(defun add-header-guard ()
  (interactive)
  (if (buffer-file-name)
      (let ((fn (upcase (file-name-nondirectory 
			 (file-name-sans-extension buffer-file-name))))
	    (begin (point-marker)))
	(goto-char (point-min))
	(insert "#ifndef _" fn "_H" "\n#define _" fn "_H\t1" "\n")
	(goto-char (point-max))
	(insert "\n#endif")
	(goto-char begin))
    (message (concat "Buffer " (buffer-name) " must have a filename"))))