Multics - Revision history

Jnc: /* External links */ +Multics Myths

2024-12-15T17:44:15Z

‎External links: +Multics Myths

Jnc: Add link; teaks

2024-12-15T17:38:32Z

Add link; teaks

Jnc: /* External links */ +Multics commands and active functions

2024-09-16T13:33:10Z

‎External links: +Multics commands and active functions

Jnc: /* External links */ +Multics Users Face Their Maker

2024-07-16T16:37:20Z

‎External links: +Multics Users Face Their Maker

Jnc: /* External links */ +Multix OS -- Pioneer of time sharing

2024-03-07T15:05:48Z

‎External links: +Multix OS -- Pioneer of time sharing

Jnc: /* External links */ +Honeywell marketing brochure

2024-02-07T16:37:51Z

‎External links: +Honeywell marketing brochure

Jnc: /* External links */ +Multics System Maintenance Procedures Manual

2024-01-03T19:07:13Z

‎External links: +Multics System Maintenance Procedures Manual

Jnc: /* External links */ +e Multics Storage System Program Logic Manual

2023-08-14T14:36:44Z

‎External links: +e Multics Storage System Program Logic Manual

Jnc: never spellwd in caps

2023-01-24T21:56:15Z

never spellwd in caps

Jnc: /* External links */ +mgmt papers

2023-01-19T17:43:50Z

‎External links: +mgmt papers

@@ Line 75: / Line 75: @@
 *** [http://www.acsac.org/2002/papers/classic-multics-orig.pdf Multics Security Evaluation: Vulnerability Analysis, ESD-TR-74-193]
 *** [http://www.acsac.org/2002/papers/classic-multics.pdf Thirty Years Later: Lessons from the Multics Security Evaluation]
 ** [https://www.multicians.org/multics-images.html Image Gallery] - many of people, some of machines <!--
 *** [https://www.multicians.org/mulimg/h6180-doors-open-big.jpg CISL Honeywell 6180 Multics machine, 1976] -->

@@ Line 11: / Line 11: @@
 }}
-Multics (''Multi''plexed ''I''nformation and ''C''omputing ''S''ervice - although it is ''never'' spelled in capitals) was an early [[time-sharing]] [[operating system]] which has influenced every operating system created since; especially via [[UNIX]] (the name of which is a play on 'Multics'), which was created by [[Bell Laboratories|Bell Labs]] personnel who had worked on Multics, after Bell Labs pulled out of the Multics project.
+Multics (''Multi''plexed ''I''nformation and ''C''omputing ''S''ervice - although the short form is ''never'' spelled in all capitals) was an early [[time-sharing]] [[operating system]] which has influenced almost every operating system created since; especially via [[UNIX]] (the name of which is a play on 'Multics'), which was created by [[Bell Laboratories|Bell Labs]] personnel who had worked on Multics, after Bell Labs pulled out of the Multics project.
 Multics was intended as an ''information utility''; i.e. a service to which those who wanted information processing would connect, much as people connect to the electric grid for power.
-This dictated a number of Multics' features, including the modular structure of the hardware (with multiple [[Central Processing Unit|CPUs]] and [[main memory]] banks, fully interconnected, and with the ability to take individual units out of service for maintenance, or to simply add additional units as demand increased over time); extremely robust security (so that individual users in a facility open to all comers would be protected from each other), etc.
+This dictated a number of Multics' features, including the modular structure of the hardware (with multiple [[Central Processing Unit|CPUs]] and [[main memory]] banks, fully interconnected, and with the ability to take individual units out of service for maintenance, or to simply add additional units as demand increased over time); extremely robust security (so that individual users in a facility open to all comers would be protected from each other); etc.
 ==Technical aspects==
@@ Line 31: / Line 31: @@
 In modern UNIX terminology, it was as if every file were 'mmap()'ed; however, in Multics there was no concept of process memory, separate from the memory used to hold mapped-in files: all memory in the system was part of some segment, which appeared in the file system; this included the temporary scratch memory of the process, such as its [[kernel]] [[stack]], etc.
-Multics also implemented [[virtual memory]], which was very new at that time (only a handful of other systems implemented it at that point); but this was not a new idea with Multics.
+Multics also implemented [[virtual memory]], which was very new at that time (only a handful of other systems implemented it at that point); but this was not a new idea with Multics. The segmentation and paging in Multics are often discussed together, but it is important to realize that they were not fundamentally connected; one could theoretically have an SLS system which did not page. Paging was added as well for practical reasons.
-The segmentation and paging in Multics are often discussed together, but it is important to realize that they were not fundamentally connected; one could theoretically have an SLS system which did not page. Paging was added as well for practical reasons.
+Multics also made popular the now-common technique of having separate per-process stacks in the kernel; this was apparently first seen in the [[Burroughs B5000]], but was not well known. This is an important kernel structuring advance since it greatly simplifies code; if a process discovers, somewhere deep inside a [[subroutine]] [[call stack]] that it needs to wait for an event, it can simply do so right there, instead of having to [[unwind]] its way out, and then return later when the waited-for event has happened.
-Multics also made popular the now-common technique of having separate per-process stacks in the kernel; this was apparently first seen in the [[Burroughs B5000]], but was not well known.
+The entire system was written almost entirely in [[high-level language]] ([[PL/I]]) - which was quite rare at the time; the Burroughs B5000 had an OS written in [[ALGOL]], but this was the only previous system to do so.
 ===Hardware===

@@ Line 11: / Line 11: @@
 }}
-Multics (''Multi''plexed ''I''nformation and ''C''omputing ''S''ervice - although it is ''never'' spelled in capitals) was an early [[time-sharing]] [[operating system]] which has influenced every operating system created since; especially via [[UNIX]] (the name of which is a play on 'Multics'), which was created by Bell Labs personnel who had worked on Multics, after Bell Labs pulled out of the Multics project.
+Multics (''Multi''plexed ''I''nformation and ''C''omputing ''S''ervice - although it is ''never'' spelled in capitals) was an early [[time-sharing]] [[operating system]] which has influenced every operating system created since; especially via [[UNIX]] (the name of which is a play on 'Multics'), which was created by [[Bell Laboratories|Bell Labs]] personnel who had worked on Multics, after Bell Labs pulled out of the Multics project.
 Multics was intended as an ''information utility''; i.e. a service to which those who wanted information processing would connect, much as people connect to the electric grid for power.
@@ Line 24: / Line 24: @@
 * [[Dynamic linking]] for libraries, etc
 * A [[command processor]] implemented entirely in user code
-* A hierachical [[file system]]
+* A hierarchical [[file system]]
 * Separate [[access control list]]s for each 'file'
@@ Line 69: / Line 69: @@
 * [http://www.multicians.org Multicians] - a great source of info
 ** [https://multicians.org/history.html History]
 *** [https://multicians.org/ge635.html The GE-635s at Project MAC and BTL]

@@ Line 81: / Line 81: @@
 *** [https://www.multicians.org/mulimg/h6180-doors-open-big.jpg CISL Honeywell 6180 Multics machine, 1976] -->
 ** [https://www.multicians.org/ge635.html The GE-635s at Project MAC and BTL] - much of the early story of Multics
 * [http://web.mit.edu/multics-history/ Multics] - MIT's Multics site
 ** [http://web.mit.edu/multics-history/source/Multics_Internet_Server/Multics_sources.html Multics sources]
@@ Line 91: / Line 92: @@
 ** [http://bitsavers.org/pdf/honeywell/large_systems/multics/AM81-04_maintPrcds_Nov86.pdf Multics System Maintenance Procedures Manual] - describes the multitude of front panels
 * [http://s3data.computerhistory.org/brochures/honeywell.multicssystem.1975.102646162.pdf The Multics System] - marketing brochure from Honeywell
-* [https://wiki.livingcomputers.org/doku.php?id=multics Multics] - Multics page at the [[Living Computer Museum]] DokuWiki
+* [https://web.archive.org/web/20230914064053/https://wiki.livingcomputers.org/doku.php?id=multics Multics] - Multics page at the [[Living Computer Museum]] DokuWiki (archived)
 * [http://ringzero.wikidot.com/ Multics reborn wiki]
 * [https://multics-wiki.swenson.org/ Running Multics wiki]

@@ Line 97: / Line 97: @@
 * [http://sourceforge.net/projects/h6180/ H6180 emulator (abandoned)]
 * [https://www.cs.virginia.edu/~evans/greatworks/MULTICS.pdf multics] - useful summary
 * [https://www.youtube.com/watch?v=jni7wk7bjxA Multics booting] - A video of a H6180 CPU front panel hooked up to a SIMH H6180 emulation booting Multics
 [[Category: Operating Systems]]

@@ Line 89: / Line 89: @@
 ** [http://www.bitsavers.org/pdf/honeywell/large_systems/multics/AG95_multicsVM_Jun72.pdf The Multics Virtual Memory] - this version contains, starting on pg. 174 of the PDF, a discussion of the changes from the 645 to the 6180
 ** [http://www.bitsavers.org/pdf/honeywell/large_systems/multics/AN61A_storageSysPLM_Sep78.pdf Multics Storage System Program Logic Manual] - detailed description of the Multics paging/segmentation mechanisms
 * [https://wiki.livingcomputers.org/doku.php?id=multics Multics] - Multics page at the [[Living Computer Museum]] DokuWiki
 * [http://ringzero.wikidot.com/ Multics reborn wiki]

@@ Line 11: / Line 11: @@
 }}
-Multics (''Multi''plexed ''I''nformation and ''C''omputing ''S''ervice) was an early [[time-sharing]] [[operating system]] which has influenced every operating system created since; especially via [[Unix]] (the name of which is a play on 'Multics'), which was created by Bell Labs personnel who had worked on Multics, after Bell Labs pulled out of the Multics project.
+Multics (''Multi''plexed ''I''nformation and ''C''omputing ''S''ervice - although it is ''never'' spelled in capitals) was an early [[time-sharing]] [[operating system]] which has influenced every operating system created since; especially via [[UNIX]] (the name of which is a play on 'Multics'), which was created by Bell Labs personnel who had worked on Multics, after Bell Labs pulled out of the Multics project.
 Multics was intended as an ''information utility''; i.e. a service to which those who wanted information processing would connect, much as people connect to the electric grid for power.
-This dictated a number of Multics' features, including the modular structure of the hardware (with multiple [[CPU]]s and [[main memory]] banks, fully interconnected, and with the ability to take individual units out of service for maintenance, or to simply add additional units as demand increased over time); extremely robust security (so that individual users in a facility open to all comers would be protected from each other), etc.
+This dictated a number of Multics' features, including the modular structure of the hardware (with multiple [[Central Processing Unit|CPUs]] and [[main memory]] banks, fully interconnected, and with the ability to take individual units out of service for maintenance, or to simply add additional units as demand increased over time); extremely robust security (so that individual users in a facility open to all comers would be protected from each other), etc.
 ==Technical aspects==
-In addition to the modular hardware, and robust security, Multics had a number of other major technical features, some commonplace now (and some still not too common - alas), but major advances when it was first designed (in 1967). They include:
+In addition to the modular hardware, and robust security, Multics had a number of other major technical features, some commonplace now (and some still not too common - alas), but major advances when it was first designed (in 1965). They include:
 * A [[single-level store]]
@@ Line 27: / Line 27: @@
 * Separate [[access control list]]s for each 'file'
-The single-level store architecture of Multics was particularly significant: it discarded the clear distinction between [[file]]s (called ''segments'' in Multics) and [[process]] memory. The memory of a process consisted solely of segments that were mapped into its [[address space]]. To read or write to them, the process simply used normal [[instruction]]s; the operating system took care of making sure that all the modifications were saved to [[secondary storage]] ([[disk]]).
+The single-level store architecture of Multics was particularly significant: it discarded the clear distinction between [[file]]s (replaced by ''[[segment]]s'' in Multics) and [[process]] memory. The memory of a process consisted solely of segments that were mapped into its [[address space]]. To read or write to them, the process simply used normal [[instruction]]s; the operating system took care of making sure that all the modifications were saved to [[secondary storage]] ([[disk]]).
 In modern UNIX terminology, it was as if every file were 'mmap()'ed; however, in Multics there was no concept of process memory, separate from the memory used to hold mapped-in files: all memory in the system was part of some segment, which appeared in the file system; this included the temporary scratch memory of the process, such as its [[kernel]] [[stack]], etc.
@@ Line 43: / Line 43: @@
 ===Hardware===
 Multics ran only on special hardware, which provided hardware support for its single-level store [[architecture]].
@@ Line 49: / Line 50: @@
 == Multics today ==
 Multics is dead. There are no systems running it today (the last one was [http://slashdot.org/articles/00/11/13/066228.shtml shut down in 2000]).
@@ Line 71: / Line 70: @@
 * [http://www.multicians.org Multicians] - a great source of info
 ** [https://multicians.org/history.html History]
 *** [https://multicians.org/phase-one.html Phase One]
 *** [https://multicians.org/phx.html Multics in Phoenix]