Multics OS

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tarun basu
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Multics OS

🧩 1. Basic Information

Field β€”>Description
OS Name β€”>Multics (Multiplexed Information and Computing Service)
Developer β€”>MIT, Bell Labs, General Electric (later Honeywell)
First Released β€”>1969 (project started 1964)
Latest Version β€”>Discontinued in 2000 (last running system shut down)
License Type β€”>Initially proprietary (Honeywell); now historical source available for study
Supported Platforms β€”>GE-645, Honeywell 6180 (mainframe-class systems)
Still Active? β€”>❌ No (historic OS, but studied in OS theory courses)

βš™οΈ 2. Kernel & Architecture

Kernel Type: Early form of segmented, paged, multi-layered architecture, often described as a ringed kernel

Memory Management: Hardware-enforced rings of privilege (precursor to CPU ring levels)

Supported virtual memory, dynamic linking, hierarchical file systems

Developed as a time-sharing system to support multiple users on mainframes simultaneously

🌟 3. Key Features

Advanced security model: Rings of protection, strict access control lists (ACLs) β€” direct ancestor of modern CPU privilege levels

Hierarchical file system: looked very similar to modern UNIX directories

Dynamic linking: programs could link to libraries at runtime (foundation of shared libraries & DLLs today)

Virtual memory with demand paging

Time-sharing with fine-grained accounting, so many users could share a system fairly

Interactive command line & early shell environments

Even supported multi-language programming environments (PL/I, FORTRAN, assembly)

πŸ“ˆ 4. Version History & Important Milestones βœ…

Milestone / Version β€”>Year β€”>Description
Project starts at MIT β€”>1964 β€”>Collaboration between MIT, Bell Labs, GE
First operational Multics β€”>1969 β€”>Ran on GE-645 mainframe
Honeywell takes over β€”>1970 β€”>GE computer division sold to Honeywell
UNIX created by ex-Bell Labs engineers β€”>~1969–70 β€”>Ken Thompson & Dennis Ritchie left Multics to create UNIX, influenced by it heavily
Commercial systems used β€”>70s–80s ---->Deployed by government & large institutions
Last running Multics shut down β€”>2000 β€”>Canadian system retired, officially ended operational life

🎯 5. Target Audience & Use Cases

Large universities & research labs: ran hundreds of simultaneous users in the 70s & 80s

Government & secure research facilities: because of its security model

Telephone companies & air traffic control: appreciated robust multi-user processing

Today: studied by CS students & historians to understand multi-user OS concepts

βœ… 6. Pros & Cons

Pros β€”>Cons
Pioneered concepts like rings, dynamic linking, hierarchical filesystems β€”>Required large, expensive mainframes

Strong security & fault isolation for its time β€”>Complex system, hard to debug & maintain

Excellent documentation, design papers β€”>Eventually overshadowed by simpler UNIX
Direct ancestor of UNIX/Linux/Mac kernel ideas β€”>Proprietary, tied to specific Honeywell hardware

🎨 7. UI Demo & Visuals

Terminal session on a Multics console (green-screen style)

Showing command line environment with hierarchical directories (ls style)

Access control examples setting user permissions on files

Early email programs and text editors

Diagrams from the famous β€œrings of protection” model

πŸ“¦ 8. Ecosystem & App Support

Supported multiple programming languages simultaneously: PL/I (primary), FORTRAN, COBOL, assembly

Early database systems, academic compilers, interactive shells

Could run text editors, mail systems, accounting & quota tools

No modern apps, but was the base template for nearly all multi-user OS that followed

πŸ” 9. Security & Updates

Most advanced security model of its era:

Hardware & software ring protection (kernel vs user mode)

Mandatory & discretionary access control lists on files

Login auditing and extensive logs

Updated by Honeywell engineers, with patches delivered via magnetic tapes to large installations

🌍 10. Community, License & Development

Initially proprietary (MIT & GE research), then owned by Honeywell

Last code base released for historical study β€” available via Multicians.org archives

Huge influence on computing:

Inspired UNIX, Linux, Windows NT security rings, modern dynamic linking, process memory separation

Active community of historians & enthusiasts who document papers, manuals, system logs

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