Multics was an early operating system, a sort of spiritual ancestor to UNIX. It was one of the first operating systems that focused heavily on interactive operation, rather than executing batch jobs like the GE and IBM mainframe systems of the day. It never achieved the level of success that was hoped for, and ended up sold to Honeywell. Honeywell proceeded to neglect it for the next several years, focusing on the GCOS system they had acquired from GE. Multics did influence the GCOS systems, with GCOS 6 and GCOS 7 being more or less direct descendants of it, but as a standalone product was gradually phased out in the 80's. It lives on today in the forms of NEC ACOS-2, Bull GCOS 7, and Stratus VOS, all of which are direct descendants of the Multics operating system. The main programming environment on Multics was (and to some extent still is) PL/I, which hasn't exactly helped its continuing legacy.