View source for History of computing hardware

{{Short description|Developments from devices for simple calculations to complex analog and digital computers}}
{{Use dmy dates|cs1-dates=ly|date=March 2021}}
{{History of computing}}
The '''history of computing hardware''' spans the developments from early devices used for simple calculations to today's complex computers, encompassing advancements in both analog and digital technology.

The first aids to computation were purely mechanical devices which required the operator to set up the initial values of an elementary [[arithmetic]] operation, then manipulate the device to obtain the result. In later stages, computing devices began representing numbers in continuous forms, such as by distance along a scale, rotation of a shaft, or a specific voltage level. Numbers could also be represented in the form of digits, automatically manipulated by a mechanism. Although this approach generally required more complex mechanisms, it greatly increased the precision of results. The development of transistor technology, followed by the invention of integrated circuit chips, led to revolutionary breakthroughs. 

Transistor-based computers and, later, integrated circuit-based computers enabled digital systems to gradually replace analog systems, increasing both efficiency and processing power. [[MOSFET|Metal-oxide-semiconductor]] (MOS) [[large-scale integration]] (LSI) then enabled [[semiconductor memory]] and the [[microprocessor]], leading to another key breakthrough, the miniaturized [[personal computer]] (PC), in the 1970s. The cost of computers gradually became so low that personal computers by the 1990s, and then [[mobile computing|mobile computers]] ([[smartphone]]s and [[tablet computer|tablets]]) in the 2000s, became ubiquitous.

==Early devices==
{{See also|Timeline of computing hardware before 1950}}

===Ancient and medieval===
[[File:Os d'Ishango IRSNB.JPG|thumb|upright=0.6|left|The [[Ishango bone]] is thought to be a Paleolithic tally stick.{{efn|The [[Ishango bone]] is a [[bone tool]], dated to the [[Upper Paleolithic]] era, about 18,000 to 20,000&nbsp;BC. It is a dark brown length of bone, the [[fibula]] of a baboon. It has a series of tally marks carved in three columns running the length of the tool. It was found in 1960 in Belgian Congo.<ref>{{cite web |first=Phill |last=Schultz |date=7 September 1999 |publisher=University of Western Australia School of Mathematics |url=https://www.maths.uwa.edu.au/~schultz/3M3/history.html |title=A very brief history of pure mathematics: The Ishango Bone |archive-url=https://web.archive.org/web/20080721075947/http://www.maths.uwa.edu.au/~schultz/3M3/history.html |archive-date=2008-07-21}}</ref>}} ]]
[[File:Abacus 6.png|thumb|right|[[Suanpan]] (The number represented on this abacus is 6,302,715,408.)]]
Devices have been used to aid computation for thousands of years, mostly using [[one-to-one correspondence]] with [[finger-counting|fingers]]. The earliest counting device was probably a form of [[tally stick]]. The [[Lebombo bone]] from the mountains between [[Eswatini]] and [[South Africa]] may be the oldest known mathematical artifact.<ref name="Selin2008">{{cite book |first=Helaine|last=Selin|title=Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures |url=https://books.google.com/books?id=kt9DIY1g9HYC&pg=PA1356|date=12 March 2008 |publisher=Springer Science & Business Media |isbn=978-1-4020-4559-2|page=1356|bibcode=2008ehst.book.....S|access-date=2020-05-27}}</ref> It dates from 35,000 BCE and consists of 29 distinct notches that were deliberately cut into a [[baboon]]'s [[fibula]].<ref>{{mathworld |title=Lebombo Bone |urlname=LebomboBone |author=Pegg, Ed Jr. |author-link=Ed Pegg Jr. |ref=none}}</ref><ref>{{cite book| last=Darling| first=David| title=The Universal Book of Mathematics From Abracadabra to Zeno's Paradoxes| year=2004| publisher=John Wiley & Sons| isbn= 978-0-471-27047-8}}</ref> Later record keeping aids throughout the [[Fertile Crescent]] included calculi (clay spheres, cones, etc.) which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers.{{efn|According to {{harvnb|Schmandt-Besserat|1981}}, these clay containers contained tokens, the total of which were the count of objects being transferred. The containers thus served as something of a [[bill of lading]] or an accounts book. In order to avoid breaking open the containers, first, clay impressions of the tokens were placed on the outside of the containers, for the count; the shapes of the impressions were abstracted into stylized marks; finally, the abstract marks were systematically used as numerals; these numerals were finally formalized as numbers. Eventually (Schmandt-Besserat estimates it took 5000 years.<ref>{{cite web |last=Schmandt-Besserat |first=Denise |title=The Evolution of Writing |url=https://sites.utexas.edu/dsb/files/2014/01/evolution_writing.pdf |archive-url=https://web.archive.org/web/20120130084757/http://www.laits.utexas.edu/ghazal/Chap1/dsb/chapter1.html |archive-date=2012-01-30 |url-status=live}}</ref>) the marks on the outside of the containers were all that were needed to convey the count, and the clay containers evolved into clay tablets with marks for the count.}}<ref>{{cite book |first=Eleanor |last=Robson |author-link=Eleanor Robson |year=2008 |title=Mathematics in Ancient Iraq |publisher=Princeton University Press |isbn=978-0-691-09182-2 |quote-page=5 |quote=calculi were in use in Iraq for primitive accounting systems as early as 3200–3000 BCE, with commodity-specific counting representation systems. Balanced accounting was in use by 3000–2350 BCE, and a [[sexagesimal number system]] was in use 2350–2000 BCE.}}</ref>{{efn|Robson has recommended at least one supplement to {{harvp|Schmandt-Besserat|1981}}, e.g., a review, {{cite journal |doi=10.1126/science.260.5114.1670 |last=Englund |first=R. |date=1993 |title=The origins of script |journal=Science |volume=260 |issue=5114 |pages=1670–1671 |pmid=17810210}}<ref>{{cite web |first=Eleanor |last=Robson |title=Bibliography of Mesopotamian Mathematics |url=https://it.stlawu.edu/~dmelvill/mesomath/erbiblio.html#genhist |access-date=2016-07-06 |archive-url=https://web.archive.org/web/20160616161807/http://it.stlawu.edu/~dmelvill/mesomath/erbiblio.html#genhist |url-status=dead |archive-date=2016-06-16}}</ref>}} The use of [[counting rods]] is one example. The [[abacus]] was early used for arithmetic tasks. What we now call the [[Roman abacus]] was used in [[Babylonia]] as early as {{circa|2700}}–2300 BC. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European [[counting house]], a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money.

Several [[analog computer]]s were constructed in ancient and medieval times to perform astronomical calculations. These included the [[astrolabe]] and [[Antikythera mechanism]] from the [[Hellenistic world]] (c. 150–100 BC).{{sfn|Lazos|1994}} In [[Roman Egypt]], [[Hero of Alexandria]] (c. 10–70 AD) made mechanical devices including [[Automaton|automata]] and a programmable [[cart]].<ref>{{citation |title=A programmable robot from 60 AD |first=Noel |last=Sharkey |date=4 July 2007 |volume=2611 |publisher=New Scientist |url=https://www.newscientist.com/blog/technology/2007/07/programmable-robot-from-60ad.html|archive-url=https://web.archive.org/web/20171213205451/https://www.newscientist.com/blog/technology/2007/07/programmable-robot-from-60ad.html|archive-date=13 December 2017}}</ref> The steam-powered automatic flute described by the ''[[Book of Ingenious Devices]]'' (850) by the Persian-Baghdadi [[Banū Mūsā brothers]] may have been the first programmable device.<ref name=Koetsier>{{Citation |last1=Koetsier |first1=Teun  |year=2001 |title=On the prehistory of programmable machines: musical automata, looms, calculators |journal=Mechanism and Machine Theory |volume=36 |issue=5 |pages=589–603 |publisher=Elsevier |doi=10.1016/S0094-114X(01)00005-2 |postscript=.}}</ref>

Other early mechanical devices used to perform one or another type of calculations include the [[planisphere]] and other mechanical computing devices invented by [[Al-Biruni]] (c. AD 1000); the [[equatorium]] and universal latitude-independent astrolabe by [[Al-Zarqali]] (c. AD 1015); the astronomical analog computers of other medieval [[Islamic astronomy|Muslim astronomers]] and engineers; and the astronomical [[clock tower]] of [[Su Song]] (1094) during the [[Song dynasty]]. The [[castle clock]], a [[hydropower]]ed mechanical [[astronomical clock]] invented by [[Ismail al-Jazari]] in 1206, was the first [[Computer programming|programmable]] analog computer.{{Disputed inline|for=The cited source doesn't support the claim, and the claim is misleading.|date=June 2022}}<ref name="Ancient Discoveries">{{citation|title=Episode 11: Ancient Robots|work=[[Ancient Discoveries]]|publisher=[[History Channel]]|url=https://www.youtube.com/watch?v=rxjbaQl0ad8|url-status=dead |access-date=2008-09-06|archive-date=2014-03-01 |archive-url=https://web.archive.org/web/20140301151115/https://www.youtube.com/watch?v=rxjbaQl0ad8}}</ref><ref>{{Cite book |last=Turner |first=Howard R. |title=Science in Medieval Islam: An Illustrated Introduction |page=184 |date=1997 |publisher=University of Texas press |isbn=978-0-292-78149-8 |location=Austin}}</ref><ref>{{cite magazine |author-link=Donald Routledge Hill |last=Hill |first=Donald Routledge |title=Mechanical Engineering in the Medieval Near East |magazine=Scientific American |date=May 1991 |pages=64–69}} ([[cf.]] {{cite web |last=Hill |first=Donald Routledge |title=IX. Mechanical Engineering |url= http://home.swipnet.se/islam/articles/HistoryofSciences.htm |work=History of Sciences in the Islamic World |archive-url=https://web.archive.org/web/20071225091836/http://home.swipnet.se/islam/articles/HistoryofSciences.htm |archive-date=2007-12-25 |url-status=dead}})</ref> [[Ramon Llull]] invented the Lullian Circle: a notional machine for calculating answers to philosophical questions (in this case, to do with Christianity) via logical combinatorics. This idea was taken up by [[Gottfried Leibniz|Leibniz]] centuries later, and is thus one of the founding elements in computing and [[information science]].

=== Renaissance calculating tools===
Scottish mathematician and physicist [[John Napier]] discovered that the multiplication and division of numbers could be performed by the addition and subtraction, respectively, of the [[logarithm]]s of those numbers. While producing the first logarithmic tables, Napier needed to perform many tedious multiplications. It was at this point that he designed his '[[Napier's bones]]', an abacus-like device that greatly simplified calculations that involved multiplication and division.{{efn|A Spanish implementation of [[Napier's bones]] (1617), is documented in {{harvnb|Montaner|Simon|1887|pp=19–20}}.}}

[[File:Sliderule 2005.png|thumb|upright=1.15|left|A modern slide rule]]
Since [[real number]]s can be represented as distances or intervals on a line, the [[slide rule]] was invented in the 1620s, shortly after Napier's work, to allow multiplication and division operations to be carried out significantly faster than was previously possible.{{sfn|Kells|Kern|Bland|1943|p=92}} [[Edmund Gunter]] built a calculating device with a single logarithmic scale at the [[University of Oxford]]. His device greatly simplified arithmetic calculations, including multiplication and division. [[William Oughtred]] greatly improved this in 1630 with his circular slide rule. He followed this up with the modern slide rule in 1632, essentially a combination of two [[Gunter's scale|Gunter rule]]s, held together with the hands. Slide rules were used by generations of engineers and other mathematically involved professional workers, until the invention of the [[pocket calculator]].{{sfn|Kells|Kern|Bland|1943|p=82}}

===Mechanical calculators===
In 1609, [[Guidobaldo del Monte]] made a mechanical multiplier to calculate fractions of a degree. Based on a system of four gears, the rotation of an index on one quadrant corresponds to 60 rotations of another index on an opposite quadrant.<ref>{{cite journal |first=Domenico Bertolini|last=Meli|date=1992|doi=10.1163/182539192x00019 |title=Guidobaldo Dal Monte and the Archimedean Revival |journal=Nuncius|number=1|pages=3–34|volume=7}}</ref> Thanks to this machine, errors in the calculation of first, second, third and quarter degrees can be avoided. Guidobaldo is the first to document the use of gears for mechanical calculation.

[[Wilhelm Schickard]], a German [[polymath]], designed a calculating machine in 1623 which combined a mechanized form of Napier's rods with the world's first mechanical adding machine built into the base. Because it made use of a single-tooth gear there were circumstances in which its carry mechanism would jam.<ref>{{harvnb|Williams|1997|p=128}} "...the single-tooth gear, like that used by Schickard, would not do for a general carry mechanism. The single-tooth gear works fine if the carry is only going to be propagated a few places but, if the carry has to be propagated several places along the accumulator, the force needed to operate the machine would be of such magnitude that it would do damage to the delicate gear works."</ref> A fire destroyed at least one of the machines in 1624 and it is believed Schickard was too disheartened to build another.

[[File:Pascaline calculator.jpg|thumb|View through the back of [[Pascal's calculator]]. [[Blaise Pascal|Pascal]] invented his machine in 1642.]]
In 1642, while still a teenager, [[Blaise Pascal]] started some pioneering work on calculating machines and after three years of effort and 50 prototypes<ref>{{Cite book |url=https://fr.wikisource.org/wiki/La_Machine_d%E2%80%99arithm%C3%A9tique |last=Pascal |first=Blaise |title=La Machine d'arithmétique |date=1645 |language=fr}}</ref> he invented a [[mechanical calculator]].{{sfn|Marguin|1994|p=48}}{{sfn|Ocagne|1893|p=245}} He built twenty of these machines (called [[Pascal's calculator]] or Pascaline) in the following ten years.{{sfn|Mourlevat|1988|p=12}} Nine Pascalines have survived, most of which are on display in European museums.{{efn|All nine machines are described in {{harvnb|Vidal|Vogt|2011}}.}} A continuing debate exists over whether Schickard or Pascal should be regarded as the "inventor of the mechanical calculator" and the range of issues to be considered is discussed elsewhere.<ref>{{cite web|first=Jim|last=Falk|title=Schickard versus Pascal - an empty debate?|url=https://metastudies.net/pmwiki/pmwiki.php?n=Site.SchicardvsPascal|access-date=2014-05-15 |archive-url=https://web.archive.org/web/20140408215848/http://metastudies.net/pmwiki/pmwiki.php?n=Site.SchicardvsPascal|archive-date=2014-04-08 |url-status=dead}}</ref>

[[File:Napier's calculating tables.JPG|thumb|left|A set of [[John Napier]]'s calculating tables from around 1680]]
[[Gottfried Wilhelm Leibniz|Gottfried Wilhelm von Leibniz]] invented the [[stepped reckoner]] and his [[Leibniz wheel|famous stepped drum mechanism]] around 1672. He attempted to create a machine that could be used not only for addition and subtraction but would use a moveable carriage to enable multiplication and division. Leibniz once said "It is unworthy of excellent men to lose hours like slaves in the labour of calculation which could safely be relegated to anyone else if machines were used."{{sfn|Smith|1929|pp=180–181}} However, Leibniz did not incorporate a fully successful carry mechanism. Leibniz also described the [[binary numeral system]],{{sfn|Leibniz|1703}} a central ingredient of all modern computers. However, up to the 1940s, many subsequent designs (including [[Charles Babbage]]'s machines of 1822 and even [[ENIAC]] of 1945) were based on the decimal system.{{efn|[[Binary-coded decimal]] (BCD) is a numeric representation, or [[character encoding]], which is still widely used.}}

[[File:Arithmometer - Detail of Multiplier pre 1851.jpg|thumb|Detail of an arithmometer built before 1851. The one-digit multiplier cursor (ivory top) is the leftmost cursor.]]

Around 1820, [[Charles Xavier Thomas|Charles Xavier Thomas de Colmar]] created what would over the rest of the century become the first successful, mass-produced mechanical calculator, the Thomas [[Arithmometer]]. It could be used to add and subtract, and with a moveable carriage the operator could also multiply, and divide by a process of long multiplication and long division.<ref>{{Cite web |date=2005 |title=Discovering the Arithmometer |url=https://www.cis.cornell.edu/boom/2005/ProjectArchive/arithometer/ |archive-url=https://web.archive.org/web/20060913173424/http://www.cis.cornell.edu/boom/2005/ProjectArchive/arithometer/index.html |archive-date=2006-09-13 |access-date=2023-08-26 |website=[[Cornell University]]}}</ref> It utilised a stepped drum similar in conception to that invented by Leibniz. Mechanical calculators remained in use until the 1970s.

===Punched-card data processing===
In 1804, French weaver [[Joseph Marie Jacquard]] developed [[Jacquard loom|a loom]] in which the pattern being woven was controlled by a paper tape constructed from [[punched cards]]. The paper tape could be changed without changing the mechanical design of the loom. This was a landmark achievement in programmability. His machine was an improvement over similar weaving looms. Punched cards were preceded by punch bands, as in the machine proposed by [[Basile Bouchon]]. These bands would inspire information recording for automatic pianos and more recently [[numerical control]] machine tools.

[[File:Early SSA accounting operations.jpg|thumb|upright|left|[[IBM]] punched-card accounting machines, 1936]]
In the late 1880s, the American [[Herman Hollerith]] invented data storage on [[punched card]]s that could then be read by a machine.<ref>{{cite web |url=https://www.columbia.edu/acis/history/hollerith.html |title=Herman Hollerith |website=Columbia University Computing History |publisher=Columbia University ACIS |access-date=2010-01-30 |archive-date=2011-05-13 |archive-url=https://web.archive.org/web/20110513134315/http://www.columbia.edu/acis/history/hollerith.html |url-status=live}}</ref> To process these punched cards, he invented the [[tabulating machine|tabulator]] and the [[keypunch]] machine. His machines used electromechanical [[relay]]s and [[Mechanical counter|counters]].<ref>{{cite book|author1-link=Leon E. Truesdell |last=Truesdell |first=Leon E. |title=The Development of Punch Card Tabulation in the Bureau of the Census 1890–1940|pages=47–55 |year=1965 |publisher=US GPO}}</ref> Hollerith's method was used in the [[1890 United States census]].<!-- The Census Bureau is not "an independent 3rd party" source – as required by Wikipedia – for Census Bureau performance claims. FOLLOWING CLAIM DELETED. -> and the completed results were "... finished months ahead of schedule and far under budget".<ref>{{cite web |title=Tabulation and Processing – History – U.S. Census Bureau |first=Jason |last=Gauthier |url=https://www.census.gov/history/www/innovations/technology/tabulation_and_processing.html |access-date=11 August 2015}}</ref>--> That census was processed two years faster than the prior census had been.<ref name="11th census report">{{cite book |title=Report of the Commissioner of Labor In Charge of The Eleventh Census to the Secretary of the Interior for the Fiscal Year Ending June 30, 1895 |location=Washington, DC |publisher=[[United States Government Publishing Office]] |date=29 July 1895 |oclc=867910652|hdl=2027/osu.32435067619882 |page=9}} "You may confidently look for the rapid reduction of the force of this office after the 1st of October, and the entire cessation of clerical work during the present calendar year. ... The condition of the work of the Census Division and the condition of the final reports show clearly that the work of the Eleventh Census will be completed at least two years earlier than was the work of the Tenth Census." — Carroll D. Wright, Commissioner of Labor in Charge</ref> Hollerith's company eventually became the core of [[International Business Machines|IBM]].

By 1920, electromechanical tabulating machines could add, subtract, and print accumulated totals.<ref>{{cite web |url=https://www.ibm.com/ibm/history/history/year_1920.html |website=IBM Archives |title=1920 |date=23 January 2003 |access-date=2020-12-01 |archive-date=2020-10-29 |archive-url=https://web.archive.org/web/20201029080349/https://www.ibm.com/ibm/history/history/year_1920.html |url-status=live }}</ref> Machine functions were directed <!-- other than the calculators (602, 604...) unit record machines are not programmed – there is no sequence of operations on their control panels. See [[plugboard]]--> by inserting dozens of wire jumpers into removable [[plugboard|control panel]]s. When the United States instituted [[Social Security (United States)|Social Security]] in 1935, IBM punched-card systems were used to process records of 26 million workers.<ref>{{cite web |url= https://www.ibm.com/ibm/history/history/decade_1930.html |website=IBM Archives |title=Chronological History of IBM: 1930s |date=23 January 2003 |access-date=2020-12-01 |archive-date=2020-12-03 |archive-url=https://web.archive.org/web/20201203145246/https://www.ibm.com/ibm/history/history/decade_1930.html |url-status=live }}</ref> Punched cards became ubiquitous in industry and government for accounting and administration.

[[Leslie Comrie]]'s articles on punched-card methods<ref>Leslie Comrie [https://adsabs.harvard.edu/full/1928MNRAS..88..506C (1928) On the Construction of Tables by Interpolation]</ref> and [[W. J. Eckert]]'s publication of ''Punched Card Methods in Scientific Computation'' in 1940, described punched-card techniques sufficiently advanced to solve some differential equations or perform multiplication and division using floating-point representations, all on punched cards and [[unit record equipment|unit record machines]].{{sfn|Eckert|1935}} Such machines were used during World War II for cryptographic statistical processing,<ref>{{citation | editor-last = Erskine | editor-first = Ralph | editor2-last = Smith | editor2-first = Michael | editor2-link = Michael Smith (newspaper reporter) | title = The Bletchley Park Codebreakers | publisher = Biteback Publishing Ltd | year = 2011 | page = 134| isbn = 978-184954078-0}} Updated and extended version of ''Action This Day: From Breaking of the Enigma Code to the Birth of the Modern Computer'' Bantam Press 2001</ref> as well as a vast number of administrative uses. The Astronomical Computing Bureau of [[Columbia University]] performed astronomical calculations representing the state of the art in [[computing]].<ref>{{cite web |author=Frank da Cruz |title=A Chronology of Computing at Columbia University |website=Columbia University Computing History |publisher=Columbia University |url=https://www.columbia.edu/cu/computinghistory/#timeline |access-date=2023-08-31|archive-date=2023-08-22 |archive-url=https://web.archive.org/web/20230822234349/http://www.columbia.edu/cu/computinghistory/#timeline |url-status=live}}</ref>{{sfn|Eckert|1940|pp=101–114}}

===Calculators===
{{Main|Calculator}}
[[File:Curta01.JPG|thumb|upright|The [[Curta]] calculator could also do multiplication and division.]]
By the 20th century, earlier mechanical calculators, cash registers, accounting machines, and so on were redesigned to use electric motors, with gear position as the representation for the state of a variable. The word "computer" was a job title assigned to primarily women who used these calculators to perform mathematical calculations.<ref>{{Cite journal|last=Light|first=Jennifer S. |date=July 1999|title=When Computers Were Women|journal=Technology and Culture|volume=40|issue=3|pages=455–483 |s2cid=108407884 |doi=10.1353/tech.1999.0128}}</ref> By the 1920s, British scientist [[Lewis Fry Richardson]]'s interest in weather prediction led him to propose [[human computer]]s and [[numerical analysis]] to model the weather; to this day, the most powerful computers on [[Earth]] are needed to adequately model its weather using the [[Navier–Stokes equations]].{{sfn|Hunt|1998}}

Companies like [[Friden, Inc.|Friden]], [[Marchant Calculator]] and [[Monroe Calculator Company|Monroe]] made desktop mechanical calculators from the 1930s that could add, subtract, multiply and divide.<ref>{{cite web |title=Friden Model STW-10 Electro-Mechanical Calculator |url=https://www.oldcalculatormuseum.com/fridenstw.html |access-date=11 August 2015|archive-date=2011-05-14 |archive-url=https://web.archive.org/web/20110514070335/http://www.oldcalculatormuseum.com/fridenstw.html|url-status=live}}</ref> In 1948, the [[Curta calculator|Curta]] was introduced by Austrian inventor [[Curt Herzstark]]. It was a small, hand-cranked mechanical calculator and as such, a descendant of [[Gottfried Leibniz]]'s [[Stepped Reckoner]] and [[Charles Xavier Thomas|Thomas]]' [[Arithmometer]].

The world's first ''all-electronic desktop'' calculator was the British [[Bell Punch]] [[Sumlock ANITA calculator|ANITA]], released in 1961.<ref>{{cite magazine |title=Simple and Silent |magazine=Office Magazine |date=December 1961 |page=1244}}</ref><ref>{{cite magazine |title='Anita' der erste tragbare elektonische Rechenautomat |trans-title='Anita' the first portable electronic computer |magazine=Buromaschinen Mechaniker |date=November 1961 |page=207}}</ref> It used [[vacuum tube]]s, cold-cathode tubes and [[Dekatron]]s in its circuits, with 12 cold-cathode [[Nixie tube|"Nixie"]] tubes for its display. The [[Sumlock ANITA calculator|ANITA]] sold well since it was the only electronic desktop calculator available, and was silent and quick. The tube technology was superseded in June 1963 by the U.S. manufactured [[Friden, Inc.|Friden]] EC-130, which had an all-transistor design, a stack of four 13-digit numbers displayed on a {{convert|5|in|cm|adj=on}} [[Cathode-ray tube|CRT]], and introduced [[reverse Polish notation]] (RPN).

==First proposed general-purpose computing device==
{{Main|Analytical Engine}}
[[File:Difference engine plate 1853.jpg|thumb|A portion of [[Charles Babbage|Babbage]]'s [[Difference Engine]] ]][[File:AnalyticalMachine Babbage London.jpg|thumb|left|Trial model of a part of the Analytical Engine, built by Babbage, as displayed at the Science Museum, London]]
The [[Industrial Revolution]] (late 18th to early 19th century) had a significant impact on the evolution of computing hardware, as the era's rapid advancements in machinery and manufacturing laid the groundwork for mechanized and automated computing. Industrial needs for precise, large-scale calculations—especially in fields such as navigation, engineering, and finance—prompted innovations in both design and function, setting the stage for devices like [[Charles Babbage|Charles Babbage's]] [[difference engine]] (1822).<ref>{{Cite book |last=Babbage |first=Charles |url=http://dx.doi.org/10.1017/cbo9781139103671 |title=Passages from the Life of a Philosopher |date=2011-10-12 |publisher=Cambridge University Press |doi=10.1017/cbo9781139103671 |isbn=978-1-108-03788-4}}</ref><ref>{{Cite book |last=Babbage |first=Charles |url=http://dx.doi.org/10.1017/cbo9780511696374 |title=On the Economy of Machinery and Manufactures |date=2010-03-04 |publisher=Cambridge University Press |doi=10.1017/cbo9780511696374 |isbn=978-1-108-00910-2}}</ref> This mechanical device was intended to automate the calculation of polynomial functions and represented one of the earliest applications of computational logic.<ref>{{Cite journal |last=Hutton |first=D.M. |date=2002-08-01 |title=The Difference Engine: Charles Babbage and the Quest to Build the First Computer |url=http://dx.doi.org/10.1108/k.2002.06731fae.009 |journal=Kybernetes |volume=31 |issue=6 |doi=10.1108/k.2002.06731fae.009 |issn=0368-492X|url-access=subscription }}</ref>

Babbage, often regarded as the "father of the computer," envisioned a fully mechanical system of gears and wheels, powered by steam, capable of handling complex calculations that previously required intensive manual labor.<ref>{{Cite journal |last=Tropp |first=Henry S. |date=December 1975 |title=''The Origins of Digital Computers: Selected Papers''. Brian Randell |url=http://dx.doi.org/10.1086/351520 |journal=Isis |volume=66 |issue=4 |pages=572–573 |doi=10.1086/351520 |issn=0021-1753|url-access=subscription }}</ref> His difference engine, designed to aid navigational calculations, ultimately led him to conceive the [[analytical engine]] in 1833.<ref>{{Cite journal |last1=W. |first1=J. W. |last2=Hyman |first2=Anthony |date=April 1986 |title=Charles Babbage, Pioneer of the Computer. |url=http://dx.doi.org/10.2307/2008013 |journal=Mathematics of Computation |volume=46 |issue=174 |pages=759 |doi=10.2307/2008013 |jstor=2008013 |issn=0025-5718|url-access=subscription }}</ref> This concept, far more advanced than his difference engine, included an [[arithmetic logic unit]], control flow through conditional branching and loops, and integrated memory.<ref>{{Cite book |last1=Campbell-Kelly |first1=Martin |last2=Aspray |first2=William |last3=Ensmenger |first3=Nathan |last4=Yost |first4=Jeffrey R. |date=2018-04-20 |title=Computer |url=http://dx.doi.org/10.4324/9780429495373 |doi=10.4324/9780429495373|isbn=978-0-429-49537-3 }}</ref> Babbage's plans made his analytical engine the first general-purpose design that could be described as [[Turing completeness|Turing-complete]] in modern terms.<ref>{{Citation |last=Turing |first=Alan |title=Computing Machinery and Intelligence (1950) |date=2004-09-09 |work=The Essential Turing |pages=433–464 |url=http://dx.doi.org/10.1093/oso/9780198250791.003.0017 |access-date=2024-10-30 |publisher=Oxford University PressOxford |doi=10.1093/oso/9780198250791.003.0017 |isbn=978-0-19-825079-1|url-access=subscription }}</ref><ref>{{Cite book |last=Davis |first=Martin |date=2018-02-28 |title=the Universal Computer |url=http://dx.doi.org/10.1201/9781315144726 |doi=10.1201/9781315144726|isbn=978-1-315-14472-6 }}</ref>

The analytical engine was programmed using [[Punched card input/output|punched cards]], a method adapted from the [[Jacquard machine|Jacquard loom]] invented by [[Joseph Marie Jacquard]] in 1804, which controlled textile patterns with a sequence of punched cards.<ref>{{Cite journal |last1=d'Ucel |first1=Jeanne |last2=Dib |first2=Mohammed |date=1958 |title=Le métier à tisser |url=http://dx.doi.org/10.2307/40098349 |journal=Books Abroad |volume=32 |issue=3 |pages=278 |doi=10.2307/40098349 |jstor=40098349 |issn=0006-7431|url-access=subscription }}</ref> These cards became foundational in later computing systems as well.<ref>{{Cite book |last=Heide |first=Lars |url=http://dx.doi.org/10.1353/book.3454 |title=Punched-Card Systems and the Early Information Explosion, 1880–1945 |date=2009 |publisher=Johns Hopkins University Press |doi=10.1353/book.3454 |isbn=978-0-8018-9143-4}}</ref> Babbage's machine would have featured multiple output devices, including a printer, a curve plotter, and even a bell, demonstrating his ambition for versatile computational applications beyond simple arithmetic.<ref>{{Cite journal |last=Bromley |first=A.G. |date=1998 |title=Charles Babbage's Analytical Engine, 1838 |url=http://dx.doi.org/10.1109/85.728228 |journal=IEEE Annals of the History of Computing |volume=20 |issue=4 |pages=29–45 |doi=10.1109/85.728228 |bibcode=1998IAHC...20d..29B |issn=1058-6180|url-access=subscription }}</ref>

[[Ada Lovelace]] expanded on Babbage's vision by conceptualizing algorithms that could be executed by his machine.<ref>{{Cite journal |last=Toole |first=Betty Alexandra |date=March 1991 |title=Ada, an analyst and a metaphysician |url=http://dx.doi.org/10.1145/122028.122031 |journal=ACM SIGAda Ada Letters |volume=XI |issue=2 |pages=60–71 |doi=10.1145/122028.122031 |issn=1094-3641|url-access=subscription }}</ref> Her notes on the analytical engine, written in the 1840s, are now recognized as the earliest examples of computer programming.<ref>{{Cite book |last1=Howard |first1=Emily |last2=De Roure |first2=David |chapter=Turning numbers into notes |date=2015 |title=Ada Lovelace Symposium 2015- Celebrating 200 Years of a Computer Visionary on - Ada Lovelace Symposium '15 |chapter-url=http://dx.doi.org/10.1145/2867731.2867746 |location=New York, New York, USA |publisher=ACM Press |pages=13 |doi=10.1145/2867731.2867746|isbn=978-1-4503-4150-9 }}</ref> Lovelace saw potential in computers to go beyond numerical calculations, predicting that they might one day generate complex musical compositions or perform tasks like language processing.<ref>{{Cite journal |last1=Haugtvedt |first1=Erica |last2=Abata |first2=Duane |title=Ada Lovelace: First Computer Programmer and Hacker? |url=http://dx.doi.org/10.18260/1-2--36646 |journal=2021 ASEE Virtual Annual Conference Content Access Proceedings |date=2021 |publisher=ASEE Conferences |doi=10.18260/1-2--36646}}</ref>

Though Babbage's designs were never fully realized due to technical and financial challenges, they influenced a range of subsequent developments in computing hardware. Notably, in the 1890s, [[Herman Hollerith]] adapted the idea of punched cards for automated data processing, which was utilized in the U.S. Census and sped up data tabulation significantly, bridging industrial machinery with data processing.<ref>{{Cite thesis |last=Blodgett |first=John H. |title=Herman Hollerith, data processing pioneer |date=1968 |publisher=Drexel University Libraries |doi=10.17918/00004750 |url=http://dx.doi.org/10.17918/00004750|url-access=subscription }}</ref>

The Industrial Revolution's advancements in mechanical systems demonstrated the potential for machines to conduct complex calculations, influencing engineers like [[Leonardo Torres Quevedo]] and [[Vannevar Bush]] in the early 20th century. Torres Quevedo designed an electromechanical machine with floating-point arithmetic,<ref>{{Citation |last=Torres y Quevedo |first=Leonardo |title=Essays on Automatics |date=1982 |work=The Origins of Digital Computers |pages=89–107 |url=http://dx.doi.org/10.1007/978-3-642-61812-3_6 |access-date=2024-10-30 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |doi=10.1007/978-3-642-61812-3_6 |isbn=978-3-642-61814-7|url-access=subscription }}</ref> while Bush's later work explored electronic digital computing.<ref>{{Citation |title=6 Vannevar Bush, from "As We May Think" (1945) |date=2021 |work=Information |publisher=Columbia University Press |doi=10.7312/hayo18620-032 |isbn=978-0-231-54654-6|doi-access=free }}</ref> By the mid-20th century, these innovations paved the way for the first fully electronic computers.<ref>{{Cite book |last1=Haigh |first1=Thomas |url=http://dx.doi.org/10.7551/mitpress/11436.001.0001 |title=A New History of Modern Computing |last2=Ceruzzi |first2=Paul E. |date=2021-09-14 |publisher=The MIT Press |doi=10.7551/mitpress/11436.001.0001 |isbn=978-0-262-36648-9}}</ref>

==Analog computers==
{{Main|Analog computer}}
{{Further|Mechanical computer}}
[[File:099-tpm3-sk.jpg|thumb|[[William Thomson, 1st Baron Kelvin|Sir William Thomson]]'s third tide-predicting machine design, 1879–81]]
In the first half of the 20th century, [[analog computer]]s were considered by many to be the future of computing. These devices used the continuously changeable aspects of physical phenomena such as [[Electrical network|electrical]], [[Mechanics|mechanical]], or [[hydraulic]] quantities to [[Scientific modelling|model]] the problem being solved, in contrast to [[digital computer]]s that represented varying quantities symbolically, as their numerical values change. As an analog computer does not use discrete values, but rather continuous values, processes cannot be reliably repeated with exact equivalence, as they can with [[Turing machine]]s.{{sfn|Chua|1971|pp=507–519}}

The first modern analog computer was a [[tide-predicting machine]], invented by [[Lord Kelvin|Sir William Thomson]], later Lord Kelvin, in 1872. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location and was of great utility to navigation in shallow waters. His device was the foundation for further developments in analog computing.<ref name="stanf">{{cite encyclopedia |encyclopedia=Stanford Encyclopedia of Philosophy |title=The Modern History of Computing|year=2017 |publisher=Metaphysics Research Lab, Stanford University |url=https://plato.stanford.edu/entries/computing-history/ |access-date=2014-01-07 |archive-date=2010-07-12 |archive-url=https://web.archive.org/web/20100712072148/http://plato.stanford.edu/entries/computing-history/|url-status=live}}</ref>

The [[differential analyser]], a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by [[James Thomson (engineer)|James Thomson]], the brother of the more famous Lord Kelvin. He explored the possible construction of such calculators, but was stymied by the limited output torque of the [[ball-and-disk integrator]]s.<ref>{{cite web |first=Ray |last=Girvan |title=The revealed grace of the mechanism: computing after Babbage |work=Scientific Computing World |date=May–June 2003 |url=https://www.scientific-computing.com/scwmayjun03computingmachines.html |archive-url=https://web.archive.org/web/20121103094710/http://www.scientific-computing.com/scwmayjun03computingmachines.html |archive-date=3 November 2012}}</ref> In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output.

A notable series of analog calculating machines were developed by [[Leonardo Torres Quevedo#Analogue calculating machines|Leonardo Torres Quevedo]] since 1895, including one that was able to compute the roots of arbitrary [[polynomial]]s of order eight, including the complex ones, with a precision down to thousandths.<ref>{{Cite journal |last=Torres |first=Leonardo |author-link=Leonardo Torres Quevedo |date=1895-10-10 |title=Memória sobre las Máquinas Algébricas |url=https://quickclick.es/rop/pdf/publico/1895/1895_tomoI_28_01.pdf |journal=Revista de Obras Públicas |language=es |issue=28 |pages=217–222}}</ref><ref name="MaquinasAlgebricasLTQ">Leonardo Torres. ''[https://books.google.com/books?id=Eo0NAQAAIAAJ Memoria sobre las máquinas algébricas: con un informe de la Real academia de ciencias exactas, fisicas y naturales]'', Misericordia, 1895.</ref><ref name="Thomas2008">{{Cite journal |last=Thomas |first=Federico |date=2008-08-01 |title=A short account on Leonardo Torres' endless spindle |url=https://www.sciencedirect.com/science/article/pii/S0094114X07001231 |journal=[[Mechanism and Machine Theory]] |publisher=[[International Federation for the Promotion of Mechanism and Machine Science|IFToMM]] |volume=43 |issue=8 |pages=1055–1063 |doi=10.1016/j.mechmachtheory.2007.07.003 |issn=0094-114X|hdl=10261/30460 |hdl-access=free }}</ref>

[[File:US Army AF Drift Sight Mk. I on DH4.jpeg|thumb|left|A Mk. I Drift Sight. The lever just in front of the bomb aimer's fingertips sets the altitude, the wheels near his knuckles set the wind and airspeed.]]
An important advance in analog computing was the development of the first [[fire-control system]]s for long range [[ship]] [[Gun laying|gunlaying]]. When gunnery ranges increased dramatically in the late 19th century it was no longer a simple matter of calculating the proper aim point, given the flight times of the shells. Various spotters on board the ship would relay distance measures and observations to a central plotting station. There the fire direction teams fed in the location, speed and direction of the ship and its target, as well as various adjustments for [[Coriolis effect]], weather effects on the air, and other adjustments; the computer would then output a firing solution, which would be fed to the turrets for laying. In 1912, British engineer [[Arthur Pollen]] developed the first electrically powered mechanical [[analogue computer]] (called at the time the Argo Clock).{{Citation needed|date=September 2017}} It was used by the [[Imperial Russian Navy]] in [[World War I]].{{Citation needed|date=October 2008}} The alternative [[Frederic Charles Dreyer#Dreyer Fire Control Table|Dreyer Table]] fire control system was fitted to British capital ships by mid-1916.

Mechanical devices were also used to aid the [[bombsight|accuracy of aerial bombing]]. [[Drift Sight]] was the first such aid, developed by [[Harry Wimperis]] in 1916 for the [[Royal Naval Air Service]]; it measured the [[wind speed]] from the air, and used that measurement to calculate the wind's effects on the trajectory of the bombs. The system was later improved with the [[Course Setting Bomb Sight]], and reached a climax with [[World War II]] bomb sights, [[Mark XIV bomb sight]] ([[RAF Bomber Command]]) and the [[Norden bombsight|Norden]]<ref>{{cite web |title=Norden M9 Bombsight |publisher=National Museum of the USAF |url=https://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=8056 |access-date=2008-05-17 |archive-url=https://web.archive.org/web/20070829071916/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=8056 |archive-date=2007-08-29 |url-status=dead}}</ref> ([[United States Army Air Forces]]).

The art of mechanical analog computing reached its zenith with the [[differential analyzer]],{{sfn|Coriolis|1836|pp=5–9}} built by H. L. Hazen and [[Vannevar Bush]] at [[MIT]] starting in 1927, which built on the mechanical integrators of [[James Thomson (engineer)|James Thomson]] and the [[torque amplifier]]s invented by H. W. Nieman. A dozen of these devices were built before their obsolescence became obvious; the most powerful was constructed at the [[University of Pennsylvania]]'s [[Moore School of Electrical Engineering]], where the [[ENIAC]] was built.

A fully electronic analog computer was built by [[Helmut Hölzer]] in 1942 at [[Peenemünde Army Research Center]].<ref>{{Cite journal |doi=10.1109/MAHC.1985.10025 |title=Helmut Hoelzer's Fully Electronic Analog Computer |journal= IEEE Annals of the History of Computing |volume=7 |issue=3 |pages=227–240 |year=1985 |last1=Tomayko |first1=James E. |bibcode=1985IAHC....7c.227T |s2cid=15986944}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=L6BfBgAAQBAJ&q=Hoelzer%201942&pg=PT138|title=The Rocket and the Reich: Peenemunde and the Coming of the Ballistic Missile Era|last=Neufeld|first=Michael J.|date=2013-09-10|publisher=Smithsonian Institution |isbn=9781588344663|page=138|access-date=2020-10-18 |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181641/https://books.google.com/books?id=L6BfBgAAQBAJ&q=Hoelzer%201942&pg=PT138|url-status=live}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=y1DpBQAAQBAJ&pg=PA38|title=Analog Computing |last=Ulmann|first=Bernd|date=2013-07-22 |publisher=Walter de Gruyter|isbn=9783486755183|page=38 |access-date=2021-12-27 |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181642/https://books.google.com/books?id=y1DpBQAAQBAJ&pg=PA38|url-status=live}}</ref>

By the 1950s the success of digital electronic computers had spelled the end for most analog computing machines, but [[hybrid computer|hybrid analog computers]], controlled by digital electronics, remained in substantial use into the 1950s and 1960s, and later in some specialized applications.

==Advent of the digital computer==
[[File:Women holding parts of the first four Army computers.jpg|right|thumb|Parts from four early computers, 1962. From left to right: [[ENIAC]] board, [[EDVAC]] board, [[ORDVAC]] board, and [[BRLESC]]-I board, showing the trend toward [[miniaturization]].]]
The principle of the modern computer was first described by computer scientist [[Alan Turing]], who set out the idea in his seminal 1936 paper,<ref name=Turing-1937-1938>{{harvs|nb |last=Turing |year=1937 |year2=1938}}</ref> ''On Computable Numbers''. Turing reformulated [[Kurt Gödel]]'s 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as [[Turing machine]]s. He proved that some such machine would be capable of performing any conceivable mathematical computation if it were representable as an [[algorithm]]. He went on to prove that there was no solution to the ''[[Entscheidungsproblem]]'' by first showing that the [[halting problem]] for Turing machines is [[Decision problem|undecidable]]: in general, it is not possible to decide algorithmically whether a given Turing machine will ever halt.

He also introduced the notion of a "universal machine" (now known as a [[universal Turing machine]]), with the idea that such a machine could perform the tasks of any other machine, or in other words, it is provably capable of computing anything that is computable by executing a program stored on tape, allowing the machine to be programmable. [[John von Neumann]] acknowledged that the central concept of the modern computer was due to this paper.<ref>{{harvnb|Copeland|2004|p=22}}: "von Neumann&nbsp;... firmly emphasized to me, and to others I am sure, that the fundamental conception is owing to Turing—insofar as not anticipated by Babbage, Lovelace and others. Letter by [[Stanley Frankel]] to [[Brian Randell]], 1972."</ref> Turing machines are to this day a central object of study in [[theory of computation]]. Except for the limitations imposed by their finite memory stores, modern computers are said to be [[Turing-complete]], which is to say, they have [[algorithm]] execution capability equivalent to a [[universal Turing machine]].

===Electromechanical computers===
{{Further|Mechanical computer#Electro-mechanical computers}}
The era of modern computing began with a flurry of development before and during World War II. Most digital computers built in this period were electromechanical – electric switches drove mechanical relays to perform the calculation. These mechanical components had a low operating speed due to their mechanical nature and were eventually superseded by much faster all-electric components, originally using [[vacuum tube]]s and later [[transistor]]s.

The [[Z2 (computer)|Z2]] was one of the earliest examples of an electric operated digital [[computer]] built with electromechanical relays and was created by civil engineer [[Konrad Zuse]] in 1940 in Germany. It was an improvement on his earlier, mechanical [[Z1 (computer)|Z1]]; although it used the same mechanical [[computer memory|memory]], it replaced the arithmetic and control logic with electrical [[relay]] circuits.<ref name="Part 4 Zuse">{{cite web |url=https://www.epemag.com/zuse/part4a.htm|title=Part 4: Konrad Zuse's Z1 and Z3 Computers|last=Zuse|first=Horst |work=The Life and Work of Konrad Zuse|publisher=EPE Online |access-date=2008-06-17 |archive-url=https://web.archive.org/web/20080601210541/http://www.epemag.com/zuse/part4a.htm |archive-date = 2008-06-01}}</ref>

In the same year, electro-mechanical devices called [[bombe]]s were built by British [[cryptologist]]s to help decipher [[Germany|German]] [[Enigma machine|Enigma-machine]]-encrypted secret messages during [[World War II]]. The bombe's initial design was created in 1939 at the UK [[Government Code and Cypher School]] at [[Bletchley Park]] by [[Alan Turing]],{{sfn|Smith|2007|p=60}} with an important refinement devised in 1940 by [[Gordon Welchman]].{{sfn|Welchman|1984|p=77}} The engineering design and construction was the work of [[Harold Keen]] of the [[British Tabulating Machine Company]]. It was a substantial development from a device that had been designed in 1938 by [[Polish Cipher Bureau]] cryptologist [[Marian Rejewski]], and known as the "[[Bomba (cryptography)|cryptologic bomb]]" ([[Polish language|Polish]]: ''"bomba kryptologiczna"'').

[[File:Z3 Deutsches Museum.JPG|thumb|left|Replica of [[Konrad Zuse|Zuse]]'s [[Z3 (computer)|Z3]], the first fully automatic, digital (electromechanical) computer]]
In 1941, Zuse followed his earlier machine up with the [[Z3 (computer)|Z3]],<ref name="Part 4 Zuse"/> the world's first working [[electromechanical]] [[Computer programming|programmable]], fully automatic digital computer.<ref>{{cite news|title=A Computer Pioneer Rediscovered, 50 Years On |newspaper=The New York Times |url=https://www.nytimes.com/1994/04/20/news/20iht-zuse.html |date=20 April 1994 |access-date=2017-02-16 |archive-date=2016-11-04 |archive-url=https://web.archive.org/web/20161104051054/http://www.nytimes.com/1994/04/20/news/20iht-zuse.html|url-status=live}}</ref> The Z3 was built with 2000 [[relay]]s, implementing a 22-[[bit]] [[Word (computer architecture)|word length]] that operated at a [[clock rate|clock frequency]] of about 5–10&nbsp;[[Hertz|Hz]].{{sfn|Zuse|1993|p=55}} Program code and data were stored on punched [[celluloid|film]]. It was quite similar to modern machines in some respects, pioneering numerous advances such as [[floating-point arithmetic|floating-point numbers]]. Replacement of the hard-to-implement decimal system (used in [[Charles Babbage]]'s earlier design) by the simpler [[binary number|binary]] system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time.<ref>{{cite web |url=https://www.crash-it.com/crash/index.php?page=73 |archive-url=https://web.archive.org/web/20080318184915/http://www.crash-it.com/crash/index.php?page=73 |url-status=dead |archive-date=2008-03-18 |title=Zuse |work=Crash! The Story of IT}}</ref> Despite lacking explicit conditional execution, the Z3 was proven to have been a theoretically [[Turing machine|Turing-complete machine]] in 1998 by [[Raúl Rojas]].<ref>{{Cite journal|last=Rojas|first=Raúl|title=How to Make Zuse's Z3 a Universal Computer |journal=IEEE Annals of the History of Computing |date=1998 |volume=20 |issue=3 |page=51 |doi=10.1109/85.707574 |bibcode=1998IAHC...20c..51R |citeseerx=10.1.1.37.665}}</ref> In two 1936 [[patent]] applications, Zuse also anticipated that machine instructions could be stored in the same storage used for data—the key insight of what became known as the [[von Neumann architecture]], first implemented in 1948 in America in the [[Mechanical computer#Electro-mechanical computers|electromechanical]] [[IBM SSEC]] and in Britain in the fully electronic [[Manchester Baby]].<ref>{{cite journal |title=Electronic Digital Computers |journal=Nature |last1=Williams |first1=F. C. |last2=Kilburn |first2=T. |date=25 September 1948 |volume=162 |issue=4117 |page=487 |bibcode=1948Natur.162..487W |doi=10.1038/162487a0 |s2cid=4110351 |doi-access=free }}</ref>

Zuse suffered setbacks during World War II when some of his machines were destroyed in the course of [[Allies of World War II|Allied]] bombing campaigns. Apparently his work remained largely unknown to engineers in the UK and US until much later, although at least IBM was aware of it as it financed his post-war startup company in 1946 in return for an option on Zuse's patents.

In 1944, the [[Harvard Mark I]] was constructed at IBM's Endicott laboratories.{{sfn|Da Cruz|2008}} It was a similar general purpose electro-mechanical computer to the Z3, but was not quite Turing-complete.

===Digital computation===
The term digital was first suggested by [[George Stibitz|George Robert Stibitz]] and refers to where a signal, such as a voltage, is not used to directly represent a value (as it would be in an [[analog computer]]), but to encode it. In November 1937, Stibitz, then working at Bell Labs (1930–1941),<ref name=":0">{{cite web |title=Computer Pioneers – George Stibitz |url=https://history.computer.org/pioneers/stibitz.html |website=history.computer.org |access-date=2018-11-08 |archive-date=2018-10-05 |archive-url=https://web.archive.org/web/20181005004432/http://history.computer.org/pioneers/stibitz.html |url-status=live}}</ref> completed a relay-based calculator he later dubbed the "[[Model K (calculator)|Model K]]" (for "'''k'''itchen table", on which he had assembled it), which became the first [[binary adder]].<ref>{{cite book|last=Ritchie |first=David|date=1986|title=The Computer Pioneers|page=[https://archive.org/details/computerpioneers00ritc/page/35 35]|location=New York|publisher=Simon and Schuster |isbn=067152397X|url=https://archive.org/details/computerpioneers00ritc}}</ref> Typically signals have two states – low (usually representing 0) and high (usually representing 1), but sometimes [[three-valued logic]] is used, especially in high-density memory. Modern computers generally use [[Boolean logic|binary logic]], but many early machines were [[decimal computer]]s. In these machines, the basic unit of data was the decimal digit, encoded in one of several schemes, including [[binary-coded decimal]] or BCD, [[Bi-quinary coded decimal|bi-quinary]], [[excess-3]], and [[two-out-of-five code]].

The mathematical basis of digital computing is [[Boolean algebra]], developed by the British mathematician [[George Boole]] in his work ''[[The Laws of Thought]]'', published in 1854. His Boolean algebra was further refined in the 1860s by [[William Jevons]] and [[Charles Sanders Peirce]], and was first presented systematically by [[Ernst Schröder (mathematician)|Ernst Schröder]] and [[A. N. Whitehead]].<ref name="DunnHardegree2001">{{cite book|first1=J. Michael|last1=Dunn|first2=Gary M.|last2=Hardegree|year=2001 |title=Algebraic methods in philosophical logic |url=https://books.google.com/books?id=-AokWhbILUIC&pg=PA2 |publisher=Oxford University Press US|isbn=978-0-19-853192-0|page=2|access-date=2016-06-04 |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181643/https://books.google.com/books?id=-AokWhbILUIC&pg=PA2|url-status=live}}</ref> In 1879 Gottlob Frege developed the formal approach to logic and proposes the first logic language for logical equations.<ref>{{cite book|title=Begriffsschrift: eine der arithmetischen nachgebildete Formelsprache des reinen Denkens|author=Arthur Gottlob Frege}}</ref>

In the 1930s and working independently, American [[electronic engineer]] [[Claude Shannon]] and Soviet [[logician]] [[Victor Shestakov]] both showed a [[one-to-one correspondence]] between the concepts of [[Boolean logic]] and certain electrical circuits, now called [[logic gate]]s, which are now ubiquitous in digital computers.{{sfn|Shannon|1938}} They showed that electronic relays and switches can realize the [[expression (mathematics)|expression]]s of [[Boolean algebra (logic)|Boolean algebra]].{{sfn|Shannon|1940}} This thesis essentially founded practical [[digital circuit]] design. In addition Shannon's paper gives a correct circuit diagram for a 4 bit digital binary adder.{{sfn|Shannon|1938|pp=494–495|ps=.{{verify source|date=August 2023|reason=Neither Shannon (1938) of Shannon (1940) include pages 494–495.}}}}

===Electronic data processing===
[[File:Atanasoff-Berry Computer at Durhum Center.jpg|thumb|[[Atanasoff–Berry Computer]] replica at first floor of Durham Center, [[Iowa State University]] ]]
Purely [[electronic circuit]] elements soon replaced their mechanical and electromechanical equivalents, at the same time that digital calculation replaced analog. Machines such as the [[Z3 (computer)|Z3]], the [[Atanasoff–Berry Computer]], the [[Colossus computer]]s, and the [[ENIAC]] were built by hand, using circuits containing relays or valves (vacuum tubes), and often used [[punched card]]s or [[punched tape|punched paper tape]] for input and as the main (non-volatile) storage medium.<ref>{{Cite journal |last=Guarnieri|first=M.|year=2012|title=The Age of Vacuum Tubes: Merging with Digital Computing &#91;Historical&#93; |journal=IEEE Industrial Electronics Magazine|volume=6 |issue=3|pages=52–55|doi=10.1109/MIE.2012.2207830 |s2cid=41800914}}</ref>

Engineer [[Tommy Flowers]] joined the telecommunications branch of the [[General Post Office]] in 1926. While working at the [[Post Office Research Station|research station]] in [[Dollis Hill]] in the 1930s, he began to explore the possible use of electronics for the [[telephone exchange]]. Experimental equipment that he built in 1934 went into operation 5 years later, converting a portion of the [[telephone exchange]] network into an electronic data processing system, using thousands of [[vacuum tube]]s.<ref name="stanf" />

In the US, in 1940 Arthur Dickinson (IBM) invented the first digital electronic computer.<ref>{{cite book |title=Building IBM: Shaping an Industry and its Technology|first=Emerson W.|last=Pugh|publisher=[[The MIT Press]]|year=1996}}</ref> This calculating device was fully electronic – control, calculations and output (the first electronic display).<ref>{{cite web |url=https://www.ibm.com/ibm/history/ibm100/us/en/icons/patents/ |access-date=2020-12-01 |title=Patents and Innovation |website=IBM 100 |date=7 March 2012 |archive-date=2020-12-02 |archive-url=https://web.archive.org/web/20201202140105/https://www.ibm.com/ibm/history/ibm100/us/en/icons/patents/ |url-status=live}}</ref> John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed the Atanasoff–Berry Computer (ABC) in 1942,<ref>15 January 1941 notice in the ''Des Moines Register''</ref> the first binary electronic digital calculating device.<ref>{{cite book |title=The First Electronic Computer: the Atanasoff story |url=https://archive.org/details/firstelectronicc0000burk |url-access=registration |first1=Alice R. |last1=Burks |first2=Arthur W. |last2=Burks |year=1988 |location=Ann Arbor |publisher=University of Michigan Press |isbn=0-472-10090-4}}</ref> This design was semi-electronic (electro-mechanical control and electronic calculations), and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory. However, its paper card writer/reader was unreliable and the regenerative drum contact system was mechanical. The machine's special-purpose nature and lack of changeable, [[stored-program computer|stored program]] distinguish it from modern computers.{{sfn|Copeland|2006|p=107}}

Computers whose logic was primarily built using vacuum tubes are now known as [[vacuum-tube computer|first generation computers]].

===The electronic programmable computer===
{{Main|Colossus computer|ENIAC}}
[[File:Colossus.jpg|thumb|Colossus was the first [[electronics|electronic]] [[Digital electronics|digital]] [[Computer programming|programmable]] computing device, and was used to break German ciphers during World War II. It remained unknown, as a military secret, well into the 1970s.]]
During World War II, British codebreakers at [[Bletchley Park]], {{convert|40|mi|km}} north of London, achieved a number of successes at breaking encrypted enemy military communications. The German encryption machine, [[Enigma (machine)|Enigma]], was first attacked with the help of the electro-mechanical [[bombe]]s.{{sfn|Welchman|1984|pp=138–145, 295–309}} They ruled out possible Enigma settings by performing chains of logical deductions implemented electrically. Most possibilities led to a contradiction, and the few remaining could be tested by hand.

The Germans also developed a series of teleprinter encryption systems, quite different from Enigma. The [[Lorenz SZ 40/42]] machine was used for high-level Army communications, code-named "Tunny" by the British. The first intercepts of Lorenz messages began in 1941. As part of an attack on Tunny, [[Max Newman]] and his colleagues developed the [[Heath Robinson (codebreaking machine)|Heath Robinson]], a fixed-function machine to aid in code breaking.{{sfn|Copeland|2006|p=182}} [[Tommy Flowers]], a senior engineer at the [[Post Office Research Station]]{{sfn|Randell|1980|p=9}} was recommended to Max Newman by Alan Turing{{sfn|Budiansky|2000|p=314}} and spent eleven months from early February 1943 designing and building the more flexible [[Colossus computer]] (which superseded the [[Heath Robinson (codebreaking machine)|Heath Robinson]]).<ref>{{cite news |title=Bletchley's code-cracking Colossus |newspaper=BBC News |date=2 February 2010 |url=https://news.bbc.co.uk/2/hi/technology/8492762.stm |access-date=19 October 2012 |url-status=live |archive-date=2020-03-08 |archive-url=https://web.archive.org/web/20200308163851/http://news.bbc.co.uk/2/hi/technology/8492762.stm}}</ref><ref>{{Citation |last=Fensom|first=Jim|title=Harry Fensom obituary |newspaper=The Guardian |date=8 November 2010 |url=https://www.theguardian.com/theguardian/2010/nov/08/harry-fensom-obituary|access-date=17 October 2012|archive-date=2013-09-17 |archive-url=https://web.archive.org/web/20130917220225/http://www.theguardian.com/theguardian/2010/nov/08/harry-fensom-obituary |url-status=live}}</ref> After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944<ref>{{cite web |last=Sale |first=Tony |title=Colossus - The Rebuild Story |publisher=The National Museum of Computing |url=https://www.tnmoc.org/colossus-rebuild-story |archive-url=https://web.archive.org/web/20150418230306/http://www.tnmoc.org/colossus-rebuild-story |archive-date=2015-04-18 |url-status=dead}}</ref> and attacked its first message on 5 February.{{sfn|Copeland|2006|p=75}} By the time Germany surrendered in May 1945, there were ten [[Colossus computer|Colossi]] working at Bletchley Park.{{sfn|Copeland|2006|p=2}}

[[File:Wartime photo of Colossus 10.png|thumb|left|Wartime photo of Colossus No. 10]]
Colossus was the world's first [[electronics|electronic]] [[digital electronics|digital]] [[Computer programming|programmable]] [[computer]].<ref name="stanf" /> It used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured to perform a variety of [[Boolean logic]]al operations on its data,<ref>{{Citation |last=Small |first=Albert W. |title=The Special Fish Report |publisher=The American National Archive (NARA) |location=College Campus Washington |date=December 1944 |url=https://www.codesandciphers.org.uk/documents/small/smallix.htm |access-date=2019-01-11 |archive-date=2011-05-15 |archive-url=https://web.archive.org/web/20110515021436/http://www.codesandciphers.org.uk/documents/small/smallix.htm |url-status=live}}</ref> but it was not [[Turing-complete]]. Data input to Colossus was by [[photoelectric sensor|photoelectric]] reading of a paper tape transcription of the enciphered intercepted message. This was arranged in a continuous loop so that it could be read and re-read multiple times – there being no internal store for the data. The reading mechanism ran at 5,000 characters per second with the paper tape moving at {{cvt|40|ft/s|m/s mph|sigfig=3}}. Colossus Mark 1 contained 1500 thermionic valves (tubes), but Mark 2 with 2400 valves and five processors in parallel, was both 5 times faster and simpler to operate than Mark 1, greatly speeding the decoding process. Mark 2 was designed while Mark 1 was being constructed. [[Allen Coombs]] took over leadership of the Colossus Mark 2 project when [[Tommy Flowers]] moved on to other projects.<ref>{{Citation |last1=Randell |first1=Brian |author-link=Brian |last2=Fensom |first2=Harry |last3=Milne |first3=Frank A. |title=Obituary: Allen Coombs |newspaper=The Independent |date=15 March 1995 |url=https://www.independent.co.uk/news/people/obituary-allen-coombs-1611270.html |access-date=18 October 2012 |archive-date=2012-02-03 |archive-url=https://web.archive.org/web/20120203042657/http://www.independent.co.uk/news/people/obituary-allen-coombs-1611270.html |url-status=dead}}</ref> The first Mark 2 Colossus became operational on 1 June 1944, just in time for the Allied [[Invasion of Normandy]] on [[Normandy landings|D-Day]].

Most of the use of Colossus was in determining the start positions of the Tunny rotors for a message, which was called "wheel setting". Colossus included the first-ever use of [[shift register]]s and [[systolic array]]s, enabling five simultaneous tests, each involving up to 100 [[Boolean algebra|Boolean calculations]]. This enabled five different possible start positions to be examined for one transit of the paper tape.<ref>{{Citation |last=Flowers |first=T. H. |author-link=Tommy Flowers |title=The Design of Colossus |journal=Annals of the History of Computing |volume=5 |issue=3 |pages=239–252 |year=1983 |doi=10.1109/MAHC.1983.10079 |s2cid=39816473 |url=https://www.ivorcatt.com/47c.htm |access-date=2019-03-03 |archive-date=2006-03-26 |archive-url=https://web.archive.org/web/20060326041703/http://www.ivorcatt.com/47c.htm |url-status=live}}</ref> As well as wheel setting some later [[Colossus computer|Colossi]] included mechanisms intended to help determine pin patterns known as "wheel breaking". Both models were programmable using switches and plug panels in a way their predecessors had not been.

[[File:Glen Beck and Betty Snyder program the ENIAC in building 328 at the Ballistic Research Laboratory.jpg|thumb|[[ENIAC]] was the first Turing-complete electronic device, and performed ballistics trajectory calculations for the [[United States Army]].<ref>{{cite magazine |date=2014-11-25 |title=How the World's First Computer Was Rescued From the Scrap Heap |url=https://www.wired.com/2014/11/eniac-unearthed/ |first=Brendan I. |last=Loerner |magazine=Wired |access-date=2017-03-07 |archive-date=2017-05-02 |archive-url=https://web.archive.org/web/20170502064714/https://www.wired.com/2014/11/eniac-unearthed/ |url-status=live}}</ref>]]
Without the use of these machines, the [[Allies of World War II|Allies]] would have been deprived of the very valuable [[military intelligence|intelligence]] that was obtained from reading the vast quantity of [[encipher]]ed high-level [[telegraphy|telegraphic]] messages between the [[Oberkommando der Wehrmacht|German High Command (OKW)]] and their [[Wehrmacht|army]] commands throughout occupied Europe. Details of their existence, design, and use were kept secret well into the 1970s. [[Winston Churchill]] personally issued an order for their destruction into pieces no larger than a man's hand, to keep secret that the British were capable of cracking [[Lorenz cipher|Lorenz SZ cyphers]] (from German rotor stream cipher machines) during the oncoming Cold War. Two of the machines were transferred to the newly formed [[GCHQ]] and the others were destroyed. As a result, the machines were not included in many histories of computing.{{efn|The existence of Colossus was kept secret by the UK Government for 30 years and so was not known to American computer scientists, such as [[Gordon Bell]] and [[Allen Newell]]. And was not in {{harvp|Bell|Newell|1971}} ''Computing Structures'', a standard reference work in the 1970s.}} A reconstructed working copy of one of the Colossus machines is now on display at Bletchley Park.

The [[ENIAC]] (Electronic Numerical Integrator and Computer) was the first electronic programmable computer built in the US. Although the ENIAC used similar technology to the [[Colossus computer|Colossi]], it was much faster and more flexible and was Turing-complete. Like the Colossi, a "program" on the ENIAC was defined by the states of its patch cables and switches, a far cry from the [[stored-program computer|stored-program]] electronic machines that came later. Once a program was ready to be run, it had to be mechanically set into the machine with manual resetting of plugs and switches. The programmers of the ENIAC were women who had been trained as mathematicians.{{Sfn|Evans|2018|p=39}}

It combined the high speed of electronics with the ability to be programmed for many complex problems. It could add or subtract 5000 times a second, a thousand times faster than any other machine. It also had modules to multiply, divide, and square root. High-speed memory was limited to 20 words (equivalent to about 80 bytes). Built under the direction of [[John Mauchly]] and [[J. Presper Eckert]] at the University of Pennsylvania, ENIAC's development and construction lasted from 1943 to full operation at the end of 1945. The machine was huge, weighing 30 tons, using 200 kilowatts of electric power and contained over 18,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors.<ref name="Eniac">{{cite web|url=https://www.techiwarehouse.com/engine/a046ee08/Generations-of-Computer|title=Generations of Computer|access-date=11 August 2015|archive-url=https://web.archive.org/web/20150702211455/http://www.techiwarehouse.com/engine/a046ee08/Generations-of-Computer/|archive-date=2 July 2015|url-status=dead}}</ref> One of its major engineering feats was to minimize the effects of tube burnout, which was a common problem in machine reliability at that time. The machine was in almost constant use for the next ten years.

==Stored-program computer==
{{Main|Stored-program computer}}
{{Further|List of vacuum-tube computers}}

[[File:von Neumann architecture.svg|thumb|Design of the [[von Neumann architecture]], 1947]]

The theoretical basis for the stored-program computer was proposed by [[Alan Turing]] in his 1936 paper ''On Computable Numbers''.<ref name=Turing-1937-1938/> Whilst Turing was at [[Princeton University]] working on his PhD, [[John von Neumann]] got to know him and became intrigued by his concept of a universal computing machine.{{sfn|Copeland|2004|pp=21-22}}

Early computing machines executed the set sequence of steps, known as a '[[computer program|program]]', that could be altered by changing electrical connections using switches or a [[patch panel]] (or [[plugboard]]). However, this process of 'reprogramming' was often difficult and time-consuming, requiring engineers to create flowcharts and physically re-wire the machines.{{sfn|Copeland|2006|p=104}} Stored-program computers, by contrast, were designed to store a set of instructions (a [[computer program|program]]), in memory – typically the same memory as stored data.

[[ENIAC]] inventors [[John Mauchly]] and [[J. Presper Eckert]] proposed, in August 1944, the construction of a machine called the Electronic Discrete Variable Automatic Computer ([[EDVAC]]) and design work for it commenced at the [[University of Pennsylvania]]'s [[Moore School of Electrical Engineering]], before the ENIAC was fully operational.  The design implemented a number of important architectural and logical improvements conceived during the ENIAC's construction, and a high-speed [[Delay-line memory|serial-access memory]].<ref name=Wilkes>{{cite book | last=Wilkes | first=M. V. | author-link=Maurice Vincent Wilkes | title=Automatic Digital Computers | publisher=John Wiley & Sons | year=1956 | location=New York | pages=305 pages | id=QA76.W5 1956 }}</ref> However, Eckert and Mauchly left the project and its construction floundered.

In 1945, von Neumann visited the Moore School and wrote notes on what he saw, which he sent to the project. The U.S. Army liaison there had them typed and  circulated as the ''[[First Draft of a Report on the EDVAC]]''. The draft did not mention Eckert and Mauchly and, despite its incomplete nature and questionable lack of attribution of the sources of some of the ideas,<ref name="stanf"/> the computer architecture it outlined became known as the '[[von Neumann architecture]]'.

In 1945, Turing joined the [[National Physical Laboratory (United Kingdom)|UK National Physical Laboratory]] and began work on developing an electronic stored-program digital computer. His late-1945 report 'Proposed Electronic Calculator' was the first reasonably detailed specification for such a device. Turing presented a more detailed paper to the [[National Physical Laboratory, UK|National Physical Laboratory]] (NPL) Executive Committee in March 1946, giving the first substantially complete design of a [[stored-program computer]], a device that was called the [[Automatic Computing Engine]] (ACE).

Turing considered that the speed and the size of [[computer memory]] were crucial elements,<ref name=turing1945>{{cite report|url=https://www.npl.co.uk/getattachment/about-us/History/Famous-faces/Alan-Turing/turing-proposal-Alan-LR.pdf?lang=en-GB|title=Proposed Electronic Calculator|author=Alan Turing|date=1945|access-date=August 24, 2023}}</ref>{{rp|p.4}} so he proposed a high-speed memory of what would today be called 25 [[Kibibyte|KB]], accessed at a speed of 1 [[Hertz|MHz]]. The ACE implemented [[subroutine]] calls, whereas the EDVAC did not, and the ACE also used ''Abbreviated Computer Instructions,'' an early form of [[programming language]].

===Manchester Baby===
{{Main|Manchester Baby}}
[[File:SSEM Manchester museum close up.jpg|thumb|left|alt=Three tall racks containing electronic circuit boards|A section of the rebuilt [[Manchester Baby]], the first electronic stored-program computer]]
The [[Manchester Baby]] (Small Scale Experimental Machine, SSEM) was the world's first electronic [[stored-program computer]]. It was built at the [[Victoria University of Manchester]] by [[Frederic Calland Williams|Frederic C. Williams]], [[Tom Kilburn]] and Geoff Tootill, and ran its first program on 21&nbsp;June 1948.<ref>{{citation |last=Enticknap |first=Nicholas |title=Computing's Golden Jubilee |journal=Resurrection |issue=20 |publisher=The Computer Conservation Society |date=Summer 1998 |url=https://www.cs.man.ac.uk/CCS/res/res20.htm#d |issn=0958-7403 |access-date=19 April 2008 |url-status=dead |archive-url=https://web.archive.org/web/20120109142655/http://www.cs.man.ac.uk/CCS/res/res20.htm#d |archive-date=9 January 2012}}</ref>

The machine was not intended to be a practical computer but was instead designed as a [[testbed]] for the [[Williams tube]], the first [[random-access memory|random-access]] digital storage device.<ref>{{citation |title=Early computers at Manchester University |journal=Resurrection |volume=1 |issue=4 |publisher=The Computer Conservation Society |date=Summer 1992 |url=https://www.cs.man.ac.uk/CCS/res/res04.htm#g |issn=0958-7403 |access-date=7 July 2010 |archive-url=https://web.archive.org/web/20170828010743/http://www.cs.man.ac.uk/CCS/res/res04.htm#g |archive-date=28 August 2017 |url-status=dead}}</ref> Invented by [[Frederic Calland Williams|Freddie Williams]] and [[Tom Kilburn]]<ref>{{cite web |website=Computer 50 |url=https://www.computer50.org/mark1/notes.html |archive-url=https://web.archive.org/web/20130606122154/http://www.computer50.org/mark1/notes.html |archive-date=2013-06-06 |title=Why Williams-Kilburn Tube is a Better Name for the Williams Tube}}</ref><ref>{{Citation |last=Kilburn |first=Tom |author-link=Tom Kilburn |title=From Cathode Ray Tube to Ferranti Mark I |journal=Resurrection |publisher=The Computer Conservation Society |volume=1 |issue=2 |year=1990 |url=https://www.cs.man.ac.uk/CCS/res/res02.htm#e |issn=0958-7403 |access-date=15 March 2012 |archive-date=2020-06-27 |archive-url=https://web.archive.org/web/20200627165410/http://www.cs.man.ac.uk/CCS/res/res02.htm#e |url-status=live }}</ref> at the University of Manchester in 1946 and 1947, it was a [[cathode-ray tube]] that used an effect called [[secondary emission]] to temporarily store electronic [[binary data]], and was used successfully in several early computers.

Described as small and primitive in a 1998 retrospective, the Baby was the first working machine to contain all of the elements essential to a modern electronic computer.<ref name=EarlyComputers /> As soon as it had demonstrated the feasibility of its design, a project was initiated at the university to develop the design into a more usable computer, the [[Manchester Mark 1]]. The Mark 1 in turn quickly became the prototype for the [[Ferranti Mark 1]], the world's first commercially available general-purpose computer.<ref name=NapperMK1>{{citation |last=Napper |first=R. B. E. |title=Introduction to the Mark 1 |website=Computer 50 |url=https://www.computer50.org/mark1/mark1intro.html |publisher=The University of Manchester |access-date=4 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081026080604/http://www.computer50.org/mark1/mark1intro.html |archive-date=26 October 2008 }}</ref>

The Baby had a [[32-bit computing|32-bit]] [[word (data type)|word]] length and a [[computer memory|memory]] of 32&nbsp;words. As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in [[Computer hardware|hardware]] were [[subtraction]] and [[negation]]; other arithmetic operations were implemented in software. The first of three programs written for the machine found the highest [[proper divisor]] of 2<sup>18</sup> (262,144), a calculation that was known would take a long time to run—and so prove the computer's reliability—by testing every integer from 2<sup>18</sup>&nbsp;−&nbsp;1 downwards, as division was implemented by repeated subtraction of the divisor. The program consisted of 17&nbsp;instructions and ran for 52&nbsp;minutes before reaching the correct answer of 131,072, after the Baby had performed 3.5&nbsp;million operations (for an effective CPU speed of 1.1 [[instructions per second|kIPS]]). The successive approximations to the answer were displayed as a pattern of dots on the output [[cathode-ray tube|CRT]] which mirrored the pattern held on the Williams tube used for storage.

===Manchester Mark 1===
The SSEM led to the development of the [[Manchester Mark 1]] at the University of Manchester.{{sfn|Lavington|1998|p=20}} Work began in August 1948, and the first version was operational by April 1949; a program written to search for [[Mersenne prime]]s ran error-free for nine hours on the night of 16/17 June 1949. The machine's successful operation was widely reported in the British press, which used the phrase "electronic brain" in describing it to their readers.

The computer is especially historically significant because of its pioneering inclusion of [[index register]]s, an innovation which made it easier for a program to read sequentially through an array of [[Word (data type)|words]] in memory. Thirty-four patents resulted from the machine's development, and many of the ideas behind its design were incorporated in subsequent commercial products such as the {{nowrap|[[IBM 701]]}} and [[IBM 702|702]] as well as the Ferranti Mark 1. The chief designers, [[Frederic Calland Williams|Frederic C. Williams]] and [[Tom Kilburn]], concluded from their experiences with the Mark&nbsp;1 that computers would be used more in scientific roles than in pure mathematics. In 1951 they started development work on [[Meg (computer)|Meg]], the Mark&nbsp;1's successor, which would include a [[floating-point unit]].

===EDSAC===
[[File:EDSAC (19).jpg|right|thumb|EDSAC]]
The other contender for being the first recognizably modern digital stored-program computer<ref>{{cite web |first=Mark |last=Ward |date=13 January 2011 |work=BBC News |title=Pioneering Edsac computer to be built at Bletchley Park |url=https://www.bbc.co.uk/news/technology-12181153 |access-date=2018-06-21 |archive-date=2018-06-20 |archive-url=https://web.archive.org/web/20180620162103/https://www.bbc.co.uk/news/technology-12181153 |url-status=live }}</ref> was the [[EDSAC]],<ref>{{cite journal |last1=Wilkes |first1=W. V. |author-link=Maurice Wilkes |last2=Renwick |first2=W. |title=The EDSAC (Electronic delay storage automatic calculator) |journal=Math. Comp. |year=1950 |volume=4 |issue=30 |pages=61–65 |doi=10.1090/s0025-5718-1950-0037589-7|doi-access=free }}</ref> designed and constructed by [[Maurice Wilkes]] and his team at the [[University of Cambridge Mathematical Laboratory]] in [[England]] at the [[University of Cambridge]] in 1949. The machine was inspired by [[John von Neumann]]'s seminal ''[[First Draft of a Report on the EDVAC]]'' and was one of the first usefully operational electronic digital [[Von Neumann architecture|stored-program]] computers.{{efn|The Manchester Baby predated EDSAC as a [[stored-program computer]], but was built as a test bed for the [[Williams tube]] and not as a machine for practical use.<ref>{{cite web |title=A brief informal history of the Computer Laboratory |work=EDSAC 99 |url=https://www.cl.cam.ac.uk/events/EDSAC99/history.html |access-date=2020-12-01 |publisher=University of Cambridge Computer Laboratory |archive-url=https://web.archive.org/web/20130506195233/http://www.cl.cam.ac.uk/events/EDSAC99/history.html |archive-date=2013-05-06 |url-status=live}}</ref> However, the Manchester Mark 1 of 1949 (not to be confused with the 1948 prototype, the Baby) was available for university research in April 1949 despite being still under development.<ref>{{cite web |title=The Manchester Mark 1 |website=Computer 50 |url=https://www.computer50.org/mark1/MM1.html |access-date=2014-01-05 |url-status=dead |archive-url=https://web.archive.org/web/20140209155638/http://www.computer50.org/mark1/MM1.html |archive-date=2014-02-09}}</ref>}}

EDSAC ran its first programs on 6&nbsp;May 1949, when it calculated a table of squares<ref>{{cite journal|title=Pioneer computer to be rebuilt|journal=Cam|volume=62|date=2011|page=5}} To be precise, EDSAC's first program printed a list of the [[square number|square]]s of the [[integer (computer science)|integer]]s from 0 to 99 inclusive.</ref> and a list of [[prime number]]s.The EDSAC also served as the basis for the first commercially applied computer, the [[LEO (computer)|LEO I]], used by food manufacturing company [[J. Lyons and Co.|J. Lyons & Co. Ltd.]]  EDSAC 1 was finally shut down on 11 July 1958, having been superseded by EDSAC 2 which stayed in use until 1965.<ref>{{citation |title=EDSAC 99: 15–16 April 1999 |publisher=University of Cambridge Computer Laboratory |date=1999-05-06 |pages=68–69 |url=https://www.cl.cam.ac.uk/events/EDSAC99/booklet.pdf |access-date=2013-06-29 |archive-date=2020-09-26 |archive-url=https://web.archive.org/web/20200926061030/https://www.cl.cam.ac.uk/events/EDSAC99/booklet.pdf |url-status=live }}</ref>

{{blockquote|The "brain" [computer] may one day come down to our level [of the common people] and help with our income-tax and book-keeping calculations. But this is speculation and there is no sign of it so far.|British newspaper ''The Star'' in a June 1949 news article about the [[EDSAC]] computer, long before the era of the personal computers.<ref>{{Cite web |first=Martin |last=Campbell-Kelly |date=July 2001 |title=Tutorial Guide to the EDSAC Simulator |publisher=Department of Computer Science, University of Warwick |url=https://www.dcs.warwick.ac.uk/~edsac/Software/EdsacTG.pdf |access-date=2016-11-18 |archive-url=https://web.archive.org/web/20151222132057/http://www.dcs.warwick.ac.uk/~edsac/Software/EdsacTG.pdf |archive-date=2015-12-22 |url-status=dead }}<br/>{{*}}{{Cite web |date=March 2018 |title=Tutorial Guide to the EDSAC Simulator |publisher=The EDSAC Replica Project, The National Museum of Computing |url=https://www.dcs.warwick.ac.uk/~edsac/Software/EdsacTG.pdf |access-date=2020-12-02 |archive-date=2015-12-22 |archive-url=https://web.archive.org/web/20151222132057/http://www.dcs.warwick.ac.uk/~edsac/Software/EdsacTG.pdf |url-status=live }}</ref>}}

===EDVAC===
[[File:Edvac.jpg|right|thumb|upright|EDVAC]]
[[ENIAC]] inventors [[John Mauchly]] and [[J. Presper Eckert]] proposed the [[EDVAC]]'s construction in August 1944, and design work for the EDVAC commenced at the [[University of Pennsylvania]]'s [[Moore School of Electrical Engineering]], before the [[ENIAC]] was fully operational.  The design implemented a number of important architectural and logical improvements conceived during the ENIAC's construction, and a high-speed [[Delay-line memory|serial-access memory]].<ref name="Wilkes" /> However, Eckert and Mauchly left the project and its construction floundered.

It was finally delivered to the [[United States Army|U.S. Army]]'s [[Ballistics Research Laboratory]] at the [[Aberdeen Proving Ground]] in August 1949, but due to a number of problems, the computer only began operation in 1951, and then only on a limited basis.

===Commercial computers===
The first commercial electronic computer was the [[Ferranti Mark 1]], built by [[Ferranti]] and delivered to the [[University of Manchester]] in February 1951. It was based on the [[Manchester Mark 1]]. The main improvements over the Manchester Mark 1 were in the size of the [[primary storage]] (using [[Random-access memory|random access]] [[Williams tubes]]), [[secondary storage]] (using a [[drum memory|magnetic drum]]), a faster multiplier, and additional instructions. The basic cycle time was 1.2 milliseconds, and a multiplication could be completed in about 2.16 milliseconds. The multiplier used almost a quarter of the machine's 4,050 vacuum tubes (valves).{{sfn|Lavington|1998|p=25}} A second machine was purchased by the [[University of Toronto]], before the design was revised into the [[Ferranti Mark 1#Mark 1 Star|Mark 1 Star]]. At least seven of these later machines were delivered between 1953 and 1957, one of them to [[Royal Dutch Shell|Shell]] labs in Amsterdam.<ref>{{Citation |publisher=Computer Conservation Society |title=Our Computer Heritage Pilot Study: Deliveries of Ferranti Mark I and Mark I Star computers. |url=https://www.ourcomputerheritage.org/wp/ |archive-url=https://web.archive.org/web/20161211201840/http://www.ourcomputerheritage.org/wp/ |url-status=dead |archive-date=11 December 2016 |access-date=9 January 2010 }}</ref>

In October 1947, the directors of [[J. Lyons and Co.|J. Lyons & Company]], a British catering company famous for its teashops but with strong interests in new office management techniques, decided to take an active role in promoting the commercial development of computers. The [[LEO computer|LEO I]] computer (Lyons Electronic Office) became operational in April 1951<ref>{{cite web | last = Lavington | first = Simon | title = A brief history of British computers: the first 25 years (1948–1973). | publisher = [[British Computer Society]] | url = http://www.bcs.org/server.php? | access-date = 10 January 2010 | archive-date = 2010-07-05 | archive-url = https://web.archive.org/web/20100705050757/http://www.bcs.org/server.php | url-status = dead }}</ref> and ran the world's first regular routine office computer [[job (software)|job]]. On 17 November 1951, the J. Lyons company began weekly operation of a bakery valuations job on the LEO – the first business [[:Category:Application software|application]] to go live on a stored-program computer.{{efn|{{harvnb|Martin|2008|p=24}} notes that [[David Caminer]] (1915–2008) served as the first corporate electronic systems analyst, for this first business computer system. LEO would calculate an employee's pay, handle billing, and other office automation tasks.}}

In June 1951, the [[UNIVAC I]] (Universal Automatic Computer) was delivered to the [[United States Census Bureau|U.S. Census Bureau]]. Remington Rand eventually sold 46 machines at more than {{US$|1 million}} each (${{Formatprice|{{Inflation|US|1000000|1951|r=-4}}|0}} as of {{inflation/year|US}}).{{Inflation-fn|US}} UNIVAC was the first "mass-produced" computer. It used 5,200 vacuum tubes and consumed {{val|125|ul=kW}} of power. Its primary storage was [[Sequential access|serial-access]] mercury delay lines capable of storing 1,000 words of 11 decimal digits plus sign (72-bit words).

In 1952, [[Groupe Bull|Compagnie des Machines Bull]] released the [[Bull Gamma 3|Gamma 3]] computer, which became a large success in Europe, eventually selling more than 1,200 units, and the first computer produced in more than 1,000 units.<ref name=":1">{{Cite journal |last=Leclerc |first=Bruno |date=January 1990 |title=From Gamma 2 to Gamma E.T.: The Birth of Electronic Computing at Bull |journal=Annals of the History of Computing |volume=12 |issue=1 |pages=5–22 |doi=10.1109/MAHC.1990.10010 |bibcode=1990IAHC...12a...5L |s2cid=15227017 |issn=0164-1239}}</ref> The Gamma 3 had innovative features for its time including a dual-mode, software switchable, BCD and binary ALU, as well as a hardwired floating-point library for scientific computing.<ref name=":1" /> In its E.T configuration, the Gamma 3 drum memory could fit about 50,000 instructions for a capacity of 16,384 words (around 100&nbsp;kB), a large amount for the time.<ref name=":1" />

[[File:IBM-650-panel.jpg|thumb|right|Front panel of the [[IBM 650]] ]]
Compared to the UNIVAC, IBM introduced a smaller, more affordable computer in 1954 that proved very popular.{{efn|For example, Kara Platoni's article on [[Donald Knuth]] stated that "there was something special about the IBM 650".<ref>{{cite magazine |first=Kara |last=Platoni |title=Love at First Byte |magazine=Stanford Magazine |url=https://www.stanfordalumni.org/news/magazine/2006/mayjun/features/knuth.html |date=May–June 2006 |archive-url= https://web.archive.org/web/20060925022700/http://www.stanfordalumni.org/news/magazine/2006/mayjun/features/knuth.html |archive-date=2006-09-25 |url-status=dead}}</ref>}}<ref>
V. M. Wolontis (18 August 1955) "A Complete Floating-Decimal Interpretive System for the I.B.M. 650 Magnetic Drum Calculator—Case 20878" Bell Telephone Laboratories Technical Memorandum MM-114-37, Reported in IBM Technical Newsletter No. 11, March 1956, as referenced in {{cite journal |title=Wolontis-Bell Interpreter |publisher=IEEE |journal=Annals of the History of Computing |volume=8 |issue=1 |date=January–March 1986 |pages=74–76 |doi=10.1109/MAHC.1986.10008 |bibcode=1986IAHC....8a..74. |s2cid=36692260}}
</ref> The [[IBM 650]] weighed over {{val|900|u=kg}}, the attached power supply weighed around {{val|1350|u=kg}} and both were held in separate cabinets of roughly 1.5{{times}}0.9{{times}}{{val|1.8|u=meters}}. The system cost {{US$|500000}}<ref>{{cite book |last=Dudley |first=Leonard |title=Information Revolution in the History of the West |year=2008 |url= https://books.google.com/books?id=jLnPi5aYoJUC&pg=PA266 |isbn=978-1-84720-790-6 |publisher=Edward Elgar Publishing |page=266 |access-date=2020-08-30}}</ref> (${{Formatprice|{{Inflation|US|500000|1954|r=-4}}|0}} as of {{inflation/year|US}}) or could be leased for {{US$|3500}} a month (${{Formatprice|{{Inflation|US|3500|1954|r=-4}}|0}} as of {{inflation/year|US}}).{{Inflation-fn|US}} Its drum memory was originally 2,000 ten-digit words, later expanded to 4,000 words. Memory limitations such as this were to dominate programming for decades afterward.  The program instructions were fetched from the spinning drum as the code ran. Efficient execution using drum memory was provided by a combination of hardware architecture – the instruction format included the address of the next instruction – and software: the [[Symbolic Optimal Assembly Program]], SOAP,<ref>{{Citation |last=IBM |title=SOAP II for the IBM 650 |year=1957 |id=C24-4000-0 |url= http://www.bitsavers.org/pdf/ibm/650/24-4000-0_SOAPII.pdf |access-date=2009-05-25 |archive-date=2009-09-20 |archive-url=https://web.archive.org/web/20090920081523/http://www.bitsavers.org/pdf/ibm/650/24-4000-0_SOAPII.pdf |url-status=live}}</ref> assigned instructions to the optimal addresses (to the extent possible by static analysis of the source program). Thus many instructions were, when needed, located in the next row of the drum to be read and additional wait time for drum rotation was reduced.

===Microprogramming===
In 1951, British scientist [[Maurice Wilkes]] developed the concept of [[microcode|microprogramming]] from the realisation that the [[central processing unit]] of a computer could be controlled by a miniature, highly specialized [[computer program]] in high-speed [[Read-only memory|ROM]]. Microprogramming allows the base instruction set to be defined or extended by built-in programs (now called [[firmware]] or [[microcode]]).{{sfn|Horowitz|Hill|1989|p=743}} This concept greatly simplified CPU development. He first described this at the [[University of Manchester]] Computer Inaugural Conference in 1951, then published in expanded form in ''[[IEEE Spectrum]]'' in 1955.{{citation needed|date=April 2013}}

It was widely used in the CPUs and [[floating-point]] units of [[mainframe computer|mainframe]] and other computers; it was implemented for the first time in [[EDSAC 2]],<ref name="edsac2">{{Cite journal |last1=Wilkes |first1=M. V. |author-link1=Maurice Wilkes| title=Edsac 2 |doi=10.1109/85.194055 |journal=IEEE Annals of the History of Computing| volume=14 |issue=4 |pages=49–56 |year=1992 |bibcode=1992IAHC...14d..49W |s2cid=11377060}}</ref> which also used multiple identical "bit slices" to simplify design. Interchangeable, replaceable tube assemblies were used for each bit of the processor.{{efn|The microcode was implemented as ''extracode'' on Atlas.<ref>{{cite web |title=The Atlas Supervisor |author1=T. Kilburn |author2=R. B. Payne |author3=D. J. Howarth |year=1962 |work=Atlas Computer |url=https://www.chilton-computing.org.uk/acl/technology/atlas/p019.htm |access-date=2010-02-09 |archive-date=2009-12-31 |archive-url=https://web.archive.org/web/20091231062425/http://www.chilton-computing.org.uk/acl/technology/atlas/p019.htm |url-status=live }}</ref>}}

==Magnetic memory==
[[File:Coincident-current magnetic core.svg|thumb|right|Diagram of a 4×4 plane of [[magnetic-core memory]] in an X/Y line coincident-current setup. X and Y are drive lines, S is sense, Z is inhibit. Arrows indicate the direction of current for writing.]]
Magnetic [[drum memory|drum memories]] were developed for the US Navy during WW II with the work continuing at [[Engineering Research Associates]] (ERA) in 1946 and 1947. ERA, then a part of Univac included a drum memory in its [[UNIVAC 1103|1103]], announced in February 1953. The first mass-produced computer, the [[IBM 650]], also announced in 1953 had about 8.5 kilobytes of drum memory.

[[Magnetic core|Magnetic-core]] memory patented in 1949<ref>{{Cite patent |country=US |number=2708722 |title=Pulse transfer controlling device |fdate=1949-10-21 |gdate=1955-05-17 |invent1=Wang |inventor1-first=An |inventorlink=An Wang}}</ref> with its first usage demonstrated for the [[Whirlwind I#The memory subsystem|Whirlwind computer]] in August 1953.<ref>{{Cite web |title=1953: Whirlwind computer debuts core memory |url=https://www.computerhistory.org/storageengine/whirlwind-computer-debuts-core-memory/ |url-status=live |archive-url=https://web.archive.org/web/20180508121757/http://www.computerhistory.org/storageengine/whirlwind-computer-debuts-core-memory/ |archive-date=2018-05-08 |access-date=2023-08-26 |website=[[Computer History Museum]]}}</ref> Commercialization followed quickly. Magnetic core was used in peripherals of the IBM 702 delivered in July 1955, and later in the 702 itself. The [[IBM 704]] (1955) and the Ferranti Mercury (1957) used magnetic-core memory. It went on to dominate the field into the 1970s, when it was replaced with semiconductor memory.  Magnetic core peaked in volume about 1975 and declined in usage and market share thereafter.<ref>{{cite magazine |url=https://books.google.com/books?id=paExEmGMXlAC&pg=PA419 |title=Takeover in the memory market |author=N. Valery |magazine=New Scientist |date=21 August 1975 |pages=419–421 |access-date=2019-01-22 |url-status=live |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181645/https://books.google.com/books?id=paExEmGMXlAC&pg=PA419}}</ref>

As late as 1980, PDP-11/45 machines using magnetic-core main memory and drums for swapping were still in use at many of the original UNIX sites.

==Early digital computer characteristics==
{{Further|Analytical Engine#Comparison to other early computers}}
{| class="wikitable" style="margin-left:auto; margin-right:auto;"
|+Defining characteristics of some early digital computers of the 1940s {{Small|(In the history of computing hardware)}}
|-
! Name !! First operational !! Numeral system !! Computing mechanism !! [[Computer program|Programming]] !! [[Turing completeness|Turing-complete]]
|-
|{{rh}}| Arthur H. Dickinson [[IBM]] {{small|(US)}} ||style="text-align:right;" | Jan 1940 || [[Decimal]]|| [[Electronics|Electronic]] || {{No2|Not}} programmable || {{No}}
|-
|{{rh}}| [[Joseph Desch]] [[NCR Corporation|NCR]] {{small|(US)}} ||style="text-align:right;" | March 1940 || [[Decimal]] || [[Electronics|Electronic]] || {{No2|Not}} programmable || {{No}}
|-
|{{rh}}| [[Konrad Zuse|Zuse]] [[Z3 (computer)|Z3]] {{small|(Germany)}} ||style="text-align:right;" | May 1941 || [[Binary number|Binary]] [[floating-point arithmetic|floating point]] || [[Electromechanics|Electro-mechanical]] || Program-controlled by punched {{val|35|u=mm}} [[film stock]] (but no conditional branch) || In theory {{small|([[Z3 (computer)#Z3 as a universal Turing machine|1998]])}}
|-
|{{rh}}| [[Atanasoff–Berry Computer]] {{small|(US)}} ||style="text-align:right;" | 1942|| Binary || [[Electronics|Electronic]] || {{No2|Not}} programmable — single purpose || {{No}}
|-
|{{rh}}| [[Colossus computer|Colossus]] Mark 1 {{small|(UK)}} ||style="text-align:right;" | Feb 1944 || Binary || Electronic || Program-controlled by patch cables and switches || {{No|[[Colossus computer#Influence and fate|No]]}}
|-
|{{rh}}| [[Harvard Mark I|Harvard Mark I – IBM ASCC]] {{small|(US)}} || style="text-align:right;" |May 1944 || [[Decimal]] || Electro-mechanical || Program-controlled by 24-channel [[punched tape|punched paper tape]] (but no conditional branch) || Debatable
|-
|{{rh}}| [[Colossus computer|Colossus]] Mark 2 {{small|(UK)}} || style="text-align:right;" |June 1944 || Binary || Electronic || Program-controlled by patch cables and switches || Conjectured<ref name="Wells pp. 1383–1405">{{cite journal | last=Wells | first=Benjamin | title=Unwinding performance and power on Colossus, an unconventional computer | journal=Natural Computing | publisher=Springer Science and Business Media LLC | volume=10 | issue=4 | date=2010-11-18 | issn=1567-7818 | doi=10.1007/s11047-010-9225-x | pages=1383–1405| s2cid=7492074 }}</ref>
|-
|{{rh}}| Zuse [[Z4 (computer)|Z4]] {{small|(Germany)}} ||style="text-align:right;" | March 1945 || Binary floating point <!-- for sure? "Numbers were entered and output as decimal floating-point even though the internal working was in binary" --> || Electro-mechanical || Program-controlled by punched {{val|35|u=mm}} film stock || [[Z4 (computer)#Construction|In 1950]]
|-
|{{rh}}| [[ENIAC]] {{small|(US)}} || style="text-align:right;" | <!-- "Feb 1946", no? "completed in 1945 and first put to work for practical purposes on December 10, 1945" --> December 1945 || Decimal || Electronic || Program-controlled by patch cables and switches || {{Yes}}
|-
|{{rh}}| [[ENIAC|Modified ENIAC]] {{small|(US)}} ||style="text-align:right;white-space:nowrap;" | April 1948 || Decimal || Electronic || Read-only stored-programming mechanism using the Function Tables as program [[read-only memory|ROM]] || {{Yes}}
|-
|{{rh}}| [[APEXC|ARC2 (SEC)]] {{small|(UK)}} ||style="text-align:right;" | May 1948 || Binary || Electronic || [[Stored-program computer|Stored-program]] in [[drum memory|rotating drum memory]] || {{Yes}}
|-
|{{rh}}| [[Manchester Baby]] {{small|(UK)}} ||style="text-align:right;" | June 1948 || Binary || Electronic || [[Stored-program computer|Stored-program]] in [[Williams tube|Williams cathode-ray tube memory]] || {{Yes}}
|-
|{{rh}}| [[Manchester Mark 1]] {{small|(UK)}} || style="text-align:right;" |April 1949 || Binary || Electronic || Stored-program in Williams cathode-ray tube memory and [[Drum memory|magnetic drum]] memory|| {{Yes}}
|-
|{{rh}}| [[EDSAC]] {{small|(UK)}} ||style="text-align:right;" | May 1949 ||Binary || Electronic || Stored-program in mercury [[delay-line memory]] || {{Yes}}
|-
|{{rh}}| [[CSIRAC]] {{small|(Australia)}} || style="text-align:right;" | Nov 1949 || Binary || Electronic || Stored-program in mercury delay-line memory || {{Yes}}
|}

==Transistor computers==
{{Main|Transistor computer}}
{{Further|List of transistorized computers}}
[[File:Transistor-die-KSY34.jpg|thumb|left|A [[bipolar junction transistor]] ]]
The bipolar [[transistor]] was invented in 1947. From 1955 onward transistors replaced [[vacuum tube]]s in computer designs,{{sfn|Feynman|Leighton|Sands|1966|pp=14–11 to 14–12}} giving rise to the "second generation" of computers. Compared to vacuum tubes, transistors have many advantages: they are smaller, and require less power than vacuum tubes, so give off less heat. Silicon junction transistors were much more reliable than vacuum tubes and had longer service life. Transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space. Transistors greatly reduced computers' size, initial cost, and [[operating cost]]. Typically, second-generation computers were composed of large numbers of [[printed circuit board]]s such as the [[Standard Modular System|IBM Standard Modular System]],{{sfn|IBM|1960}} each carrying one to four [[logic gate]]s or [[Flip-flop (electronics)|flip-flops]].

At the [[University of Manchester]], a team under the leadership of [[Tom Kilburn]] designed and built a machine using the newly developed [[transistor]]s instead of valves (vacuum tubes). Initially the only devices available were [[germanium]] [[point-contact transistor]]s, less reliable than the valves they replaced but which consumed far less power.{{sfn|Lavington|1998|pp=34–35}} Their first [[transistor computer|transistorized computer]], and the first in the world, was [[Manchester computers#Transistor Computer|operational by 1953]],{{sfn|Lavington|1998|p=37}} and a second version was completed there in April 1955.{{sfn|Lavington|1998|p=37}} The 1955 version used 200 transistors, 1,300 [[Solid-state electronics|solid-state]] [[diode]]s, and had a power consumption of 150 watts. However, the machine did make use of valves to generate its 125&nbsp;kHz clock waveforms and in the circuitry to read and write on its magnetic drum memory, so it was not the first completely transistorized computer.

That distinction goes to the [[Harwell CADET]] of 1955,<ref name="ieeexplore.ieee"/> built by the electronics division of the [[Atomic Energy Research Establishment]] at [[Harwell, Oxfordshire|Harwell]]. The design featured a 64-kilobyte magnetic drum memory store with multiple moving heads that had been designed at the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory, UK]]. By 1953 this team had transistor circuits operating to read and write on a smaller magnetic drum from the [[Royal Radar Establishment]]. The machine used a low clock speed of only 58&nbsp;kHz to avoid having to use any valves to generate the clock waveforms.<ref>{{cite book |last=Cooke-Yarborough |first=E.H. |title=Introduction to Transistor Circuits |publisher=Oliver and Boyd |year=1957 |location=Edinburgh}}</ref><ref name="ieeexplore.ieee">{{cite journal| title=Some early transistor applications in the UK| journal=Engineering Science & Education Journal| volume=7| issue=3| pages=100–106| year=1998| last1=Cooke-Yarborough| first1=E.H.| doi=10.1049/esej:19980301| doi-broken-date=12 July 2025}}</ref>

CADET used 324-point-contact transistors provided by the UK company [[Standard Telephones and Cables]]; 76 [[Bipolar junction transistor|junction transistor]]s were used for the first stage amplifiers for data read from the drum, since point-contact transistors were too noisy. From August 1956, CADET was offering a regular computing service, during which it often executed continuous computing runs of 80 hours or more.<ref>{{cite book |last=Lavington |first=Simon |title=Early British Computers |publisher=Manchester University Press |year=1980 |url=https://ed-thelen.org/comp-hist/EarlyBritish-05-12.html#Ch-09 |isbn=0-7190-0803-4 |access-date=2014-01-07 |archive-date=2019-05-24 |archive-url=https://web.archive.org/web/20190524164254/http://ed-thelen.org/comp-hist/EarlyBritish-05-12.html#Ch-09 |url-status=live }}</ref><ref>{{Cite journal |doi= 10.1049/pi-b-1.1956.0076 |title=A transistor digital computer |journal=Proceedings of the IEE - Part B: Radio and Electronic Engineering |volume=103 |issue=3S |pages=364–370 |year=1956 |last1=Cooke-Yarborough |first1=E.H. |last2= Barnes |first2=R.C.M. |last3=Stephen |first3=J.H. |last4=Howells |first4=G.A.}}</ref> Problems with the reliability of early batches of point contact and alloyed junction transistors meant that the machine's [[mean time between failures]] was about 90&nbsp;minutes, but this improved once the more reliable [[bipolar junction transistor]]s became available.{{sfn|Lavington|1998|pp=36–37}}

The Manchester University Transistor Computer's design was adopted by the local engineering firm of [[Metropolitan-Vickers]] in their [[Metrovick 950]], the first commercial transistor computer anywhere.<ref>{{cite web |title=Metrovick |website=Exposuremeters.net |url= http://www.myphotoweb.com/expmeters/pages/metrovick.htm |url-status=dead |archive-date=2014-01-07 |archive-url=https://web.archive.org/web/20140107164654/http://www.myphotoweb.com/expmeters/pages/metrovick.htm}}</ref> Six Metrovick 950s were built, the first completed in 1956. They were successfully deployed within various departments of the company and were in use for about five years.{{sfn|Lavington|1998|p=37}} A second generation computer, the [[IBM 1401]], captured about one third of the world market. IBM installed more than ten thousand 1401s between 1960 and 1964.

===Transistor peripherals===
Transistorized electronics improved not only the CPU (Central Processing Unit), but also the [[peripheral|peripheral devices]]. The second generation [[disk storage|disk data storage units]] were able to store tens of millions of letters and digits.  Next to the [[fixed disk]] storage units, connected to the CPU via high-speed data transmission, were removable disk data storage units. A removable [[disk pack]] can be easily exchanged with another pack in a few seconds. Even if the removable disks' capacity is smaller than fixed disks, their interchangeability guarantees a nearly unlimited quantity of data close at hand. [[Magnetic-tape data storage|Magnetic tape]] provided archival capability for this data, at a lower cost than disk.

Many second-generation CPUs delegated peripheral device communications to a secondary processor. For example, while the communication processor controlled [[Unit record equipment|card reading and punching]], the main CPU executed calculations and binary [[branch (computer science)|branch instructions]]. One [[Bus (computing)|databus]] would bear data between the main CPU and core memory at the CPU's [[fetch-execute cycle]] rate, and other databusses would typically serve the peripheral devices. On the [[PDP-1]], the core memory's cycle time was 5 microseconds; consequently most arithmetic instructions took 10 microseconds (100,000 operations per second) because most operations took at least two memory cycles; one for the instruction, one for the [[operand]] data fetch.

During the second generation [[Remote Digital Terminal|remote terminal]] units (often in the form of [[Teleprinter]]s like a [[Friden Flexowriter]]) saw greatly increased use.{{efn|[[Allen Newell]] used remote terminals to communicate cross-country with the [[RAND]] computers.{{sfn|Simon|1991}}}} Telephone connections provided sufficient speed for early remote terminals and allowed hundreds of kilometers separation between remote-terminals and the computing center. Eventually these stand-alone computer networks would be generalized into an interconnected ''[[history of the Internet|network of networks]]''—the Internet.{{efn|[[Robert Taylor (computer scientist)|Bob Taylor]] conceived of a generalized protocol to link together multiple networks to be viewed as a single session regardless of the specific network: "Wait a minute. Why not just have one terminal, and it connects to anything you want it to be connected to? And, hence, the Arpanet was born."{{sfn|Mayo|Newcomb|2008}}}}

===Transistor supercomputers===
[[File:University of Manchester Atlas, January 1963.JPG|thumb|The University of Manchester Atlas in January 1963]]
The early 1960s saw the advent of [[Supercomputer|supercomputing]]. The [[Atlas (computer)|Atlas]] was a joint development between the [[Victoria University of Manchester|University of Manchester]], [[Ferranti]], and [[Plessey]], and was first installed at Manchester University and officially commissioned in 1962 as one of the world's first [[supercomputer]]s – considered to be the most powerful computer in the world at that time.{{sfn|Lavington|1998|p=41}} It was said that whenever Atlas went offline half of the United Kingdom's computer capacity was lost.{{sfn|Lavington|1998|pp=44–45}} It was a second-generation machine, using [[Discrete device|discrete]] [[Bipolar junction transistor#Germanium transistors|germanium]] [[transistor]]s. Atlas also pioneered the [[Atlas Supervisor]], "considered by many to be the first recognisable modern [[operating system]]".{{sfn|Lavington|1998|pp=50–52}}

In the US, a series of computers at [[Control Data Corporation]] (CDC) were designed by [[Seymour Cray]] to use innovative designs and parallelism to achieve superior computational peak performance.<ref name=chen>{{cite book |title=Hardware software co-design of a multimedia SOC platform |author1=Sao-Jie Chen |author2=Guang-Huei Lin |author3=Pao-Ann Hsiung |author4=Yu-Hen Hu |year=2009 |pages=70–72}}</ref> The [[CDC 6600]], released in 1964, is generally considered the first supercomputer.<ref>{{cite book |title=History of computing in education |first1=John |last1=Impagliazzo |first2=John A. N. |last2=Lee |year=2004 |isbn=1-4020-8135-9 |page=172 |publisher=Springer |url= https://books.google.com/books?id=J46GinHakmkC&pg=PA172 |access-date=2016-06-04 |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181649/https://books.google.com/books?id=J46GinHakmkC&pg=PA172 |url-status=live}}</ref><ref>{{cite book |title=The American Midwest: an interpretive encyclopedia |first1=Richard |last1=Sisson |first2=Christian K. |last2=Zacher |year=2006 |isbn=0-253-34886-2 |page=1489 |url= https://books.google.com/books?id=n3Xn7jMx1RYC&pg=PA1489 |publisher=Indiana University Press |access-date=2016-06-04 |url-status=live |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181649/https://books.google.com/books?id=n3Xn7jMx1RYC&pg=PA1489}}</ref> The CDC 6600 outperformed its predecessor, the [[IBM 7030 Stretch]], by about a factor of 3. With performance of about 1&nbsp;[[FLOPS|megaFLOPS]], the CDC 6600 was the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the [[CDC 7600]].

==Integrated circuit computers==
{{main|History of computing hardware (1960s–present)#Third generation}}
The "third-generation" of digital electronic computers used [[integrated circuit]] (IC) chips as the basis of their logic.

The idea of an integrated circuit was conceived by a radar scientist working for the [[Royal Radar Establishment]] of the [[Ministry of Defence (United Kingdom)|Ministry of Defence]], [[Geoffrey Dummer|Geoffrey W.A. Dummer]].

The first working integrated circuits were invented by [[Jack Kilby]] at [[Texas Instruments]] and [[Robert Noyce]] at [[Fairchild Semiconductor]].{{sfn|Kilby|2000}} Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958.<ref name="TIJackBuilt">{{cite web |url=https://www.ti.com/corp/docs/kilbyctr/jackbuilt.shtml |title=The Chip that Jack Built |archive-url=https://web.archive.org/web/20170805081956/http://www.ti.com/corp/docs/kilbyctr/jackbuilt.shtml |archive-date=2017-08-05 |date=c. 2008 |publisher=Texas Instruments |access-date=29 May 2008}}</ref> Kilby's invention was a [[hybrid integrated circuit]] (hybrid IC).<ref name="Saxena140">{{cite book |last1=Saxena |first1=Arjun N. |title=Invention of Integrated Circuits: Untold Important Facts |date=2009 |publisher=[[World Scientific]] |isbn=9789812814456 |page=140 |url=https://books.google.com/books?id=-3lpDQAAQBAJ&pg=PA140 |access-date=2019-12-07 |url-status=live |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181650/https://books.google.com/books?id=-3lpDQAAQBAJ&pg=PA140}}</ref> It had external wire connections, which made it difficult to mass-produce.<ref name="nasa">{{cite web |title=Integrated circuits |website=[[NASA]] |url=https://www.hq.nasa.gov/alsj/ic-pg3.html |access-date=13 August 2019 |archive-date=2019-07-21 |archive-url=https://web.archive.org/web/20190721173218/https://www.hq.nasa.gov/alsj/ic-pg3.html |url-status=live}}</ref>

Noyce came up with his own idea of an integrated circuit half a year after Kilby.<ref>{{Cite patent |country=US |number=2981877 |title=Semiconductor device-and-lead structure |gdate=1961-04-25 |invent1=Noyce |inventor1-first=Robert |inventorlink=Robert Noyce|assign1=[[Fairchild Semiconductor Corporation]]}}</ref> Noyce's invention was a [[monolithic integrated circuit]] (IC) chip.<ref name="computerhistory1959">{{cite web |title=1959: Practical Monolithic Integrated Circuit Concept Patented |url=https://www.computerhistory.org/siliconengine/practical-monolithic-integrated-circuit-concept-patented/ |website=[[Computer History Museum]] |access-date=13 August 2019 |archive-date=2019-10-24 |archive-url=https://web.archive.org/web/20191024144046/https://www.computerhistory.org/siliconengine/practical-monolithic-integrated-circuit-concept-patented/ |url-status=live }}</ref><ref name="nasa"/> His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of [[silicon]], whereas Kilby's chip was made of [[germanium]]. The basis for Noyce's monolithic IC was Fairchild's [[planar process]], which allowed integrated circuits to be laid out using the same principles as those of [[printed circuit]]s. The planar process was developed by Noyce's colleague [[Jean Hoerni]] in early 1959, based on [[Mohamed M. Atalla]]'s work on semiconductor surface passivation by silicon dioxide at [[Bell Labs]] in the late 1950s.<ref name="Lojek120">{{cite book |last1=Lojek |first1=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=[[Springer Science & Business Media]] |isbn=9783540342588 |page=120}}</ref><ref>{{cite book |last1=Bassett |first1=Ross Knox |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |date=2007 |publisher=Johns Hopkins University Press |isbn=9780801886393 |page=46 |url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA46 |access-date=2019-12-07 |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181649/https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA46 |url-status=live }}</ref><ref>{{cite book |last1=Huff |first1=Howard R. |last2=Tsuya |first2=H. |last3=Gösele |first3=U. |title=Silicon Materials Science and Technology: Proceedings of the Eighth International Symposium on Silicon Materials Science and Technology |date=1998 |publisher=[[Electrochemical Society]] |pages=181–182 |isbn=9781566771931 |url=https://books.google.com/books?id=SnQfAQAAIAAJ&pg=PA181 |access-date=2019-12-07 |url-status=live |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202182712/https://books.google.com/books?id=SnQfAQAAIAAJ&pg=PA181}}</ref>

Third generation (integrated circuit) computers first appeared in the early 1960s in computers developed for government purposes, and then in commercial computers beginning in the mid-1960s.  The first silicon IC computer was the [[Apollo Guidance Computer]] or AGC.<ref name= ceruzzi>{{cite web |title=Apollo Guidance Computer and the First Silicon Chips |last=Ceruzzi |first=Paul |date=2015 |website=SmithsonianNational Air and Space Museum |url=https://airandspace.si.edu/stories/editorial/apollo-guidance-computer-and-first-silicon-chips |access-date=2021-05-12 |url-status=live |archive-date=2021-05-22 |archive-url=https://web.archive.org/web/20210522064136/https://airandspace.si.edu/stories/editorial/apollo-guidance-computer-and-first-silicon-chips}}</ref> Although not the most powerful computer of its time, the extreme constraints on size, mass, and power of the Apollo spacecraft required the AGC to be much smaller and denser than any prior computer, weighing in at only {{convert|70|lb|kg}}. Each lunar landing mission carried two AGCs, one each in the command and lunar ascent modules.

==Semiconductor memory==
{{Main|Semiconductor memory}}

The [[MOSFET]] (metal–oxide–semiconductor field-effect transistor, or MOS transistor) was invented by [[Mohamed M. Atalla]] and [[Dawon Kahng]] at [[Bell Labs]] in 1959.<ref name="computerhistory">{{cite journal|title=1960 - Metal Oxide Semiconductor (MOS) Transistor Demonstrated |url=https://www.computerhistory.org/siliconengine/metal-oxide-semiconductor-mos-transistor-demonstrated/ |access-date=2019-10-21|journal=The Silicon Engine|publisher=[[Computer History Museum]]|archive-date=2019-10-27|archive-url=https://web.archive.org/web/20191027045554/https://www.computerhistory.org/siliconengine/metal-oxide-semiconductor-mos-transistor-demonstrated/|url-status=live}}</ref> In addition to data processing, the MOSFET enabled the practical use of MOS transistors as [[memory cell (computing)|memory cell]] storage elements, a function previously served by [[magnetic cores]]. [[Semiconductor memory]], also known as [[MOS memory]], was cheaper and consumed less power than [[magnetic-core memory]].<ref name="computerhistory1970">{{cite web |title=1970: MOS Dynamic RAM Competes with Magnetic Core Memory on Price |url=https://www.computerhistory.org/siliconengine/mos-dynamic-ram-competes-with-magnetic-core-memory-on-price/ |website=[[Computer History Museum]] |access-date=29 July 2019 |archive-date=2021-10-26 |archive-url=https://web.archive.org/web/20211026142915/https://www.computerhistory.org/siliconengine/mos-dynamic-ram-competes-with-magnetic-core-memory-on-price/ |url-status=live }}</ref> MOS [[random-access memory]] (RAM), in the form of [[static RAM]] (SRAM), was developed by John Schmidt at [[Fairchild Semiconductor]] in 1964.<ref name="computerhistory1970"/><ref>{{Cite book |url=https://books.google.com/books?id=kG4rAQAAIAAJ&q=John+Schmidt|title=Solid State Design - Vol. 6|date=1965|publisher=Horizon House|access-date=2020-10-18 |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202182713/https://books.google.com/books?id=kG4rAQAAIAAJ&q=John+Schmidt|url-status=live}}</ref> In 1966, [[Robert Dennard]] at the [[IBM Thomas J. Watson Research Center]] developed MOS [[dynamic RAM]] (DRAM).<ref name="ibm100">{{cite web |title=DRAM |website=IBM100 |publisher=[[IBM]] |url= https://www.ibm.com/ibm/history/ibm100/us/en/icons/dram/ |access-date=20 September 2019 |date=9 August 2017 |archive-url=https://web.archive.org/web/20190620014432/https://www.ibm.com/ibm/history/ibm100/us/en/icons/dram/ |archive-date=2019-06-20 |url-status=live}}</ref> In 1967, Dawon Kahng and [[Simon Sze]] at Bell Labs developed the [[floating-gate MOSFET]], the basis for MOS [[non-volatile memory]] such as [[EPROM]], [[EEPROM]] and [[flash memory]].<ref name="computerhistory1971">{{cite web |title=1971: Reusable semiconductor ROM introduced |url=https://www.computerhistory.org/storageengine/reusable-semiconductor-rom-introduced/ |website=[[Computer History Museum]] |access-date=19 June 2019 |archive-date=2019-10-03 |archive-url=https://web.archive.org/web/20191003063442/https://www.computerhistory.org/storageengine/reusable-semiconductor-rom-introduced/ |url-status=live }}</ref><ref name="economist">{{cite news |title=Not just a flash in the pan |url=https://www.economist.com/technology-quarterly/2006/03/11/not-just-a-flash-in-the-pan |newspaper=[[The Economist]] |date=11 March 2006 |access-date=10 September 2019 |archive-date=2019-09-25 |archive-url=https://web.archive.org/web/20190925021310/https://www.economist.com/technology-quarterly/2006/03/11/not-just-a-flash-in-the-pan |url-status=live }}</ref>

==Microprocessor computers==
{{Main|History of computing hardware (1960s–present)#Fourth generation}}
The "fourth-generation" of digital electronic computers used [[microprocessor]]s as the basis of their logic. The microprocessor has origins in the [[MOS integrated circuit]] (MOS IC) chip.<ref name="ieee">{{cite journal |last1=Shirriff |first1=Ken |title=The Surprising Story of the First Microprocessors |journal=[[IEEE Spectrum]] |volume=53 |issue=9 |pages=48–54 |date=30 August 2016 |publisher=[[Institute of Electrical and Electronics Engineers]] |url=https://spectrum.ieee.org/the-surprising-story-of-the-first-microprocessors |access-date=13 October 2019 |doi=10.1109/MSPEC.2016.7551353 |s2cid=32003640 |archive-date=2021-07-12 |archive-url=https://web.archive.org/web/20210712091202/https://spectrum.ieee.org/tech-history/silicon-revolution/the-surprising-story-of-the-first-microprocessors |url-status=live}}</ref> Due to rapid [[MOSFET scaling]], MOS IC chips rapidly increased in complexity at a rate predicted by [[Moore's law]], leading to [[large-scale integration]] (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips to [[computing]] was the basis for the first microprocessors, as engineers began recognizing that a complete [[computer processor]] could be contained on a single MOS LSI chip.<ref name="ieee"/>

The subject of exactly which device was the first microprocessor is contentious, partly due to lack of agreement on the exact definition of the term "microprocessor". The earliest multi-chip microprocessors were the [[Four-Phase Systems]] AL-1 in 1969 and [[Garrett AiResearch]] [[MP944]] in 1970, developed with multiple MOS LSI chips.<ref name="ieee"/> The first single-chip microprocessor was the [[Intel 4004]],{{sfn|Intel|1971}} developed on a single [[PMOS logic|PMOS]] LSI chip.<ref name="ieee"/> It was designed and realized by [[Marcian Hoff|Ted Hoff]], [[Federico Faggin]], [[Masatoshi Shima]] and [[Stanley Mazor]] at [[Intel]], and released in 1971.{{efn|The Intel 4004 (1971) die was 12&nbsp;mm<sup>2</sup>, composed of 2300 transistors; by comparison, the Pentium Pro was 306&nbsp;mm<sup>2</sup>, composed of 5.5 million transistors.{{sfn|Patterson|Hennessy|1998|pp=27–39}}}}

[[File:Intel 8742 153056995.jpg|right|thumb|The [[die (integrated circuit)|die]] from an Intel [[Intel MCS-48|8742]], an 8-bit [[microcontroller]] that includes a CPU running at 12&nbsp;MHz, RAM, EPROM, and I/O]]
While the earliest microprocessor ICs literally contained only the processor, i.e. the central processing unit, of a computer, their progressive development naturally led to chips containing most or all of the internal electronic parts of a computer. The integrated circuit in the image on the right, for example, an [[Intel]] 8742, is an [[8-bit computing|8-bit]] [[microcontroller]] that includes a CPU running at 12&nbsp;MHz, 128 bytes of [[random-access memory|RAM]], 2048 bytes of [[EPROM]], and [[input/output|I/O]] in the same chip.

During the 1960s, there was considerable overlap between second and third generation technologies.{{efn|In the defense field, considerable work was done in the computerized implementation of equations such as {{harvnb|Kalman|1960|pp=35–45}}.}} IBM implemented its [[IBM Solid Logic Technology]] modules in [[hybrid circuit]]s for the IBM System/360 in 1964. As late as 1975, Sperry Univac continued the manufacture of second-generation machines such as the UNIVAC 494. The [[Burroughs large systems]] such as the B5000 were [[stack machine]]s, which allowed for simpler programming. These [[pushdown automaton]]s were also implemented in minicomputers and microprocessors later, which influenced programming language design. Minicomputers served as low-cost computer centers for industry, business and universities.{{sfn|Eckhouse|Morris|1979|pp=1–2}} It became possible to simulate analog circuits with the ''simulation program with integrated circuit emphasis'', or [[SPICE]] (1971) on minicomputers, one of the programs for electronic design automation ([[:Category:Electronic design automation software|EDA]]). The microprocessor led to the development of [[microcomputer]]s, small, low-cost computers that could be owned by individuals and small businesses. Microcomputers, the first of which appeared in the 1970s, became ubiquitous in the 1980s and beyond.

[[File:Altair 8800 Computer.jpg|right|thumb|Altair 8800]]
While which specific product is considered the first microcomputer system is a matter of debate, one of the earliest is R2E's [[Micral#Micral N|Micral N]] ([[François Gernelle]], [[André Truong Trong Thi|André Truong]]) launched "early 1973" using the Intel 8008.<ref>{{Cite web |url=https://www.system-cfg.com/detail.php?ident=811 |title=R2E Micral N|website=www.system-cfg.com |access-date=2022-12-02 |archive-date=2022-11-10 |archive-url=https://web.archive.org/web/20221110084947/https://www.system-cfg.com/detail.php?ident=811|url-status=live}}</ref> The first commercially available microcomputer kit was the [[Intel 8080]]-based [[Altair 8800]], which was announced in the January 1975 cover article of ''[[Popular Electronics]]''. However, the Altair 8800 was an extremely limited system in its initial stages, having only 256 bytes of [[DRAM]] in its initial package and no input-output except its toggle switches and LED register display. Despite this, it was initially surprisingly popular, with several hundred sales in the first year, and demand rapidly outstripped supply. Several early third-party vendors such as [[Cromemco]] and [[Processor Technology]] soon began supplying additional [[S-100 bus]] hardware for the Altair 8800.

In April 1975, at the [[Hannover Messe|Hannover Fair]], [[Olivetti]] presented the [[Olivetti P6060|P6060]], the world's first complete, pre-assembled personal computer system. The central processing unit consisted of two cards, code named PUCE1 and PUCE2, and unlike most other personal computers was built with [[Transistor–transistor logic|TTL]] components rather than a microprocessor. It had one or two 8" [[floppy disk]] drives, a 32-character [[plasma display]], 80-column graphical [[thermal printer]], 48 Kbytes of [[random-access memory|RAM]], and [[BASIC]] language. It weighed {{cvt|40|kg|lb}}. As a complete system, this was a significant step from the Altair, though it never achieved the same success. It was in competition with a similar product by IBM that had an external floppy disk drive.

From 1975 to 1977, most microcomputers, such as the [[KIM-1|MOS Technology KIM-1]], the [[Altair 8800]], and some versions of the [[Apple I]], were sold as kits for do-it-yourselfers. Pre-assembled systems did not gain much ground until 1977, with the introduction of the [[Apple II]], the Tandy [[TRS-80]], the first [[SWTPC]] computers, and the [[Commodore PET]]. Computing has evolved with microcomputer architectures, with features added from their larger brethren, now dominant in most market segments.

A NeXT Computer and its [[Object-oriented programming|object-oriented]] development tools and libraries were used by [[Tim Berners-Lee]] and [[Robert Cailliau]] at [[CERN]] to develop the world's first [[web server]] software, [[CERN httpd]], and also used to write the first [[web browser]], [[WorldWideWeb]].

Systems as complicated as computers require very high [[reliability engineering|reliability]]. ENIAC remained on, in continuous operation from 1947 to 1955, for eight years before being shut down. Although a vacuum tube might fail, it would be replaced without bringing down the system. By the simple strategy of never shutting down ENIAC, the failures were dramatically reduced. The vacuum-tube [[Semi-Automatic Ground Environment|SAGE]] air-defense computers became remarkably reliable – installed in pairs, one off-line, tubes likely to fail did so when the computer was intentionally run at reduced power to find them. [[Hot plugging|Hot-pluggable]] hard disks, like the hot-pluggable vacuum tubes of yesteryear, continue the tradition of repair during continuous operation. Semiconductor memories routinely have no errors when they operate, although operating systems like Unix have employed memory tests on start-up to detect failing hardware. Today, the requirement of reliable performance is made even more stringent when [[server farm]]s are the delivery platform.<ref>{{cite web |last=Shankland |first=Stephen |title=Google uncloaks once-secret server |website=CNET |date=1 April 2009 |url=https://news.cnet.com/8301-1001_3-10209580-92.html |access-date=2009-04-01 |url-status=dead |archive-url=https://web.archive.org/web/20140716084210/http://www.cnet.com/news/google-uncloaks-once-secret-server-10209580/ |archive-date=2014-07-16}} "Since 2005, its [Google's] data centers have been composed of standard shipping containers—each with 1,160 servers and a power consumption that can reach 250 kilowatts." —Ben Jai of Google.</ref> Google has managed this by using fault-tolerant software to recover from hardware failures, and is even working on the concept of replacing entire server farms on-the-fly, during a service event.<ref>{{cite web |last=Shankland |first=Stephen |title=Google spotlights data center inner workings |website=CNET |date=30 May 2008 |url=https://news.cnet.com/8301-10784_3-9955184-7.html?tag=nefd.lede |access-date=2008-05-31 |url-status=dead |archive-url=https://web.archive.org/web/20140818092344/http://www.cnet.com/news/google-spotlights-data-center-inner-workings/ |archive-date=2014-08-18}} "If you're running 10,000 machines, something is going to die every day." —Jeff Dean of Google.</ref><ref>{{cite web|title=Google Groups |url=https://groups.google.com/group/google-appengine/browse_thread/thread/a7640a2743922dcf?pli=1 |access-date=11 August 2015 |archive-url=https://web.archive.org/web/20110913014648/https://groups.google.com/group/google-appengine/browse_thread/thread/a7640a2743922dcf?pli=1 |archive-date=2011-09-13|url-status=live}}</ref>

In the 21st century, [[multi-core]] CPUs became commercially available.<ref>{{cite web |last=Shrout |first=Ryan |date=2 December 2009 |website=PC Perspective |url=https://pcper.com/2009/12/intel-shows-48-core-x86-processor-as-single-chip-cloud-computer/ |title=Intel Shows 48-core x86 Processor as Single-chip Cloud Computer|archive-url=https://web.archive.org/web/20100814203128/http://www.pcper.com/article.php?aid=825 |archive-date=2010-08-14 |url-status=live |access-date=2020-12-02}}<br/>{{*}}{{cite web |date=3 December 2009 |title=Intel unveils 48-core cloud computing silicon chip |work=BBC News |url=https://news.bbc.co.uk/2/hi/technology/8392392.stm |access-date=2009-12-03 |archive-date=2012-12-06 |archive-url=https://web.archive.org/web/20121206054225/http://news.bbc.co.uk/2/hi/technology/8392392.stm |url-status=live}}</ref> [[Content-addressable memory]] (CAM){{sfn|Kohonen|1980|p={{page needed|date=August 2023}}}} has become inexpensive enough to be used in networking, and is frequently used for on-chip [[cache memory]] in modern microprocessors, although no computer system has yet implemented hardware CAMs for use in programming languages. Currently, CAMs (or associative arrays) in software are programming-language-specific. Semiconductor memory cell arrays are very regular structures, and manufacturers prove their processes on them; this allows price reductions on memory products. During the 1980s, [[CMOS]] [[logic gates]] developed into devices that could be made as fast as other circuit types; computer power consumption could therefore be decreased dramatically. Unlike the continuous current draw of a gate based on other logic types, a CMOS gate only draws significant current, except for leakage, during the 'transition' between logic states.{{sfn|Mead|Conway|1980|pp=11-36}}

CMOS circuits have allowed computing to become a commercial [[Product (business)|product]] which is now ubiquitous, embedded in [[embedded system|many forms]], from greeting cards and [[Mobile phone|telephone]]s to [[Satellite communications#History|satellites]]. The [[thermal design power]] which is dissipated during operation has become as essential as computing speed of operation. In 2006 servers consumed 1.5% of the total U.S. electricity consumption.<ref>{{cite report |date=2007 |title=Energystar report |page=4 |url=https://www.energystar.gov/ia/partners/prod_development/downloads/EPA_Report_Exec_Summary_Final.pdf?f272-71fc |access-date=2013-08-18 |archive-date=2013-10-22 |archive-url=https://web.archive.org/web/20131022230644/http://www.energystar.gov/ia/partners/prod_development/downloads/EPA_Report_Exec_Summary_Final.pdf?f272-71fc |url-status=live }}</ref> The energy consumption of computer data centers was expected to double to 3% of world consumption by 2011. The [[System on a chip|SoC]] (system on a chip) has compressed even more of the [[integrated circuit]]ry into a single chip; SoCs are enabling phones and PCs to converge into single hand-held wireless [[mobile computing|mobile device]]s.<ref>{{cite web |first=Walt |last=Mossberg |date=9 July 2014 |url=https://recode.net/2014/07/09/how-the-pc-is-merging-with-the-smartphone/ |title=How the PC is merging with the smartphone |access-date=2014-07-09 |url-status=live |archive-date=2014-07-09 |archive-url=https://web.archive.org/web/20140709183504/http://recode.net/2014/07/09/how-the-pc-is-merging-with-the-smartphone/}}</ref>

{{anchor|quantum computing}}[[Quantum computing]] is an emerging technology in the field of computing. ''MIT Technology Review'' reported 10 November 2017 that IBM has created a 50-[[qubit]] computer; currently its quantum state lasts 50 microseconds.<ref>{{cite web |url=https://www.technologyreview.com/s/609451/ibm-raises-the-bar-with-a-50-qubit-quantum-computer/ |first=Will |last=Knight |work=MIT Technology Review |date=10 November 2017 |title=IBM Raises the Bar with a 50-Qubit Quantum Computer |access-date=2017-11-10 |url-status=live |archive-date=2017-11-12 |archive-url=https://web.archive.org/web/20171112050728/https://www.technologyreview.com/s/609451/ibm-raises-the-bar-with-a-50-qubit-quantum-computer/}}</ref> Google researchers have been able to extend the 50 microsecond time limit, as reported 14 July 2021 in ''Nature'';<ref name=quantumErrorCorrection/> stability has been extended 100-fold by spreading a single logical qubit over chains of data qubits for [[quantum error correction]].<ref name=quantumErrorCorrection>{{cite journal |doi=10.1038/s41586-021-03588-y |doi-access=free |collaboration=Google Quantum AI |author=Julian Kelly |display-authors=etal |date=15 July 2021 |title=Exponential suppression of bit or phase errors with cyclic error correction |journal=Nature |volume=595 |issue=7867 |pages=383–387 |pmid=34262210 |pmc=8279951 |url=https://www.nature.com/articles/s41586-021-03588-y.pdf?pdf=button%20sticky}} Cited in {{cite web |author=Adrian Cho |date=14 July 2021 |title=Physicists move closer to defeating errors in quantum computation |magazine=Science |url=https://www.science.org/content/article/physicists-move-closer-defeating-errors-quantum-computation}}</ref> ''Physical Review X'' reported a technique for 'single-gate sensing as a viable readout method for spin qubits' (a singlet-triplet spin state in silicon) on 26 November 2018.<ref>{{Cite journal |title=Single-Shot Single-Gate rf Spin Readout in Silicon |first1=P. |last1=Pakkiam |first2=A. V. |last2=Timofeev |first3=M. G. |last3=House |first4=M. R. |last4=Hogg |first5=T. |last5=Kobayashi |first6=M. |last6=Koch |first7=S. |last7=Rogge |first8=M. Y. |last8=Simmons |date=26 November 2018 |journal=Physical Review X |volume=8 |issue=4 |at=041032 |via=APS |doi=10.1103/PhysRevX.8.041032 |arxiv=1809.01802 |bibcode=2018PhRvX...8d1032P |s2cid=119363882}}</ref> A Google team has succeeded in operating their RF pulse modulator chip at 3&nbsp;[[kelvin]]s, simplifying the cryogenics of their 72-qubit computer, which is set up to operate at 0.3&nbsp;[[kelvin|K]]; but the readout circuitry and another driver remain to be brought into the cryogenics.<ref name=72qubits>{{cite web |first=Samuel K. |last=Moore |work=IEEE Spectrum |date=13 March 2019 |title=Google Builds Circuit to Solve One of Quantum Computing's Biggest Problems |url=https://spectrum.ieee.org/google-team-builds-circuit-to-solve-one-of-quantum-computings-biggest-problems |access-date=2019-03-14 |archive-date=2019-03-14 |archive-url=https://web.archive.org/web/20190314213116/https://spectrum.ieee.org/tech-talk/semiconductors/design/google-team-builds-circuit-to-solve-one-of-quantum-computings-biggest-problems |url-status=live}}</ref>{{efn|name=ibmEagle |IBM's 127-qubit computer cannot be simulated on traditional computers.<ref name=127qubits>{{cite web |author=Ina Fried |date=14 Nov 2021 |url=https://www.axios.com/ibm-quantum-computing-axios-hbo-bd9d50b7-3c11-4586-bdb1-8bbc9928ad1b.html |title=Exclusive: IBM achieves quantum computing breakthrough |website=Axios |archive-url=https://web.archive.org/web/20211115133314/https://www.axios.com/ibm-quantum-computing-axios-hbo-bd9d50b7-3c11-4586-bdb1-8bbc9928ad1b.html |archive-date=2021-11-15 |url-status=live}}</ref>}} ''See: [[Quantum supremacy]]''<ref>{{cite web |first=Russ |last=Juskalian |date=22 February 2017 |title=Practical Quantum Computers |url=https://mittr-frontend-prod.herokuapp.com/s/603495/10-breakthrough-technologies-2017-practical-quantum-computers/amp/ |work=MIT Technology Review|access-date=2020-12-02|archive-url=https://web.archive.org/web/20210623193833/https://mittr-frontend-prod.herokuapp.com/s/603495/10-breakthrough-technologies-2017-practical-quantum-computers/amp/ |archive-date=2021-06-23 |url-status=live}}</ref><ref>{{cite web |first=John D. |last=MacKinnon |date=19 December 2018 |url=https://www.wsj.com/articles/congress-expected-to-pass-bill-spurring-quantum-computing-11545250595 |work=The Wall Street Journal |title=House Passes Bill to Create National Quantum Computing Program |access-date=2018-12-20 |archive-url=https://web.archive.org/web/20181220084728/https://www.wsj.com/articles/congress-expected-to-pass-bill-spurring-quantum-computing-11545250595 |archive-date=2018-12-20 |url-status=live}}</ref> Silicon qubit systems have demonstrated [[quantum entanglement|entanglement]] at [[action at a distance|non-local]] distances.<ref>{{cite web |url=https://scitechdaily.com/quantum-computing-breakthrough-silicon-qubits-interact-at-long-distance/ |author=Princeton University |date=25 December 2019 |title=Quantum Computing Breakthrough: Silicon Qubits Interact at Long-Distance |work=SciTechDaily |access-date=2019-12-26 |archive-date=2019-12-26 |archive-url=https://web.archive.org/web/20191226165255/https://scitechdaily.com/quantum-computing-breakthrough-silicon-qubits-interact-at-long-distance/ |url-status=live}}</ref>

Computing hardware and its software have even become a metaphor for the operation of the universe.<ref>{{harvnb|Smolin|2001|pp=53–57}}. Pages 220–226 are annotated references and guide for further reading.</ref>

==Epilogue==
An indication of the rapidity of development of this field can be inferred from the history of the seminal 1947 article by Burks, Goldstine and von Neumann.<ref>{{harvnb|Burks|Goldstine|von Neumann|1947|pp=1–464}} reprinted in ''[[Datamation]]'', September–October 1962. Note that ''preliminary discussion/design'' was the term later called ''system analysis/design'', and even later, called ''system architecture.''</ref> By the time that anyone had time to write anything down, it was obsolete. After 1945, others read John von Neumann's  ''First Draft of a Report on the EDVAC'', and immediately started implementing their own systems. To this day, the rapid pace of development has continued, worldwide.{{efn|''[[DBLP]]'' summarizes the ''[[Annals of the History of Computing]]'', year by year, back to 1979.<ref>{{cite web |title=IEEE Annals of the History of Computing |publisher=[[Dagstuhl|Schloss Dagstuhl – Leibniz-Zentrum für Informatik]] |url=https://www.informatik.uni-trier.de/~ley/db/journals/annals/ |access-date=2023-08-29 |url-status=live |archive-url=https://web.archive.org/web/20110320212935/http://www.informatik.uni-trier.de/~ley/db/journals/annals/ |archive-date=2011-03-20}}</ref>}}{{efn|The fastest [[supercomputer]] of the [[top 500]] is now Frontier (of Oak Ridge National Laboratory) at 1.102 ExaFlops,<ref>{{Cite web |date=2022-05-30 |title=ORNL's Frontier First to Break the Exaflop Ceiling |website=top500.org |url=https://www.top500.org/news/ornls-frontier-first-to-break-the-exaflop-ceiling/ |url-status=live |archive-url=https://web.archive.org/web/20220602004225/https://www.top500.org/news/ornls-frontier-first-to-break-the-exaflop-ceiling/ |archive-date=2022-06-02 |access-date=2023-08-26}}</ref> which is 2.66 times faster than Fugaku, now number two of the top 500.<ref>{{cite web |url=https://gizmodo.com/japans-new-fugaku-supercomputer-is-number-one-ranking-1844126655 |first=Tom |last=McKay |date=22 June 2020 |title=Japan's New Fugaku Supercomputer Is Number One, Ranking in at 415 Petaflops |website=Gizmodo |access-date=2020-06-23 |archive-date=2020-06-23 |archive-url=https://web.archive.org/web/20200623174019/https://gizmodo.com/japans-new-fugaku-supercomputer-is-number-one-ranking-1844126655 |url-status=live }}</ref>}}

==See also==
* {{annotated link|Antikythera mechanism}}
* {{annotated link|History of computing}}
* {{annotated link|History of computing hardware (1960s–present)}}
* {{annotated link|History of laptops}}
* {{annotated link|History of personal computers}}
* {{annotated link|History of software}}
* {{Annotated link|History of supercomputing}}
* {{annotated link|Information Age}}
* {{annotated link|IT History Society}}
* {{annotated link|Retrocomputing}}
* {{annotated link|Timeline of computing}}
* {{annotated link|List of pioneers in computer science}}
* {{annotated link|Vacuum-tube computer}}

==Notes==
{{notelist|40em}}
<references>
<ref name=EarlyComputers>{{citation |title=Early Electronic Computers (1946–51) |publisher=University of Manchester |url=https://www.computer50.org/mark1/contemporary.html |access-date=16 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20090105031620/http://www.computer50.org/mark1/contemporary.html |archive-date=5 January 2009 |website=Computer 50}}</ref>
</references>

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{{refend}}

==Further reading==
* {{cite web |title=online access |url=https://csdl2.computer.org/persagen/DLPublication.jsp?pubtype=m&acronym=an |work=[[IEEE Annals of the History of Computing]] |archive-url=https://web.archive.org/web/20060523142200/http://csdl2.computer.org/persagen/DLPublication.jsp?pubtype=m&acronym=an |archive-date=2006-05-23 |url-status=dead}}
* {{Citation | last = Ceruzzi | first = Paul E. | author-link = Paul E. Ceruzzi | title = A History of Modern Computing  | publisher = The MIT Press | year = 1998 }}
* Haigh, Thomas; Ceruzzi , Paul E. (2021) : ''A New History of Modern Computing'' (History of Computing), Cambridge, Massachusetts ; London, England: MIT Press, 544 pp.
* [https://www.bitsavers.org/magazines/Computers_And_Automation/ Computers and Automation] Magazine – Pictorial Report on the Computer Field:
** ''A PICTORIAL INTRODUCTION TO COMPUTERS'' – [https://www.bitsavers.org/magazines/Computers_And_Automation/195706.pdf 06/1957]
** ''A PICTORIAL MANUAL ON COMPUTERS'' – [https://www.bitsavers.org/magazines/Computers_And_Automation/195712.pdf 12/1957]
** ''A PICTORIAL MANUAL ON COMPUTERS, Part 2'' – [https://www.bitsavers.org/magazines/Computers_And_Automation/195801.pdf 01/1958]
** 1958–1967 Pictorial Report on the Computer Field – December issues ([https://www.bitsavers.org/magazines/Computers_And_Automation/ 195812.pdf, ..., 196712.pdf])
* ''Bit by Bit: An Illustrated History of Computers'', Stan Augarten, 1984. [http://ds-wordpress.haverford.edu/bitbybit/ OCR with permission of the author]
* {{cite web
 |title        = Z3 Computer (1938–1941)
 |website      = www.computermuseum.li
 |url          = http://www.computermuseum.li/Testpage/Z3-Computer-1939.htm
 |access-date  = 2008-06-01
 |url-status   = dead
 |archive-url  = https://web.archive.org/web/20080617234903/http://www.computermuseum.li/Testpage/Z3-Computer-1939.htm
 |archive-date = 2008-06-17
}}

==External links==
{{Wikiversity|Introduction to Computers/History}}
{{Commons category|History of computing hardware}}
*[https://www.oldcomputers.net/ Obsolete Technology – Old Computers]
*[https://meta-studies.net/pmwiki/pmwiki.php?n=Site.Introduction ''Things That Count'']
*[https://museum.ipsj.or.jp/en/computer/index.html Historic Computers in Japan]
*[https://www.xnumber.com/xnumber/japanese_calculators.htm The History of Japanese Mechanical Calculating Machines]
*[https://web.archive.org/web/20090405054226/http://www.trailing-edge.com/~bobbemer/HISTORY.HTM Computer History] — a collection of articles by [[Bob Bemer]]
*[https://web.archive.org/web/20190610103014/https://spectrum.ieee.org/static/25chips 25 Microchips that shook the world] (archived) – a collection of articles by the [[Institute of Electrical and Electronics Engineers]]
*[https://www.columbia.edu/cu/computinghistory/ Columbia University Computing History]
*[http://www.computerhistories.org/ Computer Histories] – An introductory course on the history of computing
*[https://www.computerhistory.org/revolution/ Revolution – The First 2000 Years Of Computing], Computer History Museum

{{Mainframes}}
{{Basic computer components}}

[[Category:History of computing hardware| ]]
[[Category:Early computers| ]]
[[Category:One-of-a-kind computers|*01]]
[[Category:History of computing|Hardware]]