Way OT programming question

[friar_josh at tcbug.org (Josh Paetzel)]

I've been muddling through some of the source files for FreeBSD 
5.2.1-RELEASE, and I've noticed that a large number of .c files 
in /usr/src have something similar to below in them:

#ifndef lint
#if 0
static char sccsid[] = "@(#)cat.c       8.2 (Berkeley) 4/27/95";
#endif
#endif /* not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/bin/cat/cat.c,v 1.29 2003/04/30 17:40:28 
obrien Exp $");

1) Isn't 'if 0' always negative?
2) What is the __FBSDID line doing?

-- 
Thanks,

Josh Paetzel