Multics

Multics (Multiplexed Information and Computing Service) was an influential early time-sharing operating system. The project was started in 1964 in Cambridge, Massachusetts. The last known natively running Multics installation was shut down on October 30, 2000, at the Canadian Department of National Defence in Halifax, Nova Scotia, Canada. Virtually all modern operating systems are heavily influenced by Multics, through Unix, either directly (Linux, OS X) or indirectly (Microsoft Windows).