Danny Amor's Online Library/Danny Amor's Online Library - Volume 1.iso/html/faqs/alt/os.multics/faq_multics_general

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From: [e-mail] (Tom Van Vleck)
Subject: FAQ Multics General
Message-ID: <[e-mail]>
Sender: [e-mail] (More Bytes Than You Can Read)
Organization: Multicians
Date: Fri, 29 Jul 1994 23:33:17 GMT
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Summary: General information about the Multics operating system.
Expires: 1 Sep 1994

archive-name: multics/general

05/09/94 THVV info on WWW page from Stan Zanarotti
06/01/94 THVV added info on GEMSOS from Paul Karger.
06/01/94 THVV split out the features into a new file to stay below 32K.

This is as far as I have gotten with the Multics FAQ.
Please post corrections/additions or mail them to
<[e-mail]>
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Lane A. Robert <[e-mail]> archives this group on pc.usl.edu in
/pub/multics/alt.os.multics.

The collected System-M Forum transactions from the [e-mail]
(alt.os.multics) mailing list are now available via anonymous ftp to
vela.acs.oakland.edu (141.210.10.2).  They are stored in the directory
/pub/multics.  Jeff Marraccini also archives monthly traffic from this
newsgroup there in Unix compressed format files.

Jeff is populating one of Oakland's Gopher servers with articles from the
archives.  Articles are organized chronologically.

To link or access the server from Gopher or WWW:
Type=1
Name=alt.os.multics Archives
Path=1/Network Services & Databases/USENET News/alt.os.multics Archives
Host=gopher.acs.oakland.edu (141.210.10.11)
Port=70
URL: gopher://gopher.acs.oakland.edu:70/11/Network Services & Databases
/USENET News/alt.os.multics Archives

Stan Zanarotti ([e-mail]) has created a Multics information page on the
World Wide Web.  It contains a GIF of the Multics logo, and current copies
of the FAQ from this newsgroup.  The URL is
"http://www.mit.edu:8001/afs/net/user/srz/www/multics.html".

=================================================================
0.      FAQ documents posted monthly in alt.os.multics
0.1.      Multics General (this Document) (THVV)
0.2.      List Of Multicians (in 3 parts) (THVV)
0.3.      Multics Chronology (THVV)
0.4.      List Of Multics Sites (THVV)
0.5.      Multics Bibliography (THVV)
0.6.      Multics History (THVV)
0.7.      Multics Features (THVV)

1.      What was Multics?
1.1.      Summary
1.2.      Goals
1.3.      Notable features
1.3.1.      Segmented memory
1.3.2.      Virtual memory
1.3.3.      High-level language implementation
1.3.4.      Shared memory multiprocessor
1.3.5.      Multi-language support
1.3.6.      Relational database
1.3.7.      Security
1.3.8.      On-line reconfiguration
1.3.9.      Software Engineering
1.4.      Influence on other systems
1.4.1.      UNIX
1.4.2.      GCOS 6
1.4.3.      Primos
1.4.4.      VOS
1.4.5.      Apollo Domain
1.4.6.      NTT DIPS
1.4.7.      Amber
1.4.8.      GEMSOS
1.4.9.      Other systems using rings

2.      Multics today
2.1.      Where can I get a Multics account today?
2.2.      I'd like to see some Multics source. How?
2.3.      Could Multics be ported to a modern micro?
=============================================================
1.      What was Multics?
1.1.      Summary
Multics (Multiplexed Information and Computing Service) was a
timesharing operating system begin in 1965 and still in use today.  The
system was started as a joint project by MIT Project MAC, Bell
Telephone Laboratories, and GE.  Prof.  F.  J.  Corbato of MIT led the
project.  Bell Labs withdrew from the development effort in 1969, and
later GE sold its computer business to Honeywell, which continued
Multics development and offered Multics as a commercial product.  At
the peak there were almost 100 Multics sites.

Multics ran on special expensive CPU hardware which provided a
segmented, paged, ring-structured virtual memory.  The system was a
symmetric multiprocessor with shared physical and virtual memory.  The
operating system was programmed in PL/I.

Elliot Organick's book, _The Multics System, an Examination of its
Structure_, describes the system as it was in about 1968.  MIT started
providing timesharing service on Multics to users in fall of 1969.  GE
sold the next system to the US Air Force, and the military use of
Multics led to some of the sustem's security features.  Honeywell sold
more systems to government, and to auto makers, universities, and
commercial data processing services.

Honeywell decided not to create a new hardware generation for Multics
in the mid-80s and stopped developing the operating system.  A few
systems are still in use: for example, dockmaster.mil.

1.2.      Goals
There were nine major goals for Multics:
1.2.1.    Convenient remote terminal use.
1.2.2.    Continuous operation analogous to power & telephone services.
1.2.3.    A wide range of system configurations, changeable without
          system or user program reorganization.
1.2.4.    A high reliability internal file system.
1.2.5.    Support for selective information sharing.
1.2.6.    Hierarchical structures of information for system administration
          and decentralization of user activities.
1.2.7.    Support for a wide range of applications.
1.2.8.    Support for multiple programming environments & human interfaces.
1.2.9.    The ability to evolve the system with changes in technology and
          in user aspirations.

1.3.      Notable features
1.3.1.      Segmented memory
The Multics memory architecture divided memory into segments. Each
segment had addresses from 0 to 256K words (1 MB). The file system was
integrated with the memory access system so that programs could simply
access files by making memory references.

1.3.2.      Virtual memory
Multics used paged memory in the manner pioneered by the Atlas system.
Addresses generated by the CPU were translated by hardware from a
virtual address to a real address. A three-level scheme, using disk,
drum, and core, provided transparent access to the virtual memory.

1.3.3.      High-level language implementation
Multics was implemented in the PL/I language. Only a small  part of
the system was implemented in assembly language. This was a radical
idea at the time.

1.3.4.      Shared memory multiprocessor
The Multics hardware architecture supported multiple CPUs sharing
the same physical memory. All processors were equivalent.

1.3.5.      Multi-language support
In addition to PL/I, Multics supported BCPL, BASIC, APL, FORTRAN,
COBOL, ALGOL 68 and Pascal. Routines in these languages could call
each other.

1.3.6.      Relational database
Multics provided the first commercial relational database product,
the Multics Relational Data Store (MRDS), in 1978.

1.3.7.      Security
Multics was designed to be secure from the beginning. In the 1980s,
the system was awarded the B2 security rating by the US
government NCSC, the first (and for years only) system to get a B2
rating.

1.3.8.      On-line reconfiguration
As part of the computer utility orientation, Multics was designed
to be able to run 7 days a week, 24 hours a day. CPUs, memory, I/O
controllers, and disk drives can be added to and removed from the
system configuration while the system is running.

1.3.9.      Software Engineering
The development team spent a lot of effort trying to find ways to build
the system in a disciplined way.  The Multics System Programmer's Manual
(MSPM) was written before implementation started: it was 3000 or so
pages and filled about 4 feet of shelf space in looseleaf binders.
(Clingen and Corbato mention that we couldn't have built the system
without the invention of the photocopier.) High level language, design
and code review, structured programming, modularization and layering
were all employed extensively to manage the complexity of the system,
which was one of the largest software development efforts of its day.

1.4.      Influence on other systems
1.4.1.      UNIX
Ken Thompson and Dennis Ritchie worked on Multics until Bell Labs
dropped out of the Multics development effort in 1969.  The UNIX systems
name is a pun on Multics attributed to Brian Kernighan.  Some ideas in
Multics were developed further in UNIX.  See <<KLT evolution paper??>>
for history.

1.4.2.      GCOS 6
Honeywell's GCOS 6 operating system for the Level 6 minicomputers
was strongly influenced by Multics.

1.4.3.      Primos
Prime's Primos operating system shows a strong Multics influence.
Bill Poduska worked on Multics at GE before founding Prime, and
several other senior Multicians worked at Prime. Poduska referred
to Primos as "Multics in a shoebox."

1.4.4.      VOS
Stratus's VOS operating system shows a strong Multics influence.
Bob Freiburghouse, former Multics languages manager, was one of
the founders of Stratus; many Multicians are still Stratus employees.

1.4.5.      Apollo Domain

Bill Poduska went on from Prime to help found Apollo, and Domain was
known as "Multics in a Matchbox."  Apollo's OS shows strong Multics
influence. For instance, the basic access to stuff on disk is via a
single-level store directly based on Multics.  Supposedly some of the
motivation for the object-store style of file system came from Multics
too. (Info from Frederick Roeber)

1.4.6.      NTT DIPS
NTT undertook a massive effort to clone Multics, which led to their DIPS
(Denden Information Processing System) series of mainframes.  DIPS
machines are still in widespread use in Japan today by NTT, but everyone
agrees that they are going away.  I believe that Intermetrics developed
the DIPS PL/I compiler for NTT.  (Info from Carl Hoffman)

1.4.7.      Amber
Multics also influenced Amber, the operating system produced by the S-1
project at Livermore between 1979 and 1986 or so.  The original Amber
group was familiar with Multics as users - the original development work
was done on MIT-Multics - but I don't believe it included anyone who'd
actually worked on the Multics kernel itself.

The most important Multics influences were writing the operating system
in a high-level language, the single-level storage system, and an
emphasis on security, although rings were not present on the last
generation of S-1 machine.  Amber was heavily influenced by critiques of
Multics such as the Multics Kernel Redesign Project.  In its later
years, Amber made serious strides toward machine independence.

The developers hoped to make it "Multics done better," as reported in a
DATAMATION article.  Jeff Broughton co-wrote the compiler for the Pastel
language used for Amber.  (Info from Jay Pattin)

1.4.8.      GEMSOS
The Gemini GEMSOS secure operating system for the Intel architecture was
developed by Roger Schell to support a Multics-style segmented
environment in a system designed to meet A1 security requirements.
(info from Paul Karger)

1.4.9.      Other systems using rings
Many other systems since Multics have also used rings including:
   VME/B for the ICL 2900
   AOS/VS for the Data General MV8000
   VMS for the DEC VAX
   the Hitachi 5020 time sharing system (first with hardware rings)
(from Paul Karger)

2.      Multics today
2.1.      Where can I get a Multics account today?
It won't be easy.  The Multics sites still running are listed in the
Sites FAQ.  You could get a job at one of them, if they are hiring.  If
you had a good reason, you might be able to get an account on
DOCKMASTER.

2.2.      I'd like to see some Multics source. How?
ACTC Inc, of Calgary, Alberta, Canada has rights to the Multics source.
They are doing maintenance of Multics for the remaining Multics sites.
The director there is Arun Gatha.  It was suggested in this group, in
spring 1993, that ACTC produce or make the source available for a
Multics source CD-ROM.  Several people wrote letters to Arun Gatha about
this.  As far as I know, there has been no response to these letters.

2.3.      Could Multics be ported to a modern micro?
Yes.  As a matter of fact, several projects were started to try this in
the 80s, as described in this news group.  None of these projects
finished.  Porting Multics would be a big job and risky, and the final
product would need further development to match current state of the
art.  Paul Green says, "I think it would be easier to try 'improving'
existing technology than to resurrect Multics itself."