Corewar is a programming game in which players write programs to battle in a virtual arena called the "core". The programs, called "warriors", are written in a simple assembly language and are loaded into the memory of the Corewar virtual machine.
The warriors then execute in parallel, moving around the memory of the "core" and attempting to destroy the instructions of the other warriors. The last program standing in the "core" is the winner.
The Corewar game was invented in 1984 by D.G. Jones and A.K. Dewdney. Since then, many variations have been created and the game has become popular in programmer and computer science communities as a programming and optimization challenge.