>This BIF can be removed in a future version of the Beam
            machine without prior warning. It is unlikely to be
            implemented in other Erlang implementations.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="byte_size" arity="1"/>
      <fsummary>Return the size of a bitstring (or binary).</fsummary>
      <desc>
        <p>Returns an integer that is the number of bytes needed to
          contain <c><anno>Bitstring</anno></c>. That is, if the number of bits
          in <c><anno>Bitstring</anno></c> is not divisible by 8, the resulting
          number of bytes is rounded <em>up</em>. Examples:</p>
        <pre>
> <input>byte_size(&lt;&lt;433:16,3:3&gt;&gt;).</input>
3
> <input>byte_size(&lt;&lt;1,2,3&gt;&gt;).</input>
3</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="cancel_timer" arity="1"/>
      <fsummary>Cancel a timer.</fsummary>
      <desc>
        <p>Cancels a timer. The same as calling
          <seealso marker="#cancel_timer/2">
          <c>erlang:cancel_timer(TimerRef, [])</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="cancel_timer" arity="2"/>
      <fsummary>Cancel a timer.</fsummary>
      <desc>
        <p>Cancels a timer that has been created by
          <seealso marker="#start_timer/4">
          <c>erlang:start_timer</c></seealso> or
          <seealso marker="#send_after/4"><c>erlang:send_after</c></seealso>.
          <c><anno>TimerRef</anno></c> identifies the timer, and
          was returned by the BIF that created the timer.</p>
        <p><c><anno>Option</anno></c>s:</p>
        <taglist>
          <tag><c>{async, Async}</c></tag>
          <item>
            <p>Asynchronous request for cancellation. <c>Async</c>
              defaults to <c>false</c>, which causes the
              cancellation to be performed synchronously. When
              <c>Async</c> is set to <c>true</c>, the cancel
              operation is performed asynchronously. That is,
              <c>cancel_timer()</c> sends an asynchronous
              request for cancellation to the timer service that
              manages the timer, and then returns <c>ok</c>.</p>
          </item>
          <tag><c>{info, Info}</c></tag>
          <item>
            <p>Requests information about the <c><anno>Result</anno></c>
              of the cancellation. <c>Info</c> defaults to <c>true</c>,
              which means the <c><anno>Result</anno></c> is
              given. When <c>Info</c> is set to <c>false</c>, no
              information about the result of the cancellation
              is given.</p>
            <list type="bulleted">
              <item>
                <p>When <c>Async</c> is <c>false</c>:
                  if <c>Info</c> is <c>true</c>, the <c>Result</c> is
                  returned by <c>erlang:cancel_timer()</c>. otherwise
                  <c>ok</c> is returned.</p>
              </item>
              <item>
                <p>When <c>Async</c> is <c>true</c>:
                  if <c>Info</c> is <c>true</c>, a message on the form
                  <c>{cancel_timer, <anno>TimerRef</anno>,
                  <anno>Result</anno>}</c> is sent to the
                  caller of <c>erlang:cancel_timer()</c> when the
                  cancellation operation has been performed, otherwise
                  no message is sent.</p>
              </item>
            </list>
           </item>
         </taglist>
        <p>More <c><anno>Option</anno></c>s may be added in the future.</p>
        <p>If <c><anno>Result</anno></c> is an integer, it represents
          the time in milliseconds left until the canceled timer would
          have expired.</p>
        <p>If <c><anno>Result</anno></c> is <c>false</c>, a
          timer corresponding to <c><anno>TimerRef</anno></c> could not
          be found. This can be either because the timer had expired,
          already had been canceled, or because <c><anno>TimerRef</anno></c>
          never corresponded to a timer. Even if the timer had expired,
          it does not tell you if the time-out message has
          arrived at its destination yet.</p>
        <note>
          <p>The timer service that manages the timer can be co-located
            with another scheduler than the scheduler that the calling
            process is executing on. If so, communication
            with the timer service takes much longer time than if it
            is located locally. If the calling process is in critical
            path, and can do other things while waiting for the result
            of this operation, or is not interested in the result of
            the operation, you want to use option <c>{async, true}</c>.
            If using option <c>{async, false}</c>, the calling
            process blocks until the operation has been performed.</p>
        </note>
        <p>See also
          <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>,
          <seealso marker="#start_timer/4">
          <c>erlang:start_timer/4</c></seealso>, and
          <seealso marker="#read_timer/2">
          <c>erlang:read_timer/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="ceil" arity="1"/>
      <fsummary>Returns the smallest integer not less than the argument</fsummary>
      <desc>
        <p>Returns the smallest integer not less than
	<c><anno>Number</anno></c>.
        For example:</p>
        <pre>
> <input>ceil(5.5).</input>
6</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>
    <func>
      <name name="check_old_code" arity="1"/>
      <fsummary>Check if a module has old code.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Module</anno></c> has old code,
          otherwise <c>false</c>.</p>
        <p>See also <seealso marker="kernel:code">
          <c>code(3)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="check_process_code" arity="2"/>
      <fsummary>Check if a process executes old code for a module.</fsummary>
      <desc>
        <p>The same as
          <seealso marker="#check_process_code/3">
          <c>check_process_code(<anno>Pid</anno>, <anno>Module</anno>, [])</c>
          </seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="check_process_code" arity="3"/>
      <fsummary>Check if a process executes old code for a module.</fsummary>
      <desc>
        <p>Checks if the node local process identified by
          <c><anno>Pid</anno></c>
          executes old code for <c><anno>Module</anno></c>.</p>
        <p><c><anno>Option</anno></c>s:</p>
        <taglist>
          <tag><c>{allow_gc, boolean()}</c></tag>
          <item>
            <p>Determines if garbage collection is allowed when performing
            the operation. If <c>{allow_gc, false}</c> is passed, and
            a garbage collection is needed to determine the
            result of the operation, the operation is aborted (see
            information on <c><anno>CheckResult</anno></c> below).
            The default is to allow garbage collection, that is,
            <c>{allow_gc, true}</c>.</p>
          </item>
          <tag><c>{async, RequestId}</c></tag>
          <item>
            <p>The function <c>check_process_code/3</c> returns
            the value <c>async</c> immediately after the request
            has been sent. When the request has been processed, the
            process that called this function is passed a
            message on the form <c>{check_process_code, <anno>RequestId</anno>,
            <anno>CheckResult</anno>}</c>.</p>
          </item>
        </taglist>
        <p>If <c><anno>Pid</anno></c> equals <c>self()</c>, and
          no <c>async</c> option has been passed, the operation
          is performed at once. Otherwise a request for
          the operation is sent to the process identified by
          <c><anno>Pid</anno></c>, and is handled when
          appropriate. If no <c>async</c> option has been passed,
          the caller blocks until <c><anno>CheckResult</anno></c>
          is available and can be returned.</p>
        <p><c><anno>CheckResult</anno></c> informs about the result of
          the request as follows:</p>
        <taglist>
          <tag><c>true</c></tag>
          <item>
            <p>The process identified by <c><anno>Pid</anno></c>
            executes old code for <c><anno>Module</anno></c>.
            That is, the current call of the process executes old
            code for this module, or the process has references
            to old code for this module, or the process contains
            funs that references old code for this module.</p>
          </item>
          <tag><c>false</c></tag>
          <item>
            <p>The process identified by <c><anno>Pid</anno></c> does
            not execute old code for <c><anno>Module</anno></c>.</p>
          </item>
          <tag><c>aborted</c></tag>
          <item>
            <p>The operation was aborted, as the process needed to
            be garbage collected to determine the operation result,
            and the operation was requested
            by passing option <c>{allow_gc, false}</c>.</p>
          </item>
        </taglist>
	<note>
	<p>
	  Up until ERTS version 8.*, the check process code operation
	  checks for all types of references to the old code. That is,
	  direct references (e.g. return addresses on the process
	  stack), indirect references (<c>fun</c>s in process
	  context), and references to literals in the code.
	</p>
	<p>
	  As of ERTS version 9.0, the check process code operation
	  only checks for direct references to the code. Indirect
	  references via <c>fun</c>s will be ignored. If such
	  <c>fun</c>s exist and are used after a purge of the old
	  code, an exception will be raised upon usage (same as
	  the case when the <c>fun</c> is received by the process
	  after the purge). Literals will be taken care of (copied)
	  at a  later stage. This behavior can as of ERTS version
	  8.1 be enabled when
	  <seealso marker="doc/installation_guide:INSTALL#Advanced-configuration-and-build-of-ErlangOTP_Configuring">building OTP</seealso>,
	  and will automatically be enabled if dirty scheduler
	  support is enabled.
	</p>
	</note>
        <p>See also <seealso marker="kernel:code">
          <c>code(3)</c></seealso>.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>Pid</anno></c> is not a node local process
            identifier.
          </item>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>Module</anno></c> is not an atom.
          </item>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>OptionList</anno></c> is an invalid list of options.
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="convert_time_unit" arity="3"/>
      <fsummary>Convert time unit of a time value.</fsummary>
      <desc>
        <p>Converts the <c><anno>Time</anno></c> value of time unit
          <c><anno>FromUnit</anno></c> to the corresponding
          <c><anno>ConvertedTime</anno></c> value of time unit
          <c><anno>ToUnit</anno></c>. The result is rounded
          using the floor function.</p>
        <warning>
          <p>You can lose accuracy and precision when converting
            between time units. To minimize such loss, collect all
            data at <c>native</c> time unit and do the conversion on the end
            result.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="crc32" arity="1"/>
      <fsummary>Compute crc32 (IEEE 802.3) checksum.</fsummary>
      <desc>
        <p>Computes and returns the crc32 (IEEE 802.3 style) checksum
          for <c><anno>Data</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="crc32" arity="2"/>
      <fsummary>Compute crc32 (IEEE 802.3) checksum.</fsummary>
      <desc>
        <p>Continues computing the crc32 checksum by combining
          the previous checksum, <c><anno>OldCrc</anno></c>, with the checksum
          of <c><anno>Data</anno></c>.</p>
        <p>The following code:</p>
        <code>
X = erlang:crc32(Data1),
Y = erlang:crc32(X,Data2).</code>
        <p>assigns the same value to <c>Y</c> as this:</p>
        <code>
Y = erlang:crc32([Data1,Data2]).</code>
      </desc>
    </func>

    <func>
      <name name="crc32_combine" arity="3"/>
      <fsummary>Combine two crc32 (IEEE 802.3) checksums.</fsummary>
      <desc>
        <p>Combines two previously computed crc32 checksums.
          This computation requires the size of the data object for
          the second checksum to be known.</p>
        <p>The following code:</p>
        <code>
Y = erlang:crc32(Data1),
Z = erlang:crc32(Y,Data2).</code>
        <p>assigns the same value to <c>Z</c> as this:</p>
	<code>
X = erlang:crc32(Data1),
Y = erlang:crc32(Data2),
Z = erlang:crc32_combine(X,Y,iolist_size(Data2)).</code>
      </desc>
    </func>

    <func>
      <name name="date" arity="0"/>
      <fsummary>Current date.</fsummary>
      <desc>
        <p>Returns the current date as <c>{Year, Month, Day}</c>.</p>
        <p>The time zone and Daylight Saving Time correction depend on
          the underlying OS. Example:</p>
        <pre>
> <input>date().</input>
{1995,2,19}</pre>
      </desc>
    </func>

    <func>
      <name name="decode_packet" arity="3"/>
      <fsummary>Extract a protocol packet from a binary.</fsummary>
      <desc>
        <p>Decodes the binary <c><anno>Bin</anno></c> according to the packet
          protocol specified by <c><anno>Type</anno></c>. Similar to the packet
          handling done by sockets with option
          <c>{packet,<anno>Type</anno>}.</c></p>
        <p>If an entire packet is contained in <c><anno>Bin</anno></c>, it is
          returned together with the remainder of the binary as
          <c>{ok,<anno>Packet</anno>,<anno>Rest</anno>}</c>.</p>
        <p>If <c><anno>Bin</anno></c> does not contain the entire packet,
          <c>{more,<anno>Length</anno>}</c> is returned.
          <c><anno>Length</anno></c> is either the
          expected <em>total size</em> of the packet, or <c>undefined</c>
          if the expected packet size is unknown. <c>decode_packet</c>
          can then be called again with more data added.</p>
        <p>If the packet does not conform to the protocol format,
          <c>{error,<anno>Reason</anno>}</c> is returned.</p>
        <p><c>Type</c>s:</p>
        <taglist>
          <tag><c>raw | 0</c></tag>
          <item>
            <p>No packet handling is done. The entire binary is
              returned unless it is empty.</p>
          </item>
          <tag><c>1 | 2 | 4</c></tag>
          <item>
            <p>Packets consist of a header specifying the number of
              bytes in the packet, followed by that number of bytes.
              The length of the header can be one, two, or four bytes;
              the order of the bytes is big-endian. The header
              is stripped off when the packet is returned.</p>
          </item>
          <tag><c>line</c></tag>
          <item>
            <p>A packet is a line-terminated by a delimiter byte,
              default is the latin-1 newline character. The delimiter
              byte is included in the returned packet unless the line
              was truncated according to option <c>line_length</c>.</p>
          </item>
          <tag><c>asn1 | cdr | sunrm | fcgi | tpkt</c></tag>
          <item>
            <p>The header is <em>not</em> stripped off.</p>
            <p>The meanings of the packet types are as follows:</p>
            <taglist>     
              <tag><c>asn1</c> - ASN.1 BER</tag><item></item>
              <tag><c>sunrm</c> - Sun's RPC encoding</tag><item></item>
              <tag><c>cdr</c> - CORBA (GIOP 1.1)</tag><item></item>
              <tag><c>fcgi</c> - Fast CGI</tag><item></item>
              <tag><c>tpkt</c> - TPKT format [RFC1006]</tag><item></item>
            </taglist>
          </item>
          <tag><c>http | httph | http_bin | httph_bin</c></tag>
          <item>
            <p>The Hypertext Transfer Protocol. The packets
              are returned with the format according to
              <c><anno>HttpPacket</anno></c> described earlier.
              A packet is either a
              request, a response, a header, or an end of header
              mark. Invalid lines are returned as
              <c><anno>HttpError</anno></c>.</p>
            <p>Recognized request methods and header fields are returned
              as atoms. Others are returned as strings. Strings of
              unrecognized header fields are formatted with only
              capital letters first and after hyphen characters, for
              example, <c>"Sec-Websocket-Key"</c>.</p>
            <p>The protocol type <c>http</c> is only to be used for
              the first line when an <c><anno>HttpRequest</anno></c> or an
              <c><anno>HttpResponse</anno></c> is expected.
              The following calls are to use <c>httph</c> to get
              <c><anno>HttpHeader</anno></c>s until
              <c>http_eoh</c> is returned, which marks the end of the
              headers and the beginning of any following message body.</p> 
            <p>The variants <c>http_bin</c> and <c>httph_bin</c> return
              strings (<c>HttpString</c>) as binaries instead of lists.</p>
          </item>
        </taglist>
        <p>Options:</p>
        <taglist>
          <tag><c>{packet_size, integer() >= 0}</c></tag>
          <item><p>Sets the maximum allowed size of the packet body.
            If the packet header indicates that the length of the
            packet is longer than the maximum allowed length, the
            packet is considered invalid. Defaults to 0, which means
            no size limit.</p>
          </item>
          <tag><c>{line_length, integer() >= 0}</c></tag>
          <item>
            <p>For packet type <c>line</c>, lines longer than
              the indicated length are truncated.</p>
            <p>Option <c>line_length</c> also applies to <c>http*</c>
              packet types as an alias for option <c>packet_size</c>
              if <c>packet_size</c> itself is not set. This use is
              only intended for backward compatibility.</p>
          </item>
          <tag><c>{line_delimiter, 0 =&lt; byte() =&lt; 255}</c></tag>
          <item><p>For packet type <c>line</c>, sets the delimiting byte.
            Default is the latin-1 character <c>$\n</c>.</p>
          </item>
        </taglist>
        <p>Examples:</p>
        <pre>
> <input>erlang:decode_packet(1,&lt;&lt;3,"abcd"&gt;&gt;,[]).</input>
{ok,&lt;&lt;"abc"&gt;&gt;,&lt;&lt;"d"&gt;&gt;}
> <input>erlang:decode_packet(1,&lt;&lt;5,"abcd"&gt;&gt;,[]).</input>
{more,6}</pre>
      </desc>
    </func>

    <func>
      <name name="delete_element" arity="2"/>
      <fsummary>Delete element at index in a tuple.</fsummary>
      <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno>)</type_desc>
      <desc>
        <p>Returns a new tuple with element at <c><anno>Index</anno></c>
          removed from tuple <c><anno>Tuple1</anno></c>, for example:</p>
        <pre>
> <input>erlang:delete_element(2, {one, two, three}).</input>
{one,three}</pre>
      </desc>
    </func>

    <func>
      <name name="delete_module" arity="1"/>
      <fsummary>Make the current code for a module old.</fsummary>
      <desc>
        <p>Makes the current code for <c><anno>Module</anno></c> become old
          code and deletes all references for this module from the export table.
          Returns <c>undefined</c> if the module does not exist,
          otherwise <c>true</c>.</p>
        <warning>
          <p>This BIF is intended for the code server (see
            <seealso marker="kernel:code"><c>code(3)</c></seealso>)
            and is not to be used elsewhere.</p>
        </warning>
        <p>Failure: <c>badarg</c> if there already is an old version of
          <c>Module</c>.</p>
      </desc>
    </func>

    <func>
      <name name="demonitor" arity="1"/>
      <fsummary>Stop monitoring.</fsummary>
      <desc>
        <p>If <c><anno>MonitorRef</anno></c> is a reference that the
          calling process obtained by calling
          <seealso marker="#monitor/2"><c>monitor/2</c></seealso>,
          this monitoring is turned off. If the monitoring is already
          turned off, nothing happens.</p>
        <p>Once <c>demonitor(<anno>MonitorRef</anno>)</c> has returned, it is
          guaranteed that no <c>{'DOWN',
          <anno>MonitorRef</anno>, _, _, _}</c> message,
          because of the monitor, will be placed in the caller message queue
          in the future. However, a <c>{'DOWN',
          <anno>MonitorRef</anno>, _, _, _}</c> message
          can have been placed in the caller message queue before
          the call. It is therefore usually advisable
          to remove such a <c>'DOWN'</c> message from the message queue
          after monitoring has been stopped.
          <seealso marker="#demonitor/2">
          <c>demonitor(<anno>MonitorRef</anno>, [flush])</c></seealso>
          can be used instead of <c>demonitor(<anno>MonitorRef</anno>)</c>
          if this cleanup is wanted.</p>
        <note>
          <p>Before Erlang/OTP R11B (ERTS 5.5) <c>demonitor/1</c>
            behaved completely asynchronously, that is, the monitor was active
            until the "demonitor signal" reached the monitored entity. This
            had one undesirable effect. You could never know when
            you were guaranteed <em>not</em> to receive a <c>DOWN</c> message
            because of the monitor.</p>
          <p>The current behavior can be viewed as two combined operations:
            asynchronously send a "demonitor signal" to the monitored entity
            and ignore any future results of the monitor.</p>
        </note>
        <p>Failure: It is an error if <c><anno>MonitorRef</anno></c> refers to a
          monitoring started by another process. Not all such cases are
          cheap to check. If checking is cheap, the call fails with
          <c>badarg</c>, for example if <c><anno>MonitorRef</anno></c> is a
          remote reference.</p>
      </desc>
    </func>

    <func>
      <name name="demonitor" arity="2"/>
      <fsummary>Stop monitoring.</fsummary>
      <desc>
        <p>The returned value is <c>true</c> unless <c>info</c> is part
          of <c><anno>OptionList</anno></c>.</p>
        <p><c>demonitor(<anno>MonitorRef</anno>, [])</c> is equivalent to
          <seealso marker="#demonitor/1">
          <c>demonitor(<anno>MonitorRef</anno>)</c></seealso>.</p>
        <p><c><anno>Option</anno></c>s:</p>
        <taglist>
          <tag><c>flush</c></tag>
          <item>
            <p>Removes (one) <c>{_,
              <anno>MonitorRef</anno>, _, _, _}</c> message,
              if there is one, from the caller message queue after
              monitoring has been stopped.</p>
            <p>Calling <c>demonitor(<anno>MonitorRef</anno>, [flush])</c>
              is equivalent to the following, but more efficient:</p>
            <code type="none">
demonitor(MonitorRef),
receive
    {_, MonitorRef, _, _, _} ->
        true
after 0 ->
        true
end</code>
          </item>
          <tag><c>info</c></tag>
          <item>
            <p>The returned value is one of the following:</p>
            <taglist>
              <tag><c>true</c></tag>
              <item><p>The monitor was found and removed. In this case,
                no <c>'DOWN'</c> message corresponding to this
                monitor has been delivered and will not be delivered.</p>
              </item>
              <tag><c>false</c></tag>
              <item><p>The monitor was not found and could not be removed.
                This probably because someone already has placed a
                <c>'DOWN'</c> message corresponding to this monitor
                in the caller message queue.</p>
              </item>
            </taglist>
            <p>If option <c>info</c> is combined with option <c>flush</c>,
              <c>false</c> is returned if a flush was needed,
              otherwise <c>true</c>.</p>
          </item>
        </taglist>
        <note>
          <p>More options can be added in a future release.</p>
        </note>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>OptionList</anno></c> is not a list.
          </item>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>Option</anno></c> is an invalid option.
          </item>
          <tag><c>badarg</c></tag>
          <item>The same failure as for
            <seealso marker="#demonitor/1"><c>demonitor/1</c></seealso>.
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="disconnect_node" arity="1"/>
      <fsummary>Force the disconnection of a node.</fsummary>
      <desc>
        <p>Forces the disconnection of a node. This appears to
          the node <c><anno>Node</anno></c> as if the local node has crashed.
          This BIF is mainly used in the Erlang network authentication
          protocols.</p>
        <p>Returns <c>true</c> if disconnection succeeds,
          otherwise <c>false</c>. If the local node is not alive,
          <c>ignored</c> is returned.</p>
      </desc>
    </func>

    <func>
      <name name="display" arity="1"/>
      <fsummary>Print a term on standard output.</fsummary>
      <desc>
        <p>Prints a text representation of <c><anno>Term</anno></c> on the
          standard output.</p>
        <warning>
          <p>This BIF is intended for debugging only.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="dist_ctrl_get_data" arity="1"/>
      <fsummary>Get distribution channel data to pass to another node.</fsummary>
      <desc>
        <p>
	  Get distribution channel data from the local node that is
	  to be passed to the remote node. The distribution channel
	  is identified by <c><anno>DHandle</anno></c>. If no data
	  is available, the atom <c>none</c> is returned. One
	  can request to be informed by a message when more
	  data is available by calling
	  <seealso marker="erlang#dist_ctrl_get_data_notification/1"><c>erlang:dist_ctrl_get_data_notification(DHandle)</c></seealso>.
	</p>
	<note><p>
	  Only the process registered as distribution
	  controller for the distribution channel identified by
	  <c><anno>DHandle</anno></c> is allowed to call this
	  function.
	</p></note>
	<p>
	  This function is used when implementing an alternative
	  distribution carrier using processes as distribution
	  controllers. <c><anno>DHandle</anno></c> is retrived
	  via the callback
	  <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
	  More information can be found in the documentation of
	  <seealso marker="erts:alt_dist#distribution_module">ERTS
	  User's Guide ➜ How to implement an Alternative Carrier
	  for the Erlang Distribution ➜ Distribution Module</seealso>.
	</p>
      </desc>
    </func>

    <func>
      <name name="dist_ctrl_get_data_notification" arity="1"/>
      <fsummary>Request notification about available outgoing distribution channel data.</fsummary>
      <desc>
        <p>
	  Request notification when more data is available to
	  fetch using
	  <seealso marker="erlang#dist_ctrl_get_data/1"><c>erlang:dist_ctrl_get_data(DHandle)</c></seealso>
	  for the distribution channel identified by
	  <c><anno>DHandle</anno></c>. When more data is present,
	  the caller will be sent the message <c>dist_data</c>.
	  Once a <c>dist_data</c> messages has been sent, no
	  more <c>dist_data</c> messages will be sent until
	  the <c>dist_ctrl_get_data_notification/1</c> function has been called
	  again.
	</p>
	<note><p>
	  Only the process registered as distribution
	  controller for the distribution channel identified by
	  <c><anno>DHandle</anno></c> is allowed to call this
	  function.
	</p></note>
	<p>
	  This function is used when implementing an alternative
	  distribution carrier using processes as distribution
	  controllers. <c><anno>DHandle</anno></c> is retrived
	  via the callback
	  <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
	  More information can be found in the documentation of
	  <seealso marker="erts:alt_dist#distribution_module">ERTS
	  User's Guide ➜ How to implement an Alternative Carrier
	  for the Erlang Distribution ➜ Distribution Module</seealso>.
	</p>
      </desc>
    </func>

    <func>
      <name name="dist_ctrl_input_handler" arity="2"/>
      <fsummary>Register distribution channel input handler process.</fsummary>
      <desc>
        <p>
	  Register an alternate input handler process for the
	  distribution channel identified by <c><anno>DHandle</anno></c>.
	  Once this function has been called, <c><anno>InputHandler</anno></c>
	  is the only process allowed to call
	  <seealso marker="erlang#dist_ctrl_put_data/2"><c>erlang:dist_ctrl_put_data(DHandle, Data)</c></seealso>
	  with the <c><anno>DHandle</anno></c> identifing this distribution
	  channel.
	</p>
	<note><p>
	  Only the process registered as distribution
	  controller for the distribution channel identified by
	  <c><anno>DHandle</anno></c> is allowed to call this
	  function.
	</p></note>
	<p>
	  This function is used when implementing an alternative
	  distribution carrier using processes as distribution
	  controllers. <c><anno>DHandle</anno></c> is retrived
	  via the callback
	  <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
	  More information can be found in the documentation of
	  <seealso marker="erts:alt_dist#distribution_module">ERTS
	  User's Guide ➜ How to implement an Alternative Carrier
	  for the Erlang Distribution ➜ Distribution Module</seealso>.
	</p>
      </desc>
    </func>

    <func>
      <name name="dist_ctrl_put_data" arity="2"/>
      <fsummary>Pass data into the VM from a distribution channel.</fsummary>
      <desc>
        <p>
	  Deliver distribution channel data from a remote node to the
	  local node.
	</p>
	<note><p>
	  Only the process registered as distribution
	  controller for the distribution channel identified by
	  <c><anno>DHandle</anno></c> is allowed to call this
	  function unless an alternate input handler process
	  has been registered using
	  <seealso marker="erlang#dist_ctrl_input_handler/2"><c>erlang:dist_ctrl_input_handler(DHandle, InputHandler)</c></seealso>.
	  If an alternate input handler has been registered, only
	  the registered input handler process is allowed to call
	  this function.
	</p></note>
	<p>
	  This function is used when implementing an alternative
	  distribution carrier using processes as distribution
	  controllers. <c><anno>DHandle</anno></c> is retrived
	  via the callback
	  <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
	  More information can be found in the documentation of
	  <seealso marker="erts:alt_dist#distribution_module">ERTS
	  User's Guide ➜ How to implement an Alternative Carrier
	  for the Erlang Distribution ➜ Distribution Module</seealso>.
	</p>
      </desc>
    </func>

    <func>
      <name name="element" arity="2"/>
      <fsummary>Return the Nth element of a tuple.</fsummary>
      <type_desc variable="N">1..tuple_size(<anno>Tuple</anno>)</type_desc>
      <desc>
        <p>Returns the <c><anno>N</anno></c>th element (numbering from 1) of
          <c><anno>Tuple</anno></c>, for example:</p>
        <pre>
> <input>element(2, {a, b, c}).</input>
b</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="erase" arity="0"/>
      <fsummary>Return and delete the process dictionary.</fsummary>
      <desc>
        <p>Returns the process dictionary and deletes it, for
          example:</p>
        <pre>
> <input>put(key1, {1, 2, 3}),</input>
<input>put(key2, [a, b, c]),</input>
<input>erase().</input>
[{key1,{1,2,3}},{key2,[a,b,c]}]</pre>
      </desc>
    </func>

    <func>
      <name name="erase" arity="1"/>
      <fsummary>Return and delete a value from the process dictionary.
      </fsummary>
      <desc>
        <p>Returns the value <c><anno>Val</anno></c> associated with
          <c><anno>Key</anno></c> and deletes it from the process dictionary.
          Returns <c>undefined</c> if no value is associated with
          <c><anno>Key</anno></c>. Example:</p>
        <pre>
> <input>put(key1, {merry, lambs, are, playing}),</input>
<input>X = erase(key1),</input>
<input>{X, erase(key1)}.</input>
{{merry,lambs,are,playing},undefined}</pre>
      </desc>
    </func>

    <func>
      <name name="error" arity="1"/>
      <fsummary>Stop execution with a specified reason.</fsummary>
      <desc>
        <p>Stops the execution of the calling process with the reason
          <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c>
          is any term. The exit reason is
          <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c>
          is a list of the functions most recently called (the current
          function first). As evaluating this function causes
          the process to terminate, it has no return value. Example:</p>
        <pre>
> <input>catch error(foobar).</input>
{'EXIT',{foobar,[{erl_eval,do_apply,5},
                 {erl_eval,expr,5},
                 {shell,exprs,6},
                 {shell,eval_exprs,6},
                 {shell,eval_loop,3}]}}</pre>
      </desc>
    </func>

    <func>
      <name name="error" arity="2"/>
      <fsummary>Stop execution with a specified reason.</fsummary>
      <desc>
        <p>Stops the execution of the calling process with the reason
          <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c>
          is any term. The exit reason is
          <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c>
          is a list of the functions most recently called (the current
          function first). <c><anno>Args</anno></c> is expected to be the
          list of arguments for the current function; in Beam it is used
          to provide the arguments for the current function in
          the term <c>Where</c>. As evaluating this function causes
          the process to terminate, it has no return value.</p>
      </desc>
    </func>

    <func>
      <name name="exit" arity="1"/>
      <fsummary>Stop execution with a specified reason.</fsummary>
      <desc>
        <p>Stops the execution of the calling process with exit reason
          <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c>
          is any term. As
          evaluating this function causes the process to terminate, it
          has no return value. Example:</p>
        <pre>
> <input>exit(foobar).</input>
** exception exit: foobar
> <input>catch exit(foobar).</input>
{'EXIT',foobar}</pre>
      </desc>
    </func>

    <func>
      <name name="exit" arity="2"/>
      <fsummary>Send an exit signal to a process or a port.</fsummary>
      <desc>
        <p>Sends an exit signal with exit reason <c><anno>Reason</anno></c> to
          the process or port identified by <c><anno>Pid</anno></c>.</p>
        <p>The following behavior applies if <c><anno>Reason</anno></c>
          is any term, except <c>normal</c> or <c>kill</c>:</p>
        <list type="bulleted">
          <item><p>If <c><anno>Pid</anno></c> is not trapping exits,
            <c><anno>Pid</anno></c>
            itself exits with exit reason <c><anno>Reason</anno></c>.</p>
          </item>
          <item><p>If <c><anno>Pid</anno></c> is trapping exits, the exit
            signal is transformed into a message
            <c>{'EXIT', From, <anno>Reason</anno>}</c>
            and delivered to the message queue of <c><anno>Pid</anno></c>.</p>
          </item>
          <item><p><c>From</c> is the process identifier of the process
            that sent the exit signal. See also
            <seealso marker="#process_flag/2">
            <c>process_flag/2</c></seealso>.</p>
          </item>
        </list>
        <p>If <c><anno>Reason</anno></c> is the atom <c>normal</c>,
          <c><anno>Pid</anno></c>
          does not exit. If it is trapping exits, the exit signal is
          transformed into a message <c>{'EXIT', From, normal}</c>
          and delivered to its message queue.</p>
        <p>If <c><anno>Reason</anno></c> is the atom <c>kill</c>,
          that is, if <c>exit(<anno>Pid</anno>, kill)</c> is called,
          an untrappable exit signal is sent to <c><anno>Pid</anno></c>,
          which unconditionally exits with exit reason <c>killed</c>.</p>
      </desc>
    </func>

    <func>
      <name name="external_size" arity="1"/>
      <fsummary>Calculate the maximum size for a term encoded in the Erlang
        external term format.</fsummary>
      <desc>
        <p>Calculates, without doing the encoding, the maximum byte size for
          a term encoded in the Erlang external term format. The following
          condition applies always:</p>
          <pre>
> <input>Size1 = byte_size(term_to_binary(<anno>Term</anno>)),</input>
> <input>Size2 = erlang:external_size(<anno>Term</anno>),</input>
> <input>true = Size1 =&lt; Size2.</input>
true</pre>
        <p>This is equivalent to a call to:</p>
<code>
erlang:external_size(<anno>Term</anno>, [])</code>
      </desc>
    </func>

    <func>
      <name name="external_size" arity="2"/>
      <fsummary>Calculate the maximum size for a term encoded in the Erlang
        external term format.</fsummary>
      <desc>
        <p>Calculates, without doing the encoding, the maximum byte size for
          a term encoded in the Erlang external term format. The following
          condition applies always:</p>
          <pre>
> <input>Size1 = byte_size(term_to_binary(<anno>Term</anno>, <anno>Options</anno>)),</input>
> <input>Size2 = erlang:external_size(<anno>Term</anno>, <anno>Options</anno>),</input>
> <input>true = Size1 =&lt; Size2.</input>
true</pre>
        <p>Option <c>{minor_version, <anno>Version</anno>}</c> specifies how
          floats are encoded. For a detailed description, see
          <seealso marker="#term_to_binary/2">
          <c>term_to_binary/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="float" arity="1"/>
      <fsummary>Convert a number to a float.</fsummary>
      <desc>
        <p>Returns a float by converting <c><anno>Number</anno></c> to a float,
          for example:</p>
        <pre>
> <input>float(55).</input>
55.0</pre>
        <p>Allowed in guard tests.</p>
        <note>
          <p>If used on the top level in a guard, it tests whether the
            argument is a floating point number; for clarity, use
            <seealso marker="#is_float/1"><c>is_float/1</c></seealso>
            instead.</p>
          <p>When <c>float/1</c> is used in an expression in a guard,
            such as '<c>float(A) == 4.0</c>', it converts a number as
            described earlier.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="float_to_binary" arity="1"/>
      <fsummary>Text representation of a float.</fsummary>
      <desc>
        <p>The same as
          <c>float_to_binary(<anno>Float</anno>,[{scientific,20}])</c>.</p>
      </desc>
    </func>

    <func>
      <name name="float_to_binary" arity="2"/>
      <fsummary>Text representation of a float formatted using specified
        options.</fsummary>
      <desc>
        <p>Returns a binary corresponding to the text
          representation of <c><anno>Float</anno></c> using fixed decimal 
          point formatting. <c><anno>Options</anno></c> behaves in the same
          way as <seealso marker="#float_to_list/2">
          <c>float_to_list/2</c></seealso>. Examples:</p>
        <pre>
> <input>float_to_binary(7.12, [{decimals, 4}]).</input>
&lt;&lt;"7.1200">>
> <input>float_to_binary(7.12, [{decimals, 4}, compact]).</input>
&lt;&lt;"7.12">></pre>
      </desc>
    </func>

    <func>
      <name name="float_to_list" arity="1"/>
      <fsummary>Text representation of a float.</fsummary>
      <desc>
        <p>The same as
          <c>float_to_list(<anno>Float</anno>,[{scientific,20}])</c>.</p>
      </desc>
    </func>

    <func>
      <name name="float_to_list" arity="2"/>
      <fsummary>Text representation of a float formatted using specified
        options.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text representation
          of <c>Float</c> using fixed decimal point formatting.</p>
        <p>Available options:</p>
        <list type="bulleted">
          <item><p>If option <c>decimals</c> is specified, the returned value
            contains at most <c>Decimals</c> number of digits past the
            decimal point. If the number does not fit in the internal
            static buffer of 256 bytes, the function throws <c>badarg</c>.</p>
          </item>
          <item><p>If option <c>compact</c> is specified, the trailing zeros
            at the end of the list are truncated. This option is only
            meaningful together with option <c>decimals</c>.</p>
          </item>
          <item><p>If option <c>scientific</c> is specified, the float is
            formatted using scientific notation with <c>Decimals</c>
            digits of precision.</p>
          </item>
          <item><p>If <c>Options</c> is <c>[]</c>, the function behaves as
            <seealso marker="#float_to_list/1">
            <c>float_to_list/1</c></seealso>.</p>
          </item>
        </list>
        <p>Examples:</p>
        <pre>
> <input>float_to_list(7.12, [{decimals, 4}]).</input>
"7.1200"
> <input>float_to_list(7.12, [{decimals, 4}, compact]).</input>
"7.12"</pre>
      </desc>
    </func>

    <func>
      <name name="floor" arity="1"/>
      <fsummary>Returns the largest integer not greater than the argument</fsummary>
      <desc>
        <p>Returns the largest integer not greater than
	<c><anno>Number</anno></c>.
        For example:</p>
        <pre>
> <input>floor(-10.5).</input>
-11</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="fun_info" arity="1"/>
      <fsummary>Information about a fun.</fsummary>
      <desc>
        <p>Returns a list with information about the fun
          <c><anno>Fun</anno></c>. Each list element is a tuple. The order
          of the tuples is undefined, and more tuples can be added in a
          future release.</p>
        <warning>
          <p>This BIF is mainly intended for debugging, but it can
            sometimes be useful in library functions that need
            to verify, for example, the arity of a fun.</p>
        </warning>
        <p>Two types of funs have slightly different semantics:</p>
        <list type="bulleted">
          <item><p>A fun created by <c>fun M:F/A</c> is called an
            <em>external</em> fun. Calling it will always call the
            function <c>F</c> with arity <c>A</c> in the latest code for
            module <c>M</c>. Notice that module <c>M</c> does not even
            need to be loaded when the fun <c>fun M:F/A</c> is created.</p>
          </item>
          <item><p>All other funs are called <em>local</em>. When a local fun
            is called, the same version of the code that created the fun
            is called (even if a newer version of the module has been
            loaded).</p>
          </item>
        </list>
        <p>The following elements are always present in the list
          for both local and external funs:</p>
        <taglist>
          <tag><c>{type, Type}</c></tag>
          <item>
            <p><c>Type</c> is <c>local</c> or <c>external</c>.</p>
          </item>
          <tag><c>{module, Module}</c></tag>
          <item>
            <p><c>Module</c> (an atom) is the module name.</p>
            <p>If <c>Fun</c> is a local fun, <c>Module</c> is the module
              in which the fun is defined.</p>
            <p>If <c>Fun</c> is an external fun, <c>Module</c> is the
              module that the fun refers to.</p>
          </item>
          <tag><c>{name, Name}</c></tag>
          <item>
            <p><c>Name</c> (an atom) is a function name.</p>
            <p>If <c>Fun</c> is a local fun, <c>Name</c> is the name
              of the local function that implements the fun.
              (This name was generated by the compiler, and is
              only of informational use. As it is a local function, it
              cannot be called directly.)
              If no code is currently loaded for the fun, <c>[]</c>
              is returned instead of an atom.</p>
            <p>If <c>Fun</c> is an external fun, <c>Name</c> is the name
              of the exported function that the fun refers to.</p>
          </item>
          <tag><c>{arity, Arity}</c></tag>
          <item>
            <p><c>Arity</c> is the number of arguments that the fun
              is to be called with.</p>
          </item>
          <tag><c>{env, Env}</c></tag>
          <item>
            <p><c>Env</c> (a list) is the environment or free variables
              for the fun. For external funs, the returned list is
              always empty.</p>
          </item>
        </taglist>
        <p>The following elements are only present in the list if
          <c>Fun</c> is local:</p>
        <taglist>
          <tag><c>{pid, Pid}</c></tag>
          <item>
            <p><c>Pid</c> is the process identifier of the process
              that originally created the fun.</p>
          </item>
          <tag><c>{index, Index}</c></tag>
          <item>
            <p><c>Index</c> (an integer) is an index into the module
              fun table.</p>
          </item>
          <tag><c>{new_index, Index}</c></tag>
          <item>
            <p><c>Index</c> (an integer) is an index into the module
              fun table.</p>
          </item>
          <tag><c>{new_uniq, Uniq}</c></tag>
          <item>
            <p><c>Uniq</c> (a binary) is a unique value for this fun. It
              is calculated from the compiled code for the entire module.</p>
          </item>
          <tag><c>{uniq, Uniq}</c></tag>
          <item>
            <p><c>Uniq</c> (an integer) is a unique value for this fun.
              As from Erlang/OTP R15, this integer is calculated from the
              compiled code for the entire module. Before Erlang/OTP R15, this
              integer was based on only the body of the fun.</p>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="fun_info" arity="2"/>
      <fsummary>Information about a fun.</fsummary>
      <type name="fun_info_item"/>
      <desc>
        <p>Returns information about <c><anno>Fun</anno></c> as specified by
          <c><anno>Item</anno></c>, in the form
          <c>{<anno>Item</anno>,<anno>Info</anno>}</c>.</p>
        <p>For any fun, <c><anno>Item</anno></c> can be any of the atoms
          <c>module</c>, <c>name</c>, <c>arity</c>, <c>env</c>, or
          <c>type</c>.</p>
        <p>For a local fun, <c><anno>Item</anno></c> can also be any of the
          atoms <c>index</c>, <c>new_index</c>, <c>new_uniq</c>,
          <c>uniq</c>, and <c>pid</c>. For an external fun, the value
          of any of these items is always the atom <c>undefined</c>.</p>
        <p>See
          <seealso marker="#fun_info/1"><c>erlang:fun_info/1</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="fun_to_list" arity="1"/>
      <fsummary>Text representation of a fun.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of <c><anno>Fun</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="function_exported" arity="3"/>
      <fsummary>Check if a function is exported and loaded.</fsummary>
      <desc>
        <p>Returns <c>true</c> if the module <c><anno>Module</anno></c> is
          loaded and contains an exported function
          <c><anno>Function</anno>/<anno>Arity</anno></c>,
          or if there is a BIF (a built-in function implemented in C)
          with the specified name, otherwise returns <c>false</c>.</p>
        <note>
          <p>This function used to return <c>false</c> for BIFs
            before Erlang/OTP 18.0.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="garbage_collect" arity="0"/>
      <fsummary>Force an immediate garbage collection of the calling process.
      </fsummary>
      <desc>
        <p>Forces an immediate garbage collection of the
          executing process. The function is not to be used unless
          it has been noticed (or there are good reasons to suspect)
          that the spontaneous garbage collection will occur too late
          or not at all.</p>
        <warning>
          <p>Improper use can seriously degrade system performance.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="garbage_collect" arity="1"/>
      <fsummary>Garbage collect a process.</fsummary>
      <desc>
        <p>The same as
          <seealso marker="#garbage_collect/2">
          <c>garbage_collect(<anno>Pid</anno>, [])</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="garbage_collect" arity="2"/>
      <fsummary>Garbage collect a process.</fsummary>
      <desc>
        <p>Garbage collects the node local process identified by
          <c><anno>Pid</anno></c>.</p>
        <p><c><anno>Option</anno></c>:</p>
        <taglist>
          <tag><c>{async, RequestId}</c></tag>
          <item>The function <c>garbage_collect/2</c> returns
            the value <c>async</c> immediately after the request
            has been sent. When the request has been processed, the
            process that called this function is passed a message on
            the form <c>{garbage_collect,
            <anno>RequestId</anno>, <anno>GCResult</anno>}</c>.
          </item>

          <tag><c>{type, 'major' | 'minor'}</c></tag>
          <item>Triggers garbage collection of requested type. Default value is
            <c>'major'</c>, which would trigger a fullsweep GC.
            The option <c>'minor'</c> is considered a hint and may lead to
            either minor or major GC run.</item>
        </taglist>
        <p>If <c><anno>Pid</anno></c> equals <c>self()</c>, and
          no <c>async</c> option has been passed, the garbage
          collection is performed at once, that is, the same as calling
          <seealso marker="#garbage_collect/0">
          <c>garbage_collect/0</c></seealso>.
          Otherwise a request for garbage collection
          is sent to the process identified by <c><anno>Pid</anno></c>,
          and will be handled when appropriate. If no <c>async</c>
          option has been passed, the caller blocks until
          <c><anno>GCResult</anno></c> is available and can be returned.</p>
        <p><c><anno>GCResult</anno></c> informs about the result of
          the garbage collection request as follows:</p>
        <taglist>
          <tag><c>true</c></tag>
          <item>
            The process identified by <c><anno>Pid</anno></c> has
            been garbage collected.
          </item>
          <tag><c>false</c></tag>
          <item>
            No garbage collection was performed, as
            the process identified by <c><anno>Pid</anno></c>
            terminated before the request could be satisfied.
          </item>
        </taglist>
        <p>Notice that the same caveats apply as for
          <seealso marker="#garbage_collect/0">
          <c>garbage_collect/0</c></seealso>.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Pid</anno></c> is not a node local process identifier.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>OptionList</anno></c> is an invalid list of options.
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="get" arity="0"/>
      <fsummary>Return the process dictionary.</fsummary>
      <desc>
        <p>Returns the process dictionary as a list of
          <c>{<anno>Key</anno>, <anno>Val</anno>}</c> tuples, for example:</p>
        <pre>
> <input>put(key1, merry),</input>
<input>put(key2, lambs),</input>
<input>put(key3, {are, playing}),</input>
<input>get().</input>
[{key1,merry},{key2,lambs},{key3,{are,playing}}]</pre>
      </desc>
    </func>

    <func>
      <name name="get" arity="1"/>
      <fsummary>Return a value from the process dictionary.</fsummary>
      <desc>
        <p>Returns the value <c><anno>Val</anno></c> associated with
          <c><anno>Key</anno></c> in the process dictionary, or <c>undefined</c>
          if <c><anno>Key</anno></c> does not exist. Example:</p>
        <pre>
> <input>put(key1, merry),</input>
<input>put(key2, lambs),</input>
<input>put({any, [valid, term]}, {are, playing}),</input>
<input>get({any, [valid, term]}).</input>
{are,playing}</pre>
      </desc>
    </func>

    <func>
      <name name="get_cookie" arity="0"/>
      <fsummary>Get the magic cookie of the local node.</fsummary>
      <desc>
        <p>Returns the magic cookie of the local node if the node is
          alive, otherwise the atom <c>nocookie</c>.</p>
      </desc>
    </func>

    <func>
      <name name="get_keys" arity="0"/>
      <fsummary>Return a list of all keys from the process dictionary.
      </fsummary>
      <desc>
        <p>Returns a list of all keys present in the process dictionary,
          for example:</p>
        <pre>
> <input>put(dog, {animal,1}),</input>
<input>put(cow, {animal,2}),</input>
<input>put(lamb, {animal,3}),</input>
<input>get_keys().</input>
[dog,cow,lamb]</pre>
      </desc>
    </func>

    <func>
      <name name="get_keys" arity="1"/>
      <fsummary>Return a list of keys from the process dictionary.</fsummary>
      <desc>
        <p>Returns a list of keys that are associated with the value
          <c><anno>Val</anno></c> in the process dictionary, for example:</p>
        <pre>
> <input>put(mary, {1, 2}),</input>
<input>put(had, {1, 2}),</input>
<input>put(a, {1, 2}),</input>
<input>put(little, {1, 2}),</input>
<input>put(dog, {1, 3}),</input>
<input>put(lamb, {1, 2}),</input>
<input>get_keys({1, 2}).</input>
[mary,had,a,little,lamb]</pre>
      </desc>
    </func>

    <func>
      <name name="get_stacktrace" arity="0"/>
      <fsummary>Get the call stack back-trace of the last exception.</fsummary>
      <type name="stack_item"/>
      <desc>
        <p>Gets the call stack back-trace (<em>stacktrace</em>) for an
          exception that has just been caught
	  in the calling process as a list of
          <c>{<anno>Module</anno>,<anno>Function</anno>,<anno>Arity</anno>,<anno>Location</anno>}</c>
          tuples. Field <c><anno>Arity</anno></c> in the first tuple can be the
          argument list of that function call instead of an arity integer,
          depending on the exception.</p>
        <p>If there has not been any exceptions in a process, the
          stacktrace is <c>[]</c>. After a code change for the process,
          the stacktrace can also be reset to <c>[]</c>.</p>
	<p><c>erlang:get_stacktrace/0</c> is only guaranteed to return
	a stacktrace if called (directly or indirectly) from within the
	scope of a <c>try</c> expression. That is, the following call works:</p>
<pre>
try Expr
catch
  C:R ->
   {C,R,erlang:get_stacktrace()}
end</pre>
	<p>As does this call:</p>
<pre>
try Expr
catch
  C:R ->
   {C,R,helper()}
end

helper() ->
  erlang:get_stacktrace().</pre>

        <warning><p>In a future release,
        <c>erlang:get_stacktrace/0</c> will return <c>[]</c> if called
        from outside a <c>try</c> expression.</p></warning>
        <p>The stacktrace is the same data as operator <c>catch</c>
          returns, for example:</p>
        <pre>
{'EXIT',{badarg,Stacktrace}} = catch abs(x)</pre>
        <p><c><anno>Location</anno></c> is a (possibly empty) list
          of two-tuples that
          can indicate the location in the source code of the function.
          The first element is an atom describing the type of
          information in the second element. The following
          items can occur:</p>
        <taglist>
          <tag><c>file</c></tag>
          <item>The second element of the tuple is a string (list of
            characters) representing the filename of the source file
            of the function.
          </item>
          <tag><c>line</c></tag>
          <item>The second element of the tuple is the line number
            (an integer &gt; 0) in the source file
            where the exception occurred or the function was called.
          </item>
        </taglist>
        <warning><p>Developers should rely on stacktrace entries only for
          debugging purposes.</p>
          <p>The VM performs tail call optimization, which
          does not add new entries to the stacktrace, and also limits stacktraces
          to a certain depth. Furthermore, compiler options, optimizations and
          future changes may add or remove stacktrace entries, causing any code
          that expects the stacktrace to be in a certain order or contain specific
          items to fail.</p>
          <p>The only exception to this rule is <c>error:undef</c> which
          guarantees to include the <anno>Module</anno>, <anno>Function</anno> and <anno>Arity</anno>
          of the attempted function as the first stacktrace entry.</p>
        </warning>	
        <p>See also
          <seealso marker="#error/1"><c>error/1</c></seealso> and
          <seealso marker="#error/2"><c>error/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="group_leader" arity="0"/>
      <fsummary>Get the group leader for the calling process.</fsummary>
      <desc>
        <p>Returns the process identifier of the group leader for the
          process evaluating the function.</p>
        <p>Every process is a member of some process group and all
          groups have a <em>group leader</em>. All I/O from the group
          is channeled to the group leader. When a new process is
          spawned, it gets the same group leader as the spawning
          process. Initially, at system startup, <c>init</c> is both
          its own group leader and the group leader of all processes.</p>
      </desc>
    </func>

    <func>
      <name name="group_leader" arity="2"/>
      <fsummary>Set the group leader for a process.</fsummary>
      <desc>
        <p>Sets the group leader of <c><anno>Pid</anno></c>
          to <c><anno>GroupLeader</anno></c>.
          Typically, this is used when a process started from a
          certain shell is to have another group leader than
          <c>init</c>.</p>
        <p>See also
          <seealso marker="#group_leader/0"><c>group_leader/0</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="halt" arity="0"/>
      <fsummary>Halt the Erlang runtime system and indicate normal exit to
        the calling environment.</fsummary>
      <desc>
        <p>The same as
          <seealso marker="#halt/2"><c>halt(0, [])</c></seealso>. Example:</p>
        <pre>
> <input>halt().</input>
os_prompt%</pre>
      </desc>
    </func>

    <func>
      <name name="halt" arity="1"/>
      <fsummary>Halt the Erlang runtime system.</fsummary>
      <desc>
        <p>The same as <seealso marker="#halt/2">
          <c>halt(<anno>Status</anno>, [])</c></seealso>. Example:</p>
        <pre>
> <input>halt(17).</input>
os_prompt% <input>echo $?</input>
17
os_prompt%</pre>
      </desc>
    </func>

    <func>
      <name name="halt" arity="2"/>
      <fsummary>Halt the Erlang runtime system.</fsummary>
      <desc>
        <p><c><anno>Status</anno></c> must be a non-negative integer, a string,
          or the atom <c>abort</c>.
          Halts the Erlang runtime system. Has no return value.
          Depending on <c><anno>Status</anno></c>, the following occurs:</p>
        <taglist>
          <tag>integer()</tag>
          <item>The runtime system exits with integer value
            <c><anno>Status</anno></c>
            as status code to the calling environment (OS).
	    <note>
	      <p>On many platforms, the OS supports only status
	      codes 0-255. A too large status code is truncated by clearing
	      the high bits.</p>
	    </note>
          </item>
          <tag>string()</tag>
          <item>An Erlang crash dump is produced with <c><anno>Status</anno></c>
            as slogan. Then the runtime system exits with status code <c>1</c>.
	    The string will be truncated if longer than 200 characters.
	    <note>
	      <p>Before ERTS 9.1 (OTP-20.1) only code points in the range 0-255
	         was accepted in the string. Now any unicode string is valid.</p>
	    </note>
          </item>
          <tag><c>abort</c></tag>
          <item>The runtime system aborts producing a core dump, if that is
            enabled in the OS.
          </item>
        </taglist>
        <p>For integer <c><anno>Status</anno></c>, the Erlang runtime system
          closes all ports and allows async threads to finish their
          operations before exiting. To exit without such flushing, use
          <c><anno>Option</anno></c> as <c>{flush,false}</c>.</p>
        <p>For statuses <c>string()</c> and <c>abort</c>, option
          <c>flush</c> is ignored and flushing is <em>not</em> done.</p>
      </desc>
    </func>

    <func>
      <name name="hd" arity="1"/>
      <fsummary>Head of a list.</fsummary>
      <desc>
        <p>Returns the head of <c><anno>List</anno></c>, that is,
          the first element, for example:</p>
        <pre>
> <input>hd([1,2,3,4,5]).</input>
1</pre>
        <p>Allowed in guard tests.</p>
        <p>Failure: <c>badarg</c> if <c><anno>List</anno></c> is the empty
          list <c>[]</c>.</p>
      </desc>
    </func>

    <func>
      <name name="hibernate" arity="3"/>
      <fsummary>Hibernate a process until a message is sent to it.</fsummary>
      <desc>
        <p>Puts the calling process into a wait state where its memory
          allocation has been reduced as much as possible. This is
          useful if the process does not expect to receive any messages
          soon.</p>
        <p>The process is awaken when a message is sent to it, and control
          resumes in <c><anno>Module</anno>:<anno>Function</anno></c> with
          the arguments specified by <c><anno>Args</anno></c> with the call
          stack emptied, meaning that the process terminates when that
          function returns. Thus <c>erlang:hibernate/3</c> never
          returns to its caller.</p>
        <p>If the process has any message in its message queue,
          the process is awakened immediately in the same way as
          described earlier.</p>
        <p>In more technical terms, <c>erlang:hibernate/3</c>
          discards the call stack for the process,
          and then garbage collects the process. After this,
          all live data is in one continuous heap. The heap
          is then shrunken to the exact same size as the live data
          that it holds (even if that size is less than the minimum
          heap size for the process).</p>
        <p>If the size of the live data in the process is less than
          the minimum heap size, the first garbage collection occurring
          after the process is awakened ensures that the heap
          size is changed to a size not smaller than the minimum heap
          size.</p>
        <p>Notice that emptying the call stack means that any surrounding
          <c>catch</c> is removed and must be re-inserted after
          hibernation. One effect of this is that processes started
          using <c>proc_lib</c> (also indirectly, such as
          <c>gen_server</c> processes), are to use
          <seealso marker="stdlib:proc_lib#hibernate/3">
          <c>proc_lib:hibernate/3</c></seealso>
          instead, to ensure that the exception handler continues to work
          when the process wakes up.</p>
      </desc>
    </func>

    <func>
      <name name="insert_element" arity="3"/>
      <fsummary>Insert an element at index in a tuple.</fsummary>
      <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno>)
        + 1</type_desc>
      <desc>
        <p>Returns a new tuple with element <c><anno>Term</anno></c>
          inserted at position
          <c><anno>Index</anno></c> in tuple <c><anno>Tuple1</anno></c>.
          All elements from position <c><anno>Index</anno></c> and upwards are
          pushed one step higher in the new tuple <c><anno>Tuple2</anno></c>.
          Example:</p>
        <pre>
> <input>erlang:insert_element(2, {one, two, three}, new).</input>
{one,new,two,three}</pre>
      </desc>
    </func>

    <func>
      <name name="integer_to_binary" arity="1"/>
      <fsummary>Text representation of an integer.</fsummary>
      <desc>
        <p>Returns a binary corresponding to the text
          representation of <c><anno>Integer</anno></c>, for example:</p>
        <pre>
> <input>integer_to_binary(77).</input>
&lt;&lt;"77">></pre>
      </desc>
    </func>

    <func>
      <name name="integer_to_binary" arity="2"/>
      <fsummary>Text representation of an integer.</fsummary>
      <desc>
        <p>Returns a binary corresponding to the text
          representation of <c><anno>Integer</anno></c> in base
          <c><anno>Base</anno></c>, for example:</p>
        <pre>
> <input>integer_to_binary(1023, 16).</input>
&lt;&lt;"3FF">></pre>
      </desc>
    </func>

    <func>
      <name name="integer_to_list" arity="1"/>
      <fsummary>Text representation of an integer.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of <c><anno>Integer</anno></c>, for example:</p>
        <pre>
> <input>integer_to_list(77).</input>
"77"</pre>
      </desc>
    </func>

    <func>
      <name name="integer_to_list" arity="2"/>
      <fsummary>Text representation of an integer.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of <c><anno>Integer</anno></c> in base
          <c><anno>Base</anno></c>, for example:</p>
        <pre>
> <input>integer_to_list(1023, 16).</input>
"3FF"</pre>
      </desc>
    </func>

    <func>
      <name name="iolist_size" arity="1"/>
      <fsummary>Size of an iolist.</fsummary>
      <desc>
        <p>Returns an integer, that is the size in bytes,
          of the binary that would be the result of
          <c>iolist_to_binary(<anno>Item</anno>)</c>, for example:</p>
        <pre>
> <input>iolist_size([1,2|&lt;&lt;3,4>>]).</input>
4</pre>
      </desc>
    </func>

    <func>
      <name name="iolist_to_binary" arity="1"/>
      <fsummary>Convert an iolist to a binary.</fsummary>
      <desc>
        <p>Returns a binary that is made from the integers and
          binaries in <c><anno>IoListOrBinary</anno></c>, for example:</p>
        <pre>
> <input>Bin1 = &lt;&lt;1,2,3&gt;&gt;.</input>
&lt;&lt;1,2,3&gt;&gt;
> <input>Bin2 = &lt;&lt;4,5&gt;&gt;.</input>
&lt;&lt;4,5&gt;&gt;
> <input>Bin3 = &lt;&lt;6&gt;&gt;.</input>
&lt;&lt;6&gt;&gt;
> <input>iolist_to_binary([Bin1,1,[2,3,Bin2],4|Bin3]).</input>
&lt;&lt;1,2,3,1,2,3,4,5,4,6&gt;&gt;</pre>
      </desc>
    </func>

    <func>
      <name name="iolist_to_iovec" arity="1"/>
      <fsummary>Converts an iolist to a iovec.</fsummary>
      <desc>
        <p>Returns an iovec that is made from the integers and binaries in
          <c><anno>IoListOrBinary</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="is_alive" arity="0"/>
      <fsummary>Check whether the local node is alive.</fsummary>
      <desc>
        <p>Returns <c>true</c> if the local node is alive (that is, if
          the node can be part of a distributed system), otherwise
          <c>false</c>.</p>
      </desc>
    </func>

    <func>
      <name name="is_atom" arity="1"/>
      <fsummary>Check whether a term is an atom.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an atom,
          otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_binary" arity="1"/>
      <fsummary>Check whether a term is a binary.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a binary,
          otherwise <c>false</c>.</p>
        <p>A binary always contains a complete number of bytes.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_bitstring" arity="1"/>
      <fsummary>Check whether a term is a bitstring.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a
          bitstring (including a binary), otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_boolean" arity="1"/>
      <fsummary>Check whether a term is a boolean.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is the
          atom <c>true</c> or the atom <c>false</c> (that is, a boolean).
          Otherwise returns <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_builtin" arity="3"/>
      <fsummary>Check if a function is a BIF implemented in C.</fsummary>
      <desc>
        <p>This BIF is useful for builders of cross-reference tools.</p>
        <p>Returns <c>true</c> if
          <c><anno>Module</anno>:<anno>Function</anno>/<anno>Arity</anno></c>
          is a BIF implemented in C, otherwise <c>false</c>.</p>
      </desc>
    </func>

    <func>
      <name name="is_float" arity="1"/>
      <fsummary>Check whether a term is a float.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a floating point
          number, otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_function" arity="1"/>
      <fsummary>Check whether a term is a fun.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a fun, otherwise
          <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_function" arity="2"/>
      <fsummary>Check whether a term is a fun with a specified given arity.
      </fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a fun that can be
          applied with <c><anno>Arity</anno></c> number of arguments, otherwise
          <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_integer" arity="1"/>
      <fsummary>Check whether a term is an integer.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an integer,
          otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_list" arity="1"/>
      <fsummary>Check whether a term is a list.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a list with
          zero or more elements, otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_map" arity="1"/>
      <fsummary>Check whether a term is a map.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a map,
          otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_number" arity="1"/>
      <fsummary>Check whether a term is a number.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an integer or a
          floating point number. Otherwise returns <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_pid" arity="1"/>
      <fsummary>Check whether a term is a process identifier.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a process
          identifier, otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_port" arity="1"/>
      <fsummary>Check whether a term is a port.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a port identifier,
          otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_process_alive" arity="1"/>
      <fsummary>Check whether a process is alive.</fsummary>
      <desc>
        <p><c><anno>Pid</anno></c> must refer to a process at the local
          node.</p>
        <p>Returns <c>true</c> if the process exists and is alive, that
          is, is not exiting and has not exited. Otherwise returns
          <c>false</c>.</p>
      </desc>
    </func>

    <func>
      <name name="is_record" arity="2"/>
      <fsummary>Check whether a term appears to be a record.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a tuple and its
          first element is <c><anno>RecordTag</anno></c>.
          Otherwise returns <c>false</c>.</p>
        <note>
          <p>Normally the compiler treats calls to <c>is_record/2</c>
            especially. It emits code to verify that <c><anno>Term</anno></c>
            is a tuple, that its first element is
            <c><anno>RecordTag</anno></c>, and that the
            size is correct. However, if <c><anno>RecordTag</anno></c> is
            not a literal atom, the BIF <c>is_record/2</c> is called
            instead and the size of the tuple is not verified.</p>
        </note>
        <p>Allowed in guard tests, if <c><anno>RecordTag</anno></c> is
          a literal atom.</p>
      </desc>
    </func>

    <func>
      <name name="is_record" arity="3"/>
      <fsummary>Check whether a term appears to be a record.</fsummary>
      <desc>
        <p><c><anno>RecordTag</anno></c> must be an atom.</p>
        <p>Returns <c>true</c> if
          <c><anno>Term</anno></c> is a tuple,
          its first element is <c><anno>RecordTag</anno></c>,
          and its size is <c><anno>Size</anno></c>.
          Otherwise returns <c>false</c>.</p>
        <p>Allowed in guard tests if <c><anno>RecordTag</anno></c> is
          a literal atom and <c>Size</c> is a literal integer.</p>
        <note>
          <p>This BIF is documented for completeness. Usually
            <c>is_record/2</c> is to be used.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="is_reference" arity="1"/>
      <fsummary>Check whether a term is a reference.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a reference,
          otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="is_tuple" arity="1"/>
      <fsummary>Check whether a term is a tuple.</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a tuple,
          otherwise <c>false</c>.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="length" arity="1"/>
      <fsummary>Length of a list.</fsummary>
      <desc>
        <p>Returns the length of <c><anno>List</anno></c>, for example:</p>
        <pre>
> <input>length([1,2,3,4,5,6,7,8,9]).</input>
9</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="link" arity="1"/>
      <fsummary>Create a link to another process (or port).</fsummary>
      <desc>
        <p>Creates a link between the calling process and another
          process (or port) <c><anno>PidOrPort</anno></c>, if there is
          not such a link
          already. If a process attempts to create a link to itself,
          nothing is done. Returns <c>true</c>.</p>
        <p>If <c><anno>PidOrPort</anno></c> does not exist, the behavior
          of the BIF
          depends on if the calling process is trapping exits or not (see
          <seealso marker="#process_flag/2">
          <c>process_flag/2</c></seealso>):</p>
        <list type="bulleted">
          <item><p>If the calling process is not trapping exits, and
            checking <c><anno>PidOrPort</anno></c> is cheap
            (that is, if <c><anno>PidOrPort</anno></c>
            is local), <c>link/1</c> fails with reason <c>noproc</c>.</p></item>
          <item><p>Otherwise, if the calling process is trapping exits,
            and/or <c><anno>PidOrPort</anno></c> is remote, <c>link/1</c>
            returns <c>true</c>, but an exit signal with reason <c>noproc</c>
            is sent to the calling process.</p></item>
        </list>
      </desc>
    </func>

    <func>
      <name name="list_to_atom" arity="1"/>
      <fsummary>Convert from text representation to an atom.</fsummary>
      <desc>
        <p>Returns the atom whose text representation is
          <c><anno>String</anno></c>.</p>
        <p>As from Erlang/OTP 20, <c><anno>String</anno></c> may contain
          any Unicode character. Earlier versions allowed only ISO-latin-1
          characters as the implementation did not allow Unicode characters
          above 255. For more information on Unicode support in atoms, see
          <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8
          encoded atoms</seealso>
          in section "External Term Format" in the User's Guide.</p>
        <p>Example:</p>
        <pre>
> <input>list_to_atom("Erlang").</input>
'Erlang'</pre>
      </desc>
    </func>

    <func>
      <name name="list_to_binary" arity="1"/>
      <fsummary>Convert a list to a binary.</fsummary>
      <desc>
        <p>Returns a binary that is made from the integers and
          binaries in <c><anno>IoList</anno></c>, for example:</p>
        <pre>
> <input>Bin1 = &lt;&lt;1,2,3&gt;&gt;.</input>
&lt;&lt;1,2,3&gt;&gt;
> <input>Bin2 = &lt;&lt;4,5&gt;&gt;.</input>
&lt;&lt;4,5&gt;&gt;
> <input>Bin3 = &lt;&lt;6&gt;&gt;.</input>
&lt;&lt;6&gt;&gt;
> <input>list_to_binary([Bin1,1,[2,3,Bin2],4|Bin3]).</input>
&lt;&lt;1,2,3,1,2,3,4,5,4,6&gt;&gt;</pre>
      </desc>
    </func>

    <func>
      <name name="list_to_bitstring" arity="1"/>
      <fsummary>Convert a list to a bitstring.</fsummary>
      <type name="bitstring_list"/>
      <desc>
        <p>Returns a bitstring that is made from the integers and
          bitstrings in <c><anno>BitstringList</anno></c>. (The last tail in
          <c><anno>BitstringList</anno></c> is allowed to be a bitstring.)
          Example:</p>
        <pre>
> <input>Bin1 = &lt;&lt;1,2,3&gt;&gt;.</input>
&lt;&lt;1,2,3&gt;&gt;
> <input>Bin2 = &lt;&lt;4,5&gt;&gt;.</input>
&lt;&lt;4,5&gt;&gt;
> <input>Bin3 = &lt;&lt;6,7:4&gt;&gt;.</input>
&lt;&lt;6,7:4&gt;&gt;
> <input>list_to_bitstring([Bin1,1,[2,3,Bin2],4|Bin3]).</input>
&lt;&lt;1,2,3,1,2,3,4,5,4,6,7:4&gt;&gt;</pre>
      </desc>
    </func>

    <func>
      <name name="list_to_existing_atom" arity="1"/>
      <fsummary>Convert from text representation to an atom.</fsummary>
      <desc>
        <p>Returns the atom whose text representation is
          <c><anno>String</anno></c>,
          but only if there already exists such atom.</p>
        <p>Failure: <c>badarg</c> if there does not already exist an atom
          whose text representation is <c><anno>String</anno></c>.</p>
	<note>
	  <p>Note that the compiler may optimize away atoms. For
	  example, the compiler will rewrite
	  <c>atom_to_list(some_atom)</c> to <c>"some_atom"</c>. If
	  that expression is the only mention of the atom
	  <c>some_atom</c> in the containing module, the atom will not
	  be created when the module is loaded, and a subsequent call
	  to <c>list_to_existing_atom("some_atom")</c> will fail.</p>
	</note>
      </desc>
    </func>

    <func>
      <name name="list_to_float" arity="1"/>
      <fsummary>Convert from text representation to a float.</fsummary>
      <desc>
        <p>Returns the float whose text representation is
          <c><anno>String</anno></c>, for example:</p>
        <pre>
> <input>list_to_float("2.2017764e+0").</input>
2.2017764</pre>
        <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad
          representation of a float.</p>
      </desc>
    </func>

    <func>
      <name name="list_to_integer" arity="1"/>
      <fsummary>Convert from text representation to an integer.</fsummary>
      <desc>
        <p>Returns an integer whose text representation is
          <c><anno>String</anno></c>, for example:</p>
        <pre>
> <input>list_to_integer("123").</input>
123</pre>
        <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad
          representation of an integer.</p>
      </desc>
    </func>

    <func>
      <name name="list_to_integer" arity="2"/>
      <fsummary>Convert from text representation to an integer.</fsummary>
      <desc>
        <p>Returns an integer whose text representation in base
          <c><anno>Base</anno></c> is <c><anno>String</anno></c>,
          for example:</p>
        <pre>
> <input>list_to_integer("3FF", 16).</input>
1023</pre>
        <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad
          representation of an integer.</p>
      </desc>
    </func>

    <func>
      <name name="list_to_pid" arity="1"/>
      <fsummary>Convert from text representation to a pid.</fsummary>
      <desc>
        <p>Returns a process identifier whose text representation is a 
          <c><anno>String</anno></c>, for example:</p>
        <pre>
> <input>list_to_pid("&lt;0.4.1>").</input>
&lt;0.4.1></pre>
        <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad
          representation of a process identifier.</p>
        <warning>
          <p>This BIF is intended for debugging and is not to be used
            in application programs.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="list_to_port" arity="1"/>
      <fsummary>Convert from text representation to a port.</fsummary>
      <desc>
        <p>Returns a port identifier whose text representation is a
          <c><anno>String</anno></c>, for example:</p>
        <pre>
> <input>list_to_port("#Port&lt;0.4>").</input>
#Port&lt;0.4></pre>
        <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad
          representation of a port identifier.</p>
        <warning>
          <p>This BIF is intended for debugging and is not to be used
            in application programs.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="list_to_ref" arity="1"/>
      <fsummary>Convert from text representation to a ref.</fsummary>
      <desc>
        <p>Returns a reference whose text representation is a
          <c><anno>String</anno></c>, for example:</p>
        <pre>
> <input>list_to_ref("#Ref&lt;0.4192537678.4073193475.71181>").</input>
#Ref&lt;0.4192537678.4073193475.71181></pre>
        <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad
          representation of a reference.</p>
        <warning>
          <p>This BIF is intended for debugging and is not to be used
            in application programs.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="list_to_tuple" arity="1"/>
      <fsummary>Convert a list to a tuple.</fsummary>
      <desc>
        <p>Returns a tuple corresponding to <c><anno>List</anno></c>,
          for example</p>
        <pre>
> <input>list_to_tuple([share, ['Ericsson_B', 163]]).</input>
{share, ['Ericsson_B', 163]}</pre>
        <p><c><anno>List</anno></c> can contain any Erlang terms.</p>
      </desc>
    </func>

    <func>
      <name name="load_module" arity="2"/>
      <fsummary>Load object code for a module.</fsummary>
      <desc>
        <p>If <c><anno>Binary</anno></c> contains the object code for module
          <c><anno>Module</anno></c>, this BIF loads that object code. If
          the code for module <c><anno>Module</anno></c> already exists, all
          export references are replaced so they point to the newly
          loaded code. The previously loaded code is kept in the system
          as old code, as there can still be processes executing
          that code.</p>
        <p>Returns either <c>{module, <anno>Module</anno>}</c>, or
          <c>{error, <anno>Reason</anno>}</c> if loading fails.
          <c><anno>Reason</anno></c> is one of the following:</p>
        <taglist>
          <tag><c>badfile</c></tag>
          <item>The object code in <c><anno>Binary</anno></c> has an
            incorrect format <em>or</em> the object code contains code
            for another module than <c><anno>Module</anno></c>.
          </item>
          <tag><c>not_purged</c></tag>
          <item><c><anno>Binary</anno></c> contains a module that cannot be
            loaded because old code for this module already exists.
          </item>
        </taglist>
        <warning>
          <p>This BIF is intended for the code server (see
            <seealso marker="kernel:code"><c>code(3)</c></seealso>)
            and is not to be used elsewhere.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="load_nif" arity="2"/>
      <fsummary>Load NIF library.</fsummary>
      <desc>
        <p>Loads and links a dynamic library containing native
          implemented functions (NIFs) for a module. <c><anno>Path</anno></c>
          is a file path to the shareable object/dynamic library file minus
          the OS-dependent file extension (<c>.so</c> for Unix and
          <c>.dll</c> for Windows). Notice that on most OSs the library has
          to have a different name on disc when an upgrade of the nif is
          done. If the name is the same, but the contents differ, the
          old library may be loaded instead. For information on how to
          implement a NIF library, see
        <seealso marker="erl_nif"><c>erl_nif(3)</c></seealso>.</p>
        <p><c><anno>LoadInfo</anno></c> can be any term. It is passed on to
          the library as part of the initialization. A good practice is
          to include a module version number to support future code
          upgrade scenarios.</p>
        <p>The call to <c>load_nif/2</c> must be made
          <em>directly</em> from the Erlang code of the module that the
          NIF library belongs to. It returns either <c>ok</c>, or
          <c>{error,{<anno>Reason</anno>,Text}}</c> if loading fails.
          <c><anno>Reason</anno></c> is one of the following atoms
          while <c><anno>Text</anno></c> is a human readable string that
          can give more information about the failure:</p>
        <taglist>
          <tag><c>load_failed</c></tag>
          <item>The OS failed to load the NIF library.
          </item>
          <tag><c>bad_lib</c></tag>
          <item>The library did not fulfill the requirements as a NIF
            library of the calling module.
          </item>
          <tag><c>load | upgrade</c></tag>
          <item>The corresponding library callback was unsuccessful.
          </item>
          <tag><c>reload</c></tag>
          <item>A NIF library is already loaded for this module instance.
	    The previously deprecated <c>reload</c> feature was removed in OTP 20.
          </item>
          <tag><c>old_code</c></tag>
          <item>The call to <c>load_nif/2</c> was made from the old
            code of a module that has been upgraded; this is not
            allowed.
          </item>
	  <tag><c>notsup</c></tag>
          <item>Lack of support. Such as loading NIF library for a
	    HiPE compiled module.
	  </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="loaded" arity="0"/>
      <fsummary>List all loaded modules.</fsummary>
      <desc>
        <p>Returns a list of all loaded Erlang modules (current and
          old code), including preloaded modules.</p>
        <p>See also <seealso marker="kernel:code">
          <c>code(3)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="localtime" arity="0"/>
      <fsummary>Current local date and time.</fsummary>
      <desc>
        <p>Returns the current local date and time,
          <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c>,
          for example:</p>
        <pre>
> <input>erlang:localtime().</input>
{{1996,11,6},{14,45,17}}</pre>
        <p>The time zone and Daylight Saving Time correction depend
          on the underlying OS.</p>
      </desc>
    </func>

    <func>
      <name name="localtime_to_universaltime" arity="1"/>
      <fsummary>Convert from local to Universal Time Coordinated (UTC) date
        and time.</fsummary>
      <desc>
        <p>Converts local date and time to Universal Time Coordinated
          (UTC), if supported by the underlying OS. Otherwise
          no conversion is done and <c><anno>Localtime</anno></c>
          is returned. Example:</p>
        <pre>
> <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}).</input>
{{1996,11,6},{13,45,17}}</pre>
        <p>Failure: <c>badarg</c> if <c><anno>Localtime</anno></c> denotes an
          invalid date and time.</p>
      </desc>
    </func>

    <func>
      <name name="localtime_to_universaltime" arity="2"/>
      <fsummary>Convert from local to Universal Time Coordinated (UTC) date
        and time.</fsummary>
      <desc>
        <p>Converts local date and time to Universal Time Coordinated
          (UTC) as <c>erlang:localtime_to_universaltime/1</c>,
          but the caller decides if Daylight Saving Time is active.</p>
        <p>If <c><anno>IsDst</anno> == true</c>, <c><anno>Localtime</anno></c>
          is during Daylight Saving Time, if <c><anno>IsDst</anno> == false</c>
          it is not. If <c><anno>IsDst</anno> == undefined</c>, the underlying
          OS can guess, which is the same as calling
          <c>erlang:localtime_to_universaltime(<anno>Localtime</anno>)</c>.</p>
        <p>Examples:</p>
        <pre>
> <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, true).</input>
{{1996,11,6},{12,45,17}}
> <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, false).</input>
{{1996,11,6},{13,45,17}}
> <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, undefined).</input>
{{1996,11,6},{13,45,17}}</pre>
        <p>Failure: <c>badarg</c> if <c><anno>Localtime</anno></c> denotes an
          invalid date and time.</p>
      </desc>
    </func>

    <func>
      <name name="make_ref" arity="0"/>
      <fsummary>Return a unique reference.</fsummary>
      <desc>
        <p>Returns a
          <seealso marker="doc/efficiency_guide:advanced#unique_references">
          unique reference</seealso>. The reference is unique among
          connected nodes.</p>
        <warning>
          <p>Known issue: When a node is restarted multiple
            times with the same node name, references created
            on a newer node can be mistaken for a reference
            created on an older node with the same node name.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="make_tuple" arity="2"/>
      <fsummary>Create a new tuple of a specified arity.</fsummary>
      <desc>
        <p>Creates a new tuple of the specified <c><anno>Arity</anno></c>, where
          all elements are <c><anno>InitialValue</anno></c>, for example:</p>
        <pre>
> <input>erlang:make_tuple(4, []).</input>
{[],[],[],[]}</pre>
      </desc>
    </func>

    <func>
      <name name="make_tuple" arity="3"/>
      <fsummary>Create a new tuple with specifed arity and contents.</fsummary>
      <desc>
        <p>Creates a tuple of size <c><anno>Arity</anno></c>, where each element
          has value <c><anno>DefaultValue</anno></c>, and then fills in
          values from <c><anno>InitList</anno></c>.
          Each list element in <c><anno>InitList</anno></c>
          must be a two-tuple, where the first element is a position in the
          newly created tuple and the second element is any term. If a
          position occurs more than once in the list, the term corresponding
          to the last occurrence is used. Example:</p>
        <pre>
> <input>erlang:make_tuple(5, [], [{2,ignored},{5,zz},{2,aa}]).</input>
{[],aa,[],[],zz}</pre>
      </desc>
    </func>

    <func>
      <name name="map_size" arity="1"/>
      <fsummary>Return the size of a map.</fsummary>
      <desc>
        <p>Returns an integer, which is the number of key-value pairs
          in <c><anno>Map</anno></c>, for example:</p>
        <pre>
> <input>map_size(#{a=>1, b=>2, c=>3}).</input>
3</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="match_spec_test" arity="3"/>
      <fsummary>Test that a match specification works.</fsummary>
      <desc>
        <p>Tests a match specification used in calls to
          <seealso marker="stdlib:ets#select/2"><c>ets:select/2</c></seealso>
          and <seealso marker="#trace_pattern/3">
          <c>erlang:trace_pattern/3</c></seealso>.
          The function tests both a match specification for "syntactic"
          correctness and runs the match specification against the object. If
          the match specification contains errors, the tuple <c>{error,
          Errors}</c> is returned, where <c>Errors</c> is a list of natural
          language descriptions of what was wrong with the match
          specification.</p>
        <p>If <c><anno>Type</anno></c> is <c>table</c>, the object to match
          against is to be a tuple. The function then returns
          <c>{ok,Result,[],Warnings}</c>, where <c>Result</c> is what would
          have been the result in a real <c>ets:select/2</c> call, or
          <c>false</c> if the match specification does not match the object
          tuple.</p>
        <p>If <c><anno>Type</anno></c> is <c>trace</c>, the object to match
          against is to be a list. The function returns
          <c>{ok, Result, Flags, Warnings}</c>, where <c>Result</c> is one of
          the following:</p>
        <list type="bulleted">
          <item><c>true</c> if a trace message is to be emitted</item>
          <item><c>false</c> if a trace message is not to be emitted</item>
          <item>The message term to be appended to the trace message</item>
        </list>
        <p><c>Flags</c> is a list containing all the trace flags to be enabled,
          currently this is only <c>return_trace</c>.</p>
        <p>This is a useful debugging and test tool, especially when writing
          complicated match specifications.</p>
        <p>See also
          <seealso marker="stdlib:ets#test_ms/2"><c>ets:test_ms/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="max" arity="2"/>
      <fsummary>Return the largest of two terms.</fsummary>
      <desc>
        <p>Returns the largest of <c><anno>Term1</anno></c> and
          <c><anno>Term2</anno></c>.
          If the terms are equal, <c><anno>Term1</anno></c> is returned.</p>
      </desc>
    </func>

    <func>
      <name name="md5" arity="1"/>
      <fsummary>Compute an MD5 message digest.</fsummary>
      <desc>
        <p>Computes an MD5 message digest from <c><anno>Data</anno></c>, where
          the length of the digest is 128 bits (16 bytes).
          <c><anno>Data</anno></c>
          is a binary or a list of small integers and binaries.</p>
        <p>For more information about MD5, see
          <url href="https://www.ietf.org/rfc/rfc1321.txt">
          RFC 1321 - The MD5 Message-Digest Algorithm</url>.</p>
        <warning>
          <p>The MD5 Message-Digest Algorithm is <em>not</em> considered
            safe for code-signing or software-integrity purposes.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="md5_final" arity="1"/>
      <fsummary>Finish the update of an MD5 context and return the computed
        MD5 message digest.</fsummary>
      <desc>
        <p>Finishes the update of an MD5 <c><anno>Context</anno></c> and returns
          the computed <c>MD5</c> message digest.</p>
      </desc>
    </func>

    <func>
      <name name="md5_init" arity="0"/>
      <fsummary>Create an MD5 context.</fsummary>
      <desc>
        <p>Creates an MD5 context, to be used in the following calls to
          <c>md5_update/2</c>.</p>
      </desc>
    </func>

    <func>
      <name name="md5_update" arity="2"/>
      <fsummary>Update an MD5 context with data and return a new context.
      </fsummary>
      <desc>
        <p>Update an MD5 <c><anno>Context</anno></c> with
          <c><anno>Data</anno></c> and returns a
          <c><anno>NewContext</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="memory" arity="0"/>
      <fsummary>Information about dynamically allocated memory.</fsummary>
      <type name="memory_type"/>
      <desc>
        <p>Returns a list with information about memory
          dynamically allocated by the Erlang emulator. Each list
          element is a tuple <c>{Type, Size}</c>. The first element
          <c><anno>Type</anno></c> is an atom describing memory type. The second
          element <c><anno>Size</anno></c> is the memory size in bytes.</p>
        <p>Memory types:</p>
        <taglist>
          <tag><c>total</c></tag>
          <item>
            <p>The total amount of memory currently allocated. This is
              the same as the sum of the memory size for <c>processes</c>
              and <c>system</c>.</p>
          </item>
          <tag><c>processes</c></tag>
          <item>
            <p>The total amount of memory currently allocated for
              the Erlang processes.</p>
          </item>
          <tag><c>processes_used</c></tag>
          <item>
            <p>The total amount of memory currently used by the Erlang
              processes. This is part of the memory presented as
              <c>processes</c> memory.</p>
          </item>
          <tag><c>system</c></tag>
          <item>
            <p>The total amount of memory currently allocated for
              the emulator that is not directly related to any Erlang
              process. Memory presented as <c>processes</c> is not
              included in this memory. <seealso marker="tools:instrument">
              <c>instrument(3)</c></seealso> can be used to
              get a more detailed breakdown of what memory is part
              of this type.</p>
          </item>
          <tag><c>atom</c></tag>
          <item>
            <p>The total amount of memory currently allocated for atoms.
              This memory is part of the memory presented as
              <c>system</c> memory.</p>
          </item>
          <tag><c>atom_used</c></tag>
          <item>
            <p>The total amount of memory currently used for atoms.
              This memory is part of the memory presented as
              <c>atom</c> memory.</p>
          </item>
          <tag><c>binary</c></tag>
          <item>
            <p>The total amount of memory currently allocated for
              binaries. This memory is part of the memory presented
              as <c>system</c> memory.</p>
          </item>
          <tag><c>code</c></tag>
          <item>
            <p>The total amount of memory currently allocated for
              Erlang code. This memory is part of the memory presented
              as <c>system</c> memory.</p>
          </item>
          <tag><c>ets</c></tag>
          <item>
            <p>The total amount of memory currently allocated for ETS
              tables. This memory is part of the memory presented as
              <c>system</c> memory.</p>
          </item>
          <tag><c>low</c></tag>
          <item>
            <p>Only on 64-bit halfword emulator.
              The total amount of memory allocated in low memory areas
              that are restricted to &lt; 4 GB, although
              the system can have more memory.</p>
            <p>Can be removed in a future release of the halfword
              emulator.</p>
          </item>
          <tag><c>maximum</c></tag>
          <item>
            <p>The maximum total amount of memory allocated since
              the emulator was started. This tuple is only present
              when the emulator is run with instrumentation.</p>
            <p>For information on how to run the emulator with
              instrumentation, see
              <seealso marker="tools:instrument">
              <c>instrument(3)</c></seealso>
              and/or <seealso marker="erl"><c>erl(1)</c></seealso>.</p>
          </item>
        </taglist>
        <note>
          <p>The <c>system</c> value is not complete. Some allocated
            memory that is to be part of this value is not.</p>
          <p>When the emulator is run with instrumentation,
            the <c>system</c> value is more accurate, but memory
            directly allocated for <c>malloc</c> (and friends) is still
            not part of the <c>system</c> value. Direct calls to
            <c>malloc</c> are only done from OS-specific runtime
            libraries and perhaps from user-implemented Erlang drivers
            that do not use the memory allocation functions in
            the driver interface.</p>
          <p>As the <c>total</c> value is the sum of <c>processes</c>
            and <c>system</c>, the error in <c>system</c> propagates
            to the <c>total</c> value.</p>
          <p>The different amounts of memory that are summed are
            <em>not</em> gathered atomically, which introduces
            an error in the result.</p>
        </note>
        <p>The different values have the following relation to each
          other. Values beginning with an uppercase letter is not part
          of the result.</p>
        <code type="none">
total      = processes + system
processes  = processes_used + ProcessesNotUsed
system     = atom + binary + code + ets + OtherSystem
atom       = atom_used + AtomNotUsed
RealTotal  = processes + RealSystem
RealSystem = system + MissedSystem</code>
        <p>More tuples in the returned list can be added in a
          future release.</p>
        <note>
          <p>The <c>total</c> value is supposed to be the total amount
            of memory dynamically allocated by the emulator. Shared
            libraries, the code of the emulator itself, and
            the emulator stacks are not supposed to be included. That
            is, the <c>total</c> value is <em>not</em> supposed to be
            equal to the total size of all pages mapped to the emulator.</p>
          <p>Also, because of fragmentation and prereservation of
            memory areas, the size of the memory segments containing
            the dynamically allocated memory blocks can be much
            larger than the total size of the dynamically allocated
            memory blocks.</p>
        </note>
        <note>
          <p>As from ERTS 5.6.4, <c>erlang:memory/0</c> requires that
            all <seealso marker="erts:erts_alloc"><c>erts_alloc(3)</c></seealso>
            allocators are enabled (default behavior).</p>
        </note>
        <p>Failure: <c>notsup</c> if an
          <seealso marker="erts:erts_alloc"><c>erts_alloc(3)</c></seealso>
          allocator has been disabled.</p>
      </desc>
    </func>

    <func>
      <name name="memory" arity="1" clause_i="1"/>
      <name name="memory" arity="1" clause_i="2"/>
      <fsummary>Information about dynamically allocated memory.</fsummary>
      <type name="memory_type"/>
      <desc>
        <p>Returns the memory size in bytes allocated for memory of type
          <c><anno>Type</anno></c>. The argument can also be specified as a list
          of <c>memory_type()</c> atoms, in which case a corresponding list of
          <c>{memory_type(), Size :: integer >= 0}</c> tuples is returned.</p>
        <note>
          <p>As from ERTS 5.6.4,
            <c>erlang:memory/1</c> requires that
            all <seealso marker="erts_alloc"><c>erts_alloc(3)</c></seealso>
            allocators are enabled (default behavior).</p>
        </note>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Type</anno></c> is not one of the memory types
            listed in the description of
            <seealso marker="#memory/0"><c>erlang:memory/0</c></seealso>.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If <c>maximum</c> is passed as <c><anno>Type</anno></c> and
            the emulator is not run in instrumented mode.
          </item>
          <tag><c>notsup</c></tag>
          <item>
            If an <seealso marker="erts_alloc"><c>erts_alloc(3)</c></seealso>
            allocator has been disabled.
          </item>
        </taglist>
        <p>See also
          <seealso marker="#memory/0"><c>erlang:memory/0</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="min" arity="2"/>
      <fsummary>Return the smallest of two terms.</fsummary>
      <desc>
        <p>Returns the smallest of <c><anno>Term1</anno></c> and
          <c><anno>Term2</anno></c>.
          If the terms are equal, <c><anno>Term1</anno></c> is returned.</p>
      </desc>
    </func>

    <func>
      <name name="module_loaded" arity="1"/>
      <fsummary>Check if a module is loaded.</fsummary>
      <desc>
        <p>Returns <c>true</c> if the module <c><anno>Module</anno></c>
          is loaded, otherwise <c>false</c>. It does not attempt to load
          the module.</p>
        <warning>
          <p>This BIF is intended for the code server (see
            <seealso marker="kernel:code"><c>code(3)</c></seealso>)
            and is not to be used elsewhere.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="monitor" arity="2" clause_i="1"/>
      <name name="monitor" arity="2" clause_i="2"/>
      <name name="monitor" arity="2" clause_i="3"/>
      <fsummary>Start monitoring.</fsummary>
      <type name="registered_name"/>
      <type name="registered_process_identifier"/>
      <type name="monitor_process_identifier"/>
      <type name="monitor_port_identifier"/>
      <desc>
	<p>Sends a monitor request of type <c><anno>Type</anno></c> to the
	  entity identified by <c><anno>Item</anno></c>. If the monitored entity
          does not exist or it changes monitored state, the caller of
          <c>monitor/2</c> is notified by a message on the following format:</p>
        <code type="none">
{Tag, <anno>MonitorRef</anno>, <anno>Type</anno>, Object, Info}</code>
	<note>
          <p>The monitor request is an asynchronous signal. That is, it
	    takes time before the signal reaches its destination.</p>
        </note>

        <p><c><anno>Type</anno></c> can be one of the following atoms:
          <c>process</c>, <c>port</c> or <c>time_offset</c>.</p>

        <p>A <c>process</c> or <c>port</c> monitor is triggered only once,
          after that it is removed from both monitoring process and
          the monitored entity. Monitors are fired when the monitored process
          or port terminates, does not exist at the moment of creation,
          or if the connection to it is lost. If the connection to it is lost,
          we do not know if it still exists. The monitoring is also turned off
          when <seealso marker="#demonitor/1">demonitor/1</seealso> is
          called.</p>

        <p>A <c>process</c> or <c>port</c> monitor by name
          resolves the <c>RegisteredName</c> to <c>pid()</c> or <c>port()</c>
          only once at the moment of monitor instantiation, later changes to
          the name registration will not affect the existing monitor.</p>

        <p>When a <c>process</c> or <c>port</c> monitor is triggered,
          a <c>'DOWN'</c> message is sent that has the following pattern:</p>
          <code type="none">
{'DOWN', MonitorRef, Type, Object, Info}</code>

        <p>In the monitor message <c>MonitorRef</c> and <c>Type</c> are the
          same as described earlier, and:</p>
        <taglist>
          <tag><c>Object</c></tag>
          <item>
            <p>The monitored entity, which triggered the event. When monitoring
              a local process or port, <c>Object</c> will be equal to the
              <c>pid()</c> or <c>port()</c> that was being monitored. When
              monitoring process or port by name, <c>Object</c> will have format
              <c>{RegisteredName, Node}</c> where <c>RegisteredName</c> is the
              name which has been used with <c>monitor/2</c> call and
              <c>Node</c> is local or remote node name (for ports monitored by
              name, <c>Node</c> is always local node name).</p>
          </item>
          <tag><c>Info</c></tag>
          <item>
            <p>Either the exit reason of the process, <c>noproc</c>
              (process or port did not exist at the time of monitor creation),
              or <c>noconnection</c> (no connection to the node where the
              monitored process resides). </p></item>
        </taglist>

        <taglist>
        <tag>Monitoring a <marker id="monitor_process"/><c>process</c></tag>
        <item>
          <p>Creates monitor between the current process and another
            process identified by <c><anno>Item</anno></c>, which can be a
            <c>pid()</c> (local or remote), an atom <c>RegisteredName</c> or
            a tuple <c>{RegisteredName, Node}</c> for a registered process,
          located elsewhere.</p>

        <note><p>Before ERTS 10.0 (OTP 21.0), monitoring a process could fail with
	  <c>badarg</c> if the monitored process resided on a primitive node
	  (such as erl_interface or jinterface), where remote process monitoring
	  is not implemented.</p>
	  <p>Now, such a call to <c>monitor</c> will instead succeed and a
	  monitor is created. But the monitor will only supervise the
	  connection. That is, a <c>{'DOWN', _, process, _, noconnection}</c> is
	  the only message that may be received, as the primitive node have no
	  way of reporting the status of the monitored process.</p>
	</note>

        </item>

        <tag>Monitoring a <marker id="monitor_port"/><c>port</c></tag>
        <item>
          <p>Creates monitor between the current process and a port
            identified by <c><anno>Item</anno></c>, which can be a
            <c>port()</c> (only local), an atom <c>RegisteredName</c> or
            a tuple <c>{RegisteredName, Node}</c> for a registered port,
            located on this node. Note, that attempt to monitor a remote port
            will result in <c>badarg</c>.</p>
        </item>

        <tag>Monitoring a
          <marker id="monitor_time_offset"/><c>time_offset</c></tag>
	  <item>
	    <p>Monitors changes in
	      <seealso marker="#time_offset/0"><c>time offset</c></seealso>
	      between
	      <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
	      monotonic time</seealso> and
	      <seealso marker="time_correction#Erlang_System_Time">Erlang
	      system time</seealso>. One valid <c><anno>Item</anno></c>
              exists in combination with the
	      <c>time_offset <anno>Type</anno></c>, namely the atom
	      <c>clock_service</c>. Notice that the atom <c>clock_service</c> is
	      <em>not</em> the registered name of a process. In this
	      case it serves as an identifier of the runtime system internal
	      clock service at current runtime system instance.</p>

	    <p>The monitor is triggered when the time offset is changed.
	      This either if the time offset value is changed, or if the
	      offset is changed from preliminary to final during
	      <seealso marker="#system_flag_time_offset">finalization
	      of the time offset</seealso> when the
	      <seealso marker="time_correction#Single_Time_Warp_Mode">single
	      time warp mode</seealso> is used. When a change from preliminary
	      to final time offset is made, the monitor is triggered once
	      regardless of whether the time offset value was changed
	      or not.</p>

	    <p>If the runtime system is in
	      <seealso marker="time_correction#Multi_Time_Warp_Mode">multi
	      time warp mode</seealso>, the time offset is changed when
	      the runtime system detects that the
	      <seealso marker="time_correction#OS_System_Time">OS system
	      time</seealso> has changed. The runtime system does, however,
	      not detect this immediately when it occurs. A task checking
	      the time offset is scheduled to execute at least once a minute,
	      so under normal operation this is to be detected within a
	      minute, but during heavy load it can take longer time.</p>

	    <p>The monitor is <em>not</em> automatically removed
	      after it has been triggered. That is, repeated changes of
	      the time offset trigger the monitor repeatedly.</p>

            <p>When the monitor is triggered a <c>'CHANGE'</c> message is
	      sent to the monitoring process. A <c>'CHANGE'</c> message has
	      the following pattern:</p>
              <code type="none">
{'CHANGE', MonitorRef, Type, Item, NewTimeOffset}</code>
              <p>where <c>MonitorRef</c>, <c><anno>Type</anno></c>, and
	      <c><anno>Item</anno></c> are the same as described above, and
	      <c>NewTimeOffset</c> is the new time offset.</p>

	    <p>When the <c>'CHANGE'</c> message has been received you are
	      guaranteed not to retrieve the old time offset when calling
	      <seealso marker="#time_offset/0">
              <c>erlang:time_offset()</c></seealso>.
	      Notice that you can observe the change of the time offset
	      when calling <c>erlang:time_offset()</c> before you
	      get the <c>'CHANGE'</c> message.</p>
	  </item>
	</taglist>

	<p>Making several calls to <c>monitor/2</c> for the same
	  <c><anno>Item</anno></c> and/or <c><anno>Type</anno></c> is not
	  an error; it results in as many independent monitoring instances.</p>

	<p>The monitor functionality is expected to be extended. That is,
	  other <c><anno>Type</anno></c>s and <c><anno>Item</anno></c>s
	  are expected to be supported in a future release.</p>
        <note>
          <p>If or when <c>monitor/2</c> is extended, other
            possible values for <c>Tag</c>, <c>Object</c>, and
            <c>Info</c> in the monitor message will be introduced.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="monitor_node" arity="2"/>
      <fsummary>Monitor the status of a node.</fsummary>
      <desc>
        <p>Monitor the status of the node <c><anno>Node</anno></c>.
          If <c><anno>Flag</anno></c>
          is <c>true</c>, monitoring is turned on. If <c><anno>Flag</anno></c>
          is <c>false</c>, monitoring is turned off.</p>
        <p>Making several calls to <c>monitor_node(Node, true)</c> for
          the same <c><anno>Node</anno></c> is not an error; it results
          in as many independent monitoring instances.</p>
        <p>If <c><anno>Node</anno></c> fails or does not exist, the message
          <c>{nodedown, Node}</c> is delivered to the process. If a
          process has made two calls to <c>monitor_node(Node, true)</c>
          and <c><anno>Node</anno></c> terminates, two <c>nodedown</c> messages
          are delivered to the process. If there is no connection to
          <c><anno>Node</anno></c>, an attempt is made to create one.
          If this fails, a <c>nodedown</c> message is delivered.</p>
        <p>Nodes connected through hidden connections can be monitored
          as any other nodes.</p>
        <p>Failure: <c>badarg</c> if the local node is not alive.</p>
      </desc>
    </func>

    <func>
      <name name="monitor_node" arity="3"/>
      <fsummary>Monitor the status of a node.</fsummary>
      <desc>
        <p>Behaves as
          <seealso marker="#monitor_node/2"><c>monitor_node/2</c></seealso>
          except that it allows an
          extra option to be specified, namely <c>allow_passive_connect</c>.
          This option allows the BIF to wait the normal network connection
          time-out for the <em>monitored node</em> to connect itself,
          even if it cannot be actively connected from this node
          (that is, it is blocked). The state where this can be useful
          can only be achieved by using the Kernel option
          <c>dist_auto_connect once</c>. If that option is not
          used, option <c>allow_passive_connect</c> has no effect.</p>
        <note>
          <p>Option <c>allow_passive_connect</c> is used
            internally and is seldom needed in applications where the
            network topology and the Kernel options in effect
            are known in advance.</p>
        </note>
        <p>Failure: <c>badarg</c> if the local node is not alive or the
          option list is malformed.</p>
      </desc>
    </func>

    <func>
      <name name="monotonic_time" arity="0"/>
      <fsummary>Current Erlang monotonic time.</fsummary>
      <desc>
        <p>Returns the current
          <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
          monotonic time</seealso> in <c>native</c>
          <seealso marker="#type_time_unit">time unit</seealso>. This
          is a monotonically increasing time since some unspecified point in
          time.</p>
        <note>
          <p>This is a
            <seealso marker="time_correction#Monotonically_Increasing">
            monotonically increasing</seealso> time, but <em>not</em> a
            <seealso marker="time_correction#Strictly_Monotonically_Increasing">
            strictly monotonically increasing</seealso>
            time. That is, consecutive calls to
            <c>erlang:monotonic_time/0</c> can produce the same result.</p>
          <p>Different runtime system instances will use different unspecified
            points in time as base for their Erlang monotonic clocks.
            That is, it is <em>pointless</em> comparing monotonic times from
            different runtime system instances. Different runtime system
            instances can also place this unspecified point in time different
            relative runtime system start. It can be placed in the future (time
            at start is a negative value), the past (time at start is a
            positive value), or the runtime system start (time at start is
            zero). The monotonic time at runtime system start can be
            retrieved by calling
            <seealso marker="#system_info_start_time">
            <c>erlang:system_info(start_time)</c></seealso>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="monotonic_time" arity="1"/>
      <fsummary>Current Erlang monotonic time.</fsummary>
      <desc>
        <p>Returns the current
          <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
          monotonic time</seealso> converted
          into the <c><anno>Unit</anno></c> passed as argument.</p>
        <p>Same as calling
          <seealso marker="#convert_time_unit/3">
          <c>erlang:convert_time_unit</c></seealso><c>(</c><seealso
          marker="#monotonic_time/0">
          <c>erlang:monotonic_time()</c></seealso><c>,
          native, <anno>Unit</anno>)</c>,
          however optimized for commonly used <c><anno>Unit</anno></c>s.</p>
      </desc>
    </func>

    <func>
      <name name="nif_error" arity="1"/>
      <fsummary>Stop execution with a specified reason.</fsummary>
      <desc>
        <p>Works exactly like
         <seealso marker="#error/1"><c>error/1</c></seealso>, but
         Dialyzer thinks that this BIF will return an arbitrary
         term. When used in a stub function for a NIF to generate an
         exception when the NIF library is not loaded, Dialyzer
         does not generate false warnings.</p>
      </desc>
    </func>

    <func>
      <name name="nif_error" arity="2"/>
      <fsummary>Stop execution with a specified reason.</fsummary>
      <desc>
        <p>Works exactly like
          <seealso marker="#error/2"><c>error/2</c></seealso>, but
          Dialyzer thinks that this BIF will return an arbitrary
          term. When used in a stub function for a NIF to generate an
          exception when the NIF library is not loaded, Dialyzer
          does not generate false warnings.</p>
      </desc>
    </func>

    <func>
      <name name="node" arity="0"/>
      <fsummary>Name of the local node.</fsummary>
      <desc>
        <p>Returns the name of the local node. If the node is not alive,
          <c>nonode@nohost</c> is returned instead.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="node" arity="1"/>
      <fsummary>At which node a pid, port, or reference originates.</fsummary>
      <desc>
        <p>Returns the node where <c><anno>Arg</anno></c> originates.
          <c><anno>Arg</anno></c> can
          be a process identifier, a reference, or a port.
          If the local node is not
          alive, <c>nonode@nohost</c> is returned.</p>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="nodes" arity="0"/>
      <fsummary>All visible nodes in the system.</fsummary>
      <desc>
        <p>Returns a list of all visible nodes in the system, except
          the local node. Same as <c>nodes(visible)</c>.</p>
      </desc>
    </func>

    <func>
      <name name="nodes" arity="1"/>
      <fsummary>All nodes of a certain type in the system.</fsummary>
      <desc>
        <p>Returns a list of nodes according to the argument specified.
          The returned result, when the argument is a list, is the list
          of nodes satisfying the disjunction(s) of the list elements.</p>
        <p><c><anno>NodeType</anno></c>s:</p>
        <taglist>
          <tag><c>visible</c></tag>
          <item>
            <p>Nodes connected to this node through normal connections.</p>
          </item>
          <tag><c>hidden</c></tag>
          <item>
            <p>Nodes connected to this node through hidden connections.</p>
          </item>
          <tag><c>connected</c></tag>
          <item>
            <p>All nodes connected to this node.</p>
          </item>
          <tag><c>this</c></tag>
          <item>
            <p>This node.</p>
          </item>
          <tag><c>known</c></tag>
          <item>
            <p>Nodes that are known to this node. That is, connected
              nodes and nodes referred to by process identifiers, port
              identifiers, and references located on this node.
              The set of known nodes is garbage collected. Notice that
              this garbage collection can be delayed. For more
              information, see
              <seealso marker="erlang#system_info_delayed_node_table_gc">
              <c>erlang:system_info(delayed_node_table_gc)</c></seealso>.</p>
          </item>
        </taglist>
        <p>Some equalities: <c>[node()] = nodes(this)</c>,
          <c>nodes(connected) = nodes([visible, hidden])</c>, and
          <c>nodes() = nodes(visible)</c>.</p>
      </desc>
    </func>

    <func>
      <name name="now" arity="0"/>
      <fsummary>Elapsed time since 00:00 GMT.</fsummary>
      <type name="timestamp"/>
      <desc>
        <warning>
          <p><em>This function is deprecated. Do not use it.</em></p>
          <p>For more information, see section
            <seealso marker="time_correction">Time and Time Correction</seealso>
            in the User's Guide. Specifically, section
            <seealso marker="time_correction#Dos_and_Donts">
            Dos and Dont's</seealso> describes what to use instead of
            <c>erlang:now/0</c>.</p>
        </warning>
        <p>Returns the tuple <c>{MegaSecs, Secs, MicroSecs}</c>, which is
          the elapsed time since 00:00 GMT, January 1, 1970 (zero hour),
          if provided by the underlying OS.
          Otherwise some other point in time is chosen. It is also
          guaranteed that the following calls to this BIF return
          continuously increasing values. Hence, the return value from
          <c>erlang:now/0</c> can be used to generate unique time stamps.
          If it is called in a tight loop on a fast machine,
          the time of the node can become skewed.</p>
        <p>Can only be used to check the local time of day if
          the time-zone information of the underlying OS is
          properly configured.</p>
      </desc>
    </func>

    <func>
      <name name="open_port" arity="2"/>
      <fsummary>Open a port.</fsummary>
      <desc>
        <p>Returns a port identifier as the result of opening a
          new Erlang port. A port can be seen as an external Erlang
          process.</p>
        <p>The name of the executable as well as the arguments
          specifed in <c>cd</c>, <c>env</c>, <c>args</c>, and <c>arg0</c> are
          subject to Unicode filename translation if the system is running
          in Unicode filename mode. To avoid
          translation or to force, for example UTF-8, supply the executable
          and/or arguments as a binary in the correct
          encoding. For details, see the module
          <seealso marker="kernel:file"><c>file(3)</c></seealso>, the
          function <seealso marker="kernel:file#native_name_encoding/0">
          <c>file:native_name_encoding/0</c></seealso> in Kernel, and
          the <seealso marker="stdlib:unicode_usage">
          <c>Using Unicode in Erlang</c></seealso> User's Guide.</p>
        <note>
          <p>The characters in the name (if specified as a list) can
            only be &gt; 255 if the Erlang virtual machine is started
            in Unicode filename translation mode. Otherwise the name
            of the executable is limited to the ISO Latin-1
            character set.</p>
        </note>
	<p><c><anno>PortName</anno></c>s:</p>
        <taglist>
          <tag><c>{spawn, <anno>Command</anno>}</c></tag>
          <item>
            <p>Starts an external program. <c><anno>Command</anno></c>
              is the name of the external program to be run.
              <c><anno>Command</anno></c>
              runs outside the Erlang work space unless an Erlang
              driver with the name <c><anno>Command</anno></c> is found.
              If found, that driver is started. A driver runs in the Erlang
              work space, which means that it is linked with the Erlang
              runtime system.</p>
            <p>When starting external programs on Solaris, the system
              call <c>vfork</c> is used in preference to <c>fork</c>
              for performance reasons, although it has a history of
              being less robust. If there are problems using
              <c>vfork</c>, setting environment variable
              <c>ERL_NO_VFORK</c> to any value causes <c>fork</c>
              to be used instead.</p>
            <p>For external programs, <c>PATH</c> is searched
              (or an equivalent method is used to find programs,
              depending on the OS). This is done by invoking
              the shell on certain platforms. The first space-separated
              token of the command is considered as the
              name of the executable (or driver). This (among other
              things) makes this option unsuitable for running
              programs with spaces in filenames or directory names.
              If spaces in executable filenames are desired, use
              <c>{spawn_executable, <anno>Command</anno>}</c> instead.</p>
          </item>
          <tag><c>{spawn_driver, <anno>Command</anno>}</c></tag>
          <item>
            <p>Works like <c>{spawn, <anno>Command</anno>}</c>, but demands
              the first (space-separated) token of the command to be the name
              of a loaded driver. If no driver with that name is loaded, a
              <c>badarg</c> error is raised.</p>
          </item>
          <tag><c>{spawn_executable, <anno>FileName</anno>}</c></tag>
          <item>
            <p>Works like <c>{spawn, <anno>FileName</anno>}</c>, but only runs
              external executables. <c><anno>FileName</anno></c> in its whole
              is used as the name of the executable, including any spaces.
              If arguments are to be passed, the
              <c><anno>PortSettings</anno></c>
              <c>args</c> and <c>arg0</c> can be used.</p>
            <p>The shell is usually not invoked to start the
              program, it is executed directly. <c>PATH</c> (or
              equivalent) is not searched. To find a program
              in <c>PATH</c> to execute, use
              <seealso marker="kernel:os#find_executable/1">
              <c>os:find_executable/1</c></seealso>.</p>
            <p>Only if a shell script or <c>.bat</c> file is
              executed, the appropriate command interpreter is
              invoked implicitly, but there is still no
              command-argument expansion or implicit <c>PATH</c> search.</p>
            <p>If <c><anno>FileName</anno></c> cannot be run, an error
              exception is raised, with the POSIX error code as the reason.
              The error reason can differ between OSs.
              Typically the error <c>enoent</c> is raised when an
              attempt is made to run a program that is not found and
              <c>eacces</c> is raised when the specified file is not
              executable.</p>
          </item>
          <tag><c>{fd, <anno>In</anno>, <anno>Out</anno>}</c></tag>
          <item>
            <p>Allows an Erlang process to access any currently opened
              file descriptors used by Erlang. The file descriptor
              <c><anno>In</anno></c> can be used for standard input, and the
              file descriptor <c><anno>Out</anno></c> for standard output.
              It is only used for various servers in the Erlang OS (<c>shell</c>
              and <c>user</c>). Hence, its use is limited.</p>
          </item>
        </taglist>
        <p><c><anno>PortSettings</anno></c> is a list of settings for the port.
          The valid settings are as follows:</p>
        <taglist>
          <tag><c>{packet, <anno>N</anno>}</c></tag>
          <item>
            <p>Messages are preceded by their length, sent in
              <c><anno>N</anno></c>
              bytes, with the most significant byte first. The valid values
              for <c>N</c> are 1, 2, and 4.</p>
          </item>
          <tag><c>stream</c></tag>
          <item>
            <p>Output messages are sent without packet lengths. A
              user-defined protocol must be used between the Erlang
              process and the external object.</p>
          </item>
          <tag><c>{line, <anno>L</anno>}</c></tag>
          <item>
            <p>Messages are delivered on a per line basis. Each line
              (delimited by the OS-dependent newline sequence) is
              delivered in a single message. The message data format
              is <c>{Flag, Line}</c>, where <c>Flag</c> is
              <c>eol</c> or <c>noeol</c>, and <c>Line</c> is the
              data delivered (without the newline sequence).</p>
            <p><c><anno>L</anno></c> specifies the maximum line length in bytes.
              Lines longer than this are delivered in more than one
              message, with <c>Flag</c> set to <c>noeol</c> for all
              but the last message. If end of file is encountered
              anywhere else than immediately following a newline
              sequence, the last line is also delivered with
              <c>Flag</c> set to <c>noeol</c>. Otherwise
              lines are delivered with <c>Flag</c> set to <c>eol</c>.</p>
            <p>The <c>{packet, <anno>N</anno>}</c> and <c>{line,
              <anno>L</anno>}</c> settings are mutually exclusive.</p>
          </item>
          <tag><c>{cd, <anno>Dir</anno>}</c></tag>
          <item>
            <p>Only valid for <c>{spawn, <anno>Command</anno>}</c> and
              <c>{spawn_executable, <anno>FileName</anno>}</c>.
              The external program starts using <c><anno>Dir</anno></c> as its
              working directory. <c><anno>Dir</anno></c> must be a string.</p>
          </item>
          <tag><c>{env, <anno>Env</anno>}</c></tag>
          <item>
	    <p>
	      Types:<br/>
	      &nbsp;&nbsp;<c><anno>Name</anno> = </c><seealso marker="kernel:os#type-env_var_name"><c>os:env_var_name()</c></seealso><br/>
	      &nbsp;&nbsp;<c><anno>Val</anno> = </c><seealso marker="kernel:os#type-env_var_value"><c>os:env_var_value()</c></seealso><c> | false</c><br/>
	      &nbsp;&nbsp;<c>Env = [{<anno>Name</anno>, <anno>Val</anno>}]</c>
	    </p>
            <p>Only valid for <c>{spawn, <anno>Command</anno>}</c>, and
              <c>{spawn_executable, <anno>FileName</anno>}</c>.
              The environment of the started process is extended using
              the environment specifications in <c><anno>Env</anno></c>.</p>
            <p><c><anno>Env</anno></c> is to be a list of tuples
              <c>{<anno>Name</anno>, <anno>Val</anno>}</c>,
              where <c><anno>Name</anno></c> is the name of an
              environment variable, and <c><anno>Val</anno></c> is the
              value it is to have in the spawned
              port process. Both <c><anno>Name</anno></c> and
              <c><anno>Val</anno></c> must be strings. The one
              exception is <c><anno>Val</anno></c> being the atom
              <c>false</c> (in analogy with
              <seealso marker="kernel:os#getenv/1"><c>os:getenv/1</c></seealso>,
              which removes the environment variable.
	    </p>
	    <p>
	      For information about encoding requirements, see documentation
	      of the types for <c><anno>Name</anno></c> and
	      <c><anno>Val</anno></c>.
	    </p>
          </item>
          <tag><c>{args, [ string() | binary() ]}</c></tag>
          <item>
            <p>Only valid for <c>{spawn_executable, <anno>FileName</anno>}</c>
              and specifies arguments to the executable. Each argument
              is specified as a separate string and (on Unix) eventually
              ends up as one element each in the argument vector. On
              other platforms, a similar behavior is mimicked.</p>
            <p>The arguments are not expanded by the shell before
              they are supplied to the executable. Most notably this
              means that file wildcard expansion does not occur.
              To expand wildcards for the arguments, use
              <seealso marker="stdlib:filelib#wildcard/1">
              <c>filelib:wildcard/1</c></seealso>.
              Notice that even if
              the program is a Unix shell script, meaning that the
              shell ultimately is invoked, wildcard expansion
              does not occur, and the script is provided with the
              untouched arguments. On Windows, wildcard expansion
              is always up to the program itself, therefore this is
              not an issue.</p>
            <p>The executable name (also known as <c>argv[0]</c>)
              is not to be specified in this list. The proper executable name
              is automatically used as <c>argv[0]</c>, where applicable.</p>
            <p>If you explicitly want to set the
              program name in the argument vector, option <c>arg0</c>
              can be used.</p>
          </item>
          <tag><c>{arg0, string() | binary()}</c></tag>
          <item>
            <p>Only valid for <c>{spawn_executable, <anno>FileName</anno>}</c>
              and explicitly specifies the program name argument when
              running an executable. This can in some circumstances,
              on some OSs, be desirable. How the program
              responds to this is highly system-dependent and no specific
              effect is guaranteed.</p>
          </item> 
          <tag><c>exit_status</c></tag>
          <item>
            <p>Only valid for <c>{spawn, <anno>Command</anno>}</c>, where
              <c><anno>Command</anno></c> refers to an external program, and
              for <c>{spawn_executable, <anno>FileName</anno>}</c>.</p>
            <p>When the external process connected to the port exits, a
              message of the form <c>{Port,{exit_status,Status}}</c> is
              sent to the connected process, where <c>Status</c> is the
              exit status of the external process. If the program
              aborts on Unix, the same convention is used as the shells
              do (that is, 128+signal).</p>
            <p>If option <c>eof</c> is specified also, the messages <c>eof</c>
              and <c>exit_status</c> appear in an unspecified order.</p>
            <p>If the port program closes its <c>stdout</c> without exiting,
              option <c>exit_status</c> does not work.</p>
          </item>
          <tag><c>use_stdio</c></tag>
          <item>
            <p>Only valid for <c>{spawn, <anno>Command</anno>}</c> and
              <c>{spawn_executable, <anno>FileName</anno>}</c>. It
              allows the standard input and output (file descriptors 0
              and 1) of the spawned (Unix) process for communication
              with Erlang.</p>
          </item>
          <tag><c>nouse_stdio</c></tag>
          <item>
            <p>The opposite of <c>use_stdio</c>. It uses file descriptors
              3 and 4 for communication with Erlang.</p>
          </item>
          <tag><c>stderr_to_stdout</c></tag>
          <item>
            <p>Affects ports to external programs. The executed program
              gets its standard error file redirected to its standard
              output file. <c>stderr_to_stdout</c> and
              <c>nouse_stdio</c> are mutually exclusive.</p>
          </item>
          <tag><c>overlapped_io</c></tag>
          <item>
            <p>Affects ports to external programs on Windows only. The
              standard input and standard output handles of the port program
              are, if this option is supplied, opened with flag
              <c>FILE_FLAG_OVERLAPPED</c>, so that the port program can
              (and must) do
              overlapped I/O on its standard handles. This is not normally
              the case for simple port programs, but an option of value for the
              experienced Windows programmer. <em>On all other platforms, this
              option is silently discarded.</em></p>
          </item>
          <tag><c>in</c></tag>
          <item>
            <p>The port can only be used for input.</p>
          </item>
          <tag><c>out</c></tag>
          <item>
            <p>The port can only be used for output.</p>
          </item>
          <tag><c>binary</c></tag>
          <item>
            <p>All I/O from the port is binary data objects as opposed
              to lists of bytes.</p>
          </item>
          <tag><c>eof</c></tag>
          <item>
            <p>The port is not closed at the end of the file and does not
              produce an exit signal. Instead, it remains open and
              a <c>{Port, eof}</c> message is sent to the process
              holding the port.</p>
          </item>
          <tag><c>hide</c></tag>
          <item>
            <p>When running on Windows, suppresses creation of a new
              console window when spawning the port program.
              (This option has no effect on other platforms.)</p>
          </item>
          <tag><c>{parallelism, Boolean}</c></tag>
          <item>
            <marker id="open_port_parallelism"></marker>
            <p>Sets scheduler hint for port parallelism. If set to
              <c>true</c>, the virtual machine schedules port tasks;
              when doing so, it improves parallelism in the system. If set
              to <c>false</c>, the virtual machine tries to
              perform port tasks immediately, improving latency at the
              expense of parallelism. The default can be set at system startup
              by passing command-line argument
              <seealso marker="erl#+spp"><c>+spp</c></seealso> to
              <c>erl(1)</c>.</p>
          </item>
        </taglist>
        <p>Default is <c>stream</c> for all port types and
          <c>use_stdio</c> for spawned ports.</p>
        <p>Failure: if the port cannot be opened, the exit reason is
          <c>badarg</c>, <c>system_limit</c>, or the POSIX error code that
          most closely describes the error, or <c>einval</c> if no POSIX
          code is appropriate:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>Bad input arguments to <c>open_port</c>.
          </item>
          <tag><c>system_limit</c></tag>
          <item>All available ports in the Erlang emulator are in use.
          </item>
          <tag><c>enomem</c></tag>
          <item>Not enough memory to create the port.
          </item>
          <tag><c>eagain</c></tag>
          <item>No more available OS processes.
          </item>
          <tag><c>enametoolong</c></tag>
          <item>Too long external command.
          </item>
          <tag><c>emfile</c></tag>
          <item>No more available file descriptors (for the
            OS process that the Erlang emulator runs in).
          </item>
          <tag><c>enfile</c></tag>
          <item>Full file table (for the entire OS).
          </item>
          <tag><c>eacces</c></tag>
          <item><c>Command</c> specified in <c>{spawn_executable, Command}</c>
            does not point out an executable file.
          </item>
          <tag><c>enoent</c></tag>
          <item><c><anno>FileName</anno></c> specified in
            <c>{spawn_executable, <anno>FileName</anno>}</c>
            does not point out an existing file.
          </item>
        </taglist>
        <p>During use of a port opened using <c>{spawn, Name}</c>,
          <c>{spawn_driver, Name}</c>, or <c>{spawn_executable, Name}</c>,
          errors arising when sending messages to it are reported to
          the owning process using signals of the form
          <c>{'EXIT', Port, PosixCode}</c>. For the possible values of
          <c>PosixCode</c>, see
          <seealso marker="kernel:file"><c>file(3)</c></seealso>.</p>
        <p>The maximum number of ports that can be open at the same
          time can be configured by passing command-line flag
          <seealso marker="erl#max_ports"><c>+Q</c></seealso> to
          <c>erl(1)</c>.</p>
      </desc>
    </func>

    <func>
      <name name="phash" arity="2"/>
      <fsummary>Portable hash function.</fsummary>
      <type_desc variable="Range">Range = 1..2^32, Hash = 1..Range</type_desc>
      <desc>
        <p>Portable hash function that gives the same hash for
          the same Erlang term regardless of machine architecture and
          ERTS version (the BIF was introduced in ERTS 4.9.1.1).
          The function returns a hash value for
          <c><anno>Term</anno></c> within the range
          <c>1..<anno>Range</anno></c>. The maximum value for
          <c><anno>Range</anno></c> is 2^32.</p>
      </desc>
    </func>

    <func>
      <name name="phash2" arity="1"/>
      <name name="phash2" arity="2"/>
      <fsummary>Portable hash function.</fsummary>
      <type_desc variable="Range">1..2^32</type_desc>
      <type_desc variable="Hash">0..Range-1</type_desc>
      <desc>
        <p>Portable hash function that gives the same hash for
          the same Erlang term regardless of machine architecture and
          ERTS version (the BIF was introduced in ERTS 5.2).
          The function returns a hash value for
          <c><anno>Term</anno></c> within the range
          <c>0..<anno>Range</anno>-1</c>. The maximum value for
          <c><anno>Range</anno></c> is 2^32. When without argument
          <c><anno>Range</anno></c>, a value in the range
          0..2^27-1 is returned.</p>
        <p>This BIF is always to be used for hashing terms. It
          distributes small integers better than <c>phash/2</c>, and
          it is faster for bignums and binaries.</p>
        <p>Notice that the range <c>0..<anno>Range</anno>-1</c> is
          different from the range of <c>phash/2</c>, which is
          <c>1..<anno>Range</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="pid_to_list" arity="1"/>
      <fsummary>Text representation of a pid.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of <c><anno>Pid</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="port_call" arity="3"/>
      <fsummary>Perform a synchronous call to a port with term data.</fsummary>
      <desc>
        <p>Performs a synchronous call to a port. The meaning of
          <c><anno>Operation</anno></c> and <c><anno>Data</anno></c>
          depends on the port, that is,
          on the port driver. Not all port drivers support this feature.</p>
        <p><c><anno>Port</anno></c> is a port identifier,
          referring to a driver.</p>
        <p><c><anno>Operation</anno></c> is an integer, which is passed on to
          the driver.</p>
        <p><c><anno>Data</anno></c> is any Erlang term. This data is converted
          to binary term format and sent to the port.</p>
        <p>Returns a term from the driver. The meaning of the returned
          data also depends on the port driver.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Port</anno></c> is not an identifier of an open port,
            or the registered name of an open port. If the calling
            process was previously linked to the closed port,
            identified by <c><anno>Port</anno></c>, the exit signal
            from the port is guaranteed to be delivered before this
            <c>badarg</c> exception occurs.
            </item>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Operation</anno></c> does not fit in a 32-bit integer.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the port driver does not support synchronous control operations.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the port driver so decides for any reason (probably
            something wrong with <c><anno>Operation</anno></c>
            or <c><anno>Data</anno></c>).
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="port_close" arity="1"/>
      <fsummary>Close an open port.</fsummary>
      <desc>
        <p>Closes an open port. Roughly the same as <c><anno>Port</anno> !
          {self(), close}</c> except for the error behavior
          (see below), being synchronous, and that the port does
          <em>not</em> reply with <c>{Port, closed}</c>. Any process can
          close a port with <c>port_close/1</c>, not only the port owner
          (the connected process). If the calling process is linked to
          the port identified by <c><anno>Port</anno></c>, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_close/1</c> returns.</p> 
        <p>For comparison: <c><anno>Port</anno> ! {self(), close}</c>
          only fails with <c>badarg</c> if <c><anno>Port</anno></c> does
          not refer to a port or a process. If <c><anno>Port</anno></c>
          is a closed port, nothing happens. If <c><anno>Port</anno></c>
          is an open port and the calling process is the port owner,
          the port replies with <c>{Port, closed}</c> when all buffers
          have been flushed and the port really closes. If the calling
          process is not the port owner, the <em>port owner</em> fails
          with <c>badsig</c>.</p> 
        <p>Notice that any process can close a port using
          <c><anno>Port</anno> ! {PortOwner, close}</c> as if it itself was
          the port owner, but the reply always goes to the port owner.</p>
        <p>As from Erlang/OTP R16,
          <c><anno>Port</anno> ! {PortOwner, close}</c> is truly
          asynchronous. Notice that this operation has always been
          documented as an asynchronous operation, while the underlying
          implementation has been synchronous. <c>port_close/1</c> is
          however still fully synchronous because of its error behavior.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an
          identifier of an open port, or the registered name of an open port.
          If the calling process was previously linked to the closed
          port, identified by <c><anno>Port</anno></c>, the exit
          signal from the port is guaranteed to be delivered before
          this <c>badarg</c> exception occurs.</p>
      </desc>
    </func>

    <func>
      <name name="port_command" arity="2"/>
      <fsummary>Send data to a port.</fsummary>
      <desc>
        <p>Sends data to a port. Same as
          <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> except for
          the error behavior and being synchronous (see below). Any process
          can send data to a port with <c>port_command/2</c>, not only the
          port owner (the connected process).</p>
        <p>For comparison: <c><anno>Port</anno> ! {PortOwner, {command,
          Data}}</c> only fails with <c>badarg</c> if <c><anno>Port</anno></c>
          does not refer to a port or a process. If <c><anno>Port</anno></c> is
          a closed port, the data message disappears 
          without a sound. If <c><anno>Port</anno></c> is open and the calling
          process is not the port owner, the <em>port owner</em> fails
          with <c>badsig</c>. The port owner fails with <c>badsig</c>
          also if <c><anno>Data</anno></c> is an invalid I/O list.</p>
        <p>Notice that any process can send to a port using
          <c><anno>Port</anno> ! {PortOwner, {command, <anno>Data</anno>}}</c>
          as if it itself was the port owner.</p>
        <p>If the port is busy, the calling process is suspended
          until the port is not busy any more.</p>
        <p>As from Erlang/OTP R16,
          <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c>
          is truly asynchronous. Notice that this operation has always been
          documented as an asynchronous operation, while the underlying
          implementation has been synchronous. <c>port_command/2</c> is
          however still fully synchronous because of its error behavior.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            <p>If <c><anno>Port</anno></c> is not an identifier of an open
              port, or the registered name of an open port. If the
              calling process was previously linked to the closed port,
              identified by <c><anno>Port</anno></c>, the exit signal
              from the port is guaranteed to be delivered before this
              <c>badarg</c> exception occurs.</p>
          </item>
          <tag><c>badarg</c></tag>
          <item>
            <p>If <c><anno>Data</anno></c> is an invalid I/O list.</p>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="port_command" arity="3"/>
      <fsummary>Send data to a port.</fsummary>
      <desc>
        <p>Sends data to a port. <c>port_command(Port, Data, [])</c>
          equals <c>port_command(Port, Data)</c>.</p>
        <p>If the port command is aborted, <c>false</c> is returned,
          otherwise <c>true</c>.</p>
        <p>If the port is busy, the calling process is suspended
          until the port is not busy anymore.</p>
        <p><c><anno>Option</anno></c>s:</p>
        <taglist>
          <tag><c>force</c></tag>
          <item>The calling process is not suspended if the port is
            busy, instead the port command is forced through. The
            call fails with a <c>notsup</c> exception if the
            driver of the port does not support this. For more
            information, see driver flag
            <seealso marker="driver_entry#driver_flags">
            <c>![CDATA[ERL_DRV_FLAG_SOFT_BUSY]]</c></seealso>.
          </item>
          <tag><c>nosuspend</c></tag>
          <item>The calling process is not suspended if the port is
            busy, instead the port command is aborted and
            <c>false</c> is returned. 
          </item>
        </taglist>
        <note>
          <p>More options can be added in a future release.</p>
        </note>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Port</anno></c> is not an identifier of an open
            port, or the registered name of an open port. If the
            calling process was previously linked to the closed port,
            identified by <c><anno>Port</anno></c>, the exit signal
            from the port is guaranteed to be delivered before this
            <c>badarg</c> exception occurs.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Data</anno></c> is an invalid I/O list.
          </item>
          <tag><c>badarg</c></tag>
          <item>
          If <c><anno>OptionList</anno></c> is an invalid option list.
          </item>
          <tag><c>notsup</c></tag>
          <item>
            If option <c>force</c> has been passed, but the
            driver of the port does not allow forcing through
            a busy port.
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="port_connect" arity="2"/>
      <fsummary>Set the owner of a port.</fsummary>
      <desc>
        <p>Sets the port owner (the connected port) to <c><anno>Pid</anno></c>.
          Roughly the same as
          <c><anno>Port</anno> ! {Owner, {connect, <anno>Pid</anno>}}</c>
          except for the following:</p>
        <list type="bulleted">
          <item>
            <p>The error behavior differs, see below.</p>
          </item>
          <item>
            <p>The port does <em>not</em> reply with
              <c>{Port,connected}</c>.</p>
          </item>
          <item>
            <p><c>port_connect/1</c> is synchronous, see below.</p>
          </item>
          <item>
            <p>The new port owner gets linked to the port.</p>
          </item>
        </list>
        <p>The old port owner stays linked to the port and must call
          <c>unlink(Port)</c> if this is not desired. Any process can
          set the port owner to be any process with
          <c>port_connect/2</c>.</p>
        <p>For comparison:
          <c><anno>Port</anno> ! {self(), {connect, <anno>Pid</anno>}}</c>
          only fails with <c>badarg</c> if <c><anno>Port</anno></c>
          does not refer to a port or a process. If
          <c><anno>Port</anno></c> is a closed port, nothing happens.
          If <c><anno>Port</anno></c>
          is an open port and the calling process is the port owner,
          the port replies with <c>{Port, connected}</c> to the old
          port owner. Notice that the old port owner is still linked to
          the port, while the new is not. If <c><anno>Port</anno></c> is an open
          port and the calling process is not the port owner,
          the <em>port owner</em> fails with <c>badsig</c>. The port
          owner fails with <c>badsig</c> also if <c><anno>Pid</anno></c> is not
          an existing local process identifier.</p>
        <p>Notice that any process can set the port owner using
          <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c>
          as if it itself was the port owner, but the reply always goes to
          the port owner.</p>
        <p>As from Erlang/OTP R16,
          <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c>
          is truly asynchronous. Notice that this operation has always been
          documented as an asynchronous operation, while the underlying
          implementation has been synchronous. <c>port_connect/2</c> is
          however still fully synchronous because of its error behavior.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Port</anno></c> is not an identifier of an open port,
            or the registered name of an open port. If the calling
            process was previously linked to the closed port,
            identified by <c><anno>Port</anno></c>, the exit signal
            from the port is guaranteed to be delivered before this
            <c>badarg</c> exception occurs.
          </item>
          <tag><c>badarg</c></tag>
          <item>If the process identified by <c>Pid</c> is not an existing
            local process.</item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="port_control" arity="3"/>
      <fsummary>Perform a synchronous control operation on a port.</fsummary>
      <desc>
        <p>Performs a synchronous control operation on a port.
          The meaning of <c><anno>Operation</anno></c> and
          <c><anno>Data</anno></c> depends on
          the port, that is, on the port driver. Not all port drivers
          support this control feature.</p>
        <p>Returns a list of integers in the range 0..255, or a
          binary, depending on the port driver. The meaning of
          the returned data also depends on the port driver.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Port</anno></c> is not an open port or the registered
            name of an open port.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Operation</anno></c> cannot fit in a 32-bit integer.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the port driver does not support synchronous control operations.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the port driver so decides for any reason (probably
            something wrong with <c><anno>Operation</anno></c> or
            <c><anno>Data</anno></c>).
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="1"/>
      <fsummary>Information about a port.</fsummary>
      <desc>
        <p>Returns a list containing tuples with information about
          <c><anno>Port</anno></c>, or <c>undefined</c> if the port is not open.
          The order of the tuples is undefined, and all the
          tuples are not mandatory.
          If the port is closed and the calling process
          was previously linked to the port, the exit signal from the
          port is guaranteed to be delivered before <c>port_info/1</c>
          returns <c>undefined</c>.</p>
        <p>The result contains information about the following
          <c>Item</c>s:</p>
        <list type="bulleted">
          <item><c>registered_name</c> (if the port has a registered
            name)</item>
          <item><c>id</c></item>
          <item><c>connected</c></item>
          <item><c>links</c></item>
          <item><c>name</c></item>
          <item><c>input</c></item>
          <item><c>output</c></item>
        </list>
        <p>For more information about the different <c>Item</c>s, see
          <seealso marker="#port_info/2"><c>port_info/2</c></seealso>.</p>
        <p>Failure: <c>badarg</c> if <c>Port</c> is not a local port
          identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="1"/>
      <fsummary>Information about the connected process of a port.</fsummary>
      <desc>
        <p><c><anno>Pid</anno></c> is the process identifier of the process
          connected to the port.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="2"/>
      <fsummary>Information about the internal index of a port.</fsummary>
      <desc>
        <p><c><anno>Index</anno></c> is the internal index of the port. This
          index can be used to separate ports.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="3"/>
      <fsummary>Information about the input of a port.</fsummary>
      <desc>
        <p><c><anno>Bytes</anno></c> is the total number of bytes
          read from the port.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="4"/>
      <fsummary>Information about the links of a port.</fsummary>
      <desc>
        <p><c><anno>Pids</anno></c> is a list of the process identifiers
          of the processes that the port is linked to.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="5"/>
      <fsummary>Information about the locking of a port.</fsummary>
      <desc>
        <p><c><anno>Locking</anno></c> is one of the following:</p>
        <list type="bulleted">
          <item><c>port_level</c> (port-specific locking)</item>
          <item><c>driver_level</c> (driver-specific locking)</item>
        </list>
        <p>Notice that these results are highly implementation-specific
          and can change in a future release.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="6"/>
      <fsummary>Information about the memory size of a port.</fsummary>
      <desc>
        <p><c><anno>Bytes</anno></c> is the total number of
          bytes allocated for this port by the runtime system. The
          port itself can have allocated memory that is not
          included in <c><anno>Bytes</anno></c>.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="7"/>
      <fsummary>Information about the monitors of a port.</fsummary>
      <desc>
        <p><c><anno>Monitors</anno></c> represent processes monitored by
          this port.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="8"/>
      <fsummary>Which processes are monitoring this port.</fsummary>
      <desc>
        <p>Returns list of pids that are monitoring given port at the
          moment.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="9"/>
      <fsummary>Information about the name of a port.</fsummary>
      <desc>
        <p><c><anno>Name</anno></c> is the command name set by
          <seealso marker="#open_port/2"><c>open_port/2</c></seealso>.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="10"/>
      <fsummary>Information about the OS pid of a port.</fsummary>
      <desc>
        <p><c><anno>OsPid</anno></c> is the process identifier (or equivalent)
          of an OS process created with
          <seealso marker="#open_port/2"><c>open_port({spawn | spawn_executable,
          Command}, Options)</c></seealso>. If the port is not the result of
          spawning an OS process, the value is <c>undefined</c>.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="11"/>
      <fsummary>Information about the output of a port.</fsummary>
      <desc>
        <p><c><anno>Bytes</anno></c> is the total number of bytes written
          to the port from Erlang processes using
          <seealso marker="#port_command/2"><c>port_command/2</c></seealso>,
          <seealso marker="#port_command/3"><c>port_command/3</c></seealso>,
          or <c><anno>Port</anno> ! {Owner, {command, Data}</c>.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="12"/>
      <fsummary>Information about the parallelism hint of a port.</fsummary>
      <desc>
        <p><c><anno>Boolean</anno></c> corresponds to the port parallelism
          hint used by this port. For more information, see option
          <seealso marker="#open_port_parallelism"><c>parallelism</c></seealso>
          of <seealso marker="#open_port/2"><c>open_port/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="13"/>
      <fsummary>Information about the queue size of a port.</fsummary>
      <desc>
        <p><c><anno>Bytes</anno></c> is the total number
          of bytes queued by the port using the ERTS driver queue
          implementation.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_info" arity="2" clause_i="14"/>
      <fsummary>Information about the registered name of a port.</fsummary>
      <desc>
        <p><c><anno>RegisteredName</anno></c> is the registered name of
          the port. If the port has no registered name, <c>[]</c> is
          returned.</p>
        <p>If the port identified by <c><anno>Port</anno></c> is not open,
          <c>undefined</c> is returned. If the port is closed and the
          calling process was previously linked to the port, the exit
          signal from the port is guaranteed to be delivered before
          <c>port_info/2</c> returns <c>undefined</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local
          port identifier, or an atom.</p>
      </desc>
    </func>

    <func>
      <name name="port_to_list" arity="1"/>
      <fsummary>Text representation of a port identifier.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of the port identifier <c><anno>Port</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="ports" arity="0"/>
      <fsummary>List all existing ports.</fsummary>
      <desc>
        <p>Returns a list of port identifiers corresponding to all the
          ports existing on the local node.</p>
        <p>Notice that an exiting port exists, but is not open.</p>
      </desc>
    </func>

    <func>
      <name name="pre_loaded" arity="0"/>
      <fsummary>List all preloaded modules.</fsummary>
      <desc>
        <p>Returns a list of Erlang modules that are preloaded in
          the system. As all loading of code is done through the file
          system, the file system must have been loaded previously.
          Hence, at least the module <c>init</c> must be preloaded.</p>
      </desc>
    </func>

    <func>
      <name name="process_display" arity="2"/>
      <fsummary>Write information about a local process on standard error.
      </fsummary>
      <desc>
        <p>Writes information about the local process <c><anno>Pid</anno></c> on
          standard error. The only allowed value for the atom
          <c><anno>Type</anno></c> is <c>backtrace</c>, which shows the contents
          of the call stack, including information about the call chain, with
          the current function printed first. The format of the output
          is not further defined.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="1"/>
      <fsummary>Set process flag trap_exit for the calling process.</fsummary>
      <desc>
        <p>When <c>trap_exit</c> is set to <c>true</c>, exit signals
          arriving to a process are converted to <c>{'EXIT', From, Reason}</c>
          messages, which can be received as ordinary
          messages. If <c>trap_exit</c> is set to <c>false</c>, the
          process exits if it receives an exit signal other than
          <c>normal</c> and the exit signal is propagated to its
          linked processes. Application processes are normally
          not to trap exits.</p>
        <p>Returns the old value of the flag.</p>
        <p>See also <seealso marker="#exit/2"><c>exit/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="2"/>
      <fsummary>Set process flag error_handler for the calling process.
      </fsummary>
      <desc>
        <p>Used by a process to redefine the error handler
          for undefined function calls and undefined registered
          processes. Inexperienced users are not to use this flag,
          as code auto-loading depends on the correct
          operation of the error handling module.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="3"
	    anchor="process_flag_min_heap_size"/>
      <fsummary>Set process flag min_heap_size for the calling process.
      </fsummary>
      <desc>
        <p>Changes the minimum heap size for the calling process.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="4"/>
      <fsummary>Set process flag min_bin_vheap_size for the calling process.
      </fsummary>
      <desc>
        <p>Changes the minimum binary virtual heap size for the calling
          process.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="5"
	    anchor="process_flag_max_heap_size"/>
      <fsummary>Set process flag max_heap_size for the calling process.
      </fsummary>
      <type name="max_heap_size"/>
      <desc>
        <p>This flag sets the maximum heap size for the calling process.
          If <c><anno>MaxHeapSize</anno></c> is an integer, the system default
          values for <c>kill</c> and <c>error_logger</c> are used.
        </p>
        <taglist>
          <tag><c>size</c></tag>
          <item>
            <p>The maximum size in words of the process. If set to zero, the
              heap size limit is disabled. <c>badarg</c> is be thrown if the
              value is smaller than <seealso marker="#process_flag_min_heap_size">
              <c>min_heap_size</c></seealso>. The size check is only done when
              a garbage collection is triggered.</p>
            <p><c>size</c> is the entire heap of the process when garbage collection
              is triggered. This includes all generational heaps, the process stack, 
              any <seealso marker="#process_flag_message_queue_data">
              messages that are considered to be part of the heap</seealso>, and any
              extra memory that the garbage collector needs during collection.</p>
            <p><c>size</c> is the same as can be retrieved using
              <seealso marker="#process_info_total_heap_size">
                <c>erlang:process_info(Pid, total_heap_size)</c></seealso>,
              or by adding <c>heap_block_size</c>, <c>old_heap_block_size</c>
              and <c>mbuf_size</c> from <seealso marker="#process_info_garbage_collection_info">
                <c>erlang:process_info(Pid, garbage_collection_info)</c></seealso>.</p>
          </item>
          <tag><c>kill</c></tag>
          <item>
            <p>When set to <c>true</c>, the runtime system sends an
              untrappable exit signal with reason <c>kill</c> to the process
              if the maximum heap size is reached. The garbage collection
              that triggered the <c>kill</c> is not completed, instead the
              process exits as soon as possible. When set to <c>false</c>,
              no exit signal is sent to the process, instead it continues
              executing.</p>
            <p>If <c>kill</c> is not defined in the map,
              the system default will be used. The default system default
              is <c>true</c>. It can be changed by either option
              <seealso marker="erl#+hmaxk">+hmaxk</seealso> in <c>erl(1)</c>,
              or <seealso marker="#system_flag_max_heap_size">
              <c>erlang:system_flag(max_heap_size, MaxHeapSize)</c></seealso>.</p>
          </item>
          <tag><c>error_logger</c></tag>
          <item>
            <p>When set to <c>true</c>, the runtime system sends a
              message to the current <seealso marker="kernel:error_logger">
              <c>error_logger</c></seealso>
              containing details about the process when the maximum
              heap size is reached. One <c>error_logger</c> report is sent
              each time the limit is reached.</p>
            <p>If <c>error_logger</c> is not defined in the map, the system
              default is used. The default system default is <c>true</c>.
              It can be changed by either the option
              <seealso marker="erl#+hmaxel">+hmaxel</seealso> int <c>erl(1)</c>,
              or <seealso marker="#system_flag_max_heap_size">
              <c>erlang:system_flag(max_heap_size, MaxHeapSize)</c></seealso>.</p>
          </item>
        </taglist>
        <p>The heap size of a process is quite hard to predict, especially the
          amount of memory that is used during the garbage collection. When
          contemplating using this option, it is recommended to first run
          it in production with <c>kill</c> set to <c>false</c> and inspect
          the <c>error_logger</c> reports to see what the normal peak sizes
          of the processes in the system is and then tune the value
          accordingly.
        </p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="6"
	    anchor="process_flag_message_queue_data"/>
      <fsummary>Set process flag message_queue_data for the calling process.
      </fsummary>
      <type name="message_queue_data"/>
      <desc>
        <p>This flag determines how messages in the message queue
          are stored, as follows:</p>
        <taglist>
          <tag><c>off_heap</c></tag>
          <item>
            <p><em>All</em> messages in the message queue will be stored
              outside of the process heap. This implies that <em>no</em>
              messages in the message queue will be part of a garbage
              collection of the process.</p>
          </item>
          <tag><c>on_heap</c></tag>
          <item>
            <p>All messages in the message queue will eventually be
              placed on heap. They can however temporarily be stored
              off heap. This is how messages always have been stored
              up until ERTS 8.0.</p>
          </item>
        </taglist>
        <p>The default <c>message_queue_data</c> process flag is determined
          by command-line argument <seealso marker="erl#+hmqd">
          <c>+hmqd</c></seealso> in <c>erl(1)</c>.</p>
        <p>If the process potentially can get many messages in its queue,
          you are advised to set the flag to <c>off_heap</c>. This
          because a garbage collection with many messages placed on
          the heap can become extremely expensive and the process can
          consume large amounts of memory. Performance of the
          actual message passing is however generally better when not
          using flag <c>off_heap</c>.</p>
        <p>When changing this flag messages will be moved. This work
          has been initiated but not completed when this function
          call returns.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="7"
	    anchor="process_flag_priority"/>
      <fsummary>Set process flag priority for the calling process.</fsummary>
      <type name="priority_level"/>
      <desc>
        <p>
          Sets the process priority. <c><anno>Level</anno></c> is an atom.
          Four priority levels exist: <c>low</c>,
          <c>normal</c>, <c>high</c>, and <c>max</c>. Default
          is <c>normal</c>.</p>
        <note>
          <p>Priority level <c>max</c> is reserved for internal use in
          the Erlang runtime system, and is <em>not</em> to be used
          by others.</p>
        </note>
        <p>Internally in each priority level, processes are scheduled
          in a round robin fashion.</p>
        <p>Execution of processes on priority <c>normal</c> and
          <c>low</c> are interleaved. Processes on priority
          <c>low</c> are selected for execution less
          frequently than processes on priority <c>normal</c>.</p>
        <p>When runnable processes on priority <c>high</c> exist,
          no processes on priority <c>low</c> or <c>normal</c> are
          selected for execution. Notice however that this does
          <em>not</em> mean that no processes on priority <c>low</c>
          or <c>normal</c> can run when processes
          are running on priority <c>high</c>. When using multiple
          schedulers, more processes can be running
          in parallel than processes on priority <c>high</c>. That is,
          a <c>low</c> and a <c>high</c> priority process can
          execute at the same time.</p>
        <p>When runnable processes on priority <c>max</c> exist,
          no processes on priority <c>low</c>, <c>normal</c>, or
          <c>high</c> are selected for execution. As with priority
          <c>high</c>, processes on lower priorities can
          execute in parallel with processes on priority <c>max</c>.</p>
        <p>Scheduling is pre-emptive. Regardless of priority, a process
          is pre-empted when it has consumed more than a certain number
          of reductions since the last time it was selected for
          execution.</p>
        <note>
          <p>Do not depend on the scheduling
          to remain exactly as it is today. Scheduling is likely to be
          changed in a future release to use available processor cores better.</p>
        </note>
        <p>There is <em>no</em> automatic mechanism for
          avoiding priority inversion, such as priority inheritance
          or priority ceilings. When using priorities,
          take this into account and handle such scenarios by
          yourself.</p>
        <p>Making calls from a <c>high</c> priority process into code
          that you has no control over can cause the <c>high</c>
          priority process to wait for a process with lower
          priority. That is, effectively decreasing the priority of the
          <c>high</c> priority process during the call. Even if this
          is not the case with one version of the code that you have no
          control over, it can be the case in a future
          version of it. This can, for example, occur if a
          <c>high</c> priority process triggers code loading, as
          the code server runs on priority <c>normal</c>.</p>
        <p>Other priorities than <c>normal</c> are normally not needed.
          When other priorities are used, use them with care,
          <em>especially</em> priority <c>high</c>. A
          process on priority <c>high</c> is only
          to perform work for short periods. Busy looping for
          long periods in a <c>high</c> priority process causes
          most likely problems, as important OTP servers
          run on priority <c>normal</c>.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="8"/>
      <fsummary>Set process flag save_calls for the calling process.</fsummary>
      <desc>
        <p><c><anno>N</anno></c> must be an integer in the interval 0..10000.
          If <c><anno>N</anno></c> &gt; 0, call saving is made
          active for the
          process. This means that information about the <c><anno>N</anno></c>
          most recent global function calls, BIF calls, sends, and
          receives made by the process are saved in a list, which
          can be retrieved with
          <c>process_info(Pid, last_calls)</c>. A global function
          call is one in which the module of the function is
          explicitly mentioned. Only a fixed amount of information
          is saved, as follows:</p>
        <list type="bulleted">
          <item><p>A tuple <c>{Module, Function, Arity}</c> for
            function calls</p></item>
          <item><p>The atoms <c>send</c>, <c>'receive'</c>, and
            <c>timeout</c> for sends and receives (<c>'receive'</c>
            when a message is received and <c>timeout</c> when a
            receive times out)</p></item>
        </list>
        <p>If <c>N</c> = 0,
          call saving is disabled for the process, which is the
          default. Whenever the size of the call saving list is set,
          its contents are reset.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="2" clause_i="9"/>
      <fsummary>Set process flag sensitive for the calling process.</fsummary>
      <desc>
        <p>Sets or clears flag <c>sensitive</c> for the current process.
          When a process has been marked as sensitive by calling
          <c>process_flag(sensitive, true)</c>, features in the runtime
          system that can be used for examining the data or inner working
          of the process are silently disabled.</p>
        <p>Features that are disabled include (but are not limited to)
          the following:</p>
        <list type="bulleted">
          <item><p>Tracing. Trace flags can still be set for the process,
            but no trace messages of any kind are generated. (If flag
            <c>sensitive</c> is turned off, trace messages are again
            generated if any trace flags are set.)</p></item>
          <item><p>Sequential tracing. The sequential trace token is
            propagated as usual, but no sequential trace messages are
            generated.</p></item>
        </list>
        <p><c>process_info/1,2</c> cannot be used to read out the
          message queue or the process dictionary (both are returned
          as empty lists).</p>
        <p>Stack back-traces cannot be displayed for the process.</p>
        <p>In crash dumps, the stack, messages, and the process dictionary
          are omitted.</p>
        <p>If <c>{save_calls,N}</c> has been set for the process, no
          function calls are saved to the call saving list.
          (The call saving list is not cleared. Also, send, receive,
          and time-out events are still added to the list.)</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="process_flag" arity="3"/>
      <fsummary>Set process flags for a process.</fsummary>
      <desc>
        <p>Sets certain flags for the process <c><anno>Pid</anno></c>,
          in the same manner as
          <seealso marker="#process_flag/2"><c>process_flag/2</c></seealso>.
          Returns the old value of the flag. The valid values for
          <c><anno>Flag</anno></c> are only a subset of those allowed in
          <c>process_flag/2</c>, namely <c>save_calls</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c>
          is not a local process.</p>
      </desc>
    </func>

    <func>
      <name name="process_info" arity="1"/>
      <fsummary>Information about a process.</fsummary>
      <type name="process_info_result_item"/>
      <type name="priority_level"/>
      <type name="stack_item"/>
      <type name="max_heap_size"/>
      <type name="message_queue_data"/>
      <desc>
        <p>Returns a list containing <c><anno>InfoTuple</anno></c>s with
          miscellaneous information about the process identified by
          <c>Pid</c>, or <c>undefined</c> if the process is not alive.</p>
        <p>The order of the <c><anno>InfoTuple</anno></c>s is undefined and
          all <c><anno>InfoTuple</anno></c>s are not mandatory.
          The <c><anno>InfoTuple</anno></c>s
          part of the result can be changed without prior notice.</p>
        <p>The <c><anno>InfoTuple</anno></c>s with the following items
          are part of the result:</p>
        <list type="bulleted">
          <item><c>current_function</c></item>
          <item><c>initial_call</c></item>
          <item><c>status</c></item>
          <item><c>message_queue_len</c></item>
          <item><c>messages</c></item>
          <item><c>links</c></item>
          <item><c>dictionary</c></item>
          <item><c>trap_exit</c></item>
          <item><c>error_handler</c></item>
          <item><c>priority</c></item>
          <item><c>group_leader</c></item>
          <item><c>total_heap_size</c></item>
          <item><c>heap_size</c></item>
          <item><c>stack_size</c></item>
          <item><c>reductions</c></item>
          <item><c>garbage_collection</c></item>
        </list>
        <p>If the process identified by <c><anno>Pid</anno></c> has a
          registered name,
          also an <c><anno>InfoTuple</anno></c> with item <c>registered_name</c>
          is included.</p>
        <p>For information about specific <c><anno>InfoTuple</anno></c>s, see
          <seealso marker="#process_info/2"><c>process_info/2</c></seealso>.</p>
        <warning>
          <p>This BIF is intended for <em>debugging only</em>. For
            all other purposes, use <seealso marker="#process_info/2">
            <c>process_info/2</c></seealso>.</p>
        </warning>
        <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c> is not a
          local process.</p>
      </desc>
    </func>

    <func>
      <name name="process_info" arity="2" clause_i="1"/>
      <name name="process_info" arity="2" clause_i="2"/>
      <fsummary>Information about a process.</fsummary>
      <type name="process_info_item"/>
      <type name="process_info_result_item"/>
      <type name="stack_item"/>
      <type name="priority_level"/>
      <type name="max_heap_size"/>
      <type name="message_queue_data"/>
      <desc>
        <p>Returns information about the process identified by
          <c><anno>Pid</anno></c>, as specified by
          <c><anno>Item</anno></c> or <c><anno>ItemList</anno></c>.
          Returns <c>undefined</c> if the process is not alive.</p>
        <p>If the process is alive and a single <c><anno>Item</anno></c>
          is specified, the returned value is the corresponding
          <c><anno>InfoTuple</anno></c>, unless <c>Item =:= registered_name</c>
          and the process has no registered name. In this case,
          <c>[]</c> is returned. This strange behavior is because of
          historical reasons, and is kept for backward compatibility.</p>
        <p>If <c><anno>ItemList</anno></c> is specified, the result is
          <c><anno>InfoTupleList</anno></c>.
          The <c><anno>InfoTuple</anno></c>s in
          <c><anno>InfoTupleList</anno></c> are included with the corresponding
          <c><anno>Item</anno></c>s in the same order as the
          <c><anno>Item</anno></c>s were included
          in <c><anno>ItemList</anno></c>. Valid <c><anno>Item</anno></c>s can
          be included multiple times in <c><anno>ItemList</anno></c>.</p>
        <note>
          <p>If <c>registered_name</c> is part of <c><anno>ItemList</anno></c>
            and the process has no name registered, a
            <c>{registered_name, []}</c>, <c><anno>InfoTuple</anno></c>
            <em>will</em> be included in the resulting
            <c><anno>InfoTupleList</anno></c>. This
            behavior is different when a single
            <c>Item =:= registered_name</c> is specified, and when
            <c>process_info/1</c> is used.</p>
        </note>
        <p>Valid <c><anno>InfoTuple</anno></c>s with corresponding
          <c><anno>Item</anno></c>s:</p>
        <taglist>
          <tag><c>{backtrace, <anno>Bin</anno>}</c></tag>
          <item>
            <p>Binary <c><anno>Bin</anno></c> contains the same information
              as the output from
              <c>erlang:process_display(<anno>Pid</anno>, backtrace)</c>. Use
              <c>binary_to_list/1</c> to obtain the string of characters
              from the binary.</p>
          </item>
          <tag><c>{binary, <anno>BinInfo</anno>}</c></tag>
          <item>
            <p><c><anno>BinInfo</anno></c> is a list containing miscellaneous
              information about binaries on the heap of this
              process.
              This <c><anno>InfoTuple</anno></c> can be changed or
              removed without prior notice. In the current implementation
              <c><anno>BinInfo</anno></c> is a list of tuples. The tuples
              contain; <c>BinaryId</c>, <c>BinarySize</c>, <c>BinaryRefcCount</c>.</p>
            <p>The message queue is on the heap depending on the
              process flag <seealso marker="#process_flag_message_queue_data">
            <c>message_queue_data</c></seealso>.</p>
          </item>
          <tag><c>{catchlevel, <anno>CatchLevel</anno>}</c></tag>
          <item>
            <p><c><anno>CatchLevel</anno></c> is the number of currently active
              catches in this process. This <c><anno>InfoTuple</anno></c> can be
              changed or removed without prior notice.</p>
          </item>
          <tag><c>{current_function, {<anno>Module</anno>,
            <anno>Function</anno>, Arity}}</c></tag>
          <item>
            <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>,
              <c><anno>Arity</anno></c> is
              the current function call of the process.</p>
          </item>
          <tag><c>{current_location, {<anno>Module</anno>,
            <anno>Function</anno>, <anno>Arity</anno>,
            <anno>Location</anno>}}</c></tag>
          <item>
            <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>,
              <c><anno>Arity</anno></c> is
              the current function call of the process.
              <c><anno>Location</anno></c> is a list of two-tuples describing
              the location in the source code.</p>
          </item>
          <tag><c>{current_stacktrace, <anno>Stack</anno>}</c></tag>
          <item>
            <p>Returns the current call stack back-trace (<em>stacktrace</em>)
              of the process. The stack has the same format as returned by
              <seealso marker="#get_stacktrace/0">
              <c>erlang:get_stacktrace/0</c></seealso>. The depth of the
              stacktrace is truncated according to the <c>backtrace_depth</c>
              system flag setting.</p>
          </item>
          <tag><c>{dictionary, <anno>Dictionary</anno>}</c></tag>
          <item>
            <p><c><anno>Dictionary</anno></c> is the process dictionary.</p>
          </item>
          <tag><c>{error_handler, <anno>Module</anno>}</c></tag>
          <item>
            <p><c><anno>Module</anno></c> is the error handler module used by
              the process (for undefined function calls, for example).</p>
          </item>
          <tag><c>{garbage_collection, <anno>GCInfo</anno>}</c></tag>
          <item>
            <p><c><anno>GCInfo</anno></c> is a list containing miscellaneous
              information about garbage collection for this process.
              The content of <c><anno>GCInfo</anno></c> can be changed without
              prior notice.</p>
          </item>
          <tag>
            <marker id="process_info_garbage_collection_info"/>
            <c>{garbage_collection_info, <anno>GCInfo</anno>}</c>
          </tag>
          <item>
            <p><c><anno>GCInfo</anno></c> is a list containing miscellaneous
              detailed information about garbage collection for this process.
              The content of <c><anno>GCInfo</anno></c> can be changed without
              prior notice. For details about the meaning of each item, see
              <seealso marker="#gc_minor_start"><c>gc_minor_start</c></seealso>
              in <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>.</p>
          </item>
          <tag><c>{group_leader, <anno>GroupLeader</anno>}</c></tag>
          <item>
            <p><c><anno>GroupLeader</anno></c> is the group leader for the I/O
              of the process.</p>
          </item>
          <tag><c>{heap_size, <anno>Size</anno>}</c></tag>
          <item>
            <p><c><anno>Size</anno></c> is the size in words of the youngest
              heap generation of the process. This generation includes
              the process stack. This information is highly
              implementation-dependent, and can change if the
              implementation changes.</p>
          </item>
          <tag><c>{initial_call, {<anno>Module</anno>, <anno>Function</anno>,
            <anno>Arity</anno>}}</c></tag>
          <item>
            <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>,
              <c><anno>Arity</anno></c> is
              the initial function call with which the process was
              spawned.</p>
          </item>
          <tag><c>{links, <anno>PidsAndPorts</anno>}</c></tag>
          <item>
            <p><c><anno>PidsAndPorts</anno></c> is a list of process identifiers
              and port identifiers, with processes or ports to which the process
              has a link.</p>
          </item>
          <tag><c>{last_calls, false|Calls}</c></tag>
          <item>
            <p>The value is <c>false</c> if call saving is not active
              for the process (see <seealso marker="#process_flag/3">
              <c>process_flag/3</c></seealso>).
              If call saving is active, a list is returned, in which
              the last element is the most recent called.</p>
          </item>
          <tag><c>{memory, <anno>Size</anno>}</c></tag>
          <item>
            <p><c><anno>Size</anno></c> is the size in bytes of the process.
              This includes call stack, heap, and internal structures.</p>
          </item>
          <tag><c>{message_queue_len, <anno>MessageQueueLen</anno>}</c></tag>
          <item>
            <p><c><anno>MessageQueueLen</anno></c> is the number of messages
              currently in the message queue of the process. This is the
              length of the list <c><anno>MessageQueue</anno></c> returned as
              the information item <c>messages</c> (see below).</p>
          </item>
          <tag><c>{messages, <anno>MessageQueue</anno>}</c></tag>
          <item>
            <p><c><anno>MessageQueue</anno></c> is a list of the messages to
              the process, which have not yet been processed.</p>
          </item>
          <tag><c>{min_heap_size, <anno>MinHeapSize</anno>}</c></tag>
          <item>
            <p><c><anno>MinHeapSize</anno></c> is the minimum heap size
              for the process.</p>
          </item>
          <tag><c>{min_bin_vheap_size, <anno>MinBinVHeapSize</anno>}</c></tag>
          <item>
            <p><c><anno>MinBinVHeapSize</anno></c> is the minimum binary virtual
              heap size for the process.</p>
          </item>
          <tag><c>{monitored_by, <anno>Pids</anno>}</c></tag>
          <item>
            <p>A list of process identifiers monitoring the process (with
              <c>monitor/2</c>).</p>
          </item>
          <tag><c>{monitors, <anno>Monitors</anno>}</c></tag>
          <item>
            <p>A list of monitors (started by <c>monitor/2</c>)
              that are active for the process. For a local process
              monitor or a remote process monitor by a process
              identifier, the list consists of:</p>
              <taglist>
                <tag><c>{process, <anno>Pid</anno>}</c></tag>
                <item>Process is monitored by pid.</item>
                <tag><c>{process, {<anno>RegName</anno>, <anno>Node</anno>}}</c></tag>
                <item>Local or remote process is monitored by name.</item>
                <tag><c>{port, PortId}</c></tag>
                <item>Local port is monitored by port id.</item>
                <tag><c>{port, {<anno>RegName</anno>, <anno>Node</anno>}}</c></tag>
                <item>Local port is monitored by name. Please note, that
                  remote port monitors are not supported, so <c>Node</c> will
                  always be the local node name.</item>
              </taglist>
          </item>
          <tag><c>{message_queue_data, <anno>MQD</anno>}</c></tag>
          <item>
            <p>Returns the current state of process flag
              <c>message_queue_data</c>. <c><anno>MQD</anno></c> is either
              <c>off_heap</c> or <c>on_heap</c>. For more
              information, see the documentation of
              <seealso marker="#process_flag_message_queue_data">
              <c>process_flag(message_queue_data, MQD)</c></seealso>.</p>
          </item>
          <tag><c>{priority, <anno>Level</anno>}</c></tag>
          <item>
            <p><c><anno>Level</anno></c> is the current priority level for
              the process. For more information on priorities, see
              <seealso marker="#process_flag_priority">
              <c>process_flag(priority, Level)</c></seealso>.</p>
          </item>
          <tag><c>{reductions, <anno>Number</anno>}</c></tag>
          <item>
            <p><c><anno>Number</anno></c> is the number of reductions executed
              by the process.</p>
          </item>
          <tag><c>{registered_name, <anno>Atom</anno>}</c></tag>
          <item>
            <p><c><anno>Atom</anno></c> is the registered process name.
              If the process has no registered name, this tuple is not
              present in the list.</p>
          </item>
          <tag><c>{sequential_trace_token, [] |
            <anno>SequentialTraceToken</anno>}</c></tag>
          <item>
            <p><c><anno>SequentialTraceToken</anno></c> is the sequential trace
              token for the process. This <c><anno>InfoTuple</anno></c> can be
              changed or removed without prior notice.</p>
          </item>
          <tag><c>{stack_size, <anno>Size</anno>}</c></tag>
          <item>
            <p><c><anno>Size</anno></c> is the stack size, in words,
              of the process.</p>
          </item>
          <tag><c>{status, <anno>Status</anno>}</c></tag>
          <item>
            <p><c><anno>Status</anno></c> is the status of the process and is
              one of the following:</p>
            <list type="bulleted">
              <item><c>exiting</c></item>
              <item><c>garbage_collecting</c></item>
              <item><c>waiting</c> (for a message)</item>
              <item><c>running</c></item>
              <item><c>runnable</c> (ready to run, but another process is
                running)</item>
              <item><c>suspended</c> (suspended on a "busy" port
                or by the BIF <c>erlang:suspend_process/1,2</c>)</item>
            </list>
          </item>
          <tag><c>{suspending, <anno>SuspendeeList</anno>}</c></tag>
          <item>
            <p><c><anno>SuspendeeList</anno></c> is a list of
              <c>{<anno>Suspendee</anno>, <anno>ActiveSuspendCount</anno>,
              <anno>OutstandingSuspendCount</anno>}</c> tuples.
              <c><anno>Suspendee</anno></c> is the process identifier of a
              process that has been, or is to be,
              suspended by the process identified by <c><anno>Pid</anno></c>
              through the BIF <seealso marker="#suspend_process/2">
              <c>erlang:suspend_process/2</c></seealso> or
              <seealso marker="#suspend_process/1">
              <c>erlang:suspend_process/1</c></seealso>.</p>
            <p><c><anno>ActiveSuspendCount</anno></c> is the number of
              times <c><anno>Suspendee</anno></c> has been suspended by
              <c><anno>Pid</anno></c>.
              <c><anno>OutstandingSuspendCount</anno></c> is the number of not
              yet completed suspend requests sent by <c><anno>Pid</anno></c>,
              that is:</p>
            <list type="bulleted">
              <item>
                <p>If <c><anno>ActiveSuspendCount</anno> =/= 0</c>,
                  <c><anno>Suspendee</anno></c> is
                  currently in the suspended state.</p>
              </item>
              <item>
                <p>If <c><anno>OutstandingSuspendCount</anno> =/= 0</c>,
                  option <c>asynchronous</c> of <c>erlang:suspend_process/2</c>
                  has been used and the suspendee has not yet been
                  suspended by <c><anno>Pid</anno></c>.</p>
              </item>
            </list>
            <p>Notice that <c><anno>ActiveSuspendCount</anno></c> and
              <c><anno>OutstandingSuspendCount</anno></c> are not the
              total suspend count on <c><anno>Suspendee</anno></c>,
              only the parts contributed by <c><anno>Pid</anno></c>.</p>
          </item>
          <tag>
            <marker id="process_info_total_heap_size"/>
            <c>{total_heap_size, <anno>Size</anno>}</c>
          </tag>
          <item>
            <p><c><anno>Size</anno></c> is the total size, in words, of all heap
              fragments of the process. This includes the process stack and
              any unreceived messages that are considered to be part of the
              heap.</p>
          </item>
          <tag><c>{trace, <anno>InternalTraceFlags</anno>}</c></tag>
          <item>
            <p><c><anno>InternalTraceFlags</anno></c> is an integer
              representing the internal trace flag for this process.
              This <c><anno>InfoTuple</anno></c>
              can be changed or removed without prior notice.</p>
          </item>
          <tag><c>{trap_exit, <anno>Boolean</anno>}</c></tag>
          <item>
            <p><c><anno>Boolean</anno></c> is <c>true</c> if the process
              is trapping exits, otherwise <c>false</c>.</p>
          </item>
        </taglist>
        <p>Notice that not all implementations support all
          these <c><anno>Item</anno></c>s.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>Pid</anno></c> is not a local process.</item>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>Item</anno></c> is an invalid item.</item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="processes" arity="0"/>
      <fsummary>All processes.</fsummary>
      <desc>
        <p>Returns a list of process identifiers corresponding to
          all the processes currently existing on the local node.</p>
        <p>Notice that an exiting process exists, but is not alive.
          That is, <c>is_process_alive/1</c> returns <c>false</c>
          for an exiting process, but its process identifier is part
          of the result returned from <c>processes/0</c>.</p>
        <p>Example:</p>
        <pre>
> <input>processes().</input>
[&lt;0.0.0&gt;,&lt;0.2.0&gt;,&lt;0.4.0&gt;,&lt;0.5.0&gt;,&lt;0.7.0&gt;,&lt;0.8.0&gt;]</pre>
      </desc>
    </func>

    <func>
      <name name="purge_module" arity="1"/>
      <fsummary>Remove old code for a module.</fsummary>
      <desc>
        <p>Removes old code for <c><anno>Module</anno></c>.
          Before this BIF is used,
          <seealso marker="#check_process_code/2">
          <c>check_process_code/2</c></seealso>is to be called to check
          that no processes execute old code in the module.</p>
        <warning>
          <p>This BIF is intended for the code server (see
            <seealso marker="kernel:code"><c>code(3)</c></seealso>)
            and is not to be used elsewhere.</p>
        </warning>
        <note>
          <p>As from ERTS 8.0 (Erlang/OTP 19), any lingering processes
            that still execute the old code is killed by this function.
            In earlier versions, such incorrect use could cause much
            more fatal failures, like emulator crash.</p>
        </note>
        <p>Failure: <c>badarg</c> if there is no old code for
          <c><anno>Module</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="put" arity="2"/>
      <fsummary>Add a new value to the process dictionary.</fsummary>
      <desc>
        <p>Adds a new <c><anno>Key</anno></c> to the process dictionary,
          associated with the value <c><anno>Val</anno></c>, and returns
          <c>undefined</c>. If <c><anno>Key</anno></c> exists, the old
          value is deleted and replaced by <c><anno>Val</anno></c>, and
          the function returns the old value. Example:</p>
        <pre>
> <input>X = put(name, walrus), Y = put(name, carpenter),</input>
<input>Z = get(name),</input>
<input>{X, Y, Z}.</input>
{undefined,walrus,carpenter}</pre>
        <note>
          <p>The values stored when <c>put</c> is evaluated within
            the scope of a <c>catch</c> are not retracted if a
            <c>throw</c> is evaluated, or if an error occurs.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="raise" arity="3"/>
      <fsummary>Stop execution with an exception of specified class, reason,
        and call stack backtrace.</fsummary>
      <type name="raise_stacktrace"/>
      <desc>
        <p>Stops the execution of the calling process with an
          exception of the specified class, reason, and call stack backtrace
          (<em>stacktrace</em>).</p>
        <p><c><anno>Class</anno></c> is <c>error</c>, <c>exit</c>, or
          <c>throw</c>. So, if it were not for the stacktrace,
          <c>erlang:raise(<anno>Class</anno>, <anno>Reason</anno>,
          <anno>Stacktrace</anno>)</c> is equivalent to
          <c>erlang:<anno>Class</anno>(<anno>Reason</anno>)</c>.</p>
        <p><c><anno>Reason</anno></c> is any term.
          <c><anno>Stacktrace</anno></c> is a list as
          returned from <c>get_stacktrace()</c>, that is, a list of
          four-tuples <c>{Module, Function, Arity | Args,
          Location}</c>, where <c>Module</c> and <c>Function</c>
          are atoms, and the third element is an integer arity or an
          argument list. The stacktrace can also contain <c>{Fun,
          Args, Location}</c> tuples, where <c>Fun</c> is a local
          fun and <c>Args</c> is an argument list.</p>
        <p>Element <c>Location</c> at the end is optional.
          Omitting it is equivalent to specifying an empty list.</p>
        <p>The stacktrace is used as the exception stacktrace for the
          calling process; it is truncated to the current
          maximum stacktrace depth.</p>
        <p>As evaluating this function causes the process to
          terminate, it has no return value unless the arguments are
          invalid, in which case the function <em>returns the error
          reason</em> <c>badarg</c>. If you want to be
          sure not to return, you can call
          <c>error(erlang:raise(<anno>Class</anno>, <anno>Reason</anno>,
          <anno>Stacktrace</anno>))</c>
          and hope to distinguish exceptions later.</p>
      </desc>
    </func>

    <func>
      <name name="read_timer" arity="1"/>
      <fsummary>Read the state of a timer.</fsummary>
      <desc>
        <p>Reads the state of a timer. The same as calling
          <seealso marker="#read_timer/2"><c>erlang:read_timer(TimerRef,
          [])</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="read_timer" arity="2"/>
      <fsummary>Read the state of a timer.</fsummary>
      <desc>
        <p>Reads the state of a timer that has been created by either
          <seealso marker="#start_timer/4"><c>erlang:start_timer</c></seealso>
          or <seealso marker="#send_after/4"><c>erlang:send_after</c></seealso>.
          <c><anno>TimerRef</anno></c> identifies the timer, and
          was returned by the BIF that created the timer.</p>
        <p><c><anno>Option</anno>s</c>:</p>
        <taglist>
        <tag><c>{async, Async}</c></tag>
          <item>
            <p>Asynchronous request for state information. <c>Async</c>
              defaults to <c>false</c>, which causes the operation
              to be performed synchronously. In this case, the <c>Result</c>
              is returned by <c>erlang:read_timer</c>. When
              <c>Async</c> is <c>true</c>, <c>erlang:read_timer</c>
              sends an asynchronous request for the state information
              to the timer service that manages the timer, and then returns
              <c>ok</c>. A message on the format <c>{read_timer,
              <anno>TimerRef</anno>, <anno>Result</anno>}</c> is
              sent to the caller of <c>erlang:read_timer</c> when the
              operation has been processed.</p>
          </item>
        </taglist>
        <p>More <c><anno>Option</anno></c>s can be added in the future.</p>
        <p>If <c><anno>Result</anno></c> is an integer, it represents the
          time in milliseconds left until the timer expires.</p>
        <p>If <c><anno>Result</anno></c> is <c>false</c>, a
          timer corresponding to <c><anno>TimerRef</anno></c> could not
          be found. This because the timer had expired,
          or been canceled, or because <c><anno>TimerRef</anno></c>
          never has corresponded to a timer. Even if the timer has expired,
          it does not tell you whether or not the time-out message has
          arrived at its destination yet.</p>
        <note>
          <p>The timer service that manages the timer can be co-located
            with another scheduler than the scheduler that the calling
            process is executing on. If so, communication
            with the timer service takes much longer time than if it
            is located locally. If the calling process is in a critical
            path, and can do other things while waiting for the result
            of this operation, you want to use option <c>{async, true}</c>.
            If using option <c>{async, false}</c>, the calling
            process is blocked until the operation has been performed.</p>
         </note>
        <p>See also 
          <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>,
          <seealso marker="#start_timer/4">
          <c>erlang:start_timer/4</c></seealso>, and
          <seealso marker="#cancel_timer/2">
          <c>erlang:cancel_timer/2</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="ref_to_list" arity="1"/>
      <fsummary>Text representation of a reference.</fsummary>
      <desc>
        <p>Returns a string corresponding to the text
          representation of <c><anno>Ref</anno></c>.</p>
        <warning>
          <p>This BIF is intended for debugging and is not to be used
            in application programs.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="register" arity="2"/>
      <fsummary>Register a name for a pid (or port).</fsummary>
      <desc>
        <p>Associates the name <c><anno>RegName</anno></c> with a process
          identifier (pid) or a port identifier.
          <c><anno>RegName</anno></c>, which must be an atom, can be used
          instead of the pid or port identifier in send operator
          (<c><anno>RegName</anno> ! Message</c>). Example:</p>
        <pre>
> <input>register(db, Pid).</input>
true</pre>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
            <item>If <c><anno>PidOrPort</anno></c> is not an existing local
              process or port.</item>
          <tag><c>badarg</c></tag>
            <item>If <c><anno>RegName</anno></c> is already in use.</item>
          <tag><c>badarg</c></tag>
            <item>If the process or port is already registered
              (already has a name).</item>
          <tag><c>badarg</c></tag>
            <item>If <c><anno>RegName</anno></c> is the atom
              <c>undefined</c>.</item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="registered" arity="0"/>
      <fsummary>All registered names.</fsummary>
      <desc>
        <p>Returns a list of names that have been registered using
          <seealso marker="#register/2"><c>register/2</c></seealso>, for
          example:</p>
        <pre>
> <input>registered().</input>
[code_server, file_server, init, user, my_db]</pre>
      </desc>
    </func>

    <func>
      <name name="resume_process" arity="1"/>
      <fsummary>Resume a suspended process.</fsummary>
      <desc>
        <p>Decreases the suspend count on the process identified by
          <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c>
          is previously to have been suspended through
          <seealso marker="#suspend_process/2">
          <c>erlang:suspend_process/2</c></seealso> or
          <seealso marker="#suspend_process/1">
          <c>erlang:suspend_process/1</c></seealso>
          by the process calling
          <c>erlang:resume_process(<anno>Suspendee</anno>)</c>. When the
          suspend count on <c><anno>Suspendee</anno></c> reaches zero,
          <c><anno>Suspendee</anno></c> is resumed, that is, its state
          is changed from suspended into the state it had before it was
          suspended.</p>
        <warning>
          <p>This BIF is intended for debugging only.</p>
        </warning>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Suspendee</anno></c> is not a process identifier.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the process calling <c>erlang:resume_process/1</c> had
            not previously increased the suspend count on the process
            identified by <c><anno>Suspendee</anno></c>.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the process identified by <c><anno>Suspendee</anno></c>
            is not alive.
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="round" arity="1"/>
      <fsummary>Return an integer by rounding a number.</fsummary>
      <desc>
        <p>Returns an integer by rounding <c><anno>Number</anno></c>,
          for example:</p>
        <pre>
<input>round(5.5).</input>
6</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="self" arity="0"/>
      <fsummary>Return pid of the calling process.</fsummary>
      <desc>
        <p>Returns the process identifier of the calling process, for
          example:</p>
        <pre>
> <input>self().</input>
&lt;0.26.0></pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="send" arity="2"/>
      <fsummary>Send a message.</fsummary>
      <type name="dst"/>
      <desc>
        <p>Sends a message and returns <c><anno>Msg</anno></c>. This
          is the same as <c><anno>Dest</anno> ! <anno>Msg</anno></c>.</p>
        <p><c><anno>Dest</anno></c> can be a remote or local process identifier,
          a (local) port, a locally registered name, or a tuple
          <c>{<anno>RegName</anno>, <anno>Node</anno>}</c>
          for a registered name at another node.</p>
      </desc>
    </func>

    <func>
      <name name="send" arity="3"/>
      <fsummary>Send a message conditionally.</fsummary>
      <type name="dst"/>
      <desc>
        <p>Either sends a message and returns <c>ok</c>, or does not send
          the message but returns something else (see below).
          Otherwise the same as
          <seealso marker="#send/2"><c>erlang:send/2</c></seealso>.
          For more detailed explanation and warnings, see
          <seealso marker="#send_nosuspend/2">
          <c>erlang:send_nosuspend/2,3</c></seealso>.</p>
        <p>Options:</p>
        <taglist>
          <tag><c>nosuspend</c></tag>
          <item>If the sender would have to be suspended to do the send,
            <c>nosuspend</c> is returned instead.
          </item>
          <tag><c>noconnect</c></tag>
          <item>
            If the destination node would have to be auto-connected
             to do the send, <c>noconnect</c> is returned
             instead.
          </item>
        </taglist>
        <warning>
          <p>As with <c>erlang:send_nosuspend/2,3</c>: use with extreme
            care.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="send_after" arity="3"/>
      <fsummary>Start a timer.</fsummary>
      <desc>
        <p>Starts a timer. The same as calling
          <seealso marker="#send_after/4">
          <c>erlang:send_after(<anno>Time</anno>, <anno>Dest</anno>,
          <anno>Msg</anno>, [])</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="send_after" arity="4"/>
      <fsummary>Start a timer.</fsummary>
      <desc>
        <p>Starts a timer. When the timer expires, the message
          <c><anno>Msg</anno></c> is sent to the process
          identified by <c><anno>Dest</anno></c>. Apart from
          the format of the time-out message, this function works exactly as
          <seealso marker="#start_timer/4">
          <c>erlang:start_timer/4</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="send_nosuspend" arity="2"/>
      <fsummary>Try to send a message without ever blocking.</fsummary>
      <type name="dst"/>
      <desc>
        <p>The same as
          <seealso marker="#send/3"><c>erlang:send(<anno>Dest</anno>,
          <anno>Msg</anno>, [nosuspend])</c></seealso>,
          but returns <c>true</c> if
          the message was sent and <c>false</c> if the message was not
          sent because the sender would have had to be suspended.</p>
        <p>This function is intended for send operations to an
          unreliable remote node without ever blocking the sending
          (Erlang) process. If the connection to the remote node
          (usually not a real Erlang node, but a node written in C or
          Java) is overloaded, this function <em>does not send the message</em>
          and returns <c>false</c>.</p>
        <p>The same occurs if <c><anno>Dest</anno></c> refers to a local port
          that is busy. For all other destinations (allowed for the ordinary
          send operator <c>'!'</c>), this function sends the message and
          returns <c>true</c>.</p>
        <p>This function is only to be used in rare circumstances
          where a process communicates with Erlang nodes that can
          disappear without any trace, causing the TCP buffers and
          the drivers queue to be over-full before the node is
          shut down (because of tick time-outs) by <c>net_kernel</c>.
          The normal reaction to take when this occurs is some kind of
          premature shutdown of the other node.</p>
        <p>Notice that ignoring the return value from this function would
          result in an <em>unreliable</em> message passing, which is
          contradictory to the Erlang programming model. The message is
          <em>not</em> sent if this function returns <c>false</c>.</p>
        <p>In many systems, transient states of
          overloaded queues are normal. Although this function
          returns <c>false</c> does not mean that the other
          node is guaranteed to be non-responsive, it could be a
          temporary overload. Also, a return value of <c>true</c> does
          only mean that the message can be sent on the (TCP) channel
          without blocking; the message is not guaranteed to
          arrive at the remote node. For a disconnected
          non-responsive node, the return value is <c>true</c> (mimics
          the behavior of operator <c>!</c>). The expected
          behavior and the actions to take when the function
          returns <c>false</c> are application- and hardware-specific.</p>
        <warning>
          <p>Use with extreme care.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="send_nosuspend" arity="3"/>
      <fsummary>Try to send a message without ever blocking.</fsummary>
      <type name="dst"/>
      <desc>
        <p>The same as
          <seealso marker="#send/3"><c>erlang:send(<anno>Dest</anno>,
          <anno>Msg</anno>, [nosuspend | <anno>Options</anno>])</c></seealso>,
          but with a Boolean return value.</p>
        <p>This function behaves like
          <seealso marker="#send_nosuspend/2">
          <c>erlang:send_nosuspend/2</c></seealso>,
          but takes a third parameter, a list of options.
          The only option is <c>noconnect</c>, which
          makes the function return <c>false</c> if
          the remote node is not currently reachable by the local
          node. The normal behavior is to try to connect to the node,
          which can stall the process during a short period. The use of
          option <c>noconnect</c> makes it possible to be
          sure not to get the slightest delay when
          sending to a remote process. This is especially useful when
          communicating with nodes that expect to always be
          the connecting part (that is, nodes written in C or Java).</p>
        <p>Whenever the function returns <c>false</c> (either when a
          suspend would occur or when <c>noconnect</c> was specified and
          the node was not already connected), the message is guaranteed
          <em>not</em> to have been sent.</p>
        <warning>
          <p>Use with extreme care.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="set_cookie" arity="2"/>
      <fsummary>Set the magic cookie of a node.</fsummary>
      <desc>
        <p>Sets the magic cookie of <c><anno>Node</anno></c> to the atom
          <c><anno>Cookie</anno></c>. If <c><anno>Node</anno></c> is the
          local node, the function
          also sets the cookie of all other unknown nodes to
          <c><anno>Cookie</anno></c> (see section
          <seealso marker="doc/reference_manual:distributed">
          Distributed Erlang</seealso>
          in the Erlang Reference Manual in System Documentation).</p>
        <p>Failure: <c>function_clause</c> if the local node is not
          alive.</p>
      </desc>
    </func>

    <func>
      <name name="setelement" arity="3"/>
      <fsummary>Set the Nth element of a tuple.</fsummary>
      <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno></type_desc>
      <desc>
        <p>Returns a tuple that is a copy of argument
          <c><anno>Tuple1</anno></c>
          with the element specified by integer argument
          <c><anno>Index</anno></c>
          (the first element is the element with index 1) replaced by
          argument <c><anno>Value</anno></c>, for example:</p>
        <pre>
> <input>setelement(2, {10, green, bottles}, red).</input>
{10,red,bottles}</pre>
      </desc>
    </func>

    <func>
      <name name="size" arity="1"/>
      <fsummary>Size of a tuple or binary.</fsummary>
      <desc>
        <p>Returns the number of elements in a tuple or the number of
          bytes in a binary or bitstring, for example:</p>
        <pre>
> <input>size({morni, mulle, bwange}).</input>
3
> <input>size(&lt;&lt;11, 22, 33&gt;&gt;).</input>
3</pre>
        <p>For bitstrings, the number of whole bytes is returned.
          That is, if the number of bits
          in the bitstring is not divisible by 8, the resulting
          number of bytes is rounded <em>down</em>.</p>
        <p>Allowed in guard tests.</p>
        <p>See also
          <seealso marker="#tuple_size/1"><c>tuple_size/1</c></seealso>,
          <seealso marker="#byte_size/1"><c>byte_size/1</c></seealso>, and
          <seealso marker="#bit_size/1"><c>bit_size/1</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn" arity="1"/>
      <fsummary>Create a new process with a fun as entry point.</fsummary>
      <desc>
        <p>Returns the process identifier of a new process started by the
          application of <c><anno>Fun</anno></c> to the empty list
          <c>[]</c>. Otherwise
          works like <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn" arity="2"/>
      <fsummary>Create a new process with a fun as entry point on a specified
        node.</fsummary>
      <desc>
        <p>Returns the process identifier of a new process started
          by the application of <c><anno>Fun</anno></c> to the
          empty list <c>[]</c> on <c><anno>Node</anno></c>. If
          <c><anno>Node</anno></c> does not exist, a useless pid is
          returned. Otherwise works like
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn" arity="3"/>
      <fsummary>Create a new process with a function as entry point.</fsummary>
      <desc>
        <p>Returns the process identifier of a new process started by
          the application of <c><anno>Module</anno>:<anno>Function</anno></c>
          to <c><anno>Args</anno></c>.</p>
        <p><c>error_handler:undefined_function(<anno>Module</anno>,
          <anno>Function</anno>, <anno>Args</anno>)</c>
          is evaluated by the new process if
          <c><anno>Module</anno>:<anno>Function</anno>/Arity</c>
          does not exist (where <c>Arity</c> is the length of
          <c><anno>Args</anno></c>). The error handler
          can be redefined (see
          <seealso marker="#process_flag/2"><c>process_flag/2</c></seealso>).
          If <c>error_handler</c> is undefined, or the user has
          redefined the default <c>error_handler</c> and its replacement is
          undefined, a failure with reason <c>undef</c> occurs.</p>
        <p>Example:</p>
        <pre>
> <input>spawn(speed, regulator, [high_speed, thin_cut]).</input>
&lt;0.13.1></pre>
      </desc>
    </func>

    <func>
      <name name="spawn" arity="4"/>
      <fsummary>Create a new process with a function as entry point on a
        specified node.</fsummary>
      <desc>
        <p>Returns the process identifier (pid) of a new process started
          by the application
          of <c><anno>Module</anno>:<anno>Function</anno></c>
          to <c><anno>Args</anno></c> on <c><anno>Node</anno></c>. If
          <c><anno>Node</anno></c> does not exist, a useless pid is returned.
          Otherwise works like
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_link" arity="1"/>
      <fsummary>Create and link to a new process with a fun as entry point.
      </fsummary>
      <desc>
        <p>Returns the process identifier of a new process started by
          the application of <c><anno>Fun</anno></c> to the empty list
          <c>[]</c>. A link is created between
          the calling process and the new process, atomically.
          Otherwise works like
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_link" arity="2"/>
      <fsummary>Create and link to a new process with a fun as entry point on
        a specified node.</fsummary>
      <desc>
        <p>Returns the process identifier (pid) of a new process started
          by the application of <c><anno>Fun</anno></c> to the empty
          list <c>[]</c> on <c><anno>Node</anno></c>. A link is
          created between the calling process and the new process,
          atomically. If <c><anno>Node</anno></c> does not exist,
          a useless pid is returned and an exit signal with
          reason <c>noconnection</c> is sent to the calling
          process. Otherwise works like <seealso marker="#spawn/3">
          <c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_link" arity="3"/>
      <fsummary>Create and link to a new process with a function as entry point.
      </fsummary>
      <desc>
        <p>Returns the process identifier of a new process started by
          the application of <c><anno>Module</anno>:<anno>Function</anno></c>
          to <c><anno>Args</anno></c>. A link is created
          between the calling process and the new process, atomically.
          Otherwise works like
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_link" arity="4"/>
      <fsummary>Create and link to a new process with a function as entry point
        on a specified node.</fsummary>
      <desc>
        <p>Returns the process identifier (pid) of a new process
          started by the application
          of <c><anno>Module</anno>:<anno>Function</anno></c>
          to <c><anno>Args</anno></c> on <c><anno>Node</anno></c>. A
          link is created between the calling process and the new
          process, atomically. If <c><anno>Node</anno></c> does
          not exist, a useless pid is returned and an exit signal with
          reason <c>noconnection</c> is sent to the calling
          process. Otherwise works like <seealso marker="#spawn/3">
          <c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_monitor" arity="1"/>
      <fsummary>Create and monitor a new process with a fun as entry point.
      </fsummary>
      <desc>
        <p>Returns the process identifier of a new process, started by
          the application of <c><anno>Fun</anno></c> to the empty list
          <c>[]</c>,
          and a reference for a monitor created to the new process.
          Otherwise works like
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_monitor" arity="3"/>
      <fsummary>Create and monitor a new process with a function as entry point.
      </fsummary>
      <desc>
        <p>A new process is started by the application
          of <c><anno>Module</anno>:<anno>Function</anno></c>
          to <c><anno>Args</anno></c>. The process is
          monitored at the same time. Returns the process identifier
          and a reference for the monitor. Otherwise works like
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_opt" arity="2"/>
      <fsummary>Create a new process with a fun as entry point.</fsummary>
      <type name="priority_level"/>
      <type name="max_heap_size"/>
      <type name="message_queue_data"/>
      <type name="spawn_opt_option"/>
      <desc>
        <p>Returns the process identifier (pid) of a new process
          started by the application of <c><anno>Fun</anno></c>
          to the empty list <c>[]</c>. Otherwise works like
          <seealso marker="#spawn_opt/4"><c>spawn_opt/4</c></seealso>.</p>
        <p>If option <c>monitor</c> is specified, the newly created
          process is monitored, and both the pid and reference for
          the monitor are returned.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_opt" arity="3"/>
      <fsummary>Create a new process with a fun as entry point on a specified
        node.</fsummary>
      <type name="priority_level"/>
      <type name="max_heap_size"/>
      <type name="message_queue_data"/>
      <type name="spawn_opt_option"/>
      <desc>
        <p>Returns the process identifier (pid) of a new process started
          by the application of <c><anno>Fun</anno></c> to the
          empty list <c>[]</c> on <c><anno>Node</anno></c>. If
          <c><anno>Node</anno></c> does not exist, a useless pid is
          returned. Otherwise works like
          <seealso marker="#spawn_opt/4"><c>spawn_opt/4</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="spawn_opt" arity="4"/>
      <fsummary>Create a new process with a function as entry point.</fsummary>
      <type name="priority_level"/>
      <type name="max_heap_size"/>
      <type name="message_queue_data"/>
      <type name="spawn_opt_option"/>
      <desc>
        <p>Works as
          <seealso marker="#spawn/3"><c>spawn/3</c></seealso>, except that an
          extra option list is specified when creating the process.</p>
        <p>If option <c>monitor</c> is specified, the newly created
          process is monitored, and both the pid and reference for
          the monitor are returned.</p>
        <p>Options:</p>
        <taglist>
          <tag><c>link</c></tag>
          <item>
            <p>Sets a link to the parent process (like
              <seealso marker="#spawn_link/3"><c>spawn_link/3</c></seealso>
              does).</p>
          </item>
          <tag><c>monitor</c></tag>
          <item>
            <p>Monitors the new process (like
              <seealso marker="#monitor/2"><c>monitor/2</c></seealso> does).</p>
          </item>
          <tag><c>{priority, <anno>Level</anno></c></tag>
          <item>
            <p>Sets the priority of the new process. Equivalent to
              executing <seealso marker="#process_flag_priority">
              <c>process_flag(priority, <anno>Level</anno>)</c></seealso>
              in the start function of the new process,
              except that the priority is set before the process is
              selected for execution for the first time. For more
              information on priorities, see
              <seealso marker="#process_flag_priority">
              <c>process_flag(priority, <anno>Level</anno>)</c></seealso>.</p>
          </item>
          <tag><c>{fullsweep_after, <anno>Number</anno>}</c></tag>
          <item>
            <p>Useful only for performance tuning. Do not use this
              option unless you
              know that there is problem with execution times or
              memory consumption, and ensure
              that the option improves matters.</p>
            <p>The Erlang runtime system uses a generational garbage
              collection scheme, using an "old heap" for data that has
              survived at least one garbage collection. When there is
              no more room on the old heap, a fullsweep garbage
              collection is done.</p>
            <p>Option <c>fullsweep_after</c> makes it possible to
              specify the maximum number of generational collections
              before forcing a fullsweep, even if there is room on
              the old heap. Setting the number to zero
              disables the general collection algorithm, that is,
              all live data is copied at every garbage collection.</p>
            <p>A few cases when it can be useful to change
              <c>fullsweep_after</c>:</p>
            <list type="bulleted">
              <item><p>If binaries that are no longer used are to be
                thrown away as soon as possible. (Set
                <c><anno>Number</anno></c> to zero.)</p>
              </item>
              <item><p>A process that mostly have short-lived data is
                fullsweeped seldom or never, that is, the old heap
                contains mostly garbage. To ensure a fullsweep
                occasionally, set <c><anno>Number</anno></c> to a
                suitable value, such as 10 or 20.</p>
              </item>
              <item>In embedded systems with a limited amount of RAM
              and no virtual memory, you might want to preserve memory
              by setting <c><anno>Number</anno></c> to zero.
              (The value can be set globally, see
              <seealso marker="#system_flag/2">
              <c>erlang:system_flag/2</c></seealso>.)
              </item>
            </list>
          </item>
          <tag><c>{min_heap_size, <anno>Size</anno>}</c></tag>
          <item>
            <p>Useful only for performance tuning. Do not use this
              option unless you know that there is problem with
              execution times or memory consumption, and
              ensure that the option improves matters.</p>
            <p>Gives a minimum heap size, in words. Setting this value
              higher than the system default can speed up some
              processes because less garbage collection is done.
              However, setting a too high value can waste memory and
              slow down the system because of worse data locality.
              Therefore, use this option only for
              fine-tuning an application and to measure the execution
              time with various <c><anno>Size</anno></c> values.</p>
          </item>
          <tag><c>{min_bin_vheap_size, <anno>VSize</anno>}</c></tag>
          <item>
            <p>Useful only for performance tuning. Do not use this
              option unless you know that there is problem with
              execution times or memory consumption, and
              ensure that the option improves matters.</p>
            <p>Gives a minimum binary virtual heap size, in words.
              Setting this value
              higher than the system default can speed up some
              processes because less garbage collection is done.
              However, setting a too high value can waste memory.
              Therefore, use this option only for
              fine-tuning an application and to measure the execution
              time with various <c><anno>VSize</anno></c> values.</p>
          </item>
          <tag><c>{max_heap_size, <anno>Size</anno>}</c></tag>
          <item>
            <p>Sets the <c>max_heap_size</c> process flag. The default
              <c>max_heap_size</c> is determined by command-line argument
              <seealso marker="erl#+hmax"><c>+hmax</c></seealso>
              in <c>erl(1)</c>. For more information, see the
              documentation of <seealso marker="#process_flag_max_heap_size">
              <c>process_flag(max_heap_size, <anno>Size</anno>)</c></seealso>.
            </p>
          </item>
          <tag><c>{message_queue_data, <anno>MQD</anno>}</c></tag>
          <item>
            <p>Sets the state of the <c>message_queue_data</c> process
              flag. <c><anno>MQD</anno></c> is to be either <c>off_heap</c>
              or <c>on_heap</c>. The default
              <c>message_queue_data</c> process flag is determined by
              command-line argument <seealso marker="erl#+hmqd">
              <c>+hmqd</c></seealso> in <c>erl(1)</c>.
              For more information, see the documentation of
              <seealso marker="#process_flag_message_queue_data">
              <c>process_flag(message_queue_data,
              <anno>MQD</anno>)</c></seealso>.</p>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="spawn_opt" arity="5"/>
      <fsummary>Create a new process with a function as entry point on a
        specified node.</fsummary>
      <type name="priority_level"/>
      <type name="max_heap_size"/>
      <type name="message_queue_data"/>
      <type name="spawn_opt_option"/>
      <desc>
        <p>Returns the process identifier (pid) of a new process started
          by the application
          of <c><anno>Module</anno>:<anno>Function</anno></c> to
          <c><anno>Args</anno></c> on <c><anno>Node</anno></c>. If
          <c><anno>Node</anno></c> does not exist, a useless pid is returned.
          Otherwise works like
          <seealso marker="#spawn_opt/4"><c>spawn_opt/4</c></seealso>.</p>
        <note>
          <p>Option <c>monitor</c> is not supported by
            <c>spawn_opt/5</c>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="split_binary" arity="2"/>
      <fsummary>Split a binary into two.</fsummary>
      <type_desc variable="Pos">0..byte_size(Bin)</type_desc>
      <desc>
        <p>Returns a tuple containing the binaries that are the result
          of splitting <c><anno>Bin</anno></c> into two parts at
          position <c><anno>Pos</anno></c>.
          This is not a destructive operation. After the operation,
          there are three binaries altogether. Example:</p>
        <pre>
> <input>B = list_to_binary("0123456789").</input>
&lt;&lt;"0123456789">>
> <input>byte_size(B).</input>
10
> <input>{B1, B2} = split_binary(B,3).</input>
{&lt;&lt;"012">>,&lt;&lt;"3456789">>}
> <input>byte_size(B1).</input>
3
> <input>byte_size(B2).</input>
7</pre>
      </desc>
    </func>

    <func>
      <name name="start_timer" arity="3"/>
      <fsummary>Start a timer.</fsummary>
      <desc>
        <p>Starts a timer. The same as calling
          <seealso marker="#start_timer/4">
          <c>erlang:start_timer(<anno>Time</anno>,
          <anno>Dest</anno>, <anno>Msg</anno>, [])</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="start_timer" arity="4"/>
      <fsummary>Start a timer.</fsummary>
      <desc>
        <p>Starts a timer. When the timer expires, the message
          <c>{timeout, <anno>TimerRef</anno>, <anno>Msg</anno>}</c>
          is sent to the process identified by <c><anno>Dest</anno></c>.</p>
        <p><c><anno>Option</anno></c>s:</p>
        <taglist>
          <tag><c>{abs, false}</c></tag>
          <item>
            <p>This is the default. It means the
              <c><anno>Time</anno></c> value is interpreted
              as a time in milliseconds <em>relative</em> current
              <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
              monotonic time</seealso>.</p>
          </item>
          <tag><c>{abs, true}</c></tag>
          <item>
            <p>Absolute <c><anno>Time</anno></c> value. The
              <c><anno>Time</anno></c> value is interpreted as an
              absolute Erlang monotonic time in milliseconds.</p>
          </item>
        </taglist>
        <p>More <c><anno>Option</anno></c>s can be added in the future.</p>
        <p>The absolute point in time, the timer is set to expire on,
          must be in the interval
          <c>[</c><seealso marker="#system_info_start_time">
          <c>erlang:system_info(start_time)</c></seealso><c>,
          </c><seealso marker="#system_info_end_time">
          <c>erlang:system_info(end_time)</c></seealso><c>]</c>.
          If a relative time is specified, the <c><anno>Time</anno></c>
          value is not allowed to be negative.</p>
        <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, it must
          be a <c>pid()</c> of a process created on the current
          runtime system instance. This process has either terminated
          or not. If <c><anno>Dest</anno></c> is an
          <c>atom()</c>, it is interpreted as the name of a
          locally registered process. The process referred to by the
          name is looked up at the time of timer expiration. No error
          is returned if the name does not refer to a process.</p>
        <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer is
          automatically canceled if the process referred to by the
          <c>pid()</c> is not alive, or if the process exits. This
          feature was introduced in ERTS 5.4.11. Notice that
          timers are not automatically canceled when
          <c><anno>Dest</anno></c> is an <c>atom()</c>.</p>
        <p>See also
          <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>,
          <seealso marker="#cancel_timer/2">
          <c>erlang:cancel_timer/2</c></seealso>, and
          <seealso marker="#read_timer/2">
          <c>erlang:read_timer/2</c></seealso>.</p>
        <p>Failure: <c>badarg</c> if the arguments do not satisfy
          the requirements specified here.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="1"
	    anchor="statistics_active_tasks"/>
      <fsummary>Information about active processes and ports.</fsummary>
      <desc>
        <p>Returns the same as
	<seealso marker="#statistics_active_tasks_all">
        <c>statistics(active_tasks_all)</c></seealso>
	with the exception that no information about the dirty
	IO run queue and its associated schedulers is part of
	the result. That is, only tasks that are expected to be
	CPU bound are part of the result.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="2"
	    anchor="statistics_active_tasks_all"/>
      <fsummary>Information about active processes and ports.</fsummary>
      <desc>
        <p>Returns a list where each element represents the amount
          of active processes and ports on each run queue and its
          associated schedulers. That is, the number of processes and
          ports that are ready to run, or are currently running.
	  Values for normal run queues and their associated schedulers
	  are located first in the resulting list. The first element
	  corresponds to scheduler number 1 and so on. If support for
	  dirty schedulers exist, an element with the value for the
	  dirty CPU run queue and its associated dirty CPU schedulers
	  follow and then as last element the value for the the dirty
	  IO run queue and its associated dirty IO schedulers follow.
	  The information is <em>not</em> gathered atomically. That is,
	  the result is not necessarily a consistent snapshot of the
	  state, but instead quite efficiently gathered.</p>
	<note><p>Each normal scheduler has one run queue that it
	manages. If dirty schedulers schedulers are supported, all
	dirty CPU schedulers share one run queue, and all dirty IO
	schedulers share one run queue. That is, we have multiple
	normal run queues, one dirty CPU run queue and one dirty
	IO run queue. Work can <em>not</em> migrate between the
	different types of run queues. Only work in normal run
	queues can migrate to other normal run queues. This has
	to be taken into account when evaluating the result.</p></note>
        <p>See also
          <seealso marker="#statistics_total_active_tasks">
          <c>statistics(total_active_tasks)</c></seealso>,
          <seealso marker="#statistics_run_queue_lengths">
          <c>statistics(run_queue_lengths)</c></seealso>,
          <seealso marker="#statistics_run_queue_lengths_all">
          <c>statistics(run_queue_lengths_all)</c></seealso>,
          <seealso marker="#statistics_total_run_queue_lengths">
          <c>statistics(total_run_queue_lengths)</c></seealso>, and
          <seealso marker="#statistics_total_run_queue_lengths_all">
          <c>statistics(total_run_queue_lengths_all)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="3"/>
      <fsummary>Information about context switches.</fsummary>
      <desc>
        <p>Returns the total number of context switches since the
          system started.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="4"
	    anchor="statistics_exact_reductions"/>
      <fsummary>Information about exact reductions.</fsummary>
      <desc>
        <p>Returns the number of exact reductions.</p>
        <note>
          <p><c>statistics(exact_reductions)</c> is
            a more expensive operation than
            <seealso marker="#statistics_reductions">
            statistics(reductions)</seealso>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="5"/>
      <fsummary>Information about garbage collection.</fsummary>
      <desc>
        <p>Returns information about garbage collection, for example:</p>
        <pre>
> <input>statistics(garbage_collection).</input>
{85,23961,0}</pre>
        <p>This information can be invalid for some implementations.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="6"/>
      <fsummary>Information about I/O.</fsummary>
      <desc>
        <p>Returns <c><anno>Input</anno></c>,
          which is the total number of bytes
          received through ports, and <c><anno>Output</anno></c>,
          which is the total number of bytes output to ports.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="7"
	    anchor="statistics_microstate_accounting"/>
      <fsummary>Information about microstate accounting.</fsummary>
      <desc>
        <p>Microstate accounting can be used to measure how much time the Erlang
          runtime system spends doing various tasks. It is designed to be as
          lightweight as possible, but some overhead exists when this
          is enabled. Microstate accounting is meant to be a profiling tool
          to help finding performance bottlenecks.
          To <c>start</c>/<c>stop</c>/<c>reset</c> microstate accounting, use
          system flag <seealso marker="#system_flag_microstate_accounting">
          <c>microstate_accounting</c></seealso>.</p>
        <p><c>statistics(microstate_accounting)</c> returns a list of maps
          representing some of the OS threads within ERTS. Each map
          contains <c>type</c> and <c>id</c> fields that can be used to
          identify what
          thread it is, and also a counters field that contains data about how
          much time has been spent in the various states.</p>
        <p>Example:</p>
        <pre>
> <input>erlang:statistics(microstate_accounting).</input>
[#{counters => #{aux => 1899182914,
                 check_io => 2605863602,
                 emulator => 45731880463,
                 gc => 1512206910,
                 other => 5421338456,
                 port => 221631,
                 sleep => 5150294100},
   id => 1,
   type => scheduler}|...]</pre>
        <p>The time unit is the same as returned by
          <seealso marker="kernel:os#perf_counter/0">
          <c>os:perf_counter/0</c></seealso>.
          So, to convert it to milliseconds, you can do something like this:</p>
        <pre>
lists:map(
  fun(#{ counters := Cnt } = M) ->
          MsCnt = maps:map(fun(_K, PerfCount) ->
                                   erlang:convert_time_unit(PerfCount, perf_counter, 1000)
                           end, Cnt),
         M#{ counters := MsCnt }
  end, erlang:statistics(microstate_accounting)).</pre>
        <p>Notice that these values are not guaranteed to be
          the exact time spent in each state. This is because of various
          optimisation done to keep the overhead as small as possible.</p>
        <p><c><anno>MSAcc_Thread_Type</anno></c>s:</p>
        <taglist>
          <tag><c>scheduler</c></tag>
          <item>The main execution threads that do most of the work. See
            <seealso marker="erts:erl#+S">erl +S</seealso> for more details.</item>
          <tag><c>dirty_cpu_scheduler</c></tag>
          <item>The threads for long running cpu intensive work. See
            <seealso marker="erts:erl#+SDcpu">erl +SDcpu</seealso> for more details.</item>
          <tag><c>dirty_io_scheduler</c></tag>
          <item>The threads for long running I/O work. See
            <seealso marker="erts:erl#+SDio">erl +SDio</seealso> for more details.</item>
          <tag><c>async</c></tag>
          <item>Async threads are used by various linked-in drivers (mainly the
            file drivers) do offload non-CPU intensive work. See
            <seealso marker="erts:erl#+async_thread_pool_size">erl +A</seealso> for more details.</item>
          <tag><c>aux</c></tag>
          <item>Takes care of any work that is not
            specifically assigned to a scheduler.</item>
          <tag><c>poll</c></tag>
          <item>Does the IO polling for the emulator. See
            <seealso marker="erts:erl#+IOt">erl +IOt</seealso> for more details.</item>
        </taglist>
        <p>The following <c><anno>MSAcc_Thread_State</anno></c>s are available.
          All states are exclusive, meaning that a thread cannot be in two
          states at once. So, if you add the numbers of all counters in a
          thread, you get the total runtime for that thread.</p>
        <taglist>
          <tag><c>aux</c></tag>
          <item>Time spent handling auxiliary jobs.</item>
          <tag><c>check_io</c></tag>
          <item>Time spent checking for new I/O events.</item>
          <tag><c>emulator</c></tag>
          <item>Time spent executing Erlang processes.</item>
          <tag><c>gc</c></tag>
          <item>Time spent doing garbage collection. When extra states are
            enabled this is the time spent doing non-fullsweep garbage
            collections.</item>
          <tag><c>other</c></tag>
          <item>Time spent doing unaccounted things.</item>
          <tag><c>port</c></tag>
          <item>Time spent executing ports.</item>
          <tag><c>sleep</c></tag>
          <item>Time spent sleeping.</item>
        </taglist>
        <p>More fine-grained <c><anno>MSAcc_Thread_State</anno></c>s can
          be added through configure (such as
          <c>./configure --with-microstate-accounting=extra</c>).
          Enabling these states causes performance degradation when
          microstate accounting is turned off and increases the overhead when
          it is turned on.</p>
        <taglist>
          <tag><c>alloc</c></tag>
          <item>Time spent managing memory. Without extra states this time is
            spread out over all other states.</item>
          <tag><c>bif</c></tag>
          <item>Time spent in BIFs. Without extra states this time is part of
            the <c>emulator</c> state.</item>
          <tag><c>busy_wait</c></tag>
          <item>Time spent busy waiting. This is also the state where a
            scheduler no longer reports that it is active when using
            <seealso marker="#statistics_scheduler_wall_time">
            <c>statistics(scheduler_wall_time)</c></seealso>. So, if you add
            all other states but this and sleep, and then divide that by all
            time in the thread, you should get something very similar to the
            <c>scheduler_wall_time</c> fraction. Without extra states this
            time is part of the <c>other</c> state.</item>
          <tag><c>ets</c></tag>
          <item>Time spent executing ETS BIFs. Without extra states
            this time is part of the <c>emulator</c> state.</item>
          <tag><c>gc_full</c></tag>
          <item>Time spent doing fullsweep garbage collection. Without extra
            states this time is part of the <c>gc</c> state.</item>
          <tag><c>nif</c></tag>
          <item>Time spent in NIFs. Without extra states this time is part of
            the <c>emulator</c> state.</item>
          <tag><c>send</c></tag>
          <item>Time spent sending messages (processes only). Without extra
            states this time is part of the <c>emulator</c> state.</item>
          <tag><c>timers</c></tag>
          <item>Time spent managing timers. Without extra states this time is
            part of the <c>other</c> state.</item>
        </taglist>
        <p>The utility module
          <seealso marker="runtime_tools:msacc"><c>msacc(3)</c></seealso>
          can be used to more easily analyse these statistics.</p>
        <p>Returns <c>undefined</c> if system flag
          <seealso marker="#system_flag_microstate_accounting">
          <c>microstate_accounting</c></seealso> is turned off.</p>
        <p>The list of thread information is unsorted and can appear in
          different order between calls.</p>
        <note>
          <p>The threads and states are subject to change without any
            prior notice.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="8"
	    anchor="statistics_reductions"/>
      <fsummary>Information about reductions.</fsummary>
      <desc>
        <p>Returns information about reductions, for example:</p>
        <pre>
> <input>statistics(reductions).</input>
{2046,11}</pre>
        <note><p>As from ERTS 5.5 (Erlang/OTP R11B),
          this value does not include reductions performed in current
          time slices of currently scheduled processes. If an
          exact value is wanted, use
          <seealso marker="#statistics_exact_reductions">
          <c>statistics(exact_reductions)</c></seealso>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="9"
	    anchor="statistics_run_queue"/>
      <fsummary>Information about the run-queues.</fsummary>
      <desc>
        <p>Returns the total length of all normal run-queues. That is, the number
          of processes and ports that are ready to run on all available
          normal run-queues. Dirty run queues are not part of the
	  result. The information is gathered atomically. That
          is, the result is a consistent snapshot of the state, but
          this operation is much more expensive compared to
          <seealso marker="#statistics_total_run_queue_lengths">
          <c>statistics(total_run_queue_lengths)</c></seealso>,
          especially when a large amount of schedulers is used.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="10"
	    anchor="statistics_run_queue_lengths"/>
      <fsummary>Information about the run-queue lengths.</fsummary>
      <desc>
        <p>Returns the same as
	<seealso marker="#statistics_run_queue_lengths_all">
        <c>statistics(run_queue_lengths_all)</c></seealso>
	with the exception that no information about the dirty
	IO run queue is part of the result. That is, only
	run queues with work that is expected to be CPU bound
	is part of the result.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="11"
	    anchor="statistics_run_queue_lengths_all"/>
      <fsummary>Information about the run-queue lengths.</fsummary>
      <desc>
        <p>Returns a list where each element represents the amount
          of processes and ports ready to run for each run queue.
	  Values for normal run queues are located first in the
	  resulting list. The first element corresponds to the
	  normal run queue of scheduler number 1 and so on. If
	  support for dirty schedulers exist, values for the dirty
	  CPU run queue and the dirty IO run queue follow (in that
	  order) at the end. The information is <em>not</em>
	  gathered atomically. That is, the result is not
	  necessarily a consistent snapshot of the state, but
	  instead quite efficiently gathered.</p>
	<note><p>Each normal scheduler has one run queue that it
	manages. If dirty schedulers schedulers are supported, all
	dirty CPU schedulers share one run queue, and all dirty IO
	schedulers share one run queue. That is, we have multiple
	normal run queues, one dirty CPU run queue and one dirty
	IO run queue. Work can <em>not</em> migrate between the
	different types of run queues. Only work in normal run
	queues can migrate to other normal run queues. This has
	to be taken into account when evaluating the result.</p></note>
        <p>See also
          <seealso marker="#statistics_run_queue_lengths">
          <c>statistics(run_queue_lengths)</c></seealso>,
          <seealso marker="#statistics_total_run_queue_lengths_all">
          <c>statistics(total_run_queue_lengths_all)</c></seealso>,
          <seealso marker="#statistics_total_run_queue_lengths">
          <c>statistics(total_run_queue_lengths)</c></seealso>,
          <seealso marker="#statistics_active_tasks">
          <c>statistics(active_tasks)</c></seealso>,
          <seealso marker="#statistics_active_tasks_all">
          <c>statistics(active_tasks_all)</c></seealso>, and
          <seealso marker="#statistics_total_active_tasks">
          <c>statistics(total_active_tasks)</c></seealso>,
          <seealso marker="#statistics_total_active_tasks_all">
          <c>statistics(total_active_tasks_all)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="12"/>
      <fsummary>Information about runtime.</fsummary>
      <desc>
        <p>Returns information about runtime, in milliseconds.</p>
        <p>This is the sum of the runtime for all threads
          in the Erlang runtime system and can therefore be greater
          than the wall clock time.</p>
          <warning><p>This value might wrap due to limitations in the
          underlying functionality provided by the operating system
          that is used.</p></warning>
        <p>Example:</p>
        <pre>
> <input>statistics(runtime).</input>
{1690,1620}</pre>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="13"
	    anchor="statistics_scheduler_wall_time"/>
      <fsummary>Information about each schedulers work time.</fsummary>
      <desc>
        <p>Returns a list of tuples with
          <c>{<anno>SchedulerId</anno>, <anno>ActiveTime</anno>,
          <anno>TotalTime</anno>}</c>, where
          <c><anno>SchedulerId</anno></c> is an integer ID of the scheduler,
          <c><anno>ActiveTime</anno></c> is
          the duration the scheduler has been busy, and
          <c><anno>TotalTime</anno></c> is the total time duration since
          <seealso marker="#system_flag_scheduler_wall_time">
          <c>scheduler_wall_time</c></seealso>
          activation for the specific scheduler. Note that
	  activation time can differ significantly between
	  schedulers. Currently dirty schedulers are activated
	  at system start while normal schedulers are activated
	  some time after the <c>scheduler_wall_time</c>
	  functionality is enabled. The time unit is undefined
	  and can be subject to change between releases, OSs,
	  and system restarts. <c>scheduler_wall_time</c> is only
	  to be used to calculate relative values for scheduler
	  utilization. <c><anno>ActiveTime</anno></c> can never
	  exceed <c><anno>TotalTime</anno></c>.</p>
        <p>The definition of a busy scheduler is when it is not idle
          and is not scheduling (selecting) a process or port,
          that is:</p>
        <list type="bulleted">
          <item>Executing process code</item>
          <item>Executing linked-in driver or NIF code</item>
          <item>Executing BIFs, or any other runtime handling</item>
          <item>Garbage collecting</item>
          <item>Handling any other memory management</item>
        </list>
        <p>Notice that a scheduler can also be busy even if the
          OS has scheduled out the scheduler thread.</p>
        <p>Returns <c>undefined</c> if system flag
          <seealso marker="#system_flag_scheduler_wall_time">
          <c>scheduler_wall_time</c></seealso> is turned off.</p>
        <p>The list of scheduler information is unsorted and can
          appear in different order between calls.</p>
	<p>As of ERTS version 9.0, also dirty CPU schedulers will
	be included in the result. That is, all scheduler threads
	that are expected to handle CPU bound work. If you also
	want information about dirty I/O schedulers, use
	<seealso marker="#statistics_scheduler_wall_time_all"><c>statistics(scheduler_wall_time_all)</c></seealso>
	instead.</p>
	
	<p>Normal schedulers will have scheduler identifiers in
	the range <c>1 =&lt; <anno>SchedulerId</anno> =&lt;
	</c><seealso marker="#system_info_schedulers"><c>erlang:system_info(schedulers)</c></seealso>.
	Dirty CPU schedulers will have scheduler identifiers in
	the range <c>erlang:system_info(schedulers) &lt;
	<anno>SchedulerId</anno> =&lt; erlang:system_info(schedulers)
	+
	</c><seealso marker="#system_info_dirty_cpu_schedulers"><c>erlang:system_info(dirty_cpu_schedulers)</c></seealso>.
	</p>
	<note><p>The different types of schedulers handle
	specific types of jobs. Every job is assigned to a specific
	scheduler type. Jobs can migrate between different schedulers
	of the same type, but never between schedulers of different
	types. This fact has to be taken under consideration when
	evaluating the result returned.</p></note>
        <p>Using <c>scheduler_wall_time</c> to calculate
          scheduler utilization:</p>
        <pre>
> <input>erlang:system_flag(scheduler_wall_time, true).</input>
false
> <input>Ts0 = lists:sort(erlang:statistics(scheduler_wall_time)), ok.</input>
ok</pre>
        <p>Some time later the user takes another snapshot and calculates
          scheduler utilization per scheduler, for example:</p>
        <pre>
> <input>Ts1 = lists:sort(erlang:statistics(scheduler_wall_time)), ok.</input>
ok
> <input>lists:map(fun({{I, A0, T0}, {I, A1, T1}}) ->
	{I, (A1 - A0)/(T1 - T0)} end, lists:zip(Ts0,Ts1)).</input>
[{1,0.9743474730177548},
 {2,0.9744843782751444},
 {3,0.9995902361669045},
 {4,0.9738012596572161},
 {5,0.9717956667018103},
 {6,0.9739235846420741},
 {7,0.973237033077876},
 {8,0.9741297293248656}]</pre>
        <p>Using the same snapshots to calculate a total
          scheduler utilization:</p>
        <pre>
> <input>{A, T} = lists:foldl(fun({{_, A0, T0}, {_, A1, T1}}, {Ai,Ti}) ->
	{Ai + (A1 - A0), Ti + (T1 - T0)} end, {0, 0}, lists:zip(Ts0,Ts1)),
	TotalSchedulerUtilization = A/T.</input>
0.9769136803764825</pre>
        <p>Total scheduler utilization will equal <c>1.0</c> when
	all schedulers have been active all the time between the
	two measurements.</p>
	<p>Another (probably more) useful value is to calculate
	total scheduler utilization weighted against maximum amount
	of available CPU time:</p>
        <pre>
> <input>WeightedSchedulerUtilization = (TotalSchedulerUtilization
                                  * (erlang:system_info(schedulers)
                                     + erlang:system_info(dirty_cpu_schedulers)))
                                 / erlang:system_info(logical_processors_available).</input>
0.9769136803764825</pre>
        <p>This weighted scheduler utilization will reach <c>1.0</c>
	when schedulers are active the same amount of time as
	maximum available CPU time. If more schedulers exist
	than available logical processors, this value may
	be greater than <c>1.0</c>.</p>
	<p>As of ERTS version 9.0, the Erlang runtime system
        will as default have more schedulers than logical processors.
        This due to the dirty schedulers.</p>
        <note>
          <p><c>scheduler_wall_time</c> is by default disabled. To
            enable it, use
            <c>erlang:system_flag(scheduler_wall_time, true)</c>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="14"
	    anchor="statistics_scheduler_wall_time_all"/>
      <fsummary>Information about each schedulers work time.</fsummary>
      <desc>
	<p>The same as
	<seealso marker="#statistics_scheduler_wall_time"><c>statistics(scheduler_wall_time)</c></seealso>,
	except that it also include information about all dirty I/O
	schedulers.</p>
	<p>Dirty IO schedulers will have scheduler identifiers in
	the range
	<seealso marker="#system_info_schedulers"><c>erlang:system_info(schedulers)</c></seealso><c>
	+
	</c><seealso marker="#system_info_dirty_cpu_schedulers"><c>erlang:system_info(dirty_cpu_schedulers)</c></seealso><c> &lt;
	<anno>SchedulerId</anno> =&lt; erlang:system_info(schedulers)
	+ erlang:system_info(dirty_cpu_schedulers)
	+
	</c><seealso marker="#system_info_dirty_io_schedulers"><c>erlang:system_info(dirty_io_schedulers)</c></seealso>.</p>
	<note><p>Note that work executing on dirty I/O schedulers
	are expected to mainly wait for I/O. That is, when you
	get high scheduler utilization on dirty I/O schedulers,
	CPU utilization is <em>not</em> expected to be high due to
	this work.</p></note>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="15"
	    anchor="statistics_total_active_tasks"/>
      <fsummary>Information about active processes and ports.</fsummary>
      <desc>
        <p>The same as calling
	<c>lists:sum(</c><seealso marker="#statistics_active_tasks"><c>statistics(active_tasks)</c></seealso><c>)</c>,
	but more efficient.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="16"
	    anchor="statistics_total_active_tasks_all"/>
      <fsummary>Information about active processes and ports.</fsummary>
      <desc>
        <p>The same as calling
	<c>lists:sum(</c><seealso marker="#statistics_active_tasks_all"><c>statistics(active_tasks_all)</c></seealso><c>)</c>,
	but more efficient.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="17"
	    anchor="statistics_total_run_queue_lengths"/>
      <fsummary>Information about the run-queue lengths.</fsummary>
      <desc>
        <p>The same as calling
	<c>lists:sum(</c><seealso marker="#statistics_run_queue_lengths"><c>statistics(run_queue_lengths)</c></seealso><c>)</c>,
	but more efficient.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="18"
	    anchor="statistics_total_run_queue_lengths_all"/>
      <fsummary>Information about the run-queue lengths.</fsummary>
      <desc>
        <p>The same as calling
	<c>lists:sum(</c><seealso marker="#statistics_run_queue_lengths_all"><c>statistics(run_queue_lengths_all)</c></seealso><c>)</c>,
	but more efficient.</p>
      </desc>
    </func>

    <func>
      <name name="statistics" arity="1" clause_i="19"/>
      <fsummary>Information about wall clock.</fsummary>
      <desc>
        <p>Returns information about wall clock. <c>wall_clock</c> can
          be used in the same manner as
          <c>runtime</c>, except that real time is measured as
          opposed to runtime or CPU time.</p>
      </desc>
    </func>

    <func>
      <name name="suspend_process" arity="1"/>
      <fsummary>Suspend a process.</fsummary>
      <desc>
        <p>Suspends the process identified by
          <c><anno>Suspendee</anno></c>. The same as calling
          <seealso marker="#suspend_process/2">
          <c>erlang:suspend_process(<anno>Suspendee</anno>,
          [])</c></seealso>.</p>
        <warning>
          <p>This BIF is intended for debugging only.</p>
        </warning>
      </desc>
    </func>

    <func>
      <name name="suspend_process" arity="2"/>
      <fsummary>Suspend a process.</fsummary>
      <desc>
        <p>Increases the suspend count on the process identified by
          <c><anno>Suspendee</anno></c> and puts it in the suspended
          state if it is not
          already in that state. A suspended process is not
          scheduled for execution until the process has been resumed.</p>
        <p>A process can be suspended by multiple processes and can
          be suspended multiple times by a single process. A suspended
          process does not leave the suspended state until its suspend 
          count reaches zero. The suspend count of
          <c><anno>Suspendee</anno></c> is decreased when
          <seealso marker="#resume_process/1">
          <c>erlang:resume_process(<anno>Suspendee</anno>)</c></seealso>
          is called by the same process that called
          <c>erlang:suspend_process(<anno>Suspendee</anno>)</c>.
          All increased suspend
          counts on other processes acquired by a process are automatically
          decreased when the process terminates.</p>
        <p>Options (<c><anno>Opt</anno></c>s):</p>
        <taglist>
          <tag><c>asynchronous</c></tag>
          <item>
            <p>A suspend request is sent to the process identified by
              <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c>
              eventually suspends
              unless it is resumed before it could suspend. The caller
              of <c>erlang:suspend_process/2</c> returns immediately,
              regardless of whether <c><anno>Suspendee</anno></c> has
              suspended yet or not. The point in time when
              <c><anno>Suspendee</anno></c> suspends cannot be deduced
              from other events in the system. It is only guaranteed that
              <c><anno>Suspendee</anno></c> <em>eventually</em> suspends
              (unless it
              is resumed). If option <c>asynchronous</c> has <em>not</em>
              been passed, the caller of <c>erlang:suspend_process/2</c> is
              blocked until <c><anno>Suspendee</anno></c> has suspended.</p>
          </item>
          <tag><c>unless_suspending</c></tag>
          <item>
            <p>The process identified by <c><anno>Suspendee</anno></c> is
              suspended unless the calling process already is suspending
              <c><anno>Suspendee</anno></c>.
              If <c>unless_suspending</c> is combined
              with option <c>asynchronous</c>, a suspend request is
              sent unless the calling process already is suspending
              <c><anno>Suspendee</anno></c> or if a suspend request
              already has been sent and is in transit. If the calling
              process already is suspending <c><anno>Suspendee</anno></c>,
              or if combined with option <c>asynchronous</c>
              and a send request already is in transit,
              <c>false</c> is returned and the suspend count on
              <c><anno>Suspendee</anno></c> remains unchanged.</p>
          </item>
        </taglist>
        <p>If the suspend count on the process identified by
          <c><anno>Suspendee</anno></c> is increased, <c>true</c>
          is returned, otherwise <c>false</c>.</p>
        <warning>
          <p>This BIF is intended for debugging only.</p>
        </warning>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>Suspendee</anno></c> is not a process identifier.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the process identified by <c><anno>Suspendee</anno></c>
            is the same process
            as the process calling <c>erlang:suspend_process/2</c>.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the process identified by <c><anno>Suspendee</anno></c>
            is not alive.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If the process identified by <c><anno>Suspendee</anno></c>
            resides on another node.
          </item>
          <tag><c>badarg</c></tag>
          <item>
            If <c><anno>OptList</anno></c> is not a proper list of valid
            <c><anno>Opt</anno></c>s.
          </item>
          <tag><c>system_limit</c></tag>
          <item>
            If the process identified by <c><anno>Suspendee</anno></c>
            has been suspended
            more times by the calling process than can be represented by the
            currently used internal data structures. The system limit is
            &gt; 2,000,000,000 suspends and will never be lower.
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="1"/>
      <fsummary>Set system flag <c>backtrace_depth</c>.</fsummary>
      <desc>
        <p>Sets the maximum depth of call stack back-traces in the
          exit reason element of <c>'EXIT'</c> tuples. The flag
          also limits the stacktrace depth returned by <c>process_info</c>
          item <c>current_stacktrace.</c></p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="2"
	    anchor="system_flag_cpu_topology"/>
      <fsummary>Set system flag <c>cpu_topology</c>.</fsummary>
      <type name="cpu_topology"/>
      <type name="level_entry"/>
      <type name="level_tag"/>
      <type name="sub_level"/>
      <type name="info_list"/>
      <desc>
        <warning>
          <p>
            <em>This argument is deprecated.</em>
            Instead of using this argument, use command-line argument
            <seealso marker="erts:erl#+sct"><c>+sct</c></seealso> in
            <c>erl(1)</c>.</p>
          <p>When this argument is removed, a final CPU topology
            to use is determined at emulator boot time.</p>
        </warning>
        <p>Sets the user-defined <c><anno>CpuTopology</anno></c>.
          The user-defined
          CPU topology overrides any automatically detected
          CPU topology. By passing <c>undefined</c> as
          <c><anno>CpuTopology</anno></c>,
          the system reverts to the CPU topology automatically
          detected. The returned value equals the value returned
          from <c>erlang:system_info(cpu_topology)</c> before the
          change was made.</p>
        <p>Returns the old value of the flag.</p>
        <p>The CPU topology is used when binding schedulers to logical
          processors. If schedulers are already bound when the CPU
          topology is changed, the schedulers are sent a request
          to rebind according to the new CPU topology.</p>
        <p>The user-defined CPU topology can also be set by passing
          command-line argument
          <seealso marker="erts:erl#+sct"><c>+sct</c></seealso> to
          <c>erl(1)</c>.</p>
        <p>For information on type <c><anno>CpuTopology</anno></c>
          and more, see
          <seealso marker="#system_info_cpu_topology">
          <c>erlang:system_info(cpu_topology)</c></seealso>
          as well as command-line flags
          <seealso marker="erts:erl#+sct"><c>+sct</c></seealso> and
          <seealso marker="erts:erl#+sbt"><c>+sbt</c></seealso> in
          <c>erl(1)</c>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="3"
	    anchor="system_flag_dirty_cpu_schedulers_online"/>
      <fsummary>Set system_flag_dirty_cpu_schedulers_online.</fsummary>
      <desc>
        <p>
          Sets the number of dirty CPU schedulers online. Range is
          <c><![CDATA[1 <= DirtyCPUSchedulersOnline <= N]]></c>, where <c>N</c>
          is the smallest of the return values of
          <c>erlang:system_info(dirty_cpu_schedulers)</c> and
          <c>erlang:system_info(schedulers_online)</c>.</p>
        <p>Returns the old value of the flag.</p>
        <p>The number of dirty CPU schedulers online can change if the
          number of schedulers online changes. For example, if 12
          schedulers and 6 dirty CPU schedulers are online, and
          <c>system_flag/2</c> is used to set the number of
          schedulers online to 6, then the number of dirty CPU
          schedulers online is automatically decreased by half as well,
          down to 3. Similarly, the number of dirty CPU schedulers
          online increases proportionally to increases in the number of
          schedulers online.</p>
        <p>For more information, see
          <seealso marker="#system_info_dirty_cpu_schedulers">
          <c>erlang:system_info(dirty_cpu_schedulers)</c></seealso> and
          <seealso marker="#system_info_dirty_cpu_schedulers_online">
          <c>erlang:system_info(dirty_cpu_schedulers_online)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="4"/>
      <fsummary>Set system flag fullsweep_after.</fsummary>
      <desc>
        <p>Sets system flag <c>fullsweep_after</c>.
          <c><anno>Number</anno></c> is a non-negative integer indicating
          how many times generational garbage collections can be
          done without forcing a fullsweep collection. The value
          applies to new processes, while processes already running are
          not affected.</p>
        <p>Returns the old value of the flag.</p>
        <p>In low-memory systems (especially without virtual
          memory), setting the value to <c>0</c> can help to conserve
          memory.</p>
        <p>This value can also be set through (OS)
          environment variable <c>ERL_FULLSWEEP_AFTER</c>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="5"
	    anchor="system_flag_microstate_accounting"/>
      <fsummary>Set system flag microstate_accounting.</fsummary>
      <desc>
        <p>
          Turns on/off microstate accounting measurements. When passing reset,
          all counters are reset to 0.</p>
        <p>For more information see
          <seealso marker="#statistics_microstate_accounting">
          <c>statistics(microstate_accounting)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="6"/>
      <fsummary>Set system flag min_heap_size.</fsummary>
      <desc>
        <p>Sets the default minimum heap size for processes. The size
          is specified in words. The new <c>min_heap_size</c> effects
          only processes spawned after the change of
          <c>min_heap_size</c> has been made. <c>min_heap_size</c>
          can be set for individual processes by using
          <seealso marker="#spawn_opt/4"><c>spawn_opt/4</c></seealso> or
          <seealso marker="#process_flag/2"><c>process_flag/2</c></seealso>.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="7"/>
      <fsummary>Set system flag min_bin_vheap_size.</fsummary>
      <desc>
        <p>Sets the default minimum binary virtual heap size for
          processes. The size is specified in words.
          The new <c>min_bin_vhheap_size</c> effects only
          processes spawned after the change of
          <c>min_bin_vheap_size</c> has been made.
          <c>min_bin_vheap_size</c> can be set for individual
          processes by using
          <seealso marker="#spawn_opt/4"><c>spawn_opt/2,3,4</c></seealso> or
          <seealso marker="#process_flag/2"><c>process_flag/2</c></seealso>.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="8"
	    anchor="system_flag_max_heap_size"/>
      <fsummary>Set system flag max_heap_size.</fsummary>
      <type name="max_heap_size"/>
      <desc>
        <p>
          Sets the default maximum heap size settings for processes.
          The size is specified in words. The new <c>max_heap_size</c>
          effects only processes spawned efter the change has been made.
          <c>max_heap_size</c> can be set for individual processes using
          <seealso marker="#spawn_opt/4"><c>spawn_opt/2,3,4</c></seealso> or
          <seealso marker="#process_flag_max_heap_size">
          <c>process_flag/2</c></seealso>.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="9"
	    anchor="system_flag_multi_scheduling"/>
      <fsummary>Set system flag multi_scheduling.</fsummary>
      <desc>
        <p>
          If multi-scheduling is enabled, more than one scheduler
          thread is used by the emulator. Multi-scheduling can be
          blocked in two different ways. Either all schedulers but
          one is blocked, or all <em>normal</em> schedulers but
          one is blocked. When only normal schedulers are blocked,
          dirty schedulers are free to continue to schedule
          processes.</p>
        <p>If <c><anno>BlockState</anno> =:= block</c>, multi-scheduling is
          blocked. That is, one and only one scheduler thread will
          execute. If <c><anno>BlockState</anno> =:= unblock</c> and no one
          else blocks multi-scheduling, and this process has
          blocked only once, multi-scheduling is unblocked.</p>
        <p>If <c><anno>BlockState</anno> =:= block_normal</c>, normal
          multi-scheduling is blocked. That is, only one normal scheduler
          thread will execute, but multiple dirty schedulers can execute.
          If <c><anno>BlockState</anno> =:= unblock_normal</c> and no one
          else blocks normal multi-scheduling, and this process has
          blocked only once, normal multi-scheduling is unblocked.</p>
        <p>One process can block multi-scheduling and normal
          multi-scheduling multiple times. If a process has blocked
          multiple times, it must unblock exactly as many times as it
          has blocked before it has released its multi-scheduling
          block. If a process that has blocked multi-scheduling or normal
          multi-scheduling exits, it automatically releases its blocking
          of multi-scheduling and normal multi-scheduling.</p>
        <p>The return values are <c>disabled</c>, <c>blocked</c>,
          <c>blocked_normal</c>, or <c>enabled</c>. The returned value
          describes the state just after the call to
          <c>erlang:system_flag(multi_scheduling, <anno>BlockState</anno>)</c>
          has been made. For information about the return values, see
          <seealso marker="#system_info_multi_scheduling">
          <c>erlang:system_info(multi_scheduling)</c></seealso>.</p>
        <note><p>Blocking of multi-scheduling and normal multi-scheduling
          is normally not needed. If you feel that you need to use these
          features, consider it a few more times again. Blocking
          multi-scheduling is only to be used as a last resort, as it is
          most likely a <em>very inefficient</em> way to solve the problem.</p>
        </note>
        <p>See also
          <seealso marker="#system_info_multi_scheduling">
          <c>erlang:system_info(multi_scheduling)</c></seealso>,
          <seealso marker="#system_info_normal_multi_scheduling_blockers">
          <c>erlang:system_info(normal_multi_scheduling_blockers)</c></seealso>,
          <seealso marker="#system_info_multi_scheduling_blockers">
          <c>erlang:system_info(multi_scheduling_blockers)</c></seealso>, and
          <seealso marker="#system_info_schedulers">
          <c>erlang:system_info(schedulers)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="10"
	    anchor="system_flag_scheduler_bind_type"/>
      <fsummary>Set system flag scheduler_bind_type.</fsummary>
      <type name="scheduler_bind_type"/>
      <desc>
        <warning>
          <p>
            <em>This argument is deprecated.</em>
            Instead of using this argument, use command-line argument
            <seealso marker="erts:erl#+sbt"><c>+sbt</c></seealso> in
            <c>erl(1)</c>. When this argument is removed, a final scheduler bind
            type to use is determined at emulator boot time.</p>
        </warning>
        <p>Controls if and how schedulers are bound to logical
          processors.</p>
        <p>When <c>erlang:system_flag(scheduler_bind_type, <anno>How</anno>)</c>
          is called, an asynchronous signal is sent to all schedulers
          online, causing them to try to bind or unbind as requested.</p>
        <note><p>If a scheduler fails to bind, this is often silently
          ignored, as it is not always possible to verify valid
          logical processor identifiers. If an error is reported,
          it is reported to <c>error_logger</c>. To verify that the
          schedulers have bound as requested, call
          <seealso marker="#system_info_scheduler_bindings">
          <c>erlang:system_info(scheduler_bindings)</c></seealso>.</p>
        </note>
        <p>Schedulers can be bound on newer Linux,
          Solaris, FreeBSD, and Windows systems, but more systems will be
          supported in future releases.</p>
        <p>In order for the runtime system to be able to bind schedulers,
          the CPU topology must be known. If the runtime system fails
          to detect the CPU topology automatically, it can be defined.
          For more information on how to define the CPU topology, see
          command-line flag <seealso marker="erts:erl#+sct">
          <c>+sct</c></seealso> in <c>erl(1)</c>.</p>
        <p>The runtime system does by default <em>not</em> bind schedulers
          to logical processors.</p>
        <note><p>If the Erlang runtime system is the only OS
          process binding threads to logical processors, this
          improves the performance of the runtime system. However,
          if other OS processes (for example, another Erlang
          runtime system) also bind threads to logical processors,
          there can be a performance penalty instead. Sometimes this
          performance penalty can be severe. If so, it is recommended
          to not bind the schedulers.</p>
        </note>
        <p>Schedulers can be bound in different ways. Argument
          <c><anno>How</anno></c> determines how schedulers are
          bound and can be any of the following:</p>
        <taglist>
          <tag><c>unbound</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt u</c></seealso> in
            <c>erl(1)</c>.
          </item>
          <tag><c>no_spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt ns</c></seealso>
            in <c>erl(1)</c>.
          </item>
          <tag><c>thread_spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt ts</c></seealso>
            in <c>erl(1)</c>.
          </item>
          <tag><c>processor_spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt ps</c></seealso>
          in <c>erl(1)</c>.
          </item>
          <tag><c>spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt s</c></seealso>
            in <c>erl(1)</c>.
          </item>
          <tag><c>no_node_thread_spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt nnts</c></seealso>
            in <c>erl(1)</c>.
          </item>
          <tag><c>no_node_processor_spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt nnps</c></seealso>
            in <c>erl(1)</c>.
          </item>
          <tag><c>thread_no_node_processor_spread</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt tnnps</c></seealso>
            in <c>erl(1)</c>.
          </item>
          <tag><c>default_bind</c></tag>
          <item>Same as command-line argument
          <seealso marker="erts:erl#+sbt"><c>+sbt db</c></seealso>
            in <c>erl(1)</c>.
          </item>
        </taglist>
        <p>The returned value equals <c><anno>How</anno></c> before flag
           <c>scheduler_bind_type</c> was changed.</p>
        <p>Failures:</p>
        <taglist>
          <tag><c>notsup</c></tag>
          <item>If binding of schedulers is not supported.
          </item>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>How</anno></c> is not one of the documented
            alternatives.
          </item>
          <tag><c>badarg</c></tag>
          <item>If CPU topology information is unavailable.
          </item>
        </taglist>
        <p>The scheduler bind type can also be set by passing command-line
          argument <seealso marker="erts:erl#+sbt">
          <c>+sbt</c></seealso> to <c>erl(1)</c>.</p>
        <p>For more information, see
          <seealso marker="#system_info_scheduler_bind_type">
          <c>erlang:system_info(scheduler_bind_type)</c></seealso>,
          <seealso marker="#system_info_scheduler_bindings">
          <c>erlang:system_info(scheduler_bindings)</c></seealso>,
          as well as command-line flags
          <seealso marker="erts:erl#+sbt"><c>+sbt</c></seealso>
          and <seealso marker="erts:erl#+sct"><c>+sct</c></seealso>
          in <c>erl(1)</c>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="11"
	    anchor="system_flag_scheduler_wall_time"/>
      <fsummary>Set system flag scheduler_wall_time.</fsummary>
      <desc>
        <p>
          Turns on or off scheduler wall time measurements.</p>
        <p>For more information, see
          <seealso marker="#statistics_scheduler_wall_time">
          <c>statistics(scheduler_wall_time)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="12"
	    anchor="system_flag_schedulers_online"/>
      <fsummary>Set system flag schedulers_online.</fsummary>
      <desc>
        <p>
          Sets the number of schedulers online. Range is
          <c><![CDATA[1 <= SchedulersOnline <=
          erlang:system_info(schedulers)]]></c>.</p>
        <p>Returns the old value of the flag.</p>
        <p>If the emulator was built with support for
          <seealso marker="#system_flag_dirty_cpu_schedulers_online">
          dirty schedulers</seealso>,
          changing the number of schedulers online can also change the
          number of dirty CPU schedulers online. For example, if 12
          schedulers and 6 dirty CPU schedulers are online, and
          <c>system_flag/2</c> is used to set the number of schedulers
          online to 6, then the number of dirty CPU schedulers online
          is automatically decreased by half as well, down to 3.
          Similarly, the number of dirty CPU schedulers online increases
          proportionally to increases in the number of schedulers online.</p>
        <p>For more information, see
          <seealso marker="#system_info_schedulers">
          <c>erlang:system_info(schedulers)</c></seealso> and
          <seealso marker="#system_info_schedulers_online">
          <c>erlang:system_info(schedulers_online)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="13"/>
      <fsummary>Set system flag trace_control_word.</fsummary>
      <desc>
        <p>Sets the value of the node trace control word to
          <c><anno>TCW</anno></c>, which is to be an unsigned integer.
          For more information, see function
          <seealso marker="erts:match_spec#set_tcw"><c>set_tcw</c></seealso>
          in section "Match Specifications in Erlang" in the
          User's Guide.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>

    <func>
      <name name="system_flag" arity="2" clause_i="14"
	    anchor="system_flag_time_offset"/>
      <fsummary>Finalize the time offset.</fsummary>
      <desc>
        <p>
          Finalizes the <seealso marker="#time_offset/0">time offset</seealso>
          when <seealso marker="time_correction#Single_Time_Warp_Mode">single
          time warp mode</seealso> is used. If another time warp mode
          is used, the time offset state is left unchanged.</p>
        <p>Returns the old state identifier, that is:</p>
        <list>
          <item><p>If <c>preliminary</c> is returned, finalization was
            performed and the time offset is now final.</p>
          </item>
          <item><p>If <c>final</c> is returned, the time offset was
            already in the final state. This either because another
            <c>erlang:system_flag(time_offset, finalize)</c> call or
            because <seealso marker="time_correction#No_Time_Warp_Mode">no
            time warp mode</seealso> is used.</p>
          </item>
          <item><p>If <c>volatile</c> is returned, the time offset
            cannot be finalized because
            <seealso marker="time_correction#Multi_Time_Warp_Mode">multi-time
            warp mode</seealso> is used.</p>
          </item>
        </list>
      </desc>
    </func>

    <func>
      <name name="system_info" arity="1" clause_i="1"/>
      <name name="system_info" arity="1" clause_i="2"/>
      <name name="system_info" arity="1" clause_i="3"/>
      <name name="system_info" arity="1" clause_i="4"/>
      <name name="system_info" arity="1" clause_i="5"/>
      <fsummary>Information about the system allocators.</fsummary>
      <type variable="Allocator" name_i="2"/>
      <type variable="Version" name_i="2"/>
      <type variable="Features" name_i="2"/>
      <type variable="Settings" name_i="2"/>
      <type variable="Alloc" name_i="3"/>
      <desc>
        <marker id="system_info_allocator_tags"></marker>
        <p>Returns various information about the allocators of the
          current system (emulator) as specified by
          <c><anno>Item</anno></c>:</p>
        <marker id="system_info_allocated_areas"></marker>
        <taglist>
          <tag><c>allocated_areas</c></tag>
          <item>
            <p>Returns a list of tuples with information about
              miscellaneous allocated memory areas.</p>
            <p>Each tuple contains an atom describing the type of
              memory as first element and the amount of allocated
              memory in bytes as second element. When information
              about allocated and used memory is present, also a
              third element is present, containing the amount of
              used memory in bytes.</p>
            <p><c>erlang:system_info(allocated_areas)</c> is intended
              for debugging, and the content is highly
              implementation-dependent. The content of the results
              therefore changes when needed without prior notice.</p>
            <p>Notice that the sum of these values is <em>not</em>
              the total amount of memory allocated by the emulator.
              Some values are part of other values, and some memory
              areas are not part of the result. For information about
              the total amount of memory allocated by the emulator, see
              <seealso marker="#memory/0">
              <c>erlang:memory/0,1</c></seealso>.</p>
          </item>
          <tag><c>allocator</c></tag>
          <item>
            <marker id="system_info_allocator"></marker>
            <p>Returns <c>{<anno>Allocator</anno>, <anno>Version</anno>,
              <anno>Features</anno>, <anno>Settings</anno></c>, where:</p>
            <list type="bulleted">
              <item>
                <p><c><anno>Allocator</anno></c> corresponds to the
                  <c>malloc()</c> implementation used. If
                  <c><anno>Allocator</anno></c> equals
                  <c>undefined</c>, the <c>malloc()</c> implementation
                  used cannot be identified. <c>glibc</c> can be
                  identified.</p>
              </item>
              <item>
                <p><c><anno>Version</anno></c> is a list of integers
                  (but not a string) representing the version of
                  the <c>malloc()</c> implementation used.</p>
              </item>
              <item>
                <p><c><anno>Features</anno></c> is a list of atoms
                  representing the allocation features used.</p>
              </item>
              <item>
                <p><c><anno>Settings</anno></c> is a list of subsystems,
                  their configurable parameters, and used values. Settings
                  can differ between different combinations of
                  platforms, allocators, and allocation features.
                  Memory sizes are given in bytes.</p>
              </item>
            </list>
            <p>See also "System Flags Effecting erts_alloc" in
              <seealso marker="erts:erts_alloc#flags">
              <c>erts_alloc(3)</c></seealso>.</p>
          </item>
          <tag><c>alloc_util_allocators</c></tag>
          <item>
            <marker id="system_info_alloc_util_allocators"></marker>
            <p>Returns a list of the names of all allocators using
              the ERTS internal <c>alloc_util</c> framework
              as atoms. For more information, see section
              <seealso marker="erts:erts_alloc#alloc_util">The
              alloc_util framework</seealso>
              in <c>erts_alloc(3)</c>.</p>
          </item>
          <tag><c>{allocator, <anno>Alloc</anno>}</c></tag>
          <item>
            <marker id="system_info_allocator_tuple"></marker>
            <p>Returns information about the specified allocator.
              As from ERTS 5.6.1, the return value is a list
              of <c>{instance, InstanceNo, InstanceInfo}</c> tuples,
              where <c>InstanceInfo</c> contains information about
              a specific instance of the allocator.
              If <c><anno>Alloc</anno></c> is not a
              recognized allocator, <c>undefined</c> is returned.
              If <c><anno>Alloc</anno></c> is disabled,
              <c>false</c> is returned.</p>
            <p>Notice that the information returned is highly
              implementation-dependent and can be changed or removed
              at any time without prior notice. It was initially
              intended as a tool when developing new allocators, but
              as it can be of interest for others it has been
              briefly documented.</p>
            <p>The recognized allocators are listed in
              <seealso marker="erts:erts_alloc"><c>erts_alloc(3)</c></seealso>.
              Information about super carriers can be obtained from
              ERTS 8.0 with <c>{allocator, erts_mmap}</c> or from
              ERTS 5.10.4; the returned list when calling with
              <c>{allocator, mseg_alloc}</c> also includes an
              <c>{erts_mmap, _}</c> tuple as one element in the list.</p>
            <p>After reading the <c>erts_alloc(3)</c> documentation,
              the returned information
              more or less speaks for itself, but it can be worth
              explaining some things. Call counts are presented by two
              values, the first value is giga calls, and the second
              value is calls. <c>mbcs</c> and <c>sbcs</c> denote
              multi-block carriers, and single-block carriers,
              respectively. Sizes are presented in bytes. When a
              size is not presented, it is the amount of something.
              Sizes and amounts are often presented by three values:</p>
            <list type="bulleted">
              <item>The first is the current value.</item>
              <item>The second is the maximum value since the last call
                to <c>erlang:system_info({allocator, Alloc})</c>.</item>
              <item>The third is the maximum value since the emulator
                was started.</item>
            </list>
            <p>If only one value is present, it is the current value.
              <c>fix_alloc</c> memory block types are presented by two
              values. The first value is the memory pool size and
              the second value is the used memory size.</p>
          </item>
          <tag><c>{allocator_sizes, <anno>Alloc</anno>}</c></tag>
          <item>
            <marker id="system_info_allocator_sizes"></marker>
            <p>Returns various size information for the specified
              allocator. The information returned is a subset of the
              information returned by
              <seealso marker="#system_info_allocator_tuple">
              <c>erlang:system_info({allocator,
              <anno>Alloc</anno>})</c></seealso>.</p>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="system_info" arity="1" clause_i="12"
	    anchor="system_info_cpu_topology"/>
      <name name="system_info" arity="1" clause_i="13"/>
      <fsummary>Information about the CPU topology of the system.</fsummary>
      <type name="cpu_topology"/>
      <type name="level_entry"/>
      <type_desc name="cpu_topology">
        All <c><anno>LevelEntry</anno></c>s of a list
        must contain the same <c><anno>LevelTag</anno></c>, except
        on the top level where both <c>node</c> and
        <c>processor</c> <c><anno>LevelTag</anno></c>s can coexist.
      </type_desc>
      <type_desc name="level_entry">
        <c>{<anno>LevelTag</anno>,
        <anno>SubLevel</anno>} == {<anno>LevelTag</anno>, [],
        <anno>SubLevel</anno>}</c>
      </type_desc>
      <type name="level_tag"/>
      <type_desc name="level_tag">
        More <c><anno>LevelTag</anno></c>s can be introduced in a
        future release.
      </type_desc>
      <type name="sub_level"/>
      <type name="info_list"/>
      <type_desc name="info_list">
        The <c>info_list()</c> can be extended in a future release.
      </type_desc>
      <desc>
        <marker id="system_info_cpu_topology_tags"></marker>
        <p>Returns various information about the CPU topology of
          the current system (emulator) as specified by
          <c><anno>Item</anno></c>:</p>
        <taglist>
          <tag><c>cpu_topology</c></tag>
          <item>
            <p>Returns the <c><anno>CpuTopology</anno></c> currently used by
              the emulator. The CPU topology is used when binding schedulers
              to logical processors. The CPU topology used is the
              <seealso marker="erlang#system_info_cpu_topology_defined">
              user-defined CPU topology</seealso>,
              if such exists, otherwise the
              <seealso marker="erlang#system_info_cpu_topology_detected">
              automatically detected CPU topology</seealso>,
              if such exists. If no CPU topology
              exists, <c>undefined</c> is returned.</p>
            <p><c>node</c> refers to Non-Uniform Memory Access (NUMA)
              nodes. <c>thread</c> refers to hardware threads
              (for example, Intel hyper-threads).</p>
            <p>A level in term <c><anno>CpuTopology</anno></c> can be
              omitted if only one entry exists and
              <c><anno>InfoList</anno></c> is empty.</p>
            <p><c>thread</c> can only be a sublevel to <c>core</c>.
              <c>core</c> can be a sublevel to <c>processor</c>
              or <c>node</c>. <c>processor</c> can be on the
              top level or a sublevel to <c>node</c>. <c>node</c>
              can be on the top level or a sublevel to
              <c>processor</c>. That is, NUMA nodes can be processor
              internal or processor external. A CPU topology can
              consist of a mix of processor internal and external
              NUMA nodes, as long as each logical CPU belongs to
              <em>one</em> NUMA node. Cache hierarchy is not part of
              the <c><anno>CpuTopology</anno></c> type, but will be in a
              future release. Other things can also make it into the CPU
              topology in a future release. So, expect the
              <c><anno>CpuTopology</anno></c> type to change.</p>
          </item>
          <tag><c>{cpu_topology, defined}</c></tag>
          <item>
            <marker id="system_info_cpu_topology_defined"></marker>
            <p>Returns the user-defined <c><anno>CpuTopology</anno></c>.
              For more information, see command-line flag
              <seealso marker="erts:erl#+sct"><c>+sct</c></seealso> in
              <c>erl(1)</c> and argument
              <seealso marker="#system_info_cpu_topology">
              <c>cpu_topology</c></seealso>.</p>
          </item>
          <tag><c>{cpu_topology, detected}</c></tag>
          <item>
            <marker id="system_info_cpu_topology_detected"></marker>
            <p>Returns the automatically detected
              <c><anno>CpuTopology</anno>y</c>. The
              emulator detects the CPU topology on some newer
              Linux, Solaris, FreeBSD, and Windows systems.
              On Windows system with more than 32 logical processors,
              the CPU topology is not detected.</p>
            <p>For more information, see argument
              <seealso marker="#system_info_cpu_topology">
              <c>cpu_topology</c></seealso>.</p>
          </item>
          <tag><c>{cpu_topology, used}</c></tag>
          <item>
            <p>Returns <c><anno>CpuTopology</anno></c> used by the emulator.
              For more information, see argument
              <seealso marker="#system_info_cpu_topology">
              <c>cpu_topology</c></seealso>.</p>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="system_info" arity="1" clause_i="29"/>
      <name name="system_info" arity="1" clause_i="30"/>
      <name name="system_info" arity="1" clause_i="38"/>
      <name name="system_info" arity="1" clause_i="39"/>
      <name name="system_info" arity="1" clause_i="40"/>
      <name name="system_info" arity="1" clause_i="41"/>
      <fsummary>Information about the default process heap settings.</fsummary>
      <type name="message_queue_data"/>
      <type name="max_heap_size"/>
      <desc>
        <p>Returns information about the default process heap settings:</p>
        <taglist>
          <tag><c>fullsweep_after</c></tag>
          <item>
            <p>Returns <c>{fullsweep_after, integer() >= 0}</c>, which is
              the <c>fullsweep_after</c> garbage collection setting used
              by default. For more information, see
              <c>garbage_collection</c> described below.</p>
          </item>
          <tag><c>garbage_collection</c></tag>
          <item>
            <p>Returns a list describing the default garbage collection
              settings. A process spawned on the local node by a
              <c>spawn</c> or <c>spawn_link</c> uses these
              garbage collection settings. The default settings can be
              changed by using
              <seealso marker="#system_flag/2">
              <c>erlang:system_flag/2</c></seealso>.
              <seealso marker="#spawn_opt/4"><c>spawn_opt/2,3,4</c></seealso>
              can spawn a process that does not use the default
              settings.</p>
          </item>
          <tag><c>max_heap_size</c></tag>
          <item>
            <p>Returns <c>{max_heap_size, <anno>MaxHeapSize</anno>}</c>,
              where <c><anno>MaxHeapSize</anno></c> is the current
              system-wide maximum heap size settings for spawned processes.
              This setting can be set using the command-line flags
              <seealso marker="erl#+hmax"><c>+hmax</c></seealso>,
              <seealso marker="erl#+hmaxk"><c>+hmaxk</c></seealso> and
              <seealso marker="erl#+hmaxel"><c>+hmaxel</c></seealso> in
              <c>erl(1)</c>. It can also be changed at runtime using
              <seealso marker="#system_flag_max_heap_size">
              <c>erlang:system_flag(max_heap_size, MaxHeapSize)</c></seealso>.
              For more details about the <c>max_heap_size</c> process flag,
              see <seealso marker="#process_flag_max_heap_size">
              <c>process_flag(max_heap_size, MaxHeapSize)</c></seealso>.</p>
          </item>
          <tag><marker id="system_info_message_queue_data"/>
            <c>message_queue_data</c></tag>
          <item>
            <p>Returns the default value of the <c>message_queue_data</c>
              process flag, which is either <c>off_heap</c> or <c>on_heap</c>.
              This default is set by command-line argument
              <seealso marker="erl#+hmqd"><c>+hmqd</c></seealso> in
              <c>erl(1)</c>. For more information on the
              <c>message_queue_data</c> process flag, see documentation of
              <seealso marker="#process_flag_message_queue_data">
              <c>process_flag(message_queue_data, MQD)</c></seealso>.</p>
          </item>
          <tag><c>min_heap_size</c></tag>
          <item>
            <p>Returns <c>{min_heap_size, <anno>MinHeapSize</anno>}</c>,
              where <c><anno>MinHeapSize</anno></c> is the current
              system-wide minimum heap size for spawned processes.</p>
          </item>
          <tag><c>min_bin_vheap_size</c></tag>
          <item>
            <p>Returns <c>{min_bin_vheap_size,
              <anno>MinBinVHeapSize</anno>}</c>, where
              <c><anno>MinBinVHeapSize</anno></c> is the current system-wide
              minimum binary virtual heap size for spawned processes.</p>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="system_info" arity="1" clause_i="6"/>
      <name name="system_info" arity="1" clause_i="7"/>
      <name name="system_info" arity="1" clause_i="8"/>
      <name name="system_info" arity="1" clause_i="9"/>
      <name name="system_info" arity="1" clause_i="10"/>
      <name name="system_info" arity="1" clause_i="11"/>
      <name name="system_info" arity="1" clause_i="14"/>
      <name name="system_info" arity="1" clause_i="15"/>
      <name name="system_info" arity="1" clause_i="16"/>
      <name name="system_info" arity="1" clause_i="17"/>
      <name name="system_info" arity="1" clause_i="18"/>
      <name name="system_info" arity="1" clause_i="19"/>
      <name name="system_info" arity="1" clause_i="20"/>
      <name name="system_info" arity="1" clause_i="21"/>
      <name name="system_info" arity="1" clause_i="22"/>
      <name name="system_info" arity="1" clause_i="23"/>
      <name name="system_info" arity="1" clause_i="24"/>
      <name name="system_info" arity="1" clause_i="25"/>
      <name name="system_info" arity="1" clause_i="26"/>
      <name name="system_info" arity="1" clause_i="27"/>
      <name name="system_info" arity="1" clause_i="28"/>
      <name name="system_info" arity="1" clause_i="31"/>
      <name name="system_info" arity="1" clause_i="32"/>
      <name name="system_info" arity="1" clause_i="33"/>
      <name name="system_info" arity="1" clause_i="34"/>
      <name name="system_info" arity="1" clause_i="35"/>
      <name name="system_info" arity="1" clause_i="36"/>
      <name name="system_info" arity="1" clause_i="37"/>
      <name name="system_info" arity="1" clause_i="42"/>
      <name name="system_info" arity="1" clause_i="43"/>
      <name name="system_info" arity="1" clause_i="44"/>
      <name name="system_info" arity="1" clause_i="45"/>
      <name name="system_info" arity="1" clause_i="46"/>
      <name name="system_info" arity="1" clause_i="47"/>
      <name name="system_info" arity="1" clause_i="48"/>
      <name name="system_info" arity="1" clause_i="49"/>
      <name name="system_info" arity="1" clause_i="50"/>
      <name name="system_info" arity="1" clause_i="51"/>
      <name name="system_info" arity="1" clause_i="52"/>
      <name name="system_info" arity="1" clause_i="53"/>
      <name name="system_info" arity="1" clause_i="54"/>
      <name name="system_info" arity="1" clause_i="55"/>
      <name name="system_info" arity="1" clause_i="56"/>
      <name name="system_info" arity="1" clause_i="57"/>
      <name name="system_info" arity="1" clause_i="58"/>
      <name name="system_info" arity="1" clause_i="59"/>
      <name name="system_info" arity="1" clause_i="60"/>
      <name name="system_info" arity="1" clause_i="61"/>
      <name name="system_info" arity="1" clause_i="62"/>
      <name name="system_info" arity="1" clause_i="63"/>
      <name name="system_info" arity="1" clause_i="64"/>
      <name name="system_info" arity="1" clause_i="65"/>
      <name name="system_info" arity="1" clause_i="66"/>
      <name name="system_info" arity="1" clause_i="67"/>
      <name name="system_info" arity="1" clause_i="68"/>
      <name name="system_info" arity="1" clause_i="69"/>
      <name name="system_info" arity="1" clause_i="70"/>
      <name name="system_info" arity="1" clause_i="71"/>
      <fsummary>Information about the system.</fsummary>
      <desc>
        <p>Returns various information about the current system
          (emulator) as specified by <c><anno>Item</anno></c>:</p>
        <taglist>
          <tag><c>atom_count</c></tag>
          <item>
            <marker id="system_info_atom_count"></marker>
            <p>Returns the number of atoms currently existing at the
              local node. The value is given as an integer.</p>
          </item>
          <tag><c>atom_limit</c></tag>
          <item>
            <marker id="system_info_atom_limit"></marker>
            <p>Returns the maximum number of atoms allowed.
              This limit can be increased at startup by passing
              command-line flag
              <seealso marker="erts:erl#+t"><c>+t</c></seealso> to
              <c>erl(1)</c>.
            </p>
          </item>
          <tag><c>build_type</c></tag>
          <item>
            <p>Returns an atom describing the build type of the runtime
              system. This is normally the atom <c>opt</c> for optimized.
              Other possible return values are <c>debug</c>, <c>purify</c>,
              <c>quantify</c>, <c>purecov</c>, <c>gcov</c>, <c>valgrind</c>,
              <c>gprof</c>, and <c>lcnt</c>. Possible return values
              can be added or removed at any time without prior notice.</p>
          </item>
          <tag><c>c_compiler_used</c></tag>
          <item>
            <p>Returns a two-tuple describing the C compiler used when
              compiling the runtime system. The first element is an
              atom describing the name of the compiler, or <c>undefined</c>
              if unknown. The second element is a term describing the
              version of the compiler, or <c>undefined</c> if unknown.</p>
          </item>
          <tag><c>check_io</c></tag>
          <item>
            <p>Returns a list containing miscellaneous information
              about the emulators internal I/O checking. Notice that
              the content of the returned list can vary between
              platforms and over time. It is only guaranteed
              that a list is returned.</p>
          </item>
          <tag><c>compat_rel</c></tag>
          <item>
            <p>Returns the compatibility mode of the local node as
              an integer. The integer returned represents the
              Erlang/OTP release that the current emulator has been
              set to be backward compatible with. The compatibility
              mode can be configured at startup by using command-line flag
              <seealso marker="erts:erl#compat_rel"><c>+R</c></seealso> in
              <c>erl(1)</c>.</p>
          </item>
          <tag><c>cpu_topology</c></tag>
          <item>
            <p>See <seealso
              marker="#system_info_cpu_topology_tags">above</seealso>.</p>
          </item>
          <tag><c>creation</c></tag>
          <item>
            <p>Returns the creation of the local node as an integer.
              The creation is changed when a node is restarted. The
              creation of a node is stored in process identifiers, port
              identifiers, and references. This makes it (to some
              extent) possible to distinguish between identifiers from
              different incarnations of a node. The valid
              creations are integers in the range 1..3, but this will
              probably change in a future release. If the node is not
              alive, <c>0</c> is returned.</p>
          </item>
          <tag><c>debug_compiled</c></tag>
          <item>
            <p>Returns <c>true</c> if the emulator has been
              debug-compiled, otherwise <c>false</c>.</p>
          </item>
          <tag><c>delayed_node_table_gc</c></tag>
          <item>
            <marker id="system_info_delayed_node_table_gc"></marker>
            <p>Returns the amount of time in seconds garbage collection
              of an entry in a node table is delayed. This limit can be set
              on startup by passing command-line flag
              <seealso marker="erts:erl#+zdntgc"><c>+zdntgc</c></seealso>
              to <c>erl(1)</c>. For more information, see the documentation of
              the command-line flag.</p>
          </item>
          <tag><c>dirty_cpu_schedulers</c></tag>
          <item>
            <marker id="system_info_dirty_cpu_schedulers"></marker>
            <p>Returns the number of dirty CPU scheduler threads used by
              the emulator. Dirty CPU schedulers execute CPU-bound
              native functions, such as NIFs, linked-in driver code,
              and BIFs that cannot be managed cleanly by the normal
              emulator schedulers.</p>
            <p>The number of dirty CPU scheduler threads is determined
              at emulator boot time and cannot be changed after that.
              However, the number of dirty CPU scheduler threads online
              can be changed at any time. The number of dirty CPU
              schedulers can be set at startup by passing
              command-line flag
              <seealso marker="erts:erl#+SDcpu"><c>+SDcpu</c></seealso> or
              <seealso marker="erts:erl#+SDPcpu"><c>+SDPcpu</c></seealso> in
              <c>erl(1)</c>.</p>
            <p>See also
              <seealso marker="#system_flag_dirty_cpu_schedulers_online">
              <c>erlang:system_flag(dirty_cpu_schedulers_online,
              DirtyCPUSchedulersOnline)</c></seealso>,
              <seealso marker="#system_info_dirty_cpu_schedulers_online">
              <c>erlang:system_info(dirty_cpu_schedulers_online)</c></seealso>,
              <seealso marker="#system_info_dirty_io_schedulers">
              <c>erlang:system_info(dirty_io_schedulers)</c></seealso>,
              <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso>,
              <seealso marker="#system_info_schedulers_online">
              <c>erlang:system_info(schedulers_online)</c></seealso>, and
              <seealso marker="#system_flag_schedulers_online">
              <c>erlang:system_flag(schedulers_online,
              SchedulersOnline)</c></seealso>.</p>
          </item>
          <tag><c>dirty_cpu_schedulers_online</c></tag>
          <item>
            <marker id="system_info_dirty_cpu_schedulers_online"></marker>
            <p>Returns the number of dirty CPU schedulers online.
              The return value satisfies
              <c><![CDATA[1 <= DirtyCPUSchedulersOnline <= N]]></c>,
              where <c>N</c> is the smallest of the return values of
              <c>erlang:system_info(dirty_cpu_schedulers)</c> and
              <c>erlang:system_info(schedulers_online)</c>.</p>
            <p>The number of dirty CPU schedulers online can be set at
              startup by passing command-line flag
              <seealso marker="erts:erl#+SDcpu"><c>+SDcpu</c></seealso> in
              <c>erl(1)</c>.</p>
            <p>For more information, see
              <seealso marker="#system_info_dirty_cpu_schedulers">
              <c>erlang:system_info(dirty_cpu_schedulers)</c></seealso>,
              <seealso marker="#system_info_dirty_io_schedulers">
              <c>erlang:system_info(dirty_io_schedulers)</c></seealso>,
              <seealso marker="#system_info_schedulers_online">
              <c>erlang:system_info(schedulers_online)</c></seealso>, and
              <seealso marker="#system_flag_dirty_cpu_schedulers_online">
              <c>erlang:system_flag(dirty_cpu_schedulers_online,
              DirtyCPUSchedulersOnline)</c></seealso>.</p>
          </item>
          <tag><c>dirty_io_schedulers</c></tag>
          <item>
            <marker id="system_info_dirty_io_schedulers"></marker>
            <p>Returns the number of dirty I/O schedulers as an integer.
              Dirty I/O schedulers execute I/O-bound native functions,
              such as NIFs and linked-in driver code, which cannot be
              managed cleanly by the normal emulator schedulers.</p>
            <p>This value can be set at startup by passing command-line
              argument <seealso marker="erts:erl#+SDio"><c>+SDio</c></seealso>
              in <c>erl(1)</c>.</p>
            <p>For more information, see
              <seealso marker="#system_info_dirty_cpu_schedulers">
              <c>erlang:system_info(dirty_cpu_schedulers)</c></seealso>,
              <seealso marker="#system_info_dirty_cpu_schedulers_online">
              <c>erlang:system_info(dirty_cpu_schedulers_online)</c></seealso>,
              and <seealso marker="#system_flag_dirty_cpu_schedulers_online">
              <c>erlang:system_flag(dirty_cpu_schedulers_online,
              DirtyCPUSchedulersOnline)</c></seealso>.</p>
          </item>
          <tag><c>dist</c></tag>
          <item>
            <p>Returns a binary containing a string of distribution
              information formatted as in Erlang crash dumps. For more
              information, see section <seealso marker="erts:crash_dump">
              How to interpret the Erlang crash dumps</seealso>
              in the User's Guide.</p>
          </item>
          <tag><c>dist_buf_busy_limit</c></tag>
          <item>
            <marker id="system_info_dist_buf_busy_limit"></marker>
            <p>Returns the value of the distribution buffer busy limit
              in bytes. This limit can be set at startup by passing
              command-line flag
              <seealso marker="erts:erl#+zdbbl"><c>+zdbbl</c></seealso>
              to <c>erl(1)</c>.</p>
          </item>
          <tag><c>dist_ctrl</c></tag>
          <item>
            <p>Returns a list of tuples
              <c>{<anno>Node</anno>, <anno>ControllingEntity</anno>}</c>,
              one entry for each connected remote node.
              <c><anno>Node</anno></c> is the node name
              and <c><anno>ControllingEntity</anno></c> is the port or process
              identifier responsible for the communication to that node.
              More specifically, <c><anno>ControllingEntity</anno></c> for
              nodes connected through TCP/IP (the normal case) is the socket
              used in communication with the specific node.</p>
          </item>
          <tag><c>driver_version</c></tag>
          <item>
            <p>Returns a string containing the Erlang driver version
              used by the runtime system. It has the form
              <seealso marker="erts:erl_driver#version_management">
              "&lt;major ver&gt;.&lt;minor ver&gt;"</seealso>.</p>
          </item>
          <tag><c>dynamic_trace</c></tag>
          <item>
            <p>Returns an atom describing the dynamic trace framework
              compiled into the virtual machine. It can be
              <c>dtrace</c>, <c>systemtap</c>, or <c>none</c>. For a
              commercial or standard build, it is always <c>none</c>.
              The other return values indicate a custom configuration
              (for example, <c>./configure --with-dynamic-trace=dtrace</c>).
              For more information about dynamic tracing, see
              <seealso marker="runtime_tools:dyntrace">
              <c>dyntrace(3)</c></seealso> manual page and the
              <c>README.dtrace</c>/<c>README.systemtap</c> files in the
              Erlang source code top directory.</p>
          </item>
          <tag><c>dynamic_trace_probes</c></tag>
          <item>
            <p>Returns a <c>boolean()</c> indicating if dynamic trace
              probes (<c>dtrace</c> or <c>systemtap</c>) are built into
              the emulator. This can only be <c>true</c> if the virtual
              machine was built for dynamic tracing (that is,
              <c>system_info(dynamic_trace)</c> returns
              <c>dtrace</c> or <c>systemtap</c>).</p>
          </item>
          <tag><marker id="system_info_end_time"/><c>end_time</c></tag>
          <item>
            <p>The last <seealso marker="#monotonic_time/0">Erlang monotonic
              time</seealso> in <c>native</c>
              <seealso marker="#type_time_unit">time unit</seealso> that
              can be represented internally in the current Erlang runtime system
              instance. The time between the
              <seealso marker="#system_info_start_time">start time</seealso> and
              the end time is at least a quarter of a millennium.</p>
          </item>
          <tag><c>elib_malloc</c></tag>
          <item>
            <p>This option will be removed in a future release.
              The return value will always be <c>false</c>, as the
              <c>elib_malloc</c> allocator has been removed.</p>
          </item>
          <tag><c>ets_limit</c></tag>
          <item>
            <p>Returns the maximum number of ETS tables allowed. This
              limit can be increased at startup by passing
              command-line flag
              <seealso marker="erts:erl#+e"><c>+e</c></seealso> to
              <c>erl(1)</c> or by setting environment variable
              <c>ERL_MAX_ETS_TABLES</c> before starting the Erlang
              runtime system.</p>
          </item>
          <tag><c>heap_sizes</c></tag>
          <item>
            <p>Returns a list of integers representing valid heap sizes 
              in words. All Erlang heaps are sized from sizes in this
              list.</p>
          </item>
          <tag><c>heap_type</c></tag>
          <item>
            <p>Returns the heap type used by the current emulator. One
              heap type exists:</p>
            <taglist>
              <tag><c>private</c></tag>
              <item>
                Each process has a heap reserved for its use and no
                references between heaps of different processes are
                allowed. Messages passed between processes are copied
                between heaps.
              </item>
            </taglist>
          </item>
          <tag><c>info</c></tag>
          <item>
            <p>Returns a binary containing a string of miscellaneous
              system information formatted as in Erlang crash dumps.
              For more information, see section
              <seealso marker="erts:crash_dump">
              How to interpret the Erlang crash dumps</seealso>
              in the User's Guide.</p>
          </item>
          <tag><c>kernel_poll</c></tag>
          <item>
            <p>Returns <c>true</c> if the emulator uses some kind of
              kernel-poll implementation, otherwise <c>false</c>.</p>
          </item>
          <tag><c>loaded</c></tag>
          <item>
            <p>Returns a binary containing a string of loaded module
              information formatted as in Erlang crash dumps. For more
              information, see section
              <seealso marker="erts:crash_dump">How to interpret the Erlang
              crash dumps</seealso> in the User's Guide.</p>
          </item>
          <tag><c>logical_processors</c></tag>
          <item>
            <marker id="logical_processors"></marker>
            <p>Returns the detected number of logical processors configured
              in the system. The return value is either an integer, or
              the atom <c>unknown</c> if the emulator cannot
              detect the configured logical processors.</p>
          </item>
          <tag><c>logical_processors_available</c></tag>
          <item>
            <marker id="logical_processors_available"></marker>
            <p>Returns the detected number of logical processors available
              to the Erlang runtime system. The return value is either an
              integer, or the atom <c>unknown</c> if the emulator
              cannot detect the available logical processors. The number
              of available logical processors is less than or equal to
              the number of <seealso marker="#logical_processors_online">
              logical processors online</seealso>.</p>
          </item>
          <tag><c>logical_processors_online</c></tag>
          <item>
            <marker id="logical_processors_online"></marker>
            <p>Returns the detected number of logical processors online on
              the system. The return value is either an integer,
              or the atom <c>unknown</c> if the emulator cannot
              detect logical processors online. The number of logical
              processors online is less than or equal to the number of
              <seealso marker="#logical_processors">logical processors
              configured</seealso>.</p>
          </item>
          <tag><c>machine</c></tag>
          <item>
            <p>Returns a string containing the Erlang machine name.</p>
          </item>
          <tag><c>modified_timing_level</c></tag>
          <item>
            <p>Returns the modified timing-level (an integer) if
              modified timing is enabled, otherwise <c>undefined</c>.
              For more information about modified timing, see
              command-line flag
              <seealso marker="erts:erl#+T"><c>+T</c></seealso>
              in <c>erl(1)</c></p>
          </item>
          <tag><c>multi_scheduling</c></tag>
          <item>
            <marker id="system_info_multi_scheduling"></marker>
            <p>Returns one of the following:</p>
            <taglist>
              <tag><c>disabled</c></tag>
              <item>
                <p>The emulator has been started with only one scheduler thread.</p>
              </item>
              <tag><c>blocked</c></tag>
              <item>
                <p>The emulator has more than one scheduler thread,
                  but all scheduler threads except one are blocked.
                  That is, only one scheduler thread schedules
                  Erlang processes and executes Erlang code.</p>
              </item>
              <tag><c>blocked_normal</c></tag>
              <item>
                <p>The emulator has more than one scheduler thread,
                  but all normal scheduler threads except one are
                  blocked. Notice that dirty schedulers are not
                  blocked, and can schedule Erlang processes and
                  execute native code.</p>
              </item>
              <tag><c>enabled</c></tag>
              <item>
                <p>The emulator has more than one scheduler thread,
                  and no scheduler threads are blocked. That is,
                  all available scheduler threads schedule
                  Erlang processes and execute Erlang code.</p>
              </item>
            </taglist>
            <p>See also
              <seealso marker="#system_flag_multi_scheduling">
              <c>erlang:system_flag(multi_scheduling, BlockState)</c></seealso>,
              <seealso marker="#system_info_multi_scheduling_blockers">
              <c>erlang:system_info(multi_scheduling_blockers)</c></seealso>,
              <seealso marker="#system_info_normal_multi_scheduling_blockers">
              <c>erlang:system_info(normal_multi_scheduling_blockers)</c></seealso>,
              and <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso>.</p>
          </item>
          <tag><c>multi_scheduling_blockers</c></tag>
          <item>
            <marker id="system_info_multi_scheduling_blockers"></marker>
            <p>Returns a list of <c><anno>Pid</anno></c>s when
              multi-scheduling is blocked, otherwise the empty list is
              returned. The <c><anno>Pid</anno></c>s in the list
              represent all the processes currently
              blocking multi-scheduling. A <c><anno>Pid</anno></c> occurs
              only once in the list, even if the corresponding
              process has blocked multiple times.</p>
            <p>See also
              <seealso marker="#system_flag_multi_scheduling">
              <c>erlang:system_flag(multi_scheduling, BlockState)</c></seealso>,
              <seealso marker="#system_info_multi_scheduling">
              <c>erlang:system_info(multi_scheduling)</c></seealso>,
              <seealso marker="#system_info_normal_multi_scheduling_blockers">
              <c>erlang:system_info(normal_multi_scheduling_blockers)</c></seealso>,
              and <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso>.</p>
          </item>
          <tag><c>nif_version</c></tag>
          <item>
            <p>Returns a string containing the version of the Erlang NIF
              interface used by the runtime system. It is on the form
              "&lt;major ver&gt;.&lt;minor ver&gt;".</p>
          </item>
          <tag><c>normal_multi_scheduling_blockers</c></tag>
          <item>
            <marker id="system_info_normal_multi_scheduling_blockers"></marker>
            <p>Returns a list of <c><anno>Pid</anno></c>s when
              normal multi-scheduling is blocked (that is, all normal schedulers
              but one is blocked), otherwise the empty list is returned.
              The <c><anno>Pid</anno></c>s in the list represent all the
              processes currently blocking normal multi-scheduling.
              A <c><anno>Pid</anno></c> occurs only once in the list, even if
              the corresponding process has blocked multiple times.</p>
            <p>See also
              <seealso marker="#system_flag_multi_scheduling">
              <c>erlang:system_flag(multi_scheduling, BlockState)</c></seealso>,
              <seealso marker="#system_info_multi_scheduling">
              <c>erlang:system_info(multi_scheduling)</c></seealso>,
              <seealso marker="#system_info_multi_scheduling_blockers">
              <c>erlang:system_info(multi_scheduling_blockers)</c></seealso>,
              and <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso>.</p>
          </item>
          <tag><marker id="system_info_otp_release"/>
            <c>otp_release</c></tag>
          <item>
            <marker id="system_info_otp_release"></marker>
            <p>Returns a string containing the OTP release number of the
              OTP release that the currently executing ERTS application
              is part of.</p>
            <p>As from Erlang/OTP 17, the OTP release number corresponds to
              the major OTP version number. No
              <c>erlang:system_info()</c> argument gives the exact OTP
              version. This is because the exact OTP version in the general case
              is difficult to determine. For more information, see the
              description of versions in
              <seealso marker="doc/system_principles:versions">
              System principles</seealso> in System Documentation.</p>
          </item>
          <tag><marker id="system_info_os_monotonic_time_source"/>
            <c>os_monotonic_time_source</c></tag>
          <item>
            <p>Returns a list containing information about the source of
              <seealso marker="erts:time_correction#OS_Monotonic_Time">OS
              monotonic time</seealso> that is used by the runtime system.</p>
            <p>If <c>[]</c> is returned, no OS monotonic time is
              available. The list contains two-tuples with <c>Key</c>s
              as first element, and <c>Value</c>s as second element. The
              order of these tuples is undefined. The following
              tuples can be part of the list, but more tuples can be
              introduced in the future:</p>
            <taglist>
              <tag><c>{function, Function}</c></tag>
              <item><p><c>Function</c> is the name of the function
                used. This tuple always exists if OS monotonic time is
                available to the runtime system.</p>
              </item>
              <tag><c>{clock_id, ClockId}</c></tag>
              <item><p>This tuple only exists if <c>Function</c>
                can be used with different clocks. <c>ClockId</c>
                corresponds to the clock identifier used when calling
                <c>Function</c>.</p>
              </item>
              <tag><c>{resolution, OsMonotonicTimeResolution}</c></tag>
              <item><p>Highest possible
                <seealso marker="time_correction#Time_Resolution">
                resolution</seealso>
                of current OS monotonic time source as parts per
                second. If no resolution information can be retrieved
                from the OS, <c>OsMonotonicTimeResolution</c> is
                set to the resolution of the time unit of
                <c>Function</c>s return value. That is, the actual
                resolution can be lower than
                <c>OsMonotonicTimeResolution</c>. Notice that
                the resolution does not say anything about the
                <seealso marker="time_correction#Time_Accuracy">
                accuracy</seealso> or whether the
                <seealso marker="time_correction#Time_Precision">
                precision</seealso> aligns with the resolution. You do,
                however, know that the precision is not better than
                <c>OsMonotonicTimeResolution</c>.</p>
              </item>
              <tag><c>{extended, Extended}</c></tag>
              <item><p><c>Extended</c> equals <c>yes</c> if
                the range of time values has been extended;
                otherwise <c>Extended</c> equals <c>no</c>. The
                range must be extended if <c>Function</c>
                returns values that wrap fast. This typically
                is the case when the return value is a 32-bit value.</p>
              </item>
              <tag><c>{parallel, Parallel}</c></tag>
              <item><p><c>Parallel</c> equals <c>yes</c> if
                <c>Function</c> is called in parallel from multiple
                threads. If it is not called in parallel, because
                calls must be serialized, <c>Parallel</c> equals
                <c>no</c>.</p>
              </item>
              <tag><c>{time, OsMonotonicTime}</c></tag>
              <item><p><c>OsMonotonicTime</c> equals current OS
                monotonic time in <c>native</c>
                <seealso marker="#type_time_unit">time unit</seealso>.</p>
              </item>
            </taglist>
          </item>
          <tag><marker id="system_info_os_system_time_source"/>
          <c>os_system_time_source</c></tag>
          <item>
            <p>Returns a list containing information about the source of
              <seealso marker="erts:time_correction#OS_System_Time">OS
              system time</seealso> that is used by the runtime system.</p>
            <p>The list contains two-tuples with <c>Key</c>s
              as first element, and <c>Value</c>s as second element. The
              order if these tuples is undefined. The following
              tuples can be part of the list, but more tuples can be
              introduced in the future:</p>
            <taglist>
              <tag><c>{function, Function}</c></tag>
              <item><p><c>Function</c> is the name of the funcion used.</p>
              </item>
              <tag><c>{clock_id, ClockId}</c></tag>
              <item><p>Exists only if <c>Function</c>
                can be used with different clocks. <c>ClockId</c>
                corresponds to the clock identifier used when calling
                <c>Function</c>.</p>
              </item>
              <tag><c>{resolution, OsSystemTimeResolution}</c></tag>
              <item><p>Highest possible
                <seealso marker="time_correction#Time_Resolution">
                resolution</seealso>
                of current OS system time source as parts per
                second. If no resolution information can be retrieved
                from the OS, <c>OsSystemTimeResolution</c> is
                set to the resolution of the time unit of
                <c>Function</c>s return value. That is, the actual
                resolution can be lower than
                <c>OsSystemTimeResolution</c>. Notice that
                the resolution does not say anything about the
                <seealso marker="time_correction#Time_Accuracy">
                accuracy</seealso> or whether the
                <seealso marker="time_correction#Time_Precision">
                precision</seealso> do align with the resolution. You do,
                however, know that the precision is not better than
                <c>OsSystemTimeResolution</c>.</p>
              </item>
              <tag><c>{parallel, Parallel}</c></tag>
              <item><p><c>Parallel</c> equals <c>yes</c> if
                <c>Function</c> is called in parallel from multiple
                threads. If it is not called in parallel, because
                calls needs to be serialized, <c>Parallel</c> equals
                <c>no</c>.</p>
              </item>
              <tag><c>{time, OsSystemTime}</c></tag>
              <item><p><c>OsSystemTime</c> equals current OS
                system time in <c>native</c>
                <seealso marker="#type_time_unit">time unit</seealso>.</p>
              </item>
            </taglist>
          </item>
          <tag><c>port_parallelism</c></tag>
          <item>
            <marker id="system_info_port_parallelism"></marker>
            <p>Returns the default port parallelism scheduling hint used.
              For more information, see command-line argument
              <seealso marker="erl#+spp"><c>+spp</c></seealso>
              in <c>erl(1)</c>.</p>
          </item>
          <tag><marker id="system_info_port_count"/><c>port_count</c></tag>
          <item>
            <p>Returns the number of ports currently existing at the
              local node. The value is given as an integer. This is
              the same value as returned by
              <c>length(erlang:ports())</c>, but more efficient.</p>
          </item>
          <tag><c>port_limit</c></tag>
          <item>
          <marker id="system_info_port_limit"></marker>
            <p>Returns the maximum number of simultaneously existing
              ports at the local node as an integer. This limit can be
              configured at startup by using command-line flag
              <seealso marker="erl#+Q"><c>+Q</c></seealso> in <c>erl(1)</c>.</p>
          </item>
          <tag><marker id="system_info_process_count"/>
            <c>process_count</c></tag>
          <item>
            <p>Returns the number of processes currently existing at the
              local node. The value is given as an integer. This is
              the same value as returned by
              <c>length(processes())</c>, but more efficient.</p>
          </item>
          <tag><c>process_limit</c></tag>
          <item>
            <marker id="system_info_process_limit"></marker>
            <p>Returns the maximum number of simultaneously existing
              processes at the local node. The value is given as an
              integer. This limit can be configured at startup by using
              command-line flag <seealso marker="erl#+P"><c>+P</c></seealso>
              in <c>erl(1)</c>.</p>
          </item>
          <tag><c>procs</c></tag>
          <item>
            <p>Returns a binary containing a string of process and port
              information formatted as in Erlang crash dumps. For more
              information, see section <seealso marker="erts:crash_dump">
              How to interpret the Erlang crash dumps</seealso>
              in the User's Guide.</p>
          </item>
          <tag><c>scheduler_bind_type</c></tag>
          <item>
            <marker id="system_info_scheduler_bind_type"></marker>
            <p>Returns information about how the user has requested
              schedulers to be bound or not bound.</p>
            <p>Notice that although a user has requested
              schedulers to be bound, they can silently have failed
              to bind. To inspect the scheduler bindings, call
              <seealso marker="#system_info_scheduler_bindings">
              <c>erlang:system_info(scheduler_bindings)</c></seealso>.</p>
            <p>For more information, see command-line argument
              <seealso marker="erts:erl#+sbt"><c>+sbt</c></seealso>
              in <c>erl(1)</c> and
              <seealso marker="#system_info_scheduler_bindings">
              <c>erlang:system_info(scheduler_bindings)</c></seealso>.</p>
          </item>
          <tag><c>scheduler_bindings</c></tag>
          <item>
            <marker id="system_info_scheduler_bindings"></marker>
            <p>Returns information about the currently used scheduler
              bindings.</p>
            <p>A tuple of a size equal to
              <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso>
              is returned. The tuple elements are integers
              or the atom <c>unbound</c>. Logical processor identifiers
              are represented as integers. The <c>N</c>th
              element of the tuple equals the current binding for
              the scheduler with the scheduler identifier equal to
              <c>N</c>. For example, if the schedulers are bound,
              <c>element(erlang:system_info(scheduler_id),
              erlang:system_info(scheduler_bindings))</c> returns
              the identifier of the logical processor that the calling
              process is executing on.</p>
            <p>Notice that only schedulers online can be bound to logical
              processors.</p>
            <p>For more information, see command-line argument
              <seealso marker="erts:erl#+sbt"><c>+sbt</c></seealso>
              in <c>erl(1)</c> and
              <seealso marker="#system_info_schedulers_online">
              <c>erlang:system_info(schedulers_online)</c></seealso>.</p>
          </item>
          <tag><c>scheduler_id</c></tag>
          <item>
            <marker id="system_info_scheduler_id"></marker>
            <p>Returns the scheduler ID (<c>SchedulerId</c>) of the
              scheduler thread that the calling process is executing
              on. <c><anno>SchedulerId</anno></c> is a positive integer,
              where <c><![CDATA[1 <= SchedulerId <=
              erlang:system_info(schedulers)]]></c>.</p>
            <p>See also
              <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso>.</p>
          </item>
          <tag><c>schedulers</c></tag>
          <item>
            <marker id="system_info_schedulers"></marker>
            <p>Returns the number of scheduler threads used by
              the emulator. Scheduler threads online schedules Erlang
              processes and Erlang ports, and execute Erlang code
              and Erlang linked-in driver code.</p>
            <p>The number of scheduler threads is determined at
              emulator boot time and cannot be changed later.
              However, the number of schedulers online can
              be changed at any time.</p>
            <p>See also
              <seealso marker="#system_flag_schedulers_online">
              <c>erlang:system_flag(schedulers_online,
              SchedulersOnline)</c></seealso>,
              <seealso marker="#system_info_schedulers_online">
              <c>erlang:system_info(schedulers_online)</c></seealso>,
              <seealso marker="#system_info_scheduler_id">
              <c>erlang:system_info(scheduler_id)</c></seealso>,
              <seealso marker="#system_flag_multi_scheduling">
              <c>erlang:system_flag(multi_scheduling, BlockState)</c></seealso>,
              <seealso marker="#system_info_multi_scheduling">
              <c>erlang:system_info(multi_scheduling)</c></seealso>,
              <seealso marker="#system_info_normal_multi_scheduling_blockers">
              <c>erlang:system_info(normal_multi_scheduling_blockers)</c></seealso>
              and <seealso marker="#system_info_multi_scheduling_blockers">
              <c>erlang:system_info(multi_scheduling_blockers)</c></seealso>.
            </p>
          </item>
          <tag><c>schedulers_online</c></tag>
          <item>
            <marker id="system_info_schedulers_online"></marker>
            <p>Returns the number of schedulers online. The scheduler
              identifiers of schedulers online satisfy the relationship
              <c><![CDATA[1 <= SchedulerId <=
              erlang:system_info(schedulers_online)]]></c>.</p>
            <p>For more information, see
              <seealso marker="#system_info_schedulers">
              <c>erlang:system_info(schedulers)</c></seealso> and
              <seealso marker="#system_flag_schedulers_online">
              <c>erlang:system_flag(schedulers_online,
              SchedulersOnline)</c></seealso>.</p>
          </item>
          <tag><c>smp_support</c></tag>
          <item>
            <p>Returns <c>true</c>.</p>
          </item>
          <tag><marker id="system_info_start_time"/><c>start_time</c></tag>
          <item>
            <p>The <seealso marker="#monotonic_time/0">Erlang monotonic
              time</seealso> in <c>native</c>
              <seealso marker="#type_time_unit">time unit</seealso> at the
              time when current Erlang runtime system instance started.</p>
            <p>See also <seealso marker="#system_info_end_time">
              <c>erlang:system_info(end_time)</c></seealso>.</p>
          </item>
          <tag><c>system_version</c></tag>
          <item>
            <p>Returns a string containing version number and
              some important properties, such as the number of schedulers.</p>
          </item>
          <tag><c>system_architecture</c></tag>
          <item>
            <p>Returns a string containing the processor and OS
              architecture the emulator is built for.</p>
          </item>
          <tag><c>threads</c></tag>
          <item>
            <p>Returns <c>true</c>.</p>
          </item>
          <tag><c>thread_pool_size</c></tag>
          <item>
            <marker id="system_info_thread_pool_size"></marker>
            <p>Returns the number of async threads in the async thread
              pool used for asynchronous driver calls
              (<seealso marker="erts:erl_driver#driver_async">
              <c>erl_driver:driver_async()</c></seealso>).
              The value is given as an integer.</p>
          </item>
          <tag><c>time_correction</c></tag>
          <item>
            <marker id="system_info_time_correction"></marker>
            <p>Returns a boolean value indicating whether
              <seealso marker="time_correction#Time_Correction">
              time correction</seealso> is enabled or not.</p>
          </item>
          <tag><c>time_offset</c></tag>
          <item>
            <marker id="system_info_time_offset"></marker>
            <p>Returns the state of the time offset:</p>
            <taglist>
              <tag><c>preliminary</c></tag>
              <item>
                <p>The time offset is preliminary, and will be changed
                  and finalized later. The preliminary time offset
                  is used during the preliminary phase of the
                  <seealso marker="time_correction#Single_Time_Warp_Mode">
                  single time warp mode</seealso>.</p>
              </item>
              <tag><c>final</c></tag>
              <item>
                <p>The time offset is final. This either because
                  <seealso marker="time_correction#No_Time_Warp_Mode">
                  no time warp mode</seealso> is used, or because the time
                  offset have been finalized when
                  <seealso marker="time_correction#Single_Time_Warp_Mode">
                  single time warp mode</seealso> is used.</p>
              </item>
              <tag><c>volatile</c></tag>
              <item>
                <p>The time offset is volatile. That is, it can
                  change at any time. This is because
                  <seealso marker="time_correction#Multi_Time_Warp_Mode">
                  multi-time warp mode</seealso> is used.</p>
              </item>
            </taglist>
          </item>
          <tag><marker id="system_info_time_warp_mode"/>
            <c>time_warp_mode</c></tag>
          <item>
            <p>Returns a value identifying the
              <seealso marker="time_correction#Time_Warp_Modes">
              time warp mode</seealso> that is used:</p>
            <taglist>
              <tag><c>no_time_warp</c></tag>
              <item>The <seealso marker="time_correction#No_Time_Warp_Mode">
                no time warp mode</seealso> is used.
              </item>
              <tag><c>single_time_warp</c></tag>
              <item>The <seealso marker="time_correction#Single_Time_Warp_Mode">
                single time warp mode</seealso> is used.
              </item>
              <tag><c>multi_time_warp</c></tag>
              <item>The <seealso marker="time_correction#Multi_Time_Warp_Mode">
                multi-time warp mode</seealso> is used.
              </item>
            </taglist>
          </item>
          <tag><c>tolerant_timeofday</c></tag>
          <item>
            <marker id="system_info_tolerant_timeofday"></marker>
            <p>Returns whether a pre ERTS 7.0 backwards compatible
              compensation for sudden changes of system time is <c>enabled</c>
              or <c>disabled</c>. Such compensation is <c>enabled</c> when the
              <seealso marker="#system_info_time_offset">time offset</seealso>
              is <c>final</c>, and
              <seealso marker="#system_info_time_correction">
              time correction</seealso> is enabled.</p>
          </item>
          <tag><c>trace_control_word</c></tag>
          <item>
            <p>Returns the value of the node trace control word. For
              more information, see function <c>get_tcw</c> in section
              <seealso marker="erts:match_spec#get_tcw">
              Match Specifications in Erlang</seealso> in the User's Guide.</p>
          </item>
          <tag><c>update_cpu_info</c></tag>
          <item>
            <marker id="update_cpu_info"></marker>
            <p>The runtime system rereads the CPU information available
              and updates its internally stored information about the
              <seealso marker="#system_info_cpu_topology_detected">detected
              CPU topology</seealso> and the number of logical processors
              <seealso marker="#logical_processors">configured</seealso>,
              <seealso marker="#logical_processors_online">online</seealso>,
              and <seealso marker="#logical_processors_available">
              available</seealso>.</p>
            <p>If the CPU information has changed since the last time
              it was read, the atom <c>changed</c> is returned, otherwise
              the atom <c>unchanged</c>. If the CPU information has changed,
              you probably want to
              <seealso marker="#system_flag_schedulers_online">adjust the
              number of schedulers online</seealso>. You typically want
              to have as many schedulers online as
              <seealso marker="#logical_processors_available">logical
              processors available</seealso>.</p>
          </item>
          <tag><c>version</c></tag>
          <item>
            <marker id="system_info_version"></marker>
            <p>Returns a string containing the version number of the
              emulator.</p>
          </item>
          <tag><c>wordsize</c></tag>
          <item>
            <p>Same as <c>{wordsize, internal}</c>.</p>
          </item>
          <tag><c>{wordsize, internal}</c></tag>
          <item>
            <p>Returns the size of Erlang term words in bytes as an
              integer, that is, 4 is returned on a 32-bit architecture,
              and 8 is returned on a pure 64-bit architecture. On a
              halfword 64-bit emulator, 4 is returned, as the Erlang
              terms are stored using a virtual word size of half the
              system word size.</p>
          </item>
          <tag><c>{wordsize, external}</c></tag>
          <item>
            <p>Returns the true word size of the emulator, that is,
              the size of a pointer. The value is given in bytes
              as an integer. On a pure 32-bit architecture, 4 is
              returned. On both a half word and on a pure
              64-bit architecture, 8 is returned.</p>
          </item>
        </taglist>
        <note>
          <p>Argument <c>scheduler</c> has changed name to
            <c>scheduler_id</c> to avoid mix up with argument
            <c>schedulers</c>. Argument <c>scheduler</c> was
            introduced in ERTS 5.5 and renamed in
            ERTS 5.5.1.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="system_monitor" arity="0"/>
      <fsummary>Current system performance monitoring settings.</fsummary>
      <type name="system_monitor_option"/>
      <desc>
        <p>Returns the current system monitoring settings set by
          <seealso marker="#system_monitor/2">
          <c>erlang:system_monitor/2</c></seealso>
          as <c>{<anno>MonitorPid</anno>, <anno>Options</anno>}</c>,
          or <c>undefined</c> if no settings exist. The order of the
          options can be different from the one that was set.</p>
      </desc>
    </func>

    <func>
      <name name="system_monitor" arity="1"/>
      <fsummary>Set or clear system performance monitoring options.</fsummary>
      <type name="system_monitor_option"/>
      <desc>
        <p>When called with argument <c>undefined</c>, all
          system performance monitoring settings are cleared.</p>
        <p>Calling the function with <c>{<anno>MonitorPid</anno>,
          <anno>Options</anno>}</c> as argument is the same as calling
          <seealso marker="#system_monitor/2">
          <c>erlang:system_monitor(<anno>MonitorPid</anno>,
          <anno>Options</anno>)</c></seealso>.</p>
        <p>Returns the previous system monitor settings just like
          <seealso marker="#system_monitor/0">
          <c>erlang:system_monitor/0</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_monitor" arity="2"/>
      <fsummary>Set system performance monitoring options.</fsummary>
      <type name="system_monitor_option"/>
      <desc>
        <p>Sets the system performance monitoring options.
          <c><anno>MonitorPid</anno></c> is a local process identifier (pid)
          receiving system monitor messages. The
          second argument is a list of monitoring options:</p>
        <taglist>
          <tag><c>{long_gc, Time}</c></tag>
          <item>
            <p>If a garbage collection in the system takes at least
              <c>Time</c> wall clock milliseconds, a message
              <c>{monitor, GcPid, long_gc, Info}</c> is sent to
              <c><anno>MonitorPid</anno></c>. <c>GcPid</c> is the pid that
              was garbage collected. <c>Info</c> is a list of two-element
              tuples describing the result of the garbage collection.</p>
            <p>One of the tuples is <c>{timeout, GcTime}</c>, where
              <c>GcTime</c> is the time for the garbage
              collection in milliseconds. The other tuples are
              tagged with <c>heap_size</c>, <c>heap_block_size</c>,
              <c>stack_size</c>, <c>mbuf_size</c>, <c>old_heap_size</c>,
              and <c>old_heap_block_size</c>. These tuples are
              explained in the description of trace message
              <seealso marker="#gc_minor_start"><c>gc_minor_start</c></seealso>
              (see <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>).
              New tuples can be added, and the order of the tuples in
              the <c>Info</c> list can be changed at any time without
              prior notice.</p>
          </item>
          <tag><c>{long_schedule, Time}</c></tag>
          <item>
            <p>If a process or port in the system runs uninterrupted
              for at least <c>Time</c> wall clock milliseconds, a
              message <c>{monitor, PidOrPort, long_schedule, Info}</c>
              is sent to <c>MonitorPid</c>. <c>PidOrPort</c> is the
              process or port that was running. <c>Info</c> is a
              list of two-element tuples describing the event.</p>
            <p>If a <c>pid()</c>, the tuples <c>{timeout, Millis}</c>,
              <c>{in, Location}</c>, and <c>{out, Location}</c> are
              present, where <c>Location</c> is either an MFA
              (<c>{Module, Function, Arity}</c>) describing the
              function where the process was scheduled in/out, or the
              atom <c>undefined</c>.</p>
            <p>If a <c>port()</c>, the
              tuples <c>{timeout, Millis}</c> and <c>{port_op,Op}</c>
              are present. <c>Op</c> is one of <c>proc_sig</c>,
              <c>timeout</c>, <c>input</c>, <c>output</c>,
              <c>event</c>, or <c>dist_cmd</c>, depending on which
              driver callback was executing.</p>
            <p><c>proc_sig</c> is an
              internal operation and is never to appear, while the
              others represent the corresponding driver callbacks
              <c>timeout</c>, <c>ready_input</c>, <c>ready_output</c>,
              <c>event</c>, and <c>outputv</c> (when the port
              is used by distribution). Value <c>Millis</c> in
              tuple <c>timeout</c> informs about the
              uninterrupted execution time of the process or port, which
              always is equal to or higher than the <c>Time</c> value
              supplied when starting the trace. New tuples can be
              added to the <c>Info</c> list in a future release. The
              order of the tuples in the list can be changed at any
              time without prior notice.</p>
            <p>This can be used to detect problems with NIFs or
              drivers that take too long to execute. 1 ms is
              considered a good maximum time for a driver callback
              or a NIF. However, a time-sharing system is usually to
              consider everything &lt; 100 ms as "possible" and
              fairly "normal". However, longer schedule times can
              indicate swapping or a misbehaving NIF/driver.
              Misbehaving NIFs and drivers can cause bad resource
              utilization and bad overall system performance.</p>
          </item>
          <tag><c>{large_heap, Size}</c></tag>
          <item>
            <p>If a garbage collection in the system results in
              the allocated size of a heap being at least <c>Size</c>
              words, a message <c>{monitor, GcPid, large_heap, Info}</c>
              is sent to <c><anno>MonitorPid</anno></c>.
              <c>GcPid</c> and <c>Info</c>
              are the same as for <c>long_gc</c> earlier, except that
              the tuple tagged with <c>timeout</c> is not present.</p>
            <p>The monitor message is sent if the sum of the sizes of
              all memory blocks allocated for all heap generations after
              a garbage collection is equal to or higher than <c>Size</c>.</p>
            <p>When a process is killed by
              <seealso marker="#process_flag_max_heap_size">
              <c>max_heap_size</c></seealso>, it is killed before the
              garbage collection is complete and thus no large heap message
              is sent.</p>
          </item>
          <tag><c>busy_port</c></tag>
          <item>
            <p>If a process in the system gets suspended because it
              sends to a busy port, a message
              <c>{monitor, SusPid, busy_port, Port}</c> is sent to
              <c><anno>MonitorPid</anno></c>. <c>SusPid</c> is the pid
              that got suspended when sending to <c>Port</c>.</p>
          </item>
          <tag><c>busy_dist_port</c></tag>
          <item>
            <p>If a process in the system gets suspended because it
              sends to a process on a remote node whose inter-node
              communication was handled by a busy port, a message
              <c>{monitor, SusPid, busy_dist_port, Port}</c> is sent to
              <c><anno>MonitorPid</anno></c>. <c>SusPid</c> is the pid
              that got suspended when sending through the inter-node
              communication port <c>Port</c>.</p>
          </item>
        </taglist>
        <p>Returns the previous system monitor settings just like
          <seealso marker="#system_monitor/0">
          <c>erlang:system_monitor/0</c></seealso>.</p>
        <note>
          <p>If a monitoring process gets so large that it itself
            starts to cause system monitor messages when garbage
            collecting, the messages enlarge the process
            message queue and probably make the problem worse.</p>
          <p>Keep the monitoring process neat and do not set the system
            monitor limits too tight.</p>
        </note>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>MonitorPid</anno></c> does not exist.</item>
          <tag><c>badarg</c></tag>
          <item>If <c><anno>MonitorPid</anno></c> is not a local process.</item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="system_profile" arity="0"/>
      <fsummary>Current system profiling settings.</fsummary>
      <type name="system_profile_option"/>
      <desc>
        <p>Returns the current system profiling settings set by
          <seealso marker="#system_profile/2">
          <c>erlang:system_profile/2</c></seealso>
          as <c>{<anno>ProfilerPid</anno>, <anno>Options</anno>}</c>,
          or <c>undefined</c> if there
          are no settings. The order of the options can be different
          from the one that was set.</p>
      </desc>
    </func>

    <func>
      <name name="system_profile" arity="2"/>
      <fsummary>Current system profiling settings.</fsummary>
      <type name="system_profile_option"/>
      <desc>
        <p>Sets system profiler options. <c><anno>ProfilerPid</anno></c>
          is a local process identifier (pid) or port receiving profiling
          messages. The receiver is excluded from all profiling.
          The second argument is a list of profiling options:</p>
        <taglist>
          <tag><c>exclusive</c></tag>
          <item>
            <p>If a synchronous call to a port from a process is done, the
              calling process is considered not runnable during the call
              runtime to the port. The calling process is notified as
              <c>inactive</c>, and later <c>active</c> when the port
              callback returns.</p>
          </item>
          <tag><c>monotonic_timestamp</c></tag>
          <item>
            <p>Time stamps in profile messages use
              <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
              monotonic time</seealso>. The time stamp (Ts) has the same
              format and value as produced by
              <c>erlang:monotonic_time(nanosecond)</c>.</p>
          </item>
          <tag><c>runnable_procs</c></tag>
          <item>
            <p>If a process is put into or removed from the run queue, a
              message, <c>{profile, Pid, State, Mfa, Ts}</c>, is sent to
              <c><anno>ProfilerPid</anno></c>. Running processes that
              are reinserted into the run queue after having been
              pre-empted do not trigger this message.</p>
          </item>
          <tag><c>runnable_ports</c></tag>
          <item>
            <p>If a port is put into or removed from the run queue, a 
              message, <c>{profile, Port, State, 0, Ts}</c>, is sent to
              <c><anno>ProfilerPid</anno></c>.</p>
          </item>
          <tag><c>scheduler</c></tag>
          <item>
            <p>If a scheduler is put to sleep or awoken, a message,
              <c>{profile, scheduler, Id, State, NoScheds, Ts}</c>, is
              sent to <c><anno>ProfilerPid</anno></c>.</p>
          </item>
          <tag><c>strict_monotonic_timestamp</c></tag>
          <item>
            <p>Time stamps in profile messages consist of
              <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
              monotonic time</seealso> and a monotonically increasing
              integer. The time stamp (Ts) has the same format and value
              as produced by <c>{erlang:monotonic_time(nanosecond),
              erlang:unique_integer([monotonic])}</c>.</p>
          </item>
          <tag><c>timestamp</c></tag>
          <item>
            <p>Time stamps in profile messages include a
              time stamp (Ts) that has the same form as returned by
              <c>erlang:now()</c>. This is also the default if no
              time stamp flag is specified. If <c>cpu_timestamp</c> has
              been enabled through
              <seealso marker="erlang:trace/3"><c>erlang:trace/3</c></seealso>,
              this also effects the time stamp produced in profiling messages
              when flag <c>timestamp</c> is enabled.</p>
          </item>
        </taglist>
        <note>
          <p><c>erlang:system_profile</c> behavior can change
            in a future release.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="system_time" arity="0"/>
      <fsummary>Current Erlang system time.</fsummary>
      <desc>
        <p>Returns current
          <seealso marker="time_correction#Erlang_System_Time">
          Erlang system time</seealso> in <c>native</c>
          <seealso marker="#type_time_unit">time unit</seealso>.</p>
        <p>Calling <c>erlang:system_time()</c> is equivalent to
          <seealso marker="#monotonic_time/0">
          <c>erlang:monotonic_time()</c></seealso><c> +
          </c><seealso marker="#time_offset/0">
          <c>erlang:time_offset()</c></seealso>.</p>
        <note>
          <p>This time is <em>not</em> a monotonically increasing time
            in the general case. For more information, see the documentation of
            <seealso marker="time_correction#Time_Warp_Modes">
            time warp modes</seealso> in the User's Guide.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="system_time" arity="1"/>
      <fsummary>Current Erlang system time.</fsummary>
      <desc>
        <p>Returns current
          <seealso marker="time_correction#Erlang_System_Time">
          Erlang system time</seealso>
          converted into the <c><anno>Unit</anno></c> passed as argument.</p>
        <p>Calling <c>erlang:system_time(<anno>Unit</anno>)</c> is equivalent
          to <seealso marker="#convert_time_unit/3">
          <c>erlang:convert_time_unit</c></seealso><c>(</c><seealso
          marker="#system_time/0"><c>erlang:system_time()</c></seealso><c>,
          native, <anno>Unit</anno>)</c>.</p>
        <note>
          <p>This time is <em>not</em> a monotonically increasing time
            in the general case. For more information, see the documentation of
            <seealso marker="time_correction#Time_Warp_Modes">
            time warp modes</seealso> in the User's Guide.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="term_to_binary" arity="1"/>
      <fsummary>Encode a term to an Erlang external term format binary.
      </fsummary>
      <desc>
        <p>Returns a binary data object that is the result of encoding
          <c><anno>Term</anno></c> according to the
          <seealso marker="erts:erl_ext_dist">Erlang external
          term format.</seealso></p>
        <p>This can be used for various purposes, for example,
          writing a term to a file in an efficient way, or sending an
          Erlang term to some type of communications channel not
          supported by distributed Erlang.</p>
        <pre>
> <input>Bin = term_to_binary(hello).</input>
&lt;&lt;131,100,0,5,104,101,108,108,111>>
> <input>hello = binary_to_term(Bin).</input>
hello
</pre>
        <p>See also <seealso marker="#binary_to_term/1">
          <c>binary_to_term/1</c></seealso>.</p>
        <note>
          <p>There is no guarantee that this function will return
            the same encoded representation for the same term.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="term_to_binary" arity="2"/>
      <fsummary>Encode a term to en Erlang external term format binary.
      </fsummary>
      <desc>
        <p>Returns a binary data object that is the result of encoding
          <c><anno>Term</anno></c> according to the Erlang external
          term format.</p>
        <p>If option <c>compressed</c> is provided, the external term
          format is compressed. The compressed format is automatically
          recognized by <c>binary_to_term/1</c> as from Erlang/OTP R7B.</p>
        <p>A compression level can be specified by giving option
          <c>{compressed, <anno>Level</anno>}</c>.
          <c><anno>Level</anno></c> is an integer
          with range 0..9, where:</p>
        <list type="bulleted">
          <item><p><c>0</c> - No compression is done (it is the same as
            giving no <c>compressed</c> option).</p></item>
          <item><p><c>1</c> - Takes least time but may not compress
            as well as the higher levels.</p></item>
          <item><p><c>6</c> - Default level when option <c>compressed</c>
            is provided.</p></item>
          <item><p><c>9</c> - Takes most time and tries to produce a smaller
            result. Notice "tries" in the preceding sentence; depending
            on the input term, level 9 compression either does or does
            not produce a smaller result than level 1 compression.</p></item>
        </list>
        <p>Option <c>{minor_version, <anno>Version</anno>}</c>
          can be used to control some
          encoding details. This option was introduced in Erlang/OTP R11B-4.
          The valid values for <c><anno>Version</anno></c> are:</p>
	  <taglist>
	    <tag><c>0</c></tag>
	    <item>
              <p>Floats are encoded using a textual representation.
	      This option is useful to ensure that releases before Erlang/OTP
	      R11B-4 can decode resulting binary.</p>
	      <p>This version encode atoms that can be represented by a
	      latin1 string using latin1 encoding while only atoms that
	      cannot be represented by latin1 are encoded using utf8.</p>
	    </item>
	    <tag><c>1</c></tag>
	    <item>
              <p>This is as of Erlang/OTP 17.0 the default. It forces any floats
	      in the term to be encoded in a more space-efficient and exact way
	      (namely in the 64-bit IEEE format, rather than converted to a
	      textual representation). As from Erlang/OTP R11B-4,
	      <c>binary_to_term/1</c> can decode this representation.</p>
	      <p>This version encode atoms that can be represented by a
	      latin1 string using latin1 encoding while only atoms that
	      cannot be represented by latin1 are encoded using utf8.</p>
	    </item>
	    <tag><c>2</c></tag>
	    <item>
              <p>Drops usage of the latin1 atom encoding and unconditionally
	      use utf8 encoding for all atoms. This will be changed to the
	      default in a future major release of Erlang/OTP. Erlang/OTP
	      systems as of R16B can decode this representation.</p>
	    </item>
	  </taglist>
        <p>See also <seealso marker="#binary_to_term/1">
          <c>binary_to_term/1</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="throw" arity="1"/>
      <fsummary>Throw an exception.</fsummary>
      <desc>
        <p>A non-local return from a function. If evaluated within a
          <c>catch</c>, <c>catch</c> returns value <c><anno>Any</anno></c>.
          Example:</p>
        <pre>
> <input>catch throw({hello, there}).</input>
{hello,there}</pre>
        <p>Failure: <c>nocatch</c> if not evaluated within a catch.</p>
      </desc>
    </func>

    <func>
      <name name="time" arity="0"/>
      <fsummary>Current time.</fsummary>
      <desc>
        <p>Returns the current time as <c>{Hour, Minute, Second}</c>.</p>
        <p>The time zone and Daylight Saving Time correction depend on
          the underlying OS. Example:</p>
        <pre>
> <input>time().</input>
{9,42,44}</pre>
      </desc>
    </func>

    <func>
      <name name="time_offset" arity="0"/>
      <fsummary>Current time offset.</fsummary>
      <desc>
        <p>Returns the current time offset between
          <seealso marker="time_correction#Erlang_Monotonic_Time">
          Erlang monotonic time</seealso> and
          <seealso marker="time_correction#Erlang_System_Time">
          Erlang system time</seealso> in
          <c>native</c> <seealso marker="#type_time_unit">time unit</seealso>.
          Current time offset added to an Erlang monotonic time gives
          corresponding Erlang system time.</p>
        <p>The time offset may or may not change during operation depending
          on the <seealso marker="time_correction#Time_Warp_Modes">time
          warp mode</seealso> used.</p>
        <note>
          <p>A change in time offset can be observed at slightly
            different points in time by different processes.</p>
          <p>If the runtime system is in
            <seealso marker="time_correction#Multi_Time_Warp_Mode">multi-time
            warp mode</seealso>, the time offset is changed when
            the runtime system detects that the
            <seealso marker="time_correction#OS_System_Time">OS system
            time</seealso> has changed. The runtime system will, however,
            not detect this immediately when it occurs. A task checking
            the time offset is scheduled to execute at least once a minute;
            so, under normal operation this is to be detected within a
            minute, but during heavy load it can take longer time.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="time_offset" arity="1"/>
      <fsummary>Current time offset.</fsummary>
      <desc>
        <p>Returns the current time offset between
          <seealso marker="time_correction#Erlang_Monotonic_Time">
          Erlang monotonic time</seealso> and
          <seealso marker="time_correction#Erlang_System_Time">
          Erlang system time</seealso>
          converted into the <c><anno>Unit</anno></c> passed as argument.</p>
        <p>Same as calling
          <seealso marker="#convert_time_unit/3">
          <c>erlang:convert_time_unit</c></seealso><c>(</c><seealso marker="#time_offset/0">
          <c>erlang:time_offset()</c></seealso><c>, native,
          <anno>Unit</anno>)</c>
          however optimized for commonly used <c><anno>Unit</anno></c>s.</p>
      </desc>
    </func>

    <func>
      <name name="timestamp" arity="0"/>
      <fsummary>Current Erlang System time.</fsummary>
      <type name="timestamp"/>
      <desc>
        <p>Returns current
          <seealso marker="time_correction#Erlang_System_Time">
          Erlang system time</seealso>
          on the format <c>{MegaSecs, Secs, MicroSecs}</c>. This format is 
          the same as <seealso marker="kernel:os#timestamp/0">
          <c>os:timestamp/0</c></seealso>
          and the deprecated <seealso marker="#now/0">
          <c>erlang:now/0</c></seealso>
          use. The reason for the existence of <c>erlang:timestamp()</c> is
          purely to simplify use for existing code that assumes this time stamp
          format. Current Erlang system time can more efficiently be retrieved
          in the time unit of your choice using
          <seealso marker="#system_time/1">
          <c>erlang:system_time/1</c></seealso>.</p>
        <p>The <c>erlang:timestamp()</c> BIF is equivalent to:</p>
<code type="none">
timestamp() ->
    ErlangSystemTime = erlang:system_time(microsecond),
    MegaSecs = ErlangSystemTime div 1000000000000,
    Secs = ErlangSystemTime div 1000000 - MegaSecs*1000000,
    MicroSecs = ErlangSystemTime rem 1000000,
    {MegaSecs, Secs, MicroSecs}.</code>
        <p>It, however, uses a native implementation that does
          not build garbage on the heap and with slightly better
          performance.</p>
        <note>
          <p>This time is <em>not</em> a monotonically increasing time
            in the general case. For more information, see the documentation of
            <seealso marker="time_correction#Time_Warp_Modes">
            time warp modes</seealso> in the User's Guide.</p>
	</note>
      </desc>
    </func>

    <func>
      <name name="tl" arity="1"/>
      <fsummary>Tail of a list.</fsummary>
      <desc>
        <p>Returns the tail of <c><anno>List</anno></c>, that is,
          the list minus the first element, for example:</p>
        <pre>
> <input>tl([geesties, guilies, beasties]).</input>
[guilies, beasties]</pre>
        <p>Allowed in guard tests.</p>
        <p>Failure: <c>badarg</c> if <c><anno>List</anno></c>
          is the empty list <c>[]</c>.</p>
      </desc>
    </func>

    <func>
      <name name="trace" arity="3"/>
      <fsummary>Set trace flags for a process or processes.</fsummary>
      <type name="trace_flag"/>
      <desc>
        <p>Turns on (if <c><anno>How</anno> == true</c>) or off (if
          <c><anno>How</anno> == false</c>) the trace flags in
          <c><anno>FlagList</anno></c> for
          the process or processes represented by
          <c><anno>PidPortSpec</anno></c>.</p>
        <p><c><anno>PidPortSpec</anno></c> is either a process identifier
          (pid) for a local process, a port identifier,
          or one of the following atoms:</p>
        <taglist>
          <tag><c>all</c></tag>
          <item>All currently existing processes and ports and all that
            will be created in the future.
          </item>
          <tag><c>processes</c></tag>
          <item>All currently existing processes and all that will be created
            in the future.
          </item>
          <tag><c>ports</c></tag>
          <item>All currently existing ports and all that will be created in
            the future.
          </item>
          <tag><c>existing</c></tag>
          <item>All currently existing processes and ports.
          </item>
          <tag><c>existing_processes</c></tag>
          <item>All currently existing processes.
          </item>
          <tag><c>existing_ports</c></tag>
          <item>All currently existing ports.
          </item>
          <tag><c>new</c></tag>
          <item>All processes and ports that will be created in the future.
          </item>
          <tag><c>new_processes</c></tag>
          <item>All processes that will be created in the future.
          </item>
          <tag><c>new_ports</c></tag>
          <item>All ports that will be created in the future.
          </item>
        </taglist>
        <p><c><anno>FlagList</anno></c> can contain any number of the
          following flags (the "message tags" refers to the list of
          <seealso marker="#trace_3_trace_messages">
          <c>trace messages</c></seealso>):</p>
        <taglist>
          <tag><c>all</c></tag>
          <item>
            <p>Sets all trace flags except <c>tracer</c> and
              <c>cpu_timestamp</c>, which are in their nature different
              than the others.</p>
          </item>
          <tag><c>send</c></tag>
          <item>
            <p>Traces sending of messages.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_send">
              <c>send</c></seealso> and
              <seealso marker="#trace_3_trace_messages_send_to_non_existing_process">
              <c>send_to_non_existing_process</c></seealso>.</p>
          </item>
          <tag><c>'receive'</c></tag>
          <item>
            <p>Traces receiving of messages.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_receive">
                <c>'receive'</c></seealso>.</p>
          </item>
          <tag><c>call</c></tag>
          <item>
            <p>Traces certain function calls. Specify which function
              calls to trace by calling <seealso marker="#trace_pattern/3">
              <c>erlang:trace_pattern/3</c></seealso>.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_call">
              <c>call</c></seealso> and
              <seealso marker="#trace_3_trace_messages_return_from">
              <c>return_from</c></seealso>.</p>
          </item>
          <tag><c>silent</c></tag>
          <item>
            <p>Used with the <c>call</c> trace flag.
              The <c>call</c>, <c>return_from</c>, and <c>return_to</c>
              trace messages are inhibited if this flag is set, but they
              are executed as normal if there are match specifications.</p>
            <p>Silent mode is inhibited by executing
              <c>erlang:trace(_, false, [silent|_])</c>,
              or by a match specification executing the function
              <c>{silent, false}</c>.</p>
            <p>The <c>silent</c> trace flag facilitates setting up
              a trace on many or even all processes in the system.
              The trace can then be activated and deactivated using the match
              specification function <c>{silent,Bool}</c>, giving
              a high degree of control of which functions with which 
              arguments that trigger the trace.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_call">
              <c>call</c></seealso>,
              <seealso marker="#trace_3_trace_messages_return_from">
              <c>return_from</c></seealso>, and
              <seealso marker="#trace_3_trace_messages_return_to">
              <c>return_to</c></seealso>. Or rather, the absence of.</p>
          </item>
          <tag><c>return_to</c></tag>
          <item>
            <p>Used with the <c>call</c> trace flag.
              Traces the return from a traced function back to
              its caller. Only works for functions traced with
              option <c>local</c> to <seealso marker="#trace_pattern/3">
              <c>erlang:trace_pattern/3</c></seealso>.</p>
            <p>The semantics is that a trace message is sent when a
              call traced function returns, that is, when a
              chain of tail recursive calls ends. Only one trace
              message is sent per chain of tail recursive calls,
              so the properties of tail recursiveness for
              function calls are kept while tracing with this flag.
              Using <c>call</c> and <c>return_to</c> trace together
              makes it possible to know exactly in which function a
              process executes at any time.</p>
            <p>To get trace messages containing return values from
              functions, use the <c>{return_trace}</c> match
              specification action instead.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_return_to">
              <c>return_to</c></seealso>.</p>
          </item>
          <tag><c>procs</c></tag>
          <item>
            <p>Traces process-related events.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_spawn">
              <c>spawn</c></seealso>,
              <seealso marker="#trace_3_trace_messages_spawned">
              <c>spawned</c></seealso>,
              <seealso marker="#trace_3_trace_messages_exit">
              <c>exit</c></seealso>,
              <seealso marker="#trace_3_trace_messages_register">
              <c>register</c></seealso>,
              <seealso marker="#trace_3_trace_messages_unregister">
              <c>unregister</c></seealso>,
              <seealso marker="#trace_3_trace_messages_link">
              <c>link</c></seealso>,
              <seealso marker="#trace_3_trace_messages_unlink">
              <c>unlink</c></seealso>,
              <seealso marker="#trace_3_trace_messages_getting_linked">
              <c>getting_linked</c></seealso>, and
              <seealso marker="#trace_3_trace_messages_getting_unlinked">
              <c>getting_unlinked</c></seealso>.</p>
          </item>
          <tag><c>ports</c></tag>
          <item>
            <p>Traces port-related events.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_open">
              <c>open</c></seealso>,
              <seealso marker="#trace_3_trace_messages_closed">
              <c>closed</c></seealso>,
              <seealso marker="#trace_3_trace_messages_register">
              <c>register</c></seealso>,
              <seealso marker="#trace_3_trace_messages_unregister">
              <c>unregister</c></seealso>,
              <seealso marker="#trace_3_trace_messages_getting_linked">
              <c>getting_linked</c></seealso>, and
              <seealso marker="#trace_3_trace_messages_getting_unlinked">
              <c>getting_unlinked</c></seealso>.</p>
          </item>
          <tag><c>running</c></tag>
          <item>
            <p>Traces scheduling of processes.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_in_proc">
              <c>in</c></seealso> and
              <seealso marker="#trace_3_trace_messages_out_proc">
              <c>out</c></seealso>.</p>
          </item>
          <tag><c>exiting</c></tag>
          <item>
            <p>Traces scheduling of exiting processes.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_in_exiting_proc">
              <c>in_exiting</c></seealso>,
              <seealso marker="#trace_3_trace_messages_out_exiting_proc">
              <c>out_exiting</c></seealso>, and
              <seealso marker="#trace_3_trace_messages_out_exited_proc">
              <c>out_exited</c></seealso>.</p>
          </item>
          <tag><c>running_procs</c></tag>
          <item>
            <p>Traces scheduling of processes just like <c>running</c>.
              However, this option also includes schedule events when the
              process executes within the context of a port without
              being scheduled out itself.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_in_proc">
              <c>in</c></seealso> and
              <seealso marker="#trace_3_trace_messages_out_proc">
              <c>out</c></seealso>.</p>
          </item>
          <tag><c>running_ports</c></tag>
          <item>
            <p>Traces scheduling of ports.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_in_port">
              <c>in</c></seealso> and
              <seealso marker="#trace_3_trace_messages_out_port">
              <c>out</c></seealso>.</p>
          </item>
          <tag><c>garbage_collection</c></tag>
          <item>
            <p>Traces garbage collections of processes.</p>
            <p>Message tags:
              <seealso marker="#trace_3_trace_messages_gc_minor_start">
              <c>gc_minor_start</c></seealso>,
              <seealso marker="#trace_3_trace_messages_gc_max_heap_size">
              <c>gc_max_heap_size</c></seealso>, and
              <seealso marker="#trace_3_trace_messages_gc_minor_end">
              <c>gc_minor_end</c></seealso>.</p>
          </item>
          <tag><c>timestamp</c></tag>
          <item>
            <p>Includes a time stamp in all trace messages. The
              time stamp (Ts) has the same form as returned by
              <c>erlang:now()</c>.</p>
          </item>
          <tag><c>cpu_timestamp</c></tag>
          <item>
            <p>A global trace flag for the Erlang node that makes all
              trace time stamps using flag <c>timestamp</c> to be
              in CPU time, not wall clock time. That is, <c>cpu_timestamp</c>
              is not be used if <c>monotonic_timestamp</c> or
              <c>strict_monotonic_timestamp</c> is enabled.
              Only allowed with <c><anno>PidPortSpec</anno>==all</c>. If the
              host machine OS does not support high-resolution
              CPU time measurements, <c>trace/3</c> exits with
              <c>badarg</c>. Notice that most OS do
              not synchronize this value across cores, so be prepared
              that time can seem to go backwards when using this option.</p>
          </item>
          <tag><c>monotonic_timestamp</c></tag>
          <item>
            <p>Includes an
              <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
              monotonic time</seealso> time stamp in all trace messages. The
              time stamp (Ts) has the same format and value as produced by
              <seealso marker="#monotonic_time-1">
              <c>erlang:monotonic_time(nanosecond)</c></seealso>.
              This flag overrides flag <c>cpu_timestamp</c>.</p>
          </item>
          <tag><c>strict_monotonic_timestamp</c></tag>
          <item>
            <p>Includes an time stamp consisting of
              <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
              monotonic time</seealso> and a monotonically increasing
              integer in all trace messages. The time stamp (Ts) has the
              same format and value as produced by <c>{</c>
              <seealso marker="#monotonic_time-1">
              <c>erlang:monotonic_time(nanosecond)</c></seealso><c>,</c>
              <seealso marker="#unique_integer-1">
              <c>erlang:unique_integer([monotonic])</c></seealso><c>}</c>.
              This flag overrides flag <c>cpu_timestamp</c>.</p>
          </item>
          <tag><c>arity</c></tag>
          <item>
            <p>Used with the <c>call</c> trace flag.
              <c>{M, F, Arity}</c> is specified instead of
              <c>{M, F, Args}</c> in call trace messages.</p>
          </item>
          <tag><c>set_on_spawn</c></tag>
          <item>
            <p>Makes any process created by a traced process inherit
              its trace flags, including flag <c>set_on_spawn</c>.</p>
          </item>
          <tag><c>set_on_first_spawn</c></tag>
          <item>
            <p>Makes the first process created by a traced process
              inherit its trace flags, excluding flag
              <c>set_on_first_spawn</c>.</p>
          </item>
          <tag><c>set_on_link</c></tag>
          <item>
            <p>Makes any process linked by a traced process inherit its
              trace flags, including flag <c>set_on_link</c>.</p>
          </item>
          <tag><c>set_on_first_link</c></tag>
          <item>
            <p>Makes the first process linked to by a traced process
              inherit its trace flags, excluding flag
              <c>set_on_first_link</c>.</p>
          </item>
          <tag><c>{tracer, Tracer}</c></tag>
          <item>
            <p>Specifies where to send the trace messages. <c>Tracer</c>
              must be the process identifier of a local process
              or the port identifier of a local port.</p>
          </item>
          <tag><c>{tracer, TracerModule, TracerState}</c></tag>
          <item>
            <p>Specifies that a tracer module is to be called
              instead of sending a trace message. The tracer module
              can then ignore or change the trace message. For more details
              on how to write a tracer module, see
              <seealso marker="erts:erl_tracer"><c>erl_tracer(3)</c></seealso>.</p>
          </item>
        </taglist>
        <p>If no <c>tracer</c> is specified, the calling process
          receives all the trace messages.</p>
        <p>The effect of combining <c>set_on_first_link</c> with
          <c>set_on_link</c> is the same as
          <c>set_on_first_link</c> alone. Likewise for
          <c>set_on_spawn</c> and <c>set_on_first_spawn</c>.</p>
        <p>The tracing process receives the <em>trace messages</em> described
          in the following list. <c>Pid</c> is the process identifier of the
          traced process in which the traced event has occurred. The
          third tuple element is the message tag.</p>
        <p>If flag <c>timestamp</c>, <c>strict_monotonic_timestamp</c>, or
          <c>monotonic_timestamp</c> is specified, the first tuple
          element is <c>trace_ts</c> instead, and the time stamp
          is added as an extra element last in the message tuple. If
          multiple time stamp flags are passed, <c>timestamp</c> has
          precedence over <c>strict_monotonic_timestamp</c>, which
          in turn has precedence over <c>monotonic_timestamp</c>. All
          time stamp flags are remembered, so if two are passed
          and the one with highest precedence later is disabled,
          the other one becomes active.</p>
        <p>Trace messages:</p>
        <marker id="trace_3_trace_messages"></marker>
        <taglist>
          <tag>
            <marker id="trace_3_trace_messages_send"></marker>
            <c>{trace, PidPort, send, Msg, To}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> sends message <c>Msg</c> to
              process <c>To</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_send_to_non_existing_process"/>
            <c>{trace, PidPort, send_to_non_existing_process, Msg, To}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> sends message <c>Msg</c> to
              the non-existing process <c>To</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_receive"></marker>
            <c>{trace, PidPort, 'receive', Msg}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> receives message <c>Msg</c>.
              If <c>Msg</c> is set to time-out, a receive
              statement can have timed out, or the process received
              a message with the payload <c>timeout</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_call"></marker>
            <c>{trace, Pid, call, {M, F, Args}}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> calls a traced function. The return
              values of calls are never supplied, only the call and its
              arguments.</p>
            <p>Trace flag <c>arity</c> can be used to
              change the contents of this message, so that <c>Arity</c>
              is specified instead of <c>Args</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_return_to"></marker>
            <c>{trace, Pid, return_to, {M, F, Arity}}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> returns <em>to</em> the specified
              function. This trace message is sent if both
              the flags <c>call</c> and <c>return_to</c> are set,
              and the function is set to be traced on <em>local</em>
              function calls. The message is only sent when returning
              from a chain of tail recursive function calls, where at
              least one call generated a <c>call</c> trace message
              (that is, the functions match specification matched, and
              <c>{message, false}</c> was not an action).</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_return_from"></marker>
            <c>{trace, Pid, return_from, {M, F, Arity}, ReturnValue}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> returns <em>from</em> the specified
              function. This trace message is sent if flag <c>call</c>
              is set, and the function has a match specification
              with a <c>return_trace</c> or <c>exception_trace</c> action.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_exception_from"></marker>
            <c>{trace, Pid, exception_from, {M, F, Arity}, {Class, Value}}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> exits <em>from</em> the specified
              function because of an exception. This trace message is
              sent if flag <c>call</c> is set, and the function has 
              a match specification with an <c>exception_trace</c> action.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_spawn"></marker>
            <c>{trace, Pid, spawn, Pid2, {M, F, Args}}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> spawns a new process <c>Pid2</c> with
              the specified function call as entry point.</p>
            <p><c>Args</c> is supposed to be the argument list,
              but can be any term if the spawn is erroneous.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_spawned"></marker>
            <c>{trace, Pid, spawned, Pid2, {M, F, Args}}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> is spawned by process <c>Pid2</c> with
              the specified function call as entry point.</p>
            <p><c>Args</c> is supposed to be the argument list,
              but can be any term if the spawn is erroneous.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_exit"></marker>
            <c>{trace, Pid, exit, Reason}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> exits with reason <c>Reason</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_register"></marker>
            <c>{trace, PidPort, register, RegName}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> gets the name <c>RegName</c> registered.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_unregister"></marker>
            <c>{trace, PidPort, unregister, RegName}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> gets the name <c>RegName</c> unregistered.
              This is done automatically when a registered
              process or port exits.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_link"></marker>
            <c>{trace, Pid, link, Pid2}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> links to a process <c>Pid2</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_unlink"></marker>
            <c>{trace, Pid, unlink, Pid2}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> removes the link from a process
              <c>Pid2</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_getting_linked"></marker>
            <c>{trace, PidPort, getting_linked, Pid2}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> gets linked to a process <c>Pid2</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_getting_unlinked"></marker>
            <c>{trace, PidPort, getting_unlinked, Pid2}</c>
          </tag>
          <item>
            <p>When <c>PidPort</c> gets unlinked from a process <c>Pid2</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_exit"></marker>
            <c>{trace, Pid, exit, Reason}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> exits with reason <c>Reason</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_open"></marker>
            <c>{trace, Port, open, Pid, Driver}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> opens a new port <c>Port</c> with
              the running <c>Driver</c>.</p>
            <p><c>Driver</c> is the name of the driver as an atom.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_closed"></marker>
            <c>{trace, Port, closed, Reason}</c>
          </tag>
          <item>
            <p>When <c>Port</c> closes with <c>Reason</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_in_proc"></marker>
            <marker id="trace_3_trace_messages_in_exiting_proc"></marker>
            <c>{trace, Pid, in | in_exiting, {M, F, Arity} | 0}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> is scheduled to run. The process
              runs in function <c>{M, F, Arity}</c>. On some rare
              occasions, the current function cannot be determined,
              then the last element is <c>0</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_out_proc"></marker>
            <marker id="trace_3_trace_messages_out_exiting_proc"></marker>
            <marker id="trace_3_trace_messages_out_exited_proc"></marker>
            <c>{trace, Pid, out | out_exiting | out_exited, {M, F, Arity}
            | 0}</c>
          </tag>
          <item>
            <p>When <c>Pid</c> is scheduled out. The process was
              running in function {M, F, Arity}. On some rare occasions,
              the current function cannot be determined, then the last
              element is <c>0</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_in_port"></marker>
            <c>{trace, Port, in, Command | 0}</c>
          </tag>
          <item>
            <p>When <c>Port</c> is scheduled to run. <c>Command</c> is the
              first thing the port will execute, it can however run several
              commands before being scheduled out. On some rare
              occasions, the current function cannot be determined,
              then the last element is <c>0</c>.</p>
            <p>The possible commands are <c>call</c>, <c>close</c>,
              <c>command</c>, <c>connect</c>, <c>control</c>, <c>flush</c>,
              <c>info</c>, <c>link</c>, <c>open</c>, and <c>unlink</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_out_port"></marker>
            <c>{trace, Port, out, Command | 0}</c>
          </tag>
          <item>
            <p>When <c>Port</c> is scheduled out. The last command run
              was <c>Command</c>. On some rare occasions,
              the current function cannot be determined, then the last
              element is <c>0</c>. <c>Command</c> can contain the same
              commands as <c>in</c></p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_gc_minor_start"></marker>
            <c>{trace, Pid, gc_minor_start, Info}</c>
          </tag>
          <item>
          <marker id="gc_minor_start"></marker>
            <p>Sent when a young garbage collection is about to be started.
              <c>Info</c> is a list of two-element tuples, where
              the first element is a key, and the second is the value.
              Do not depend on any order of the tuples.
              The following keys are defined:</p>
            <taglist>
              <tag><c>heap_size</c></tag>
              <item>The size of the used part of the heap.</item>
              <tag><c>heap_block_size</c></tag>
              <item>The size of the memory block used for storing
                the heap and the stack.</item>
              <tag><c>old_heap_size</c></tag>
              <item>The size of the used part of the old heap.</item>
              <tag><c>old_heap_block_size</c></tag>
              <item>The size of the memory block used for storing
                the old heap.</item>
              <tag><c>stack_size</c></tag>
              <item>The size of the stack.</item>
              <tag><c>recent_size</c></tag>
              <item>The size of the data that survived the previous garbage
                collection.</item>
              <tag><c>mbuf_size</c></tag>
              <item>The combined size of message buffers associated with
                the process.</item>
              <tag><c>bin_vheap_size</c></tag>
              <item>The total size of unique off-heap binaries referenced
                from the process heap.</item>
              <tag><c>bin_vheap_block_size</c></tag>
              <item>The total size of binaries allowed in the virtual
                heap in the process before doing a garbage collection.</item>
              <tag><c>bin_old_vheap_size</c></tag>
              <item>The total size of unique off-heap binaries referenced
                from the process old heap.</item>
              <tag><c>bin_old_vheap_block_size</c></tag>
              <item>The total size of binaries allowed in the virtual
                old heap in the process before doing a garbage
                collection.</item>
            </taglist>
            <p>All sizes are in words.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_gc_max_heap_size"></marker>
            <c>{trace, Pid, gc_max_heap_size, Info}</c>
          </tag>
          <item>
            <p>Sent when the <seealso marker="#process_flag_max_heap_size">
              <c>max_heap_size</c></seealso>
              is reached during garbage collection. <c>Info</c> contains the
              same kind of list as in message <c>gc_start</c>,
              but the sizes reflect the sizes that triggered
              <c>max_heap_size</c> to be reached.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_gc_minor_end"></marker>
            <c>{trace, Pid, gc_minor_end, Info}</c>
          </tag>
          <item>
            <p>Sent when young garbage collection is finished. <c>Info</c>
              contains the same kind of list as in message
              <c>gc_minor_start</c>,
              but the sizes reflect the new sizes after
              garbage collection.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_gc_major_start"></marker>
            <c>{trace, Pid, gc_major_start, Info}</c>
          </tag>
          <item>
            <p>Sent when fullsweep garbage collection is about to be started.
              <c>Info</c> contains the same kind of list as in message
              <c>gc_minor_start</c>.</p>
          </item>
          <tag>
            <marker id="trace_3_trace_messages_gc_major_end"></marker>
            <c>{trace, Pid, gc_major_end, Info}</c>
          </tag>
          <item>
            <p>Sent when fullsweep garbage collection is finished. <c>Info</c>
              contains the same kind of list as in message
              <c>gc_minor_start</c>, but the sizes reflect the new sizes after
              a fullsweep garbage collection.</p>
          </item>
        </taglist>
        <p>If the tracing process/port dies or the tracer module returns
          <c>remove</c>, the flags are silently removed.</p>
        <p>Each process can only be traced by one tracer. Therefore,
          attempts to trace an already traced process fail.</p>
        <p>Returns a number indicating the number of processes that
          matched <c><anno>PidPortSpec</anno></c>.
          If <c><anno>PidPortSpec</anno></c> is a process
          identifier, the return value is <c>1</c>.
          If <c><anno>PidPortSpec</anno></c>
          is <c>all</c> or <c>existing</c>, the return value is
          the number of processes running.
          If <c><anno>PidPortSpec</anno></c> is <c>new</c>, the return value is
          <c>0</c>.</p>
        <p>Failure: <c>badarg</c> if the specified arguments are
          not supported. For example, <c>cpu_timestamp</c> is not
          supported on all platforms.</p>
      </desc>
    </func>

    <func>
      <name name="trace_delivered" arity="1"/>
      <fsummary>Notification when trace has been delivered.</fsummary>
      <desc>
        <p>The delivery of trace messages (generated by
          <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>,
          <seealso marker="kernel:seq_trace"><c>seq_trace(3)</c></seealso>,
          or <seealso marker="#system_profile/2">
          <c>erlang:system_profile/2</c></seealso>)
          is dislocated on the time-line
          compared to other events in the system. If you know that
          <c><anno>Tracee</anno></c> has passed some specific point
          in its execution,
          and you want to know when at least all trace messages
          corresponding to events up to this point have reached the
          tracer, use <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>.</p>
        <p>When it is guaranteed that all trace messages are delivered to
          the tracer up to the point that <c><anno>Tracee</anno></c> reached
          at the time of the call to
          <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>, then a
          <c>{trace_delivered, <anno>Tracee</anno>, <anno>Ref</anno>}</c>
          message is sent to the caller of
          <c>erlang:trace_delivered(<anno>Tracee</anno>)</c> .</p>
        <p>Notice that message <c>trace_delivered</c> does <em>not</em>
          imply that trace messages have been delivered.
          Instead it implies that all trace messages that
          <em>are to be delivered</em> have been delivered.
          It is not an error if <c><anno>Tracee</anno></c> is not, and
          has not been traced by someone, but if this is the case,
          <em>no</em> trace messages have been delivered when the
          <c>trace_delivered</c> message arrives.</p>
        <p>Notice that <c><anno>Tracee</anno></c> must refer
          to a process currently
          or previously existing on the same node as the caller of
          <c>erlang:trace_delivered(<anno>Tracee</anno>)</c> resides on.
          The special <c><anno>Tracee</anno></c> atom <c>all</c>
          denotes all processes that currently are traced in the node.</p>
        <p>When used together with a <seealso marker="erts:erl_tracer">
          Tracer Module</seealso>, any message sent in the trace callback
          is guaranteed to have reached its recipient before the
          <c>trace_delivered</c> message is sent.</p>
        <p>Example: Process <c>A</c> is <c><anno>Tracee</anno></c>,
          port <c>B</c> is tracer, and process <c>C</c> is the port
          owner of <c>B</c>. <c>C</c> wants to close <c>B</c> when
          <c>A</c> exits. To ensure that the trace is not truncated,
          <c>C</c> can call <c>erlang:trace_delivered(A)</c> when
          <c>A</c> exits, and wait for message <c>{trace_delivered, A,
          <anno>Ref</anno>}</c> before closing <c>B</c>.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Tracee</anno></c>
          does not refer to a
          process (dead or alive) on the same node as the caller of
          <c>erlang:trace_delivered(<anno>Tracee</anno>)</c> resides on.</p>
      </desc>
    </func>

    <func>
      <name name="trace_info" arity="2"/>
      <fsummary>Trace information about a process or function.</fsummary>
      <type name="trace_info_return"/>
      <type name="trace_info_item_result"/>
      <type name="trace_info_flag"/>
      <type name="trace_match_spec"/>
      <type name="match_variable"/>
      <type_desc name="match_variable">
        Approximation of '$1' | '$2' | '$3' | ...
      </type_desc>
      <desc>
        <p>Returns trace information about a port, process, function, or
          event.</p>
        <p><em>To get information about a port or process</em>,
          <c><anno>PidPortFuncEvent</anno></c> is to
          be a process identifier (pid), port identifier, or one of
          the atoms <c>new</c>, <c>new_processes</c>, or <c>new_ports</c>. The
          atom <c>new</c> or <c>new_processes</c> means that the default trace
          state for processes to be created is returned. The atom
          <c>new_ports</c> means that the default trace state for ports to be
          created is returned.</p>
        <p>Valid <c>Item</c>s for ports and processes:</p>
        <taglist>
          <tag><c>flags</c></tag>
          <item>
            <p>Returns a list of atoms indicating what kind of traces is
              enabled for the process. The list is empty if no
              traces are enabled, and one or more of the followings
              atoms if traces are enabled: <c>send</c>,
              <c>'receive'</c>, <c>set_on_spawn</c>, <c>call</c>,
              <c>return_to</c>, <c>procs</c>, <c>ports</c>,
              <c>set_on_first_spawn</c>,
              <c>set_on_link</c>, <c>running</c>, <c>running_procs</c>,
              <c>running_ports</c>, <c>silent</c>, <c>exiting</c>,
              <c>monotonic_timestamp</c>, <c>strict_monotonic_timestamp</c>,
              <c>garbage_collection</c>, <c>timestamp</c>, and
              <c>arity</c>. The order is arbitrary.</p>
          </item>
          <tag><c>tracer</c></tag>
          <item>
            <p>Returns the identifier for process, port, or a tuple containing
              the tracer module and tracer state tracing this
              process. If this process is not traced, the return
              value is <c>[]</c>.</p>
          </item>
        </taglist>
        <p><em>To get information about a function</em>,
          <c><anno>PidPortFuncEvent</anno></c> is to
          be the three-element tuple <c>{Module, Function, Arity}</c> or
          the atom <c>on_load</c>. No wildcards are allowed. Returns
          <c>undefined</c> if the function does not exist, or
          <c>false</c> if the function is not traced.
          If <c><anno>PidPortFuncEvent</anno></c>
          is <c>on_load</c>, the information returned refers to
          the default value for code that will be loaded.</p>
        <p>Valid <c>Item</c>s for functions:</p>
        <taglist>
          <tag><c>traced</c></tag>
          <item>
            <p>Returns <c>global</c> if this function is traced on
              global function calls, <c>local</c> if this function is
              traced on local function calls (that is, local and global
              function calls), and <c>false</c> if local or
              global function calls are not traced.</p>
          </item>
          <tag><c>match_spec</c></tag>
          <item>
            <p>Returns the match specification for this function, if it
              has one. If the function is locally or globally traced but
              has no match specification defined, the returned value
              is <c>[]</c>.</p>
          </item>
          <tag><c>meta</c></tag>
          <item>
            <p>Returns the meta-trace tracer process, port, or trace module
              for this function, if it has one. If the function is not
              meta-traced, the returned value is <c>false</c>. If
              the function is meta-traced but has once detected that
              the tracer process is invalid, the returned value is
              <c>[]</c>.</p>
          </item>
          <tag><c>meta_match_spec</c></tag>
          <item>
            <p>Returns the meta-trace match specification for this
              function, if it has one. If the function is meta-traced
              but has no match specification defined, the returned
              value is <c>[]</c>.</p>
          </item>
          <tag><c>call_count</c></tag>
          <item>
            <p>Returns the call count value for this function or
              <c>true</c> for the pseudo function <c>on_load</c> if call
              count tracing is active. Otherwise <c>false</c> is returned.</p>
            <p>See also <seealso marker="#trace_pattern/3">
              <c>erlang:trace_pattern/3</c></seealso>.</p>
          </item>
          <tag><c>call_time</c></tag>
          <item>
            <p>Returns the call time values for this function or
              <c>true</c> for the pseudo function <c>on_load</c> if call
              time tracing is active. Otherwise <c>false</c> is returned.
              The call time values returned, <c>[{Pid, Count, S, Us}]</c>,
              is a list of each process that executed the function
              and its specific counters.</p>
            <p>See also
              <seealso marker="#trace_pattern/3">
              <c>erlang:trace_pattern/3</c></seealso>.</p>
          </item>
          <tag><c>all</c></tag>
          <item>
            <p>Returns a list containing the
              <c>{<anno>Item</anno>, Value}</c> tuples
              for all other items, or returns <c>false</c> if no tracing
              is active for this function.</p>
          </item>
        </taglist>
        <p><em>To get information about an event</em>,
          <c><anno>PidPortFuncEvent</anno></c> is to
          be one of the atoms <c>send</c> or <c>'receive'</c>.</p>
        <p>One valid <c>Item</c> for events exists:</p>
        <taglist>
          <tag><c>match_spec</c></tag>
          <item>
            <p>Returns the match specification for this event, if it
              has one, or <c>true</c> if no match specification has been
              set.</p>
          </item>
        </taglist>
        <p>The return value is <c>{<anno>Item</anno>, Value}</c>, where
          <c>Value</c> is the requested information as described earlier.
          If a pid for a dead process was specified, or the name of a
          non-existing function, <c>Value</c> is <c>undefined</c>.</p>
      </desc>
    </func>

    <func>
      <name name="trace_pattern" arity="2" clause_i="1"/>
      <fsummary>Set trace patterns for call, send, or 'receive' tracing.
      </fsummary>
      <type name="trace_pattern_mfa"/>
      <type name="trace_match_spec"/>
      <type_desc name="match_variable">
        Approximation of '$1' | '$2' | '$3' | ...
      </type_desc>
      <type name="match_variable"/>
      <desc>
        <p>The same as
          <seealso marker="#trace_pattern/3">
          <c>erlang:trace_pattern(Event, MatchSpec, [])</c></seealso>,
          retained for backward compatibility.</p>
      </desc>
    </func>

    <func>
      <name name="trace_pattern" arity="3" clause_i="1"/>
      <fsummary>Set trace pattern for message sending.</fsummary>
      <type name="trace_match_spec"/>
      <type name="match_variable"/>
      <type_desc name="match_variable">
        Approximation of '$1' | '$2' | '$3' | ...
      </type_desc>
      <desc>
        <p>Sets trace pattern for <em>message sending</em>.
          Must be combined with
          <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>
          to set the <c>send</c> trace flag for one or more processes.
          By default all messages sent from <c>send</c> traced processes
          are traced. To limit
          traced send events based on the message content, the sender
          and/or the receiver, use <c>erlang:trace_pattern/3</c>.</p>
        <p>Argument <c><anno>MatchSpec</anno></c> can take the
          following forms:</p>
        <taglist>
          <tag><c><anno>MatchSpecList</anno></c></tag>
          <item>
            <p>A list of match specifications. The matching is done
              on the list <c>[Receiver, Msg]</c>. <c>Receiver</c>
              is the process or port identity of the receiver and
              <c>Msg</c> is the message term. The pid of the sending
              process can be accessed with the guard function
              <c>self/0</c>. An empty list is the same as <c>true</c>.
              For more information, see section
              <seealso marker="erts:match_spec">
              Match Specifications in Erlang</seealso> in the User's Guide.</p>
          </item>
          <tag><c>true</c></tag>
          <item>
            <p>Enables tracing for all sent messages (from <c>send</c>
              traced processes). Any match specification is
              removed. <em>This is the default</em>.</p>
          </item>
          <tag><c>false</c></tag>
          <item>
            <p>Disables tracing for all sent messages.
              Any match specification is removed.</p>
          </item>
        </taglist>
        <p>Argument <c><anno>FlagList</anno></c> must be <c>[]</c>
          for send tracing.</p>
        <p>The return value is always <c>1</c>.</p>
        <p>Examples:</p>
        <p>Only trace messages to a specific process <c>Pid</c>:</p>
        <pre>
> <input>erlang:trace_pattern(send, [{[Pid, '_'],[],[]}], []).</input>
1</pre>
        <p>Only trace messages matching <c>{reply, _}</c>:</p>
        <pre>
> <input>erlang:trace_pattern(send, [{['_', {reply,'_'}],[],[]}], []).</input>
1</pre>
        <p>Only trace messages sent to the sender itself:</p>
        <pre>
> <input>erlang:trace_pattern(send, [{['$1', '_'],[{'=:=','$1',{self}}],[]}], []).</input>
1</pre>
        <p>Only trace messages sent to other nodes:</p>
        <pre>
> <input>erlang:trace_pattern(send, [{['$1', '_'],[{'=/=',{node,'$1'},{node}}],[]}], []).</input>
1</pre>
        <note>
          <p>A match specification for <c>send</c> trace can use
            all guard and body functions except <c>caller</c>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="trace_pattern" arity="3" clause_i="2"/>
      <fsummary>Set trace pattern for tracing of message receiving.</fsummary>
      <type name="trace_match_spec"/>
      <type name="match_variable"/>
      <type_desc name="match_variable">
        Approximation of '$1' | '$2' | '$3' | ...
      </type_desc>
      <desc>
        <p>Sets trace pattern for <em>message receiving</em>.
          Must be combined with
          <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>
          to set the <c>'receive'</c> trace flag for one or more processes.
          By default all messages received by <c>'receive'</c> traced
          processes are traced. To limit
          traced receive events based on the message content, the sender
          and/or the receiver, use <c>erlang:trace_pattern/3</c>.</p>
        <p>Argument <c><anno>MatchSpec</anno></c> can take the
          following forms:</p>
        <taglist>
          <tag><c><anno>MatchSpecList</anno></c></tag>
          <item>
            <p>A list of match specifications. The matching is done
              on the list <c>[Node, Sender, Msg]</c>. <c>Node</c>
              is the node name of the sender. <c>Sender</c> is the
              process or port identity of the sender, or the atom
              <c>undefined</c> if the sender is not known (which can
              be the case for remote senders). <c>Msg</c> is the
              message term. The pid of the receiving process can be
              accessed with the guard function <c>self/0</c>. An empty
              list is the same as <c>true</c>. For more information, see
              section <seealso marker="erts:match_spec">
              Match Specifications in Erlang</seealso> in the User's Guide.</p>
          </item>
          <tag><c>true</c></tag>
          <item>
            <p>Enables tracing for all received messages (to <c>'receive'</c>
              traced processes). Any match specification is
              removed. <em>This is the default</em>.</p>
          </item>
          <tag><c>false</c></tag>
          <item>
            <p>Disables tracing for all received messages.
              Any match specification is removed.</p>
          </item>
        </taglist>
        <p>Argument <c><anno>FlagList</anno></c> must be <c>[]</c>
          for receive tracing.</p>
        <p>The return value is always <c>1</c>.</p>
        <p>Examples:</p>
        <p>Only trace messages from a specific process <c>Pid</c>:</p>
        <pre>
> <input>erlang:trace_pattern('receive', [{['_',Pid, '_'],[],[]}], []).</input>
1</pre>
        <p>Only trace messages matching <c>{reply, _}</c>:</p>
        <pre>
> <input>erlang:trace_pattern('receive', [{['_','_', {reply,'_'}],[],[]}], []).</input>
1</pre>
        <p>Only trace messages from other nodes:</p>
        <pre>
> <input>erlang:trace_pattern('receive', [{['$1', '_', '_'],[{'=/=','$1',{node}}],[]}], []).</input>
1</pre>
        <note>
          <p>A match specification for <c>'receive'</c> trace can
            use all guard and body functions except <c>caller</c>,
            <c>is_seq_trace</c>, <c>get_seq_token</c>, <c>set_seq_token</c>,
            <c>enable_trace</c>, <c>disable_trace</c>, <c>trace</c>,
            <c>silent</c>, and <c>process_dump</c>.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="trace_pattern" arity="3" clause_i="3"/>
      <fsummary>Set trace patterns for tracing of function calls.</fsummary>
      <type name="trace_pattern_mfa"/>
      <type name="trace_match_spec"/>
      <type name="trace_pattern_flag"/>
      <type name="match_variable"/>
      <type_desc name="match_variable">
        Approximation of '$1' | '$2' | '$3' | ...
      </type_desc>
      <desc>
        <p>Enables or disables <em>call tracing</em> for one or more functions.
          Must be combined with
          <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>
          to set the <c>call</c> trace flag
          for one or more processes.</p>
        <p>Conceptually, call tracing works as follows. Inside
          the Erlang virtual machine, a set of processes and
          a set of functions are to be traced. If a traced process
          calls a traced function, the trace action is taken.
          Otherwise, nothing happens.</p>
        <p>To add or remove one or more processes to the set of traced
          processes, use
          <seealso marker="#trace/3"><c>erlang:trace/3</c></seealso>.</p>
        <p>To add or remove functions to the set of traced
          functions, use <c>erlang:trace_pattern/3</c>.</p>
        <p>The BIF <c>erlang:trace_pattern/3</c> can also add match
          specifications to a function. A match specification
          comprises a pattern that the function arguments must
          match, a guard expression that must evaluate to <c>true</c>,
          and an action to be performed. The default action is to send a
          trace message. If the pattern does not match or the guard
          fails, the action is not executed.</p>
        <p>Argument <c><anno>MFA</anno></c> is to be a tuple, such as
          <c>{Module, Function, Arity}</c>, or the atom <c>on_load</c>
          (described below). It can be the module, function,
          and arity for a function (or a BIF in any module).
          The atom <c>'_'</c> can be used as a wildcard in any of the
          following ways:</p>
        <taglist>
          <tag><c>{Module,Function,'_'}</c></tag>
          <item>
            <p>All functions of any arity named <c>Function</c>
              in module <c>Module</c>.</p>
          </item>
          <tag><c>{Module,'_','_'}</c></tag>
          <item>
            <p>All functions in module <c>Module</c>.</p>
          </item>
          <tag><c>{'_','_','_'}</c></tag>
          <item>
            <p>All functions in all loaded modules.</p>
          </item>
        </taglist>
        <p>Other combinations, such as <c>{Module,'_',Arity}</c>, are
          not allowed. Local functions match wildcards only if
          option <c>local</c> is in <c><anno>FlagList</anno></c>.</p>
        <p>If argument <c><anno>MFA</anno></c> is the atom <c>on_load</c>,
          the match specification and flag list are used on all
          modules that are newly loaded.</p>
        <p>Argument <c><anno>MatchSpec</anno></c> can take the
          following forms:</p>
        <taglist>
          <tag><c>false</c></tag>
          <item>
            <p>Disables tracing for the matching functions.
              Any match specification is removed.</p>
          </item>
          <tag><c>true</c></tag>
          <item>
            <p>Enables tracing for the matching functions.
              Any match specification is removed.</p>
          </item>
          <tag><c><anno>MatchSpecList</anno></c></tag>
          <item>
            <p>A list of match specifications. An empty list is
              equivalent to <c>true</c>. For a description of match
              specifications, see section <seealso marker="erts:match_spec">
              Match Specifications in Erlang</seealso> in the User's Guide.</p>
          </item>
          <tag><c>restart</c></tag>
          <item>
            <p>For the <c><anno>FlagList</anno></c> options <c>call_count</c>
              and <c>call_time</c>: restarts
              the existing counters. The behavior is undefined
              for other <c><anno>FlagList</anno></c> options.</p>
          </item>
          <tag><c>pause</c></tag>
          <item>
            <p>For the <c><anno>FlagList</anno></c> options
              <c>call_count</c> and <c>call_time</c>: pauses
              the existing counters. The behavior is undefined for
              other <c><anno>FlagList</anno></c> options.</p>
          </item>
        </taglist>
        <p>Parameter <c><anno>FlagList</anno></c> is a list of options.
          The following are the valid options:</p>
        <taglist>
          <tag><c>global</c></tag>
          <item>
            <p>Turns on or off call tracing for global function calls
              (that is, calls specifying the module explicitly). Only
              exported functions match and only global calls
              generate trace messages. <em>This is the default</em>.</p>
          </item>
          <tag><c>local</c></tag>
          <item>
            <p>Turns on or off call tracing for all types of function
              calls. Trace messages are sent whenever any of
              the specified functions are called, regardless of how they
              are called. If flag <c>return_to</c> is set for
              the process, a <c>return_to</c> message is also sent
              when this function returns to its caller.</p>
          </item>
          <tag><c>meta | {meta, <anno>Pid</anno>} |
            {meta, <anno>TracerModule</anno>, <anno>TracerState</anno>}</c>
          </tag>
          <item>
            <p>Turns on or off meta-tracing for all types of function
              calls. Trace messages are sent to the tracer whenever any of
              the specified functions are called. If no tracer is specified,
              <c>self()</c> is used as a default tracer process.</p>
            <p>Meta-tracing traces all processes and does not care
              about the process trace flags set by <c>erlang:trace/3</c>,
              the trace flags are instead fixed to
              <c>[call, timestamp]</c>.</p>
            <p>The match specification function <c>{return_trace}</c>
              works with meta-trace and sends its trace message to the
              same tracer.</p>
          </item>
          <tag><c>call_count</c></tag>
          <item>
            <p>Starts (<c><anno>MatchSpec</anno> == true</c>) or stops
              (<c><anno>MatchSpec</anno> == false</c>)
              call count tracing for all
              types of function calls. For every function, a counter is
              incremented when the function is called, in any process.
              No process trace flags need to be activated.</p>
            <p>If call count tracing is started while already running,
              the count is restarted from zero. To pause running
              counters, use <c><anno>MatchSpec</anno> == pause</c>.
              Paused and running counters can be restarted from zero with
              <c><anno>MatchSpec</anno> == restart</c>.</p>
            <p>To read the counter value, use
              <seealso marker="#trace_info/2">
              <c>erlang:trace_info/2</c></seealso>.</p>
          </item>
          <tag><c>call_time</c></tag>
          <item>
            <p>Starts (<c><anno>MatchSpec</anno> == true</c>) or stops
              (<c><anno>MatchSpec</anno> == false</c>) call time
              tracing for all
              types of function calls. For every function, a counter is
              incremented when the function is called.
              Time spent in the function is accumulated in
              two other counters, seconds and microseconds.
              The counters are stored for each call traced process.</p>
            <p>If call time tracing is started while already running,
              the count and time restart from zero. To pause
              running counters, use <c><anno>MatchSpec</anno> == pause</c>.
              Paused and running counters can be restarted from zero with
              <c><anno>MatchSpec</anno> == restart</c>.</p>
            <p>To read the counter value, use
              <seealso marker="#trace_info/2">
              <c>erlang:trace_info/2</c></seealso>.</p>
          </item>
        </taglist>
        <p>The options <c>global</c> and <c>local</c> are mutually
          exclusive, and <c>global</c> is the default (if no options are
          specified). The options <c>call_count</c> and <c>meta</c>
          perform a kind of local tracing, and cannot be combined
          with <c>global</c>. A function can be globally or
          locally traced. If global tracing is specified for a
          set of functions, then local, meta, call time, and call count
          tracing for the matching set of local functions is
          disabled, and conversely.</p>
        <p>When disabling trace, the option must match the type of trace
          set on the function. That is, local tracing must be
          disabled with option <c>local</c> and global tracing with
          option <c>global</c> (or no option), and so on.</p>
        <p>Part of a match specification list cannot be changed directly.
          If a function has a match specification, it can be replaced
          with a new one. To change an existing match specification,
          use the BIF
          <seealso marker="#trace_info/2"><c>erlang:trace_info/2</c></seealso>
          to retrieve the existing match specification.</p>
        <p>Returns the number of functions matching
          argument <c><anno>MFA</anno></c>. This is zero if none matched.</p>
      </desc>
    </func>

    <func>
      <name name="trunc" arity="1"/>
      <fsummary>Return an integer by truncating a number.</fsummary>
      <desc>
        <p>Returns an integer by truncating <c><anno>Number</anno></c>,
          for example:</p>
        <pre>
> <input>trunc(5.5).</input>
5</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="tuple_size" arity="1"/>
      <fsummary>Return the size of a tuple.</fsummary>
      <desc>
        <p>Returns an integer that is the number of elements in
          <c><anno>Tuple</anno></c>, for example:</p>
        <pre>
> <input>tuple_size({morni, mulle, bwange}).</input>
3</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>

    <func>
      <name name="tuple_to_list" arity="1"/>
      <fsummary>Convert a tuple to a list.</fsummary>
      <desc>
        <p>Returns a list corresponding to <c><anno>Tuple</anno></c>.
          <c><anno>Tuple</anno></c> can contain any Erlang terms.
          Example:</p>
        <pre>
> <input>tuple_to_list({share, {'Ericsson_B', 163}}).</input>
[share,{'Ericsson_B',163}]</pre>
      </desc>
    </func>

    <func>
      <name name="unique_integer" arity="0"/>
      <fsummary>Get a unique integer value.</fsummary>
      <desc>
        <p>Generates and returns an
          <seealso marker="doc/efficiency_guide:advanced#unique_integers">
          integer unique on current runtime system instance</seealso>.
          The same as calling
          <seealso marker="#unique_integer/1">
          <c>erlang:unique_integer([])</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="unique_integer" arity="1"/>
      <fsummary>Get a unique integer value.</fsummary>
      <desc>
        <p>Generates and returns an
          <seealso marker="doc/efficiency_guide:advanced#unique_integers">
          integer unique on current runtime system
          instance</seealso>. The integer is unique in the
          sense that this BIF, using the same set of
          modifiers, does not return the same integer more
          than once on the current runtime system instance.
          Each integer value can of course be constructed
          by other means.</p>
        <p>By default, when <c>[]</c> is passed as
          <c><anno>ModifierList</anno></c>, both negative and
          positive integers can be returned. This
          to use the range of integers that do
          not need heap memory allocation as much as possible.
          By default the returned integers are also only
          guaranteed to be unique, that is, any returned integer
          can be smaller or larger than previously
          returned integers.</p>
        <p><c><anno>Modifier</anno></c>s:</p>
        <taglist>
          <tag>positive</tag>
          <item>
            <p>Returns only positive integers.</p>
            <p>Notice that by passing the <c>positive</c> modifier
              you will get heap allocated integers (bignums) quicker.</p>
          </item>
          <tag>monotonic</tag>
          <item>
            <p>Returns <seealso
              marker="time_correction#Strictly_Monotonically_Increasing">
              strictly monotonically increasing</seealso> integers
              corresponding to creation time. That is, the integer
              returned is always larger than previously
              returned integers on the current runtime system
              instance.</p>
            <p>These values can be used to determine order between events
              on the runtime system instance. That is, if both
              <c>X = erlang:unique_integer([monotonic])</c> and
              <c>Y = erlang:unique_integer([monotonic])</c> are
              executed by different processes (or the same
              process) on the same runtime system instance and
              <c>X &lt; Y</c>, we know that <c>X</c> was created
              before <c>Y</c>.</p>
            <warning>
              <p>Strictly monotonically increasing values
                are inherently quite expensive to generate and scales
                poorly. This is because the values need to be synchronized
                between CPU cores. That is, do not pass the <c>monotonic</c>
                modifier unless you really need strictly monotonically
                increasing values.</p>
            </warning>
        </item>
        </taglist>
        <p>All valid <c><anno>Modifier</anno></c>s
          can be combined. Repeated (valid)
          <c><anno>Modifier</anno></c>s in the <c>ModifierList</c>
          are ignored.</p>
        <note>
          <p>The set of integers returned by
            <c>erlang:unique_integer/1</c> using different sets of
            <c><anno>Modifier</anno></c>s <em>will overlap</em>.
            For example, by calling <c>unique_integer([monotonic])</c>,
            and <c>unique_integer([positive, monotonic])</c>
            repeatedly, you will eventually see some integers that are
            returned by both calls.</p>
        </note>
        <p>Failures:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>if <c><anno>ModifierList</anno></c> is not a
            proper list.</item>
          <tag><c>badarg</c></tag>
          <item>if <c><anno>Modifier</anno></c> is not a
            valid modifier.</item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="universaltime" arity="0"/>
      <fsummary>Current date and time according to Universal Time Coordinated
        (UTC).</fsummary>
      <desc>
        <p>Returns the current date and time according to Universal
          Time Coordinated (UTC) in the form
          <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c> if
          supported by the underlying OS.
          Otherwise <c>erlang:universaltime()</c> is equivalent to
          <c>erlang:localtime()</c>. Example:</p>
        <pre>
> <input>erlang:universaltime().</input>
{{1996,11,6},{14,18,43}}</pre>
      </desc>
    </func>

    <func>
      <name name="universaltime_to_localtime" arity="1"/>
      <fsummary>Convert from Universal Time Coordinated (UTC) to local date
        and time.</fsummary>
      <desc>
        <p>Converts Universal Time Coordinated (UTC) date and time to
          local date and time in the form
          <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c> if
          supported by the underlying OS.
          Otherwise no conversion is done, and
          <c><anno>Universaltime</anno></c> is returned. Example:</p>
        <pre>
> <input>erlang:universaltime_to_localtime({{1996,11,6},{14,18,43}}).</input>
{{1996,11,7},{15,18,43}}</pre>
        <p>Failure: <c>badarg</c> if <c>Universaltime</c> denotes
          an invalid date and time.</p>
      </desc>
    </func>

    <func>
      <name name="unlink" arity="1"/>
      <fsummary>Remove a link to another process or port.</fsummary>
      <desc>
        <p>Removes the link, if there is one, between the calling
          process and the process or port referred to by
          <c><anno>Id</anno></c>.</p>
        <p>Returns <c>true</c> and does not fail, even if there is no
          link to <c><anno>Id</anno></c>, or if <c><anno>Id</anno></c>
          does not exist.</p>
        <p>Once <c>unlink(<anno>Id</anno>)</c> has returned,
          it is guaranteed that
          the link between the caller and the entity referred to by
          <c><anno>Id</anno></c> has no effect on the caller
          in the future (unless
          the link is setup again). If the caller is trapping exits, an
          <c>{'EXIT', <anno>Id</anno>, _}</c> message from the link
          can have been placed in the caller's message queue before
          the call.</p>
        <p>Notice that the <c>{'EXIT', <anno>Id</anno>, _}</c>
          message can be the
          result of the link, but can also be the result of <c>Id</c>
          calling <c>exit/2</c>. Therefore, it <em>can</em> be
          appropriate to clean up the message queue when trapping exits
          after the call to <c>unlink(<anno>Id</anno>)</c>, as follows:</p>
        <code type="none">
unlink(Id),
receive
    {'EXIT', Id, _} ->
        true
after 0 ->
        true
end</code>
        <note>
          <p>Before Erlang/OTP R11B (ERTS 5.5) <c>unlink/1</c>
            behaved completely asynchronously, that is, the link was active
            until the "unlink signal" reached the linked entity. This
            had an undesirable effect, as you could never know when
            you were guaranteed <em>not</em> to be effected by the link.</p>
          <p>The current behavior can be viewed as two combined operations:
            asynchronously send an "unlink signal" to the linked entity
            and ignore any future results of the link.</p>
        </note>
      </desc>
    </func>

    <func>
      <name name="unregister" arity="1"/>
      <fsummary>Remove the registered name for a process (or port).</fsummary>
      <desc>
        <p>Removes the registered name <c><anno>RegName</anno></c>
          associated with a
          process identifier or a port identifier, for example:</p>
        <pre>
> <input>unregister(db).</input>
true</pre>
        <p>Users are advised not to unregister system processes.</p>
        <p>Failure: <c>badarg</c> if <c>RegName</c> is not a registered
          name.</p>
      </desc>
    </func>

    <func>
      <name name="whereis" arity="1"/>
      <fsummary>Get the pid (or port) with a specified registered name.
      </fsummary>
      <desc>
        <p>Returns the process identifier or port identifier with
          the registered name <c>RegName</c>. Returns <c>undefined</c>
          if the name is not registered. Example:</p>
        <pre>
> <input>whereis(db).</input>
&lt;0.43.0></pre>
      </desc>
    </func>

    <func>
      <name name="yield" arity="0"/>
      <fsummary>Let other processes get a chance to execute.</fsummary>
      <desc>
        <p>Voluntarily lets other processes (if any) get a chance to
          execute. Using this function is similar to
          <c>receive after 1 -> ok end</c>, except that <c>yield()</c>
          is faster.</p>
        <warning>
          <p>There is seldom or never any need to use this BIF
            as other processes have a chance to run in another scheduler
            thread anyway.
            Using this BIF without a thorough grasp of how the scheduler
            works can cause performance degradation.</p>
        </warning>
      </desc>
    </func>
  </funcs>
</erlref>