aboutsummaryrefslogtreecommitdiffstats
path: root/erts/doc/src/erlang.xml
blob: 81e9084e07f9d480bc9e52d5640827db4f9cf96f (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
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1996</year><year>2013</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.

      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights 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 seen as being
      in the module <c>erlang</c>. A number 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 and both the calls <c>atom_to_list(Erlang)</c> and
      <c>erlang:atom_to_list(Erlang)</c> are identical.</p>
    <p>In the text, auto-imported BIFs are listed without module prefix.
      BIFs listed with module prefix are not auto-imported.</p>
    <p>BIFs may fail for a variety of reasons. All BIFs fail with
      reason <c>badarg</c> if they are called with arguments of an
      incorrect type. The other reasons that may make BIFs fail are
      described in connection with the description of each individual
      BIF.</p>
    <p>Some BIFs may be used in guard tests, these are marked with
      "Allowed in guard tests".</p>
  </description>

  <datatypes>
    <datatype>
      <name><marker id="type-ext_binary">ext_binary()</marker></name>
      <desc>
        <p>A binary data object, structured according to
           the Erlang external term format.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="timestamp"></name>
      <desc><p>See <seealso marker="#now/0">now/0</seealso>.</p>
      </desc>
    </datatype>
  </datatypes>

  <funcs>
    <func>
      <name name="abs" arity="1" clause_i="1"/>
      <name name="abs" arity="1" clause_i="2"/>
      <type variable="Float" name_i="1"/>
      <type variable="Int" name_i="2"/>
      <fsummary>Arithmetical absolute value</fsummary>
      <desc>
        <p>Returns an integer or float which is the arithmetical
          absolute value of <c><anno>Float</anno></c> or <c><anno>Int</anno></c>.</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>Continue 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>- would assign the same value to <c>Y</c> as this would:</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>- would assign the same value to <c>Z</c> as this would:</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 which 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.</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>Call a fun, passing the elements in <c><anno>Args</anno></c> as
          arguments.</p>
        <p>Note: 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 given as
            <c>{Module, Function}</c>, equivalent to
            <c>apply(Module, Function, Args)</c>. This usage is
            deprecated and will stop working in a future release of
            Erlang/OTP.</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>.</p>
        <pre>
> <input>apply(lists, reverse, [[a, b, c]]).</input>
[c,b,a]</pre>
        <p><c>apply</c> can be used to evaluate BIFs by using
          the module name <c>erlang</c>.</p>
        <pre>
> <input>apply(erlang, atom_to_list, ['Erlang']).</input>
"Erlang"</pre>
        <p>Note: 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: <c>error_handler:undefined_function/3</c> is called
          if the applied function is not exported. The error handler
          can be redefined (see
          <seealso marker="#process_flag/2">process_flag/2</seealso>).
          If the <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 the 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 which corresponds to the text
          representation of <c><anno>Atom</anno></c>. If <c><anno>Encoding</anno></c>
	  is <c>latin1</c>, there will be one byte for each character
	  in the text representation. If <c><anno>Encoding</anno></c> is 
	  <c>utf8</c> or
	  <c>unicode</c>, the characters will be encoded using UTF-8
	  (meaning that characters from 16#80 up to 0xFF will be
	  encoded in two bytes).</p>

	<note><p>Currently, <c>atom_to_binary(<anno>Atom</anno>, latin1)</c> can
	never fail because the text representation of an atom can only contain
	characters from 0 to 16#FF. In a future release, the text representation
	of atoms might be allowed to contain any Unicode character
	and <c>atom_to_binary(<anno>Atom</anno>, latin1)</c> will fail if the
	text representation for the <c><anno>Atom</anno></c> contains a Unicode
	character greater than 16#FF.</p></note>

        <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 which corresponds to the text
          representation of <c><anno>Atom</anno></c>.</p>
        <pre>
> <input>atom_to_list('Erlang').</input>
"Erlang"</pre>
      </desc>
    </func>
    <func>
      <name name="binary_part" arity="2"/>
      <fsummary>Extracts 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:</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>If <c><anno>PosLen</anno></c> in any way references outside the binary, a <c>badarg</c> exception is raised.</p>

      <p><c><anno>Start</anno></c> is zero-based, i.e.:</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>See the STDLIB module <c>binary</c> for details about the <c><anno>PosLen</anno></c> semantics.</p>

      <p>Allowed in guard tests.</p>
      </desc>
    </func>
    <func>
      <name name="binary_part" arity="3"/>
      <fsummary>Extracts 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; furthermore, only Unicode characters up
	to 0xFF are allowed.</p>

	<note><p><c>binary_to_atom(<anno>Binary</anno>, utf8)</c> will fail if
	the binary contains Unicode characters greater than 16#FF.
	In a future release, such Unicode characters might be allowed
	and <c>binary_to_atom(<anno>Binary</anno>, utf8)</c>
	will not fail in that case. For more information on Unicode support in atoms
	see <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8 encoded atoms</seealso>
	in the chapter about the external term format in the ERTS User's Guide.</p></note>

        <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>
** exception error: bad argument
     in function  binary_to_atom/2
        called as binary_to_atom(&lt;&lt;208,128&gt;&gt;,utf8)</pre>
      </desc>
    </func>
    <func>
      <name name="binary_to_existing_atom" arity="2"/>
      <fsummary>Convert from text representation to an atom</fsummary>
      <desc>
        <p>Works like <seealso marker="#binary_to_atom/2">binary_to_atom/2</seealso>,
          but the atom must already exist.</p>
        <p>Failure: <c>badarg</c> if the atom does not already exist.</p>
      </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>.</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>.</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>.</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 which correspond 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(<anno>Binary</anno>)</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>. Positions in the
          binary are numbered starting from 1.</p>

	  <note><p>This function's indexing style of using one-based indices for
	  binaries is deprecated. New code should use the functions in
	  the STDLIB module <c>binary</c> instead. They consequently
	  use the same (zero-based) style of indexing.</p></note>
      </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 which correspond 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 will be a bitstring
	  containing the remaining bits (1 up to 7 bits).</p>
      </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 which is the result of decoding
          the binary object <c><anno>Binary</anno></c>, which must be encoded
          according to the Erlang external term format.</p>
        <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">term_to_binary/1</seealso>
           and
	   <seealso marker="#binary_to_term/2">binary_to_term/2</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 options that affect decoding
           of the binary.</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 may be used to
	       attack the Erlang system.  In the event of receiving unsafe
               data, decoding fails with a badarg error.</p>
	    <p>Currently, this prevents creation of new atoms directly,
	       creation of new atoms indirectly (as they are embedded in
	       certain structures like pids, refs, funs, etc.), and creation of
	       new external function references.  None of those resources are
	       currently garbage collected, so unchecked creation of them can
               exhaust available memory.</p>
          </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">term_to_binary/1</seealso>,
           <seealso marker="#binary_to_term/1">binary_to_term/1</seealso>,
           and <seealso marker="#list_to_existing_atom/1">
             list_to_existing_atom/1</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="bit_size" arity="1"/>
      <fsummary>Return the size of a bitstring</fsummary>
      <desc>
        <p>Returns an integer which is the size in bits of <c><anno>Bitstring</anno></c>.</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="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, and a context switch is
          forced when the counter reaches the maximum number of reductions
	  for a process (2000 reductions in R12B).</p>
        <warning>
          <p>This BIF might 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 which 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 will be rounded <em>up</em>.)</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, where <c><anno>TimerRef</anno></c> was returned by
          either
          <seealso marker="#send_after/3">erlang:send_after/3</seealso>
          or
          <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>.
          If the timer is there to be removed, the function returns
          the time in milliseconds left until the timer would have expired,
          otherwise <c>false</c> (which means that <c><anno>TimerRef</anno></c> was
          never a timer, that it has already been cancelled, or that it
          has already delivered its message).</p>
        <p>See also 
          <seealso marker="#send_after/3">erlang:send_after/3</seealso>,
          <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>,
          and
          <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p>
        <p>Note: Cancelling a timer does not guarantee that the message
          has not already been delivered to the message queue.</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 the <c><anno>Module</anno></c> has old code,
	and <c>false</c> otherwise.</p>
        <p>See also <seealso marker="kernel:code">code(3)</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="check_process_code" arity="2"/>
      <fsummary>Check if a process is executing old code for a module</fsummary>
      <desc>
        <p>Returns <c>true</c> if the process <c><anno>Pid</anno></c> is executing
          old code for <c><anno>Module</anno></c>. That is, if the current call of
          the process executes old code for this module, or if the
          process has references to old code for this module, or if the
          process contains funs that references old code for this
          module. Otherwise, it returns <c>false</c>.</p>
        <pre>
> <input>check_process_code(Pid, lists).</input>
false</pre>
        <p>See also <seealso marker="kernel:code">code(3)</seealso>.</p>
      </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>Continue 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>- would assign the same value to <c>Y</c> as this would:</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>- would assign the same value to <c>Z</c> as this would:</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.</p>
        <pre>
> <input>date().</input>
{1995,2,19}</pre>
      </desc>
    </func>
    <func>
      <name name="decode_packet" arity="3"/>
      <fsummary>Extracts 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>. Very similar to the packet
        handling done by sockets with the option {packet,<anno>Type</anno>}.</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 not known. <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>The following values of <c><anno>Type</anno></c> are valid:</p>
        <taglist>
          <tag><c>raw | 0</c></tag>
          <item>
            <p>No packet handling is done. 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 header can be one, two, or four bytes;
              the order of the bytes is big-endian. The header
              will be stripped off when the packet is returned.</p>
          </item>
          <tag><c>line</c></tag>
          <item>
            <p>A packet is a line terminated with newline. The
              newline character is included in the returned packet
              unless the line was truncated according to the 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 above. 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
	       (like <c>"Sec-Websocket-Key"</c>).</p>
            <p>The protocol type <c>http</c> should only be used for
               the first line when a <c><anno>HttpRequest</anno></c> or a
               <c><anno>HttpResponse</anno></c> is expected. The following calls
               should use <c>httph</c> to get <c><anno>HttpHeader</anno></c>'s until
               <c>http_eoh</c> is returned that 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> will return
               strings (<c>HttpString</c>) as binaries instead of lists.</p>
          </item>
        </taglist>
        <p>The following options are available:</p>
            <taglist>
              <tag><c>{packet_size, integer() >= 0}</c></tag>
              <item><p>Sets the max allowed size of the packet body. If
                the packet header indicates that the length of the
                packet is longer than the max allowed length, the packet
                is considered invalid. Default is 0 which means no
                size limit.</p>
              </item>
              <tag><c>{line_length, integer() >= 0}</c></tag>
              <item><p>For packet type <c>line</c>, truncate lines longer
	      than the indicated length.</p>
	      <p>Option <c>line_length</c> also applies to <c>http*</c> 
	      packet types as an alias for option <c>packet_size</c> in the
	      case when <c>packet_size</c> itself is not set. This usage is
	      only intended for backward compatibility.</p>
              </item>
            </taglist>
        <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>.
		  </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">code(3)</seealso>) and should not be
            used elsewhere.</p>
        </warning>
        <p>Failure: <c>badarg</c> if there is already 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 which the calling process
          obtained by calling
          <seealso marker="#monitor/2">monitor/2</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
          due to the monitor will be placed in the caller's message queue
          in the future. A <c>{'DOWN', <anno>MonitorRef</anno>, _, _, _}</c> message
          might have been placed in the caller's message queue prior to
          the call, though. Therefore, in most cases, it is advisable
          to remove such a <c>'DOWN'</c> message from the message queue
          after monitoring has been stopped. 
          <seealso marker="#demonitor/2">demonitor(<anno>MonitorRef</anno>, [flush])</seealso> can be used instead of
          <c>demonitor(<anno>MonitorRef</anno>)</c> if this cleanup is wanted.</p>
        <note>
          <p>Prior to OTP release R11B (erts version 5.5) <c>demonitor/1</c>
            behaved completely asynchronous, i.e., the monitor was active
            until the "demonitor signal" reached the monitored entity. This
            had one undesirable effect, though. You could never know when
            you were guaranteed <em>not</em> to receive a <c>DOWN</c> message
            due to the monitor.</p>
          <p>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">demonitor(<anno>MonitorRef</anno>)</seealso>.</p>
        <p>Currently the following <c><anno>Option</anno></c>s are valid:</p>
        <taglist>
          <tag><c>flush</c></tag>
          <item>
            <p>Remove (one) <c>{_, <anno>MonitorRef</anno>, _, _, _}</c> message,
              if there is one, from the caller's 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 due to this monitor have
		       been nor will be placed in the message queue
		       of the caller.
		    </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's message queue.
		    </p>
	      </item>
	    </taglist>
	    <p>If the <c>info</c> option is combined with the <c>flush</c>
	       option, <c>false</c> will be returned if a flush was needed;
	       otherwise, <c>true</c>.
	    </p>
          </item>
        </taglist>
        <note>
          <p>More options may be added in the future.</p>
        </note>
        <p>Failure: <c>badarg</c> if <c><anno>OptionList</anno></c> is not a list, or
          if <c><anno>Option</anno></c> is not a valid option, or the same failure as for
          <seealso marker="#demonitor/1">demonitor/1</seealso></p>
      </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 will appear 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. Returns <c>true</c> if disconnection succeeds,
          otherwise <c>false</c>. If the local node is not alive,
          the function returns <c>ignored</c>.</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="element" arity="2"/>
      <type_desc variable="N">1..tuple_size(<anno>Tuple</anno>)</type_desc>
      <fsummary>Get Nth element of a tuple</fsummary>
      <desc>
        <p>Returns the <c><anno>N</anno></c>th element (numbering from 1) of
          <c><anno>Tuple</anno></c>.</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.</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>.</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 given 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 actual
          exit reason will be <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c>
          is a list of the functions most recently called (the current
          function first). Since evaluating this function causes
          the process to terminate, it has no return value.</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 given 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 actual
          exit reason will be <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 will be used
          to provide the actual arguments for the current function in
          the <c>Where</c> term. Since 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 given reason</fsummary>
      <desc>
        <p>Stops the execution of the calling process with the exit
          reason <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> is any term. Since
          evaluating this function causes the process to terminate, it
          has no return value.</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 apply if <c><anno>Reason</anno></c> is any term
          except <c>normal</c> or <c>kill</c>:</p>
        <p>If <c><anno>Pid</anno></c> is not trapping exits, <c><anno>Pid</anno></c> itself will
          exit with exit reason <c><anno>Reason</anno></c>. 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>. <c>From</c> is the pid of the process
          which sent the exit signal. See also
          <seealso marker="#process_flag/2">process_flag/2</seealso>.</p>
        <p>If <c><anno>Reason</anno></c> is the atom <c>normal</c>, <c><anno>Pid</anno></c> will
          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 will unconditionally exit 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>
        <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>
        <p>This is equivalent to a call to: <code>erlang:external_size(<anno>Term</anno>, [])
          </code></p>
      </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>
        <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>
        <p>The option <c>{minor_version, <anno>Version</anno>}</c> specifies how floats
          are encoded. See
          <seealso marker="#term_to_binary/2">term_to_binary/2</seealso> for
          a more detailed description.
        </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.</p>
        <pre>
> <input>float(55).</input>
55.0</pre>
        <p>Allowed in guard tests.</p>
        <note>
          <p>Note that if used on the top-level in a guard, it will
            test whether the argument is a floating point number; for
            clarity, use
            <seealso marker="#is_float/1">is_float/1</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 above.</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 given options</fsummary>
      <desc>
        <p>Returns a binary which corresponds to the text
          representation of <c><anno>Float</anno></c> using fixed decimal 
	  point formatting. The <c><anno>Options</anno></c> behave in the same
	  way as <seealso marker="#float_to_list/2">float_to_list/2</seealso>.
	</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 given options</fsummary>
      <desc>
        <p>Returns a string which corresponds to the text
          representation of <c>Float</c> using fixed decimal point formatting.
          When <c>decimals</c> option is specified
          the returned value will contain at most <c>Decimals</c> number of
          digits past the decimal point.  If the number doesn't fit in the
          internal static buffer of 256 bytes, the function throws <c>badarg</c>.
          When <c>compact</c> option is provided
          the trailing zeros at the end of the list are truncated (this option is
          only meaningful together with the <c>decimals</c> option). When
          <c>scientific</c> option is provided, the float will be formatted using
          scientific notation with <c>Decimals</c> digits of precision. If
          <c>Options</c> is <c>[]</c> the function behaves like 
	  <c><seealso marker="#float_to_list/1">float_to_list/1</seealso></c>.
          </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="fun_info" arity="1"/>
      <fsummary>Information about a fun</fsummary>
      <desc>
        <p>Returns a list containing information about the fun
          <c><anno>Fun</anno></c>. Each element of the list is a tuple. The order of
          the tuples is not defined, and more tuples may be added in a
          future release.</p>
        <warning>
          <p>This BIF is mainly intended for debugging, but it can
            occasionally be useful in library functions that might need
            to verify, for instance, the arity of a fun.</p>
        </warning>
        <p>There are two types of funs with slightly different
          semantics:</p>
        <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>. Note that module <c>M</c> does not even need
          to be loaded when the fun <c>fun M:F/A</c> is created.</p>
        <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
          will be called (even if newer version of the module has been
          loaded).</p>
        <p>The following elements will always be present in the list
          for both local and external funs:</p>
        <taglist>
          <tag><c>{type, Type}</c></tag>
          <item>
            <p><c>Type</c> is either <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 generally
              only of informational use. As it is a local function, it
              is not possible to call it directly.)
              If no code is currently loaded for the fun, <c>[]</c>
              will be 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
              should 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 will only be 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 pid 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's
              fun table.</p>
          </item>
          <tag><c>{new_index, Index}</c></tag>
          <item>
            <p><c>Index</c> (an integer) is an index into the module's
              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.
	    Starting in the R15 release, this integer is calculated from
	    the compiled code for the entire module. Before R15, this
	    integer was based on only the body of the fun.
	    </p>
          </item>
        </taglist>
      </desc>
    </func>
    <func>
      <name name="fun_info" arity="2"/>
      <type name="fun_info_item"/>
      <fsummary>Information about a fun</fsummary>
      <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">erlang:fun_info/1</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="fun_to_list" arity="1"/>
      <fsummary>Text representation of a fun</fsummary>
      <desc>
        <p>Returns a string which corresponds 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>;
          otherwise <c>false</c>.</p>
        <p>Returns <c>false</c> for any BIF (functions implemented in C
          rather than in Erlang).</p>
      </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 currently
          executing process. The function should not 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. Improper use may seriously degrade system
          performance.</p>
        <p>Compatibility note: In versions of OTP prior to R7,
          the garbage collection took place at the next context switch,
          not immediately. To force a context switch after a call to
          <c>erlang:garbage_collect()</c>, it was sufficient to make
          any function call.</p>
      </desc>
    </func>
    <func>
      <name name="garbage_collect" arity="1"/>
      <fsummary>Force an immediate garbage collection of a process</fsummary>
      <desc>
        <p>Works like <c>erlang:garbage_collect()</c> but on any
          process. The same caveats apply. Returns <c>false</c> if
          <c><anno>Pid</anno></c> refers to a dead process; <c>true</c> otherwise.</p>
      </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.</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.</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="1"/>
      <fsummary>Return a list of keys from the process dictionary</fsummary>
      <desc>
        <p>Returns a list of keys which are associated with the value
          <c><anno>Val</anno></c> in the process dictionary.</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>Get the call stack back-trace (<em>stacktrace</em>) of the last
          exception in the calling process as a list of 
          <c>{<anno>Module</anno>,<anno>Function</anno>,<anno>Arity</anno>,<anno>Location</anno>}</c> tuples.
          The <c><anno>Arity</anno></c> field in the first tuple may 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 may also be reset to [].</p>
        <p>The stacktrace is the same data as the <c>catch</c> operator
          returns, for example:</p>
        <p><c>{'EXIT',{badarg,Stacktrace}} = catch abs(x)</c></p>
	<p><c><anno>Location</anno></c> is a (possibly empty) list of two-tuples that
	  may indicate the location in the source code of the function.
	  The first element is an atom that describes the type of
	  information in the second element. Currently the following
	  items may occur:</p>
	<taglist>
	  <tag><c>file</c></tag>
	  <item>
	    <p>The second element of the tuple is a string (list of
	      characters) representing the filename of the source file
	      of the function.</p>
	  </item>
	  <tag><c>line</c></tag>
	  <item>
	    <p>The second element of the tuple is the line number
	      (an integer greater than zero) in the source file
	      where the exception occurred or the function was called.</p>
	  </item>
	</taglist>
        <p>See also
          <seealso marker="#error/1">erlang:error/1</seealso> and
          <seealso marker="#error/2">erlang:error/2</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 pid of the group leader for the process which
          evaluates the function.</p>
        <p>Every process is a member of some process group and all
          groups have a <em>group leader</em>. All IO 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 start-up, <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 processes started from a
          certain shell should have another group leader than
          <c>init</c>.</p>
        <p>See also
          <seealso marker="#group_leader/0">group_leader/0</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>.</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>.</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>:
	</p>
	<taglist>
	  <tag>integer()</tag>
	  <item>The runtime system exits with the integer value <c><anno>Status</anno></c>
	  as status code to the calling environment (operating system).
	  </item>
	  <tag>string()</tag>
	  <item>An erlang crash dump is produced with <c><anno>Status</anno></c> as slogan,
	  and then the runtime system exits with status code <c>1</c>.
	  </item>
	  <tag><c>abort</c></tag>
	  <item>
	    The runtime system aborts producing a core dump, if that is
	    enabled in the operating system.
	  </item>
	</taglist>
	<p>Note that on many platforms, only the status codes 0-255 are
	  supported by the operating system.
	</p>
	<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> the <c>flush</c>
	  option is ignored and flushing is <em>not</em> done.
	</p>
      </desc>
    </func>
    <func>
      <name name="hash" arity="2"/>
      <fsummary>Hash function (deprecated)</fsummary>
      <desc>
        <p>Returns a hash value for <c><anno>Term</anno></c> within the range
          <c>1..<anno>Range</anno></c>. The allowed range is 1..2^27-1.</p>
        <warning>
          <p>This BIF is deprecated as the hash value may differ on
            different architectures. Also the hash values for integer
            terms larger than 2^27 as well as large binaries are very
            poor. The BIF is retained for backward compatibility
            reasons (it may have been used to hash records into a file),
            but all new code should use one of the BIFs
            <c>erlang:phash/2</c> or <c>erlang:phash2/1,2</c> instead.</p>
        </warning>
      </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.</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 [].</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, which is
          useful if the process does not expect to receive any messages
          in the near future.</p>
        <p>The process will be awaken when a message is sent to it, and
          control will resume in <c><anno>Module</anno>:<anno>Function</anno></c> with
          the arguments given by <c><anno>Args</anno></c> with the call stack
          emptied, meaning that the process will terminate when that
          function returns. Thus <c>erlang:hibernate/3</c> will never
          return to its caller.</p>
        <p>If the process has any message in its message queue,
          the process will be awaken immediately in the same way as
          described above.</p>
        <p>In more technical terms, what <c>erlang:hibernate/3</c> does
          is the following. It discards the call stack for the process.
          Then it garbage collects the process. After the garbage
          collection, all live data is in one continuous heap. The heap
          is then shrunken to the exact same size as the live data
          which 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 has been awaken will ensure that the heap
          size is changed to a size not smaller than the minimum heap
          size.</p>
        <p>Note that emptying the call stack means that any surrounding
          <c>catch</c> is removed and has to 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), should use
          <seealso marker="stdlib:proc_lib#hibernate/3">proc_lib:hibernate/3</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> insert 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 subsequently
			  pushed one step higher in the new tuple <c><anno>Tuple2</anno></c>.
		  </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 which corresponds to the text
          representation of <c><anno>Integer</anno></c>.</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 which corresponds to the text
          representation of <c><anno>Integer</anno></c> in base <c><anno>Base</anno></c>.</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 which corresponds to the text
          representation of <c><anno>Integer</anno></c>.</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 which corresponds to the text
          representation of <c><anno>Integer</anno></c> in base <c><anno>Base</anno></c>.</p>
        <pre>
> <input>integer_to_list(1023, 16).</input>
"3FF"</pre>
      </desc>
    </func>
    <func>
      <name name="iolist_to_binary" arity="1"/>
      <fsummary>Convert an iolist to a binary</fsummary>
      <desc>
        <p>Returns a binary which is made from the integers and
          binaries in <c><anno>IoListOrBinary</anno></c>.</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_size" arity="1"/>
      <fsummary>Size of an iolist</fsummary>
      <desc>
        <p>Returns an integer which is the size in bytes
          of the binary that would be the result of 
          <c>iolist_to_binary(<anno>Item</anno>)</c>.</p>
        <pre>
> <input>iolist_size([1,2|&lt;&lt;3,4>>]).</input>
4</pre>
      </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, it
          returns <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 returns <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 returns <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 returns <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
          either the atom <c>true</c> or the atom <c>false</c>
          (i.e. 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>Returns <c>true</c> if <c><anno>Module</anno>:<anno>Function</anno>/<anno>Arity</anno></c> is
          a BIF implemented in C; otherwise returns <c>false</c>.
          This BIF is useful for builders of cross reference tools.</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 returns <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
          returns <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 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
          returns <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 returns <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 returns <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 either 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 pid</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a pid (process
          identifier); otherwise returns <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 returns <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.
          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>
            specially. 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 the <c><anno>RecordTag</anno></c> is
            not a literal atom, the <c>is_record/2</c> BIF will be
            called instead and the size of the tuple will not be
            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. 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, provided that <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. In most cases
            <c>is_record/2</c> should 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 returns <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 returns <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>.</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">process_flag/2</seealso>):</p>
        <list type="bulleted">
          <item>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>.</item>
          <item>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.</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><c><anno>String</anno></c> may only contain ISO-latin-1
	characters (i.e. numbers below 256) as the current
	implementation does not allow unicode characters >= 256 in
	atoms. For more information on Unicode support in atoms
	see <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8 encoded atoms</seealso>
	in the chapter about the external term format in the ERTS User's Guide.</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 which is made from the integers and
          binaries in <c><anno>IoList</anno></c>.</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"/>
      <type name="bitstring_list"/>
      <fsummary>Convert a list to a bitstring</fsummary>
      <desc>
        <p>Returns a bitstring which 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.)</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&gt;&gt;
> <input>list_to_bitstring([Bin1,1,[2,3,Bin2],4|Bin3]).</input>
&lt;&lt;1,2,3,1,2,3,4,5,4,6,7:46&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>
      </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>.</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>.</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>.</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 pid whose text representation is <c><anno>String</anno></c>.</p>
        <warning>
          <p>This BIF is intended for debugging and for use in
            the Erlang operating system. It should not be used in
            application programs.</p>
        </warning>
        <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 pid.</p>
      </desc>
    </func>
    <func>
      <name name="list_to_tuple" arity="1"/>
      <fsummary>Convert a list to a tuple</fsummary>
      <desc>
        <p>Returns a tuple which corresponds to <c><anno>List</anno></c>. <c><anno>List</anno></c>
          can contain any Erlang terms.</p>
        <pre>
> <input>list_to_tuple([share, ['Ericsson_B', 163]]).</input>
{share, ['Ericsson_B', 163]}</pre>
      </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 the module
          <c><anno>Module</anno></c>, this BIF loads that object code. Also, if
          the code for the 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 may still be processes which are
          executing that code. It 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>
            <p>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>.</p>
          </item>
          <tag><c>not_purged</c></tag>
          <item>
            <p><c><anno>Binary</anno></c> contains a module which cannot be loaded
              because old code for this module already exists.</p>
          </item>
        </taglist>
        <warning>
          <p>This BIF is intended for the code server (see
            <seealso marker="kernel:code">code(3)</seealso>) and should not be
            used elsewhere.</p>
        </warning>
      </desc>
    </func>
    <func>
      <name name="load_nif" arity="2"/>
      <fsummary>Load NIF library</fsummary>
      <desc>
        <note>
          <p>In releases older than OTP R14B, NIFs were an
          experimental feature. Versions of OTP older than R14B might
          have different and possibly incompatible NIF semantics and
          interfaces. For example, in R13B03 the return value on
          failure was
          <c>{error,Reason,Text}</c>.</p>
        </note>
        <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 sharable object/dynamic library file minus
        the OS-dependent file extension (.so for Unix and .dll for
        Windows). See <seealso marker="erl_nif">erl_nif</seealso>
        on how to implement a NIF library.</p> 
        <p><c><anno>LoadInfo</anno></c> can be any term. It will be 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.</p>
        <p>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 atoms below,
        while <c><anno>Text</anno></c> is a human readable string that may give
        some more information about the failure.</p>
        <taglist>
          <tag><c>load_failed</c></tag>
          <item>
            <p>The OS failed to load the NIF library.</p>
          </item>
          <tag><c>bad_lib</c></tag>
          <item>
            <p>The library did not fulfil the requirements as a NIF
            library of the calling module.</p> 
          </item>
          <tag><c>load | reload | upgrade</c></tag>
          <item>
            <p>The corresponding library callback was not successful.</p>
          </item>
          <tag><c>old_code</c></tag>
          <item>
            <p>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.</p>
          </item>
        </taglist>
      </desc>
    </func>
    <func>
      <name name="loaded" arity="0"/>
      <fsummary>List of all loaded modules</fsummary>
      <desc>
        <p>Returns a list of all loaded Erlang modules (current and/or
          old code), including preloaded modules.</p>
        <p>See also <seealso marker="kernel:code">code(3)</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>.</p>
        <p>The time zone and daylight saving time correction depend
          on the underlying OS.</p>
        <pre>
> <input>erlang:localtime().</input>
{{1996,11,6},{14,45,17}}</pre>
      </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 this is supported by the underlying OS. Otherwise,
          no conversion is done and <c><anno>Localtime</anno></c> is returned.</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> does not denote
          a valid 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) just like <c>erlang:localtime_to_universaltime/1</c>,
          but the caller decides if daylight saving time is active or
          not.</p>
        <p>If <c><anno>IsDst</anno> == true</c> the <c><anno>Localtime</anno></c> is during
          daylight saving time, if <c><anno>IsDst</anno> == false</c> it is not,
          and if <c><anno>IsDst</anno> == undefined</c> the underlying OS may
          guess, which is the same as calling
          <c>erlang:localtime_to_universaltime(<anno>Localtime</anno>)</c>.</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> does not denote
          a valid date and time.</p>
      </desc>
    </func>
    <func>
      <name name="make_ref" arity="0"/>
      <fsummary>Return an almost unique reference</fsummary>
      <desc>
        <p>Returns an almost unique reference.</p>
        <p>The returned reference will re-occur after approximately 2^82
          calls; therefore it is unique enough for practical purposes.</p>
        <pre>
> <input>make_ref().</input>
#Ref&lt;0.0.0.135></pre>
      </desc>
    </func>
    <func>
      <name name="make_tuple" arity="2"/>
      <fsummary>Create a new tuple of a given arity</fsummary>
      <desc>
        <p>Returns a new tuple of the given <c><anno>Arity</anno></c>, where all
          elements are <c><anno>InitialValue</anno></c>.</p>
        <pre>
> <input>erlang:make_tuple(4, []).</input>
{[],[],[],[]}</pre>
      </desc>
    </func>
    <func>
      <name name="make_tuple" arity="3"/>
      <fsummary>Create a new tuple with given arity and contents</fsummary>
      <desc>
        <p><c>erlang:make_tuple</c> first creates a tuple of size <c><anno>Arity</anno></c>
	  where each element has the value <c><anno>DefaultValue</anno></c>. It 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
	  last occurrence will be used.</p>
        <pre>
> <input>erlang:make_tuple(5, [], [{2,ignored},{5,zz},{2,aa}]).</input>
{{[],aa,[],[],zz}</pre>
      </desc>
    </func>
    <func>
      <name name="max" arity="2"/>
      <fsummary>Return the largest of two term</fsummary>
      <desc>
        <p>Return the largest of <c><anno>Term1</anno></c> and <c><anno>Term2</anno></c>;
	if the terms compare equal, <c><anno>Term1</anno></c> will be returned.</p>
      </desc>
    </func>
    <func>
      <name name="md5" arity="1"/>
      <fsummary>Compute an MD5 message digest</fsummary>
      <desc>
        <p>Computes an <c>MD5</c> 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>See The MD5 Message Digest Algorithm (RFC 1321) for more
          information about MD5.</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 subsequent 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>Updates 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"/>
      <type name="memory_type"/>
      <fsummary>Information about dynamically allocated memory</fsummary>
      <desc>
        <p>Returns a list containing information about memory
          dynamically allocated by the Erlang emulator. Each element of
          the list 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 memory size in bytes. A description of
          each memory type follows:</p>
        <taglist>
          <tag><c>total</c></tag>
          <item>
            <p>The total amount of memory currently allocated, which is
              the same as the sum of 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 by
              the Erlang processes.</p>
          </item>
          <tag><c>processes_used</c></tag>
          <item>
            <p>The total amount of memory currently used by the Erlang
              processes.</p>
            <p>This memory 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 by
              the emulator that is not directly related to any Erlang
              process.</p>
            <p>Memory presented as <c>processes</c> is not included in
              this memory.</p>
          </item>
          <tag><c>atom</c></tag>
          <item>
            <p>The total amount of memory currently allocated for atoms.</p>
            <p>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.</p>
            <p>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.</p>
            <p>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.</p>
            <p>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.</p>
            <p>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.</p>
            <p>The total amount of memory allocated in low memory areas
	      that are restricted to less than 4 Gb even though
	      the system may have more physical memory.</p>
	    <p>May be removed in future releases of halfword emulator.</p>
          </item>
          <tag><c>maximum</c></tag>
          <item>
            <p>The maximum total amount of memory allocated since
              the emulator was started.</p>
            <p>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">instrument(3)</seealso>
              and/or <seealso marker="erts:erl">erl(1)</seealso>.</p>
          </item>
        </taglist>
        <note>
          <p>The <c>system</c> value is not complete. Some allocated
            memory that should be part of the <c>system</c> value are
            not.</p>
          <p>When the emulator is run with instrumentation,
            the <c>system</c> value is more accurate, but memory
            directly allocated by <c>malloc</c> (and friends) are 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>Since the <c>total</c> value is the sum of <c>processes</c>
            and <c>system</c> the error in <c>system</c> will propagate
            to the <c>total</c> value.</p>
	  <p>The different amounts of memory that are summed are
	    <em>not</em> gathered atomically which also introduce
	    an error in the result.</p>
        </note>
        <p>The different values has 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 may be added in the future.</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 stack(s) 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.
            Furthermore, due to fragmentation and pre-reservation of
            memory areas, the size of the memory segments which contain
            the dynamically allocated memory blocks can be substantially
            larger than the total size of the dynamically allocated
            memory blocks.</p>
        </note>
	<note>
	  <p>
	    Since erts version 5.6.4 <c>erlang:memory/0</c> requires that
	    all <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso>
	    allocators are enabled (default behaviour).
	  </p>
	</note>
        <p>Failure:</p>
        <taglist>
          <tag><c>notsup</c></tag>
          <item>
	    If an <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso>
	    allocator has been disabled.
	  </item>
	</taglist>
      </desc>
    </func>
    <func>
      <name name="memory" arity="1" clause_i="1"/>
      <name name="memory" arity="1" clause_i="2"/>
      <type name="memory_type"/>
      <fsummary>Information about dynamically allocated memory</fsummary>
      <desc>
        <p>Returns the memory size in bytes allocated for memory of
          type <c><anno>Type</anno></c>. The argument can also be given 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>
	    Since erts version 5.6.4 <c>erlang:memory/1</c> requires that
	    all <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso>
	    allocators are enabled (default behaviour).
	  </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
	    documentation of
	    <seealso marker="#memory/0">erlang:memory/0</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:erts_alloc">erts_alloc(3)</seealso>
	    allocator has been disabled.
	  </item>
	</taglist>
        <p>See also
          <seealso marker="#memory/0">erlang:memory/0</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="min" arity="2"/>
      <fsummary>Return the smallest of two term</fsummary>
      <desc>
        <p>Return the smallest of <c><anno>Term1</anno></c> and <c><anno>Term2</anno></c>;
	if the terms compare equal, <c><anno>Term1</anno></c> will be 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 returns <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">code(3)</seealso>) and should not be
            used elsewhere.</p>
        </warning>
      </desc>
    </func>
    <func>
      <name name="monitor" arity="2"/>
      <fsummary>Start monitoring</fsummary>
      <desc>
        <p>The calling process starts monitoring <c><anno>Item</anno></c> which is
          an object of type <c><anno>Type</anno></c>.</p>
        <p>Currently only processes can be monitored, i.e. the only
          allowed <c><anno>Type</anno></c> is <c>process</c>, but other types may be
          allowed in the future.</p>
        <p><c><anno>Item</anno></c> can be:</p>
        <taglist>
          <tag><c>pid()</c></tag>
          <item>
            <p>The pid of the process to monitor.</p>
          </item>
          <tag><c>{RegName, Node}</c></tag>
          <item>
            <p>A tuple consisting of a registered name of a process and
              a node name. The process residing on the node <c>Node</c>
              with the registered name <c>RegName</c> will be monitored.</p>
          </item>
          <tag><c>RegName</c></tag>
          <item>
            <p>The process locally registered as <c>RegName</c> will be
              monitored.</p>
          </item>
        </taglist>
        <note>
          <p>When a process is monitored by registered name, the process
            that has the registered name at the time when
            <c>monitor/2</c> is called will be monitored.
            The monitor will not be effected, if the registered name is
            unregistered.</p>
        </note>
        <p>A <c>'DOWN'</c> message will be sent to the monitoring
          process if <c><anno>Item</anno></c> dies, if <c><anno>Item</anno></c> does not exist,
          or if the connection is lost to the node which <c><anno>Item</anno></c>
          resides on. A <c>'DOWN'</c> message has the following pattern:</p>
        <code type="none">
{'DOWN', MonitorRef, Type, Object, Info}</code>
        <p>where <c>MonitorRef</c> and <c>Type</c> are the same as
          described above, and:</p>
        <taglist>
          <tag><c>Object</c></tag>
          <item>
            <p>A reference to the monitored object:</p>
            <list type="bulleted">
              <item>the pid of the monitored process, if <c><anno>Item</anno></c> was
               specified as a pid.</item>
              <item><c>{RegName, Node}</c>, if <c><anno>Item</anno></c> was specified as
              <c>{RegName, Node}</c>.</item>
              <item><c>{RegName, Node}</c>, if <c><anno>Item</anno></c> was specified as
              <c>RegName</c>. <c>Node</c> will in this case be the
               name of the local node (<c>node()</c>).</item>
            </list>
          </item>
          <tag><c>Info</c></tag>
          <item>
            <p>Either the exit reason of the process, <c>noproc</c>
              (non-existing process), or <c>noconnection</c> (no
              connection to <c><anno>Node</anno></c>).</p>
          </item>
        </taglist>
        <note>
          <p>If/when <c>monitor/2</c> is extended (e.g. to
            handle other item types than <c>process</c>), other
            possible values for <c>Object</c>, and <c>Info</c> in the
            <c>'DOWN'</c> message will be introduced.</p>
        </note>
        <p>The monitoring is turned off either when the <c>'DOWN'</c>
          message is sent, or when
          <seealso marker="#demonitor/1">demonitor/1</seealso>
          is called.</p>
        <p>If an attempt is made to monitor a process on an older node
          (where remote process monitoring is not implemented or one
          where remote process monitoring by registered name is not
          implemented), the call fails with <c>badarg</c>.</p>
        <p>Making several calls to <c>monitor/2</c> for the same
          <c><anno>Item</anno></c> is not an error; it results in as many, completely
          independent, monitorings.</p>
        <note>
          <p>The format of the <c>'DOWN'</c> message changed in the 5.2
            version of the emulator (OTP release R9B) for monitor <em>by registered name</em>. The <c>Object</c> element of
            the <c>'DOWN'</c> message could in earlier versions
            sometimes be the pid of the monitored process and sometimes
            be the registered name. Now the <c>Object</c> element is
            always a tuple consisting of the registered name and
            the node name. Processes on new nodes (emulator version 5.2
            or greater) will always get <c>'DOWN'</c> messages on
            the new format even if they are monitoring processes on old
            nodes. Processes on old nodes will always get <c>'DOWN'</c>
            messages on the old format.</p>
        </note>
      </desc>
    </func>
    <func>
      <name name="monitor_node" arity="2"/>
      <fsummary>Monitor the status of a node</fsummary>
      <desc>
        <p>Monitors 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,
          completely independent, monitorings.</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>, there will be an attempt 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 node.</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 <c>monitor_node/2</c> except that it allows an
          extra option to be given, namely <c>allow_passive_connect</c>.
          The option allows the BIF to wait the normal net connection
          timeout for the <em>monitored node</em> to connect itself,
          even if it cannot be actively connected from this node
          (i.e. it is blocked). The state where this might be useful can
          only be achieved by using the kernel option
          <c>dist_auto_connect once</c>. If that kernel option is not
          used, the <c>allow_passive_connect</c> option has no
          effect.</p>
        <note>
          <p>The <c>allow_passive_connect</c> option is used
            internally and is seldom needed in applications where the
            network topology and the kernel options in effect is 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="nif_error" arity="1"/>
      <fsummary>Stop execution with a given reason</fsummary>
      <desc>
        <p>Works exactly like
	 <seealso marker="#error/1">erlang:error/1</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
	 will not generate false warnings.</p>
      </desc>
    </func>
    <func>
      <name name="nif_error" arity="2"/>
      <fsummary>Stop execution with a given reason</fsummary>
      <desc>
        <p>Works exactly like
	 <seealso marker="#error/2">erlang:error/2</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
	 will 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 is a pid, port or reference located</fsummary>
      <desc>
        <p>Returns the node where <c><anno>Arg</anno></c> is located. <c><anno>Arg</anno></c> can
          be a pid, 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, excluding
          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 argument given.
          The result returned 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> can be any of the following:</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 which are known to this node, i.e., connected,
              previously connected, etc.</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>
        <p>If the local node is not alive,
          <c>nodes(this) == nodes(known) == [nonode@nohost]</c>, for
          any other <c><anno>Arg</anno></c> the empty list [] is returned.</p>
      </desc>
    </func>
    <func>
      <name name="now" arity="0"/>
      <type name="timestamp"/>
      <fsummary>Elapsed time since 00:00 GMT</fsummary>
      <desc>
        <p>Returns the tuple <c>{MegaSecs, Secs, MicroSecs}</c> which is
          the elapsed time since 00:00 GMT, January 1, 1970 (zero hour)
          on the assumption that the underlying OS supports this.
          Otherwise, some other point in time is chosen. It is also
          guaranteed that subsequent calls to this BIF returns
          continuously increasing values. Hence, the return value from
          <c>now()</c> can be used to generate unique time-stamps,
          and if it is called in a tight loop on a fast machine
          the time of the node can become skewed.</p>
        <p>It can only be used to check the local time of day if
          the time-zone info of the underlying operating system is
          properly configured.</p>
        <p>If you do not need the return value to be unique and
          monotonically increasing, use
          <seealso marker="kernel:os#timestamp/0">os:timestamp/0</seealso>
          instead to avoid some overhead.</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
	given in <c>cd</c>, <c>env</c>, <c>args</c> and <c>arg0</c> is subject to
	Unicode file name translation if the system is running
	in Unicode file name mode. To avoid
	translation or force i.e. UTF-8, supply the executable
	and/or arguments as a binary in the correct
	encoding. See the <seealso
	marker="kernel:file">file</seealso> module, the
	<seealso marker="kernel:file#native_name_encoding/0">
	  file:native_name_encoding/0</seealso> function and the
	  <seealso marker="stdlib:unicode_usage">stdlib users guide
	</seealso> for details.</p>

	<note><p>The characters in the name (if given as a list)
	can only be &gt; 255 if the Erlang VM is started in
	Unicode file name 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> is one of the following:</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 which will 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 will be started. A driver runs in the Erlang
              workspace, 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 with using
              <c>vfork</c>, setting the environment variable
              <c>ERL_NO_VFORK</c> to any value will cause <c>fork</c>
              to be used instead.</p>

	      <p>For external programs, the <c>PATH</c> is searched
	      (or an equivalent method is used to find programs,
	      depending on operating system). This is done by invoking
	      the shell on certain platforms. The first space
	      separated token of the command will be considered as the
	      name of the executable (or driver). This (among other
	      things) makes this option unsuitable for running
	      programs having spaces in file or directory names. Use
	      {spawn_executable, <anno>Command</anno>} instead if spaces in executable
	      file names is desired.</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. The <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>args</c> and <c>arg0</c> <c><anno>PortSettings</anno></c> can be used.</p>

	      <p>The shell is not usually invoked to start the
	      program, it's executed directly. Neither is the
	      <c>PATH</c> (or equivalent) searched. To find a program
	      in the PATH to execute, use <seealso
	      marker="kernel:os#find_executable/1">os:find_executable/1</seealso>.</p>
	      <p>Only if a shell script or <c>.bat</c> file is
	      executed, the appropriate command interpreter will
	      implicitly be invoked, but there will still be no
	      command argument expansion or implicit PATH search.</p>
  
	      <p>If the <c><anno>FileName</anno></c> cannot be run, an error
	      exception, with the posix error code as the reason, is
	      raised. The error reason may differ between operating
	      systems. Typically the error <c>enoent</c> is raised
	      when one tries to run a program that is not found and
	      <c>eaccess</c> is raised when the given 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 operating system
              (<c>shell</c> and <c>user</c>). Hence, its use is very
              limited.</p>
          </item>
        </taglist>
        <p><c><anno>PortSettings</anno></c> is a list of settings for the port.
          Valid settings are:</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. Valid values
              for <c>N</c> are 1, 2, or 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 one single message. The message data format
              is <c>{Flag, Line}</c>, where <c>Flag</c> is either
              <c>eol</c> or <c>noeol</c> and <c>Line</c> is the actual
              data delivered (without the newline sequence).</p>
            <p><c><anno>L</anno></c> specifies the maximum line length in bytes.
              Lines longer than this will be delivered in more than one
              message, with the <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 will also be delivered with
              the <c>Flag</c> set to <c>noeol</c>. In all other cases,
              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>This is 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>This is 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> should 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 <c>os:getenv/1</c>), which
              removes the environment variable.
	    </p>
          </item>
	  <tag><c>{args, [ string() | binary() ]}</c></tag>
          <item>

	    <p>This option is only valid for <c>{spawn_executable, <anno>FileName</anno>}</c>
	    and specifies arguments to the executable. Each argument
	    is given as a separate string and (on Unix) eventually
	    ends up as one element each in the argument vector. On
	    other platforms, similar behavior is mimicked.</p>

	    <p>The arguments are not expanded by the shell prior to
	      being supplied to the executable, most notably this
	      means that file wildcard expansion will not happen. Use
	      <seealso
	      marker="stdlib:filelib#wildcard/1">filelib:wildcard/1</seealso>
	      to expand wildcards for the arguments. Note that even if
	      the program is a Unix shell script, meaning that the
	      shell will ultimately be invoked, wildcard expansion
	      will not happen and the script will be provided with the
	      untouched arguments. On Windows&reg;, wildcard expansion
	      is always up to the program itself, why this isn't an
	      issue.</p>

	    <p>Note also that the actual executable name (a.k.a. <c>argv[0]</c>)
	    should not be given in this list. The proper executable name will
	    automatically be used as argv[0] where applicable.</p>

	    <p>If one, for any reason, wants to explicitly set the
	    program name in the argument vector, the <c>arg0</c>
	    option can be used.</p>

          </item>
	  <tag><c>{arg0, string() | binary()}</c></tag>
          <item>

	    <p>This option is only valid for <c>{spawn_executable, <anno>FileName</anno>}</c>
	    and explicitly specifies the program name argument when
	    running an executable. This might in some circumstances,
	    on some operating systems, 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>This is 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 (i.e., 128+signal).</p>
            <p>If the <c>eof</c> option has been given as well,
              the <c>eof</c> message and the <c>exit_status</c> message
              appear in an unspecified order.</p>
            <p>If the port program closes its stdout without exiting,
              the <c>exit_status</c> option will not work.</p>
          </item>
          <tag><c>use_stdio</c></tag>
          <item>
            <p>This is 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>. 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&reg; only.
	    The standard input and standard output handles of the port program
	    will, if this option is supplied, be opened with the flag
	    FILE_FLAG_OVERLAPPED, so that the port program can (and has to) 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 IO from the port are binary data objects as opposed
              to lists of bytes.</p>
          </item>
          <tag><c>eof</c></tag>
          <item>
            <p>The port will not be closed at the end of the file and
              produce an exit signal. Instead, it will remain open and
              a <c>{Port, eof}</c> message will be sent to the process
              holding the port.</p>
          </item>
          <tag><c>hide</c></tag>
          <item>
            <p>When running on Windows, suppress creation of a new
	      console window when spawning the port program.
	      (This option has no effect on other platforms.)</p>
          </item>
          <tag><marker id="open_port_parallelism"><c>{parallelism, Boolean}</c></marker></tag>
          <item>
            <p>Set scheduler hint for port parallelism. If set to <c>true</c>,
	    the VM will schedule port tasks when it by this can improve the
	    parallelism in the system. If set to <c>false</c>, the VM will
	    try to perform port tasks immediately and by this improving the
	    latency at the expense of parallelism. The default can be set on
	    system startup by passing the
	    <seealso marker="erl#+spp">+spp</seealso> command line argument
	    to <seealso marker="erl">erl(1)</seealso>.
	    </p>
          </item>
        </taglist>
        <p>The default is <c>stream</c> for all types of port 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 which
	  most closely describes the error, or <c>einval</c> if no Posix code
	  is appropriate:</p>
        <taglist>
          <tag><c>badarg</c></tag>
          <item>
            <p>Bad input arguments to <c>open_port</c>.</p>
          </item>
          <tag><c>system_limit</c></tag>
          <item>
            <p>All available ports in the Erlang emulator are in use.</p>
          </item>
          <tag><c>enomem</c></tag>
          <item>
            <p>There was not enough memory to create the port.</p>
          </item>
          <tag><c>eagain</c></tag>
          <item>
            <p>There are no more available operating system processes.</p>
          </item>
          <tag><c>enametoolong</c></tag>
          <item>
            <p>The external command given was too long.</p>
          </item>
          <tag><c>emfile</c></tag>
          <item>
            <p>There are no more available file descriptors (for the operating system process
	    that the Erlang emulator runs in).</p>
          </item>
          <tag><c>enfile</c></tag>
          <item>
            <p>The file table is full (for the entire operating system).</p>
          </item>
          <tag><c>eacces</c></tag>
          <item>
            <p>The <c>Command</c> given in <c>{spawn_executable, Command}</c> does not point out an executable file.</p>
          </item>
          <tag><c>enoent</c></tag>
          <item>
            <p>The <c><anno>FileName</anno></c> given in <c>{spawn_executable, <anno>FileName</anno>}</c> does not point out an existing file.</p>
          </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>. See <c>file(3)</c> for
          possible values of <c>PosixCode</c>.</p>
	  <p>The maximum number of ports that can be open at the same
          time can be configured by passing the 
	  <seealso marker="erl#max_ports"><c>+Q</c></seealso>
	  command line flag to
	  <seealso marker="erl"><c>erl(1)</c></seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="phash" arity="2"/>
      <type_desc variable="Range">Range = 1..2^32, Hash = 1..Range</type_desc>
      <fsummary>Portable hash function</fsummary>
      <desc>
        <p>Portable hash function that will give 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). Range
          can be between 1 and 2^32, the function returns a hash value
          for <c><anno>Term</anno></c> within the range <c>1..<anno>Range</anno></c>.</p>
        <p>This BIF could be used instead of the old deprecated
          <c>erlang:hash/2</c> BIF, as it calculates better hashes for
          all data-types, but consider using <c>phash2/1,2</c> instead.</p>
      </desc>
    </func>
    <func>
      <name name="phash2" arity="1"/>
      <name name="phash2" arity="2"/>
      <type_desc variable="Range">1..2^32</type_desc>
      <type_desc variable="Hash">0..Range-1</type_desc>
      <fsummary>Portable hash function</fsummary>
      <desc>
        <p>Portable hash function that will give the same hash for
          the same Erlang term regardless of machine architecture and
          ERTS version (the BIF was introduced in ERTS 5.2). Range can
          be between 1 and 2^32, the function returns a hash value for
          <c><anno>Term</anno></c> within the range <c>0..<anno>Range</anno>-1</c>. When called
          without the <c><anno>Range</anno></c> argument, a value in the range
          <c>0..2^27-1</c> is returned.</p>
        <p>This BIF should always 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>Note that the range <c>0..<anno>Range</anno>-1</c> is different from
          the range of <c>phash/2</c> (<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 which corresponds to the text
          representation of <c><anno>Pid</anno></c>.</p>
        <warning>
          <p>This BIF is intended for debugging and for use in
            the Erlang operating system. It should not be used in
            application programs.</p>
        </warning>
      </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 behaviour
          (see below), being synchronous, and that the port does
	  <em>not</em> reply with <c>{Port, closed}</c>. Any process may
	  close a port with <c>port_close/1</c>, not only the port owner
	  (the connected process).</p>
        <p>For comparison: <c><anno>Port</anno> ! {self(), close}</c> fails with
          <c>badarg</c> if <c><anno>Port</anno></c> cannot be sent to (i.e.,
          <c><anno>Port</anno></c> refers neither to a port nor to 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, but if
          the calling process is not the port owner the <em>port owner</em> fails with <c>badsig</c>.</p>
        <p>Note that any process can close a port using
          <c><anno>Port</anno> ! {PortOwner, close}</c> just as if it itself was
          the port owner, but the reply always goes to the port owner.</p>
	<p>As of OTP-R16 <c><anno>Port</anno> ! {PortOwner, close}</c> is truly
	   asynchronous. Note 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. This due to its error
	   behavior.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an open port or
          the registered name of an open port.</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
          behaviour and being synchronous (see below). Any process may
	  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>
          fails with <c>badarg</c> if <c><anno>Port</anno></c> cannot be sent to
          (i.e., <c><anno>Port</anno></c> refers neither to a port nor to 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 not a valid IO list.</p>
        <p>Note that any process can send to a port using
          <c><anno>Port</anno> ! {PortOwner, {command, <anno>Data</anno>}}</c> just as if it
          itself was the port owner.</p>
	<p>If the port is busy, the calling process will be suspended
	   until the port is not busy anymore.</p>
	<p>As of OTP-R16 <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> is
	   truly asynchronous. Note 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. This due to its error
	   behavior.</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>Data</anno></c> is not a valid io list.
	  </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> is returned.</p>
	<p>If the port is busy, the calling process will be suspended
	   until the port is not busy anymore.</p>
        <p>Currently the following <c><anno>Option</anno></c>s are valid:</p>
        <taglist>
          <tag><c>force</c></tag>
          <item>The calling process will not be suspended if the port is
	        busy; instead, the port command is forced through. The
		call will fail with a <c>notsup</c> exception if the
		driver of the port does not support this. For more
		information see the
		<seealso marker="driver_entry#driver_flags"><![CDATA[ERL_DRV_FLAG_SOFT_BUSY]]></seealso>
		driver flag.
          </item>
          <tag><c>nosuspend</c></tag>
          <item>The calling process will not be suspended if the port is
	        busy; instead, the port command is aborted and
		<c>false</c> is returned. 
          </item>
        </taglist>
        <note>
          <p>More options may be added in the future.</p>
        </note>
        <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>Data</anno></c> is not a valid io list.
	  </item>
          <tag><c>badarg</c></tag>
          <item>
	    If <c><anno>OptionList</anno></c> is not a valid option list.
	  </item>
          <tag><c>notsup</c></tag>
          <item>
	    If the <c>force</c> option 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 have to call
          <c>unlink(Port)</c> if this is not desired. Any process may
          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> fails
          with <c>badarg</c> if <c><anno>Port</anno></c> cannot be sent to (i.e.,
          <c><anno>Port</anno></c> refers neither to a port nor to 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. Note that the old port owner is still linked to
          the port, and that 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 pid.</p>
        <p>Note that any process can set the port owner using
          <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c> just as if it
          itself was the port owner, but the reply always goes to
          the port owner.</p>
	<p>As of OTP-R16 <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c> is
	   truly asynchronous. Note 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. This due to its error
	   behavior.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an open port
          or the registered name of an open port, or if <c>Pid</c> is
          not an existing local pid.</p>
      </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, i.e., on the port driver. Not all port drivers
          support this control feature.</p>
        <p>Returns: a list of integers in the range 0 through 255, or a
          binary, depending on the port driver. The meaning of
          the returned data also depends on the port driver.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an open port or
          the registered name of an open port, if <c><anno>Operation</anno></c>
          cannot fit in a 32-bit integer, if the port driver does not
          support synchronous control operations, or if the port driver
          so decides for any reason (probably something wrong with
          <c><anno>Operation</anno></c> or <c><anno>Data</anno></c>).</p>
      </desc>
    </func>
    <func>
      <name name="port_call" arity="3"/>
      <fsummary>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, i.e.,
          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>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an open port or
          the registered name of an open port, if <c><anno>Operation</anno></c>
          cannot fit in a 32-bit integer, if the port driver does not
          support synchronous control operations, or if the port driver
          so decides for any reason (probably something wrong with
          <c><anno>Operation</anno></c> or <c><anno>Data</anno></c>).</p>
      </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
          the <c><anno>Port</anno></c>, or <c>undefined</c> if the port is not open.
          The order of the tuples is not defined, nor are all the
          tuples mandatory.</p>
	<p>Currently the result will containt information about the
	following <c>Item</c>s: <c>registered_name</c> (if the port has
	a registered name), <c>id</c>, <c>connected</c>, <c>links</c>,
	<c>name</c>, <c>input</c>, and <c>output</c>. For more information
	about the different <c>Item</c>s, see
	<seealso marker="#port_info/2">port_info/2</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.</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 may 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.</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.</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.</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 currently either <c>false</c>
	(emulator without SMP support), <c>port_level</c> (port specific
	locking), or <c>driver_level</c> (driver specific locking). Note
	that these results are highly implementation specific and might
	change in the future.</p>
	<p>If the port identified by <c><anno>Port</anno></c> is not open,
	<c>undefined</c> is returned.</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 amount of memory,
	in bytes, allocated for this port by the runtime system. Note
	that the port itself might have allocated memory which 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.</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 that this port
	is monitoring.</p>
	<p>If the port identified by <c><anno>Port</anno></c> is not open,
	<c>undefined</c> is returned.</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>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">open_port/2</seealso>.</p>
	<p>If the port identified by <c><anno>Port</anno></c> is not open,
	<c>undefined</c> is returned.</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 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">open_port({spawn | spawn_executable,
	Command}, Options)</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.</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 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 either
	<seealso marker="#port_command/2">port_command/2</seealso>,
	<seealso marker="#port_command/3">port_command/3</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.</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 parallelism hint of a port</fsummary>
      <desc>
	<p><c><anno>Boolean</anno></c> corresponds to the port parallelism
	hint being used by this port. For more information see
	the <seealso marker="#open_port_parallelism">parallelism</seealso>
	option of <seealso marker="#open_port/2">open_port/2</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="port_info" arity="2" clause_i="12"/>
      <fsummary>Information about the queue size of a port</fsummary>
      <desc>
	<p><c><anno>Bytes</anno></c> is the total amount of data,
	in 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.</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="13"/>
      <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.</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 which corresponds to the text
          representation of the port identifier <c><anno>Port</anno></c>.</p>
        <warning>
          <p>This BIF is intended for debugging and for use in
            the Erlang operating system. It should not be used in
            application programs.</p>
        </warning>
      </desc>
    </func>
    <func>
      <name name="ports" arity="0"/>
      <fsummary>All open ports</fsummary>
      <desc>
	<p>Returns a list of port identifiers corresponding to all the
	ports currently existing on the local node.</p>

	<p>Note that a port that is exiting, exists but is not open.</p>
      </desc>
    </func>
    <func>
      <name name="pre_loaded" arity="0"/>
      <fsummary>List of all pre-loaded modules</fsummary>
      <desc>
        <p>Returns a list of Erlang modules which are pre-loaded 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 pre-loaded.</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 currently 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 should normally
          not trap exits.</p>
        <p>Returns the old value of the flag.</p>
        <p>See also <seealso marker="#exit/2">exit/2</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>This is used by a process to redefine the error handler
          for undefined function calls and undefined registered
          processes.  Inexperienced users should not use this flag
          since code auto-loading is dependent 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"/>
      <fsummary>Set process flag min_heap_size for the calling process</fsummary>
      <desc>
        <p>This 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>This 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"/>
      <type name="priority_level"/>
      <fsummary>Set process flag priority for the calling process</fsummary>
      <desc>
        <p><marker id="process_flag_priority"></marker>
          This sets the process priority. <c><anno>Level</anno></c> is an atom.
          There are currently four priority levels: <c>low</c>,
          <c>normal</c>, <c>high</c>, and <c>max</c>. The default
          priority level is <c>normal</c>. <em>NOTE</em>: The
          <c>max</c> priority level is reserved for internal use in
          the Erlang runtime system, and should <em>not</em> be used
          by others.
        </p>
        <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
          priority <c>low</c> will be interleaved. Processes on
          priority <c>low</c> will be selected for execution less
          frequently than processes on priority <c>normal</c>.
        </p>
        <p>When there are runnable processes on priority <c>high</c>
          no processes on priority <c>low</c>, or <c>normal</c> will
          be selected for execution. Note, however, that this does
          <em>not</em> mean that no processes on priority <c>low</c>,
          or <c>normal</c> will be able to run when there are
          processes on priority <c>high</c> running. On the runtime
          system with SMP support there might be more processes running
          in parallel than processes on priority <c>high</c>, i.e.,
          a <c>low</c>, and a <c>high</c> priority process might
          execute at the same time.
        </p>
        <p>When there are runnable processes on priority <c>max</c>
          no processes on priority <c>low</c>, <c>normal</c>, or
          <c>high</c> will be selected for execution. As with the
          <c>high</c> priority, processes on lower priorities might
          execute in parallel with processes on priority <c>max</c>.
        </p>
        <p>Scheduling is preemptive. Regardless of priority, a process
          is preempted when it has consumed more than a certain amount
          of reductions since the last time it was selected for
          execution.
        </p>
        <p><em>NOTE</em>: You should not depend on the scheduling
          to remain exactly as it is today. Scheduling, at least on
          the runtime system with SMP support, is very likely to be
          modified in the future in order to better utilize available
          processor cores.
        </p>
        <p>There is currently <em>no</em> automatic mechanism for
          avoiding priority inversion, such as priority inheritance,
          or priority ceilings. When using priorities you have
          to 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 don't have control over may cause the <c>high</c>
          priority process to wait for a processes with lower
          priority, i.e., effectively decreasing the priority of the
          <c>high</c> priority process during the call. Even if this
          isn't the case with one version of the code that you don't
          have under your control, it might be the case in a future
          version of it. This might, for example, happen if a
          <c>high</c> priority process triggers code loading, since
          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, they need to be used
          with care, especially the <c>high</c> priority <em>must</em>
          be used with care. A process on <c>high</c> priority should
          only perform work for short periods of time. Busy looping for
          long periods of time in a <c>high</c> priority process will
          most likely cause problems, since there are important servers
          in OTP running 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="6"/>
      <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, which 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: a tuple <c>{Module, Function, Arity}</c> for
          function calls, and the mere 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). 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="7"/>
      <fsummary>Set process flag sensitive for the calling process</fsummary>
      <desc>
        <p>Set or clear the <c>sensitive</c> flag for the current process.
          When a process has been marked as sensitive by calling
          <c>process_flag(sensitive, true)</c>, features in the run-time
          system that can be used for examining the data and/or inner working
          of the process are silently disabled.</p>
        <p>Features that are disabled include (but are not limited to)
          the following:</p>
        <p>Tracing: Trace flags can still be set for the process, but no
          trace messages of any kind will be generated.
          (If the <c>sensitive</c> flag is turned off, trace messages will
          again be generated if there are any trace flags set.)</p>
        <p>Sequential tracing: The sequential trace token will be propagated
          as usual, but no sequential trace messages will be generated.</p>
        <p><c>process_info/1,2</c> cannot be used to read out the message
          queue or the process dictionary (both will be 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
          will be omitted.</p>
        <p>If <c>{save_calls,N}</c> has been set for the process, no
          function calls will be saved to the call saving list.
          (The call saving list will not be cleared; furthermore, send, receive,
          and timeout events will still be 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">process_flag/2</seealso>.
          Returns the old value of the flag. The allowed 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"/>
      <type name="process_info_result_item"/>
      <type name="priority_level"/>
      <type name="stack_item"/>
      <fsummary>Information about a process</fsummary>
      <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 not defined, nor
	  are all the <c><anno>InfoTuple</anno></c>s mandatory. The <c><anno>InfoTuple</anno></c>s
	  part of the result may be changed without prior notice.
	  Currently <c><anno>InfoTuple</anno></c>s with the following items
	  are part of the result:
	  <c>current_function</c>, <c>initial_call</c>, <c>status</c>,
	  <c>message_queue_len</c>, <c>messages</c>, <c>links</c>,
	  <c>dictionary</c>, <c>trap_exit</c>, <c>error_handler</c>,
	  <c>priority</c>, <c>group_leader</c>, <c>total_heap_size</c>,
	  <c>heap_size</c>, <c>stack_size</c>, <c>reductions</c>, and
	  <c>garbage_collection</c>.
	  If the process identified by <c><anno>Pid</anno></c> has a registered name
	  also an <c><anno>InfoTuple</anno></c> with the item <c>registered_name</c>
	  will appear.
	</p>
	<p>See <seealso marker="#process_info/2">process_info/2</seealso>
	   for information about specific <c><anno>InfoTuple</anno></c>s.</p>
        <warning>
          <p>This BIF is intended for <em>debugging only</em>, use
	  <seealso marker="#process_info/2">process_info/2</seealso>
	  for all other purposes.
	  </p>
        </warning>
        <p>Failure: <c>badarg</c> if <c>Pid</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"/>
      <type name="process_info_item"/>
      <type name="process_info_result_item"/>
      <type name="stack_item"/>
      <type name="priority_level"/>
      <fsummary>Information about a process</fsummary>
      <desc>
        <p>Returns information about the process identified by <c><anno>Pid</anno></c>
	   as specified by the <c><anno>Item</anno></c> or the <c><anno>ItemList</anno></c>, or <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 given,
           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 due to
	   historical reasons, and is kept for backward compatibility.
	</p>
	<p>If an  <c>ItemList</c> is given, the result is an
	   <c><anno>InfoTupleList</anno></c>. The <c><anno>InfoTuple</anno></c>s in the
	   <c><anno>InfoTupleList</anno></c> will appear with the corresponding
	   <c><anno>Item</anno></c>s in the same order as the <c><anno>Item</anno></c>s appeared
	   in the <c><anno>ItemList</anno></c>. Valid <c><anno>Item</anno></c>s may appear multiple
	   times in the <c><anno>ItemList</anno></c>.
	</p>
	 <note><p>If <c>registered_name</c> is part of an <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>
		  appear in the resulting <c><anno>InfoTupleList</anno></c>. This
		  behavior is different than when a single
		  <c>Item =:= registered_name</c> is given, and than when
		  <c>process_info/1</c> is used.
	</p></note>
	<p>Currently the following <c><anno>InfoTuple</anno></c>s with corresponding
	   <c><anno>Item</anno></c>s are valid:</p>
        <taglist>
          <tag><c>{backtrace, <anno>Bin</anno>}</c></tag>
          <item>
            <p>The 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 currently being referred to by this process.
	      This <c><anno>InfoTuple</anno></c> may be changed or removed without prior
	      notice.</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> may be
	    changed or removed without prior notice.</p>
          </item>
          <tag><c>{current_function, {<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 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 that describes the
	      location in the source code.
	    </p>
          </item>
          <tag><c>{current_stacktrace, <anno>Stack</anno>}</c></tag>
          <item>
            <p>Return 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">erlang:get_stacktrace/0</seealso>.
	    </p>
          </item>
          <tag><c>{dictionary, <anno>Dictionary</anno>}</c></tag>
          <item>
            <p><c><anno>Dictionary</anno></c> is the dictionary of the process.</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 which contains miscellaneous
	       information about garbage collection for this process.
	       The content of <c><anno>GCInfo</anno></c> may be changed without
	       prior notice.</p>
          </item>
          <tag><c>{group_leader, <anno>GroupLeader</anno>}</c></tag>
          <item>
            <p><c><anno>GroupLeader</anno></c> is group leader for the IO 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 youngest heap generation
	    of the process. This generation currently include the stack
	    of the process. This information is highly implementation
	    dependent, and may change if the implementation change.
	    </p>
          </item>
          <tag><c>{initial_call, {Module, Function, Arity}}</c></tag>
          <item>
            <p><c>Module</c>, <c>Function</c>, <c>Arity</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 pids 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">process_flag/3</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 info 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 pids that are 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 pid, the list item
              is <c>{process, <anno>Pid</anno>}</c>, and for a remote process
              monitor by name, the list item is
              <c>{process, {<anno>RegName</anno>, <anno>Node</anno>}}</c>.</p>
          </item>
          <tag><c>{priority, Level}</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">process_flag(priority, Level)</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 name of the process. 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> the sequential trace token for
	    the process. This <c><anno>InfoTuple</anno></c> may 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 of the process in words.</p>
          </item>
          <tag><c>{status, <anno>Status</anno>}</c></tag>
          <item>
            <p><c><anno>Status</anno></c> is the status of the process. <c><anno>Status</anno></c>
              is <c>exiting</c>, <c>garbage_collecting</c>,
              <c>waiting</c> (for a message), <c>running</c>,
              <c>runnable</c> (ready to run, but another process is
              running), or <c>suspended</c> (suspended on a "busy" port
              or by the <c>erlang:suspend_process/[1,2]</c> BIF).</p>
          </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 pid of a process that have been or is to
	    be suspended by the process identified by <c><anno>Pid</anno></c> via the
	    <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso>
	    BIF, or the
	    <seealso marker="#suspend_process/1">erlang:suspend_process/1</seealso>
	    BIF. <c><anno>ActiveSuspendCount</anno></c> is the number of times the
	    <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,
	    if <c><anno>ActiveSuspendCount</anno> =/= 0</c>, <c><anno>Suspendee</anno></c> is
	    currently in the suspended state, and if
	    <c><anno>OutstandingSuspendCount</anno> =/= 0</c> the <c>asynchronous</c>
	    option of <c>erlang:suspend_process/2</c> has been used and
	    the suspendee has not yet been suspended by <c><anno>Pid</anno></c>.
	    Note that the <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>Pid</c>.
	    </p>
          </item>
          <tag><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 currently include the stack
	    of the process.
	    </p>
          </item>
          <tag><c>{trace, <anno>InternalTraceFlags</anno>}</c></tag>
          <item>
            <p><c><anno>InternalTraceFlags</anno></c> is an integer representing
	    internal trace flag for this process. This <c><anno>InfoTuple</anno></c>
	    may 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 it is <c>false</c>.</p>
          </item>
        </taglist>
        <p>Note however, that not all implementations support every one
          of the above <c><anno>Item</anno></c>s.</p>
        <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c> is not a local process,
	or if <c><anno>Item</anno></c> is not a valid <c><anno>Item</anno></c>.</p>
      </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>Note that a process that is exiting, exists but is not alive, i.e.,
	   <c>is_process_alive/1</c> will return <c>false</c> for a process
	   that is exiting, but its process identifier will be part
	   of the result returned from <c>processes/0</c>.
	</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,
          <c>erlang:check_process_code/2</c> should be called to check
          that no processes are executing old code in the module.</p>
        <warning>
          <p>This BIF is intended for the code server (see
            <seealso marker="kernel:code">code(3)</seealso>) and should not be
            used elsewhere.</p>
        </warning>
        <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> already exists, the old value is deleted and
          replaced by <c><anno>Val</anno></c> and the function returns the old value.</p>
        <note>
          <p>The values stored when <c>put</c> is evaluated within
            the scope of a <c>catch</c> will not be retracted if a
            <c>throw</c> is evaluated, or if an error occurs.</p>
        </note>
        <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>
      </desc>
    </func>
    <func>
      <name name="raise" arity="3"/>
      <type name="raise_stacktrace"/>
      <fsummary>Stop execution with an exception of given class, reason and call stack backtrace</fsummary>
      <desc>
        <p>Stops the execution of the calling process with an
          exception of given class, reason and call stack backtrace
          (<em>stacktrace</em>).</p>
        <warning>
          <p>This BIF is intended for debugging and for use in
            the Erlang operating system. In general, it should
            be avoided in applications, unless you know
            very well what you are doing.</p>
        </warning>
        <p><c><anno>Class</anno></c> is one of <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>.
          <c><anno>Reason</anno></c> is any term and <c><anno>Stacktrace</anno></c> is a list as
          returned from <c>get_stacktrace()</c>, that is a list of
          4-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 may 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>The <c>Location</c> element 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 will be truncated to the current
          maximum stacktrace depth.</p>
        <p>Because 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>, that is <c>badarg</c>. If you want to be
          really 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>Number of milliseconds remaining for a timer</fsummary>
      <desc>
        <p><c><anno>TimerRef</anno></c> is a timer reference returned by
          <seealso marker="#send_after/3">erlang:send_after/3</seealso>
          or
          <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>.
          If the timer is active, the function returns the time in
          milliseconds left until the timer will expire, otherwise
          <c>false</c> (which means that <c><anno>TimerRef</anno></c> was never a
          timer, that it has been cancelled, or that it has already
          delivered its message).</p>
        <p>See also 
          <seealso marker="#send_after/3">erlang:send_after/3</seealso>,
          <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>,
          and
          <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="ref_to_list" arity="1"/>
      <fsummary>Text representation of a reference</fsummary>
      <desc>
        <p>Returns a string which corresponds to the text
          representation of <c><anno>Ref</anno></c>.</p>
        <warning>
          <p>This BIF is intended for debugging and for use in
            the Erlang operating system. It should not 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 pid or a port
          identifier. <c><anno>RegName</anno></c>, which must be an atom, can be used
          instead of the pid / port identifier in the send operator
          (<c><anno>RegName</anno> ! Message</c>).</p>
        <pre>
> <input>register(db, Pid).</input>
true</pre>
        <p>Failure: <c>badarg</c> if <c><anno>PidOrPort</anno></c> is not an existing,
          local process or port, if <c><anno>RegName</anno></c> is already in use,
          if the process or port is already registered (already has a
          name), or if <c><anno>RegName</anno></c> is the atom <c>undefined</c>.</p>
      </desc>
    </func>
    <func>
      <name name="registered" arity="0"/>
      <fsummary>All registered names</fsummary>
      <desc>
        <p>Returns a list of names which have been registered using
          <seealso marker="#register/2">register/2</seealso>.</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> should previously have been
	suspended via
	<seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso>,
	or
	<seealso marker="#suspend_process/1">erlang:suspend_process/1</seealso>
	by the process calling <c>erlang:resume_process(<anno>Suspendee</anno>)</c>. When
	the suspend count on <c><anno>Suspendee</anno></c> reach zero, <c><anno>Suspendee</anno></c>
	will be resumed, i.e., the state of the <c>Suspendee</c> is changed
	from suspended into the state <c><anno>Suspendee</anno></c> was in 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> isn't 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>.</p>
        <pre>
> <input>round(5.5).</input>
6</pre>
        <p>Allowed in guard tests.</p>
      </desc>
    </func>
    <func>
      <name name="self" arity="0"/>
      <fsummary>Pid of the calling process</fsummary>
      <desc>
        <p>Returns the pid (process identifier) of the calling process.</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> may be a remote or local pid, 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"/>
      <type name="dst"/>
      <fsummary>Send a message conditionally</fsummary>
      <desc>
        <p>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">erlang:send/2</seealso>. See
          also
          <seealso marker="#send_nosuspend/2">erlang:send_nosuspend/2,3</seealso>.
          for more detailed explanation and warnings.</p>
        <p>The possible options are:</p>
        <taglist>
          <tag><c>nosuspend</c></tag>
          <item>
            <p>If the sender would have to be suspended to do the send,
              <c>nosuspend</c> is returned instead.</p>
          </item>
          <tag><c>noconnect</c></tag>
          <item>
            <p>If the destination node would have to be auto-connected
              before doing the send, <c>noconnect</c> is returned
              instead.</p>
          </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"/>
      <type_desc variable="Time">0 &lt;= Time &lt;= 4294967295</type_desc>
      <fsummary>Start a timer</fsummary>
      <desc>
        <p>Starts a timer which will send the message <c>Msg</c>
          to <c><anno>Dest</anno></c> after <c><anno>Time</anno></c> milliseconds.</p>
	<p>If <c><anno>Dest</anno></c> is a <c>pid()</c> it has to be a <c>pid()</c> of a local process, dead or alive.</p>
	<p>The <c><anno>Time</anno></c> value can, in the current implementation, not be greater than 4294967295.</p>
        <p>If <c><anno>Dest</anno></c> is an <c>atom()</c>, it is supposed to be the name of
          a registered process. The process referred to by the name is
          looked up at the time of delivery. No error is given if
          the name does not refer to a process.</p>

        <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will be automatically
          canceled if the process referred to by the <c>pid()</c> is not alive,
          or when the process exits. This feature was introduced in
          erts version 5.4.11. Note that timers will not be
          automatically canceled when <c><anno>Dest</anno></c> is an <c>atom</c>.</p>
        <p>See also
          <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>,
          <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>,
          and
          <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p>
        <p>Failure: <c>badarg</c> if the arguments does not satisfy
          the requirements specified above.</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">erlang:send(<anno>Dest</anno>, <anno>Msg</anno>, [nosuspend])</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 towards 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>will not send the message</em> but return <c>false</c> instead.</p>
        <p>The same happens, 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 very 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 will actually
          be shut down (due to tick timeouts) by <c>net_kernel</c>. The
          normal reaction to take when this happens is some kind of
          premature shutdown of the other node.</p>
        <p>Note that ignoring the return value from this function would
          result in <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>Note also that in many systems, transient states of
          overloaded queues are normal. The fact that this function
          returns <c>false</c> does not in any way 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 could be sent on the (TCP) channel
          without blocking, the message is not guaranteed to have
          arrived at the remote node. Also in the case of a disconnected
          non-responsive node, the return value is <c>true</c> (mimics
          the behaviour of the <c>!</c> operator). The expected
          behaviour as well as 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">erlang:send(<anno>Dest</anno>, <anno>Msg</anno>, [nosuspend | <anno>Options</anno>])</seealso>,
          but with boolean return value.</p>
        <p>This function behaves like
          <seealso marker="#send_nosuspend/2">erlang:send_nosuspend/2)</seealso>,
          but takes a third parameter, a list of options. The only
          currently implemented option is <c>noconnect</c>. The option
          <c>noconnect</c> makes the function return <c>false</c> if
          the remote node is not currently reachable by the local
          node. The normal behaviour is to try to connect to the node,
          which may stall the process for a shorter period. The use of
          the <c>noconnect</c> option makes it possible to be
          absolutely sure not to get even the slightest delay when
          sending to a remote process. This is especially useful when
          communicating with nodes who expect to always be
          the connecting part (i.e. 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
          <seealso marker="doc/reference_manual:distributed">Distributed Erlang</seealso> in the Erlang Reference Manual).</p>
        <p>Failure: <c>function_clause</c> if the local node is not
          alive.</p>
      </desc>
    </func>
    <func>
      <name name="setelement" arity="3"/>
      <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno>)</type_desc>
      <fsummary>Set Nth element of a tuple</fsummary>
      <desc>
        <p>Returns a tuple which is a copy of the argument <c><anno>Tuple1</anno></c>
          with the element given by the integer argument <c><anno>Index</anno></c>
          (the first element is the element with index 1) replaced by
          the argument <c><anno>Value</anno></c>.</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 an integer which is the size of the argument
          <c><anno>Item</anno></c>,  which must be either a tuple or a binary.</p>
        <pre>
> <input>size({morni, mulle, bwange}).</input>
3</pre>
        <p>Allowed in guard tests.</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 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/3">spawn/3</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="spawn" arity="2"/>
      <fsummary>Create a new process with a fun as entry point on a given node</fsummary>
      <desc>
        <p>Returns the 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/3">spawn/3</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 pid of a new process started by the application
          of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c>. The new process
          created will be placed in the system scheduler queue and be
          run some time later.</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">process_flag/2</seealso>).
          If <c>error_handler</c> is undefined, or the user has
          redefined the default <c>error_handler</c> its replacement is
          undefined, a failure with the reason <c>undef</c> will occur.</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 given node</fsummary>
      <desc>
        <p>Returns the 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>Node</c>. If
          <c><anno>Node</anno></c> does not exists, a useless pid is returned.
          Otherwise works like
          <seealso marker="#spawn/3">spawn/3</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 pid of a new process started by the application
          of <c><anno>Fun</anno></c> to the empty list []. A link is created between
          the calling process and the new process, atomically.
          Otherwise works like
          <seealso marker="#spawn/3">spawn/3</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 pid of a new process started by the application
          of <c><anno>Fun</anno></c> to the empty list [] 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 due to the link, an exit signal with exit
          reason <c>noconnection</c> will be received). Otherwise works
          like <seealso marker="#spawn/3">spawn/3</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 pid 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">spawn/3</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 given node</fsummary>
      <desc>
        <p>Returns the 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>Node</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 due to the link, an exit signal with exit
          reason <c>noconnection</c> will be received). Otherwise works
          like <seealso marker="#spawn/3">spawn/3</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 pid of a new process started by the application
          of <c><anno>Fun</anno></c> to the empty list [] and reference for a monitor
          created to the new process.
          Otherwise works like
          <seealso marker="#spawn/3">spawn/3</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>, and the process is
          monitored at the same time. Returns the pid and a reference
          for the monitor.
          Otherwise works like
          <seealso marker="#spawn/3">spawn/3</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="spawn_opt" arity="2"/>
      <type name="priority_level" />
      <fsummary>Create a new process with a fun as entry point</fsummary>
      <desc>
        <p>Returns the 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">spawn_opt/4</seealso>.</p>
        <p>If the option <c>monitor</c> is given, the newly created
          process will be monitored and both the pid and reference for
          the monitor will be returned.</p>
      </desc>
    </func>
    <func>
      <name name="spawn_opt" arity="3"/>
      <type name="priority_level" />
      <fsummary>Create a new process with a fun as entry point on a given node</fsummary>
      <desc>
        <p>Returns the 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">spawn_opt/4</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="spawn_opt" arity="4"/>
      <type name="priority_level" />
      <fsummary>Create a new process with a function as entry point</fsummary>
      <desc>
        <p>Works exactly like
          <seealso marker="#spawn/3">spawn/3</seealso>, except that an
          extra option list is given when creating the process.</p>
        <p>If the option <c>monitor</c> is given, the newly created
          process will be monitored and both the pid and reference for
          the monitor will be returned.</p>
        <taglist>
          <tag><c>link</c></tag>
          <item>
            <p>Sets a link to the parent process (like
              <c>spawn_link/3</c> does).</p>
          </item>
          <tag><c>monitor</c></tag>
          <item>
            <p>Monitor the new process (just like
              <seealso marker="#monitor/2">monitor/2</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">process_flag(priority, <anno>Level</anno>)</seealso> in the start function of the new process,
              except that the priority will be set before the process is
              selected for execution for the first time. For more information
              on priorities see
              <seealso marker="#process_flag_priority">process_flag(priority, Level)</seealso>.</p>
          </item>
          <tag><c>{fullsweep_after, <anno>Number</anno>}</c></tag>
          <item>
            <p>This option is only useful for performance tuning.
              In general, you should not use this option unless you
              know that there is problem with execution times and/or
              memory consumption, and you should measure to make sure
              that the option improved 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 will be done.</p>
            <p>The <c>fullsweep_after</c> option makes it possible to
              specify the maximum number of generational collections
              before forcing a fullsweep even if there is still room on
              the old heap. Setting the number to zero effectively
              disables the general collection algorithm, meaning that
              all live data is copied at every garbage collection.</p>
            <p>Here are a few cases when it could be useful to change
              <c>fullsweep_after</c>. Firstly, if binaries that are no
              longer used should be thrown away as soon as possible.
              (Set <c><anno>Number</anno></c> to zero.) Secondly, a process that
              mostly have short-lived data will be fullsweeped seldom
              or never, meaning that the old heap will contain mostly
              garbage. To ensure a fullsweep once in a while, set
              <c><anno>Number</anno></c> to a suitable value such as 10 or 20.
              Thirdly, in embedded systems with limited amount of RAM
              and no virtual memory, one might want to preserve memory
              by setting <c><anno>Number</anno></c> to zero. (The value may be set
              globally, see
              <seealso marker="#system_flag/2">erlang:system_flag/2</seealso>.)</p>
          </item>
          <tag><c>{min_heap_size, <anno>Size</anno>}</c></tag>
          <item>
            <p>This option is only useful for performance tuning.
              In general, you should not use this option unless you
              know that there is problem with execution times and/or
              memory consumption, and you should measure to make sure
              that the option improved matters.
              </p>
            <p>Gives a minimum heap size in words. Setting this value
              higher than the system default might speed up some
              processes because less garbage collection is done.
              Setting too high value, however, might waste memory and
              slow down the system due to worse data locality.
              Therefore, it is recommended to 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>This option is only useful for performance tuning.
              In general, you should not use this option unless you
              know that there is problem with execution times and/or
              memory consumption, and you should measure to make sure
              that the option improved matters.
              </p>
	      <p>Gives a minimum binary virtual heap size in words. Setting this value
              higher than the system default might speed up some
              processes because less garbage collection is done.
              Setting too high value, however, might waste memory.
              Therefore, it is recommended to 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>

        </taglist>
      </desc>
    </func>
    <func>
      <name name="spawn_opt" arity="5"/>
      <type name="priority_level" />
      <fsummary>Create a new process with a function as entry point on a given node</fsummary>
      <desc>
        <p>Returns the 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>Node</c>. If
          <c><anno>Node</anno></c> does not exist, a useless pid is returned.
          Otherwise works like
          <seealso marker="#spawn_opt/4">spawn_opt/4</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="split_binary" arity="2"/>
      <type_desc variable="Pos">0..byte_size(Bin)</type_desc>
      <fsummary>Split a binary into two</fsummary>
      <desc>
        <p>Returns a tuple containing the binaries which 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 will be three binaries altogether.</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"/>
      <type_desc variable="Time">0 &lt;= Time &lt;= 4294967295</type_desc>
      <fsummary>Start a timer</fsummary>
      <desc>
        <p>Starts a timer which will send the message
          <c>{timeout, <anno>TimerRef</anno>, <anno>Msg</anno>}</c> to <c><anno>Dest</anno></c>
          after <c><anno>Time</anno></c> milliseconds.</p>
	<p>If <c><anno>Dest</anno></c> is a <c>pid()</c> it has to be a <c>pid()</c> of a local process, dead or alive.</p>
	<p>The <c><anno>Time</anno></c> value can, in the current implementation, not be greater than 4294967295.</p>
        <p>If <c><anno>Dest</anno></c> is an <c>atom()</c>, it is supposed to be the name of
          a registered process. The process referred to by the name is
          looked up at the time of delivery. No error is given if
          the name does not refer to a process.</p>
        <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will be automatically
          canceled if the process referred to by the <c>pid()</c> is not alive,
          or when the process exits. This feature was introduced in
          erts version 5.4.11. Note that timers will not be
          automatically canceled when <c><anno>Dest</anno></c> is an <c>atom()</c>.</p>
        <p>See also
          <seealso marker="#send_after/3">erlang:send_after/3</seealso>,
          <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>,
          and
          <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p>
        <p>Failure: <c>badarg</c> if the arguments does not satisfy
          the requirements specified above.</p>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="1"/>
      <fsummary>Information about context switches</fsummary>
      <desc>
        <p><c><anno>ContextSwitches</anno></c> is the total number of context
          switches since the system started.</p>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="2"/>
      <fsummary>Information about exact reductions</fsummary>
      <desc>
        <marker id="statistics_exact_reductions"></marker>
			<note><p><c>statistics(exact_reductions)</c> is
					a more expensive operation than
					<seealso marker="#statistics_reductions">statistics(reductions)</seealso>
					especially on an Erlang machine with SMP support.</p>
			</note>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="3"/>
      <fsummary>Information about garbage collection</fsummary>
      <desc>
        <p>This information may not be valid for all implementations.</p>
	  <pre>
> <input>statistics(garbage_collection).</input>
{85,23961,0}
</pre>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="4"/>
      <fsummary>Information about io</fsummary>
      <desc>
        <p><c><anno>Input</anno></c> is the total number of bytes received
          through ports, and <c><anno>Output</anno></c> is the total number of
          bytes output to ports.</p>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="5"/>
      <fsummary>Information about reductions</fsummary>
      <desc>
        <marker id="statistics_reductions"></marker>
			<note>
				<p>Since erts-5.5 (OTP release 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">statistics(exact_reductions)</seealso>.</p>
			</note>
        <pre>
> <input>statistics(reductions).</input>
{2046,11}
</pre>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="6"/>
      <fsummary>Information about the run-queue</fsummary>
      <desc>
        <p>Returns the length of the run queue, that is, the number
          of processes that are ready to run.</p>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="7"/>
      <fsummary>Information about run-time</fsummary>
      <desc>
        <p>Note that the run-time is the sum of the run-time for all
        threads in the Erlang run-time system and may therefore be greater
        than the wall-clock time.</p>
        <pre>
> <input>statistics(runtime).</input>
{1690,1620}
</pre>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="8"/>
      <fsummary>Information about each schedulers work time</fsummary>
      <desc>
		  <marker id="statistics_scheduler_wall_time"></marker>
		  <p>
			  Returns a list of tuples with <c>{<anno>SchedulerId</anno>,
				  <anno>ActiveTime</anno>, <anno>TotalTime</anno>}</c>, where
			  <c>SchedulerId</c> is an integer id of the scheduler, <c>ActiveTime</c> is
			  the duration the scheduler has been busy, <c>TotalTime</c> is the total time duration since
			  <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso>
			  activation. The time unit is not defined and may be subject to change
			  between releases, operating systems and system restarts.
			  <c>scheduler_wall_time</c> should only be used to calculate relative
			  values for scheduler-utilization. <c>ActiveTime</c> can never exceed <c>TotalTime</c>.
		  </p>

		  <p>The definition of a busy scheduler is when it is not idle or not
			  scheduling (selecting) a process or port, meaning; executing process
			  code, executing linked-in-driver or NIF code, executing
			  built-in-functions or any other runtime handling, garbage collecting
			  or handling any other memory management. Note, a scheduler may also be
			  busy even if the operating system has scheduled out the scheduler
			  thread.
		  </p>

		  <p>
			  Returns <c>undefined</c> if the system flag
			  <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso>
			  is turned off.
		  </p>

		  <p>The list of scheduler information is unsorted and may appear in different order
			  between calls.
		  </p>
		  <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 we will take another snapshot and calculate scheduler-utilization per scheduler.</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)), A/T.</input>
0.9769136803764825
</pre>
        <note>
          <p><c>scheduler_wall_time</c> is by default disabled. Use <c>erlang:system_flag(scheduler_wall_time, true)</c> to enable it. </p>
        </note>
      </desc>
    </func>
    <func>
      <name name="statistics" arity="1" clause_i="9"/>
      <fsummary>Information about wall-clock</fsummary>
      <desc>
        <p><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="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 isn't
	already in the suspended state. A suspended process will not be
	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 will not leave the suspended state until its suspend 
	count reach zero. The suspend count of <c><anno>Suspendee</anno></c>
	is decreased when
	<seealso marker="#resume_process/1">erlang:resume_process(<anno>Suspendee</anno>)</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 will automatically be
	decreased when the process terminates.</p>

	<p>Currently the following options (<c><anno>Opt</anno></c>s) are available:</p>
        <taglist>
          <tag><c>asynchronous</c></tag>
          <item>
	  A suspend request is sent to the process identified by
	  <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c> will eventually suspend
	  unless it is resumed before it was able to suspend. The caller
	  of <c>erlang:suspend_process/2</c> will return immediately,
	  regardless of whether the <c><anno>Suspendee</anno></c> has suspended yet
	  or not. Note that the point in time when the <c><anno>Suspendee</anno></c>
	  will actually suspend cannot be deduced from other events
	  in the system. The only guarantee given is that the
	  <c><anno>Suspendee</anno></c> will <em>eventually</em> suspend (unless it
	  is resumed). If the <c>asynchronous</c> option has <em>not</em>
	  been passed, the caller of <c>erlang:suspend_process/2</c> will
	  be blocked until the <c><anno>Suspendee</anno></c> has actually suspended.
	  </item>
          <tag><c>unless_suspending</c></tag>
          <item>
	  The process identified by <c><anno>Suspendee</anno></c> will be suspended
	  unless the calling process already is suspending the
	  <c><anno>Suspendee</anno></c>. If <c>unless_suspending</c> is combined
	  with the <c>asynchronous</c> option, a suspend request will be
	  sent unless the calling process already is suspending the
	  <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
	  the <c><anno>Suspendee</anno></c>, or if combined with the <c>asynchronous</c>
	  option and a send request already is in transit,
	  <c>false</c> is returned and the suspend count on <c><anno>Suspendee</anno></c>
	  will remain unchanged.
	  </item>
        </taglist>

	<p>If the suspend count on the process identified by
	<c><anno>Suspendee</anno></c> was increased, <c>true</c> is returned; otherwise,
	<c>false</c> is returned.</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> isn't a process identifier.
	  </item>
          <tag><c>badarg</c></tag>
          <item>
	  If the process identified by <c><anno>Suspendee</anno></c> is same the 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> isn't 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 current system limit
	  is larger than 2 000 000 000 suspends, and it will never be less
	  than that.
	  </item>
        </taglist>
      </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">erlang:suspend_process(<anno>Suspendee</anno>, [])</seealso>. For more information see the documentation of <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso>.
	</p>
        <warning>
          <p>This BIF is intended for debugging only.</p>
        </warning>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="1"/>
      <fsummary>Set system flag backtrace_depth</fsummary>
      <desc>
        <p>Sets the maximum depth of call stack back-traces in the
          exit reason element of <c>'EXIT'</c> tuples.</p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="2"/>
      <type name="cpu_topology"/>
      <type name="level_entry"/>
      <type name="level_tag"/>
      <type name="sub_level"/>
      <type name="info_list"/>
      <fsummary>Set system flag cpu_topology</fsummary>
      <desc>
        <warning>
          <p><marker id="system_flag_cpu_topology"></marker>
          This argument is <em>deprecated</em> and
          scheduled for removal in erts-5.10/OTP-R16. Instead of using
          this argument you are advised to use the <c>erl</c> command
          line argument <seealso marker="erts:erl#+sct">+sct</seealso>.
          When this argument has been removed a final CPU topology to use
          will be determined at emulator boot time.</p>
        </warning>
        <p>Sets the user defined <c><anno>CpuTopology</anno></c>. The user defined
           CPU topology will override any automatically detected
           CPU topology. By passing <c>undefined</c> as <c><anno>CpuTopology</anno></c>
           the system will revert back 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 will be sent a request
           to rebind according to the new CPU topology.
        </p>
        <p>The user defined CPU topology can also be set by passing
           the <seealso marker="erts:erl#+sct">+sct</seealso> command
           line argument to <c>erl</c>.
        </p>
        <p>For information on the <c><anno>CpuTopology</anno></c> type
           and more, see the documentation of
           <seealso marker="#system_info_cpu_topology">erlang:system_info(cpu_topology)</seealso>,
           and the <c>erl</c> <seealso marker="erts:erl#+sct">+sct</seealso>
           and <seealso marker="erts:erl#+sbt">+sbt</seealso>
           command line flags.
        </p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="3"/>
      <fsummary>Set system flag fullsweep_after</fsummary>
      <desc>
        <p><c><anno>Number</anno></c> is a non-negative integer which indicates
          how many times generational garbage collections can be
          done without forcing a fullsweep collection. The value
          applies to new processes; 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 0 can help to conserve
          memory.</p>
        <p>An alternative way to set this value is through the
          (operating system) environment variable
          <c>ERL_FULLSWEEP_AFTER</c>.</p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="4"/>
      <fsummary>Set system flag min_heap_size</fsummary>
      <desc>
        <p>Sets the default minimum heap size for processes. The
          size is given in words. The new <c>min_heap_size</c> only
          effects processes spawned after the change of
          <c>min_heap_size</c> has been made.
          The <c>min_heap_size</c> can be set for individual
          processes by use of
          <seealso marker="#spawn_opt/4">spawn_opt/N</seealso> or
          <seealso marker="#process_flag/2">process_flag/2</seealso>. </p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="5"/>
      <fsummary>Set system flag min_bin_vheap_size</fsummary>
      <desc>
        <p>Sets the default minimum binary virtual heap size for processes. The
          size is given in words. The new <c>min_bin_vhheap_size</c> only
          effects processes spawned after the change of
          <c>min_bin_vhheap_size</c> has been made.
          The <c>min_bin_vheap_size</c> can be set for individual
          processes by use of
          <seealso marker="#spawn_opt/4">spawn_opt/N</seealso> or
          <seealso marker="#process_flag/2">process_flag/2</seealso>. </p>
        <p>Returns the old value of the flag.</p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="6"/>
      <fsummary>Set system flag multi_scheduling</fsummary>
      <desc>
        <p><marker id="system_flag_multi_scheduling"></marker>
          If multi-scheduling is enabled, more than one scheduler
          thread is used by the emulator. Multi-scheduling can be
          blocked. When multi-scheduling has been blocked, only
          one scheduler thread will schedule Erlang processes.</p>
        <p>If <c><anno>BlockState</anno> =:= block</c>, multi-scheduling will
          be blocked. If <c><anno>BlockState</anno> =:= unblock</c> and no-one
          else is blocking multi-scheduling and this process has
          only blocked one time, multi-scheduling will be unblocked.
          One process can block multi-scheduling multiple times.
          If a process has blocked multiple times, it has to
          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 exits, it will release its
          blocking of multi-scheduling.</p>
        <p>The return values are <c>disabled</c>, <c>blocked</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. The return values are described in the
          documentation of <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>.</p>
        <p><em>NOTE</em>: Blocking of multi-scheduling should normally
          not be needed. If you feel that you need to
          block multi-scheduling, think through the
          problem at least a couple of times again.
          Blocking multi-scheduling should only be used
          as a last resort since it will most likely be
          a <em>very inefficient</em> way to solve the
          problem.</p>
        <p>See also <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>,
          <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>, and
          <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="7"/>
      <type name="scheduler_bind_type"/>
      <fsummary>Set system flag scheduler_bind_type</fsummary>
      <desc>
        <warning>
          <p><marker id="system_flag_scheduler_bind_type"></marker>
          This argument is <em>deprecated</em> and
          scheduled for removal in erts-5.10/OTP-R16. Instead of using
          this argument you are advised to use the <c>erl</c> command
          line argument <seealso marker="erts:erl#+sbt">+sbt</seealso>.
          When this argument has been removed a final scheduler bind type
          to use will be 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 which causes them to try to bind or unbind as requested.
           <em>NOTE:</em> If a scheduler fails to bind, this
           will often be silently ignored. This since it isn't always
           possible to verify valid logical processor identifiers. If
           an error is reported, it will be reported to the
           <c>error_logger</c>. If you want to verify that the
           schedulers actually have bound as requested, call
           <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.
        </p>
        <p>Schedulers can currently only be bound on newer Linux,
           Solaris, FreeBSD, and Windows systems, but more systems will be
           supported in the future.
        </p>
        <p>In order for the runtime system to be able to bind schedulers,
           the CPU topology needs to be known. If the runtime system fails
           to automatically detect the CPU topology, it can be defined.
           For more information on how to define the CPU topology, see
           the <c>erl</c> <seealso marker="erts:erl#+sct">+sct</seealso> command
           line flag.
        </p>
        <p>The runtime system will by default <em>not</em> bind schedulers
           to logical processors.
        </p>
        <p><em>NOTE:</em> If the Erlang runtime system is the only
           operating system process that binds threads to logical processors,
           this improves the performance of the runtime system. However,
           if other operating system processes (as for example another Erlang
           runtime system) also bind threads to logical processors, there
           might be a performance penalty instead. In some cases this
           performance penalty might be severe. If this is the case, you
           are advised to not bind the schedulers.</p>
        <p>Schedulers can be bound in different ways. The <c><anno>How</anno></c>
           argument determines how schedulers are bound. <c><anno>How</anno></c> can
           currently be one of:</p>
        <taglist>
          <tag><c>unbound</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt u</seealso>.
          </p></item>
          <tag><c>no_spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt ns</seealso>.
          </p></item>
          <tag><c>thread_spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt ts</seealso>.
          </p></item>
          <tag><c>processor_spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt ps</seealso>.
          </p></item>
          <tag><c>spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt s</seealso>.
          </p></item>
          <tag><c>no_node_thread_spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt nnts</seealso>.
          </p></item>
          <tag><c>no_node_processor_spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt nnps</seealso>.
          </p></item>
          <tag><c>thread_no_node_processor_spread</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt tnnps</seealso>.
          </p></item>
          <tag><c>default_bind</c></tag>
          <item><p>Same as the <c>erl</c> command line argument
          <seealso marker="erts:erl#+sbt">+sbt db</seealso>.
          </p></item>
        </taglist>
        <p>The value returned equals <c><anno>How</anno></c> before the
           <c>scheduler_bind_type</c> flag was changed.</p>
        <p>Failure:</p>
        <taglist>
          <tag><c>notsup</c></tag>
          <item>
            <p>If binding of schedulers is not supported.</p>
          </item>
          <tag><c>badarg</c></tag>
          <item>
            <p>If <c>How</c> isn't one of the documented alternatives.</p>
          </item>
          <tag><c>badarg</c></tag>
          <item>
            <p>If no CPU topology information is available.</p>
          </item>
        </taglist>
        <p>The scheduler bind type can also be set by passing
           the <seealso marker="erts:erl#+sbt">+sbt</seealso> command
           line argument to <c>erl</c>.
        </p>
        <p>For more information, see
           <seealso marker="#system_info_scheduler_bind_type">erlang:system_info(scheduler_bind_type)</seealso>,
           <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>,
           the <c>erl</c> <seealso marker="erts:erl#+sbt">+sbt</seealso>
           and <seealso marker="erts:erl#+sct">+sct</seealso> command line
           flags.
        </p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="8"/>
      <fsummary>Set system flag scheduler_wall_time</fsummary>
      <desc><p><marker id="system_flag_scheduler_wall_time"></marker>
      Turns on/off scheduler wall time measurements. </p>
      <p>For more information see,
      <seealso marker="#statistics_scheduler_wall_time">erlang:statistics(scheduler_wall_time)</seealso>.
      </p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="9"/>
      <fsummary>Set system flag schedulers_online</fsummary>
      <desc>
        <p><marker id="system_flag_schedulers_online"></marker>
        Sets the amount of schedulers online. Valid range is
        <![CDATA[1 <= SchedulersOnline <= erlang:system_info(schedulers)]]>.
        </p>
        <p>Returns the old value of the flag.</p>
        <p>For more information see,
        <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>,
        and
        <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>.
        </p>
      </desc>
    </func>
    <func>
      <name name="system_flag" arity="2" clause_i="10"/>
      <fsummary>Set system flag trace_control_word</fsummary>
      <desc>
        <p>Sets the value of the node's trace control word to
          <c><anno>TCW</anno></c>. <c><anno>TCW</anno></c> should be an unsigned integer. For
          more information see documentation of the
          <seealso marker="erts:match_spec#set_tcw">set_tcw</seealso>
          function in the match specification documentation in the
          ERTS User's Guide.</p>
        <p>Returns the old value of the flag.</p>
      </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"/>
      <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"/>
      <fsummary>Information about the allocators of the system</fsummary>
      <desc>
        <p>
          Returns various information about the
          <marker id="system_info_allocator_tags">allocators</marker> of the
          current system (emulator) as specified by
          <c><anno>Item</anno></c>:</p>
        <taglist>
          <tag><marker id="system_info_allocated_areas"><c>allocated_areas</c></marker></tag>
          <item>
            <p>Returns a list of tuples with information about
              miscellaneous allocated memory areas.</p>
            <p>Each tuple contains an atom describing type of memory as
              first element and amount of allocated memory in bytes as
              second element. In those cases when there is information
              present about allocated and used memory, a third element
              is present. This third element contains 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 will therefore
              change when needed without prior notice.</p>
            <p><em>Note:</em> 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. If you are interested
              in the total amount of memory allocated by the emulator
              see <seealso marker="#memory/0">erlang:memory/0,1</seealso>.</p>
          </item>
          <tag><marker id="system_info_allocator"><c>allocator</c></marker></tag>
          <item>
            <p>Returns <c>{<anno>Allocator</anno>, <anno>Version</anno>, <anno>Features</anno>, <anno>Settings</anno>}.</c></p>
            <p>Explanation:</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 could not be identified. Currently
                  <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
                  allocation features used.</p>
              </item>
              <item>
                <p><c><anno>Settings</anno></c> is a list of subsystems, their
                  configurable parameters, and used values. Settings
                  may 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">erts_alloc(3)</seealso>.</p>
          </item>
          <tag><marker id="system_info_alloc_util_allocators"><c>alloc_util_allocators</c></marker></tag>
          <item>
	     <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 the
	        <seealso marker="erts:erts_alloc#alloc_util">"the
		alloc_util framework" section in the
		erts_alloc(3)</seealso> documentation.
	     </p>
          </item>
          <tag><marker id="system_info_allocator_tuple"><c>{allocator, <anno>Alloc</anno>}</c></marker></tag>
          <item>
            <p>Returns information about the specified allocator.
	       As of erts version 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><em>Note:</em> The information returned is highly
              implementation dependent and may be changed, or removed
              at any time without prior notice. It was initially
              intended as a tool when developing new allocators, but
              since it might be of interest for others it has been
              briefly documented.</p>
            <p>The recognized allocators are listed in
              <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso>.
              After reading the <c>erts_alloc(3)</c> documentation,
	      the returned information
              should more or less speak 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> are
              abbreviations for, respectively, multi-block carriers, and
              single-block carriers. Sizes are presented in bytes. When
              it is not a size that is presented, it is the amount of
              something. Sizes and amounts are often presented by three
              values, the first is current value, the second is maximum
              value since the last call to
              <c>erlang:system_info({allocator, Alloc})</c>, and
              the third is maximum value since the emulator was started.
              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 memory pool size and
              the second value used memory size.</p>
          </item>
          <tag><marker id="system_info_allocator_sizes"><c>{allocator_sizes, <anno>Alloc</anno>}</c></marker></tag>
          <item>
	    <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">erlang:system_info({allocator, <anno>Alloc</anno>})</seealso>.
	    </p>
          </item>
        </taglist>
      </desc>
    </func>
    <func>
      <name name="system_info" arity="1" clause_i="10"/>
      <name name="system_info" arity="1" clause_i="11"/>
      <type name="cpu_topology"/>
      <type name="level_entry"/>
      <type_desc name="cpu_topology">
        <marker id="system_info_cpu_topology"></marker>
        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 may co-exist.
      </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 may be introduced in the future.
      </type_desc>
      <type name="sub_level"/>
      <type name="info_list"/>
      <type_desc name="info_list">
        The <c>info_list()</c> may be extended in the future.
      </type_desc>
      <fsummary>Information about the CPU topology of the system</fsummary>
      <desc>
        <p>Returns various information about the
          <marker id="system_info_cpu_topology_tags">CPU topology</marker>
          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> which currently is 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 NUMA (non-uniform memory access)
	       nodes, and <c>thread</c> refers to hardware threads
	       (e.g. Intels hyper-threads).</p>
            <p>A level in the <c><anno>CpuTopology</anno></c> term can be omitted if
	       only one entry exists and the <c><anno>InfoList</anno></c> is empty.
	    </p>
	    <p><c>thread</c> can only be a sub level to <c>core</c>.
	       <c>core</c> can be a sub level to either <c>processor</c>
	       or <c>node</c>.  <c>processor</c> can either be on the
	       top level or a sub level to <c>node</c>. <c>node</c>
	       can either be on the top level or a sub level 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 one
	       and only one NUMA node. Cache hierarchy is not part of
	       the <c><anno>CpuTopology</anno></c> type yet, but will be in the
	       future. Other things may also make it into the CPU
	       topology in the future. In other words, expect the
	       <c><anno>CpuTopology</anno></c> type to change.
	    </p>
          </item>
          <tag><marker id="system_info_cpu_topology_defined"><c>{cpu_topology, defined}</c></marker></tag>
          <item>
            <p>Returns the user defined <c><anno>CpuTopology</anno></c>. For more
	       information see the documentation of
	       the <c>erl</c> <seealso marker="erts:erl#+sct">+sct</seealso> command
	       line flag, and the documentation of the
	       <seealso marker="#system_info_cpu_topology">cpu_topology</seealso>
	       argument.
	    </p>
          </item>
          <tag><marker id="system_info_cpu_topology_detected"><c>{cpu_topology, detected}</c></marker></tag>
          <item>
            <p>Returns the automatically detected <c><anno>CpuTopology</anno></c>. The
	       emulator currently only 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 the documentation of the
	       <seealso marker="#system_info_cpu_topology">cpu_topology</seealso>
	       argument.
	    </p>
          </item>
          <tag><c>{cpu_topology, used}</c></tag>
          <item>
            <p>Returns the <c><anno>CpuTopology</anno></c> which is used by the
	       emulator. For more information see the 
               documentation of the
	       <seealso marker="#system_info_cpu_topology">cpu_topology</seealso>
	       argument.
	    </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="12"/>
      <name name="system_info" arity="1" clause_i="13"/>
      <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="29"/>
      <name name="system_info" arity="1" clause_i="30"/>
      <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="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"/>
      <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"/>
      <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>allocated_areas</c>, <c>allocator</c>,
            <c>alloc_util_allocators</c>, <c>allocator_sizes</c></tag>
          <item>
            <p>See <seealso marker="#system_info_allocator_tags">above</seealso>.</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
	       may be added and/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
              regarding the emulators internal I/O checking. Note,
              the content of the returned list may vary between
              platforms and over time. The only thing guaranteed is
              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 which the current emulator has been
              set to be backward compatible with. The compatibility
              mode can be configured at startup by using the command
              line flag <c>+R</c>, see
              <seealso marker="erts:erl#compat_rel">erl(1)</seealso>.</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. Currently valid
              creations are integers in the range 1..3, but this may
              (probably will) change in the future. If the node is not
              alive, 0 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>dist</c></tag>
          <item>
            <p>Returns a binary containing a string of distribution
              information formatted as in Erlang crash dumps. For more
              information see the <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso>
              chapter in the ERTS User's Guide.</p>
          </item>
          <tag><c>dist_ctrl</c></tag>
          <item>
            <p>Returns a list of tuples
              <c>{Node, ControllingEntity}</c>, one entry for each
              connected remote node. The <c><anno>Node</anno></c> is the name of the
              node and the <c><anno>ControllingEntity</anno></c> is the port or pid
              responsible for the communication to that node. More
              specifically, the <c><anno>ControllingEntity</anno></c> for nodes
              connected via TCP/IP (the normal case) is the socket
              actually 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 will be on 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 currently be either
            <c>dtrace</c>, <c>systemtap</c> or <c>none</c>. For a
            commercial or standard build, this is always <c>none</c>,
            the other return values indicate a custom configuration
            (e.g. <c>./configure --with-dynamic-trace=dtrace</c>). See
            the <seealso marker="runtime_tools:dyntrace">dyntrace
            </seealso> manual page and the
            <c>README.dtrace</c>/<c>README.systemtap</c> files in the
            Erlang source code top directory for more information
            about dynamic tracing.</p>
          </item>
          <tag><c>dynamic_trace_probes</c></tag>
          <item>
            <p>Returns a <c>boolean()</c> indicating if dynamic trace probes
            (either dtrace or systemtap) are built into the
            emulator. This can only be <c>true</c> if the virtual
            machine was built for dynamic tracing
            (i.e. <c>system_info(dynamic_trace)</c> returns
            <c>dtrace</c> or <c>systemtap</c>).</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> since
	      the elib_malloc allocator has been removed.</p>
          </item>
          <tag><marker id="system_info_dist_buf_busy_limit"><c>dist_buf_busy_limit</c></marker></tag>
          <item>
            <p>Returns the value of the distribution buffer busy limit
	    in bytes. This limit can be set on startup by passing the
	    <seealso marker="erts:erl#+zdbbl">+zdbbl</seealso> command line
	    flag to <c>erl</c>.</p>
          </item>
          <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> will use these
              garbage collection settings. The default settings can be
              changed by use of
              <seealso marker="#system_flag/2">system_flag/2</seealso>.
              <seealso marker="#spawn_opt/4">spawn_opt/4</seealso>
              can spawn a process that does not use the default
              settings.</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.
              Currently only the following heap type exists:</p>
            <taglist>
              <tag><c>private</c></tag>
              <item>
                <p>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.</p>
              </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 the
              <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> chapter in the ERTS
              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 the <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> chapter
              in the ERTS User's Guide.</p>
          </item>
	  <tag><marker id="logical_processors"><c>logical_processors</c></marker></tag>
          <item>
            <p>Returns the detected number of logical processors configured
	       on the system. The return value is either an integer, or
	       the atom <c>unknown</c> if the emulator wasn't able to
	       detect logical processors configured.
	    </p>
          </item>
	  <tag><marker id="logical_processors_available"><c>logical_processors_available</c></marker></tag>
          <item>
            <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 wasn't
	       able to detect logical processors available. The number
	       of logical processors available is less than or equal to
	       the number of <seealso marker="#logical_processors_online">logical
	       processors online</seealso>.
	    </p>
          </item>
	  <tag><marker id="logical_processors_online"><c>logical_processors_online</c></marker></tag>
          <item>
            <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 wasn't able to
	       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>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>
          <tag><c>modified_timing_level</c></tag>
          <item>
            <p>Returns the modified timing level (an integer) if
              modified timing has been enabled; otherwise,
              <c>undefined</c>. See the <c>+T</c> command line flag
              in the documentation of the
              <seealso marker="erts:erl#+T">erl(1)</seealso>
              command for more information on modified timing.</p>
          </item>
          <tag><marker id="system_info_multi_scheduling"><c>multi_scheduling</c></marker></tag>
          <item>
            <p>Returns <c>disabled</c>, <c>blocked</c>, or <c>enabled</c>.
              A description of the return values:</p>
            <taglist>
              <tag><c>disabled</c></tag>
              <item>
                <p>The emulator has only one scheduler thread. The
                  emulator does not have SMP support, or have 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 but one have been blocked,
                  i.e., only one scheduler thread will schedule
                  Erlang processes and execute Erlang code.</p>
              </item>
              <tag><c>enabled</c></tag>
              <item>
                <p>The emulator has more than one scheduler thread,
                  and no scheduler threads have been blocked, i.e.,
                  all available scheduler threads will schedule
                  Erlang processes and execute Erlang code.</p>
              </item>
            </taglist>
            <p>See also <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>,
              <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>, and
              <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p>
          </item>
          <tag><marker id="system_info_multi_scheduling_blockers"><c>multi_scheduling_blockers</c></marker></tag>
          <item>
            <p>Returns a list of <c><anno>PID</anno></c>s when multi-scheduling
              is blocked; otherwise, the empty list. The <c><anno>PID</anno></c>s
              in the list is <c><anno>PID</anno></c>s of the processes currently
              blocking multi-scheduling. A <c><anno>PID</anno></c> will only be
              present once in the list, even if the corresponding
              process has blocked multiple times.</p>
            <p>See also <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>,
              <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, and
              <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p>
          </item>
          <tag><marker id="system_info_otp_release"><c>otp_release</c></marker></tag>
          <item>
            <p>Returns a string containing the OTP release number.</p>
          </item>
	  <tag><marker id="system_info_port_parallelism"><c>port_parallelism</c></marker></tag>
	  <item><p>Returns the default port parallelism scheduling hint used.
	  For more information see the
	  <seealso marker="erl#+spp">+spp</seealso> command line argument
	  of <seealso marker="erl">erl(1)</seealso>.</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 as an integer. The same value as
              <c>length(erlang:ports())</c> returns, but more efficient.</p>
          </item>
          <tag><marker id="system_info_port_limit"><c>port_limit</c></marker></tag>
          <item>
            <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 the
              <seealso marker="erl#+Q">+Q</seealso>
	      command line flag of
	      <seealso marker="erl">erl(1)</seealso>.</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 as an integer. The same value as
              <c>length(processes())</c> returns, but more efficient.</p>
          </item>
          <tag><marker id="system_info_process_limit"><c>process_limit</c></marker></tag>
          <item>
            <p>Returns the maximum number of simultaneously existing
              processes at the local node as an integer. This limit
              can be configured at startup by using the
              <seealso marker="erl#+P">+P</seealso>
	      command line flag of
	      <seealso marker="erl">erl(1)</seealso>.</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 the <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> chapter
              in the ERTS User's Guide.</p>
          </item>
          <tag><marker id="system_info_scheduler_bind_type"><c>scheduler_bind_type</c></marker></tag>
          <item>
	    <p>Returns information on how user has requested
	       schedulers to be bound or not bound.</p>
	    <p><em>NOTE:</em> Even though user has requested
	       schedulers to be bound, they might have silently failed
	       to bind. In order to inspect actual scheduler bindings call
	       <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.
	    </p>
	    <p>For more information, see
	       the <c>erl</c> <seealso marker="erts:erl#+sbt">+sbt</seealso>
	       command line argument, and
	       <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.
	    </p>
          </item>
          <tag><marker id="system_info_scheduler_bindings"><c>scheduler_bindings</c></marker></tag>
          <item>
	    <p>Returns information on currently used scheduler
	       bindings.</p>
	    <p>A tuple of a size equal to
	       <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso> is returned. The elements of the tuple 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>. E.g., if the schedulers have been bound,
	       <c>element(erlang:system_info(scheduler_id),
	       erlang:system_info(scheduler_bindings))</c> will return
	       the identifier of the logical processor that the calling
	       process is executing on.
	    </p>
	    <p>Note that only schedulers online can be bound to logical
	       processors.</p>
	    <p>For more information, see
	       the <c>erl</c> <seealso marker="erts:erl#+sbt">+sbt</seealso>
	       command line argument,
	       <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>.
	    </p>
          </item>
          <tag><marker id="system_info_scheduler_id"><c>scheduler_id</c></marker></tag>
          <item>
            <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>. See also
              <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p>
          </item>
          <tag><marker id="system_info_schedulers"><c>schedulers</c></marker></tag>
          <item>
            <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 after
              that. The amount of schedulers online can
	      however be changed at any time.</p>
            <p>See also <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>,
	      <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>,
	      <seealso marker="#system_info_scheduler_id">erlang:system_info(scheduler_id)</seealso>,
              <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>,
              <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, and
              and <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>.</p>
          </item>
          <tag><marker id="system_info_schedulers_online"><c>schedulers_online</c></marker></tag>
          <item>
            <p>Returns the amount of schedulers online. The scheduler
	    identifiers of schedulers online satisfy the following
	    relationship:
	    <c><![CDATA[1 <= SchedulerId <= erlang:system_info(schedulers_online)]]></c>.
	    </p>
	    <p>For more information, see
	    <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>,
	    and
	    <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>.
	    </p>      <name name="system_info" arity="1" clause_i="49"/>

          </item>
          <tag><c>smp_support</c></tag>
          <item>
            <p>Returns <c>true</c> if the emulator has been compiled
              with smp support; otherwise, <c>false</c>.</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> if the emulator has been compiled
              with thread support; otherwise, <c>false</c> is
              returned.</p>
          </item>
          <tag><marker id="system_info_thread_pool_size"><c>thread_pool_size</c></marker></tag>
          <item>
            <p>Returns the number of async threads in the async thread
              pool used for asynchronous driver calls
              (<seealso marker="erts:erl_driver#driver_async">driver_async()</seealso>)
              as an integer.</p>
          </item>
          <tag><c>trace_control_word</c></tag>
          <item>
            <p>Returns the value of the node's trace control word.
              For more information see documentation of the function
              <c>get_tcw</c> in "Match Specifications in Erlang",
              <seealso marker="erts:match_spec#get_tcw">ERTS User's Guide</seealso>.</p>
          </item>
          <tag><marker id="update_cpu_info"><c>update_cpu_info</c></marker></tag>
          <item>
            <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 amount of logical processors
	       <seealso marker="#logical_processors">configured</seealso>,
	       <seealso marker="#logical_processors_online">online</seealso>, and
	       <seealso marker="#logical_processors_available">available</seealso>.
	       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> is returned. If the CPU information has changed
	       you probably want to
	       <seealso marker="#system_flag_schedulers_online">adjust the amount
	       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><marker id="system_info_version"><c>version</c></marker></tag>
          <item>
            <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, i.e. on a 32-bit architecture 4 is returned,
              and on a pure 64-bit architecture 8 is returned. On a
              halfword 64-bit emulator, 4 is returned, as the Erlang
              terms are stored using a virtual wordsize of half the
              system's wordsize.</p>
          </item>
          <tag><c>{wordsize, external}</c></tag>
          <item>
	    <p>Returns the true wordsize of the emulator, i.e. the size
	       of a pointer, in bytes as an integer. On a pure 32-bit
	       architecture 4 is returned, on both a halfword and pure
	       64-bit architecture, 8 is returned.</p>
          </item>
        </taglist>
        <note>
          <p>The <c>scheduler</c> argument has changed name to
            <c>scheduler_id</c>. This in order to avoid mixup with
            the <c>schedulers</c> argument. The <c>scheduler</c>
            argument was introduced in ERTS version 5.5 and renamed
            in ERTS version 5.5.1.</p>
        </note>
      </desc>
    </func>

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

    <func>
      <name name="system_monitor" arity="1"/>
      <type name="system_monitor_option"/>
      <fsummary>Set or clear system performance monitoring options</fsummary>
      <desc>
        <p>When called with the 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">erlang:system_monitor(<anno>MonitorPid</anno>, <anno>Options</anno>)</seealso>.</p>
        <p>Returns the previous system monitor settings just like
          <seealso marker="#system_monitor/0">erlang:system_monitor/0</seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="system_monitor" arity="2"/>
      <type name="system_monitor_option"/>
      <fsummary>Set system performance monitoring options</fsummary>
      <desc>
        <p>Sets system performance monitoring options. <c><anno>MonitorPid</anno></c>
          is a local pid that will receive system monitor messages, and
          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> wallclock 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 and <c>Info</c> is a list of two-element
              tuples describing the result of the garbage collection.
              One of the tuples is <c>{timeout, GcTime}</c> where
              <c>GcTime</c> is the actual 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 documentation of the
	      <seealso marker="#gc_start">gc_start</seealso>
	      trace message (see
	      <seealso marker="#trace/3">erlang:trace/3</seealso>).
	      New tuples may be added, and the order of the tuples in
	      the <c>Info</c> list may be changed at any time without prior
	      notice.
	      </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> above, except that
              the tuple tagged with <c>timeout</c> is not present.
	      <em>Note</em>: As of erts version 5.6 the monitor message
	      is sent if the sum of the sizes of all memory blocks allocated
	      for all heap generations is equal to or larger than <c>Size</c>.
	      Previously the monitor message was sent if the memory block
	      allocated for the youngest generation was equal to or larger
	      than <c>Size</c>.
	    </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">erlang:system_monitor/0</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 will enlarge the process's
            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>Failure: <c>badarg</c> if <c><anno>MonitorPid</anno></c> does not exist or is not a local process.</p>
      </desc>
    </func>

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

    <func>
      <name name="system_profile" arity="2"/>
      <type name="system_profile_option"/>
      <fsummary>Current system profiling settings</fsummary>
      <desc>
        <p>Sets system profiler options. <c><anno>ProfilerPid</anno></c>
          is a local pid or port that will receive 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 subsequently <c>active</c> when the port
	     callback returns.
          </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 is reinserted into the
	     run queue after having been preemptively scheduled out will 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>
        </taglist>
        <note><p><c>erlang:system_profile</c> is considered experimental and
        its behaviour may change in the future.</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 which is the result of encoding
          <c><anno>Term</anno></c> according to the Erlang external term format.</p>
        <p>This can be used for a variety of 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>
        <p>See also
          <seealso marker="#binary_to_term/1">binary_to_term/1</seealso>.</p>
      </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 which is the result of encoding
          <c><anno>Term</anno></c> according to the Erlang external term format.</p>
        <p>If the option <c>compressed</c> is provided, the external
          term format will be compressed. The compressed format is
          automatically recognized by <c>binary_to_term/1</c> in R7B and later.</p>
        <p>It is also possible to specify a compression level by giving
          the option <c>{compressed, <anno>Level</anno>}</c>, where <c><anno>Level</anno></c> is an
          integer from 0 through 9. <c>0</c> means that no compression
          will be done (it is the same as not giving any <c>compressed</c> option);
          <c>1</c> will take the least time but may not compress as well as
          the higher levels; <c>9</c> will take the most time and may produce
          a smaller result. Note the "mays" in the preceding sentence; depending
          on the input term, level 9 compression may or may not produce a smaller
          result than level 1 compression.</p>
        <p>Currently, <c>compressed</c> gives the same result as
          <c>{compressed, 6}</c>.</p>
        <p>The option <c>{minor_version, <anno>Version</anno>}</c> can be use to control
          some details of the encoding. This option was
          introduced in R11B-4. Currently, the allowed values for <c><anno>Version</anno></c>
          are <c>0</c> and <c>1</c>.</p>
        <p><c>{minor_version, 1}</c> 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). <c>binary_to_term/1</c>
          in R11B-4 and later is able decode the new representation.</p>
        <p><c>{minor_version, 0}</c> is currently the default, meaning that floats
          will be encoded using a textual representation; this option is useful if
          you want to ensure that releases prior to R11B-4 can decode resulting
          binary.</p>
        <p>See also
          <seealso marker="#binary_to_term/1">binary_to_term/1</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> will return the value <c><anno>Any</anno></c>.</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.</p>
        <pre>
> <input>time().</input>
{9,42,44}</pre>
      </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.</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 [].</p>
      </desc>
    </func>
    <func>
      <name name="trace" arity="3"/>
      <type name="trace_flag"/>
      <fsummary>Set trace flags for a process or processes</fsummary>
      <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>PidSpec</anno></c>.</p>
        <p><c><anno>PidSpec</anno></c> is either a pid for a local process, or one of
          the following atoms:</p>
        <taglist>
          <tag><c>existing</c></tag>
          <item>
            <p>All processes currently existing.</p>
          </item>
          <tag><c>new</c></tag>
          <item>
            <p>All processes that will be created in the future.</p>
          </item>
          <tag><c>all</c></tag>
          <item>
            <p>All currently existing processes and all processes that
              will be created in the future.</p>
          </item>
        </taglist>
        <p><c><anno>FlagList</anno></c> can contain any number of the following
          flags (the "message tags" refers to the list of messages
          following below):</p>
        <taglist>
          <tag><c>all</c></tag>
          <item>
            <p>Set all trace flags except <c>{tracer, Tracer}</c> and
              <c>cpu_timestamp</c> that are in their nature different
              than the others.</p>
          </item>
          <tag><c>send</c></tag>
          <item>
            <p>Trace sending of messages.</p>
            <p>Message tags: <c>send</c>,
              <c>send_to_non_existing_process</c>.</p>
          </item>
          <tag><c>'receive'</c></tag>
          <item>
            <p>Trace receiving of messages.</p>
            <p>Message tags: <c>'receive'</c>.</p>
          </item>
          <tag><c>procs</c></tag>
          <item>
            <p>Trace process related events.</p>
            <p>Message tags: <c>spawn</c>, <c>exit</c>,
              <c>register</c>, <c>unregister</c>, <c>link</c>,
              <c>unlink</c>, <c>getting_linked</c>,
              <c>getting_unlinked</c>.</p>
          </item>
          <tag><c>call</c></tag>
          <item>
            <p>Trace certain function calls. Specify which function
              calls to trace by calling
              <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p>
            <p>Message tags: <c>call</c>, <c>return_from</c>.</p>
          </item>
          <tag><c>silent</c></tag>
          <item>
            <p>Used in conjunction 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 if there are match specs they are executed as normal.</p>
            <p>Silent mode is inhibited by executing
              <c>erlang:trace(_, false, [silent|_])</c>,
              or by a match spec executing the <c>{silent, false}</c>
              function.</p>
            <p>The <c>silent</c> trace flag facilitates setting up
              a trace on many or even all processes in the system.
              Then the interesting trace can be activated and
              deactivated using the <c>{silent,Bool}</c>
              match spec function, giving a high degree
              of control of which functions with which 
              arguments that triggers the trace.</p>
            <p>Message tags: <c>call</c>, <c>return_from</c>, 
              <c>return_to</c>. Or rather, the absence of.</p>
          </item>
          <tag><c>return_to</c></tag>
          <item>
            <p>Used in conjunction with the <c>call</c> trace flag.
              Trace the actual return from a traced function back to
              its caller. Only works for functions traced with
              the <c>local</c> option to
              <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p>
            <p>The semantics is that a trace message is sent when a
              call traced function actually returns, that is, when a
              chain of tail recursive calls is ended. There will be
              only one trace message sent per chain of tail recursive
              calls, why 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_spec
              action instead.</p>
            <p>Message tags: <c>return_to</c>.</p>
          </item>
          <tag><c>running</c></tag>
          <item>
            <p>Trace scheduling of processes.</p>
            <p>Message tags: <c>in</c>, and <c>out</c>.</p>
          </item>
          <tag><c>exiting</c></tag>
          <item>
            <p>Trace scheduling of an exiting processes.</p>
            <p>Message tags: <c>in_exiting</c>, <c>out_exiting</c>, and
	    <c>out_exited</c>.</p>
          </item>
          <tag><c>garbage_collection</c></tag>
          <item>
            <p>Trace garbage collections of processes.</p>
            <p>Message tags: <c>gc_start</c>, <c>gc_end</c>.</p>
          </item>
          <tag><c>timestamp</c></tag>
          <item>
            <p>Include a time stamp in all trace messages. The time
              stamp (Ts) is of 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 timestamps be in CPU time, not wallclock. It is
              only allowed with <c>PidSpec==all</c>. If the host
              machine operating system does not support high resolution
              CPU time measurements, <c>trace/3</c> exits with
              <c>badarg</c>.</p>
          </item>
          <tag><c>arity</c></tag>
          <item>
            <p>Used in conjunction with the <c>call</c> trace flag.
              <c>{M, F, Arity}</c> will be 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 the <c>set_on_spawn</c> flag.</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
              the <c>set_on_first_spawn</c> flag.</p>
          </item>
          <tag><c>set_on_link</c></tag>
          <item>
            <p>Makes any process linked by a traced process inherit its
              trace flags, including the <c>set_on_link</c> flag.</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
              the <c>set_on_first_link</c> flag.</p>
          </item>
          <tag><c>{tracer, Tracer}</c></tag>
          <item>
            <p>Specify where to send the trace messages. <c>Tracer</c>
              must be the pid of a local process or the port identifier
              of a local port. If this flag is not given, trace
              messages will be sent to the process that called
              <c>erlang:trace/3</c>.</p>
          </item>
        </taglist>
        <p>The effect of combining <c>set_on_first_link</c> with
          <c>set_on_link</c> is the same as having
          <c>set_on_first_link</c> alone. Likewise for
          <c>set_on_spawn</c> and <c>set_on_first_spawn</c>.</p>
        <p>If the <c>timestamp</c> flag is not given, the tracing
          process will receive the trace messages described below.
          <c>Pid</c> is the pid of the traced process in which
          the traced event has occurred. The third element of the tuple
          is the message tag.</p>
        <p>If the <c>timestamp</c> flag is given, the first element of
          the tuple will be <c>trace_ts</c> instead and the timestamp
          is added last in the tuple.</p>
        <taglist>
          <tag><c>{trace, Pid, 'receive', Msg}</c></tag>
          <item>
            <p>When <c>Pid</c> receives the message <c>Msg</c>.</p>
          </item>
          <tag><c>{trace, Pid, send, Msg, To}</c></tag>
          <item>
            <p>When <c>Pid</c> sends the message <c>Msg</c> to
              the process <c>To</c>.</p>
          </item>
          <tag><c>{trace, Pid, send_to_non_existing_process, Msg, To}</c></tag>
          <item>
            <p>When <c>Pid</c> sends the message <c>Msg</c> to
              the non-existing process <c>To</c>.</p>
          </item>
          <tag><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>Note that the 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><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 <c>call</c> and the <c>return_to</c> flags 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><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 the <c>call</c>
              flag is set, and the function has a match specification
              with a <c>return_trace</c> or <c>exception_trace</c> action.</p>
          </item>
          <tag><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 due to an exception. This trace message is sent
              if the <c>call</c> flag is set, and the function has 
              a match specification with an <c>exception_trace</c> action.</p>
          </item>
          <tag><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>Note that <c>Args</c> is supposed to be the argument
              list, but may be any term in the case of an erroneous
              spawn.</p>
          </item>
          <tag><c>{trace, Pid, exit, Reason}</c></tag>
          <item>
            <p>When <c>Pid</c> exits with reason <c>Reason</c>.</p>
          </item>
          <tag><c>{trace, Pid, link, Pid2}</c></tag>
          <item>
            <p>When <c>Pid</c> links to a process <c>Pid2</c>.</p>
          </item>
          <tag><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><c>{trace, Pid, getting_linked, Pid2}</c></tag>
          <item>
            <p>When <c>Pid</c> gets linked to a process <c>Pid2</c>.</p>
          </item>
          <tag><c>{trace, Pid, getting_unlinked, Pid2}</c></tag>
          <item>
            <p>When <c>Pid</c> gets unlinked from a process <c>Pid2</c>.</p>
          </item>
          <tag><c>{trace, Pid, register, RegName}</c></tag>
          <item>
            <p>When <c>Pid</c> gets the name <c>RegName</c> registered.</p>
          </item>
          <tag><c>{trace, Pid, unregister, RegName}</c></tag>
          <item>
            <p>When <c>Pid</c> gets the name <c>RegName</c> unregistered.
              Note that this is done automatically when a registered
              process exits.</p>
          </item>
          <tag><c>{trace, Pid, in, {M, F, Arity} | 0}</c></tag>
          <item>
            <p>When <c>Pid</c> is scheduled to run. The process will
              run in function <c>{M, F, Arity}</c>. On some rare
              occasions the current function cannot be determined, then
              the last element <c>Arity</c> is 0.</p>
          </item>
          <tag><c>{trace, Pid, out, {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 <c>Arity</c> is 0.</p>
          </item>
          <tag><marker id="gc_start"><c>{trace, Pid, gc_start, Info}</c></marker></tag>
          <item>
            <p>Sent when 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.
              You should not depend on the tuples have any defined
              order. Currently, 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 actual 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, in words, 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_vheap_block_size</c></tag>
	      <item>The total size of binaries, in words, 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><c>{trace, Pid, gc_end, Info}</c></tag>
          <item>
            <p>Sent when garbage collection is finished. <c>Info</c>
              contains the same kind of list as in the <c>gc_start</c>
              message, but the sizes reflect the new sizes after
              garbage collection.</p>
          </item>
        </taglist>
        <p>If the tracing process dies, the flags will be silently
          removed.</p>
        <p>Only one process can trace a particular process. For this
          reason, attempts to trace an already traced process will fail.</p>
        <p>Returns: A number indicating the number of processes that
          matched <c><anno>PidSpec</anno></c>. If <c><anno>PidSpec</anno></c> is a pid,
          the return value will be <c>1</c>. If <c><anno>PidSpec</anno></c> is
          <c>all</c> or <c>existing</c> the return value will be
          the number of processes running, excluding tracer processes.
          If <c><anno>PidSpec</anno></c> is <c>new</c>, the return value will be
          <c>0</c>.</p>
        <p>Failure: If 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 is dislocated on the time-line
          compared to other events in the system. If you know that the
          <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
          you can use <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>. 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> when it
          is guaranteed that all trace messages have been delivered to
          the tracer up to the point that the <c><anno>Tracee</anno></c> had reached
          at the time of the call to
          <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>.</p>
        <p>Note that the <c>trace_delivered</c> message does <em>not</em>
          imply that trace messages have been delivered; instead, it implies
          that all trace messages that <em>should</em> be delivered have
          been delivered. It is not an error if <c><anno>Tracee</anno></c> isn't, and
          hasn't been traced by someone, but if this is the case,
          <em>no</em> trace messages will have been delivered when the
          <c>trace_delivered</c> message arrives.</p>
        <p>Note that <c><anno>Tracee</anno></c> has to 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>An 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. <c>C</c>
          can ensure that the trace isn't truncated by calling
          <c>erlang:trace_delivered(A)</c> when <c>A</c> exits and wait
          for the <c>{trace_delivered, A, <anno>Ref</anno>}</c> message 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"/>
      <type name="trace_info_return"/>
      <type name="trace_info_item_result"/>
      <type name="trace_info_flag"/>
      <type name="trace_match_spec"/>
      <fsummary>Trace information about a process or function</fsummary>
      <desc>
        <p>Returns trace information about a process or function.</p>
        <p>To get information about a process, <c><anno>PidOrFunc</anno></c> should
          be a pid or the atom <c>new</c>. The atom <c>new</c> means
          that the default trace state for processes to be created will
          be returned. <c><anno>Item</anno></c> must have one of the following
          values:</p>
        <taglist>
          <tag><c>flags</c></tag>
          <item>
            <p>Return a list of atoms indicating what kind of traces is
              enabled for the process. The list will be 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>set_on_first_spawn</c>,
              <c>set_on_link</c>, <c>running</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>Return the identifier for process or port tracing this
              process. If this process is not being traced, the return
              value will be <c>[]</c>.</p>
          </item>
        </taglist>
        <p>To get information about a function, <c>PidOrFunc</c> should
          be a 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 at all. <c>Item</c>
          must have one of the following values:</p>
        <taglist>
          <tag><c>traced</c></tag>
          <item>
            <p>Return <c>global</c> if this function is traced on
              global function calls, <c>local</c> if this function is
              traced on local function calls (i.e local and global
              function calls), and <c>false</c> if neither local nor
              global function calls are traced.</p>
          </item>
          <tag><c>match_spec</c></tag>
          <item>
            <p>Return 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>Return the meta trace tracer process or port for this
              function, if it has one. If the function is not meta
              traced the returned value is <c>false</c>, and if
              the function is meta traced but has once detected that
              the tracer proc is invalid, the returned value is [].</p>
          </item>
          <tag><c>meta_match_spec</c></tag>
          <item>
            <p>Return 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>Return 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. Return <c>false</c> otherwise.
              See also
              <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p>
          </item>
          <tag><c>call_time</c></tag>
          <item>
	      <p>Return 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. Returns <c>false</c> otherwise.
	      The call time values returned, <c>[{Pid, Count, S, Us}]</c>,
	      is a list of each process that has executed the function and its specific counters.
              See also
              <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p>
          </item>

          <tag><c>all</c></tag>
          <item>
            <p>Return a list containing the <c>{<anno>Item</anno>, Value}</c> tuples
              for all other items, or return <c>false</c> if no tracing
              is active for this function.</p>
          </item>
        </taglist>
        <p>The actual return value will be <c>{<anno>Item</anno>, Value}</c>, where
          <c>Value</c> is the requested information as described above.
          If a pid for a dead process was given, or the name of a
          non-existing function, <c>Value</c> will be <c>undefined</c>.</p>
        <p>If <c><anno>PidOrFunc</anno></c> is the <c>on_load</c>, the information
          returned refers to the default value for code that will be
          loaded.</p>
      </desc>
    </func>
    <func>
      <name name="trace_pattern" arity="2" clause_i="1"/>
      <type name="trace_pattern_mfa"/>
      <type name="trace_match_spec"/>
      <fsummary>Set trace patterns for global call tracing</fsummary>
      <desc>
        <p>The same as
          <seealso marker="#trace_pattern/3">erlang:trace_pattern(MFA, MatchSpec, [])</seealso>,
          retained for backward compatibility.</p>
      </desc>
    </func>
    <func>
      <name name="trace_pattern" arity="3"/>
      <type name="trace_pattern_mfa"/>
      <type name="trace_match_spec"/>
      <type name="trace_pattern_flag"/>
      <fsummary>Set trace patterns for tracing of function calls</fsummary>
      <desc>
        <p>This BIF is used to enable or disable call tracing for
          exported functions. It must be combined with
          <seealso marker="#trace/3">erlang:trace/3</seealso>
          to set the <c>call</c> trace flag for one or more processes.</p>
        <p>Conceptually, call tracing works like this: Inside
          the Erlang virtual machine there is a set of processes to be
          traced and a set of functions to be traced. Tracing will be
          enabled on the intersection of the set. That is, if a process
          included in the traced process set calls a function included
          in the traced function set, the trace action will be taken.
          Otherwise, nothing will happen.</p>
        <p>Use
          <seealso marker="#trace/3">erlang:trace/3</seealso> to
          add or remove one or more processes to the set of traced
          processes. Use <c>erlang:trace_pattern/2</c> to add or remove
          exported functions to the set of traced functions.</p>
        <p>The <c>erlang:trace_pattern/3</c> BIF can also add match
          specifications to an exported function. A match specification
          comprises a pattern that the arguments to the function must
          match, a guard expression which 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 will not be executed.</p>
        <p>The <c><anno>MFA</anno></c> argument should be a tuple like
          <c>{Module, Function, Arity}</c> or the atom <c>on_load</c>
          (described below). It can be the module, function, and arity
          for an exported function (or a BIF in any module).
          The <c>'_'</c> atom can be used to mean any of that kind.
          Wildcards can be used in any of the following ways:</p>
        <taglist>
          <tag><c>{Module,Function,'_'}</c></tag>
          <item>
            <p>All exported functions of any arity named <c>Function</c>
              in module <c>Module</c>.</p>
          </item>
          <tag><c>{Module,'_','_'}</c></tag>
          <item>
            <p>All exported functions in module <c>Module</c>.</p>
          </item>
          <tag><c>{'_','_','_'}</c></tag>
          <item>
            <p>All exported functions in all loaded modules.</p>
          </item>
        </taglist>
        <p>Other combinations, such as <c>{Module,'_',Arity}</c>, are
          not allowed. Local functions will match wildcards only if
          the <c>local</c> option is in the <c><anno>FlagList</anno></c>.</p>
        <p>If the <c><anno>MFA</anno></c> argument is the atom <c>on_load</c>,
          the match specification and flag list will be used on all
          modules that are newly loaded.</p>
        <p>The <c><anno>MatchSpec</anno></c> argument can take any of the following
          forms:</p>
        <taglist>
          <tag><c>false</c></tag>
          <item>
            <p>Disable tracing for the matching function(s). Any match
              specification will be removed.</p>
          </item>
          <tag><c>true</c></tag>
          <item>
            <p>Enable tracing for the matching function(s).</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>. See the ERTS User's Guide
              for a description of match specifications.</p>
          </item>
          <tag><c>restart</c></tag>
          <item>
	      <p>For the <c><anno>FlagList</anno></c> option <c>call_count</c> and <c>call_time</c>:
              restart the existing counters. The behaviour 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> option <c>call_count</c> and <c>call_time</c>: pause
              the existing counters. The behaviour is undefined for
              other <c>FlagList</c> options.</p>
          </item>
        </taglist>
        <p>The <c><anno>FlagList</anno></c> parameter is a list of options.
          The following options are allowed:</p>
        <taglist>
          <tag><c>global</c></tag>
          <item>
            <p>Turn on or off call tracing for global function calls
              (that is, calls specifying the module explicitly). Only
              exported functions will match and only global calls will
              generate trace messages. This is the default.</p>
          </item>
          <tag><c>local</c></tag>
          <item>
            <p>Turn on or off call tracing for all types of function
              calls. Trace messages will be sent whenever any of
              the specified functions are called, regardless of how they
              are called. If the <c>return_to</c> flag is set for
              the process, a <c>return_to</c> message will also be sent
              when this function returns to its caller.</p>
          </item>
          <tag><c>meta | {meta, <anno>Pid</anno>}</c></tag>
          <item>
            <p>Turn on or off meta tracing for all types of function
              calls. Trace messages will be sent to the tracer process
              or port <c><anno>Pid</anno></c> whenever any of the specified
              functions are called, regardless of how they are called.
              If no <c><anno>Pid</anno></c> 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>trace/3</c>,
              the trace flags are instead fixed to
              <c>[call, timestamp]</c>.</p>
            <p>The match spec function <c>{return_trace}</c> works with
              meta trace and send its trace message to the same tracer
              process.</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. Running counters can be
              paused with <c><anno>MatchSpec</anno> == pause</c>. Paused and running
              counters can be restarted from zero with
              <c><anno>MatchSpec</anno> == restart</c>.</p>
            <p>The counter value can be read with
              <seealso marker="#trace_info/2">erlang:trace_info/2</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 micro-seconds.
	      The counters are stored for each call traced process.</p>
            <p>If call time tracing is started while already running,
              the count and time is restarted from zero. Running counters can be
              paused with <c><anno>MatchSpec</anno> == pause</c>. Paused and running
              counters can be restarted from zero with
              <c><anno>MatchSpec</anno> == restart</c>.</p>
            <p>The counter value can be read with
              <seealso marker="#trace_info/2">erlang:trace_info/2</seealso>.</p>
          </item>

        </taglist>
        <p>The <c>global</c> and <c>local</c> options are mutually
          exclusive and <c>global</c> is the default (if no options are
          specified). The <c>call_count</c> and <c>meta</c> options
          perform a kind of local tracing, and can also not be combined
          with <c>global</c>. A function can be either globally or
          locally traced. If global tracing is specified for a
          specified set of functions; local, meta, call time and call count
          tracing for the matching set of local functions will be
          disabled, and vice versa.</p>
        <p>When disabling trace, the option must match the type of trace
          that is set on the function, so that local tracing must be
          disabled with the <c>local</c> option and global tracing with
          the <c>global</c> option (or no option at all), and so forth.</p>
        <p>There is no way to directly change part of a match
          specification list. If a function has a match specification,
          you can replace it with a completely new one. If you need to
          change an existing match specification, use the
          <seealso marker="#trace_info/2">erlang:trace_info/2</seealso>
          BIF to retrieve the existing match specification.</p>
        <p>Returns the number of exported functions that matched
          the <c><anno>MFA</anno></c> argument. This will be zero if none matched at
          all.</p>
      </desc>
    </func>
    <func>
      <name name="trunc" arity="1"/>
      <fsummary>Return an integer by the truncating a number</fsummary>
      <desc>
        <p>Returns an integer by the truncating <c><anno>Number</anno></c>.</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 which is the number of elements in <c><anno>Tuple</anno></c>.</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 which corresponds to <c><anno>Tuple</anno></c>.
          <c><anno>Tuple</anno></c> may contain any Erlang terms.</p>
        <pre>
> <input>tuple_to_list({share, {'Ericsson_B', 163}}).</input>
[share,{'Ericsson_B',163}]</pre>
      </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), also called GMT, in the form
          <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c> if
          supported by the underlying operating system. If not,
          <c>erlang:universaltime()</c> is equivalent to
          <c>erlang:localtime()</c>.</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, if this is supported by the underlying
          OS. Otherwise, no conversion is done, and
          <c><anno>Universaltime</anno></c> is returned.</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> does not denote
          a valid date and time.</p>
      </desc>
    </func>
    <func>
      <name name="unlink" arity="1"/>
      <fsummary>Remove a link, if there is one, 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 caller is trapping exits, an
          <c>{'EXIT', <anno>Id</anno>, _}</c> message due to the link might have
          been placed in the caller's message queue prior to the call,
          though. Note, the <c>{'EXIT', <anno>Id</anno>, _}</c> message can be the
          result of the link, but can also be the result of <c><anno>Id</anno></c>
          calling <c>exit/2</c>. Therefore, it <em>may</em> be
          appropriate to cleanup the message queue when trapping exits
          after the call to <c>unlink(<anno>Id</anno>)</c>, as follow:</p>
        <code type="none">

    unlink(Id),
    receive
        {'EXIT', Id, _} ->
            true
    after 0 ->
            true
    end</code>
        <note>
          <p>Prior to OTP release R11B (erts version 5.5) <c>unlink/1</c>
            behaved completely asynchronous, i.e., the link was active
            until the "unlink signal" reached the linked entity. This
            had one undesirable effect, though. You could never know when
            you were guaranteed <em>not</em> to be effected by the link.</p>
          <p>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
          pid or a port identifier.</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 given registered name</fsummary>
      <desc>
        <p>Returns the pid or port identifier with the registered name
          <c>RegName</c>. Returns <c>undefined</c> if the name is not
          registered.</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 let other processes (if any) get a chance to
          execute. Using <c>erlang:yield()</c> 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,
	especially in the SMP-emulator as other	processes will have a
	chance to run in another scheduler thread anyway.
	Using this BIF without a thorough grasp of how the scheduler
	works may cause performance degradation.</p></warning>
      </desc>
    </func>
  </funcs>
</erlref>