The Jargon File (version 4.4.7, 29 Dec 2003):

Core Wars
 n.

    A game between assembler programs in a machine or machine simulator, where
    the objective is to kill your opponent's program by overwriting it.
    Popularized in the 1980s by A. K. Dewdney's column in Scientific American
    magazine, but described in Software Practice And Experience a decade
    earlier. The game was actually devised and played by Victor Vyssotsky,
    Robert Morris Sr., and Doug McIlroy in the early 1960s (Dennis Ritchie is
    sometimes incorrectly cited as a co-author, but was not involved). Their
    original game was called ?Darwin? and ran on a IBM 7090 at Bell Labs. See 
    core. For information on the modern game, do a web search for the
    ?rec.games.corewar FAQ? or surf to the King Of The Hill site.