Applications and Successors
Lyons used LEO I initially for valuation jobs, but its role was extended to include payroll, inventory, and so on. One of its early tasks was the elaboration of daily orders which were phoned in every afternoon by the shops and used to calculate the overnight production requirements, assembly instructions, delivery schedules, invoices, costings, and management reports. This, arguably, was the first instance of an integrated management information system plus a computerised call centre. The LEO project was also a pioneer in outsourcing: in 1956, Lyons started doing the payroll calculations for Ford UK and others on the LEO I machine. The success of this led to the company dedicating one of its LEO II machines to bureau services. Later, the system was used for scientific computations, as well. Met Office office staff used a LEO I before the Met Office bought its own computer, a Ferranti Mercury, in 1959.
In 1954, with the decision to proceed with LEO II and interest from other commercial companies, Lyons formed LEO Computers Ltd. The first LEO III was completed in 1961. This was a solid-state machine with a 13.2s cycle time ferrite core memory. It was micro-programmed and was controlled by a multi-tasking operating system. In 1963, LEO Computers Ltd was merged into English Electric Company and this led to the breaking up of the team that had inspired LEO computers. English Electric Company continued to build the LEO III, and went on to build the faster LEO 360 and even faster LEO 326 models, which had been designed by the LEO team before the takeover. All LEO IIIs allowed concurrent running of as many as 12 application programs through the "Master program" operating system. Some, primarily producing telephone bills, were still in commercial use with GPO Telephones, forerunner of British Telecom, until 1981, which remained usable through parts cannibalised from redundant LEOs purchased by the GPO.
Users of LEO computers programmed in two coding languages: Intercode, a low-level assembler type language; and CLEO (acronym: Clear Language for Expressing Orders), the COBOL equivalent.
Many users fondly remember the LEO III and enthuse about some of its quirkier features, such as having a loudspeaker connected to the central processor which enabled operators to tell whether a program was looping by the distinctive sound it made. Many intermittent faults were due to dry joints and could be temporarily fixed by briskly strumming the card handles!
English Electric LEO Computers Ltd or English Electric Leo Marconi (EELM) eventually merged with International Computers and Tabulators (ICT) and others to form International Computers Limited (ICL) in 1968. In the 1980s, there were still ICL 2900 mainframes emulating LEO programs.
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