Harwell computer

The computer, which weighs {{Convert|2.5|MT|ST}},{{Cite news|url=http://www.tnmoc.org/news/news-releases/worlds-oldest-original-working-digital-computer|title=The world's oldest original working digital computer|date=20 November 2012|work=The National Museum of Computing|access-date=20 May 2018}}{{cite news| url=http://www.cnn.com/2012/11/21/tech/innovation/witch-computer-restoration/index.html?iref=allsearch | title=61-year-old computer springs back to life | publisher=CNN | date=21 November 2012 }} was built and used at the Atomic Energy Research Establishment in Harwell, Berkshire.{{cite web | title = Computing at Harwell | url = http://www.chilton-computing.org.uk/acl/literature/reports/p009.htm | format = report | location = UK | publisher = Chilton computing | accessdate = 7 December 2008}} Construction started in 1949, and the machine became operational in April 1951.{{Cite web|url=http://www.chilton-computing.org.uk/acl/literature/earlyhistory/p014.htm|title=Harwell Computers: Hollerith 555 and Dekatron|website=chilton-computing.org.uk|at=1. Introduction, 2. Harwell Dekatron; The Harwell Computer by E.H. Cooke-Yarborough}} It was handed over to the computing group in May 1952{{cite book|url=https://archive.org/details/bitsavers_onrASurveyomputers1953_8778395|title=A survey of automatic digital computers|last1=Research|first1=United States Office of Naval|date=1953|publisher=Office of Naval Research, Dept. of the Navy|page=[https://archive.org/details/bitsavers_onrASurveyomputers1953_8778395/page/n49 44]|language=en}} and remained in use until 1957.

It used 828 dekatrons for volatile memory,{{Cite web |last=Garrad |first=Jacqui |date=2012-11-30 |title=The world's oldest original working digital computer |url=https://www.tnmoc.org/news-releases/2012/11/30/the-worlds-oldest-original-working-digital-computer |access-date=2023-07-22 |website=The National Museum of Computing |language=en-GB}} similar to RAM in a modern computer, and paper tape for input and program storage.{{cite web | work = The Museum | title = Atomic Energy Authority (UK) | publisher = Old computers | url = http://www.old-computers.com/MUSEUM/computer.asp?st=1&c=1235 | accessdate = 25 November 2008 | archive-url = https://web.archive.org/web/20101121031904/http://www.old-computers.com/museum/computer.asp?st=1&c=1235 | archive-date = 21 November 2010 | url-status = dead }} A total of 480 relays were used for sequence control{{Cite web|url=http://www.computerconservationsociety.org/witch5.htm|title=An Electronic Digital Computor Using Cold Cathode Counting Tubes for Storage|website=computerconservationsociety.org|at=Sequence Control|access-date=20 May 2018}} and 199 valves (electronic vacuum tube) for calculations.{{Cite news|url=http://www.tnmoc.org/explore/large-systems|title=First generation – WITCH & EDSAC|work=The National Museum of Computing|access-date=20 May 2018|archive-url=https://web.archive.org/web/20190426181118/http://www.tnmoc.org/explore/large-systems|archive-date=26 April 2019|url-status=dead}}{{Cite web|url=http://www.computerconservationsociety.org/witch-layout.htm|title=Layout of the WITCH Computer|website=computerconservationsociety.org|access-date=20 May 2018}} The computer stands 2 meters high, 6 meters wide, and 1 meter deep with a power consumption of 1.5 kW. Output was to either a Creed teleprinter or to a paper tape punch.{{cite web |title=The Harwell Computer, better known as The 'WITCH' Computer |publisher=Computer Conservation Society | url = http://www.computerconservationsociety.org/witch.htm | date=August 2008 | first =Kevin | last = Murrell |accessdate = 25 November 2008}} The machine was decimal and initially had twenty eight-digit dekatron registers for internal storage, which was increased to 40 which appeared to be enough for nearly all calculations. It was assembled from components more commonly found in a British telephone exchange.{{cite web |title = History of SCIT Computers |publisher = University of Wolverhampton School of Computing and Information Technology |url = http://www.scit.wlv.ac.uk/university/scit/history/witch.html |archive-url = https://web.archive.org/web/19980131090055/http://www.scit.wlv.ac.uk/university/scit/history/witch.html |url-status = dead |archive-date = 31 January 1998 |accessdate = 25 November 2008 }} The man who led the effort to rebuild the machine (see below) put it in perspective to the BBC: "All together, the machine can store 90 numbers. The closest analogy is a man with a pocket calculator," Delwyn Holroyd, who led the restoration effort, tells the BBC in a video about the restoration. Although it could on occasions act as a true stored-program computer, that was not its normal mode of operation. It had a multiplication time of between 5 and 10 seconds, very slow for an electronic computer.{{cite book |last = Lavington |first= Simon |title= Early British Computers |publisher= Manchester University Press |year= 1980 |page= 139 | url = http://ed-thelen.org/comp-hist/EarlyBritish-05-12.html#Ch-09 |isbn= 0-7190-0803-4}}

As Ted Cooke-Yarborough wrote of his design in 1953 "a slow computer can only justify its existence if it is capable of running for long periods unattended and the time spent performing useful computations is a large proportion of the total time available". The design was noted for its reliability because in the period from May 1952 until February 1953 it averaged 80 hours per week running time. Dr Jack Howlett, Director of the Computer Laboratory at AERE 1948–61, said it "could be left unattended for long periods; I think the record was over one Christmas-New Year holiday when it was all by itself, with miles of input data on punched tape to keep it happy, for at least ten days and was still ticking away when we came back." It was the machine's untiring durability, rather than its speed, that was its main feature. Human mathematicians (a job role called a "hand-computer") could make calculations at a similar speed, but not continuously for the same lengths of time. Dr Howlett commented:

{{quote |One day EB ‘Bart’ Fossey, an excellent hand-computer (still with what used to be called the Atlas Computer Laboratory), settled down beside the machine with his desk machine and attempted a race. He kept level for about half an hour working flat out, but had to retire, exhausted; the machine just ploughed on.}}

File:Harwell-dekatron-witch-computer-under-resotoration-2010-03-13.jpg

In 1957, at the end of its life at Harwell, the Oxford Mathematical Institute ran a competition to award it to the college that could produce the best case for its future use. The competition was the idea of John Hammersley, who had worked at AERE previously. The competition was won by the Wolverhampton and Staffordshire Technical College (which later became Wolverhampton University) where it was used to teach computing until 1973. The computer was renamed as the WITCH, the Wolverhampton Instrument for Teaching Computing from Harwell.

The WITCH was donated to the Museum of Science and Industry, Birmingham in 1973. After the museum closed in 1997, the computer was disassembled and stored at the Birmingham Museum Collection Centre.{{Citation | title = Birmingham | place = UK | url = http://www.birmingham.gov.uk/cs/Satellite?c=Page&childpagename=SystemAdmin%2FCFPageLayout&cid=1223092602598&packedargs=subtype%3DEventWithIconTemplate%26website%3D4&pagename=BCC%2FCommon%2FWrapper%2FCFWrapper&rendermode=live| archive-url = https://web.archive.org/web/20110629133300/http://www.birmingham.gov.uk/cs/Satellite?c=Page&childpagename=SystemAdmin%2FCFPageLayout&cid=1223092602598&packedargs=subtype=EventWithIconTemplate&website=4&pagename=BCC%2FCommon%2FWrapper%2FCFWrapper&rendermode=live| url-status = dead| archive-date = 29 June 2011}}.

File:Harwell Dekatron Computer front view.JPG

From September 2009, the machine was loaned to The National Museum of Computing in the site of Bletchley Park, where it began to be restored to working order as a Computer Conservation Society project.{{cite web |url=http://www.tnmoc.org/36/section.aspx/101 |archive-url=https://web.archive.org/web/20090908101139/http://tnmoc.org/36/section.aspx/101 |url-status=dead |archive-date=8 September 2009 |title=Challenge begins to exhibit the world's oldest, working computer |accessdate=3 September 2009 |last=Fleming |first=Stephen |date=3 September 2009 |publisher=The National Museum of Computing }}{{cite web | location = UK | url = http://news.bbc.co.uk/1/hi/technology/8234428.stm | title = Reboot for UK's 'oldest' computer | accessdate = 3 September 2009 | work = News | date = 3 September 2009 | publisher = BBC}} The museum, a registered charity, invited members of the public and industry to sponsor the restoration of the Harwell computer by purchasing one of 25 shares at £4,500 each. In 2012, the restoration was completed successfully.

A {{convert|9|x|7|ft|m}} painting of the machine, Portrait of a Dead WITCH was made by the artist John Yeadon in 1983. After being exhibited at the 1984 Leicestershire Schools and Colleges show and subsequently purchased by Newbridge High School, Coalville, Leicestershire.{{cite web |title=Painting by John Yeadon: "Portrait of a Dead WItch" - a Freedom of Information request to Leicestershire County Council |url=https://www.whatdotheyknow.com/request/painting_by_john_yeadon_portrait |website=WhatDoTheyKnow |access-date=28 September 2021 |language=en |date=1 September 2021}} Within two years of that school becoming a private academy school, the painting was sold at auction in 2015 to an undisclosed private buyer.{{cite web|url=http://www.morningstaronline.co.uk/a-e320-Privatising-public-art|title=Privatising public art|last=Yeadon|first=John|date=15 August 2015|work=Morning Star|accessdate=16 August 2015|archive-url=https://web.archive.org/web/20150818172554/http://www.morningstaronline.co.uk/a-e320-Privatising-public-art|archive-date=18 August 2015|url-status=dead}} It was discovered on the wall of the Jam Street Cafe Bar in Manchester. Kaldip Bhamber, who has a fine arts degree, was unaware of the painting provenance when she purchased it. John Yeadon has visited the painting at its new location.{{cite news| last1=Kennedy|first1=Maev | title=Portrait of world's oldest computer rediscovered in Manchester café | url=https://www.theguardian.com/technology/2016/mar/28/portrait-worlds-oldest-computer-witch-rediscovered-manchester-cafe-john-yeadon | accessdate=28 March 2016|work=The Guardian | publisher=Guardian Newspapers | date=28 March 2016 }}

• List of vacuum-tube computers
• Electromechanical computer

{{Reflist|colwidth=32em}}

• {{Commons category-inline|Harwell computer}}
• {{Citation | url = https://www.wired.com/gadgetlab/2009/09/britan-oldest-computer | magazine = Wired | title = Britain's Oldest Working Computer Roars to Life |date=September 2009}}.
• {{Citation | work = BBC News | place = UK | url = http://news.bbc.co.uk/1/hi/technology/8236968.stm | title = UK's 'oldest' computer rebuilt| date = 3 September 2009 }}.
• {{Citation |work=BBC News | place = UK | url = https://www.bbc.co.uk/news/technology-20155028 | title = Witch at Bletchley: 'World's oldest working digital computer'}}.
• {{Citation | url = http://www.computerconservationsociety.org/witch.htm | publisher = Computer Conservation Society | title = Witch}}.
• {{Cite news|url=http://www.tnmoc.org/special-projects/harwell-dekatron-witch|title=Harwell Dekatron / WITCH|work=The National Museum of Computing|access-date=20 May 2018|archive-url=https://web.archive.org/web/20190426180254/http://www.tnmoc.org/special-projects/harwell-dekatron-witch|archive-date=26 April 2019|url-status=dead}}
• {{Citation | url = https://www.amazon.co.uk/gp/product/0956795625/ref=olp_product_details?ie=UTF8&me=&seller= | title = New Book: "The Harwell Dekatron Computer" | date = 7 February 2013 | publisher = The National Museum of Computing| isbn = 9780956795625 }}.
• [https://artsandculture.google.com/story/UgUxOTVXYqfUnw What is a Computer: Inside the WITCH, by TNMOC]
• {{Citation | url = https://www.youtube.com/watch?v=vVgc8ksstyg | title=Harwell Dekatron / WITCH Reboot tnmoc.org | via=YouTube | date=21 November 2012 }}

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Category:1951 establishments in England

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Category:Computer-related introductions in 1951

Category:1950s computers

Category:Early British computers

Category:One-of-a-kind computers

Category:Vacuum tube computers

Category:Electro-mechanical computers