Time Sharing Limited (TSL) was the United Kingdom's first time sharing computer services company.

1st. Generation System

Time Sharing Limited was founded in 1967 by Richard ("Dick") Evans who had been impressed by Digital Equipment Corporation's minicomputers. It started service from a small office on Great Portland Street, London, with a dual, fault-tolerant system consisting of a front-end switch directing traffic to two units, each consisting of a PDP-7 and a

PDP-8 The PDP-8 is a 12-bit minicomputer that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units being sold over the model's lifetime. Its basic design follows the pioneeri ...

. The PDP-7 interpreted messages and the PDP-8 ran the appropriate application. A

PDP-9 The PDP-9, the fourth of the five 18-bit minicomputers produced by Digital Equipment Corporation, was introduced in 1966. A total of 445 PDP-9 systems were produced, of which 40 were the compact, low-cost PDP-9/L units.. History The 18-bit PDP ...

controlled access to persistent storage based on

NCR CRAM CRAM, or Card Random-Access Memory, model 353-1, was a data storage device invented by NCR, which first appeared on their model NCR-315 mainframe computer in 1962. It was also available for NCR's third generation NCR Century series as the NCR/6 ...

Memory. The system used the

TELCOMP TELCOMP was a programming language developed at Bolt, Beranek and Newman (BBN) in about 1964 and in use until at least 1974. BBN offered TELCOMP as a paid service, with first revenue in October 1965. The service was sold to On-Line Systems, Inc. ...

interpretive language that had been developed by

Bolt, Beranek and Newman Raytheon BBN (originally Bolt Beranek and Newman Inc.) is an American research and development company, based next to Fresh Pond in Cambridge, Massachusetts, United States. In 1966, the Franklin Institute awarded the firm the Frank P. Brown ...

. Customers leased a modem from the General Post Office (later

British Telecom BT Group plc (trade name, trading as BT and formerly British Telecom) is a British Multinational corporation, multinational telecommunications holding company headquartered in London, England. It has operations in around 180 countries and is th ...

) and a Westrex

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 machines. The Teletype Corporation introduced the Model 33 as a commercial product in 1963 aft ...

from TSL. Line speeds were limited to 110 Baud (about 10 characters per second PS. Customers were charged for each minute that they were logged onto the system. The initial persistent storage system was based on

units, which used magnetic cards hanging from a digitally addressed set of rods.

Applications

TSL quickly developed a range of applications for business, scientific and engineering customers. The most highly used were the PERT application, for critical path network planning, and an embryonic corporate modeling tool that could be regarded as a forerunner to spreadsheets. TSL soon licensed programs from other DEC customers, including the Nastran finite element modeling system and an early Database Management System called Oliver. TSL's Consultancy Division also developed applications, or modified services, for its customers. The most advanced applications used the

MACRO-10 MACRO-10 is an assembly language with extensive macro facilities for DEC's PDP-10-based Mainframe computer systems, the DECsystem-10 and the DECSYSTEM-20. MACRO-10 is implemented as a two-pass assembler. Programming examples A simple " Hello, ...

assembly language.

2nd. Generation System

TSL introduced its first high throughput system in early 1970, based on a

PDP-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especi ...

, later known as the DECSystem-10, housed in London offices at the corner of Great Portland Street and Devonshire Street. The service eventually had two powerful systems for continuous service and a third, smaller system as a backup. Storage consisted of disk drives, tape decks and Bryant magnetic drums for swap space. The operating system was

TOPS-10 TOPS-10 System (''Timesharing / Total Operating System-10'') is a discontinued operating system from Digital Equipment Corporation (DEC) for the PDP-10 (or DECsystem-10) mainframe computer family. Launched in 1967, TOPS-10 evolved from the earlier ...

. The new service could support batch, remote job entry, time sharing and

real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...

loads. It was accessible via a range of terminal devices, including 30 CPS Texas Instruments Silent 700 portable units with an acoustic modem to Tektronix storage tubes, which ran at around 2,400 CPS. Fortran II was added in addition to TELCOMP III. Multiplexers were set up in Birmingham and Edinburgh to reduce line charges. Customers were charged for connect time, application usage, file storage, tape and card deck transfers and line printer output.

Customers and Acquisition

By 1973 TSL was well established, with customers that included the Greater London Council, Foster Wheeler, Baring Bros., British Shipbuilding Research Association, Mather & Platt, London Weekend Television, the Metropolitan Police, Unilever, Lloyds and the Royal Signals. Time Sharing Limited was acquired by

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in 1974.

Citations

{{reflist Defunct technology companies of the United Kingdom British companies disestablished in 1974 British companies established in 1967