Multics

Multics: /muhl'tiks/ n.  [from "MULTiplexed Information
   and Computing Service"] An early (late 1960s) timesharing
   operating system co-designed by a consortium including MIT, GE, and
   Bell Laboratories.  Multics was very innovative for its time ---
   among other things, it introduced the idea of treating all devices
   uniformly as special files.  All the members but GE eventually
   pulled out after determining that {second-system effect} had
   bloated Multics to the point of practical unusability (the
   `lean' predecessor in question was {CTSS}).  Honeywell
   commercialized Multics after buying out GE's computer group, but it
   was never very successful (among other things, on some versions one
   was commonly required to enter a password to log out).  One of the
   developers left in the lurch by the project's breakup 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}.