CTSS, which stood for the Compatible Time-Sharing System, was one of the first time-sharing operating systems; it was developed at MIT's Computation Center. CTSS was first demonstrated in 1961, and was operated at MIT until 1973. During part of this time, MIT's Project MAC had a second copy of CTSS, but the system did not spread beyond two sites. CTSS was described in a paper presented at the 1962 Spring Joint Computer Conference. 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. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The Massachusetts Institute of Technology, or MIT, is a private research university located in the city of Cambridge, Massachusetts, USA. Its mission and culture are guided by an emphasis on teaching and research grounded in practical applications of science and technology. ... 1961 (MCMLXI) was a common year starting on Sunday (the link is to a full 1961 calendar). ... 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. ...

The "Compatible" in the name refers to compatibility with the standard batch processing OS for the 7094, the Fortran Monitor System (FMS). CTSS ran an unaltered copy of FMS, processing a standard batch stream, in a virtual 7094 provided by its background facility. Background FMS jobs could access tapes normally but could not interfere with foreground time-sharing processes or the resources used to support them.

Although CTSS was not an influential operating system in its technical detail, it was very influential in showing that time-sharing was viable, in the new applications for computers which were first instantiated there, and because of its successor, Multics, which all modern operating systems are intellectually descended from. Multics (Multiplexed Information and Computing Service) was an extraordinarily influential early time-sharing operating system. ...

CTSS had one of the first computerized text formatting utilities, and one of the first inter-user electronic mail implementations. Electronic mail, abbreviated e-mail or email, is a method of composing, sending, and receiving messages over electronic communication systems. ...

MIT Computation Center staff member Louis Pouzin created a command called RUNCOM for CTSS, which executed a list of commands contained in a file; this facility is the direct ancestor of the Unix shell script. RUNCOM also allowed parameter substitution. A shell script is a script written for the shell, or command interpreter, of an operating system. ...

CTSS used a modified IBM 7094 mainframe computer that had two 32,768 36-bit word banks of core memory instead of the normal one. One bank was reserved for the time-sharing supervisory program, the other for user programs. It also had some special memory management hardware, a clock interrupt and the ability to trap certain instructions. Input-output hardware was mostly standard IBM peripherals. These included six data channels connecting to: The IBM 7094 the fourth member of the most popular family of IBMs large second-generation transistorized mainframe computers and was designed for large-scale scientific and technological applications. The first 7094 installation was in September 1962. ... A 16×16 cm area core memory plane of 128×128 bits, i. ...

• printers, punch card readers and punches
• IBM 729 tape drives, an IBM 1301 disk storage, later upgraded to an IBM 1302, with 38 million word capacity
• an IBM 7320 drum memory with 186K words that could load a 32K memory bank in one second (later upgraded to 1/4 second)
• two custom high speed vector graphics displays
• an IBM 7750 transmission control unit capable of supporting up to 112 teleprinter terminals, including IBM 1050 Selectrics and Model 35 Teletypes. Some of the terminals were located remotely and the system could be accessed using the public Telex and TWX networks

CTSS was compatible with the Fortran Monitor System, an older batch computing system that ran on the 7094 computer before CTSS was invented. FMS could run in the background nearly as efficiently as on a 7094 without an OS at all. Running in the background, FMS had access to some tape units and the user 32K bank of core memory. The punch card (or Hollerith card) is a recording medium for holding information for use by automated data processing machines. ... IBM 729s in action The IBM 729 Magnetic Tape Unit was IBMs iconic tape mass storage system from the late 1950s through the mid 1960s. ... Magnetic disk storage was a critical component of the computer revolution. ... Magnetic disk storage was a critical component of the computer revolution. ... Teletype machines in World War II A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. ... The IBM Selectric typewriter (occasionally known as the IBM Golfball typewriter) is the electric typewriter design that brought the typewriter into the electronic age starting in 1961. ... Optical Telegraf of Claude Chappe on the Litermont near Nalbach, Germany Telegraph and telegram redirect here. ... Fortran (also FORTRAN) is a statically typed, compiled, programming language originally developed in the 1950s and still heavily used for scientific computing and numerical computation half a century later. ... Batch processing is the sequential execution of a series of programs (jobs) on a computer. ...

Multics, which was also developed by Project MAC, was started in the 1960s as a successor to CTSS, for future use in multiple-access computing. Multics, infamously, was the operating system that led to the development of Unix in 1969. The 1960s decade refers to the years from 1960 to 1969, inclusive. ... Unix or UNIX is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T Bell Labs employees including Ken Thompson, Dennis Ritchie, and Douglas McIlroy. ... 1969 (MCMLXIX) was a common year starting on Wednesday (the link is to a full 1969 calendar). ...

ITS, the Incompatible Timesharing System, another early, revolutionary, and influential MIT time-sharing system, was produced by people who disagreed with the direction taken by Multics; the name was a hack on CTSS, as the name of Unix was later a hack on Multics. 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. ITS development was initiated in the late 1960s by those (the majority of the MIT AI Lab... To meet Wikipedias quality standards, this article or section may require cleanup. ...

See also

• Fernando J. Corbató, project leader

Fernando José Corbató (born July 1, 1926) is a prominent computer scientist, notable as a pioneer in the development of time-sharing operating systems. ...

References

• F. J. Corbató, M. M. Daggett, R. C. Daley, An Experimental Time-Sharing System (IFIPS 1962)
• Robert M. Fano, The MAC System: A Progress Report (MIT Project MAC, 1964) describes the usage of CTSS
• Jerome H. Saltzer, CTSS Technical Notes (MIT Project MAC, 1965) describes the internals of CTSS in some detail
• Jerome H. Saltzer, Manuscript Typing and Editing (MIT Computation Center, 1964) describes the world's first computerized text formatting system

External links

• John McCarthy, Reminiscences on the History of Time Sharing presents the origin of the concept of time-sharing
• The IBM 7094 and CTSS: personal memoir of a system programmer on CTSS
• The Origin of the Shell describes the evolution of RUNCOM into the modern shell
• CTSS Source in Paul Pierce's collection.