17 Facts About Multics

Multics is an influential early time-sharing operating system based on the concept of a single-level memory.

Nathan Gregory writes that Multics "has influenced all modern operating systems since, from microcomputers to mainframes.

Multics has numerous features intended to ensure high availability so that it would support a computing utility similar to the telephone and electricity utilities.

Multics has a number of standard mechanisms to allow engineers to analyze the performance of the system, as well as a number of adaptive performance optimization mechanisms.

In POSIX terminology, it is as if every file were mmaed; however, in Multics there is no concept of process memory, separate from the memory used to hold mapped-in files, as Unix has.

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Multics is the first major operating system to be designed as a secure system from the outset.

Multics is the first operating system to provide a hierarchical file system, and file names can be of almost arbitrary length and syntax.

Multics is the first to use the now-standard concept of per-process stacks in the kernel, with a separate stack for each security ring.

In 1964, Multics was developed initially for the GE-645 mainframe, a 36-bit system.

GE's computer business, including Multics, was taken over by Honeywell in 1970; around 1973, Multics is supported on the Honeywell 6180 machines, which included security improvements including hardware support for protection rings.

At MIT in 1975, use of Multics was declining and did not recover by 1976 to prior levels.

In 1985, Multics was issued certification as a B2 level secure operating system using the Trusted Computer System Evaluation Criteria from the National Computer Security Center a division of the NSA, the first operating system evaluated to this level.

Multics was distributed from 1975 to 2000 by Groupe Bull in Europe, and by Bull HN Information Systems Inc in the United States.

In 2014, Multics was successfully run on current hardware using an emulator.

Peter H Salus, author of a book covering Unix's early years, stated one position: "With Multics they tried to have a much more versatile and flexible operating system, and it failed miserably".

Design and features of Multics slightly influenced the Unix operating system, which was originally written by two Multics programmers, Ken Thompson and Dennis Ritchie.

The high-reliability, availability, and security features of Multics were extended in Stratus VOS to support a new line of fault tolerant computer systems supporting secure, reliable transaction processing.