$Id tag in comment headers

Question

When I read source from open source projects I often find a comment line with "$Id" at the header of the file, f. ex.:

// $Id: addappwindowa.c 30792 2009-03-07 22:40:04Z neil $

• Is there an "offical" syntax for this lines? (What does "30792" means? )
• Are there editors that auto-generate these "$Id"s?
• Are there any tools that use this information?

Answer 1

That id seems to come from a Subversion keyword.
It's automatically generated by Subversion after every commit, and it is composed by filename - revision number - date and time of last change - author of last change.
For more info on Subversion and source control, you can start by taking a look at:

http://subversion.tigris.org/
http://en.wikipedia.org/wiki/Version_control