diff --git a/libc/include/cpio.h b/libc/include/cpio.h
index ceeeb87..c2c20c2 100644
--- a/libc/include/cpio.h
+++ b/libc/include/cpio.h
@@ -26,32 +26,55 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _CPIO_H_
-#define _CPIO_H_
+#pragma once
+
+/**
+ * @file cpio.h
+ * @brief Constants for reading/writing cpio files.
+ */
 
 #include <sys/cdefs.h>
 
+/** Readable by user mode field bit. */
 #define C_IRUSR 0000400
+/** Writable by user mode field bit. */
 #define C_IWUSR 0000200
+/** Executable by user mode field bit. */
 #define C_IXUSR 0000100
+/** Readable by group mode field bit. */
 #define C_IRGRP 0000040
+/** Writable by group mode field bit. */
 #define C_IWGRP 0000020
+/** Executable by group mode field bit. */
 #define C_IXGRP 0000010
+/** Readable by other mode field bit. */
 #define C_IROTH 0000004
+/** Writable by other mode field bit. */
 #define C_IWOTH 0000002
+/** Executable by other mode field bit. */
 #define C_IXOTH 0000001
+/** Set-UID mode field bit. */
 #define C_ISUID 0004000
+/** Set-GID mode field bit. */
 #define C_ISGID 0002000
+/** Directory restricted deletion mode field bit. */
 #define C_ISVTX 0001000
+/** Directory mode field type. */
 #define C_ISDIR 0040000
+/** FIFO mode field type. */
 #define C_ISFIFO 0010000
+/** Regular file mode field type. */
 #define C_ISREG 0100000
+/** Block special file mode field type. */
 #define C_ISBLK 0060000
+/** Character special file mode field type. */
 #define C_ISCHR 0020000
+/** Reserved. */
 #define C_ISCTG 0110000
+/** Symbolic link mode field type. */
 #define C_ISLNK 0120000
+/** Socket mode field type. */
 #define C_ISSOCK 0140000
 
+/** cpio file magic. */
 #define MAGIC "070707"
-
-#endif /* _CPIO_H_ */