Players compete in the game of Corewar by writing Warriors. A warrior is a program written in an assembly like programming language called redcode. Below is an example of a simple Corewar Warrior named 'Dwarf'.

add #4, 3
mov 2, @2
jmp -2
dat #0, #0

A warrior is made up of a number of instructions, each written on a new line. The above example contains four instructions. Therefore when this warrior is loaded into the Core, it will occupy four consecutive memory addresses.

Warriors own one or more processes which execute the warrior's instructions sequentially. If a process executes an illegal instruction (usually a dat, the process is terminated. If all of a warrior's processes are terminated, the warrior is eliminated from the round.

The objective of corewar is to write a warrior which will still be running (have active processes) after all other warriors have been terminated.

See the Redcode Reference for further details on the redcode language.