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 1960--61. SPACEWAR aficionados formed the core of the early hacker culture at MIT. Nine years later, 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 feeping in video arcades everywhere.