This article covers the evolution of time-sharing systems, providing links to major early
time-sharing
In computing, time-sharing is the Concurrency (computer science), concurrent sharing of a computing resource among many tasks or users by giving each Process (computing), task or User (computing), user a small slice of CPU time, processing time. ...
operating systems, showing their subsequent evolution.
The meaning of the term ''time-sharing'' has shifted from its original usage. From 1949 to 1960, time-sharing was used to refer to multiprogramming; it evolved to mean multi-user interactive computing.
Time-sharing
Time-sharing was first proposed in the mid- to late-1950s and first implemented in the early 1960s. The concept was born out of the realization that a single expensive computer could be efficiently utilized by enabling
multiprogramming
In computing, multitasking is the concurrent execution of multiple tasks (also known as processes) over a certain period of time. New tasks can interrupt already started ones before they finish, instead of waiting for them to end. As a result ...
, and, later, by allowing multiple users simultaneous
interactive access.
In 1984,
Christopher Strachey
Christopher S. Strachey (; 16 November 1916 – 18 May 1975) was a British computer scientist. He was one of the founders of denotational semantics, and a pioneer in programming language design and computer time-sharing.F. J. Corbató, et al., T ...
wrote he considered the change in the meaning of the term ''time-sharing'' to be a source of confusion and not what he meant when he wrote his original paper in 1959.
Without time-sharing, an individual user would enter bursts of information followed by long pauses; but with a group of users working at the same time, the pauses of one user would be filled by the activity of the others. Similarly, small slices of time spent waiting for disk, tape, or network input could be granted to other users. Given an optimal group size, the overall process could be very efficient.
Each user would use their own
computer terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. Most early computers only had a front panel to input or display ...
, initially electromechanical
teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point (telecommunications), point-to-point and point- ...
s such as the
Teletype Model 33
The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. It is less rugged and cost less than earlier Teletype models. The Teletype Corporation introduced the Model 33 as a commercial product in 1963, after ...
ASR or the
Friden Flexowriter; from about 1970 these were progressively superseded by
CRT
CRT or Crt most commonly refers to:
* Cathode-ray tube, a display
* Critical race theory, an academic framework of analysis
CRT may also refer to:
Law
* Charitable remainder trust, United States
* Civil Resolution Tribunal, Canada
* Columbia ...
-based units such as the
DEC VT05,
Datapoint 2200
The Datapoint 2200 was a mass-produced programmable terminal usable as a computer, designed by Computer Terminal Corporation (CTC) founders Phil Ray and Gus Roche and announced by CTC in June 1970 (with units shipping in 1971). It was initially ...
and
Lear Siegler
Lear Siegler Incorporated (LSI) is a diverse American corporation established in 1962. Its products range from car seats and brakes to weapons control systems for military fighter planes. The company's more than $2 billion-a-year annual sales come ...
ADM-3A
The ADM-3A is an early influential video display terminal, introduced in 1976. It was manufactured by Lear Siegler and has a 12-inch screen displaying 12 or 24 lines of 80 characters. It set a new industry low single unit price of $995. Its ...
.
Terminals were initially linked to a nearby computer via
current loop
In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors. Only one current level can be present at any time.
A major application of current loops is the industry ...
or
serial cable
A serial cable or RS-232 cable is a electrical cable, cable used to transfer information between two devices using a serial communication protocol. The form of connectors depends on the particular serial port used. A cable wired for connecting two ...
s, by conventional
telegraph circuits provided by
PTTs and over specialist digital
leased line
A leased line is a private telecommunications circuit between two or more locations provided according to a commercial contract. It is sometimes also known as a private circuit, and as a data line in the UK. Typically, leased lines are used by ...
s such
T1.
Modem
The Democratic Movement (, ; MoDem ) is a centre to centre-right political party in France, whose main ideological trends are liberalism and Christian democracy, and that is characterised by a strong pro-Europeanist stance. MoDem was establis ...
s such as the
Bell 103 and successors, allowed remote and higher-speed use over the
analogue voice telephone network.
Family tree of major systems
See details and additional systems in the table below. Relationships shown here are for the purpose of grouping entries and do not reflect all influences. The Cambridge Multiple-Access System
was the first time-sharing system developed outside the United States.
System descriptions and relationships
See also
*
History of CP/CMS has many period details and sources.
*
Timeline of operating systems
Notes
References
{{Time-sharing operating systems
History of software
Time-sharing system evolution