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ITS, the Incompatible Timesharing System, was an early, revolutionary, and influential MIT time-sharing operating system; it was developed principally by the Artificial Intelligence Laboratory at MIT, with some help from Project MAC. The Massachusetts Institute of Technology, or MIT, is a research and educational institution located in the city of Cambridge, Massachusetts, USA. MIT is a world leader in science and technology, as well as in many other fields, including management, economics, linguistics, political science, and philosophy. ...
Alternate uses: see Timesharing Time-sharing is an approach to interactive computing in which a single computer is used to provide apparently simultaneous interactive general-purpose computing to multiple users by sharing processor time. ...
In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ...
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Project MAC, later the MIT Laboratory for Computer Science (LCS), was a research laboratory at MIT. Project MAC would become famous for groundbreaking research in operating systems, artificial intelligence, and the theory of computation. ...
ITS development was initiated in the late 1960s by those (the majority of the MIT AI Lab at that point in time) who disagreed with the direction taken by Project MAC's Multics project (which had started in the mid 1960s), particularly such decisions as the inclusion of powerful system security. The name was chosen by Tom Knight as a hack on the earliest MIT time-sharing operating system, the Compatible Time-Sharing System, which dated from the early 1960s. The 1960s in its most obvious sense refers to the decade between 1960 and 1969, but the expression has taken on a wider meaning over the past twenty years. ...
Multics (Multiplexed Information and Computing Service) was an extraordinarily influential early time-sharing operating system. ...
Tom Knight is the name of the station manager of the University of Surreys Student Radio Station, GU2 Radio Tom Knight is also a senior research scientist in the MIT Artificial Intelligence Laboratory and the MIT EECS department. ...
A hack in progress in Lobby 7 at MIT. Hack is a term in the slang of the technology culture which has come into existence over the past few decades. ...
CTSS, which stood for the Compatible Time-Sharing System, was one of the first time-sharing operating systems; it was developed at Project MAC at MIT. CTSS was first published, as well as operated in a time-sharing environment, in 1961; in addition, it was the system with the first...
ITS was initially developed for the Digital Equipment Corporation PDP-6 computer, and later moved to the PDP-10 once it became available, where it saw the majority of its development and use. Although not used much after 1982 or so, ITS was run at MIT until 1990, and then until 1995 at the Stacken Computer Club in Sweden. Digital Equipment Corporation was a pioneering company in the American computer industry. ...
The PDP-6 (Programmed Data Processor-6) was a computer model developed by Digital Equipment Corporation (DEC) in 1963. ...
The PDP-10 was a computer manufactured by Digital Equipment Corporation (DEC) from the late 1960s on; the name stands for Programmed Data Processor model 10. It was the machine that made time-sharing common; it looms large in hacker folklore because of its adoption in the 1970s by many...
Among numerous interesting features and oddities, the ITS top-level command interpreter was the PDP-10 machine language debugger (DDT), whose commands looked like line noise to the uninitiated. Screenshot of a sample Bash session, taken on Linux. ...
Dynamic Debugging Technique, or DDT, was the name of several debugger programs originally developed for DEC hardware, originally known as DEC Debugging Tape because it was distributed on paper tape. ...
In science, and especially in physics and telecommunication, noise is fluctuations in and the addition of external factors to the stream of target information (signal) being received at a detector. ...
Its main editor for many years, TECO, was programmable in a similar-looking gibberish. The EMACS editor is a descendant of a collection of TECO macros, now much developed. TECO (pronounced /teekoh/; originally an acronym for [paper] Tape Editor and COrrector, but later Text Editor and COrrector) was a text editor developed at MIT in the 1960s and modified by just about everybody. With all the dialects included, TECO may have been the most prolific editor in use...
The GNU Emacs interface, running in a graphical environment. ...
Among other significant and influential software subsystems which were developed on ITS, the Macsyma symbolic algebra system is probably the most important; the GNU INFO help system, MacLisp (the precursor of EmacsLisp and CommonLisp), and EMACS was also started on ITS. Macsyma is a computer algebra system that was originally developed from 1967 to 1982 at the MIT AI Lab as part of Project MAC. In 1982, MIT submitted a copy of Macsyma to the United States Department of Energy, which was one of the major funders of Macsyma development. ...
GNU is a free software operating system. ...
MacLisp is a dialect of the Lisp programming language. ...
The GNU Emacs interface, running in a graphical environment. ...
The Jargon File also started out life on ITS. The Jargon File is a glossary of hacker slang. ...
Significant technical features
ITS was an operating system with many revolutionary features; for some significant ones, it was the first to deploy them. Among them were: - It had the first device-independent graphics terminal output; programs generated generic commands to control screen content, which the system automatically translated into the appropriate character sequences for the particular type of terminal operated by the user.
- A general and powerful mechanism for implementing virtual devices in software which ran in user processes (which were called "jobs" in ITS).
- Using this mechanism, it provided transparent inter-machine filesystem access (almost certainly the first operating system to do so). The ITS machines were all connected to the ARPAnet, and a user on one could perform any operation on a file on one of the other machines that they could on files on the local machine.
- Sophisticated process management; user processes were organized in a tree hierarchy, and a superior process could control a large number of inferior processes. Any inferior process could be frozen at any point in its operation, and any of its state (including contents of the registers) examined; the process could then be restarted without any problems. (This facility is now in one of the GNU tools.)
- An advanced software interrupt facility that allowed user processes to operate asynchronously, using complex interrupt handling mechanisms.
- PCLSRing, a powerful and subtle mechanism which provided what appeared (to user processes) to be non-blocking, safely interruptible system calls. No process could ever observe any process (including itself) in the middle of executing any system call.
Many of these, and numerous other significant advances, were later picked up by other operating systems. ARPANET logical map, March 1977. ...
GNU is a free software operating system. ...
PCLSRing is the term used in the ITS operating system for a consistency principle in the way one process accesses the state of another process. ...
User environment The environment seen by ITS users was philosophically significantly different from that provided by most operating systems at the time. - Initially there were no passwords, and a user could work on ITS without even logging on. Logging on was considered polite, though, so people knew when you were connected.
- All users could bring the system down, but a message was broadcast to say who was doing it.
- All files were editable by all users.
- All users could talk with instant messaging on another's terminal, or they could use a command (SHOUT) to ask all active users for help.
- Users could see what was happening on another's terminal. The user being watched was informed, and could kill the viewer's session. This facility was later disabled in an interesting way: it looked like the session was killed, but was not.
- Tourists - guest users either at MIT AI Lab terminals, or over the ARPAnet - were permitted. A policy was later published on tourist access.
Original developers Richard D. Greenblatt is a programmer. ...
Tom Knight is the name of the station manager of the University of Surreys Student Radio Station, GU2 Radio Tom Knight is also a senior research scientist in the MIT Artificial Intelligence Laboratory and the MIT EECS department. ...
References - Bawden, Allen (n.d.) PCLSRing: Keeping Process State Modular
- Chiou, S; Music, C; Sprague, K; Wahba,R (2001). "A Marriage of Convenience: The Founding of the MIT Artificial Intelligence Laboratory." (pdf)
- Eastlake, Donald E (1969). ITS Reference Manual, Version 1.5, (MIT AI Laboratory) documents a very early version of the system (Warning: very large pdf- scanned page images)
- Eastlake, Donald E. (1972). ITS Status Report (MIT AI Laboratory) documents a somewhat later, but still fairly early, version (Warning, very large pdf- scanned page images)
- Lin, Yuwei (2004). “Epistemologically Multiple Actor-Centered Systems: or, EMACS At Work! Ubiquity 5(1). (pdf file)
- Williams, S. (2002). Free as in Freedom: Richard Stallman's Crusade for Free Software." Petaluma, CA: O'Reilly.
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