SPACEWAR n. A space-combat simulation game, inspired by E. E. "Doc"
   Smith's "Lensman" books, in which two spaceships duel around a central
   sun, shooting torpedoes at each other and jumping through hyperspace.
   This game was first implemented on the PDP-1 at MIT in 1962. In 1968-69,
   a descendant of the game motivated Ken Thompson to build, in his spare
   time on a scavenged PDP-7, the operating system that became {{Unix}}.
   Less than nine years after that, SPACEWAR was commercialized as one of
   the first video games; descendants are still {feep}ing in video arcades
   everywhere.


Source: The Jargon File