In computing , time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking at the same time. [1]

Its introduction in the 1960s and emergence as the model of computing in the 1970s represented a major shift in the history of computing.

By Allowing a wide number of users to interact CONCURRENTLY with a single computer, timeshare Dramatically lowered the cost of providing good capability computing, made it feasible for Individuals and organisms to use a computer without owning one, [2] and Promoted the interactive use of computers and the development of new interactive applications .


Batch processing

Main article: Batch processing

The earliest computers were extremely expensive, and very slow in comparison to later models. Machines were typically dedicated to a particular set of tasks and operated by the company’s control panels by means of switches in order to load and run a series of programs. These programs might take hours, or even weeks, to run. As computers grew in speed, run times dropped, and soon became a concern. Batch processing methodologies evolved to decrease these “dead periods” by queuing up programs, the next would start.

To support a batch processing operation, a number of comparatively inexpensive card punch or paper tape writers have been used by their “offline” program programmers. When typing (or punching) was completed, the programs were submitted to the operations team, which scheduled them to be run. Important programs were started quickly; how long before less important programs were started unpredictable citation needed ] . When the program was finally completed, the output was returned to the programmer. The complete process might take days, during which time the programmer could never see the computer.

The alternative of allowing the user to operate the computer directly to the far too expensive. This was because users could have long periods of code while idle. This situation was largely limited to large groups of people. Stanford students made a short film humorously critiquing it. [3] They experimented with new ways to interact directly with the computer, a field known as human-computer interaction .


Time-sharing was developed out of the realization that a single user would make inefficient use of a computer, a large group of users together would not. Reviews This was due to the pattern of interaction: Typically an individual user ENTERED bursts of information Followed by long pauses goal is group of users working at the Sami time Would mean que la breaks of one user Would Be filled by the activity of the others. Given an optimal group size, the overall process could be very efficient. Similarly, small slices of the time spent waiting for disk, tape, or network input could be granted to other users.

The concept is Claimed to-have-been first Described by John Backus in the 1954 summer session at MIT, [4] and later by Bob Bemer In His 1957 article “How to Consider a computer” in Automatic Control Magazine . [5] [6] In a paper published in December 1958 by WF Bauer, [7] he wrote that “The computers would have a number of competing problems. on the computer much like the average household buys power and water from utility companies. ”

Implementing a system able to take advantage of this was initially difficult. [1] [8] [9] Batch processing was effectively a methodological development on the top of the earliest systems. Since computers still ran single programs for single users at any time, the primary change was a time lag between one program and the next. Developing a system that supports multiple users at the same time was a completely different concept. The “state” of each user and their programs would be kept in the machine, and then switched between quickly. This would take up computer cycles, and on the slow machines of this era was a concern. However, as computers are rapidly improving in speed, and especially in size of core memoryin which users’ states were retained, the overhead of time-sharing continually decreased, relatively speaking.

The first project to implement a time-sharing system was initiated by John McCarthy at MIT in 1959, IBM 704 , and more recently modified IBM 709 (one of the first powerful computers for time-sharing). [9] One of the deliverables of the project, known as the Compatible Time-Sharing System or CTSS, was demonstrated in November 1961. CTSS has a good claim to the first time-sharing system and remains in use until 1973. Another contender for the first time-sharing system was PLATO II, created by Donald Bitzer at Robert Allerton Parknear the University of Illinois in early 1961. But this was a special purpose system. Bitzer has long said that the PLATO project would have gotten the patent on time-sharing if only the University of Illinois had not lost the patent for 2 years. [10] Joss began time-sharing service in January 1964. [11]

The first commercially successful time-sharing system was the Dartmouth Time Sharing System . [12]


Throughout the late 1960s and the 1970s, computer terminals have been multiplexed onto large institutional mainframe computers ( centralized computing systems), which in many implementations have been sequentially polled by the computer user. Later technology in interconnections Were interrupt driven, and sacrifice part of thesis used parallel data transfer technologies Such As the IEEE 488 standard. Generally, computer terminals Were Utilized on college properties in much the Sami seats have desktop computers or personal computersare found today. In the earliest days of personal computers, many have been used as smart terminals for time-sharing systems.

The Dartmouth Time Sharing System’s creators wrote in 1968 that “any response time that averages more than 10 seconds destroys the illusion of having one’s own computer”. [13] Conversely, timesharing users thought that their terminal was the computer. [14] With the rise of microcomputing in the early 1980s, time-sharing faded into the background Because individual microprocessors Were Sufficiently inexpensive That a single person Could Have all the CPU timededicated to their needs, even when idle. However, the Internet brought the general concept of time-sharing back into popularity. Expensive corporate server farms costing millions of customers all sharing the same common resources. As with the early serial terminals, the web sites operate primarily under the influence of periods of idle time. This bursting nature permits to be used by many customers, usually with no noticeable communication delays, unless the servers start to get busy.

Time-sharing business

In the 1960s, several companies providing time-sharing services as service bureaus . Early systems used Teletype Model 33 KSR or ASR gold Teletype Model 35 KSR or ASR machines in ASCII environments, and IBM Selectric typewriter- based terminals (especially the IBM 2741 ) with two different seven-bit codes. [15] They would connect to the central computer by dial-up Bell 103A modem or acoustically coupled modemsoperating at 10-15 characters per second. Later terminals and modems supported 30-120 characters per second. The time-sharing system would provide a complete operating environment, including a variety of programming language processes, various software packages, file storage, bulk printing, and off-line storage. It has a load for hours of connect time, a load for seconds of CPU time, and a load for kilobyte-months of disk storage.

Common systems used for time-sharing included the SDS 940 , the PDP-10 , and the IBM 360 . Companies providing this service included GE ‘s GEISCO, IBM subsidiary The Service Bureau Corporation , Tymshare (founded in 1966), National CSS (founded in 1967 and bought by Dun & Bradstreet in 1979), Dial Data (bought by Tymshare in 1968), and Bolt, Beranek, and Newman (BBN). By 1968, there were 32 such service bureaus serving the US National Institutes of Health (NIH) alone. [16] The Auerbach Guide to Timesharing(1973) lists 125 different timesharing services using equipment from Burroughs , CDC , DEC , HP , Honeywell , IBM , RCA , Univac , and XDS . [17]

An example of a UK-based time-sharing business office is OLS Computer Services (UK) Ltd. Previously Leasco Response and later acquired by On-Line Systems of Pittsburgh, PA, the company operated four HP-2000 TSB (Time shared Basic) systems from its Knightsbridge (later Islington) headquarters offering off-the-shelf business as well as raw time to universities. In addition to its HP estate a PDP-10 DEC operating as a front-end processor (FEP) connecting UK users to 16 PDP-11s based DEC in the US. Connectivity was provided via leased Westrex ASR 33 or Data Dynamics 390 punched-tape enabled teletype machines connected via Post Office (formerly GPO) type 2 modems or audio couplers connecting handsets operating at up to 110cps.

Rise and Fall

In 1975, it was said about one of the major super-mini computer manufacturers [18] that “the biggest end-user market currently is time-sharing.” For DEC, for a second largest computer company (after IBM), this was also true: Their PDP-10 and IBM’s 360/67 [19] were widely used [20] by commercial timesharing services such as CompuServe, On-Line Systems (OLS), and Rapidata.

Rapidata as an example

Although many time-sharing services simply closed, Rapidata [21] [22] held on, and became part of National Data Corporation. [23] It was still of sufficient interest in 1982 to be the focus of “A User’s Guide to Statistics”: The Rapidata Timesharing System. [24] Even as revenue fell by 66% [25] and National Data subsequently developed its own problems, attempts were made to keep this timesharing business going. [26] [27] [28]

The computer utility

Beginning in 1964, the Multics operating system was designed as a computing utility , modeled on the electrical or telephone utilities. In the 1970s, Ted Nelson’s original ” Xanadu ” hypertext repository was envisioned as such a service. It seemed as if it was not the case that such consolidation of computing resources would occur as timesharing systems. In the 1990s, the concept was, however, revived in the cloud of cloud computing .


Time-sharing was the first time that multiple processes, owned by different users, were running on a single machine, and these processes could interfere with one another. [29] For example, one process might be different shared resources, another process relied on, such as a variable stored in memory. When only one user was using the system, it would have been possible to have multiple users, but it would have been more likely that they would have been more likely to have.

To prevent this from happening, an operating system needs to be enforced. For example, the operating system might have some variable by a certain process.

The first international conference on computer security in London in 1971 was first driven by the time-sharing industry and its customers. quote needed ]

Notable time-sharing systems

See also: Time-sharing system evolution

Significant early timesharing systems: [17]

  • Allen-Babcock RUSH (Remote Users of Shared Hardware) Time-sharing System on IBM S / 360 hardware (1966) [30] → Tymshare
  • AT & T Bell Labs Unix (1971) → UC Berkeley BSD Unix (1977)
  • BBN PDP-1 Time-sharing System → Massachusetts General Hospital PDP-1D → MUMPS
  • BBN TENEX → DEC TOPS-20 , Foonly FOONEX, MAXC OS at PARC , Stanford Low Overhead Timesharing System (LOTS)
  • Berkeley Timesharing System at UC Berkeley Project Genie → Scientific Data Systems SDS 940 ( Tymshare , BBN , SRI , Community Memory) → BCC 500 → MAXC at PARC
  • Burroughs Time-sharing MCP → HP 3000 MPE
  • Cambridge Multiple Access System was developed for the Titan , the prototype Atlas 2 computer built by Ferranti for the University of Cambridge . [31] This was the first time-sharing system developed outside the United States, and which influenced the future development of UNIX .
  • Compower Ltd., a wholly owned subsidiary of the National Coal Board (Later British Coal Corporation) in the UK. Originally National Coal Board (NCB) Computer Services, it became Compower in 1973 providing computing and time-share services to internal NCB users and as a commercial service to external users. Sold to Philips C & P (Communications and Processing) in August 1994.
  • CompuServe , also branded as Compu-Serv, CIS.
  • Compu-Time, Inc., [17] on Honeywell 400/4000, started in 1968 in Ft. Lauderdale, Florida, moved to Daytona Beach in 1970.
  • CDC MACE, APEX → Kronos → NOS → NOS / VE
  • Dartmouth Time Sharing System (DTSS) → GE Time-sharing → GEn
  • DEC PDP-6 Time-sharing Monitor → TOPS-10 → BBN TENEX → DEC TOPS-20
  • DEC TSS-8 → RSTS-11 , RSX-11 → VAX / VMS
  • HP 2000 Time-Shared BASIC
  • HP 3000 series
  • IBM CALL / 360 , CALL / OS – using IBM System / 360 Model 50
  • IBM CP-40 → CP-67 → CP-370 → CP / CMS → VM / CMS
  • IBM TSO for OS / MVT for OS / VS2 for MVS for z / OS
  • IBM TSS / 360 → TSS / 370
  • International Timesharing Corporation on dual CDC 3300 systems. [17]
  • MIT CTSS → MULTICS (MIT / GE / Bell Labs) → Unix
  • MIT Time-sharing System for the DEC PDP-1 → ITS
  • McGill University MUSIC → IBM MUSIC / SP
  • Michigan Terminal System , IBM S / 360-67 , S / 370 , and successors.
  • Michigan State University SCOPE / HUSTLER System CDC
  • National CSS VP / CSS , on IBM 360 series; Originally based on IBM’s CP / CMS .
  • Oregon State University OS-3, on CDC 3000 series.
  • Prime Computer PRIMOS
  • RCA TSOS → Univac / Unisys VMOS → VS / 9
  • Service in Informatics and Analysis (SIA) , CDC 6600 Kronos .
  • System Development Corporation Time-sharing System, on the AN / FSQ-32 .
  • Stanford ORVYL and WYLBUR , on IBM S / 360-67 .
  • Stanford PDP-1 Time-Sharing System → SAIL → WAITS
  • Time Sharing Ltd. (TSL) [32] on DEC PDP-10 systems → Automatic Data Processing (ADP), the first commercial time-sharing system in Europe and the first dual (fault tolerant) time-sharing system.
  • Tone (TSO-like, for VS1 ), a non-IBM Time-sharing product, marketed by Tone Software Co; TSO required VS2.
  • Tymshare SDS-940 → Tymcom X → Tymcom XX
  • Unisys / UNIVAC 1108 EXEC 8 → OS 1100 → OS 2200
  • UC Berkeley CAL-TSS, on CDC 6400 .
  • XDS UTS → CP-V → Honeywell CP-6

See also

  • cloud computing
  • The Heralds of Resource Sharing , a 1972 film.
  • History of CP / CMS , IBM’s virtual machine operating system (CP) that supported time-sharing (CMS).
  • IBM M44 / 44X , an experimental computer system based on an IBM 7044 used to simulate multiple virtual machines.
  • IBM System / 360 Model 67 , the only IBM S / 360 series mainframe to support virtual memory.
  • Multiseat configuration , multiple users on a single personal computer .
  • Project MAC , a DARPA funded project at MIT famous for groundbreaking research in operating systems , artificial intelligence , and the theory of computation .
  • TELCOMP , an interactive, conversational programming language based on JOSS , developed by BBN in 1964.
  • Timeline of operating systems
  • VAX (Virtual Address eXtension), a computer architecture and family of computers developed by DEC .
  • Utility computing
  • Virtual memory


  1. ^ Jump up to:b December timesharing (1965), by Peter Clark, The Professional December, Volume 1, Number 1
  2. Jump up^ IBM advertised, early 1960s, with a headline: “This man is sharing a $ 2 million computer”
  3. Jump up^ Eisenson, Arthur; and Yager, Heather (1967). Ellis D. Kropotchev Silent Movie. Stanford University, 1967. This student-produced film from Stanford University is a humorous spoof of the trials and tribulations of a college hacker condemned to use batch processing. Originally created by Arthur Eisenson and Gary Feldman, the film gives the viewer a feel for the process of computer programming in the 1960s. Original music by Heather Yager. Computer History Museum, Object ID 102695643. Retrieved on 2013-11-29 fromhttp://www.computerhistory.org/revolution/punched-cards/2/211/2253.
  4. Jump up^ John Backus, Computer Advanced Coding Techniques , MIT 1954, page 16-2. The first known description of computer time-sharing.
  5. Jump up^ Bemer, Bob (March 1957). “Origins of Timesharing” . bobbemer.com . Retrieved June 24, 2016 .
  6. Jump up^ Middleburg, CA (2010). “Searching Publications on Operating Systems”. arXiv : 1003.5525  [ cs.OS ].
  7. Jump up^ Bauer, WF, Computer design from the programmer’s viewpoint (Eastern Joint Computer Conference, December 1958) One of the first descriptions of computer time-sharing.
  8. Jump up^ “There were no command files supported.” – the commands to compile and then ‘link’ to a program that has been typed in each time. As the article adds: “No CCL (Concise Command Language)” referring to the DEC world’s equivalent ofClistandRexx.
  9. ^ Jump up to:b McCarthy, John. “REMINISCENCES ON THE HISTORY OF TIME SHARING” . stanford.edu . stanford.edu . Retrieved 12 March 2017 .
  10. Jump up^ Brian Dear, Chapter 4 – The Diagram,The Friendly Orange Glow, Pantheon Books, New York, 2017; pages 71-72 discuss the development of time-sharing and the University of Illinois loss of the patent.
  11. Jump up^ JC Shaw (1964). “Joss: a designer’s view of an experimental on-line computing system”. Proceeding AFIPS ’64 (Fall, I share) Proceedings of the October 27-29, 1964 fall conference joined computer, I share . pp. 455-464.
  12. Jump up^ dtss.dartmouth.edu/history.php
  13. Jump up^ Kemeny, John G .; Kurtz, Thomas E. (11 October 1968). “Dartmouth Time-Sharing” . Science . 162 : 223-228.
  14. Jump up^ “TRANSCRIPTS OF 1974 National Computer Conference Pioneer Day Session” . Dartmouth Time Sharing System . Dartmouth College.
  15. Jump up^ IBM 2741 Communication Terminal (PDF) . IBM. p. 12.
  16. Jump up^ “Information Technology Corporate Histories Collection”. Computer History Museum. Retrieved on 2013-11-29 fromhttp://www.computerhistory.org/corphist/view.php?s=stories&id=136.
  17. ^ Jump up to:d Auerbach Guide to Time Sharing (PDF) . Auerbach Publishers, Inc. 1973 . Retrieved 2013-11-29 .
  18. Jump up^ Computerworld, June 11, 1975, p. 35
  19. Jump up^ One Two-page IBM print ad was headlined “100 or more people can use IBM’s new time-sharing computer at the same time.” Originals were / are? on e-Bay
  20. Jump up^ p.1425, Encyclopedia of Computer Science, Litton Educational Publishing, Inc.
  21. Jump up^https://groups.google.com/forum/#!topic/alt.folklore.computers/aE4TwORruB8- “I worked for RapiData Timesharing for a year circa 1969 …”
  22. Jump up^ someone else: “I worked there for almost 2 years 1977 to 1979.” alt.folklore.computers / aE4TwORruB8 / EdpKfFAlBncJ
  23. Jump up^ NDC started in 1967, and paralleled Rapidata; see Bloomberg’shttps://www.bloomberg.com/research/stocks/private/snapshot.asp?privcapId=290092
  24. Jump up^ Bruce Bosworth,ISBN 978-089529-1-677
  25. Jump up^ Computerworld, Oct. 6, 1986, p.179, “Rapidata revenue was $ 11 million … in 1986, down from … ($ 31 million in 1982).”
  26. Jump up^ Computerworld, Aug.25.1986, p.5, “National Data Corp. said it is close to reaching an agreement with a buyer of its Rapidata timesharing division.In May, National Data said it would close down … “
  27. Jump up^ National Data Corp Became NDC-Health Corp in 2001 (bizjournals.com/atlanta/stories/2001/10/29/daily25.html)
  28. Jump up^ As for a place in history, Rapidata is listed in ‘The AUERBACH Guide to Time Sharing (1973)’http://bitsavers.informatik.uni-stuttgart.de/pdf/auerbach/GuideToTimesharing_Jan73.pdf
  29. Jump up^ Silberschatz, Abraham; Galvin, Peter; Gagne, Greg (2010). Operating system concepts (8th ed.). Hoboken, NJ: Wiley & Sons. p. 591. ISBN  978-0-470-23399-3 .
  30. Jump up^ “A Brief Description of Privacy Measures in the RUSH Time-Sharing System”, JD Babcock, AFIPS Conference Proceedings, Spring Joint Computer Conference, Vol. 30, 1967, pp. 301-302.
  31. Jump up^ Hartley, DF (1968), The Cambridge multiple-access system: user’s reference manual , Cambridge: Cambridge Univ. Press, ISBN  978-0901224002
  32. Jump up^ “Time Sharing”, James Miller. Retrieved 30 November 2013.

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