HTML updated 2/25/95
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The proposed Multics FAQ Glossary project has grown to about 150K
of text, as people remember terms and definitions we used.
I tried to post a version of it about the 10th, but it never reached
the east coast.. so I am sending this to Bernie so he can post it.
There are still entries with a ? meaning they need to be written or
expanded. We seem to be tending toward more of an encyclopedia format
than a dictionary; some entries diverge from their subject in interesting
ways. If you see anything that would offend or belittle anyone, it's
unintentional; point it out and I will remove or reword it. I have tried
to stick to present tense describing features of Multics that still
exist, but it's easy to slip into past tense: if you spot any of these,
point them out to me so I can fix them too.
Send me contributions and I'll merge them into the file, and post it
March 1 with the other FAQs. -- <tom_van_vleck@taligent.com>
====================================================================
Glossary of Multics acronyms and terms.
Last modified: Mon Feb 20 1995
Please post corrections to alt.os.multics or mail them to me.
Entries by Tom Van Vleck unless noted.
02/06/95 THVV corrections from Bernie Greenberg
02/06/95 THVV corrections from Bruce Sanderson
02/07/95 THVV Major additions from Bernie
02/08/95 THVV Major additions from Bernie
02/09/95 THVV Corrections from Richard Shetron
02/09/95 THVV Major additions from Bernie
02/09/95 THVV Major additions from Bernie
02/12/95 THVV Additions from Vince Scarafino
02/14/95 THVV Additions from Dave Vinograd
02/14/95 THVV Additions from Conrad Longmore
02/14/95 THVV Major additions from Bernie
02/15/95 THVV Major additions from Bernie
02/15/95 THVV Additions from Earl Boebert
02/15/95 THVV Info on SIPB from Bob Frankston
02/17/95 THVV Major additions from Bernie
1ISG
Name of a group in the Air Force that operated the last of the AFDSC
Multices in the Pentagon.
1050
First IBM terminal with Selectric mechanism. Used on CTSS and
Multics. Built into a desk with a desk-side box for the electronics.
Row of switches above the keyboard for doing things like controlling
the paper tape reader.
2741
IBM terminal with Selectric mechanism, came after the 1050. Smaller
desk. Widely used on CTSS and Multics.
6180
The second-generation Multics machine, with major architectural
improvements over the 645. Also, the generic term for the
architecture of all subsequent Multics machines produced by
Honeywell.
6.36
A simulation environment, that simulated the 645 machine (at first
called the 636) on the GE635 under GECOS. This environment was used
for initial debugging and bringup of Multics in the 1966 time frame.
645
The computer system that Multics first ran on, produced by General
Electric.
7punch
Binary card format used by the I/O daemon for punching and reading.
Inherited from CTSS. Named after the 5-7 punch in column 1 that
identifies the format.
abbrev
Steve Webber wrote this command, which becomes the user's command
processor, remembering whatever used to be the command processor, and
expands user-defined abbreviations before parsing the command line.
This tool is a direct descendant of . SAVED, ("dot saved") on CTSS,
written by Noel Morris and Tom Van Vleck.
ABR
Address Base Register. The "segmentation" registers in the 645 CPU.
See pointer register.
absentee
The Multics absentee facility is like traditional batch processing,
or the UNIX cron facility. A user creates an exec_com file and
submits it using the submit_abs_request command, and the answering
service will pick it off the queue and run it later.
absolute
(1) An absolute pathname descends from the root. It begins with >.
(2) An absolute address, as opposed to a "paged," "virtual," or
"appended" address, is a physical core address. The CPU uses
absolute addresses in the DBR and in PTWs, and during initial system
startup.
absolute mode
The hardware startup mode of the 6180 and 645 processors when the
hardware mode knob is turned to "Multics". The CPU behaves more less
like a GCOS processor, and paging and segmentation don't seem to be
operative. In fact, the distinction is subtle: When the "mode" knob
is at "GCOS", paging and segmentation really aren't there. But in
"Multics" position, "absolute" mode is equivalent to running in an
unpaged segment at location 0, and it is even possible to reference
segmented addresses: appending unit activity is optional and per
control unit cycle. An attempt to actually transfer to an address
"in a segment" throws the CPU into appending mode, where instruction
fetches and non-indirect, non-pointer register references come from
the segment pointed to by the PPR. Also, faults and interrupts put
the CPU back in absolute mode, but the second instruction of the
fault vector is always, in Multics, a transfer to a segmented
address, restoring appending mode (even though the SCU instruction
preceding it that stored the very status of the appending unit, inter
alia, was executed in absolute mode!) See bootstrap1. BOS was not
run in absolute mode, although it transferred to bootstrap1 in
absolute mode. [BSG]
access control
The Multics feature that checks if a user can do something. The user
identity, established at login, is checked against the ACL of the
thing being accessed.
accounting
Multics comes with an elaborate accounting system, that summarizes
usage and produces multiple printed billing reports, written by Tom
Van Vleck.
active
Said of a segment. An active segment is a segment, that is to say a
file (see virtual memory), that has a page table in core. Only a
small fraction of the files in the whole system have page tables in
core at any one time, namely, those "actively" being used. Segment
control keeps a list of all processes that have SDWs for each active
segment, to be able to disconnect them when the segment is
"deactivated" or access to it is changed. [BSG]
active function
A command, enclosed in brackets, inserted in a command line. The
shell invokes the inserted command and captures its return value and
put the value in the command line for further evaluation. For
example, delete [files *.pl1] deletes all PL/1 files in the working
directory. The term "active function" comes from Calvin Mooers' TRAC
language, and was adopted to name a feature previously called
"interjected commands" in earlier versions of the shell.
ACL
Access Control List. A list of user names and project names in
combination specifying individual and group access rights to a
segment. First introduced in Multics.
ACS
Access Control Segment. A segment whose effective access determines
access to some other resource. ACSs for peripheral devices are kept
in >sc1>rcp. ACSs for logical volumes are kept in >lv.
ACTC
Multics site: (Calgary Alberta, Canada).
AcuRay
Later name for Industrial Nucleonics.
ADP
Advanced Development Program. Honeywell term for a new system
architecture in the late 1970s.
AED
Algol Extended for Design. Language developed by MIT's Electronic
Systems Laboratory in the mid 1960s.
AEP
Advanced Engineering Program. A GE/Honeywell co-op program.
Selected students rotated through jobs in LISD while getting a
Master's degree.
AFDSC
Air Force Data Services Center. Located in the Pentagon, this site
had 5 systems: two were multilevel secure, and one was unclassified.
AIM
Access Isolation Mechanism. The underpinnings for multilevel
security. Produced by Project Guardian, and crucial in the eventual
B2 rating for Multics.
ALGOL 68
Done by HIS UK in the 1980s.
ALM
Assembly Language for Multics, which was supposed to be an oxymoron.
Multics' then-radical innovation of being implemented in a
higher-level language (see PL/I) relegated ALM, Multics' assembler,
to a place of strong official disfavor, and suggestions for
improvements to the assembler or its language were routinely
dismissed for many years, placing additional burdens upon them who
had to use it (e.g., page control, traffic control, BOS) for whatever
reasons. An integrated macro feature (Steve Webber's
macro-preprocessor MEXP, integrated by Greenberg and Morris, both
regular ALM users) did not appear until 1977 or so. ALM was also
used to define programs' data bases, as PL/I glaringly lacks the
ability to define globally-addressable static data objects. [describe
create_data_segment?]
ALM was Multics' second-generation assembler, the follow-on to EPLBSA,
written in FORTRAN, transliterated almost mechanically to PL/I (one big
structure for COMMON!), and improved very gradually in PL/I. [authors of
ALM?] [BSG]
AML
Author Maintained Library, stored in >aml.
AN61
The Multics Storage System PLM. AN series manuals were Program Logic
Manuals. Written by Bernie Greenberg.
anonymous user
User Control allows a project administrator to define an "anonymous"
user in a project. Such a user has no PNT entry and no password. A
process is created for the user when the enter command is given
instead of login. Anonymous users are usually put in some kind of
limited service subsystem (LSS) that does its own accounting and
passwords.
answering service
The facility in Multics that listens to all non-logged-in terminals,
accepts the login, enter, and dial commands, and logs in and creates
processes for users. This facility runs in the initializer process.
[TVV] The answering service was written as one huge, very complex
PL/I procedure (dialup_) managing a table (the "answer table") with
an entry for each comm line. Organized around "event-call" wakeups,
dialup_ was totally event-driven, much as the code at the core of
some of today's GUI paradigms, and the resulting morass of "state =
this", "next_state = that", etc., totally defeated all notions of
program-structure and control flow, rendering it a bear to understand
and maintain. These are deep issues about the cost of processes, and
not an indictment. Mike Spier and Tom Van Vleck created it, and Tom
Casey continued its improvement.[BSG]
AOS
Add one to storage, opcode on 600 and 6000 CPU's, including both
Multics processors. Although most frequently used for simple
arithmetic, including metering/instrumentation, this opcode utilized
read-alter-rewrite (RAR), an indivisible operation of the SCU. [BSG]
APL
A language, defined by Ken Iverson of IBM, that used many special
operators. There were two APLs for Multics: the first one done by
Project MAC folks, the second by Honeywell CISL. Used the Selectric
938 typeball.
Unbundled product.
appending mode The hardware mode of the 6180 and 645 processors where
2-dimensional addresses, consisting of segment number and offset in
that segment, are resolved via descriptor segment and page tables
into references to a virtual memory. See absolute mode. [BSG]
APU
Appending Unit. Part of a Multics CPU that did address
interpretation according to segment and page tables. The
corresponding entity on the 645 was called the "Base Frame".
archive
The archive command manages segments that consist of multiple
subfiles. It can add a segment to an archive, list the contents of
an archive, or extract a segment from an archive. Similar to the
UNIX tar command. [TVV] [Mention tape_archive also.]
One of the first of the world's bogus mini-file-systems, mechanisms for
storing many files in one (e.g., PKZIP, TAR, ARJ, etc.) because the
overhead of files is too great for the number of files desired. Multics'
archive command stores files intact in "archive" files; it does no
compression, and its only overhead info is an ASCII header preceding each
archived file, which starts with a form-feed, so it is possible to dprint
archives and even have the headers come out "nice"! Another motivation for
all bogus mini-file-systems is the use of tools to process (send, print,
copy, etc.) single files that are not proficient or perhaps efficient at
handling subtrees or other sets of files.[BSG]
ARCS
Academic & Research Computing Services, the application programming
organization at MIT's IPC.
ARDS
Advanced Remote Display Station, an early graphics terminal. Used a
Tektronix storage tube and ran over phone lines. Common hookup was a
Bell 202C modem, with 1200 baud computer to terminal and 150 baud
terminal to computer. Some models had a joystick.
ARPA
Advanced Research Projects Agency of the US Department of Defense.
This agency contributed substantial funding to MIT Project MAC for
the development of Multics. J.C.R.Licklider was working there and
championed this idea.
ARPANet
The network first constructed by ARPA, which decades later became
"the INTERNET". MIT's Multics was one of the very first sites on it,
and Multics's network implementation one of the very first. For the
first decade, very few Multicians paid attention to it at all, only a
small but dedicated crew of "network people" who foresaw what has now
indeed come to pass. [BSG]
ASCII
American Standard Code for Information Interchange. The character
set used in Multics. In 1965, this was a great departure; character
sets were much less standardized in the 60s. The 7094 used 6-bit
BCD, and CTSS on the 7094 used BCD with shifts indicated, the
"12-bit" character set, for TYPSET and RUNOFF. Multics was one of
the first systems to use upper and lower case letters freely.
ASEA
Multics customer. Sweden.
associative memory
Each 645 and 6180 CPU had a content-addressed memory to speed up
appending lookups. The most recently used entries in the descriptor
segment and page tables were cached in these high-speed circuits and
used when needed, avoiding one or two memory references.
AST
Active Segment Table. Hardcore table of ASTEs, one per active
segment. Upper part of the SST.
ASTE
Active Segment Table Entry. Contains a page table and some segment
attributes.
ASU
Arizona State University. Had a Multics for a while in the 80s.
audit
(1) The process of peer code review practiced at CISL.
(2) the audit_ IOSIM that logs
terminal I/O to a file. The attach_audit command sets up a process's
iograph to include an audit_ attachment.
Avon
Consortium of the Universities of Bristol and Bath. Operated AUCC,
Multics site.
B2
Orange Book (US government TCSEC) rating achieved by Multics.
backup
Dumping files from disk to tape. Done by a daemon process. The
Backup.SysDaemon ran incremental and complete dumps. See restor.
BASIC
Beginner's All-purpose Symbolic Instruction Code, a language invented
by Kemeny and Kurtz at Dartmouth. Multics had several BASIC
implementations; the final one was a compiler by Barry Wolman.
BCE
Bootload Command Environment. The successor to BOS.
BCO
Billerica Computer Oprerations. The division of Honeywell that built
the Level 6 minicomputer and the VIP7801. Used a Multics as its
software factory.
BCPL
Bootstrap Combined Programming Language. A language defined by
Martin Richards of Cambridge, for bootstrapping CPL, used for some
pieces of Multics such as qed and runoff, and an ancestor of the C
language.
Bell Canada
Multics customer. Had two sites, Toronto and Montreal.
binder
An alternative to the dynamic linker, the binder combines program
binaries into a bigger binary.
bit count
The file system stores a bit count for each segment and directory,
but attaches nohardcore meaning to this quantity. User-ring
programs, by convention, interpret the bit count as the length of a
segment in bits; on a directory, a non-zero bit count indicates that
the directory should be treated as a multisegment file.
block
"Block and wakeup" is one of two interprocess synchronization
mechanisms in Multics. A process "goes blocked" (i.e., into a
suspended state) awaiting any "wakeup" sent to it. A "wakeup"
identifies not only the process, but a "channel" on which it is said
to be woken up, and contains a 72-bit arbitrary datum. Received
wakeups for a given channel are "queued" for that channel. A process
can either go blocked "on" ("event wait", i.e., waiting for a wakeup
on) a given channel, or declare a callback procedure ("event call")
for a channel, a common way of implementing server-type software.
See notify. [BSG].
boot tape
A Multics Standard Tape (MST) from which the three "collections" of
segments of the supervisor (and a handful of other segments needed to
start up a Multics from scratch) were loaded into core, virtual
memory, and the file system, respectively. Since each of these
stages depended upon successive states of increased operability of
the supervisor, the technique of merely loading an "image" was not
available. The "bootload", or "bootstrap load" process really was a
classic "up by the bootstraps" endeavor: successive mechanisms of the
supervisor (e.g., segmentation, PL/I runtime, paging, dynamic
linking) would be made operative one by one in and by restricted
environments devoid of those features. Some of the steps, such as
the copying of unpaged segments into paged ones when paging had
become operative (done by "make_segs_paged", which Mike Grady
alexandrically renamed from "update_sst_pl1"), are mind-bogglingly
profound. The bootstrap process was known as initialization.
The first record of the boot tape was read into core by BOS, which
transferred control to it -- BOS was an afterthought, and Multics was
at first designed to have been booted on a bare machine. But in
fact, BOS passed an array of hardware configuration information and
software parameters (e.g., table sizes) read in from cards (the
config deck) necessary for Multics operation.[BSG]
In 1967, a "development run" involved generating a new system tape,
signing up for time on the 645, mounting the tape on the 645 and
booting it. The system would start to initialize, read collection 1,
sit for a while flashing the CPU lights, load collection 2, think
some more, and crash. The programmer would dump core on the printer,
find the problem, and repeat the process. [TVV]
bootload
To load software into a system and start it up. On the 645, pushing
the BOOT button on the GIOC booted from cards or tape, and Multics
System Tapes had a special self-loading first record. When BOS was
first written, it booted from cards and then the BOS BOOT command
booted MSTs. A warm boot of BOS, if it was already loaded on the
disk, required only a single card.
bootstrap1
The first program on a Multics boot tape. bootstrap1 is entered in
absolute mode. (On the 645, it paired the ABRs.) It then reads the
rest of collection 1, establishes a primitive appending environment
and stack, and calls bootstrap2, which prelinks collection 1 and
proceeds with initialization. Initially written by Nguyen Van Binh,
made to work by Noel Morris and Tom Van Vleck, and further maintained
and improved by many.
BOS
Bootload Operating System. A minimal, single-user, single-processor,
non-paged, entirely assembly language 645/6180 "operating system"
that was run before Multics came up and after it was shut down or
crashed. Part of the Multics project, and not used anywhere else,
BOS played no role at all while Multics was running, comprising only
a several-hundred word "toehold" to swap core with Multics when the
latter finally stopped running. BOS included commands to make and
restore disk snapshots, patch and dump virtual memory to the printer,
load device controller microcode and the like, and initiate the
bootload and/or ESD of Multics. Initially created on the 645 by Stan
Dunten, BOS was continued on the 6180 largely by Noel Morris,
although others contributed. BOS was later replaced by BCE. [BSG]
branch
The structure in a directory allocated for each segment or directory.
Sometimes extended in meaning to the object described by it, e.g.,
"there are three types of branches: ordinary segments, directories,
and links."
Brunel
Multics site: Brunel University (Uxbridge, Middlesex, England)
BSA
Bootstrap Assembler.
BTL
Bell Telephone Laboratories.
Bulk Store
Replacement for the firehose drum, this was a large bank of slow core
memory, accessed as if it were a drum.
Bull
Machines Bull, a French computer company originally associated with
GE, that eventually bought the computer division of Honeywell and ran
it as Cii Honeywell Bull.
C
In the late 80s, a C compiler was written for Multics.
cache
In 1974, the 6180 acquired an optional CPU cache. Like most else,
this Honeywell hardware innovation was not designed with Multics in
mind, and absolute data address was used as the key to the cache. As
in all caches, cached data in one CPU becoming stale when the "real"
data is modified by another must be addressed, as it were. Multics's
extremely multicious solution, which won Steve Webber and Hardware
Designer Riley Dobberstein a US Patent and a Honeywell Sweatt Award,
was to invent the "cache" bit of an SDW (implicitly inventing the
notion of "encacheability of a segment"), which prevents words from
shared, writeable segments or those with physical I/O going on (as
determined by software) from going into, or being sought in, the CPU
cache. Greenberg invented a scheme for keeping writeable user
segments encacheable while they are not actually being shared,
including coordinating the notions of "shared between CPU's" and
"shared between processes".[BSG]
CACL
Common ACL. Up to the early 70's, Multics directories had an
additional ACL whose contents were effectively appended to that of
each segment within it. This was seen as an easy way to manipulate
"default access" in a directory. But not only did this render the
computation of effective access unduly complex, but it led to
surprises when CACL's were changed when segments already existed.
Hence, this scheme was replaced by IACLs.
call bracket
The range for rings which can call a given segment as a gate. If a
segment's ring brackets are 0, 0, 5, the call bracket is rings 0 to
5.
call/save/return
The machine language sequences for inter-subroutine call depend on
the stack discipline and the subroutine linkage conventions. These
sequences were conceived of as EPLBSA macros by Bob Graham. When
threaded code was introduced into the version 2 PL/I compiler, these
sequences were moved into pl1_operators_ and the ALM macros changed
to reference an operator segment. Later, a global change was made to
stack discipline for efficiency, without requiring any (normal)
program to be recompiled.
Cambridge Project
An MIT-Harvard social science data management project. The Cambridge
Project was criticised by campus radicals during the Vietnam War
days, because it was taking DoD and CIA money. It produced the
Consistent System.
canonicalization
Multics converts terminal input lines to a standard form, so that
lines that appear identical are identical in storage.
Cardiff
Multics site: Cardiff Joint Computing Centre (Cardiff, Wales)
CCVR
Multics site: Centre de Calcul Vectoriel pour la Recherche, Ecole
Polytechnique (Palaiseau, France)
CiiHB
See Bull.
CICB
Multics site: Centre Interuniversitaire de Calcul de Bretagne,
Universite de Rennes (Rennes, France)
CICG
Multics site: Centre Interuniversitaire de Calcul de Grenoble,
Universite de Grenoble (Grenoble, France)
CICRP
Multics site: Centre Interuniversitaire de Calcul de la Region
Parisienne (Paris, France)
CICT
Multics site: Centre Interuniversitaire de Calcul de Toulouse,
Universite Paul Sabatier (Toulouse, France)
CIRCE
Multics site: Centre InterRegional de Calcul Electronique (Orsay,
France)
CISL
Cambridge Information Systems Laboratory. Pronounced "sissle." The
group at (GE, Honeywell) that participated in the development of the
Multics operating system, and led it after BTL and Project MAC
dropped out. Originally housed on the 7th floor of 545 Tech Square;
moved to 575 Tech Square about 1970; moved to Kendall Square in the
80s; when the people were moved to Billerica in the late 80s it
wasn't called CISL any more. Had its own 6180 system. About 60
people worked at CISL.
CL
Multics site: Centre Interuniversitaire de Traitement de
l'Information, Universite de Lille (Lille, France)
clock
The original 645 shipped with a separate box that was a microsecond
realtime clock with the ability to interrupt any CPU. On the 6180,
the clock moved into the SCU and didn't take up a port. The calendar
clock read by the RCCL instruction was 52 bits (lower).
CNET
Multics site: Centre National d'etude sur les Telecommunications
[CNET] (Issy, France)
CNO
Corporate Network Operations. Honeywell site in Minneapolis, MN.
COBOL
The Multics COBOL compiler was done at Honeywell Billerica and shared
internal data structures and code generator with the Multics PL/I
compiler.
combined linkage segment
A per-ring segment that contains the LOT, the ring's static data,
outbound links (snapped and unsnapped), and entrypoint names.
computer utility
A computer, its software, and staff set up to provide 24-hour service
for all of a community's information needs, the ancestor of the
"Information Highway". Multics was envisioned as quite this, a
"Multiplexed Information and Computing Service", to be present,
reliable, powerful, and all that is needed as an information resource
for a large number of people, all the time. This was radical at the
time, when computers were viewed mainly as tools and toys for
"scientists". [BSG]
collection
A Multics boot tape contains three logical groups of segments called
collections. Each collection is read in and then run, to bootstrap a
more complex environment for loading and executing the next
collection.
command
A program designed to be invoked by typing its name at a terminal.
Multics commands are ordinary user programs, and what is more,
ordinary PL/I procedures. Commands and "subroutines" are
indistinguishable at the PL/I and dynamic linking levels. Although
this reduces the number of search mechanisms, it rarely turned out to
be useful, as calling a command as a subroutine or vice-versa,
although fully possible and often done in kludges, presents all kinds
of UI problems. The proper handling and diagnosis of missing,
malformed, or non-string arguments makes the passing of command
arguments as actual parameters a poor idea, and the current C
"argc/argv" scheme, an outcome of Multics's experience, is one
correct solution.
Correct handling of the star convention and equal convention are not
so easy, though, and the seemingly-obvious solution of relegating
that task to the shell (or "command processor") is fraught with
well-known dangers whose horror stories adorn the landscape of UNIX
critiques.
Multics commands have long names and short names: "list" has "ls", "copy"
has "cp", and "move" has "mv," as well as "page_multilevel_meters"
having "pmlm". The original convention for short names is attributed to
Don Widrig.
Although there were many conventions of name syntax as time
passed, short names were always an addition to long names.
UNIX's "tribute" to Multics of "keeping" "ls", "cp", etc., while
throwing out all long names is in fact a misunderstanding bordering on
a perversion. [BSG]
command language
The Multics command language derived from the CTSS language, with
ideas added from BESYS and TRAC. The listener reads lines from the
input stream and passes them to the shell for execution.
command processor
See shell.
compose
Multics text formatting command, successor to runoff. Written by Ed
Wallman of Honeywell Phoenix. Unbundled product.
config deck
An array of card images read by BOS and passed to Multics
initialization, describing the number and sizes of memories, number
of processors, peripherals and their channels, etc., as well as the
sizes of critical tables (such as the SST) to be created by
initialization. Ultimately, BOS acquired the capability of keeping
these images on tape or in its own disk partition, not needing actual
cards.
The cards, or card images, were parsed by an interesting BOS routine
("scan") first written by Stan Dunten, that determined into what to parse
a datum (e.g., 4-character string, octal number, decimal number, letter)
by looking at the datum itself, storing one-word "parsed" data in one
array and "data types" in a parallel array, very much like a LISP
reader.[BSG]
Consistent System
Social science data manipulation subsystem built by MIT's Cambridge
Project, architected by John Klensin.
continuum
Bulletin board program that ran on Multics in the late 70s. Ancestor
of forum.
core
Main storage on the 645 was really core memory. Several different
manufacturers produced it: Lockheed, Fabritek, who else.. I remember
running memory diagnostics that printed out FABRITEK WCCP PATTERN
TEST, WCCP meant "worst case (something)." There was a problem in
1966 with non-plated sense wires on core planes from some
manufacturer, forget who, that for a while caused the 645 to burn out
a core assembly a week. Worked fine in Arizona's dry air, but
Boston's salty & polluted atmosphere was too much for them.
core metering
Memory usage metering was described by Bob Frankston in his
undergraduate thesis. The units of memory occupancy,
page-milliseconds, are familiarly called "Frankstons."
cow's stomach
The "Coreadd queue" of Release 6.1 and afterward. This creation of
Bernie Greenberg's was a solution to the problem of multi-CPU
contention on the "page table lock" (PTL), a "spin lock" on the
entire paging database, which had become a severe performance
bottleneck. By the nature of the beast (see wired), disk interrupts,
as they arrived at page control's interrupt side from the disk DIMs,
had to spin on this lock, too. The "Cow's stomach" was a queue where
the interrupt side saved the results of completed disk operations for
later digestion by page control, viz., when the PTL was unlocked.
The algorithm defining the interaction of manipulating this queue with the
locking and unlocking of the PTL was quite complex, and took Greenberg
some time and effort to devise; when he had done so, he posted outside his
door a hand-drawn flowchart replete with starfish and keyhole shapes and
other innovations to symbolize non-traditional flowchart steps. The
overall shape of a delimited loop representing area protected by a new
lock resembled a stomach, and the complexity made many people ask if it
was "a cow's stomach." As it happened, the functionality of the thing very
much resembled that of a ruminant's stomach-complex, and the name stuck,
and was even used for a similar mechanism in later operating systems of
other vendors. [BSG]
crawlout
When a signal is raised in an inner ring routine called from an outer
ring, the signal is reflected back to the caller via a crawlout.
Ring 0 handles these specially, unlocking and salvaging before
leaving ring 0.
Cray Station
Usually titled Multics Cray Station (although the acronym MCS was
already taken). Written by Warren Johnson, it made Multics look like
an RJE station for a Cray with job, file transfer, and print queues.
Used by Ford (it was the reason for obtaining the 3rd Multics system)
and a UK site. [BWS] The original Cray XMP Ford had ran COS (Cray
Operating System) and required a front-end computer to submit,
control, and retrieve jobs. The cray station software on Multics
allowed us to use Multics as a front-end computer for the Cray. [VS]
Credit Lyonnais
Multics site: Credit Lyonnais (Paris, France)
CS
see Consistent System.
CSC
Computer Sciences Corporation. This contractor installed 4 systems
for Naval War Games System.
csort
Cygnus Sort, a more performant reimplementation of the standard
Multics sort/merge product by Cygnus Cybernetics Corp (Jim
Homan). [BWS]
CTSS
Compatible Time Sharing System. This 7094 operating system was
created at MIT Project MAC and first demonstrated in 1961. It was
used as the programming and debugging tool during initial Multics
programming and bringup by Project MAC, GE CISL, and BTL personnel.
In some sense the intellectual offspring of CTSS, Multics was
conceived as the next step into the future of multiple-access
computing. Many of the MIT Multics principals had worked on the
earlier system.
CU
Control Unit. Instruction sequencing, fetching, and decoding unit of
a Multics CPU.
daemon
A beneficent spirit. A process, not associated with a human
operator, that runs all the time and waits for requests to do
something for a user. Name usually credited to Peter Neumann.
Datatran
Cambridge Project feature?
DCC
Data Communications Corporation. Multics customer, in the business
of billing advertisers for TV commercial charges.
DDDS/ORAE
Canadian DND Multics site.
debug
Multics source-level and process-level debugger, initially written by
Steve Webber. Later partially replaced by "probe", which only has
source-level capabilities, but was more end-user oriented.
DBR
Descriptor Base Register. Sometimes Descriptor Segment Base
Register, DSBR. The appending unit register that contains the
absolute address of the descriptor segment for the processor and thus
the hardware address space of a process.
deciduous
A neologism of B. Greenberg's for branches that lose their pages
(Fr. "feuille", "leaf") when the "season" (running of Multics) is
over. This was new to NSS, and was the method of management of that
subset of paged supervisor segments that had to appear in the file
hierarchy, but also had to be loaded, paged, and operative during
initialization before the file system was "up" in that bootload. The
technique was to withdraw the pages of these segments from the same
per-bootload pool as used by the rest of the supervisor, which
required special care to make sure that no attempt was ever made to
return them to the file system. Unlike many colorful neologisms of
the time, this one made it all the way into the official
documentation. [BSG]
descriptor
(1) contents of an SDW. (2) Single word that described an operand of
an EIS instruction.
descriptor segment
The array of SDWs (segment descriptors) that totally define a
process' address space as currently available to the hardware without
segfaults. This array itself is in all respects a segment, and (by
convention) is segment 0 of the process it defines: its first element
is thus an image of the DBR that describes it. Supervisor segments
precede all other segments; then follow stacks, then all segments
initiated and terminated by supervisor calls. All of the SDWs for
wired segments are in its first page; therefore, that page has to be
wired before a process can run, and that page and the first page of
the PDS of a process are wired before a process is made eligible.
The hardware can take page faults on the rest of the descriptor
segment during the address formation process, and this case is
differentiated by bits in the SCU data.[BSG]
DFAST
FAST subsystem with Dartmouth conventions.
dial
The answering service connects a TTY channel to an existing process
if the dial command is issued instead of login. This facility is
used to support transaction processing.
DIM
Device Interface Module. The Multics I/O Switch ios_ supported
device-independent operations on data streams, something like the
UNIX Streams facility. The device-dependent operations were
performed by one or more DIMs in the I/O graph. There were two kinds
of DIMs: terminal DIMs actually controlled a physical device. Many
of these were in the hardcore. Non-terminal DIMs performed a
transformation on their input and invoked the I/O switch again, like
Fenichel's famous Pig Latin transformation. ios_ was an early
instance of polymorphism, supported by calling convention rather than
by language. The term DIM is also used for the hardcore programs
that control physical devices, even if they are not invoked via the
I/O switch, for example, the disk DIM.
directory
A file system entity that contains <a href="#segment">segments,
links, or other directories. Directories are organized into a
tree-structured naming hierarchy. All directories are stored on the
RLV. The topmost directory is called the root.
Discourse
Multics social science application written at MIT by Wren McMains.
Disk
Not "disc," those are Frisbees. (more, list models and capacities?)
disk quota
Multics enforced disk usage quotas at page fault time. A user cannot
grow a segment even temporarily past his or her quota for the "quota
directory" in which the segment resides. Some directories don't have
quotas, and charge their usage to the closest parent directory that
has a quota. Master directories are quota directories that have a
logical volume attribute different from their parent; they draw their
quota from a special segment that specifies the total quota a user
can allocate on a logical volume.
DN30
Datanet-30. A communications front-end processor.
DN355
Datanet-355. A communications front-end processor. Ran MCS.
DN6670
Datanet-6670. A communications front-end processor.
DND
Canadian Department of National Defence. Had two Multics systems.
DOCKMASTER
Unclassified Multics system operated by the NSA in Linthicum, MD.
Used as a communications tool among security researchers, lots of
forum activity.
dprint Delayed print. Pronounced dee-print. The command that queues
a file for printing on the line printer by the "I/O Daemon",
IO.Sysdaemon. Listings produced by the printer daemon are also
called "dprints." See link.
DPS
Distributed Processing System. Honeywell added this prefix to the
names of a lot of machines in the late 70s, including the DPS-68 and
the DPS-8/M.
DPS6
Another name for a Level 6.
DPS6plus
Version of the Level 6 that ran a secure system.
DPS8
Honeywell early 80s name for its mainframe line. Multics machines
were called DPS8/70M, DPS8/62M, DPS8/52M.
DPS88
Later name for the Honeywell ADP and Orion machines. Never ran
Multics.
DPS90
Even later Honeywell processor line. Never ran Multics.
Drum
See Librafile.
DS 10
Early disk unit. I think these were the ones operators had to "milk"
condensation from the vacuum lines with a special bottle.
DSEG
Jargon for descriptor segment.
DSS191
Disk unit.
DSU170
Disk unit, used on Multics in the early 70s.
DSU270
Disk unit, used on Multics in the early 70s.
DTSS
Dartmouth Time Sharing System. Created by Kemeny & Kurtz at
Dartmouth. Ran on a GE635 and supported many more users than CTSS or
Multics per CPU, but with a more limited programming model. Multics
had several DTSS simulator environments. See also BASIC and FAST.
dump
BOS command that printed an octal dump (of selected segments after
Multics had crashed, or during system debugging). Descended from
John Gintell's dump program that loaded from cards.
DVCP
Deer Valley Computer Park. Generic name for the complex of Honeywell
buildings in Phoenix at Thunderbird and the freeway, housing LISD
headquarters and manufacturing.
dynamic linker
Multics facility that resolved subroutine linkage on the fly, at call
time.
dynamic reconfiguration
Multics facility that allows the system to add and drop hardware
without shutting down. Roger Schell's thesis was the basis for this
feature. Integrated with test and diagnostic stuff. I/O
reconfiguration was added late in the life of the system.
echo negotiation
A scheme (1979) for conditional character echoing by MCS, echoing
"printable" characters until the receipt of a "break character" as
defined by software and synchronizing that usably with Multics
software, devised for Emacs by Bernie Greenberg to ameliorate the CPU
load impact of Emacs. Having since spread to the rest of the Emacs
world and since denounced as "not the way to go" (as opposed to just
having enough CPU resources) by Craig Finseth ("The Craft of Text
Editing"), this scheme did wonders towards its goal at the time.[BSG]
edm
Multics command for editing files. Written by Steve Webber. A
descendant of Jerry Saltzer's edl command on CTSS.
EIS
Extended Instruction Set. A suite of instructions added to the 645
set when the 6180 was introduced. These are business instructions,
that operate on multiple words or streams of various-sized bytes.
Requiring several words each and their own data-descriptor
architecture, EIS contributed significantly to the cost, size, and
complexity of the (non-microprogrammed) CPU. Although ideally suited
to PL/I string manipulation, EIS' need for restartability around page
faults was a constant source of bugs and failures. Of the 100 or so
boards in a 6180 CPU, over 30 were EIS. [TVV, BSG]
ELF
Multics site: Centre de Recherche ELF (French oil company) (Pau,
France)
eligible
Eligible for multiprogramming. The various scheduling algorithms
over the course of time controlled which processes become "eligible"
based upon their time since last interaction, approximate working
sets, membership in load control groups, and the like. In order to
make a process eligible, the first page of its PDS and of its
descriptor segment has to be wired: making them so is called loading
the process, and they are unwired when it loses eligibility
(unloading). Since this potentially requires I/O, the decision to
make a process eligible has finite cost and delay. When a processor
seeks candidate processes to run, as in real life, only those
eligible and loaded qualify. The idle processes are always thus.
See scheduler and traffic control. [BSG]
Emacs
From, "Editing MACroS", a video editor derived from Richard
Stallman's editor in TECO macros of the same name. Bernie Greenberg
began Emacs in MacLisp in 1978. Multics Emacs represented Multics'
first venture into the modern UI world of managed screens, WYSIWYG
editing, and character-at-time I/O and its first major offering not
in PL/I, and constituted one of the first wholly unforeseen internal
developments in the life of the product. Its use of Lisp as
implementation and extension language was the ultimate inspiration
for the use of Lisp by GNU Emacs. MCS enhancements and a video
system followed in its tracks. Multics Emacs was always spelled
"Emacs", not "EMACS", on MULTICS. [BSG]
enter
Answering service command to log in an anonymous user. The enterp
command supports anonymous users all of whom have the same password.
EOP
Executive Office of the President. A benchmark Multics won, but
didn't get the sale on. Otherwise Oliver North's e-mail would have
been on Multics instead of PROFS.
EPL
Early PL/I. This compiler was done at BTL by Doug McIlroy, Bob
Morris, and others when it became clear that Digitek wouldn't produce
a compiler. EPL was written in TMG and was incredibly slow.
EPLBSA
EPL BootStrap Assembler. EPL compiled into EPLBSA, which was then
assembled. Written by Bill Poduska in FORTRAN.
EPPBP
6180 opcode 352, "effective pointer to pair bp ((utility)
base-pointer)" (EAPBP on the 645), the most common instruction in
Multics code. Not different in concept than a 360/370 LA or an Intel
LEA, this instruction placed its effective address, segment, word,
ring, and EIS bit offset, in pointer register 2 (bp; there were also
eppap, eppab, etc. for the other seven). The power of this
instruction, and its claim to fame, is its interaction with
indirection: the standard way of loading a pointer in memory (ITS
pointer) into a pointer register is not to use a "load pointer from
memory" instruction (the 6180 had one, but it saw no use), but to
indirect through that pointer in memory, and load the resulting
"effective pointer" into that register. The computation of effective
ring (see TRR) during the indirection process, as well as the
possibilities of an intersegment link being used as an indirect
word-pair or further indirection and every other aspect, side-effect,
and possibility of the indirection process seemed always to be
appropriate for every pointer load. [BSG]
EPSHOM
Multics site: Etablissement Principal du Service Hydro-Oceanique de
la Marine (Brest, France)
equal convention
A command that operates on related filename arguments should
implement the equal convention. For example, the rename command
operates on pairs of arguments. The equal convention specifies how
equal signs in the second element of a pair are replaced by
components of the first element. A user can say rename fred.*.pl1
==.old See star convention.
ERF#
Error Report Form # - report of a system crash, at the MIT Multics
flagship/development site. Crashes were identified by erf #. "erf"
was also the verb in ifd to load up an fdumped crash image. [BSG]
ESD
Emergency ShutDown. This operation is invoked after a system crash.
The operator manually forces a transfer to a well-known location,
where special code flushes the virtual memory to disk. Organizing
storage system data structures such that this could be done in a
consistent and reliable fashion was a major feature of release 6.0.
ESL
Electronics Systems Laboratory. An MIT group that did research in
computer assistance to manufacturing. Produced the APT and AED
languages, and the Kludge.
exec_com
Multics command that executed a script of commands from a file, with
argument substitution.
execute bracket
The range of ringss that can execute a given segment. See ring
brackets.
extended access
?
FAMIS
Feature of MR11.0. File Access Methods and Integrity Services. it
was an early name for the Data Management (DM) version of MRDS that
supported transactions and before journalling. Beta tested at Ford
in 83/84. [BWS] This is a file access method that supports atomic
transactions (including commits and rollbacks). It was designed to
provide MRDS with transaction capabilities. [VS]
FAST
A DTSS simulator.
fault
A processor generated exception causing a diversion of control
through a fault vector, for any reason except an interrupt. Page
faults, segfaults, bad instructions or out-of-bounds references and
the like are all common faults. (There is no notion of "failure").
BOS did not take or process any type of faults. When Noel Morris
made BOS tapes self-booting (see Zero Six Dog), though, the
coup-de-grace was the processor taking a horrible "trouble fault" by
executing one of the magic constants on a "Multics Standard Tape"
(see MST) and Noel's code handling it, not unlike the swift whap on
the buttocks of a new-born babe. But field engineers not savvy to
Multics culture were unimpressed that "Multics starts up by taking a
fault." (setting the "stop on fault" CPU switches up was part of
their S.O.P.) [BSG]
fault vector
A set of 32 instruction pairs in a fixed location specifying CPU
handling of the 32 processor faults. Rather than specifying a
location to transfer to, the 600/6000 architecture specified a pair
of instructions to be executed out of line by the control unit, one
of whose tasks was "executing pairs of instructions, no matter how
obtained." The first instruction was invariably SCU, and the second,
"return", because the Multics return instruction also reloaded the
condition code register, which in the case of interrupt vectors was
ingeniously used to stash the interrupt number! [BSG]
fdump
BOS command that took a core dump into a disk partition.
Field Engineers
The FEs were Honeywell employees who installed the big iron and fixed
it when it broke. They were an incredibly dedicated group of people,
who worked long and strange hours, and responded without complaint to
panic calls when the machine wouldn't work. They dealt cheerfully
with an exotic, undocumented CPU built far away, running software
that changed all the time, and kibitzing by a lot of people who
provided unhelpful theories and lots of pressure, but not enough
recognition.
File manager
See vfile_.
FIM
Fault Interceptor Module. This program is invoked whenever the
hardware encounters a fault. It manages machine state and calls the
appropriate routine. Harlow Frick, Noel Morris, and Tom Van Vleck
worked on the original version. In later years, there were actually
two FIMs, "wired_fim" and "fim", for faults whose handling has to be
done in page-locked environment and not.
Firehose drum
See Librafile.
FJCC
Fall Joint Computer Conference. There used to be two big conferences
a year, one in the spring and one in the fall. Multics was first
announced at the 1965 FJCC.
FL
Function Language. An assembler that Tom Kinhan of GE was working on
but which was never made part of the system.
Flag Day
Any software change that is neither forward nor backward compatible.
Named after a change to Multics scheduled for June 14, 1966, when the
values of the ASCII character set were switched around.
FNP
Front-end Network Processor. Also called FEP. See SFEP.
Ford
Big Multics customer.
format_pl1
A PL/I indenting program with many features, options, and control
arguments, written by Monte Davidoff.
FORTRAN
Multics had two fortran compilers. The version 2 compiler shared a
back end code generator with the PL/I compiler.
forum
Bulletin board system. A descendant of continuum.
Unbundled product.
FSDCT File System Device Configuration Table. Held file system
parameters and volume bit maps (until the new storage system).
FSIM
File System Interface Module.
FSO
Federal Systems Operation. The division of Honeywell that handled
government contracts, sales, etc.
F&T
Restaurant in Kendall Square, Cambridge, where Project MAC Multicians
used to go to lunch. Not to be confused with the diner next door of
the same name.
gate
A segment that allows transfer of control between rings in a
controlled fashion. Each gate segment has a vector of entries at its
start. Now called "call gate" in the Intel world. Originated on
Multics.
Gateway
Hardware project to build an ARPANet gateway, done at Honeywell
Phoenix in 1979.
GCOS
Formerly GECOS, General Electric Comprehensive Operating System.
After the merger, the "electric" was dropped. A batch processing
system comparable to IBM IBSYS. More efficient that OS/360, but
limited for many years to a single address space. Unbundled product.
Throughout Multics's life as a product it battled with GCOS for
Honeywell resources and support of every kind.
GCOS simulator
Also called the GCOS Environment Simulator, GES. Allows a user to
run a GCOS program inside a single segment in Multics, intercepting
the MME instructions that these programs issued and calling on
Multics to e.g. open files or print output. Similar in many ways to
(the much later) Virtual 8086 mode on the Intel architectures.
GE
General Electric Co. Manufactured toasters, jet engines, nuclear
power plants, and, for a while, computers. Sold computer division to
Honeywell in 1970. Joke from that time: GE executives had a big
meeting in Florida to decide how to become number two in the computer
business (this was in the days when it was "IBM and the seven
dwarfs"). The solution they came up with: buy IBM and manage it for
6 months.
GEBUG
Debugging facility for 6.36 programs. Ran on CTSS. Don Wagner and
Steve Kidd worked on this program.
GEMSOS
Gemini Computer's secure OS, influenced by Multics.
Genstat
Statistical stuff done by Douglas Clark at Bath?
GESHUA
Pre-merger name for HLSUA.
GIM
GIOC Interface Module. The code that operated the GIOC in the
original 645 Multics.
Gimpelize
To arrange the items in a PL/I data structure so that no padding is
generated, by grouping them with all the items of highest boundary
alignment first, then next highest, and so on. Named after Jim
Gimpel of BTL, who stated the rule.
GIOC
Generalized I/O Controller. This box did all the I/O for the 645.
Some programmers pronounced this by spelling it out, but the field
engineers tended to say "gee-yock."
Glim
Statistical stuff done by Douglas Clark at Bath?
GM
General Motors. Big Multics customer.
GPM
General Purpose Macrogenerator.
graphics
Multics graphics were heavily influenced by the Electronic Systems
Laboratory design for the Kludge on CTSS. The Multics graphics
system created a device independent representation and then
translated it to device codes at display time. It was intended that
this should work as well on an ARDS as on a vector scope.
GTSS
GCOS Time Sharing System. A TSO-like timesharing environment within
GCOS. Simulated on Multics in the GCOS simulator. "gtss" was a
Multics command.
Unbundled product.
Guardian The CISL/MITRE/USAF project that added AIM, the Access
Isolation Mechanism, to Multics.
hardcore
That portion of the Multics that is loaded from the boot tape and
runs in ring 0; the supervisor, the operating system kernel. The
common phrase "hardcore supervisor" (hcs) is essentially redundant.
[BSG]
hardcore partition
A partition, on the RPV, used for the pages of the segments that
constitute the supervisor, not actually part of the user-visible file
system.
hardware monitor
Honeywell had a device that hooked into the backplane of a 6180 for
measurement purposes, called the "yellow submarine." They brought it
out to Cambridge for a while.
HASP
Houston Automatic Spooling Program. An IBM Type II program that
managed input and output queues and RJE for big 360s. Multics had
some software to talk to HASP, pretending to be an IBM 2780
(reader/punch device), over a bisync line.
hcs_
Gate into the hardcore supervisor. Most Multics supervisor functions
available to ordinary programs are provided as entrypoints in this
segment, for example the file system (hcs_$initiate). Other gates
are phcs_ and hphcs_.
HEALS
Honeywell Error Analysis and Logging System.
help
Tom Van Vleck wrote the first Multics help facility. Over time this
code became more and more elaborate. Similar to the UNIX man pages,
but the info segs that the help command references are automatically
extracted from the runoff source of the Multics commands manuals.
hierarchy
The Multics file system names files with multi-part names separated
by > and organized into a tree-structured hierarchy. Unlike files in
the UNIX file system, a Multics segment or directory is a child of
only one parent.
HISCAN
Honeywell Information Systems, Canada. A marketing organization.
HISLTD
Honeywell Information Systems, Limited. Marketing organization for
the UK.
HISUK
Another name for HISLTD.
HLR
Hoffman-LaRoche. Multics customer.
HLSUA
Honeywell Large Systems Users Association. Pronounced "h'lashua".
HOPL
History of Programming Languages. ACM conference.
hphcs_
Highly Privileged HardCore Supervisor, pronounced "h'putschkiss",
after Greenberg. A gate which allows arbitrary patching of the
supervisor, bringing the system down, and control of critical
parameters. Access to this gate is controlled by an ACL, like access
to all segments in Multics. Anyone who "has hphcs" is in effect what
is now known as a super-user. [BSG]
HRX
Internal Honeywell codename for a machine never built.
IACL
Initial ACL. The successor to the CACL scheme, The initial ACL was a
"default ACL" to be used as the ACL for new segments in the directory
(there is a separate "Directory IACL" for new subdirectories). From
that point on, changes to the IACL had no effect on already extant
segments -- access is determined by a segment's ACL alone. [BSG]
idiotic
The EPL compiler produced spectacularly bad code for some kinds of
structure references. Jim Gimpel and Don Wagner looked at these
problems and divided declarations into "synchronous," "asynchronous,"
and "idiotic" references, depending on whether an array of items was
naturally word-aligned, was some submultiple of word-aligned, or was
incommensurate with the word size. For example, an array of 37-bit
items is idiotic, an array of 36-bit items is synchronous, and an
array of 9-bit items is asynchronous. The EPL compiler was modified
to tag all references with this classification, in a comment, in the
generated EPLBSA code. An early version of the KST had an idiotic
declaration, and each reference to an element of it generated more
than a whole page of assembly code from a single EPL statement.
idle process
Multics creates a dedicated process for every CPU, all of whose code
and data are wired. Called the idle process for that CPU, the
scheduler gives a CPU to its idle process when there is nothing else
for that CPU to do, i.e., no other process for it to run, so it can
be so that every CPU is running one and only one process at any time.
A ward of both birth and death, a CPU's idle process is the place
where it is started when dynamic reconfiguration adds it to the
system, and where it goes when it is to be deleted. Making the
bootload CPU act in a fashion consistent with this (cf. Adam's navel
in classic art) is a major prestidigitation of traffic control
initialization. The idle process flashed the CPU accumulator lights;
Noel Morris made it rotate the lights like a string of pearls,
rolling one bit at each dispatch into it. The heart of the idle
process' code is a DIS (Delay until Interrupt Signal) instruction.
[BSG]
ifd
Multics tool written by Bernie Greenberg in LISP that looked at a BOS
fdump, interpreted its contents, and allowed inspection of system
data structures. Inspired by Steve Webber's "ol_dump". Although ifd
was never a product (in part because of its being written in an
"unofficial language", MacLisp), it enjoyed widespread use. Replaced
by analyze_multics (azm).
IMFT
Inter Multics File Transfer.
IMU
Information Multiplexer Unit. A later, programmable version of the
IOM. Supported in MR12.0.
IN
Industrial Nucleonics. Multics customer. Later called AcuRay.
info seg
The help command prints out information from segments with the suffix
.info, called info segments. The system info segments are kept in a
special directory whose pathname I forget. The check_info_segs
command checks the date modified of segments in this directory, and
can perform a specified action on files modified since a date
contained in a user profile segment. There was also a facility
called info created by Charlie Clingen, which printed out information
from a tree-structured document.
initialization
The software mechanisms by which the Multics supervisor was loaded
and started from the boot tape and the system brought up. [BSG]
initializer
This process is manufactured at system startup by patching the system
tables to make it appear that a process is running. The initializer
process then completes Multics startup and runs the answering service
and message coordinator.
initiate
Said of a segment. Also "to make a segment known" (to a process).
To make the supervisor call (or as a side-effect of dynamic linking)
that associates a segment number with a file in the file system by
making an entry in a process's KST. From that point on, references
to that segment number become references to that segment, the
fundamental illusion of the Multics Virtual Memory. On Multics,
instead of opening files, a user initiates segments, and all the rest
is magic [BSG].
INRA
Multics site: Institut National de la Recherche Agronomique (Jouy en
Josas, France)
INRIA
Multics site: Institut National de la Recherche en Informatique et en
Automatique [INRIA] (Rocquencourt, France)
INSEE
Multics site: Institut National de la Statistique et des Etudes
Economiques (Paris, France)
INSEL
Multics site: INSEL, CNI Aix-en-Provence (Aix-en-Provence, France)
interrupt
The 645/6180 CPU has a separate set of 32 interrupt vectors and fault
vectors. Interrupts are always generated external to the processor,
by the System Control Unit (SCU), in which the interrupt might have
been "set" by another processor or the I/O box (see GIOC, IOM).
Interrupts are only recognized during instruction-pair fetches, not
in mid-instruction. The interrupt mask is not in the processor, but
in the port on the SCU to which the processor is connected.
Inter-processor, or even looped-back, interrupts generated by
processors are used to take processors on and off the system, crash
or shutdown the system, and send IPS signals to running
processes.[BSG]
ioa_
Standard Multics output formatter, ancestor to UNIX printf, invented
by Stan Dunten as part of BOS, and then made the basic output call
for all standard programs.
IOCT
I/O Command Translator. In 645 Multics, a generalized system for
managing I/O.
I/O Daemon
The I/O daemon process runs all the printers and card equipment. It
manages print queues and notifies users when it has done something
for them.
IOI (ioi_)
I/O Interfacer. A unique facility in 6180 Multics that allows any
user granted the appropriate access to actually run the physical I/O
of hardware devices directly to and from his or her segments. IOI
relies on the protection (base and bounds) registers of IOM channels,
and page control services for temporarily locking pages in core at
absolute, contiguous addresses as required for such use. The printer
and backup daemons as well as On-line T & D use it. One of Noel
Morris' proudest masterpieces. [BSG]
IOM
Input/Output Multiplexer. Replacement for the GIOC, except that IOMs
didn't have terminal channels, so each system had to connect a DN355
to the IOM.
ios_
I/O Switch. The original model for UNIX streams. ios_ mapped
"stream" names into what are now called method tables by string
lookup on each call. The table for each switch was the set of entry
points of a DIM. Among the supported operations were synchronous and
asynchronous reads and writes and controls, and the ability to define
one stream as a synonym (i.e., front) for another. Replaced by
iox_.[BSG]
IOSIM
I/O Switch Interface Module. See iox_.
IOTC
I/O Table Compiler. In 645 Multics, a tool for generating device
descriptions for the IOCT.
iox_
I/O Exchange. the MR1.0 follow-on to ios_. iox_ combined the
performance-directed move to referencing stream method tables by
pointer as opposed to string name with a redefinition of the set of
methods to more exactly map the repertoire of PL/I I/O. As part of
the package, some capabilities, such as asynchronous I/O, were lost,
a change many saw as gratuitous and ill-advised. As a result, a
vestigial ios_ had to be kept around indefinitely to support the
asynchronous ARPANet DIMs. iox_ DIMs are called IOSIMs. iox_ was
the work of Don MacLaren and Max Smith.[BSG]
IP
Multics site: Institut de Programmation (Paris, France)
IPC
(1) Information Processing Center. MIT organization that ran the
campus computer center. (2) Inter-Process Communication. The
facility for interprocess queueing and transmittal of wakeups and
associated 72-bit data through a system queue.
IPR
(1) Independent Project Review. A Honeywell management custom, in
which people from outside a project would study it and report the
risks. (2) Illegal Procedure. Subclass of 6180 processor faults.
IPS
(1) Information Processing Services. MIT organization, next higher
assembly to IPC, also included various other campus computing
facilities such as Nuclear Science computers. (2) Interprocess
Signal. An asynchronous interrupt caused by another (privileged)
process.
IRIA
Multics customer.
IRT
Multics site: Institut de Recherche des Transports (Arcueil, France)
ITS
(1) Indirect To Segment. 635/645/ 6180 indirect words contain a
"further indirection tag", which allows for iteration of the
indexing/indirection process after the address in the word has been
picked up. The Multics processors added a feature whereby the
appending unit watches the pike as these words come by, and if this
"further indirection" field of an even-addressed word contains octal
43 ("ITS"), hijacks it before it even gets to the CU, interpreting
its "address" field as a segment number (of the TPR) and passing on
the odd word of the pair on to the control unit in its place. The
net effect is that the word-pair can be viewed as a segment-word
"pointer pair", a pointer to a location in two-dimensional virtual
memory, and this pair of words, referred to as an "ITS pair" or "ITS
pointer", is the standard Multics pointer format. On the 6180, a
ring number (see TRR) was added. Both processors had instructions to
store pointer registers in this format.[BSG]
(2) Incompatible Time Sharing (a pun on CTSS),
a homebrew PDP-10 operating system at the MIT AI Lab in the '60's and
70's, which was an intellectual source of ideas relating to Emacs,
video, and networking.[BSG]
Janus
Data analysis application that ran in the Consistent System.
KERMIT
Protocol for transferring files to and from PCs over async lines.
kernel
We didn't speak of the "kernel" of the system at first. Our term was
usually "supervisor." When Project Guardian got underway, there was
discussion of isolating the security-critical parts of the supervisor
into a "security kernel." OS/360 used the term "nucleus."
Kludge
The ESL display, a feature of CTSS. This was a vector scope
connected to channel D of the 7094, with substantial intelligence in
the display controller. Inspired features of the Multics graphics
system.
known
A segment is "known" in a process if that process has a segment
number for it, as defined by an entry in its KST. In today's
language, a "known segment" is a file mapped into the address space
of a process (but as a segment, not a sub-expanse of linear memory),
the only way of accessing files (i.e., segments) in Multics. Making
a segment known is also called initiating, and making it unknown is
called terminating. Only segments known in a process can have SDWs
in that process, but not all known segments in a process have SDWs at
any given time. See also active.[BSG]
KST
Known Segment Table. A per-process data base that defines and stores
the mapping between segment numbers in that process and files,
effectively but not really by pathname, in the file system (actually
a tree of directory entry pointers with unique ID's). It is from
this data base that segment faults in a process are resolved, i.e.,
the segment being referenced for the first time identified with a
segment in the file system by having its page table located or
created and given an SDW in this process. The size of the KST and
the width of the segment number field of pointer registers limited
the number of segments available to a process.
The KST also, for many years, contained what later became the per-ring
RNT, which records all names that a user has
used to reference a given segment. In the case of directories, which
often have similar upper-case and lower-case names, these names were
actually returned when pathnames of segments were asked for, in
an unpredictable order, resulting in >udd, >UDD, and >user_dir_dir,
all names for the same directory, appearing in unpredictable permutation.
See initiate and terminate. [BSG]
LALR
Compiler-compiler system, used for parser generation. Done by Robert
Eachus and Pat Prange at BCO. The LALR translator construction
system includes an LALR ("Look Ahead Left-to-right Rightmost"
derivation) parser algorithm.
LAPB
A flavor of X.25. Multics has it.
LCS
Laboratory for Computer Science. Later name for Project MAC.
LDBR
Load descriptor base register. The 645 and 6180 process-switching
instruction, which directs the appending unit to the base (or page
table) of the descriptor segment. Causes a flush of the associative
memory. [BSG]
Level 6
A Honeywell minicomputer, built by Honeywell at BCO in Billerica, MA.
Librafile
The "Firehose drum." A large, fixed-head (head per track, hence
indistinguishable from a drum), disk used on 645 Multics first as
simply the highest-speed secondary storage device, then as a storage
device targeted for user temporary segments such as stacks, and
finally as the first paging device. "Firehose" was a reference to
its high rate of data delivery, 1MB/s. Capacity was 16MB. It wasn't
called a Librafile at first; that name came after the original
company that made it was acquired by Singer. These drums were
rumored to be used on Polaris guided missile submarines.
Library tools
A set of programs used by system maintenance staff at various sites
to install, upgrade, and maintain libraries of source and executable
objects.
LILA
Query language accepted by LINUS.
link
(1) (Type of branch). A directory entry which describes not a file
or a directory, but a text string which is (intended to be) the
pathname of some other directory, file, or link. What UNIX calls a
soft link. Before the invention of message segments, the printer
daemon implemented its queue by making links in a special directory
(so that access control could be used to restrict this activity),
adding extra characters onto the pathname stored to describe the
requester and print options. [BSG]
(2) As in dynamic linking. A special indirect-word with a fault tag, FT2,
used to implement symbolic references from one program to another. When a
program first references some symbolic name (an external procedure, an
external datum (see ALM), the CPU takes a fault when indirection through
this indirect-word is attempted. The system inspects the word, and finds
pointers to strings describing the symbolic reference, and invokes the
dynamic linker to resolve it, and places the ITS pointer resulting from the
search into this word (pair, actually, at that point) and restarts the
instruction (this was called "snapping" the link). From that point on, the
link functions as a normal indirect pointer, until the target segment is
terminated, at which point the link can be "unsnapped" to its original
condition.[BSG]
linkage section
The output of a compilation is program instructions, in the "text"
section, and static storage and linkage information for the dynamic
linker, in the linkage section. The EPLBSA assembler produced
separate text and link files, but early in Multics development the
convention was changed to combine text and link into a single
segment. When a segment is linked to by the dynamic linker for the
first time in a process, the linkage section from the object file is
copied into the process's combined linkage segment for the current
ring.
linker
See dynamic linker.
LINUS
Logical Inquiry and Update System. Query front end for MRDS.
Unbundled product.
LISD Large Information Systems Division. The GE/Honeywell/Bull
division that built mainframes. Other parts of the Honeywell
computer business were BCO, which did minicomputers, and Bull, which
did the Level 62 and 64.
LISP
List processing language developed at MIT in the 60s. See MacLisp.
listener
The user-ring program that loops reading a line of input from the
user and submitting it to the command processor. The listener, or
"command level", is accessed via the switchable API cu_$cl (you can
install your own listener), and is called whenever command level is
"pushed" by an error (compare UNIX behavior) as well as at process
start-up. Hence, one could investigate blowups with debuggers, or
even change variables and type "start" ("%"). Note that the job
discipline is a stack, not a ring of equals as in UNIX. [BSG]
load control
Multics has elaborate features to handle more user demand than it is
able to serve. Load Control assigns different weights to different
initial procedures so that, for example, a LSS user counts as using
half the system resources of a regular user. Permission to log in
depends on whether the system has reached its load limit, set by the
system administrator per shift, and on whether someone else in the
same load control group can be preempted, that is, bumped off the
system. If you get logged in, Load Control protects you from
preemption for some specified time period, and chooses unprotected
users for bumping.
logical volume (LV)
NSS term meaning "a group of disk packs treated as one as a pool for
segment allocation". See physical volume. [BSG]
login
The command interpreted by the answering service to create a process
for a user. "Login" was the command name used on CTSS and carried
over. I think this is east-coast usage; west-coast systems seem to
use "logon" instead.
LOT
Linkage Offset Table. The per-ring table at the head of the combined
linkage segment that locates each active segment's linkage
information. Indexed by segment number, each word is a packed
pointer to that segment's linkage section.
LP
Cambridge Project software done by R K Scott?
LRK
Compiler-compiler system, used for parser generation. Done by Dave
Ward at BCO.
LS TAC
?
LSS
Limited Service Subsystem. Multics allows a project administrator to
specify the initial procedure for a user process. The limited
service subsystem gives a user only simple commands, and user control
assigns a smaller load control weight for LSS.
LUT
Multics site: Loughborough University of Technology (Loughborough,
England)
LVT
Logical Volume Table. NSS table listing mounted volumes.
MAC
See Project MAC.
MacLisp
The Multics port of LISP. Used virtual memory. Supported Emacs.
MACSYMA
Symbolic mathematics subsystem written in LISP at MIT AI. Ported to
MacLisp by Dave Moon in 1974 and used for some problems no other
machine could handle; Multics MACSYMA could do them by using virtual
memory.
MAD
Michigan Algorithm Decoder. A 7094 language developed by Graham,
Arden, and Galler at U of Michigan. Henry Ancona worked on a design
for a Multics compiler but it was never implemented.
mail
Quick and dirty unsecure mail was written by Tom Van Vleck in 1969,
in imitation of his CTSS mail. Later, this interface was switched to
use ring-1 message segments, and then later still was replaced by a
suite of tools designed for use in a networking environment. The
early Multics mail tools predated the Internet and "net mail".
mailbox
(1) The per-user file that mail is received in. (2) A cell in the
SCU, used to interrupt an active device.
Mainz
Multics site: University Mainz (Mainz, Germany)
MATPAC
?
MCB
Multics Checkout Bulletin. Early Project MAC document series.
Technical white paper, internal to the development group.
MCC
Multics Computer Center. Another name for Honeywell's System M.
MCHQ
Canadian DND Multics site.
MCR
Multics Change Request. The authorization form that had to be
approved as part of the CISL development process before a change was
made to Multics.
MCR Board
The group of developers who met weekly to consider MCRs.
MCS
Multics Communication System. Either the DN355 assembly-language
software that ran terminals and comm lines for 6180 Multics, or that
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 could 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.
[Perhaps Charlie Hornig or someone else knows something about how MCS
and IP/TCP later interacted?] [BSG] [Should also say something about
what came after MCS, e.g. NPS, UNCP etc]
MDA
McDonnell Douglas, Transport Aircraft. Multics site.
MDBM
Multics Data Base Manager. Another name for MRDS.
MDBM Data Dictionary
?
MDN
Multics Design Note. Early Project MAC document series.
MegaCalc
Third party spreadsheet package for Multics.
message coordinator
A 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)-BSG]
message segment
A ring-1 segment that contains individual messages, used to implement
mailboxes. Used extended access to specify additional access
controls.
metering
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.
Ministere de la Culture
Multics site: Ministere de la Culture (Paris, France)
Ministerie van Sociale Zaken
Multics site: Ministerie van Sociale Zaken en Werkgelegenheid (Den
Haag, The Netherlands)
MGS
Multics Graphics System. Also Max Smith's initials.
MGT
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.
mini-GIM
Small, simple, fast version of the GIM, introduced in 1968.
Minitab
Third party stat package for Multics by Minitab, Inc. Designed to
run on a wide variety of operating systems.
MIT
Massachusetts Institute of Technology. A private university, founded
in 1860, located in Cambridge, MA. "A university polarized around
science." Home of Project MAC.
mmtu
The 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.
Monsanto
A sale Multics didn't make?
motd
Message of the Day. This info seg is printed at login, and is
updated by operations to inform users of system schedules, new rules,
and so forth.
MOWSE
Multics Online Workstation Support Environment. 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). [BWS]
MPC
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. [BSG]
MPN
Multics Planning Notebook. Planning and coordination document used
in the late 60s to manage Multics bringup.
MPO
Multics Project Office. A group within Honeywell FSO that tried to
sell Multics to the government.
MR
Multics Release. The system numbers presented to the customer world.
MRDS
Multics Relational Data Store. Originally written by Jim Weeldreyer
and Oris Friesen of Honeywell Phoenix. Unbundled product.
MRGEDT CTSS command that sent a job to the 6.36 simulator.
MRPG Multics Report Program Generator. Done by Jim Falksen at
Honeywell Phoenix.
MRX
Internal Honeywell codename for a never released processor.
MSB
Multics Staff Bulletin. Document describing rules and administrative
stuff.
MSP
(1) Multics Special Projects; Minneapolis group responsible for
marketing and supporting first Multics sites after the merger. (2)
The airport code for Minneapolis/St. Paul. [WEB]
MSPM
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.
MSS
Multics Standard System. System numbers used internal to the
development group, and at MIT.
MST
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. 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. [BSG] See bootload and Zero Six Dog.
MSU0451
Disk unit. MSU0451 held about 149 MB of usable Multics pages.
MSU0501
Disk unit. MSU0501 held about 1006 MB of usable Multics pages.
MSU3381
Disk unit. MSU3381 held about 3367 MB of usable Multics pages, and
was an IBM OEM.
MTB
Multics Technical Bulletin. Replaced MCBs after Multics was "checked
out." Technical white paper, internal to the development group.
MTR
Multics Task Report. Early Project MAC document series. Described
who was doing what.
mult
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 Ring 1 command level command MULT, which,
indeed, told it to do just that - or was it the BOS runcom? Yes, I
think it was the latter.
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]
multer
At times I used "multer" in the sense one would use "guitar player"
as opposed to guitarist, i.e., it could be a term of praise through
too-low-a-term (what's the trope term?). "Noel was one multer not
soon to be forgotten."[BSG]
Multician
Anyone who contributed to the development and success of Multics.
There is no such thing as an ex-Multician. [TVV]
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."
"Tom Van Vleck was one of the original core of Multicians." [BSG]
Multicious
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. [BSG]
Multics
Multiplexed Information and Computing Service. Always spelled in
mixed case. Informal plural: Multices (Latinate).
multilevel daemon
?
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 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. 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.
Nancy
Multics site: Centre Informatique Regional Interuniversitaire de
Lorraine, Universite de Nancy 1 (Vandoeuvre Les Nancy, France)
NCP
Network Control Program. (1) the set of ARPANet inter-host protocols
that preceded TCP/IP (which latter made the Internet possible). (2)
The set of ring 0 Multics programs that supported this protocol in
the Multics ARPANet implementation, written by Doug Wells and Ed
Meyer, and discarded when TCP/IP took over. This system relied on
the Host-to-IMP [Interface Message Processor] protocol, that
supported in wired code by Raj Kanodia, which pioneered an event
count technique for which he later acquired some fame. The Multics
NCP involved a daemon which periodically called in to unload buffers
of unfetched data from from ring 0. The NCP code was conceptually,
stylistically, and implementationally isolated from the rest of ring
zero, and was a bete noir to all Multicians except the aforementioned
"network people".[BSG]
NCSC
National Computer Security Center. This US government organization
produced the Orange Book under the guidance of its Deputy Director,
Roger Schell.
new_proc
This command reveals a deep weakness in the Multics design. A
Multics process is expensive to create, so it runs commands and user
programs inside the same process that contained the user's listener
and shell. If these programs damage the process's machinery, such as
its stack or combined linkage segment, the process may malfunction.
The new_proc command destroys the current process and creates a new
one, by sending a signal to the answering service. Until Multics was
changed (about 1970) to refresh the linkage information for a program
when it was recompiled, users used to have to new_proc every time
they recompiled.
notify
"Wait/notify" is one of two interprocess synchronization mechanisms
used in Multics. "block and wakeup" is intended only for user
programs. The overhead of event queues and the inability to wait on
multiple events at once made it unsuitable for use in complex
asynchronous subsystems (e.g., page control) in the supervisor. A
process goes to "wait on" a given "event", a 36-bit number then
recorded in the traffic control entry for the process. The process
is suspended until some other process "notifies" that event,
whereupon -all- processes waiting on it are resumed. Part of the
protocol is the possibility of false notifications, the waiter must
test upon resumption, and no datum is conveyed with the notification.
Directory and other non-wired locks, as well as paging events, are
managed with this mechanism. [BSG]
NPS
Standard GCOS DN355 software. Multics could run with this as well as
its own, more functional, MCS.
NPT
New Product Test. Honeywell organization that tested each new CPU
after it was built. In the late 70s, lack of test cell capacity was
a limiting factor on LISD's ability to deliver Multics CPUs.
NSA
Multics customer. See Site N and DOCKMASTER.
NSS
New Storage System. MR 4.0 included a rewritten storage system that
supported more disk devices and improved fault tolerance and
recovery.
NTT
Nippon Telephone. Built a Multics clone, the NTT DIPS.
NWGS
Naval War Games System. A set of 4 systems sold to CDC who used them
for US Navy training.
octal
Counting in base 8. On a 36-bit word machine, this is the natural
way to express numbers.
ONERA
Multics site: Office National d'Etudes et de Recherches Aeronautiques
- Centre d'Etudes et de Recherche de Toulouse [ONERA-CERT] (Toulouse,
France)
Online T&D
Online Test and Diagnostics. Allows boxes to be isolated from a
running system and tested. CPU and memory were first. I/O testing
was not done until the mid 80s.
operator
Unsung heroes. Computer operators at many sites worked long and hard
to keep big machines running and users happy. This is a
fast-vanishing profession. See also pl1_operators_.
Opus
System proposed to follow on after Multics. Eventually canceled by
Honeywell.
ORAS
Operations Reporting and Accounting System. A large application
developed by SofTech under contract to GM corporate in the mid 70s.
ORAS was a huge spreadsheet application that summarized all of GM's
business.
Orange Book
Standards document produced by the NCSC, titled Department of Defense
Trusted Computer System Evaluation Criteria, DOD 5200.28-STD,
December 1985. Describes levels of security for computer systems.
Roger Schell was the main driver behind this document.
Orion
Honeywell codename for a processor in the ADP architecture.
OU
Oakland University. Multics site.
Overlap Project
MIT social-science project which paid to keep the 7094 going at IPC
when Multics was late.
packed pointer
A hardware feature on the 6180, and a much rarer software format on
the 645, that encodes a virtual memory pointer (segment and word
number, plus EIS bit offset on the 6180) in one 36-bit word. While
50% more storage-efficient than the two-word ITS pointer, a packed
pointer could not be used for indirection (see EPPBP) or the storage
of a value where ring number had to be saved (see TRR). Also, only
twelve bits were available for the segment number (instead of 15 in
an ITS pointer), and this was the tightest limit on the maximum
number of segments in a process, far too small. The PL/I compiler
made heavy internal use of packed pointers (which had to be loaded
with a special instruction, again, see EPPBP), but because of the
above, their use in general system code was quite uncommon. [BSG]
page
A fixed size piece of memory. The hardware supports both paged and
unpaged segments. The SDW for a paged segment points to a page
table, an array of PTWs (stored in the AST). Each PTW points to a
page in core, or has a fault tag and an indication of where on
secondary storage the page's contents can be found. The 645 had two
page sizes, 64 words and 1024 words. Bookkeeping and storage pool
management was so complex that small pages were eliminated in 1968.
page control
The ring 0, wired software responsible for managing the transfer and
mapping of pages in and out of memory. Only a small amount of this
is the famous "page replacement algorithm" due to Corbato; most of
this code, almost all complex and highly-optimized assembler
language, is the management of I/O and state, the multilevel paging
hierarchy management, and interaction with and services provided for
segment control and other areas of the system. Page control was
perhaps the most asynchronous, difficult, and critical component of
the whole system. Successive gurus who worked there and left their
marks were Stan Dunten, Steve Webber, and Bernie Greenberg. [BSG]
page fault
Still called that, or "missing page exception." What the hardware
does when a page is referenced whose PTW says it's not present.
paging device
A device used as the intermediate level store in a multilevel paging
hierarchy ("page multilevel"), at first the firehose drum, then later
the bulk store.
PAL
(forget what this stood for) Programming linguistics language created
by Art Evans, using ideas from Martin Richards. Used in the first
course taught using Multics, 6.231, in the summer of 1969.
Palyn Report
Report prepared in 1978 by Palyn Associates for Honeywell corporate,
recommending long range large systems plans.
partition
A contiguous region of a disk volume.
Pascal
Grenoble wrote a Pascal compiler for Multics in the 1980s.
password
Multics passwords are stored in the PNT encrypted by a one-way
function. They are eight characters long, and the login command has
optional arguments to generate a pronounceable password for you.
(Code written by Morrie Gasser of MITRE in connection with Project
Guardian.) This facility can be invoked automatically after a
password has expired.
path name
Multics segments are named by a sequence of entry names, separated by
> characters, e.g. >udd>m>vv>go.ec. This path name provides a path
from the root directory to the segment. Pathnames are absolute
(descend from the root) or relative to the current working directory.
PC support
A feature in MR11.0? See MOWSE.
pdd
(or PDD, process_dir_dir). Alternate names of the directory
>process_dir_dir, whose subdirectories are users' process
directories, created and destroyed as processes are created and
destroyed. Compare UDD.
PDT
Project Definition Table. The per-project segment that defines which
users may login on a project to User Control. A project
administrator can update this segment online.
PDS
Process Data Segment. A per-process, ring 0 segment, containing
per-process supervisor data (other than the KST and descriptor
segment) as well as the ring 0 stack of the process. The PDS has the
same segment number in every process, and contains many
symbolically-referenced data objects. When a process is made
eligible by the scheduler, the first page of the PDS, which contains
data needed by wired code, including places for faults to store SCU
data, is wired. Compare PRDS. [BSG]
phcs_
Privileged HardCore Supervisor gate. A gate which allows
semi-privileged operations, such as examining the contents of ring 0,
but doesn't let the user do things that might crash the system. A
user with access to phcs_ is trusted, since this gate can be used to
examine passwords in the input buffers. Compare with hphcs_.
Phase 1
Integration milestone during Multics development. The first time
that Multics booted from tape and came up to type on the operator's
TTY. Accomplished December 1967 by Noel Morris and Tom Van Vleck.
PHM
Page Has been Modified. Flag set by the CPU in a PTW when a page was
stored into, used by the page control replacement algorithm.
Phoenix
City in Arizona, where LISD built computers. Used metonymically to
refer to LISD management.
photocomposition
A feature of compose.
PHU
Page Has been Used. Flag set by the CPU in a PTW when a page was
read, used by the page control replacement algorithm.
physical volume (PV)
NSS term meaning "a disk pack". The contrast is with logical
volumes, groups of PV's: users can specify on which LV a segment is
to reside, but not on which PV - that is up to the system alone.
PV's, however, are the unit of data integrity and recovery, and this
non-transparency in the illusion is apparent. [BSG]
PIT
Process Initialization Table. Segment in the
process directory where the system
stores constants determined at process creation time.
PL/I
Programming Language #1, invented by IBM. Combining scientific
features from FORTRAN, business features like records from COBOL, and
block structuring from Algol, PL/I's future looked rosy in 1965 when
the team chose it for the Multics systems programming language and
the idea of coding an operating system in a "higher level language"
was radical. Multics's storage models, procedure models, data types,
and run-time architecture were all designed around those of the PL/I
language, and all system APIs were given in PL/I. Use of any other
language for systems programming tasks was actively and officially
discouraged. Nonetheless, over the years certain critical subsystems
of substantive complexity and bulk (notably page control and the
scheduler) were recast into assembler language to optimize
performance. The version 2 Multics PL/I implementation (Bob
Freiburghouse and Barry Wolman, chief architects), is arguably the
preeminent PL/I implementation of record. [BSG]
pl1_operators_
A segment referred to by every compiled PL/I program, containing open
code (threaded code) cliches for common constructs, including
call/save/return. Normally every process shares the same (wired)
copy of the segment, but a user can modify the operator pointer in
the stack root to switch operators to, for example, test a new
version or to turn on call tracing.
pln
Print with Line Numbers. A private command by Max Smith that was
used heavily in the development community, very similar to UNIX grep.
Although the Multics product had nothing like it, widespread feeling
that it was not Multicious, as it had no obvious place in an
organized, extant or proposed suite of tools, and an immensely useful
feature of "knowing" about the insides of archives which raised
questions about other commands, prevented it from ever being made
part of the product. While pln's many fans were often frustrated by
the double-edgedness of the at-times conservative sword of
multiciousness, and could not understand why the world at large could
not benefit from this incredibly useful tool, precisely such a
profusion of diverse, unrelated tools is in fact one of UNIX's most
well-known flaws.[BSG]
PNT
Person Name Table. User control's password and user name
registration database.
pointer register
A register on the 6180 (or "pointer pair" on the 645) containing a
segment number and a word number within that segment (and on the
6180, a ring number and a bit number for EIS), i.e., a generic
pointer into the segmented address space. Other than constant and
code references, Multics instructions usually make references
relative to pointer registers, for the same reasons of relocatability
that obtain in any architecture. On the 6180, the pointer registers
visible to the Multics instructions are actually fabricated illusions
constructed of "address registers" shared with the non-Multics (GCOS)
CPU's and segment and ring registers managed by the appending unit,
which lock-step mimics every CU operation on the "address registers"
to create the software illusion of pointer registers. On the 645,
the "pointer pairs" were wholly within the base frame, being built of
8 ABRs which could function either as segment or word pointers and be
associated into pairs. During normal Multics PL/I code, pointer
registers are reserved for the stack frame, the entry vector of
pl1_operators_, and less strictly, the procedure's actual parameter
list, its linkage section, and the operator table at the base of the
current stack. In addition to numbers 0, 1 ... 7, the pointer
registers also had names, ap, ab, bp, bb, lp, lb, sp, sb, based upon
their conventional use in Multics PL/I object code. [BSG].
PPR
Procedure Pointer Register - a tripartite processor register defining
the segment, ring, and location of the next instruction to be
executed, the Multics equivalent of the "instruction counter", which
is the "location" component of the above. The processor actually
implemented the three components on three different boards in three
different ways, but Multics chose to conceptualize it as one. The
ring component ("PRR") defines the current ring of execution.
Compare TPR, TRR.[BSG]
PRDS
Processor Data segment. A per-processor, fully-wired ring 0 segment,
containing not only symbolically-referenced per-processor data but a
stack used when running fault and interrupt handlers that cannot take
page faults or interrupts, such as page control itself, and the
scheduler. The processor carries around the SDW for the PRDS from
process to process like a carpet-bag, dropping it in the same slot in
the descriptor segment of each process as the processor moves from
process to process, literally holding it in the accumulator during
every process-switching instruction (LDBR). Compare PDS. [BSG]
prelinker
One of two. The Multics supervisor is pre-linked statically at boot
time by a pair of assembly-language programs known as the
"prelinker". In the late 70's, the capability of pre-linking select
user's address spaces as a performance boon was added. This is done
by a separate "prelinker." [BSG]
PRHA
Puerto Rican Highway Association. Multics customer.
printer
Multics supported the standard-issue GE and Honeywell line printers
of the era of fanfold paper, fitted with special type-bars and chains
to support the ASCII character set. As these printers were designed
for a 6-bit BCD character set (and were thus incredibly fast at
printing foot-thick dumps and the like), printing
upper-and-lower-case characters required odd modes and complex escape
sequences. Although softwarily possible, users never attached
printers or directed output to it -- the only mode of printer use is
to queue ASCII files to be printed by the Printer daemon, using the
dprint command.
Before the era of GUIs and WYSIWYG editing, fanfold listings were an
invaluable aid in developing and debugging programs. [BSG]
probe
Multics high-level PL/I source language debugger.
process
An address space and a locus of control. A Multics process is a
complex object, because it has a complicated address space.
process directory
A directory created when a process is created for exclusive use of
that process, namely per-process and scratch segments, including
stacks (including the PDS) and combined linkage segment. Disk quota in the
process directory is not charged against the user. All process directories
are subdirectories of >PDD [BSG]
process overseer
Procedure called at process initialization time. It sets up the
process environment and then calls the process's listener.
process preservation
Multics can save a process across a communications interruption. A
user can later reestablish communications and connect to or destroy
the preserved process.
profile
Facility to count the number of times each source statement in a
program is executed. Compile a program with the -profile option, run
it, and then use print_profile to print out per-statement counters in
its static section.
project
A group of Multics users working together, for the same firm or
organizational division, for whom Multics can pool all disk record
quota and establish common access rights, and grant other group
privileges. Although a user has to be registered globally to the
system in order to use it, he or she can only log in as a member of a
project, one project or another at any one time. [BSG] The PDT lists
a project's users.
project administrator
The person who administers a Multics project. Among the
responsibility of the Project Administrator is registering and
deregistering users on the project (a user can only log in if he or
she has a project to log in to), and creating home directories under
the project directory. [BSG] Decentralized management of the user
community was an important feature of User Control; the system
administrators established the registration of persons, and their
initial passwords, but project administrators could add and drop
registered persons without consulting the system administration, and
modify users' resource quotas and get reports of current usage.
project directory
A directory for a given UDD. The subdirectories of the project
directory are home directories. In the directory pathname
>udd>Multics>Morris, >udd>Multics is the project directory. [BSG]
Project MAC
MIT Project MAC, suggested by J.C.R. Licklider, was the organization
that began the research that led to Multics. It is now called the
MIT Laboratory for Computer Science.
PRR
Procedure Ring Register. Part of the PPR. Stored in the SCU data.
PTL
Page Table Lock. More accurately, a lock on all the data-bases of
page control, that is, PTWs, core frame tables, and paging device
map. This lock, protecting a huge amount of performance- and
integrity-critical data, is used only by wired code masked against
interrupts, including interrupt and page fault handlers, so it was
designed as a "spin lock", which would only be found locked on
multi-processor systems. As Multics grew, the necessity of
alleviating this growing performance bottleneck resulted first in the
Cow's Stomach, and later in an extremely non-modular tryst of traffic
control and page control, also by Greenberg, allowing processes to
wait (see notify) on the Page Table lock as a highly special case.
[BSG]
PTW
Page Table Word. 36-bit word interpreted by the hardware, which
contained the absolute address of a page, or a fault tag and an
indicator of where the page is on secondary storage.
pure procedure
Multics compilers all generated code that did not modify itself.
This may seem like a no-brainer, but it was quite radical at the
time: OS/360 struggled with the concept of "reentrant" (same thing as
pure procedure), "serially reusable," and another flavor, forget the
name, of program. CTSS stored into its code in lots of places, but
we realized that this would be very bad on a multiprocessor system.
PVT
Physical Volume Table. NSS table listing physical volumes.
QED
CTSS editor written by Ken Thompson. Ported to Multics BCPL. Bob
Daley then wrote Multics qedx as a less functional but faster
version. Both qed and qedx are programmable: they support multiple
buffers, and a user can execute the contents of a buffer containing
editor commands. Doug McIlroy wrote a version of tic-tac-toe in qed.
Qedx was the standard editor for most of the Multics development
community throughout the 70's. See ted.
quit
A method used to interrupt a running program. The quit condition is
raised by pressing the ATTN or INTERRUPT key on a terminal. This
condition normally causes the printing of QUIT followed by
establishment of a new command level.
quota
Usually referred to disk quota. Sometimes people spoke of the other
resource limits, CPU, dollar cost, etc, and quotas, since that was
the term used on CTSS.
RADC
Rome Air Development Center, Griffiss Air Force Base, Rome NY. The
first Multics sale (after MIT, BTL, and GE). Pronounced "rad-see".
RAE
Multics site: Royal Aircraft Establishment (Farnborough, England)
RAID
GECOS machine-level debugger, like DDT.
RALR
"Ring alarm register". A 6180 CPU register that causes a fault when
a process transfers control to a ring at least that high. Using this
register, interrupts and signals can be masked on a per-ring basis
without the need for software help in inter-ring transfer. [BSG] The
645 didn't have this register, and simulated the function by giving
each process multiple descriptor segments, one per ring.
RAR
(1) Read-alter-rewrite, an SCU operation needed by a class of CPU
instructions (AOS, STAC, STACQ) often used for synchronization. On
the 645, the SCU ensured that no other requests (from CPU's, GIOC,
etc.) were serviced between the requester's "read" and "rewrite."
Typically, STAC and STACQ were used to lock and unlock locks. The
6180 generation SCU's did not at first support this two-phase
operation, and much effort was spent by GCOS-oriented hardware
designers to convince us to make Multics use LDAC, the GCOS locking
instruction which indicates the locked state by zeroing the word in
question in one phase, instead! This was unacceptable, and we got
compatible two-phase ("STACQ") locking retrofitted, but it took some
time to debug it to acceptability. (2) Roger A. Roach, MIT IPS top
Multics man. [BSG]
RCCL
Read Calendar Clock. 645 instruction that read the clock. Returned
a 52-bit value, the number of microseconds since 0000 GMT Jan 1,
1901.
RCI
Renaissance Computing Incorporated. Took over support of the
Consistent System.
RCP
Resource Control Package. Written by Bill Silver. Handled tape
mounting requests, operator interaction, tape reel access control.
read bracket
The range of rings which can read a given segment. If the segment's
ring brackets are 1, 5, 5, the read bracket is rings 0 to 5 (the
first 5). Also sometimes used to refer to that upper inclusive limit
itself. [BSG].
ready message
The standard listener called cu_$ready_proc before reading a command.
The default action for this call was to print a line like
r 1445 2.370 22
showing time of day and virtual CPU usage and page faults since last
message. This message was customizable by author-maintained programs
such as general_ready or could be turned off entirely with the
ready_off command.
relative
A relative pathname is interpreted relative to the current working
directory.
Renault
Multics site: Renault (Boulogne-Billancourt, France)
restor
BOS command. Opposite of save. The save and restor commands copied
the contents of disk to tape in physical format, as fast as the
system could do this. These operations were much faster than running
the backup daemon inside Multics to dump segments logically through
the file system. Replaced by the volume backup facility.
retrieve
Obtain a copy of a lost file from a backup tape and put it back in
the hierarchy.
REWPUG
Read, Execute, Write, Privileged, Unpaged, (not) Gate, the six SDW
permission bits on the 6180 in their storage layout, a cryptic
formula which often appeared in part or whole in descriptor segment
dumps, and was very dear to Noel Morris. The corresponding 645
formula was "SAWP DATA" (Slave-access write-permit), which novices
sometimes mistook for a typo. [BSG]
ring
Concentric level of privilege of user/supervisor distinction.
Although now a standard part of the Intel architecture and Microsoft
Windows, this concept was invented on Multics. Although there were
64 rings (an illusion created by software) on GE 645 Multics, there
are 8 rings, supported in hardware, on the Honeywell 6180 in its
various models. Only rings 0, 1, and 4 saw any non-forced use.
[BSG]
ring 0
The most privileged ring of the Multics architecture. The hardcore
supervisor runs in ring 0, so the term was used as a casual synonym
for "the supervisor" or "the hardcore." Privileged code only runs in
ring 0.
ring brackets
Three numbers associated with every segment defining the highest ring
which can write in it, the highest ring which can read it (must be
equal or larger than the preceding), and the highest ring (if greater
than the preceding) which can call it as a gate. Executable segments
have the first two numbers equal, lest some ring be able to influence
the execution of an inner (lower-numbered, less privileged) ring by
writing the segment.[BSG]
RJE
Remote Job Entry.
RLV
Root Logical Volume. NSS term for the logical volume containing all
directories and system critical software.
RNT
Reference Name Table. This per-ring table records all reference
names that a user has used to reference a given segment. Also
holdssearch rules and current working directory.
RPV
Root Physical Volume. NSS term for the physical volume that contains
the hardcore partition and the root directory.
root
The top directory in the naming hierarchy of a Multics system. The
name of the root is simply ">". The root directory is always stored
on the RPV.
runcom
The BOS facility that allowed the execution of a script of BOS
commands, named after the corresponding CTSS facility. Runcoms could
call other runcoms but not return. In 1977, a facility for
"continuous operation" was added to BOS and Multics; a small piece of
memory was shared between the two environments for flags, and a
runcom written that would reboot Multics if it crashed, if certain
flags were set in the communications region. This facility kept MIT
Multics running during the Big Snow of February 1978.
run unit
A COBOL concept. There were some commands whose short names were
spelled out, rather than pronounced, such as stop_cobol_run_unit.
RUNOFF
CTSS command for text formatting written by Jerry Saltzer. Ported to
Multics BCPL. Eventually replaced by compose. Ancestor of UNIX
troff.
salvager
A set of programs for reconstructing directory and file system
integrity after a crash. Until NSS, the Salvager was a separate tape
booted after a crash; built of Multics supervisor parts and running
entirely in ring 0, it scanned and repaired the file hierarchy
instead of coming up to serve users. Eventually, more and more of
its functionality was moved to code that can run while the system is
up. When a crawlout occurs, locked directories are salvaged before
returning to the user ring. [BSG] The salvager does more or less
what UNIX fsck does.
scheduler
Used ambiguously, as in today's operating systems, to denote either
that piece of software that manages multiprogramming or that
allocates time slices to users. Since these are the same program,
"pxss" (process exchange, switch stack), this was not a problem.
This very large, complex assembly language module was highly
optimized, including by many non-modular hooks into page control.
[BSG] The Multics scheduler began as a Greenberger-Corbato
exponential scheduler similar to that in CTSS. About 1976, it was
replaced by Bob Mullen's virtual deadline scheduler.[TVV]
SCOMP
Secure COMPuter. Secure front-end processor, done by Honeywell in
Tampa, first system to get an Orange Book A1 rating. Used to be
called SFEP.
SCSI
Multics site: SCSI (?)
SCU
(1) System Control Unit. The multiported, arbitrating interface to
each bank of memory (usually 128 or 256 KWords), each port connecting
to a port of an "active unit" (CPU, GIOC or IOM). On the 645, the
clock occupied an SCU as well. The SCU's have their own repertoire
of opcodes and registers, including those by which system interrupts
are set by one active unit for another. The flexibility of this
architecture was significant among the reasons why the GE 600 line
was chosen for Multics.[BSG] (2) Store Control Unit. The 645 and
6180 instruction instruction that stores an eight-word encoding of
the processor state (other than register contents and the state of
the EIS unit on the 6180) at the time of an interrupt or fault.
Because of potentially lengthy indirect chains and instruction
modifiers with side-effects (increment-on-reference pointers),
instructions must be restartable in the middle. Only some of this
data is used by the software, and there are bits that are by and
large not understood by the system staff: most is used by the
processor upon restart. With the EIS unit data, the processor state
took 40 words to encode [BSG].
SDW
Segment Descriptor Word. An element of a process' descriptor
segment; the hardware-accessible data element that defines a segment
and the process' access rights to it.
SEADACS
Old name for McDonnell Douglas site in Long Beach CA.
search rules
The dynamic linking mechanism looks for segments in a set of
directories specified by the user process's search rules. These
rules are per-process and stored in the RNT. In addition to
specifying a list of directories, there are three special values that
can be specified: -initiated-segments, specifying the use of already
initiated segments (this rule should always be first); -working_dir,
to select the current working directory (which might have changed
since the search rules were set); and -referencing_dir, which
specifies "the same directory as the one holding the procedure that
took the linkage fault." This is a subtle brilliance, that helps
subsystems find the version of code that they are packaged with.
segfault
Jargon for "(missing) segment fault". What the hardware takes when a
segment number is used for which there is no valid SDW. The latter
is not necessarily an invalid or error situation, in fact, it is the
default situation when a segment has just been made known. Segfaults
are resolved by looking in the process' KST (table of segments known
to it) to find out what segment is intended to be referenced, and the
AST searched for that segment's page table to construct the SDW. If
not active, the segment has to be activated, perhaps requiring some
other segment to be deactivated to make room for its page table.
When segments are deactivated, segment control invalidates the SDWs
of all processes having SDWs for it, to start this tale at the
beginning again. [BSG]
segment
A user-visible subdivision of a process's address space, mapped onto
a storage system file. Each segment is 1MB long, and has a zero
address.
segment control
The ring 0 software responsible for the management of segmentation,
the allocation and deallocation of page tables, the connection and
disconnection of the SDWs of processes from the page tables, and the
performing of operations (such as truncation) upon active segments.
Tightly bound up with, and requesting service of page control, in the
"New Storage System" (NSS), segment control is tightly bound up with
VTOC management as well. [BSG]
segmentation
The division of a process' virtual memory into a vector of vectors,
each such vector being a segment. The idea came from the Burroughs
5500 series. Different segments can have different access rights,
including for different users, and other differing attributes.
Multics's use of segmentation is as a basis for what are now called
"memory-mapped files", hence each segment is a file and each file is
a segment, in some sense, the basic idea of Multics. [BSG]
Selectric
IBM mechanism for typewriters and computer terminals. The character
set was on a plastic "golf ball" that struck the paper through a
typewriter ribbon. This mechanism was used in the IBM 1050 and 2741
terminals, in various third-party terminals, and in the console
typewriter of the 6180. There were three grades of this mechanism
OEM'd by IBM, light, medium, and heavy duty; the 6180 console had a
heavy duty model.
SEP
Multics site: Societe Europeenne de Propulsion (Vernon, France)
Series 60, Level 68
Marketing name for a repackaged 6180. Later called the DPS-68.
SET
System Environment Test. Honeywell organization.
SFEP
Secure Front End Processor; original name of the machine that
eventually becameSCOMP.[WEB]
shell
The Multics command processor used to be called the shell. This
program is passed a command line for execution by the listener; it
parses the line into a command name and arguments, locates the
command and initiates it, and calls command with arguments that are
character strings. It is simple to replace the default system
supplied shell with a user-provided program, by calling cu_$set_cp
(see abbrev). A UNIX shell includes the concepts of both shell and
listener in the Multics sense.
shift
The accounting system defines up to 8 shifts, which can start at any
half-hour boundary in a week, at site option. User Control charges
users' resource usage against the slot for the current shift in a
per-user vector in the PDT for the user's project.
shriek name
Multics has a convention of converting unique IDs into character
string names: >pdd>!BqrHmpZZtL was a typical pathname of a process
directory, generated from a 36-bit process ID. These were called
"shriek names," because a colloquial pronunciation of the exclamation
point was "shriek." The unique_name_ subroutine reduced the alphabet
to sixteen characters to eliminate the possibility of obscenities:
all vowels were removed, "v" because you can use it to look like an
"u", and "f", of course, and "y" because it's like a vowel, and 2
others. The initializer's process ID (777777000000) always came out
!zzzzzbBBBBB, which was thus always the name of its process
directory. Rich Lamson suggested that this was Hebrew for "Fly of
the Lord" (the Initializer's function, in some sense, cf.,
"Beelzebub", Heb. for "Lord of the Flies.") [BSG]
signal
PL/I name for an exception. The Multics environment maps hardware
events, e.g. zerodivide, linkage fault, out-of-segment-bounds
reference, into PL/I signals. When a signal is raised, the runtime
searches back up the stack for a condition handler for the signal,
and invokes it if found. If no handler can be found, the runtime
starts over, looking for a handler for "unclaimed_signal."
Eachlistener on the stack establishes an unclaimed signal handler.
If invoked, this handler prints a message and "caps" the stack,
establishing a new "command level" by calling a new listener. If you
give the start command, the new listener returns to the signal
handler, which returns to the point of error and retries. For
linkage faults, this setup is ideal: if your program calls a
non-existent subroutine, the system will come to command level and
let you write it, compile it, and then type start to invoke it.
Issuing the use command, followed by start, lets you specify a
different segment or entrypoint name, so that you can redirect a call
if you made a simple spelling error. The on and answer commands
establish a condition handler and execute a command line under it;
when a program asks a question by calling command_query_, a signal is
raised that the answer command can intercept and supply a canned
answer.
SIPB
MIT Student Information Processing Board. A student organization
founded in 1969? by Bob Frankston, Gary Gut, David Burmaster, and Ed
Fox. The original purpose was to provide access to computers for
students, which translated into buying time on the online systems, in
the days when computers were big and heavy and cost millions of
dollars. To be honest, SIPB was the Student IPB when the computer
center was run by the big IPB. SIPB used what is now called soft
money. Of course, as any organization does, it tended to become a
social group as well as a service organization. Many of the young
Multicians of the late 70's were active SIPB members. SIPB's
relationship to Multics was complex: by virtue of being among its
greatest admirers and promoters, they were at once among its most
demanding and insistent critics. Overall they were enthusiastic,
though SIPB even gave out CTSS time to a user (Paul Green!) for WTBS
(now WMBR). [BSG, Frankston]
Site Analysts
Heroes of Multics. Honeywell employees who worked at the customer
site and helped the customer use the machine, report problems,
install fixes.
Site N
US National Security Agency. They didn't want it known that they had
a Multics, so all the lists showed "Site N" and if you had questions,
you were referred to some guy in FSO. Bob Morris (see EPL) was
Principal Scientist at NSA after he left BTL.
SJU
Multics site: St John's University (Jamaica NY)
SMM
Segment Management Module. Early supervisor module, obsoleted before
1970; managed reference names. Sue Rosenbaum worked on it.
SNECMA
Multics site: Societe Nationale d'Etude et de Construction de Moteurs
Aeronautiques (France)
sort/merge
Multics has a sort/merge facility that was done as part of the COBOL
support. Very batch-like, as a result of the language definition.
SOZAWE
Multics customer.
SSA
Multics customer.
SST
System Segment Table. Supervisor segment fabricated at boot,
contains AST, and thus, all the page tables of all segments in use.
STAC
Store A (accumulator) Conditional (on memory operand being zero.)
The 645/ 6180 instruction used universally in Multics to lock locks
by storing a process 36-bit ID in a zero (unlocked) lock word. See
RAR.
stack
Multics has a stack segment for the stack of each ring of each
process (that has been referenced), in the process directory of that
process. The ring 0 stack is actually (inevitably) a per-process
data base of the supervisor. The need for call stacks follows from
the PL/I basis of the programming environment, which determines the
stack discipline. The stack contains data with the PL/I automatic
storage class. Procedures have stack frames - there is no
single-data-item pushing and popping (and no instructions to support
such). Stacks are kept to less than the full 256k lest wrap-around
not be detected. The base of the stack segment contains a table of
pointers to critical operators, e.g., the procedure entry
sequence.[BSG]
STACQ
Store A (accumulator) Conditional on Q (quotient register) (being
equal to the contents of the memory operand.) Pronounced "stack
queue". Indivisible RAR instruction used by Multics to unlock locks:
Multics stores a zero in the word if and only if the content is
currently the current process's 36-bit process ID; if it is not, the
supervisor or SCU RAR handling is broken. STACQ is general enough to
simulate, with a little software ingenuity, any other real or desired
indivisible storage update, and was often used to generate unique ID
tags, event counts, and the like as well as unlocking locks. See
RAR. [BSG]
standard service system
Thecommands and subroutines provided with Multics, necessary for use
of the system. Stored in >gt;sss, >gt;sl1, and >gt;unb. Notice the
mention of subroutines. Unlike many other systems, Multics makes
available a large library of utility routines used to construct the
standard commands. These routines are shared by all programs that
call them by the dynamic linking mechanism.
star convention A convention of representing the names of multiple
segments in a directory with asterisks. Each asterisk matches either
one component of the trailing characters of a component: foo.*.pl1
matches foo.a.pl1, but not foo.pl1. ** matches any number of
components: foo.** matches foo, foo.pl1, and foo.pl1.old. Although
there are subroutines to do star matching and searching, it is the
responsibility of commands to call them; star expansion is not done
by the shell. See also equal convention. [BSG]
Staran
Attached associative processor, built by Goodyear Aerospace, used on
the RADC 645 and 6180 in the mid 70s. Had 1000 1-bit CPUs that could
be combined under program control to do vector operations. The
Staran daemon ran with a load setting of 2.
static
PL/I storage class. Storage declared static is initialized once per
process.
static section
Region of the combined linkage segment where static storage is
allocated.
STC
Multics site: Standard Telephones and Cables (New Southgate, London,
England)
supervisor
That portion of the operating system which runs in ring 0, a hardware
concept on the 6180. The supervisor is loaded from the boot tape,
and, like the rest of Multics, consists of segments, but most of
them, although they (mostly) are paged, exist outside of the file
system. Having SDWs in every process, the supervisor forms a part,
the same part, of every process' address space, occupying its lowest
segment numbers. The supervisor's SDWs are permanent, and never
incur segfaults. Some parts, e.g., the ring 0 stack and the KST, are
actually different segments in each process, although with identical
segment numbers. The supervisor can be thought of as a shared,
secure domain common to all processes: this gives it the ability to
develop and store pointers that are valid across processes, a
capability notably lacking from the Multics user rings. [BSG]
SysAdmin
Project name for system administrators, the people who registered
users and projects.
SysDaemon
The Multics project name that daemon processes runs under.
SysMaint
Project name for system maintainers, the people who installed new
software on the system.
System M
Multics system in Phoenix used by Honeywell employees for Multics
development and for other Honeywell work.
T&D
Test and Diagnostic. Until late in the 70's, all T & D on Multics
hardware was performed by field engineers running offline tools
provided by a different part of the GE (or Honeywell) corporation.
See Online T & D.
tape
Multics used tape for file backup, for disk snapshots when the system
is down, for T&D's, and for occasional file interchanges with other
systems. Tape software was not considered very important, it was
considered a throwback to an earlier age. There were no "job stacks
from tape", "spooling to and from tape", or the like. [BSG]
TCP/IP
Transmission Control Protocol/Internet Protocol.
ARPANet packet protocols introduced in the late 1970s, replacing the
older "NCP" protocols.
Tech Square
Technology Square. Office complex behind MIT. 545 Tech
Square was the office building that housed Project MAC. 575 Tech
Square was the building where CISL and the Cambridge Project were
located. Also located in 545 Tech Square was the IBM Cambridge
Scientific Center, home of CP/CMS.
TECO
Text Editor and Corrector. An editor first written for TX-0 by Dan
Edwards, then ported to the PDP-1 thru 10, CTSS, Multics, and other
systems. Stallman's original ITS EMACS was written as a set of
editor macros in TECO.
ted
For "text editor", a powerfully enhanced qedx by Jim Falksen of
Honeywell Phoenix, mid '70's. Once Multics had acquired product
status and a certain amount of momentum, new tools were not
assimilated as rapidly and enthusiastically as theretofore. While
the weakness and ugliness of qedx, especially its internal
"programming language" daily presented obstacles to its many users,
any attempt to replace or enhance it rapidly became bogged down in
the "general editor issue", the "right way to design an editor", "how
to have a Multicious editor", compatibility with multitudinous extant
qedx "programs", etc., all problems larger than we could solve, and
official progress on the "editor front" seemed impossible. Falksen
ignored all this, creating ted, enhancing it, and adding features on
request for his grateful and enthusiastic private user community, not
at all unlike the development paradigm undertaken at the height of
this by Emacs, which broke the "editor" impasse by wholly usurping
the terms of discourse in 1978. [BSG] The ted editor was added to
the Multics product line, as an unbundled product, sometime in the
80s.
Telefunken TR440
?
terminal type
A character string that identifies the kind of terminal device.
terminal operators
These were the CISL staff who typed in the Multics documentation
written by the technical writers. They spent a lot of time
programming in runoff/compose.
terminate
Said of a segment. To "make unknown", to remove the binding between
a segment number and a file in a process, the opposite and
complementary operation of initiate. Sort of like closing a file,
but not quite, for no promises of the file being consistent on disk
are made: being known, which is orthogonal to being active, is a
state of relation between a process and a segment, not a file and the
disk. From a data reliability viewpoint, this is a major deficiency
of the Multics scheme. [BSG]
TeX
?
thrashing
A condition in which the combined working set of the programs a
time-sharing system is attempting to run simultaneously exceeds the
physical memory available, so that the system spends most of its time
generating and servicing page faults. First named by Peter Denning.
Multics designers spent a lot of time trying to prevent and overcome
thrashing.
TMG
TransMoGrifier. Compiler-compiler language created by Doug McClure
at Texas Instruments about 1964. Used by Doug McIlroy and Bob Morris
to write EPL.
TN1200
A GE hardcopy terminal that ran at 1200 baud.
Toshiba
Multics customer. Two sites in Japan.
TP
Transaction Processing. Feature added in MR7.0.
TPR
Temporary Pointer Register - a tripartite processor register in which
the effective address of instruction operands is developed. The
three components are segment, ring, and offset (location within that
segment) of reference. At the time of a page fault or other
mid-instruction exception, the TPR value(s) saved in the processor
state identify the address faulted on. Not valid for interrupts,
though, which only occur between instructions. See TRR.[BSG]
TR
Trouble Report. Multics had its own database for tracking and
reporting on problems.
TRR
Temporary Ring Register - the ring component of the TPR (Temporary
pointer register). The notion of the ring of reference is a subtle
and ingenious one, innovated on Multics through the thesis of Michael
D. Schroeder. It is defined as the lowest level of privilege
involved in the computation of an address up to this point. Starting
equal to the ring of execution (see PRR), the TRR is raised (made
"less privileged") as indirect words are indirected through - both
the ring number stored in the indirect words and the write bracket
(the highest ring that could have put that number or pointer there)
of the segment containing the indirect word are factored in. The
right to access data at every single processor cycle is computed by
comparing not the PRR, but the TRR with the ring brackets of the
segment being referenced. This is done automatically, and did not
require "adjust requester privilege level" (based on the same
concept) as on the Intel architectures which pay tribute to it.
Through this mechanism, the supervisor is able to reference
user-supplied arguments (passed by pointer, as PL/I requires) without
fear of security breach.[BSG]
traffic control
The supervisor subsystem that performed the functions of controlling
process/processor binding and scheduling (see scheduler), i.e., the
allocation and management of processor resources. Also included
under this rubric are interprocess communication. Multics traffic
control is based upon Jerry Saltzer's Ph.D. thesis on this subject.
Trinity
The management group consisting of the leaders of MIT (Robert M.
Fano), GE (C. Walker Dix), and BTL (Edward E. David Jr.).
Triumvirate
The next-level management group, reporting to the Trinity, of the
programming managers of MIT (F. J. Corbato), GE (A. L. Dean Jr.),
and BTL (Peter G. Neumann). Reporting to the Triumvirate were two
Project Consultants (Edward L. Glaser and Jerome H. Saltzer), the
Project Administrator (George D. Bennett), the Development Director
(Robert C. Daley), and the Integration Director (Izhar Shy).
TSP
Cambridge Project feature?
TSS
IBM's time-sharing system for System/360.
TTY DIM
Device interface module for terminals. Hardcore software that
handles communications, talked to the FNP. Pronounced "titty-dim."
TTY37
Teletype Model 37. First terminal to use full ASCII. 150 baud. See
message coordinator.
UBCC
Multics site: University of Birmingham Computer Centre (Birmingham,
England)
UC
Multics site: University of Calgary (Calgary, Alberta, Canada)
UIM
Universal Interface Module. Feature designed but never implemented
for 645 Multics.
UK file transfer & RJE
?
UK mail & network addressing
?
UK Transport Service
?
unbundled
Costs extra. Some Multics software was not "bundled" with the
hardware purchase, but instead had an additional charge. Typically
there would be several prices: a large amount for a one-time paid-up
license, or an initial fee and then a monthly license charge. This
practice, of unbundling software and leasing it to the customer for a
monthly fee, was introduced by IBM about 1970, and represented a
radical shift in computer finance. Multics took to it reluctantly.
It led to complications, since we had to avoid dependencies from
standard software on unbundled products: e.g. we couldn't use MRDS to
store accounting data and produce reports. Unbundled software was
stored in >system_library_unbundled, also called >unb. [BSG adds:]
Since division of function by sharing of programs in a single large
address space is one of the basic features of Multics, unbundling
threatened this fundamental design goal. For example, the editor
could not rely on the "good" mail system, because it might not be
there. Major improvements to functionality were relegated to options
available for a price, and old, inadequate, embarrassingly obsolete
tools could not be phased out. The inevitable transition from the
age of software supplied with hardware to that of the competitive
software vendor is at the heart of it, though. Emacs was one of the
first unbundled products.
unclaimed signal
If a signal is raised, and the runtime cannot find a condition
handler for it, it searches for a handler for "unclaimed_signal."
UNCP
Universal Network Control Program. This I/O subsystem ran on a
DN355. Honeywell communications software. Multics worked with it.
unique name
See shriek name.
UNIX
UNIX is a trademark of AT&T Bell Laboratories, or somebody.
udd
(or UDD, user_dir_dir) Alternate names of the directory
>user_dir_dir, whose subdirectories are project directories, whose
subdirectories in turn are users' home directories. Compare PDD.
User Control
Subsystem that handled login, user registration, projects, and so on.
USGS
US Geological Survey. Multics customer. Had 3 systems, in Menlo
Park, Reston, and Denver.
USL
University of Southwestern Louisiana. Multics customer. Swamp on
campus with real alligators. Used Delta Data 4000's as terminals.
vfile_
The Multics DIM that allowed users to access segments with read/write
calls.
Video System
Supported a character based window system and a real-time input
editor much like the UNIX ksh command line editor. Followed on the
heels of Multics Emacs.
VIP7760
Honeywell video terminal. Synchronous device, required a controller.
Lacking insert or delete lines or characters, it was not well suited
for screen-managed video at less than 9600 baud. Prior to Emacs,
video terminals were in general less desirable than good printing
terminals for any number of reasons.[BSG]
VIP7801
Honeywell video terminal. Worked asynchronously or synchronously.
Complete with insert and delete lines and characters and
nicely-chiseled high-resolution characters, this was an excellent
Emacs terminal popular in the Multics development community, although
its high cost kept it from being used almost anywhere outside
Honeywell. Developed by Honeywell in Billerica, MA. [BSG]
virtual cpu
The system kept track of "virtual" CPU usage for each user, that is,
CPU usage not counting overhead. Interrupt service time was
subtracted from a process's "real" CPU usage so that a user program
would incur repeatable CPU charges for running the same program,
regardless of load.
virtual memory
As in "The Multics Virtual Memory", a paper by Clingen, Bensoussan,
and Daley. A Multics process accesses all the data (it is allowed
to) on the system as part of a huge, two-dimensional address space
(see segmentation). There is no "file I/O", no buffers, no read-in,
no write-out. All the data on the system is "virtual memory", paging
being handled completely transparently. [BSG]
VisiCalc
Microcomputer spreadsheet developed by Multicians Frankston and
Bricklin.
VLSI Design software
?
VMM
Virtual Machine Monitor. A virtual machine implementation done by
Russ McGee of GE Phoenix and a bunch of AEPs. Users could run
virtual 645s and 635s, and run GECOS and Multics under control of the
VMM "Hypervisor." Comparable to IBM's CP-67. Never a product.
volume backup
The volume dumper dumped by physical volumes, like BOS save, but ran
while the system was up. Not possible until after NSS. Programmed
by Dave Vinograd.
volume pool
RCP concept. A volume pool could allocate volumes,
e.g. "system-scratch-tape."
VOS
Stratus operating system, influenced by Multics, developed by
Multicians.
VPI
Virginia Polytechnic Institute, Blacksburg, VA. Multics customer.
VTOC
Volume Table of Contents. OS/360 volumes had these, and NSS adopted
the term for its similar database. By defining the segment catalogue
of a disk pack as a fixed-record, fixed-form database, a substantial
advance in reliability was achieved.
VTOCE
VTOC entry. Very like an inode in the UNIX file system. Contains
the activation attributes of a segment (date/time modified, page
fault count, etc.) and its file map.
VW
Multics site: Volkswagen of America (Troy MI)
wired
Today called "page-locked". Said of code or data that is fixed in
physical memory, either by virtue of being in unpaged segments
(individual segments can either be paged or contiguous in memory), or
in segments whose pages are marked as being non-removable. This is
done for code and data that must be either be run or referenced at an
equal or lower conceptual level than the I/O and page management
routines doing the paging, data actually being transferred to and
from I/O controllers, or code which must compete with such code for
resources and its data. In practice, this means page control, the
scheduler, the disk routines, low-level I/O control routines,
interrupt handlers and vectors, page tables, and that subset of the
PL/I runtime (see pl1_operators_) that is used by any of those
aforementioned that are written in PL/I. Except as an experiment,
code or data was never wired for performance reasons. [BSG]
WORDPRO
Marketing package for compose plus Emacs.
working directory
The directory used as the implicit prefix of relative path names.
See search rules.
working set
The set of pages, at any time, required in core for a program to make
reasonable progress. Defined by Peter Denning.
write bracket
The range of rings which can write a given segment. If the segment's
ring brackets are 1, 5, 5, the write bracket is rings 0 to 1. Also
sometimes used to refer to that upper inclusive limit itself. [BSG].
X25
?
xforum, xmail
These were "Executive" versions of the forum and mail commands. That
is, they were menu-driven interfaces, slow and simple. [BWS]
Unbundled products.
XR Index Register. The 645 and 6180 each had eight of them.
Containing only 18 bits, they cannot contain pointers when used in a
Multics environment.[BSG] See ABR.
XRAY
Jerry Grochow's tool for debugging 645 Multics. Consisted of a PDP7
on the fifth floor of Tech Square, linked to a special GIOC channel.
The channel was in a send/receive loop, and the PDP7 sent address
ranges to the GIOC, received the contents, and displayed them on its
tube.
XTS200
Honeywell product name for the SCOMP.
ZARF
Air Force/MITRE tiger team project that cracked Multics security.
"Zarf" is Turkish for a coffee cup, applied by the Air Force to those
white disposable cups that fit into a brown holder with a handle,
which they called a finjan, also the appropriate Turkish term.
Zero Six Dog
Field Engineers' jargon for "PRG06D", the 6080/6180 T & D program
which was initially the only program that knew how to load firmware
into the "MPC"s (tape/disk/unit record microprogrammed controllers).
Bringing up and interacting with the T & D environment was extremely
difficult (as well as requiring the system to be down), and
initially, no Multicians could do it. This situation helped impel
Noel Morris to develop on-line firmware loading for MPC's (a product
requirement), but that was still of no value for the disk and tape
controllers on which the system had to be brought up. That impelled
Bernie Greenberg (1974) to learn to run "the old dog", decode the T &
D programs and invent self-loading Multics firmware tapes, which he
and Noel then in concert developed into self-booting,
self-firmware-loading BOS tapes.[BSG]
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