Multics 843 entries
20 Apr 2024

Glossary - M

Glossary of Multics acronyms and terms. Entries by Tom Van Vleck ([THVV]) unless noted.

Index| A| B| C| D| E| F| G| H| I| J| K| L| M| N| O| P| Q| R| S| T| U| V| W| X| Y| Z|
See Project MAC.

[DMW] A database research group at Project MAC in the 1960s. The MacAIMS (MAC Advanced, Interactive Management System) group performed research on Management Information Systems. Sponsored by ARPA, it created a prototype system on CTSS that was used by Project MAC management to analyze and model its business. Bob Goldstein then led the effort to leverage the power of Multics to create a much more powerful system. This resulted in the development of MADAM, one of the first relational database management systems, as well as improvements in the human interface based on the ARDS terminal and the IMLAC PDS-1 graphic workstation. With Prof. Malcolm Jones as faculty sponsor, MacAIMS was one of the last groups at Project MAC that was associated with the MIT Sloan School of Management. The project was active from the late 1960s into 1971. (See "THE MACAIMS DATA MANAGEMENT SYSTEM", MIT-LCS-TM-024.)

[BSG] Multics version of LISP. Multics LISP was one of the first LISP implementations on virtual memory. Multics Version I Lisp was entirely written in PL/I (including its compiler, which is extremely unusual) by David Reed, then an undergraduate at MIT, and was part of the Standard Service System libraries.

Version II Lisp, known as "Multics MacLisp" was developed by MIT undergraduates Dave Reed and Dave Moon to support Macsyma. It was a descendant of the Project MAC MACLISP dialect.

Bernie Greenberg at Honeywell CISL took over maintenance and extension of MacLisp in 1974, and used it to write Emacs.

For more information, see section 1.7.10 of Multics Features and "The Multics MACLISP Compiler: The Basic Hackery -- a Tutorial" and "Multics Emacs: The History, Design and Implementation"

Symbolic mathematics subsystem written in LISP at MIT AI Lab. Joel Moses led this team. MACSYMA was ported to MacLisp by Dave Moon in 1974 and used for some large problems no other machine could handle; Multics MACSYMA could do them by using virtual memory.

Michigan Algorithm Decoder. A programming language developed on the IBM 7094 by the late Bob Graham, Bruce Arden, and Bernard Galler at University of Michigan. MAD was a descendant of ALGOL 58, with many nice features, and was used at MIT for CTSS programming. Henry Ancona worked on a design for a Multics MAD compiler but it was never implemented.

[DMW] MacAIMS Data Management system. An early relational data base management system. Developed at MIT utilizing the large Multics address space and its protection rings, MADAM was the data store underlying MacAIMS, which was used by Project MAC in developing budgets and managing the organization. (See "THE RELATIONAL APPROACH TO THE MANAGEMENT OF DATA BASES", MIT-LCS-TM-023.)

[WOS] Small scale Multics-like system done at the MIT Architecture Machine group on an Interdata 7/32 by Lee Parks and Ted Anderson as undergraduates.

Quick and dirty unsecure mail was written by Tom Van Vleck in 1969, in imitation of his (secure) CTSS MAIL command. The Multics mail command used segments writeable by everyone for mailboxes, with access coordinated by a simple lock. In the mid 70s, this command's internals were replaced to call ms_, the ring-1 message segment facility, and the user-ring mailbox files were replaced by secure ring-1 files. Even later, mail was replaced by commands like read_mail and send_mail, designed for use in a networking environment, running in ring 2. The early Multics mail tools predated the Internet and "net mail". Story: The History of Electronic Mail. See also xmail Info segment for mail command

(1) The per-user file that mail is received in, including the user's .mbx message segment.

(2) A memory cell in the SCU, used to interrupt an active device.

Multics site: Johannes Gutenberg Universitaet Mainz (Mainz, Germany). First and only Multics in Germany. 1982-1986.

[BSG] Multics had modules such as "ioam" (I/O Assignment manager) and "GIM" (GIOC interface manager). Noel Morris started spelling out "manager," with "iom_manager". Then André Bensoussan called his NSS VTOC manager "vtoc_man": as these names became progressively more andromorphic, it became increasingly easy to refer to programs with personal pronouns, a usage started by Steve Webber. The PL/I compiler always had a "base_man" (pointer register manager), which was really cool. Swapping had a swap_track_man. Bernie Greenberg had a command-line variable manager, cl_vbl_man, that many people liked simply because the name was so cool-sounding. (Note that "manager", like "manual", is from the Latin "manus", hand, not the Teutonic "Mann".)

mandatory access control
Access controls that prevent a user from making information available arbitrarily, as opposed to discretionary access controls like the ACL mechanism. The Access Isolation Mechanism added mandatory access controls to Multics, enabling it to get a B2 rating.

master directory
Master directories are quota directories that have a logical volume attribute different from their parent; they draw their disk quota from a special segment, a Master Directory Control Segment, that specifies the total quota a user can allocate on a logical volume.

master mode
The 645 version of privileged mode.


Multics Checkout Bulletin. Early Project MAC document series. Technical white paper, internal to the development group. See Development Documentation

Multics Computer Center. Another name for Honeywell's System M in Phoenix.

[RBW] Canadian DND Multics site. Maritime Command Headquarters, Halifax, Nova Scotia. Installed 1982. Multics was used at MCHQ to support the Canadian Navy's strategic command and control, and intelligence system. The Multics system was shut down on 10/30/00.

[Alf Burnham] Maritime Command Operations Information Network. Primary application on the Canadian DND MCHQ Multics site.

Multics Change Request. The authorization form that had to be approved as part of the CISL software development process before a change was made to Multics. See Software Development Process and Development Documentation.

MCR Board
Group of software developers who met weekly to consider MCRs. See Software Development Process.

[BSG] Multics Communication System. Either the DN355 assembly-language software that ran terminals and comm lines for 6180 Multics, or that software taken in conjunction with the ring 0 TTYDIM which implemented the Multics side of its protocols. MCS was flexible enough to handle bisync lines, X.25, and other spiffy features, in addition to terminals at many speeds. Emacs brought on the need for efficient character-at-a-time I/O and echo negotiation. People in other Honeywell Software organizations were continually annoyed at the fact that Multics required its own communications software in the comm processors, and did not use standard Honeywell packages. The architects and implementors of MCS, which replaced older DATANET software by Dick Snyder, were Mike Grady, Robert Coren, and Larry Johnson, the "FNPMeisters", ("f'noopmeisters") as they were known.

[THVV] Article: Multics Communications and Networking.

Multics site. McDonnell Douglas, Transport Aircraft. Long Beach, CA, USA. Hosted Support Equipment Data Acquisition and Control System (SEDACS) C-17 support application. 1985-1995.

Multics Data Base Manager. Another name for MRDS.

MDBM Data Dictionary

Multics Design Note. Early Project MAC document series. See Development Documentation.

Multics Emergency Change Request. Submits emergency changes to the exposure sites. See MSCR.

Honeywell Marketing Education. A flying squad of trainers, who taught Multics customers how to administer and use their systems.

Biomedical databank established at Rennes by the NMR laboratory in 1985. Used via SUNIST.

Third party spreadsheet package for Multics produced in 1986 by The Mega Group of Irvine, CA. Documented in Honeywell manual DW19. Mega also produced MegaFile, a "personal database manager" for Multics.

Multics command: combines changes to files descended from a common ancestor. See "Automated Merging of Software Modifications". Info segment for merge_ascii command


Honeywell bought GE's computer business in October 1970, according to J.A.N. Lee's article "The Rise and Fall of the General Electric Corporation Computer Department". This event is referred to as "the merger." Actually, Honeywell ended up running several unrelated and non-cooperating computer companies. The major change seemed to be the nameplates on the machines. GE's computer division became Honeywell LISD, with mostly the same management and policies.

[Jean Bellec] Story: Shangri-La and the Paris 645.

Codename for the Flower CPU design. See Multics Company.

message coordinator
[BSG] Facility by Tom Van Vleck (1972) that defines and manages multiple logical operator consoles and routes them to and multiplexes them over physical consoles. Before the advent of this masterpiece of I/O switchery, (see ios_), Multics actually required a console for each of its daemons, and the array of TTY37s with their bleary red-shifts, 40's-looking 6-volt pilot lights, and autonomous, cinematic chattering that was needed to run the 645 Multics service on the 9th floor of (545) Tech Square was either extremely impressive or unimpressive, depending on one's degree of sophistication. (I was young and new, and impressed.)

[THVV] The message coordinator is a multi-threaded event-driven dispatcher similar to dialup_ that drives multiple physical devices from user-ring queue segments. Each daemon process attaches its I/O streams through a DIM, mc_tty_, that reads and writes a queue segment. Story: The Message Coordinator.

message segment
Ring-1 segment that contains individual messages, used to implement mailboxes. Used extended access to specify additional access controls.

Message segment access modes include:
(add) process can add a message
(delete) process can delete a message.
(read) process can read any message.
(own) process can read or delete its own messages.
(status) process can find out how many messages are in the segment.
(wakeup) process can send a normal priority wakeup.
(null) process cannot access the segment in any way.
(urgent) process can send "urgent" messages to the user accepting messages on the mailbox. (Urgent messages are not currently implemented)

Multics has many metering commands, such as file_system_meters, traffic_control_meters, pre_page_meters, device_meters, tty_meters, page_trace, trace, meter_gate, meter_signal, alarm_clock_meters, vtoc_buffer_meters, total_time_meters, the ready message, and the script driver. The microsecond hardware clock made it easy to instrument code. Almost all subsystems have metering built in, running all the time; the commands just display the internal counters. The standard procedure for installing a new system release included running a 60-minute performance benchmark. Paper: "The Instrumentation of Multics" by John Gintell and Jerry Saltzer.

(1) Multics Graphics System

(2) Max Smith's initials.

Master Group Table. System administration table. Defines work classes and load control groups, which determine the number of users from each group that are permitted to log in, and the percentage of system resources that they are allocated while logged in.

Multics Hardware Acceptance Tests. A test run on major changes to the system. Runs a wide variety of Multics applications and validates the results.

Multics Integrated Data Store. A network database interface, similar to the GCOS IDS database, that ran on top of MRDS. Written by Jim Weeldreyer and Oris Friesen of PMDC.

Small, simple, fast version of the GIM, introduced in 1968.

Ministere de la Culture
Multics site: Ministere de la Culture. In Paris, then outside. Several database oriented applications. Had 4 CPUs. 1981-1986.

Ministerie van Sociale Zaken
Multics site: Ministerie van Sociale Zaken en Werkgelegenheid [SOZAWE] (Den Haag, The Netherlands). First and only Multics in the Netherlands.

Third party stat package for Multics by Minitab, Inc. Designed to run on a wide variety of operating systems.

Massachusetts Institute of Technology. A private land-grant university, founded in 1860, located in Cambridge, MA. Its slogan used to be "A university polarized around science."

MIT's early involvement in computers included ESL's construction of WHIRLWIND in the 1940s and 50s. In the 1960s, MIT had a 704, then a 709, then a 7090, and then a 7094, all supplied by IBM on very favorable terms. The Compatible Time-Sharing System (CTSS) was begun as an experiment at the MIT Computation Center, and grew into an everyday tool for users at MIT and Project MAC.

In 1964, Project MAC, with funding from ARPA, decided to develop its next generation time-sharing system on the GE-645 in cooperation with GE and Bell Telephone Laboratories.

The MIT Computation Center, renamed the Information Processing Center, continued to run IBM systems, and took over running Multics as a campus service from 1969 until it was shut down in 1988. During this time, the Student Information Processing Board (SIPB) provided computer services to many undergraduates, some of whom went on to become Multicians.

For more information, see the MIT Site History.

[Jamie O'Connell] MRDS to Janus Database Transfer: A windowed application providing bi-directional database conversion. It was developed by RCI late in the game, as a free add-on to CS/Janus customers.

Master Mode Entry opcode, used by GCOS programs to trap to the supervisor.

Graffiti file at MIT. (mmtu = mene mene tekel uphairsin, the writing on the wall, name due to Charlie Garman.) This info seg was maintained by IPC personnel, who responded to comments from users.

MPC OnLine Test System run by TOLTS. See AU77, Multics Online Test and Diagnostics Reference Manual.

Sale Multics didn't make?

Game programmed for Multics by Jerry Grochow in the late 60s, later commercialized as MasterMind. Interesting because the score ladder was accessed by many people. Described in Jerry's 1972 paper "MOO in Multics" in Software -- Practice and Experience. PL/I source for moo is available online.

[JMG] The Wikipedia entry for the game Mastermind claims it may have been inspired by Multics moo. My suspicion is that the assumption (that my Moo inspired a board game) is totally erroneous as Moo (Bulls and Cows) is a century old game as far as I know.

Multics OLPARS Operating System, program developed at RADC for "detection, identification, and transformation of patterns contained in high- dimensional data."

Mosteller's Law
Rule about meetings, attributed to Prof. Fred Mosteller at Harvard. It states that "a meeting's effectiveness goes to zero after 90 minutes." Many meetings at CISL would be cut off after this limit, and if more work remained, a follow-up meeting would be scheduled. MCR Board meetings were an exception.

Message of the Day. This info seg is printed when a user logs in, and is updated by operations to inform users of system schedules, new rules, and so forth.

[BWS] Multics Online Work Station Environment. IBM PC support package. Its major feature was BFT (Background File Transfer), which allowed the user to start a file transfer and go on to do something else (a big deal for a PC in 1987). Documented in GB66, Multics On-Line Work Station Environment User's Guide.

[THVV] Design work was also done to allow PCs to be backed up to Multics, called Micro File Backup.

[BSG] Microprogrammed Peripheral Controller. These huge Honeywell peripheral controllers (on the 6180) requiring software loading did not seem to provide any noticeable advance in functionality over the non-microprogrammed peripherals on the 645. See Zero Six Dog.

[Jean Bellec] The Common Peripheral Controllers of the 645 were 6-bits. The MPC was microprogrammed, so the same hardware was used on different devices (unit records, tapes, disks) and was connected to the IOM by a 9-bit channel, allowing ASCII data transfer. The fact that firmware was stored in RAM and has to be loaded as part of the boot process was an inconvenience, but that method reduced maintenance cost, because no parts had to be changed for bug corrections. It was a pity that GCOS and Multics did not agree on a common boot process that could have taken the burden of booting the hardware.

Multics Programmers' Manual. The original user manual for Multics, replaced by Honeywell manuals AG90, AG91, AG91, and AG93. See Development Documentation.

Multics Planning Notebook. Planning and coordination document used in the late 60s to manage Multics bringup. See Development Documentation.

Multics Project Office. A group within GE /Honeywell FSO that tried to sell Multics to the government.

Multics Release. The numeric designation of operating system versions presented to the customer world. Selected MSS versions of the system from the MIT site were packaged and tested at PMDC in Phoenix and released from there to customers. The last release of Multics was MR 12.5. See MSS.

Multics Relational Data Store. Originally written by Jim Weeldreyer and Oris Friesen of PMDC. MRDS was the first commercial relational database product. Unbundled product.

See Paul McJones's summary description of MRDS on the System R web site.

Multics Relational Data Store Multibase. Written at INRIA to support multiple MRDS databases. Paper by Witold Litwin and Abdelaziz Abdellatif, Multidatabase Interoperability, IEEE Computer pp10-18, Dec 1986. Query language called MDSL.

CTSS command that wrote a GECOS IMCV tape on the MIT Project MAC 7094 for input to the 6.36 simulator. Replaced by Multics command generate_mst.

Multics Report Program Generator. Produces reports from a MRDS database. Done by Jim Falksen at PMDC.

Internal Honeywell codename for the DPS6plus processor.

Multics Staff Bulletin. Document describing rules and administrative stuff. See Development Documentation.

Multics System Change Request. Form sent by a developer to make a change to the system software. (Used to be called the "yellow form" when it was on paper. Became an electronic form in the 1980s.) Accompanied with an approved MCR. Required approvals: Software Integration Project Leader; Security Coordinator (if TCB affected); documentation manager. See Software Development Process.

(1) Multics Special Projects; Minneapolis group responsible for marketing and supporting first Multics sites after the merger.

[WEB] (2) The airport code for Minneapolis/St. Paul.

Disk unit.

Multics System Programmer's Manual. About 3000 pages of documentation of the system, written mostly before coding started. The total design presented was more complex and grandiose than was ever implemented. See the MSPM Table of Contents.

Multics Standard System. System numbers used internal to the development group, and at the MIT development site. Cf. MR.

[BSG] Either "Multics standard tape" or "Multics system tape", which latter was in fact an instance of the former, being a checksummed, labeled, headered, trailered, fixed-length-record tape format with periodic tape marks used for all backup tapes and disk snapshots, as well as the tapes from which the system and BOS were booted. The record header included two fixed octal constants determined to be optimal for checking controller integrity. (The format is described in BB.3.01 Multics Standard Tape Format.) This format later proved to be inimical to the goal of having hardware-bootable tapes, and was a nightmare to support in the several assembly-language environments (e.g., BOS) that required it. See bootload and Zero Six Dog.

MST checker
Stand-alone facility invented by Peter Schicker that checked a Multics boot tape for unsatisfiable links and other common errors, used during the 1966-68 time frame. Taken over and maintained and extended by Tom Van Vleck.

Disk unit. MSU0400 held about 75 MB of usable Multics pages. same as DSS191.

Disk unit. MSU0451 held about 149 MB of usable Multics pages. These were CDC 9766 disks with an unformatted capacity of about 200MB.

Disk unit. MSU0500 held about 600 MB of usable Multics pages.

Disk unit. MSU0501 held about 1006 MB of usable Multics pages.

Disk unit. MSU3381 held about 3367 MB of usable Multics pages, and was an IBM OEM.

Multics Technical Bulletin. Replaced MCBs after Multics was "checked out." Technical white paper, internal to the development group. An index of 770 MTBs from 1973 to 1987 is available online (100K, 08/17/96). Also see Development Documentation.

Multics Task Report. Early Project MAC document series. Described who was doing what. See Development Documentation.

[BSG] I used "mult" to mean either "actively doing Multics programming, or logged in interacting with Multics, as opposed to being away from a terminal," or secondly, said of systems, "successfully time-sharedly running users in the user ring," i.e., what a crashed or hung system doesn't do. "Really? It was multing just fine a half hour ago." This was in part backed by the commands used to start up the system: at CISL, there was a BOS RUNCOM MULT to start a development run. There was also the ring-1 boot time command mult(ics) to execute part 1 of; it started a "special session," not a service session, that is, users couldn't log in.

David Levin used to tell the story, he had first cut his super-long hair and beard, and how Moseley Meer just sat there next to him multing for a half-hour before saying, "David?"

Or "Can you stop multing and spend some time with some human beings?" Today that would be called "Multics hacking," modulo the unfortunate ambiguity of the term "hacking."

[BSG] In general, anyone who multed, i.e., programmed (or even regularly used) Multics as an activity. I (BSG) occasionally used it as an accolade via litotes, e.g., "Noel was one multer not soon to be forgotten."

[David Warley] We [at STC] showed Mike Pandolfo an Apple II running VisiCalc and he created "Multicalc," the first truly interactive mainframe based spreadsheet..

Anyone who contributed to the development and success of Multics. There is no such thing as an ex-Multician.

[BSG] I used "Multician" to mean any pro-level, skilled Multics programmer/designer. Much like "musician." You might be a really good amateur and be highly regarded as a Multician, or even be a pro but not really be a Multician. I think it had to be your main, or full-time pursuit, though. "Moon, in addition to his thousand other talents, was a hell of a Multician," though. I was "as well known a Multician as any." "Stan Dunten was one of the original core of Multicians."

[BSG] Stylistically consistent with the standards of Multics design and excellence. Prelinking and phcs_$flush_file_pages are not multicious. Consistent with and excellent in the Multics design philosophy.

Multiplexed Information and Computing Service. A proper noun, always spelled in mixed case. Informal plural: Multices (Latinate).

Multics Company
Olin Sibert's proposed company, intended to purchase rights to Multics software from Honeywell, resurrect the Flower design (afterward called Merlin), and build new Multics-specific I/O hardware (Excalibur). This venture was discussed after the Flower cancellation in 1985, but Honeywell management chose not to license the technology.

(1) Multilevel secure: certified for use by users with differing DoD security authorizations. AFDSC ran its Multics this way, by using AIM. In the mid 1970s, only Multics could do this.

(2) See page multilevel.

multilevel daemon

[MTB-607] The ring-zero multiplexers provide a framework within the Multics supervisor for implementing multiplexed communications protocols. They were created when the need for support for such protocols became clear. Adding support for multiplexed protocols to the FNP was considered impossible without a complete redesign. Within this framework, support currently exists for the IBM 3270 (BSC version), VIP 77XX, X.25 level 3, and HASP protocols. The framework is also used to support communication with the FNP itself and for the software terminal facility. This code largely runs in a ring-zero masked and wired environment. It consists of about 25000 lines of PL/I and a small amount of ALM.

[THVV] Article: Multics Communications and Networking.

Running more than one CPU in the same system. Multics was designed from the beginning to support symmetric multiprocessing, meaning that all CPUs take an equal role in the system; there's no "master" CPU. (Although the "bootload CPU" had a special role for a long time.)

David Lawrence at AFDSC ran a 6-CPU configuration as a test, and reported that there was a 15% degradation per CPU:
due to memory interference and lock conflicts.

Having more than one program ready to run in memory. This was a big advance over single-user batch systems when it was first introduced. Multics transmuted this concept into that of "eligibility."

multisegment file (MSF)
One of the weaknesses of Multics is that data files larger than a megabyte are hard to map into the virtual memory. The user-ring file system supports multisegment files as a partial solution. A multisegment file is a directory with a nonzero bit count equal to the number of components of the file. Each component is a segment, contained in the directory, and named 0 ... N. The Multics stream I/O system allows programs to access multisegment files via iox_ and the vfile_ outer module. Programs that produce printed listings, such as compilers, use a set of routines that can write MSFs, as do the language runtimes for PL/I, FORTRAN, and COBOL. The I/O daemon can print MSFs. In MR 12.0, object segments could be MSFs and Emacs was modified to be able to edit MSFs.