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LEO (computer)

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</style><table class="infobox hproduct vevent"><caption class="infobox-title fn summary">LEO I</caption><tbody><tr><td colspan="2" class="infobox-image"><div class="infobox-caption">Logo of LEO Computers Ltd 1954 until 1963</div></td></tr><tr><th scope="row" class="infobox-label">Also known as</th><td class="infobox-data">Lyons Electronic Office I</td></tr><tr><th scope="row" class="infobox-label">Manufacturer</th><td class="infobox-data"><a href="J._Lyons_and_Co." title="J. Lyons and Co.">J. Lyons and Co.</a></td></tr><tr><th scope="row" class="infobox-label">Generation</th><td class="infobox-data">1</td></tr><tr><th scope="row" class="infobox-label">Release date</th><td class="infobox-data">1951 (1951)</td></tr><tr><th scope="row" class="infobox-label"><a href="Central_processing_unit" title="Central processing unit">CPU</a></th><td class="infobox-data">@ 500 kHz</td></tr><tr><th scope="row" class="infobox-label">Memory</th><td class="infobox-data">2K (2048) 35-bit words (i.e., 8<style data-mw-deduplicate="TemplateStyles:r1154941027">

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</style>3⁄4 <a href="Kilobyte" title="Kilobyte">kilobytes</a>) (ultrasonic <a href="Delay-line_memory" title="Delay-line memory">delay-line memory</a> based on tanks of <a href="Mercury_(element)" title="Mercury (element)">mercury</a>)</td></tr><tr><th scope="row" class="infobox-label"><a href="Removable_media" title="Removable media">Removable storage</a></th><td class="infobox-data"><a href="Punched_tape" title="Punched tape">paper tape</a> readers and punches, fast punched <a href="Punched_card_input/output" title="Punched card input/output">card readers</a> and punches, and a 100 line a minute tabulator</td></tr><tr><th scope="row" class="infobox-label">Predecessor</th><td class="infobox-data"><a href="EDSAC" title="EDSAC">EDSAC</a></td></tr><tr><th scope="row" class="infobox-label">Successor</th><td class="infobox-data">LEO II</td></tr></tbody></table>

The LEO (Lyons Electronic Office) was a series of early <a href="Computer" title="Computer">computer</a> systems created by <a href="J._Lyons_and_Co." title="J. Lyons and Co.">J. Lyons and Co.</a> The first in the series, the LEO I, was the first computer used for commercial business applications.

The prototype LEO I was modelled closely on the <a href="University_of_Cambridge" title="University of Cambridge">Cambridge</a> <a href="EDSAC" title="EDSAC">EDSAC</a>. Its construction was overseen by Oliver Standingford, Raymond Thompson and <a href="David_Caminer" title="David Caminer">David Caminer</a> of <a href="J._Lyons_and_Co." title="J. Lyons and Co.">J. Lyons and Co.</a> LEO I ran its first business application in 1951. In 1954 Lyons formed LEO Computers Ltd to market LEO I and its successors LEO II and LEO III to other companies. LEO Computers eventually became part of <a href="English_Electric_Company" class="mw-redirect" title="English Electric Company">English Electric Company</a> (EEL), (EELM), then English Electric Computers (EEC), where the same team developed the faster LEO 360 and even faster LEO 326 models. It then passed to <a href="International_Computers_Limited" title="International Computers Limited">International Computers Limited</a> (ICL) and ultimately <a href="Fujitsu" title="Fujitsu">Fujitsu</a>.

LEO series computers were still in use until 1981.

<div class="mw-heading mw-heading2"><h2 id="Origins_and_initial_design">Origins and initial design</h2></div>

<a href="J._Lyons_and_Co." title="J. Lyons and Co.">J. Lyons and Co.</a> was one of the UK's leading catering and food manufacturing companies in the first half of the 20th century. In 1947, two of its senior managers, Oliver Standingford and Raymond Thompson, were sent to the United States to look at new business methods developed during <a href="World_War_II" title="World War II">World War II</a>. During the visit, they met <a href="Herman_Goldstine" title="Herman Goldstine">Herman Goldstine</a> who was one of the original developers of <a href="ENIAC" title="ENIAC">ENIAC</a>, the first general-purpose electronic computer. Standingford and Thompson saw the potential of computers to help solve the problem of administering a major business enterprise. They also learned from Goldstine that, back in the UK, <a href="Douglas_Hartree" title="Douglas Hartree">Douglas Hartree</a> and <a href="Maurice_Wilkes" title="Maurice Wilkes">Maurice Wilkes</a> were actually building another such machine, the pioneering <a href="EDSAC" title="EDSAC">EDSAC</a> computer, at the <a href="University_of_Cambridge" title="University of Cambridge">University of Cambridge</a>.<a href="#cite_note-1">[1]</a>

On their return to the UK, Standingford and Thompson visited Hartree and Wilkes in Cambridge and were favourably impressed with their technical expertise and vision. Hartree and Wilkes estimated that EDSAC was 12–18 months from completion, but said that this interval could be shortened by additional funding. Standingford and Thompson wrote a report to the Lyons' board recommending that Lyons should acquire or build a computer to meet their business needs. The board agreed that, as a first step, Lyons would provide Hartree and Wilkes with £2,500 for the EDSAC project, and would also provide them with the services of a Lyons electrical engineer, Ernest Lenaerts. EDSAC was completed and ran its first program in May 1949.<a href="#cite_note-2">[2]</a>

Following the successful completion of EDSAC, the Lyons board agreed to start the construction of their own machine, expanding on the EDSAC design. The LEO computer room, which took up around 2,500 square feet of floor space, was at <a href="Cadby_Hall" title="Cadby Hall">Cadby Hall</a> in Hammersmith.<a href="#cite_note-:1-3">[3]</a>

The Lyons machine was christened Lyons Electronic Office, or LEO. On the recommendation of Wilkes, Lyons recruited <a href="John_Pinkerton_(computer_designer)" title="John Pinkerton (computer designer)">John Pinkerton</a>, a radar engineer and research student at Cambridge, as team leader for the project. Lenaerts returned to Lyons to work on the project, and Wilkes provided training for Lyons' engineer Derek Hemy, who would be responsible for writing LEO's programs. On 15 February 1951 the computer, carrying out a simple test program, was shown to <a href="Royal_Highness" title="Royal Highness">HRH</a> <a href="Elizabeth_II" title="Elizabeth II">Princess Elizabeth</a>.<a href="#cite_note-:0-4">[4]</a> The first business application to be run on LEO was Bakery Valuations, which computed the costs of ingredients used in bread and cakes.<a href="#cite_note-:2-5">[5]</a> This was successfully run on 5 September 1951,<a href="#cite_note-:0-4">[4]</a> and LEO took over Bakery Valuations calculations completely on 29–30 November 1951.<a href="#cite_note-6">[6]</a><a href="#cite_note-:0-4">[4]</a>

<a href="Mary_Coombs" title="Mary Coombs">Mary Coombs</a> was employed in 1952 as the first female programmer to work on LEO, and as such she is recognized as the first female commercial programmer.<a href="#cite_note-7">[7]</a><a href="#cite_note-computingheritage-8">[8]</a><a href="#cite_note-9">[9]</a><a href="#cite_note-10">[10]</a><a href="#cite_note-11">[11]</a>

Five files of archive material on the LEO Computer patent are held at the <a href="British_Library" title="British Library">British Library</a> and can be accessed through the British Library Archives catalogue.<a href="#cite_note-12">[12]</a>

<div class="mw-heading mw-heading2"><h2 id="Design">Design</h2></div>

LEO I's clock speed was 500 kHz, with most instructions taking about 1.5 ms to execute.<a href="#cite_note-13">[13]</a><a href="#cite_note-14">[14]</a><a href="#cite_note-15">[15]</a> To be useful for business applications, the computer had to be able to handle a number of data streams, input and output, simultaneously. Therefore, its chief designer, <a href="John_Pinkerton_(computer_designer)" title="John Pinkerton (computer designer)">John Pinkerton</a>, designed the machine to have multiple input/output <a href="Data_buffer" title="Data buffer">buffers</a>. In the first instance, these were linked to fast <a href="Punched_tape" title="Punched tape">paper tape</a> readers and punches, fast punched <a href="Punched_card_input/output" title="Punched card input/output">card readers</a> and punches, and a 100-line-per-minute tabulator. Later, other devices, including magnetic tape, were added. Its ultrasonic <a href="Delay-line_memory" title="Delay-line memory">delay-line memory</a> based on tanks of <a href="Mercury_(element)" title="Mercury (element)">mercury</a>, with 2K (2048) 35-bit words (i.e., 83⁄4 <a href="Kilobyte" title="Kilobyte">kilobytes</a>), was four times as large as that of EDSAC. The systems analysis was carried out by <a href="David_Caminer" title="David Caminer">David Caminer</a>.<a href="#cite_note-16">[16]</a>

<div class="mw-heading mw-heading2"><h2 id="Applications_and_successors">Applications and successors</h2></div>

Lyons used LEO I initially for valuation jobs, but its role was extended to include <a href="Payroll" title="Payroll">payroll</a>, <a href="Inventory" title="Inventory">inventory</a>, 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 was the first instance of an integrated management information system.<a href="#cite_note-17">[17]</a> The LEO project was also a pioneer in <a href="Outsourcing" title="Outsourcing">outsourcing</a>: 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. <a href="Met_Office" title="Met Office">Met Office</a> staff used a LEO I before the Met Office bought its own computer, a <a href="Ferranti_Mercury" title="Ferranti Mercury">Ferranti Mercury</a>, in 1959.<a href="#cite_note-18">[18]</a>

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; it was a <a href="Solid-state_electronics" title="Solid-state electronics">solid-state</a> machine with a 13.2 μs cycle time <a href="Ferrite_core_memory" class="mw-redirect" title="Ferrite core memory">ferrite core memory</a>.<a href="#cite_note-leo3s-19">[19]</a> It was <a href="Microcode" title="Microcode">microprogrammed</a> and was controlled by a <a href="Computer_multitasking" title="Computer multitasking">multitasking</a> "Master program" operating system, which allowed concurrent running of as many as 12 application programs.

Users of LEO computers programmed in two coding languages: Intercode,<a href="#cite_note-20">[20]</a> a low-level <a href="Assembly_language" title="Assembly language">assembler</a> type language; and CLEO (<a href="Acronym" title="Acronym">acronym</a>: Clear Language for Expressing Orders), the <a href="COBOL" title="COBOL">COBOL</a> equivalent.<a href="#cite_note-21">[21]</a>

One of the features that LEO III shared with many computers of the day was a loudspeaker connected to the central processor via a divide-by-100 circuit and an amplifier which enabled operators to tell whether a program was looping by the distinctive sound it made.<a href="#cite_note-22">[22]</a> Another quirk was that many intermittent faults were due to faulty connectors and could be temporarily fixed by briskly strumming the card handles.

Some LEO III machines purchased in the mid-to-late 1960s remained in commercial use at <a href="General_Post_Office" title="General Post Office">GPO</a> Telephones, the forerunner of <a href="BT_Group" title="BT Group">British Telecom</a>, until 1981, primarily producing telephone bills.<a href="#cite_note-:2-5">[5]</a><a href="#cite_note-leo3s-19">[19]</a> They were kept running using parts from redundant LEOs purchased by the GPO.

<div class="mw-heading mw-heading2"><h2 id="Fate_and_legacy">Fate and legacy</h2></div>

In 1963, LEO Computers Ltd was merged into <a href="English_Electric" title="English Electric">English Electric Company</a> and this led to the breaking up of the team that had inspired LEO computers. The 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.

English Electric LEO Computers (EEL) (1963), then English Electric Leo Marconi (EELM) (1964), later English Electric Computers (EEC) (1967), eventually merged with <a href="International_Computers_and_Tabulators" title="International Computers and Tabulators">International Computers and Tabulators</a> (ICT) and others to form <a href="International_Computers_Limited" title="International Computers Limited">International Computers Limited</a> (ICL) in 1968. In the 1980s, there were still <a href="ICL_2900" class="mw-redirect" title="ICL 2900">ICL 2900</a> mainframes running LEO programs, using an emulator written in ICL 2960 microcode at the <a href="Dalkeith" title="Dalkeith">Dalkeith</a> development centre.<a href="#cite_note-23">[23]</a> At least one modern emulator has been developed which can run some original LEO III software on a modern server.<a href="#cite_note-24">[24]</a> ICL was bought by <a href="Fujitsu" title="Fujitsu">Fujitsu</a> in 1990.

Whether its investment in LEO actually benefited J. Lyons is unclear. <a href="Nick_Pelling" title="Nick Pelling">Nick Pelling</a> notes that before LEO I the company already had a proven, industry-leading system using clerks that gave it "near-real-time management information on more or less all aspects of its business", and that no jobs were lost when the system was computerized. In addition, LEO Computers lost money on many of its sales because of unrealistically low prices.<a href="#cite_note-pelling2002-25">[25]</a>

In 2018, the <a href="Centre_for_Computing_History" title="Centre for Computing History">Centre for Computing History</a> along with LEO Computers Society were awarded funding from the <a href="Heritage_Lottery_Fund" class="mw-redirect" title="Heritage Lottery Fund">Heritage Lottery Fund</a> for their project aiming to bring together, preserve, archive and digitise a range of LEO Computers artefacts, and documents.<a href="#cite_note-computinghistory_50073-26">[26]</a> The Centre's museum gallery has an area dedicated to LEO, and as of 2021 they are also working on a LEO <a href="Virtual_reality" title="Virtual reality">virtual reality</a> project.<a href="#cite_note-computinghistory_55785-27">[27]</a><a href="#cite_note-:1-3">[3]</a> In November 2021, to coincide with the 70th anniversary of the first successful full program run on LEO I, the project released a film about the history of LEO, which went on to win Video of the Year in the Association of British Science Writers Awards in July 2022.<a href="#cite_note-28">[28]</a><a href="#cite_note-29">[29]</a>

<ul><li><a href="List_of_vacuum-tube_computers" title="List of vacuum-tube computers">List of vacuum-tube computers</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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<li id="cite_note-1"><a href="#cite_ref-1">^</a> Ferry (2003), Chapter 2

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<li id="cite_note-2"><a href="#cite_ref-2">^</a> Ferry (2003), Chapter 3

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<li id="cite_note-:0-4">^ <a href="#cite_ref-:0_4-0">a</a> <a href="#cite_ref-:0_4-1">b</a> <a href="#cite_ref-:0_4-2">c</a> <cite id="CITEREFBird1994" class="citation book cs1">Bird, Peter John (1994). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=O4VPAAAAMAAJ">LEO: The First Business Computer</a>. Hasler. pp. 84, 86, 228. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9780952165101</bdi>.</cite>

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<li id="cite_note-6"><a href="#cite_ref-6">^</a> Ferry (2003), Chapter 4

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<li id="cite_note-10"><a href="#cite_ref-10">^</a> <cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://artsandculture.google.com/exhibit/ARmIoOoP">"Women in Computing: a British Perspective – Google Arts & Culture"</a>. Google Cultural Institute. Retrieved 26 July 2018.</cite>

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</li>

<li id="cite_note-23"><a href="#cite_ref-23">^</a> <cite id="CITEREFMorgan2012" class="citation cs2">Morgan, Tony (2012), <a rel="nofollow" class="external text" href="http://www.leo-computers.org.uk/images/Leo%20III%20DME%20Story.pdf">THE DME LEO DME STORY</a> (PDF)</cite>

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</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2></div>

<ul><li><a href="Peter_Bird_(IT_manager)" title="Peter Bird (IT manager)">Bird, P. J.</a> (1994). LEO: The First Business Computer. Wokingham: Hasler Publishing Co. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-9521651-0-4</bdi>.</li>

<li><cite id="CITEREFCaminerArisHermonLand1998" class="citation book cs1">Caminer, D. T.; Aris, J. B.; Hermon, P. M.; <a href="Frank_Land" title="Frank Land">Land, F. F.</a> (1998). LEO: the incredible story of the world's first business computer. <a href="McGraw-Hill" class="mw-redirect" title="McGraw-Hill">McGraw-Hill</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-07-009501-9</bdi>.</cite></li>

<li>Campbell-Kelly, M., (1989). ICL: A Business and Technical History. Oxford: <a href="Clarendon_Press" class="mw-redirect" title="Clarendon Press">Clarendon Press</a>.</li>

<li>Caminer, D. T., Aris, J. B. B., Hermon, P. M. R., Land, F. F. (1996). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20051123125148/http://www.jpbowen.com/publications/thes-leo.html">User-Driven Innovation: The World’s First Business Computer</a>. London: <a href="McGraw-Hill" class="mw-redirect" title="McGraw-Hill">McGraw-Hill</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-07-009501-9</bdi>.</li>

<li>Carmichael, H., editor (1996). An ICL Anthology, Chapter 6: LEO, Laidlaw Hicks, Surbiton, UK.</li>

<li><cite id="CITEREFFerry2003" class="citation cs2">Ferry, Georgina (2003), A Computer Called LEO: Lyons Tea Shops and the World's First Office Computer, London: Fourth Estate, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>1-84115-185-8</bdi></cite></li>

<li>Hally, M. (2005). Electronic Brains: stories from the dawn of the computer age. Washington:Joseph Henry Press. Chapter 5: LEO the Lyons Computer. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-309-09630-8</bdi>.</li>

<li>Land, F. F., (1997). LEO, the First Business Computer: A Personal Experience. In <a href="Robert_L._Glass" title="Robert L. Glass">Glass, R. L.</a>, editor. In the Beginning: Recollections of Software Pioneers, pages 134–153. <a href="IEEE_Computer_Society" title="IEEE Computer Society">IEEE Computer Society</a>, Los Alamitos, CA.</li>

<li>PEP, (1957). Three Case Studies in Automation, PEP, London.</li>

<li>Simmons, J. R. M., (1962). LEO and the Managers, MacDonald, London.</li>

<li>Aris, J. B. B. (1996). "Systems Design – Then and Now". Resurrection, Summer issue 1996.</li>

<li>Land, F. F. (1996). "Systems Analysis for Business Applications". Resurrection, Summer issue 1996.</li>

<li>Aris, J. B. B. (2000). "Inventing Systems Engineering". <a href="IEEE_Annals_of_the_History_of_Computing" title="IEEE Annals of the History of Computing">IEEE Annals of the History of Computing</a>, Vol. 22, No. 3, July–September, pp. 4–15</li>

<li>Land, F. F. (2000). "The First Business Computer: A Case Study in User-Driven Automation". IEEE Annals of the History of Computing, Vol. 22, No. 3, July–September, pp. 16–26.</li>

<li>Caminer, D. T. (1958), "...And How to Avoid Them". <a href="The_Computer_Journal" title="The Computer Journal">The Computer Journal</a>, Vol. 1, No. 1.</li>

<li>Caminer, D. T. (1997). "LEO and its Applications: The Beginning of Business Computing". The Computer Journal, Vol. 40, No. 10.</li>

<li>Caminer, D. T. (2003). "Behind the Curtain at LEO: A Personal Reminiscence". IEEE Annals of the History of Computing, Vol. 25, No. 2, April–June, pp3–13.</li>

<li>Hendry, J. (1988). "The Teashop Computer Manufacturer: J. Lyons". Business History, Vol. 29, No. 8, pp. 73–102.</li>

<li>Land, Frank (1999). "A Historical Analysis of Implementing IS at J. Lyons." In Currie, W. G.; Galliers, R. D., editors. Rethinking Management Information Systems, pp. 310–325. <a href="Oxford_University_Press" title="Oxford University Press">Oxford University Press</a>.</li>

<li><cite id="CITEREFSavard2018" class="citation web cs1">Savard, John J. G. (2018) [2005]. <a rel="nofollow" class="external text" href="http://www.quadibloc.com/comp/cp02.htm">"Computer Arithmetic"</a>. quadibloc. The Early Days of Hexadecimal. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180716102439/http://www.quadibloc.com/comp/cp02.htm">Archived</a> from the original on 16 July 2018. Retrieved 16 July 2018.</cite> (Has information on the LEO III character set.)</li></ul>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://www.leo-computers.org.uk/">LEO Computers Society</a>. Includes <a rel="nofollow" class="external text" href="http://www.computinghistory.org.uk/pages/52267/LEOPEDIA/">LEOPEDIA</a> which is intended to be a comprehensive reference to archive, museum and media holdings and references to LEO computers, and individuals associated with them, updated periodically by <a href="Frank_Land" title="Frank Land">Frank Land</a>.</li>

<li><a rel="nofollow" class="external text" href="http://www.vintage-icl-computers.com/LEO-Computer-Tapes">LEO Magnetic Data Tape Collection at The ICL Computer Museum</a></li>

<li><a rel="nofollow" class="external text" href="http://www.vintage-icl-computers.com/icl3a">LEO Artefacts at The ICL Computer Museum</a></li>

<li><a rel="nofollow" class="external text" href="http://www.vintage-icl-computers.com/LEO-Paperwork">LEO Paperwork at The ICL Computer Museum</a></li>

<li><a rel="nofollow" class="external text" href="http://www.computinghistory.org.uk/sec/54762/LEO-Artefacts-Collection/">LEO Artefacts at the Centre for Computing History</a></li>

<li><a rel="nofollow" class="external text" href="https://archiveshub.jisc.ac.uk/manchesteruniversity/data/gb133-nahc/leo">LEO Computers Collection</a>, National Archive for the History of Computing, <a href="University_of_Manchester_Library" title="University of Manchester Library">University of Manchester Library</a>.</li>

<li><a rel="nofollow" class="external text" href="https://www.bbc.com/news/av/stories-50559357/how-a-cake-company-pioneered-the-first-office-computer">How a cake company pioneered the first office computer</a> BBC video interview with <a href="Mary_Coombs" title="Mary Coombs">Mary Coombs</a>, who worked on the first LEO computer and was the first woman to become a commercial computer programmer</li>

<li><a rel="nofollow" class="external text" href="http://purl.umn.edu/107600">Oral history interview with John M. M. Pinkerton</a>, <a href="Charles_Babbage_Institute" class="mw-redirect" title="Charles Babbage Institute">Charles Babbage Institute</a>, University of Minnesota. Pinkerton describes his work on LEO computers. In this context he discusses the British computer firms <a href="J._Lyons_and_Company" class="mw-redirect" title="J. Lyons and Company">J. Lyons and Company</a>, <a href="English_Electric" title="English Electric">English Electric</a>, and <a href="International_Computers_Ltd." class="mw-redirect" title="International Computers Ltd.">International Computers Ltd.</a></li>

<li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120210022739/http://is2.lse.ac.uk/leo/">About LEO</a> – From Business Computing: the Second 50 Years, The Guildhall conference for business leaders, London, 2001. Archived in February 2012.</li>

<li><a rel="nofollow" class="external text" href="http://www.kzwp.com/lyons/leo.htm">J. Lyons & Co. LEO Computers</a>. Extract from Peter Bird's LEO – The First Business Computer (2002); at David Lawrence's Lyons website</li>

<li><a rel="nofollow" class="external text" href="https://www.bbc.co.uk/radio4/science/electronicbrains.shtml">BBC Science: Electronic Brains</a> BBC Radio 4 series about early computers, 2002; programme 1 is about LEO</li>

<li><a rel="nofollow" class="external text" href="https://www.bbc.co.uk/programmes/b04m3ftg">Hidden Histories of the Information Age</a> BBC Radio 4 series, 2016; programme about LEO</li>

<li><a rel="nofollow" class="external text" href="https://warwick.ac.uk/services/library/mrc/archives_online/digital/leo/digitised">"Developing LEO: The world's first business computer", documents from the papers of John Simmons, Modern Records Centre, University of Warwick</a></li>

<li><cite id="CITEREFPinkerton1961" class="citation journal cs1">Pinkerton, J. M. M. (1 January 1961). <a rel="nofollow" class="external text" href="https://doi.org/10.1093%2Fcomjnl%2F4.1.42">"The Evolution of Design in a series of Computers, LEO I-III"</a>. <a href="The_Computer_Journal" title="The Computer Journal">The Computer Journal</a>. 4 (1): 42–46. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1093%2Fcomjnl%2F4.1.42">10.1093/comjnl/4.1.42</a>. <a href="ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0010-4620">0010-4620</a>.</cite></li>

<li><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://www.telegraph.co.uk/news/obituaries/2188963/David-Caminer.html">"David Caminer obituary"</a>. <a href="Daily_Telegraph" class="mw-redirect" title="Daily Telegraph">Daily Telegraph</a>. 24 June 2008.</cite></li>

<li><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=Rzu68nRVwtE">"LEO: the story of the world's first business computer"</a>. <a href="YouTube" title="YouTube">YouTube</a>. <a href="The_Centre_for_Computing_History" class="mw-redirect" title="The Centre for Computing History">The Centre for Computing History</a>. 30 November 2021.</cite></li></ul>

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</style><div id="International_Computers_Limited_(ICL)_1968-2002795" style="font-size:114%;margin:0 4em"><a href="International_Computers_Limited" title="International Computers Limited">International Computers Limited</a> (ICL) 1968-2002</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Predecessor <a href="Mainframe_computer" title="Mainframe computer">mainframes</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul>

<li><a href="Elliott_803" title="Elliott 803">Elliott 803</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="English_Electric_System_4" title="English Electric System 4">English Electric System 4 series</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="English_Electric_System_4" title="English Electric System 4">System 4/10</a></li>

<li><a href="English_Electric_System_4" title="English Electric System 4">System 4/30</a></li>

<li><a href="English_Electric_System_4" title="English Electric System 4">System 4/50</a></li>

<li><a href="English_Electric_System_4" title="English Electric System 4">System 4/70</a></li>

<li><a href="English_Electric_System_4" title="English Electric System 4">System 4/72</a></li>

<li><a href="English_Electric_System_4" title="English Electric System 4">System 4/75</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="ICT_1900_series" title="ICT 1900 series">ICT 1900 series</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="ICL_2900_Series" title="ICL 2900 Series">ICL 2900 Series</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="ICL_Series_39" title="ICL Series 39">ICL Series 39</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="ICL_Series_39" title="ICL Series 39">Level 30</a></li>

<li><a href="ICL_Series_39" title="ICL Series 39">Level 50</a></li>

<li><a href="ICL_Series_39" title="ICL Series 39">Level 60</a></li>

<li><a href="ICL_Series_39" title="ICL Series 39">Level 80</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Minicomputer" title="Minicomputer">Minicomputers</a> category</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="System_Ten" class="mw-redirect" title="System Ten">System Ten</a></li>

<li><a href="System_25" class="mw-redirect" title="System 25">System 25</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Workstation" title="Workstation">Workstations</a> category</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Operating_system" title="Operating system">Operating systems</a> category</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="ICL_VME" title="ICL VME">OpenVME</a></li>

<li><a href="SuperNova_(operating_system)" class="mw-redirect" title="SuperNova (operating system)">superNova</a></li>

<li><a href="Executive_(operating_system)" class="mw-redirect" title="Executive (operating system)">Executive</a></li>

<li><a href="GEORGE_(operating_system)" title="GEORGE (operating system)">GEORGE</a></li>

<li><a href="MAXIMOP" class="mw-redirect" title="MAXIMOP">MAXIMOP</a></li>

<li><a href="MINIMOP" title="MINIMOP">MINIMOP</a></li>

<li><a href="MultiJob" class="mw-redirect" title="MultiJob">MultiJob</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Programming_language" title="Programming language">Programming languages</a> category</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Fortran" title="Fortran">Fortran</a></li>

<li><a href="ALGOL" title="ALGOL">ALGOL</a> 60</li>

<li><a href="COBOL" title="COBOL">COBOL</a></li>

<li><a href="Pascal_(programming_language)" title="Pascal (programming language)">Pascal</a></li>

<li><a href="ICL_VME#Quickbuild" title="ICL VME">ApplicationMaster</a></li>

<li><a href="ReportMaster" class="mw-redirect" title="ReportMaster">ReportMaster</a></li>

<li><a href="DAP_FORTRAN" title="DAP FORTRAN">DAP FORTRAN</a></li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

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