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<operating system> /muhl'tiks/ MULTiplexed Information and Computing Service. A time-sharing operating system co-designed by a consortium including MIT, GE and Bell Laboratories as a successor to MIT's CTSS. The system design was presented in a special session of the 1965 Fall Joint Computer Conference and was planned to be operational in two years. It was finally made available in 1969, and took several more years to achieve respectable performance and stability.

Multics was very innovative for its time - among other things, it was the first major OS to run on a symmetric multiprocessor; provided a hierarchical file system with access control on individual files; mapped files into a paged, segmented virtual memory; was written in a high-level language (PL/I); and provided dynamic inter-procedure linkage and memory (file) sharing as the default mode of operation. Multics was the only general-purpose system to be awarded a B2 security rating by the NSA.

Bell Labs left the development effort in 1969. Honeywell commercialised Multics in 1972 after buying out GE's computer group, but it was never very successful: at its peak in the 1980s, there were between 75 and 100 Multics sites, each a multi-million dollar mainframe.

One of the former Multics developers from Bell Labs was Ken Thompson, a circumstance which led directly to the birth of Unix. For this and other reasons, aspects of the Multics design remain a topic of occasional debate among hackers. See also brain-damaged and GCOS.

MIT ended its development association with Multics in 1977. Honeywell sold its computer business to Bull in the mid 1980s, and development on Multics was stopped in 1988 when Bull scrapped a Boston proposal to port Multics to a platform derived from the DPS-6.

A few Multics sites are still in use as late as 1996.

The last Multics system running, the Canadian Department of National Defence Multics site in Halifax, Nova Scotia, Canada, shut down on 2000-10-30 at 17:08 UTC.

The Jargon file 3.0.0 claims that on some versions of Multics one was required to enter a password to log out but James J. Lippard <>, who was a Multics developer in Phoenix, believes this to be an urban legend. He never heard of a version of Multics which required a password to logout. Tom Van Vleck <> agrees. He suggests that some user may have implemented a 'terminal locking' program that required a password before one could type anything, including logout.


Usenet newsgroup: news:alt.os.multics.

[Jargon File]


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