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{{short description|Computer that stores program instructions in electronically or optically accessible memory}}
{{Use dmy dates|date=February 2023}}
A '''stored-program computer''' is a [[computer]] that stores [[Instruction (computer science)|program instructions]] in electronically, electromagnetically, or optically accessible memory.<ref>{{Citation | last = Allison | first = Joanne | title = Stored-program Computers | year = 1997 | url = http://www.computer50.org/mark1/stored.html | access-date = 24 August 2011 | url-status = dead | archive-url = https://web.archive.org/web/20110927012816/http://www.computer50.org/mark1/stored.html | archive-date = 27 September 2011}}</ref> This contrasts with systems that stored the program instructions with [[plugboard]]s or similar mechanisms.
The definition is often extended with the requirement that the treatment of programs and data in memory be interchangeable or uniform.<ref name="GilreathLaplante2003">{{cite book|author1=William F. Gilreath|author2=Phillip A. Laplante|title=Computer Architecture: A Minimalist Perspective|url=https://books.google.com/books?id=9DuC35atMu0C&pg=RA1-PA24|year=2003|publisher=Springer|isbn=978-1-4020-7416-5|page=24}}</ref><ref name="Reilly2003">{{cite book|author=Edwin D. Reilly|title=Milestones in computer science and information technology|url=https://archive.org/details/milestonesincomp0000reil|url-access=registration|year=2003|publisher=Greenwood Publishing Group|isbn=978-1-57356-521-9|page=[https://archive.org/details/milestonesincomp0000reil/page/245 245]}}</ref><ref name="POCA">{{cite book|first=Miles J.|last=Murdocca|author2=Vincent P. Heuring |year=2000|title=Principles of Computer Architecture|publisher=Prentice-Hall|isbn=0-201-43664-7|pages=5}}</ref>
== Description ==
In principle, stored-program computers have been designed with various architectural characteristics. A computer with a [[von Neumann architecture]] stores program data and instruction data in the same memory, while a computer with a [[Harvard architecture]] has separate memories for storing program and data.<ref name="Page2009">{{cite book|author=Daniel Page|title=A Practical Introduction to Computer Architecture|year=2009|publisher=Springer|isbn=978-1-84882-255-9|page=148}}</ref><ref name="Balch2003">{{cite book|author=Mark Balch|title=Complete digital design: a comprehensive guide to digital electronics and computer system architecture|url=https://books.google.com/books?id=uFSRT-OIxyoC&pg=PA149|access-date=18 May 2011|year=2003|publisher=McGraw-Hill Professional|isbn=978-0-07-140927-8|page=149}}</ref> However, the term ''stored-program computer'' is sometimes used as a synonym for the von Neumann architecture.<ref name="Page2009b">{{cite book|author=Daniel Page|title=A Practical Introduction to Computer Architecture|year=2009|publisher=Springer|isbn=978-1-84882-255-9|page=153|url=https://books.google.com/books?id=X1m1tNcfWQYC&pg=PA153}}</ref><ref name="Grattan-Guinness2003">{{cite book|author=Ivor Grattan-Guinness|author-link=Ivor Grattan-Guinness|title=Companion encyclopedia of the history and philosophy of the mathematical sciences|url=https://books.google.com/books?id=2hDvzITtfdAC&pg=PA705|year=2003|publisher=JHU Press|isbn=978-0-8018-7396-6|page=705}}</ref> [[Jack Copeland]] considers that it is "historically inappropriate, to refer to electronic stored-program digital computers as 'von Neumann machines{{'"}}.<ref>{{Cite web | last = Copeland | first = Jack | author-link = Jack Copeland | title = A Brief History of Computing |at = ENIAC and EDVAC | year = 2000 | url = https://plato.stanford.edu/entries/computing-history/#ENIAC | access-date = 27 January 2010 }}</ref> Hennessy and Patterson wrote that the early Harvard machines were regarded as "reactionary by the advocates of stored-program computers".<ref name="HennessyPatterson2003">{{cite book|author1=John L. Hennessy|author-link=John L. Hennessy|author2=David A. Patterson|author2-link=David Patterson (scientist)|author3=David Goldberg|title=Computer architecture: a quantitative approach|url=https://archive.org/details/computerarchitec0003henn|url-access=registration|year=2003|publisher=Morgan Kaufmann|isbn=978-1-55860-724-8|page=[https://archive.org/details/computerarchitec0003henn/page/68 68]}}</ref>
== History ==
The concept of the stored-program computer can be traced back to the 1936 theoretical concept of a [[universal Turing machine]].<ref name="Copeland2006">{{cite book|author=B. Jack Copeland|author-link=B. Jack Copeland|title=Colossus: the secrets of Bletchley Park's codebreaking computers|url=https://books.google.com/books?id=gfL4ky-TQOMC&pg=PA104|year=2006|publisher=Oxford University Press|isbn=978-0-19-284055-4|page=104}}</ref> Von Neumann was aware of this paper, and he impressed it on his collaborators.<ref name="Teuscher2004">{{cite book|author=Christof Teuscher|title=Alan Turing: life and legacy of a great thinker|url=https://books.google.com/books?id=0IIsoRqw9hgC&pg=PA321|year=2004|publisher=Springer|isbn=978-3-540-20020-8|page=321–322}}</ref>
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, as was the case for the [[Zuse Z3]] and the [[Harvard Mark I]], or were only programmable by physical manipulation of switches and plugs, as was the case for the [[Colossus computer]].
In 1936, [[Konrad Zuse]] anticipated in two patent applications that machine instructions could be stored in the same storage used for data.
In 1948, the [[Manchester Baby]], built at [[University of Manchester]],<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 | journal = Nature | volume = 162 | issue = 4117 | pages = 487 | year = 1948 | bibcode = 1948Natur.162..487W | s2cid = 4110351 | doi-access = free }}</ref> is generally recognized as world's first electronic computer that ran a stored program—an event 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>
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