Updated: 08/02/2020 by Computer Hope
VisiCalc software running on the Multics operating system

Multics, also known as Multiplexed Information and Computing Service, was a time-sharing operating system developed by MIT, General Electric, and Bell Labs, first released in 1964. Notable developers who worked on Multics include Ken Thompson and Dennis Ritchie.

New concepts introduced in Multics

  • A hierarchical file system, using file names of arbitrary length and support for symbolic links.
  • A single-level store for data access that removed the distinction between files and process memory. Modern operating systems share similar feature where the memory of every process is a part of the file system, located in the /proc directory.
  • Dynamic linking where a process may incorporate separately compiled code when it runs. Dynamic linking allows a program to use the most recent version of any external routines it might call.
  • On-line reconfiguration where hardware components such as CPUs, memory modules, and disk drives could be added and removed while the system was running.

The last machine to run Multics was decommissioned in 2000, but the concepts and characteristics of Multics are still found in the Windows, Linux, and macOS X operating systems.

Dynamic Linking, Hierarchical file system, Operating System terms