-#include <sys/types.h> /* predefined types */
-#include <sys/stat.h> /* */
-#include <unistd.h> /* include unix standard library */
-#include <stdio.h> /* include standard I/O library */
-#include <stdlib.h> /* standard library */
-#include <string.h> /* ANSI C standard string */
-#include <errno.h> /* errorstring */
-#include <signal.h> /* signals */
-#include <sys/ipc.h>
-#include <sys/msg.h>
+#include <sys/types.h> /* primitive system data types */
+#include <sys/stat.h> /* file characteristics constants and functions */
+#include <unistd.h> /* unix standard library */
+#include <stdio.h> /* standard I/O library */
+#include <stdlib.h> /* C standard library */
+#include <string.h> /* C strings library */
+#include <errno.h> /* error definitions and routines */
+#include <signal.h> /* signal constants, types and functions */
+#include <sys/ipc.h> /* SysV IPC functions */
+#include <sys/msg.h> /* SysV message queues */