Core Wars is a simulation game. A number of programs are loaded into a
virtual machine and executed. The programs can try to crash each other, 
manipulate other programs, overwrite as much memory as they can, etc...
The "best" program is selected according to a scoring mechanism which
involves the number of memory cells the program has overwritten, the 
number of other programs it has crashed and whether/when it crashed.

WWW: http://corewars.sourceforge.net/