PDP-7 UNIX
From Computer History Wiki
Unix (very briefly Unics, as a pun on 'Multics'), a name coined later by Brian Kernighan, was written by Ken Thompson in 1969 to experiment with file systems and support his Space Travel game. After Bell Labs' withdrawal from the Multics project, Thompson was able to find a little-used PDP-7 with a Graphic II display system to work on.
