First of all, as a note to anyone with questions who is reading this, please try to search for the answer first before posting. LOL. Just Google for it, or something. Then if you can't find anything, come here...

Second, I think this discussion probably belongs in a different thread; doesn't pertain much to game design in the context that it's been presented.

Third, here's a resource for you, straight from GameDev (found using Google, mind you):

http://www.gamedev.net/reference/articles/article1591.asp

Enjoy!