Multics was developed initially for the [GE 645]? mainframe, a 36-bit system. It was the first operating system written in a high level language; PL/I was used.
Multics was especially interesting for lacking a clear distinction between files and memory. All files were treated as virtual memory; to read or write to them one simply mapped them into ones [address space]?. (In Unix terminology, it was as if every file was mmaped.) The disadvantage of this was that the size of segments on the GE 645 was limited to 1 megabyte, and therefore extra code had to be used to work on files larger than this. (In the days before huge bit-map? graphics, this limit was rarely encountered.)
Bell Labs pulled out of the project in 1969. Some of the people who had worked on it there went on to create Unix, and Unix shows evidence of Multics in some areas, especially the naming of commands.
Honeywell? bought GE's computer division, released a better hardware base, and continued system development until 1985. About 80 multi-million-dollar sites were installed, at universities, industry, and government sites. The French university system had quite a few in the early 1980s. After Honywell stopped supporting Multics, users migrated to other systems including Unix. The last Multics machine was shut down on Halloween 2000.
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