random number algorythms

can someone give me a formula or algorythm that will generate a random or pseudo-random number?

i've always been wondering how this is done...

Oh man, I saw this somewhere before. I think it's pretty basic from what I remember. It just has some simple operations with large numbers I think.

source code for this problem.

Do a search on google for the "Mersene Twister", it's supposed to be strong enough for industrial use, whatever that means.