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Many early computers, such as the [[Atanasoff–Berry computer]], were not reprogrammable. They executed a single hardwired program. As there were no program instructions, no program storage was necessary. Other computers, though programmable, stored their programs on [[punched tape]], which was physically fed into the system as needed.
In 1936, [[Konrad Zuse]] anticipated in two patent applications that machine instructions could be stored in the same storage used for data.<ref>{{citation |title=Electronic Digital Computers |journal=Nature |date=25 September 1948 |volume=162 |issue=4117 |page=487 |url=http://www.computer50.org/kgill/mark1/natletter.html |doi=10.1038/162487a0 |last1=Williams |first1=F. C |last2=Kilburn |first2=T |bibcode=1948Natur.162..487W |s2cid=4110351 |url-status=dead |archive-url=https://web.archive.org/web/20090406014626/http://www.computer50.org/kgill/mark1/natletter.html |archive-date=6 April 2009|doi-access=free }}</ref><ref>{{citation |title=Konrad Zuses Bemühungen um die Patentanmeldung der Z3 |language=de |author-first=Susanne |author-last=Faber |date=2000}}</ref>
The [[University of Manchester]]'s [[Manchester Baby|Baby]]<ref>{{Cite journal | last1 = Williams | first1 = Frederic | author-link1 = Frederic Calland Williams | last2 = Kilburn | first2 = Tom | author-link2 = Tom Kilburn | doi = 10.1038/162487a0 | title = Electronic Digital Computers | url = http://www.computer50.org/kgill/mark1/natletter.html | journal = Nature | volume = 162 | issue = 4117 | pages = 487 | year = 1948 | bibcode = 1948Natur.162..487W | s2cid = 4110351 | url-status = dead | archive-url = https://web.archive.org/web/20090406014626/http://www.computer50.org/kgill/mark1/natletter.html | archive-date = 6 April 2009| doi-access = free }}</ref> is generally recognized as world's first electronic computer that ran a stored program—an event that occurred on 21 June 1948.<ref name="RojasHashagen2002">{{cite book|author1=Rául Rojas|author2=Ulf Hashagen|title=The first computers: history and architectures|url=https://books.google.com/books?id=nDWPW9uwZPAC&pg=PA379|year=2002|publisher=MIT Press|isbn=978-0-262-68137-7|page=379}}</ref><ref name="Page2009c">{{cite book|author=Daniel Page|title=A Practical Introduction to Computer Architecture|year=2009|publisher=Springer|isbn=978-1-84882-255-9|page=158}}</ref> However the Baby was not regarded as a full-fledged computer, but more a [[proof of concept]] predecessor to the [[Manchester Mark 1]] computer, which was first put to research work in April 1949. On 6 May 1949 the [[EDSAC]] in Cambridge ran its first program, making it another electronic digital stored-program computer.<ref name="Hally2005">{{cite book|author=Mike Hally|title=Electronic brains: stories from the dawn of the computer age|url=https://books.google.com/books?id=DKcqJJacxxwC&pg=PA96|year=2005|publisher=National Academies Press|isbn=978-0-309-09630-0|page=96}}</ref> It is sometimes claimed that the [[IBM SSEC]], operational in January 1948, was the first stored-program computer;<ref name="Pugh1995">{{cite book|author=Emerson W. Pugh|title=Building IBM: shaping an industry and its technology|url=https://books.google.com/books?id=Bc8BGhSOawgC&pg=PA136|year=1995|publisher=MIT Press|isbn=978-0-262-16147-3|page=136}}</ref> this claim is controversial, not least because of the hierarchical memory system of the SSEC, and because some aspects of its operations, like access to relays or tape drives, were determined by plugging.<ref>{{Cite conference| last1 = Olley | first1 = A.| title = Existence Precedes Essence - Meaning of the Stored-Program Concept |conference = IFIP WG 9.7 International Conference, HC 2010 | book-title=History of Computing. Learning from the Past | volume = 325 | pages = 169–178 | year = 2010 | series = IFIP Advances in Information and Communication Technology | isbn = 978-3-642-15198-9 | url = http://individual.utoronto.ca/fofound/RevisedExistEss1.pdf|doi =10.1007/978-3-642-15199-6_17| doi-access = free }}</ref> The first stored-program computer to be built in continental Europe was the [[MESM]], completed in the [[Computer systems in the Soviet Union|Soviet Union]] in 1950.<ref>{{cite book |title=Science in Russia and the Soviet Union: A Short History |first=Loren R. |last=Graham |author-link=Loren R. Graham |publisher=Cambridge University Press |year=1993 |page=256 |isbn=9780521287890}}</ref>
=== The first stored-program computers ===
|publisher=MIT Press
|isbn=978-0-262-03398-5
|pages=153, 157, 164, 174, 194}}</ref><ref>{{Cite book |last=Haigh |first=Thomas |url=https://eniacinaction.com/wp-content/uploads/2014/02/EngineeringtheMiracleoftheENIAC-Published.pdf |title=Engineering “The"The Miracle of the ENIAC”ENIAC": Implementing the Modern Code Paradigm |year=2014 |language=en}}</ref> This claim is disputed by some computer historians.<ref>{{cite book | url=https://books.google.com/books?id=Gh8SEAAAQBAJ&dq=ENIAC+Stored+Program&pg=PA987 | title=Milestones in Analog and Digital Computing | isbn=9783030409746 | last1=Bruderer | first1=Herbert | date=4 January 2021 | publisher=Springer }}</ref>
* [[APEXC|ARC2]], a relay machine developed by [[Andrew Donald Booth|Andrew Booth]] and [[Kathleen Booth]] at [[Birkbeck, University of London]], officially came online on 12 May 1948.<ref name="birkbeck">{{cite journal|last1=Campbell-Kelly|first1=Martin|title=The Development of Computer Programming in Britain (1945 to 1955)|journal=IEEE Annals of the History of Computing|date=April 1982|volume=4|issue=2|pages=121–139|doi=10.1109/MAHC.1982.10016|s2cid=14861159}}</ref> It featured the first [[drum memory|rotating drum storage device]].<ref>{{cite book|editor1-last=Lavington|editor1-first=Simon|title=Alan Turing and his Contemporaries: Building the World's First Computers|date=2012|publisher=British Computer Society|___location=London|isbn=9781906124908|page=61}}</ref><ref>{{cite web|last1=Johnson|first1=Roger|title=School of Computer Science & Information Systems: A Short History|url=http://www.dcs.bbk.ac.uk/site/assets/files/1029/50yearsofcomputing.pdf|website=Birkbeck College|publisher=University of London|access-date=23 July 2017|date=April 2008}}</ref>
* [[Manchester Baby]], a developmental, fully electronic computer that successfully ran a stored program on 21 June 1948. It was subsequently developed into the [[Manchester Mark 1]], which ran its first program in early April 1949.
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