Core War

Core War is a competitive programming game wherein each contestant enters a "warrior", a program written in redcode, a language similar to assembly.

All warriors have their instructions loaded into the shared circular memory core, and take turns executing one instruction. The goal is to be the last warrior remaining in the core, either by outliving the others, or causing them to halt execution (usually by writing a DAT instruction into whatever cell of the core they are about to execute as an instruction).