1 files changed, 23 insertions, 0 deletions
diff --git a/system/doc/tutorial/port.c b/system/doc/tutorial/port.c
new file mode 100644
index 0000000000..3a9a4e442c
--- /dev/null
+++ b/system/doc/tutorial/port.c
@@ -0,0 +1,23 @@
+/* port.c */
+
+typedef unsigned char byte;
+
+int main() {
+  int fn, arg, res;
+  byte buf[100];
+
+  while (read_cmd(buf) > 0) {
+    fn = buf[0];
+    arg = buf[1];
+    
+    if (fn == 1) {
+      res = foo(arg);
+    } else if (fn == 2) {
+      res = bar(arg);
+    }
+
+    buf[0] = res;
+    write_cmd(buf, 1);
+  }
+}
+