-#include <errno.h> /* error simbol definitions */
-#include <stdio.h> /* standard I/O functions */
-#include <signal.h> /* signal handling declarations */
-#include <sys/types.h>
-#include <sys/wait.h>
+#include <errno.h> /* error definitions and routines */
+#include <stdio.h> /* standard I/O library */
+#include <signal.h> /* signal constants, types and functions */
+#include <sys/types.h> /* primitive system data types */
+#include <sys/wait.h> /* process termination constants and functions */