Corewars is a computer game, in the most literal sense of the term. The point is, two or more programmers write programs in a funny assembly variant called redcode, and then run them both at the same time, trying to see which one can terminate the other. The programs are run in a virtual machine, (often pMARS), which means that you can't crash or burn anything with your malicious programs. This is, of course, unless there's an ersatz Operating System loaded in the core, as well.

The proper name for this is debated to be either Corewars or Corewar. It is a game created by A.K. Dewdney in one of his old Computer Recreations columns from Scientific American magazine. To play, each player writes a program in assembly language whose sole purpose is to destroy all other programs in the memory space. Along with C-Robots, it is one of the few games in which the player must write a program.