-#include <stdio.h> /* standard I/O functions */
-#include <fcntl.h>
-#include <signal.h> /* signal handling declarations */
-#include <unistd.h>
+#include <stdio.h> /* standard I/O functions */
+#include <fcntl.h> /* file control functions */
+#include <signal.h> /* signal constants, types and functions */
+#include <unistd.h> /* unix standard library */