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{{history of computing}}
The '''history of computer science''' began long before the modern discipline of [[computer science]], usually appearing in forms like [[mathematics]] or [[physics]]. Developments in previous centuries alluded to the discipline that we now know as computer science.<ref name=Tedre2014b>{{cite book |last=Tedre |first=Matti |year=2014 |title=The Science of Computing: Shaping a Discipline |publisher=Chapman Hall}}</ref> This progression, from mechanical inventions and [[mathematics|mathematical]] theories towards [[Universal Machine|modern computer concepts and machines]], led to the development of a major [[Academic discipline|academic field]], massive technological advancement across the [[Western world]], and the basis of massive worldwide trade and culture.<ref>{{cite web|url=http://www.cs.uwaterloo.ca/~shallit/Courses/134/history.html|title=History of Computer Science|work=uwaterloo.ca}}</ref>

== Prehistory ==
[[File:John Napier.JPG|left|thumb|[[John Napier]] (1550–1617), the inventor of [[logarithms]]]]
The earliest known tool for use in computation was the [[abacus]], developed in the period between 2700 and 2300 BCE in [[Sumer]].<ref>{{cite book | last1 = Boyer | first1 = Carl B. | last2 = Merzbach | first2 = Uta C. | author2-link = Uta Merzbach | title = A History of Mathematics | year = 1991 | publisher = John Wiley & Sons, Inc. | edition = 2nd | isbn = 978-0-471-54397-8 | pages = [https://archive.org/details/historyofmathema00boye/page/252 252–253] | url = https://archive.org/details/historyofmathema00boye/page/252 }}</ref> The Sumerians' abacus consisted of a table of successive columns which delimited the successive [[order of magnitude|orders of magnitude]] of their [[sexagesimal]] number system.<ref name=Ifrah2001>{{cite book |last=Ifrah |first=Georges |year=2001 |title=The Universal History of Computing: From the Abacus to the Quantum Computer |publisher=John Wiley & Sons |isbn=978-0-471-39671-0 |url=https://archive.org/details/unset0000unse_w3q2 }}</ref>{{rp|11}} Its original style of usage was by lines drawn in sand with pebbles. Abaci of a more modern design are still used as calculation tools today, such as the [[Chinese abacus]].<ref>{{cite news|last=Bellos|first=Alex|url=https://www.theguardian.com/science/alexs-adventures-in-numberland/2012/oct/25/abacus-number-joy-japan|title=Abacus adds up to number joy in Japan|access-date=2013-06-25|location=London|work=The Guardian|date=2012-10-25}}</ref>

In the 5th century BC in [[History of India|ancient India]], the [[Philologist|grammarian]] [[Pāṇini]] formulated the [[grammar]] of [[Sanskrit]] in 3959 rules known as the [[Ashtadhyayi]] which was highly systematized and technical. Panini used metarules, [[Transformational grammar|transformations]] and [[recursion]]s.<ref>{{Cite journal | doi = 10.1016/0024-3841(78)90076-1| title = On the status of recursive rules in transformational grammar| journal = [[Lingua (journal)|Lingua]]| volume = 44| issue = 2–3| pages = 169–218| year = 1978| last1 = Sinha | first1 = A. C. }}</ref>

The [[Antikythera mechanism]] is believed to be an early mechanical analog computer.<ref name="antikythera-mechanism">{{cite web|url=https://www.antikythera-mechanism.gr/project/overview|title=Project Overview|website=The Antikythera Mechanism Research Project|access-date=2023-07-06|archive-date=2022-05-21|archive-url=https://web.archive.org/web/20220521123001/http://antikythera-mechanism.gr/project/overview|url-status=live}}</ref>  It was designed to calculate astronomical positions. It was discovered in 1901 in the [[Antikythera]] wreck off the Greek island of Antikythera, between [[Kythira|Kythera]] and [[Crete]], and has been dated to ''circa'' 100 BC.<ref name="antikythera-mechanism"/>

Mechanical analog computer devices appeared again a thousand years later in the [[Islamic Golden Age|medieval Islamic world]]. They were developed by [[Islamic astronomy|Muslim astronomers]], such as the mechanical geared [[astrolabe]] by [[Abū Rayhān al-Bīrūnī]],<ref name=usc>{{cite web|url=http://islamicweb.com/begin/woi_knowledge.htm|title=Islam, Knowledge, and Science|publisher=Islamic Web|access-date=2017-11-05}}</ref> and the [[torquetum]] by [[Jabir ibn Aflah]].<ref>{{citation|first=R. P.|last=Lorch|title=The Astronomical Instruments of Jabir ibn Aflah and the Torquetum|journal=[[Centaurus (journal)|Centaurus]]|volume=20|issue=1|year=1976|pages=11–34|doi=10.1111/j.1600-0498.1976.tb00214.x|bibcode=1976Cent...20...11L}}</ref> According to [[Simon Singh]], [[Islamic mathematics|Muslim mathematicians]] also made important advances in [[cryptography]], such as the development of [[cryptanalysis]] and [[frequency analysis]] by [[Al-Kindi|Alkindus]].<ref>{{cite book |author=Simon Singh |author-link=Simon Singh |title=[[The Code Book]] |pages=14–20}}</ref><ref>{{cite web |url=https://muslimheritage.com/al-kindi-cryptography/ |title= Al-Kindi, Cryptography, Codebreaking and Ciphers |date= 9 June 2003 |access-date=2023-08-25 }}</ref> [[Program (machine)|Programmable]] machines were also invented by [[Inventions in medieval Islam|Muslim engineers]], such as the automatic [[flute]] player by the [[Banū Mūsā]] brothers.<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 |doi=10.1016/S0094-114X(01)00005-2 |postscript=.}}</ref> 

Technological artifacts of similar complexity appeared in 14th century [[Europe]], with mechanical [[astronomical clock]]s.<ref name=insearchoflosttime>{{cite journal | last1 = Marchant | first1 = Jo | title = In search of lost time | journal = Nature | volume =  444| issue = 7119| pages =  534–538| doi = 10.1038/444534a | pmid = 17136067 | date = November 2006 | bibcode = 2006Natur.444..534M | doi-access = free }}</ref>

When [[John Napier]] discovered [[logarithm]]s for computational purposes in the early 17th century,<ref>{{cite journal |title=John Napier and the Invention of Logarithms, 1614 . E. W. Hobson |journal=Isis |date=October 1920 |volume=3 |issue=2 |pages=285–286 |doi=10.1086/357925 |doi-access=free }}</ref> there followed a period of considerable progress by inventors and scientists in making calculating tools. In 1623 [[Wilhelm Schickard]] designed the calculating machine as a commission for [[Johannes Kepler]] which he named the Calculating Clock, but abandoned the project, when the prototype he had started building was destroyed by a fire in 1624.<ref>{{Cite web|title=1.6 Shickard's Calculating Clock {{!}} Bit by Bit|url=http://ds-wordpress.haverford.edu/bitbybit/bit-by-bit-contents/chapter-one/1-6-shickards-calculating-clock/|access-date=2021-03-17|language=en-US}}</ref> Around 1640, [[Blaise Pascal]], a leading French mathematician, constructed a mechanical adding device based on a design described by [[Ancient Greece|Greek]] mathematician [[Hero of Alexandria]].<ref>{{cite web|url=http://lecture.eingang.org/pascaline.html|title=History of Computing Science: The First Mechanical Calculator|work=eingang.org}}</ref> Then in 1672 [[Gottfried Wilhelm Leibniz]] invented the [[Stepped Reckoner]] which he completed in 1694.<ref name="Meyer1925">{{cite book |last=Kidwell |first=Peggy Aldritch |author-link= Peggy A. Kidwell |author2=Williams, Michael R. |title=The Calculating Machines: Their history and development |year=1992 |publisher=MIT Press|title-link=The Calculating Machines}}, p.38-42, translated and edited from {{cite book |last=Martin |first=Ernst |title=Die Rechenmaschinen und ihre Entwicklungsgeschichte |year=1925 |publisher=Pappenheim |location=Germany}}</ref>

In 1837 [[Charles Babbage]] first described his [[Analytical Engine]] which is accepted as the first design for a modern computer. The analytical engine had expandable memory, an arithmetic unit, and logic processing capabilities that enabled it to interpret a [[programming language]] with loops and conditional branching. Although never built, the design has been studied extensively and is understood to be [[Turing complete|Turing equivalent]]. The analytical engine would have had a memory capacity of less than 1 [[kilobyte]] of memory and a [[Clock rate|clock speed]] of less than 10 [[Hertz]].<ref>{{Cite web|title=CS History|url=https://everythingcomputerscience.com/CSHistory.html|website=everythingcomputerscience.com|access-date=2020-05-01}}</ref>

Considerable advancement in mathematics and [[electronics]] theory was required before the first modern computers could be designed.

== Binary logic ==

=== Gottfried Wilhelm Leibniz ===
{{Main|Gottfried Wilhelm Leibniz}}
[[File:Christoph Bernhard Francke - Bildnis des Philosophen Leibniz (ca. 1695).jpg|thumb|200x200px|[[Gottfried Wilhelm Leibniz]] (1646–1716) developed [[logic]] in a [[binary number]] system and has been called the "founder of computer science".<ref>{{cite web |title=2021: 375th birthday of Leibniz, father of computer science |url=https://people.idsia.ch/~juergen/leibniz-father-computer-science-375.html |website=people.idsia.ch}}</ref>]] 
In 1702, [[Gottfried Wilhelm Leibniz]] developed [[logic]] in a formal, mathematical sense with his writings on the binary numeral system. Leibniz simplified the binary system and articulated logical properties such as conjunction, disjunction, negation, identity, inclusion, and the empty set.<ref>{{cite journal |last1=Lande |first1=Daniel R. |title=Development of the Binary Number System and the Foundations of Computer Science |journal=The Mathematics Enthusiast |date=December 2014 |volume=11 |issue=3 |pages=513–540 |id={{ProQuest|1646358626}} |doi=10.54870/1551-3440.1315 }}</ref> He anticipated [[Lagrange polynomial|Lagrangian interpolation]] and [[algorithmic information theory]]. His [[calculus ratiocinator]] anticipated aspects of the [[universal Turing machine]]. In 1961, [[Norbert Wiener]] suggested that Leibniz should be considered the patron saint of [[cybernetics]].<ref>{{cite book |last1=Wiener |first1=Norbert |title=Cybernetics Or Control and Communication in the Animal and the Machine |date=1961 |publisher=MIT Press |isbn=978-0-262-73009-9 |page=12 }}</ref> Wiener is quoted with "Indeed, the general idea of a computing machine is nothing but a mechanization of Leibniz's Calculus Ratiocinator."<ref>{{cite journal |last1=Wiener |first1=Norbert |title=Time, Communication, and the Nervous System |journal=Annals of the New York Academy of Sciences |date=1948 |volume=50 |issue=4 Teleological |pages=197–220 |doi=10.1111/j.1749-6632.1948.tb39853.x |pmid=18886381 |bibcode=1948NYASA..50..197W }}</ref> But it took more than a century before [[George Boole]] published his [[Boolean algebra (logic)|Boolean algebra]] in 1854 with a complete system that allowed computational processes to be mathematically modeled.<ref name="Tedre2014">{{cite book |last=Tedre |first=Matti |title=The Science of Computing: Shaping a Discipline |year=2014 |publisher=CRC Press }}</ref>

By this time, the first mechanical devices driven by a binary pattern had been invented. The [[Industrial Revolution]] had driven forward the mechanization of many tasks, and this included [[weaving]]. [[Punched cards]] controlled [[Joseph Marie Jacquard]]'s loom in 1801, where a hole punched in the card indicated a binary ''one'' and an unpunched spot indicated a binary ''zero''. Jacquard's loom was far from being a computer, but it did illustrate that machines could be driven by binary systems and stored binary information.<ref name="Tedre2014" />

== Emergence of a discipline ==
[[File:Portrait of Charles Babbage (4672397).jpg|left|thumb|329x329px|[[Charles Babbage]] (1791–1871), one of the pioneers of computing]]

=== Charles Babbage and Ada Lovelace ===
{{Main|Charles Babbage|Ada Lovelace}}
[[Charles Babbage]] is often regarded as one of the first pioneers of computing. Beginning in the 1810s, Babbage had a vision of mechanically computing numbers and tables. Putting this into reality, Babbage designed a calculator to compute numbers up to 8 decimal points long. Continuing with the success of this idea, Babbage worked to develop a machine that could compute numbers with up to 20 decimal places. By the 1830s, Babbage had devised a plan to develop a machine that could use punched cards to perform arithmetical operations. The machine would store numbers in memory units, and there would be a form of sequential control.  This means that one operation would be carried out before another in such a way that the machine would produce an answer and not fail. This machine was to be known as the "Analytical Engine", which was the first true representation of what is the modern computer.<ref name="Charles Babbage"/>

[[File: Ada Byron daguerreotype by Antoine Claudet 1843 or 1850 - cropped.png|thumb|[[Ada Lovelace]] (1815–1852) predicted the use of computers in symbolic manipulation]]
[[Ada Lovelace]] (Augusta Ada Byron) is credited as the pioneer of computer programming and is regarded as a mathematical genius. Lovelace began working with Charles Babbage as an assistant while Babbage was working on his "Analytical Engine", the first mechanical computer. {{Sfn|Evans|2018|p=16}} During her work with Babbage, Ada Lovelace became the designer of the first computer algorithm, which could compute [[Bernoulli numbers]],{{Sfn|Evans|2018|p=21}} although this is arguable as Charles was the first to design the difference engine and consequently its corresponding difference based algorithms, making him the first computer algorithm designer.  Moreover, Lovelace's work with Babbage resulted in her prediction of future computers to not only perform mathematical calculations but also manipulate symbols, mathematical or not.{{Sfn|Evans|2018|p=20}} While she was never able to see the results of her work, as the "Analytical Engine" was not created in her lifetime, her efforts in later years, beginning in the 1840s, did not go unnoticed.<ref name="Ada Lovelace" />

=== Early post-Analytical Engine designs ===

[[File:Leonardo_Torres_Quevedo_1912.png |thumb|left|upright=0.84|[[Leonardo Torres Quevedo]] (1852–1936) proposed a consistent manner to store [[Floating-point arithmetic|floating-point numbers]]]]

Following Babbage, although at first unaware of his earlier work, was [[Percy Ludgate]], a clerk to a corn merchant in Dublin, Ireland. He independently designed a programmable mechanical computer, which he described in a work that was published in 1909.<ref>{{Cite web |url=https://scss.tcd.ie/SCSSTreasuresCatalog/miscellany/TCD-SCSS-X.20121208.002/TCD-SCSS-X.20121208.002.pdf/ |title=The John Gabriel Byrne Computer Science Collection |access-date=2019-08-08 |archive-url=https://web.archive.org/web/20190416071721/https://www.scss.tcd.ie/SCSSTreasuresCatalog/miscellany/TCD-SCSS-X.20121208.002/TCD-SCSS-X.20121208.002.pdf |archive-date=2019-04-16 |url-status=dead }}</ref><ref>{{cite web|url=http://ingeniousireland.ie/2012/10/1909-a-novel-irish-computer/|title=1907: was the first portable computer design Irish?|date=17 October 2012|website=Ingenious Ireland}}</ref> 

Two other inventors, [[Leonardo Torres Quevedo]] and [[Vannevar Bush]], also did follow on research based on Babbage's work. In his ''Essays on Automatics'' (1914), Torres designed an analytical electromechanical machine that was controlled by a [[Read-only memory|read-only]] program and introduced the idea of [[floating-point arithmetic]].<ref name="LTQ1914es">{{cite journal |author=L. Torres Quevedo |title=Ensayos sobre Automática – Su definicion. Extension teórica de sus aplicaciones |journal=Revista de la Academia de Ciencias Exacta, Revista 12 |pages=391–418| date=1914}}</ref><ref>{{cite journal |last=Torres Quevedo |first=Leonardo |url=https://quickclick.es/rop/pdf/publico/1914/1914_tomoI_2043_01.pdf |title=Automática: Complemento de la Teoría de las Máquinas |pages=575–583 |journal=Revista de Obras Públicas |volume=LXII |issue=2043 |date=19 November 1914}}</ref><ref>{{cite book |doi=10.1007/978-3-031-67482-2 |title=Numbers and Computers |series=Texts in Computer Science |date=2025 |isbn=978-3-031-67481-5 |first1=Ronald T |last1=Kneusel |pages=84–85 }}</ref> In 1920, to celebrate the 100th anniversary of the invention of the [[arithmometer]], he presented in Paris the [[Leonardo Torres y Quevedo#Analytical machines| Electromechanical Arithmometer]], which consisted of an arithmetic unit connected to a (possibly remote) typewriter, on which commands could be typed and the results printed automatically.<ref name="Randell1982p109">{{cite book |doi=10.1007/978-3-642-61812-3_7 |chapter=Electromechanical Calculating Machine |title=The Origins of Digital Computers |date=1982 |last1=Torres y Quevedo |first1=Leonardo |pages=109–120 |isbn=978-3-642-61814-7 }}</ref> Bush's paper ''Instrumental Analysis'' (1936) discussed using existing IBM punch card machines to implement Babbage's design. In the same year he started the Rapid Arithmetical Machine project to investigate the problems of constructing an electronic digital computer.<ref name=RANDELL>{{ cite web|url=http://www.cs.ncl.ac.uk/publications/articles/papers/398.pdf |title=From Analytical Engine to Electronic Digital Computer: The Contributions of Ludgate, Torres, and Bush |last1=Randell |first1=Brian |author-link1=Brian Randell |access-date=9 September 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130921055055/http://www.cs.ncl.ac.uk/publications/articles/papers/398.pdf |archive-date=21 September 2013 }}</ref>

=== Charles Sanders Peirce and electrical switching circuits ===
[[File:Charles Sanders Peirce theb3558.jpg|thumb|221x221px|[[Charles Sanders Peirce]] (1839–1914) described how logical operations could be carried out by [[Switching circuit theory|electrical switching circuits]]]]
In an 1886 letter, [[Charles Sanders Peirce]] described how logical operations could be carried out by electrical switching circuits.<ref name="P2M">Peirce, C. S., "Letter, Peirce to [[Allan Marquand|A. Marquand]]", dated 1886, ''[[Charles Sanders Peirce bibliography#W|Writings of Charles S. Peirce]]'', v. 5, 1993, pp. 421–23. See [[Arthur W. Burks|Burks, Arthur W.]], "Review: Charles S. Peirce, ''The new elements of mathematics''", ''Bulletin of the American Mathematical Society'' v. 84, n. 5 (1978), pp. 913–18, see 917. [https://projecteuclid.org/journals/bulletin-of-the-american-mathematical-society/volume-84/issue-5/Review-Charles-S-Peirce-The-new-elements-of-mathematics/bams/1183541145.full PDF].</ref> During 1880–81 he showed that [[NOR logic|NOR gates alone]] (or alternatively [[NAND logic|NAND gates alone]]) can be used to reproduce the functions of all the other [[logic gate]]s, but this work on it was unpublished until 1933.<ref>Peirce, C. S. (manuscript winter of 1880–81), "A Boolian Algebra with One Constant", published 1933 in ''[[Charles Sanders Peirce bibliography#CP|Collected Papers]]'' v. 4, paragraphs 12–20. Reprinted 1989 in ''[[Charles Sanders Peirce bibliography#W|Writings of Charles S. Peirce]]'' v. 4, pp. 218–21, Google [https://archive.org/details/writingsofcharle0002peir/page/218]. See Roberts, Don D. (2009), ''The Existential Graphs of Charles S. Peirce'', p. 131.</ref> The first published proof was by [[Henry M. Sheffer]] in 1913, so the NAND logical operation is sometimes called [[Sheffer stroke]]; the [[logical NOR]] is sometimes called ''Peirce's arrow''.<ref name="BüningLettmann1999">{{cite book|author1=Hans Kleine Büning|url=https://books.google.com/books?id=3oJE9yczr3EC&pg=PA2|title=Propositional logic: deduction and algorithms|author2=Theodor Lettmann|publisher=Cambridge University Press|year=1999|isbn=978-0-521-63017-7|page=2}}</ref> Consequently, these gates are sometimes called ''universal logic gates''.<ref name="Bird2007">{{cite book|author=John Bird|url=https://books.google.com/books?id=1-fBmsEBNUoC&pg=PA532|title=Engineering mathematics|publisher=Newnes|year=2007|isbn=978-0-7506-8555-9|page=532}}</ref>

Eventually, [[vacuum tube]]s replaced relays for logic operations. [[Lee De Forest]]'s modification, in 1907, of the [[Fleming valve]] can be used as a logic gate. [[Ludwig Wittgenstein]] introduced a version of the 16-row [[truth table]] as proposition 5.101 of ''[[Tractatus Logico-Philosophicus]]'' (1921). [[Walther Bothe]], inventor of the [[coincidence circuit]], got part of the 1954 [[Nobel Prize]] in physics, for the first modern electronic AND gate in 1924. [[Konrad Zuse]] designed and built electromechanical logic gates for his computer [[Z1 (computer)|Z1]] (from 1935 to 1938).

Up to and during the 1930s, electrical engineers were able to build electronic circuits to solve mathematical and logic problems, but most did so in an ''ad hoc'' manner, lacking any theoretical rigor.  This changed with [[switching circuit theory]] in the 1930s. From 1934 to 1936, [[Akira Nakashima]], [[Claude Shannon]], and Viktor Shetakov published a series of papers showing that the [[Two-element Boolean algebra|two-valued]] [[Boolean algebra]], can describe the operation of switching circuits.<ref>{{cite journal |last1=Yamada |first1=Akihiko |title=History of Research on Switching Theory in Japan |journal=IEEJ Transactions on Fundamentals and Materials |date=2004 |volume=124 |issue=8 |pages=720–726 |doi=10.1541/ieejfms.124.720 |bibcode=2004IJTFM.124..720Y |doi-access=free }}</ref><ref>{{cite web|url=http://museum.ipsj.or.jp/en/computer/dawn/0002.html|title=Switching Theory/Relay Circuit Network Theory/Theory of Logical Mathematics|website=IPSJ Computer Museum|publisher=[[Information Processing Society of Japan]]}}</ref><ref name="historical">{{cite report |first1=Radomir S |last1=Stanković |first2=Jaakko T |last2=Astola |first3=Mark G |last3=Karpovsky |title=Some historical remarks about the development and applications of switching |url=https://sites.bu.edu/mark/files/2018/02/200.pdf.pdf }}</ref><ref name="Stanković-Astola_2008">{{cite book |editor-first1=Radomir S.<!-- Stanislav? --> |editor-last1=Stanković |editor-link1=:de:Radomir S. Stanković |editor-first2=Jaakko Tapio |editor-last2=Astola |editor-link2=:fi:Jaakko Tapio Astola |date=2008 |isbn=978-952-15-1980-2 |volume=40 |issue=2 |url=http://ticsp.cs.tut.fi/reports/reprint-nakashima-rr.pdf |title=Reprints from the Early Days of Information Sciences: TICSP Series On the Contributions of Akira Nakashima to Switching Theory |series=Tampere International Center for Signal Processing (TICSP) Series |location=[[Tampere University of Technology]], Tampere, Finland |url-status=dead |archive-url=https://web.archive.org/web/20210308002559/http://ticsp.cs.tut.fi/reports/reprint-nakashima-rr.pdf |archive-date=2021-03-08}} (3+207+1 pages) [https://web.archive.org/web/20221026175726/http://ciitlab.elfak.ni.ac.rs/predavanja/09_Nakashima.mp4 10:00 min]</ref> This concept, of utilizing the properties of electrical switches to do logic, is the basic concept that underlies all electronic [[digital computer]]s. Switching circuit theory provided the mathematical foundations and tools for [[digital system]] design in almost all areas of modern technology.<ref name="Stanković-Astola_2008"/>

While taking an undergraduate philosophy class, Shannon had been exposed to [[George Boole|Boole's]] work, and recognized that it could be used to arrange electromechanical relays (then used in telephone routing switches) to solve logic problems. His thesis became the foundation of practical digital circuit design when it became widely known among the electrical engineering community during and after World War II.<ref>{{cite book |doi=10.7551/mitpress/12274.003.0010 |chapter=A Symbolic Analysis of Relay and Switching Circuits (1938) |title=Ideas That Created the Future |date=2021 |last1=Shannon |first1=Claude |pages=71–78 |isbn=978-0-262-36317-4 }}</ref>

=== Alan Turing and the Turing machine ===
{{Main|Alan Turing|Turing machine}}
[[File:Alan Turing az 1930-as években.jpg|thumb|right|[[Alan Turing]], English computer scientist, mathematician, logician, and cryptanalyst.  (circa 1930)]]
Before the 1920s, ''[[Computer (job description)|computers]]'' (sometimes ''computors'') were human clerks that performed computations. They were usually under the lead of a physicist. Many thousands of computers were employed in commerce, government, and research establishments. Many of these clerks who served as human computers were women.<ref>{{cite journal |last1=Light |first1=Jennifer S. |title=When Computers Were Women |journal=Technology and Culture |date=1999 |volume=40 |issue=3 |pages=455–483 |id={{Project MUSE|33396}} |doi=10.1353/tech.1999.0128 }}</ref><ref>{{cite journal |last1=Kiesler |first1=Sara |last2=Sproull |first2=Lee |last3=Eccles |first3=Jacquelynne S. |title=Pool Halls, Chips, and War Games: Women in the Culture of Computing |journal=Psychology of Women Quarterly |date=December 1985 |volume=9 |issue=4 |pages=451–462 |doi=10.1111/j.1471-6402.1985.tb00895.x }}</ref><ref>{{cite journal |last1=Fritz |first1=W.B. |title=The women of ENIAC |journal=IEEE Annals of the History of Computing |date=Fall 1996 |volume=18 |issue=3 |pages=13–28 |doi=10.1109/85.511940 }}</ref><ref>{{cite journal |last1=Gürer |first1=Denise |title=Pioneering women in computer science |journal=ACM SIGCSE Bulletin |date=June 2002 |volume=34 |issue=2 |pages=175–180 |doi=10.1145/543812.543853 }}</ref> Some performed astronomical calculations for calendars, others ballistic tables for the military.{{Sfn|Grier|2013|p=138}}

After the 1920s, the expression ''computing machine'' referred to any machine that performed the work of a human computer, especially those in accordance with effective methods of the [[Church-Turing thesis]]. The thesis states that a mathematical method is effective if it could be set out as a list of instructions able to be followed by a human clerk with paper and pencil, for as long as necessary, and without ingenuity or insight.

Machines that computed with continuous values became known as the ''analog'' kind. They used machinery that represented continuous numeric quantities, like the angle of a shaft rotation or difference in electrical potential.

Digital machinery, in contrast to analog, were able to render a state of a numeric value and store each individual digit. Digital machinery used difference engines or relays before the invention of faster memory devices.

The phrase ''computing machine'' gradually gave way, after the late 1940s, to just ''computer'' as the onset of electronic digital machinery became common. These computers were able to perform the calculations that were performed by the previous human clerks.

Since the values stored by digital machines were not bound to physical properties like analog devices, a logical computer, based on digital equipment, was able to do anything that could be described "purely mechanical." The theoretical [[Turing Machine]], created by [[Alan Turing]], is a hypothetical device theorized in order to study the properties of such hardware.

The mathematical foundations of modern computer science began to be laid by [[Kurt Gödel]] with his [[Gödel's incompleteness theorems|incompleteness theorem]] (1931). In this theorem, he showed that there were limits to what could be proved and disproved within a [[formal system]]. This led to work by Gödel and others to define and describe these formal systems, including concepts such as [[mu-recursive function]]s and [[lambda-definable functions]].<ref>{{Cite web|title=Gödel and the limits of logic|url=https://plus.maths.org/content/goumldel-and-limits-logic|date=2006-06-01|website=plus.maths.org|language=en|access-date=2020-05-01}}</ref>

In 1936  Alan Turing and [[Alonzo Church]] independently, and also together, introduced the formalization of an [[algorithm]], with limits on what can be computed, and a "purely mechanical" model for computing.<ref name="church-turing-thesis">{{cite encyclopedia|last=Copeland|first=B. Jack|title=The Church-Turing Thesis|date=2019|url=https://plato.stanford.edu/archives/spr2019/entries/church-turing/|encyclopedia=Stanford Encyclopedia of Philosophy|editor-last=Zalta|editor-first=Edward N.|edition=Spring 2019|publisher=Metaphysics Research Lab, Stanford University|access-date=2020-05-01}}</ref> This became the [[Church–Turing thesis]], a hypothesis about the nature of mechanical calculation devices, such as electronic computers. The thesis states that any calculation that is possible can be performed by an algorithm running on a computer, provided that sufficient time and storage space are available.<ref name="church-turing-thesis" />

In 1936, [[Alan Turing]] also published his seminal work on the [[Turing machine]]s, an abstract digital computing machine which is now simply referred to as the [[Universal Turing machine]]. This machine invented the principle of the modern computer and was the birthplace of the [[stored program]] concept that almost all modern day computers use.<ref name="plato.stanford.edu">{{cite encyclopedia|section-url=http://plato.stanford.edu/entries/computing-history/#ACE|section=Turing's Automatic Computing Engine|title=The Modern History of Computing|encyclopedia=Stanford Encyclopedia of Philosophy|publisher=Metaphysics Research Lab, Stanford University|year=2017}}</ref> These hypothetical machines were designed to formally determine, mathematically, what can be computed, taking into account limitations on computing ability. If a Turing machine can complete the task, it is considered [[Turing computable]].<ref name="Turing – Stanford" />

The [[Los Alamos National Laboratory|Los Alamos]] physicist [[Stanley Frankel]], has described [[John von Neumann]]'s view of the fundamental importance of Turing's 1936 paper, in a letter:<ref name="plato.stanford.edu" />

{{quote| I know that in or about 1943 or ‘44 von Neumann was well aware of the fundamental importance of Turing's paper of 1936… Von Neumann introduced me to that paper and at his urging I studied it with care. Many people have acclaimed von Neumann as the "father of the computer" (in a modern sense of the term) but I am sure that he would never have made that mistake himself. He might well be called the midwife, perhaps, but he firmly emphasized to me, and to others I am sure, that the fundamental conception is owing to Turing...}}
[[File:ATANASOFF Pic^5 - Flickr - Eye Steel Film.jpg|thumb|255x255px|[[John Vincent Atanasoff|John V. Atanasoff]] (1903–1995) created the first electric digital computer, known as the [[Atanasoff–Berry computer]]]]

=== Kathleen Booth and the first assembly language ===

[[Kathleen Booth]] wrote the first [[assembly language]] and designed the assembler and autocode for the [[Automatic Relay Calculator]] (ARC) at [[Birkbeck, University of London|Birkbeck College, University of London]].<ref>{{Citation |last=Booth|first=Kathleen HV |title= Machine language for Automatic Relay Computer|work= Birkbeck College Computation Laboratory |publisher=University of London}}</ref> She helped design three different machines including the ARC, SEC ([[Simple Electronic Computer]]), and [[APEXC|APE(X)C]].

=== Early computer hardware ===
The world's first electronic digital computer, the [[Atanasoff–Berry computer]], was built on the Iowa State campus from 1939 through 1942 by [[John Vincent Atanasoff|John V. Atanasoff]], a professor of physics and mathematics, and [[Clifford Berry]], an engineering graduate student.

[[File:Konrad Zuse (1992).jpg|thumb|left|177x177px|[[Konrad Zuse]], inventor of the modern computer<ref name=Bellis>{{cite web |url=https://www.thoughtco.com/konrad-zuse-modern-computer-4078237 |title=Biography of Konrad Zuse, Inventor and Programmer of Early Computers |last=Bellis |first=Mary |date=15 May 2019 |orig-date=First published 2006 at inventors.about.com/library/weekly/aa050298.htm |website=thoughtco.com |publisher=Dotdash Meredith |access-date=3 February 2021 |url-status=live |archive-url=https://web.archive.org/web/20201213003237/https://www.thoughtco.com/konrad-zuse-modern-computer-4078237 |archive-date=13 December 2020 |quote=Konrad Zuse earned the semiofficial title of 'inventor of the modern computer'{{who|date=February 2023}}}}</ref><ref>{{Cite web|url=https://www.computerhope.com/issues/ch001335.htm|title=Who is the Father of the Computer?|website=ComputerHope}}</ref>]]
In 1941, [[Konrad Zuse]] developed the world's first functional program-controlled computer, the [[Z3 (computer)|Z3]]. In 1998, it was shown to be [[Turing completeness|Turing-complete]] in principle.<ref>{{cite journal|last=Rojas |first=R. |title=How to make Zuse's Z3 a universal computer |journal=IEEE Annals of the History of Computing |volume=20 |issue=3 |pages=51–54 |year=1998 |doi=10.1109/85.707574 |author-link=Raúl Rojas }}</ref><ref>{{cite web |url=http://www.zib.de/zuse/Inhalt/Kommentare/Html/0684/universal2.html |title=How to Make Zuse's Z3 a Universal Computer |first=Raúl |last=Rojas |url-status=dead |archive-url=https://web.archive.org/web/20140714224748/http://www.zib.de/zuse/Inhalt/Kommentare/Html/0684/universal2.html |archive-date=2014-07-14 }}</ref> Zuse also developed the S2 computing machine, considered the first [[process control]] computer. He founded one of the earliest computer businesses in 1941, producing the [[Z4 (computer)|Z4]], which became the world's first commercial computer.  In 1946, he designed the first [[high-level programming language]], [[Plankalkül]].<ref name="HZ2010-11-18">Talk given by [[Horst Zuse]] to the [[Computer Conservation Society]] at the [[Science Museum (London)]] on 18 November 2010</ref>

In 1948, the [[Manchester Baby]] was completed; it was the world's first electronic digital computer that ran programs stored in its memory, like almost all modern computers.<ref name="plato.stanford.edu" /> The influence on [[Max Newman]] of Turing's seminal 1936 paper on the [[Turing Machines]] and of his logico-mathematical contributions to the project, were both crucial to the successful development of the Baby.<ref name="plato.stanford.edu" />

In 1950, Britain's [[National Physical Laboratory, UK|National Physical Laboratory]] completed [[Pilot ACE]], a small scale programmable computer, based on Turing's philosophy. With an operating speed of 1&nbsp;MHz, the Pilot Model ACE was for some time the fastest computer in the world.<ref name="plato.stanford.edu" /><ref>{{cite news|url=http://news.bbc.co.uk/2/hi/technology/8683369.stm|title=BBC News – How Alan Turing's Pilot ACE changed computing|date=May 15, 2010|newspaper=BBC News}}</ref> Turing's design for [[Automatic Computing Engine|ACE]] had much in common with today's [[RISC]] architectures and it called for a high-speed memory of roughly the same capacity as an early [[Macintosh]] computer, which was enormous by the standards of his day.<ref name="plato.stanford.edu" /> Had Turing's ACE been built as planned and in full, it would have been in a different league from the other early computers.<ref name="plato.stanford.edu" />

Later in the 1950s, the first [[operating system]], [[GM-NAA I/O]], supporting [[batch processing]] to allow jobs to be run with less operator intervention, was developed by [[General Motors]] and [[North American Aviation]] for the [[IBM 701]].

In 1969, an experiment was conducted by two research teams at UCLA and Stanford to create a network between 2 computers although the system crashed during the initial attempt to connect to the other computer but was a huge step towards the Internet.
[[File:C.E. Shannon. Tekniska museet 43069.jpg|left|thumb|177x177px|[[Claude Shannon]] (1916–2001) created the field of [[information theory]]]]
The first actual computer bug was a [[moth]]. It was stuck in between the relays on the Harvard Mark II.<ref name="mark-ii-bug">{{cite journal|url=https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=3489|title=The First "Computer Bug"|page=18|journal=CHIPS|volume=30|issue=1|date=January–March 2012|publisher=United States Navy|access-date=2023-12-03}}</ref>
While the invention of the term 'bug' is often but erroneously attributed to [[Grace Hopper]], a future rear admiral in the U.S. Navy, who supposedly logged the "bug" on September 9, 1945, most other accounts conflict at least with these details. According to these accounts, the actual date was September 9, 1947 when operators filed this 'incident' — along with the insect and the notation "First actual case of bug being found" (see [[software bug]] for details).<ref name="mark-ii-bug" />

=== Shannon and information theory ===
[[Claude Shannon]] went on to found the field of [[information theory]] with his 1948 paper titled [[A Mathematical Theory of Communication]], which applied [[probability theory]] to the problem of how to best encode the information a sender wants to transmit.  This work is one of the theoretical foundations for many areas of study, including [[data compression]] and [[cryptography]].<ref>{{Cite book|last=Shannon|first=Claude Elwood|url=https://www.worldcat.org/oclc/2654027|title=The mathematical theory of communication|date=1964|publisher=University of Illinois Press|others=Warren Weaver|isbn=0-252-72548-4|location=Urbana|oclc=2654027}}</ref>
[[File:Norbert Wiener.png|thumb|165x165px|[[Norbert Wiener]] (1894–1964) created the term [[cybernetics]]]]

=== Wiener and cybernetics ===
From experiments with anti-aircraft systems that interpreted radar images to detect enemy planes, [[Norbert Wiener]] coined the term [[cybernetics]] from the Greek word for "steersman." He published "Cybernetics" in 1948, which influenced [[artificial intelligence]]. Wiener also compared [[computation]], computing machinery, [[computer memory|memory]] devices, and other cognitive similarities with his analysis of brain waves.<ref>{{Cite journal|last1=Xiong|first1=Aiping|last2=Proctor|first2=Robert W.|date=2018|title=Information Processing: The Language and Analytical Tools for Cognitive Psychology in the Information Age|journal=Frontiers in Psychology |volume=9|page=1270|doi=10.3389/fpsyg.2018.01270|pmid=30135664|pmc=6092626 |doi-access=free}}</ref>
[[File:JohnvonNeumann-LosAlamos.gif|left|thumb|260x260px|[[John von Neumann]] (1903–1957) introduced the computer architecture known as [[Von Neumann architecture]]]]

=== John von Neumann and the von Neumann architecture ===
{{Main|John von Neumann|Von Neumann architecture}}
In 1946, a model for computer architecture was introduced and became known as ''[[Von Neumann architecture]]''. Since 1950, the von Neumann model provided uniformity in subsequent computer designs. The von Neumann architecture was considered innovative as it introduced an idea of allowing machine instructions and data to share memory space.{{fact|date=March 2025}} The von Neumann model is composed of three major parts, the arithmetic logic unit (ALU), the memory, and the instruction processing unit (IPU). In von Neumann machine design, the IPU passes addresses to memory, and memory, in turn, is routed either back to the IPU if an instruction is being fetched or to the ALU if data is being fetched.<ref name="Von Neumann" />

Von Neumann's machine design uses a RISC (Reduced instruction set computing) architecture,{{dubious|reason=neologism, reduced from what?|date=April 2014}} which means the instruction set uses a total of 21 instructions to perform all tasks. (This is in contrast to CISC, [[complex instruction set computing]], instruction sets which have more instructions from which to choose.)  With von Neumann architecture, main memory along with the accumulator (the register that holds the result of logical operations)<ref name="Dictionary" /> are the two memories that are addressed. Operations can be carried out as simple arithmetic (these are performed by the ALU and include addition, subtraction, multiplication and division), conditional branches (these are more commonly seen now as <code>if</code> statements or <code>while</code> loops. The branches serve as <code>go to</code> statements), and logical moves between the different components of the machine, i.e., a move from the accumulator to memory or vice versa. Von Neumann architecture accepts fractions and instructions as data types. Finally, as the von Neumann architecture is a simple one, its register management is also simple. The architecture uses a set of seven registers to manipulate and interpret fetched data and instructions. These registers include the "IR" (instruction register), "IBR" (instruction buffer register), "MQ" (multiplier quotient register), "MAR" (memory address register), and "MDR" (memory data register)."<ref name="Von Neumann" />  The architecture also uses a program counter ("PC") to keep track of where in the program the machine is.<ref name="Von Neumann" />
[[File:John McCarthy Stanford.jpg|thumb|[[John McCarthy (computer scientist)|John McCarthy]] (1927–2011) is considered one of the founding fathers of [[artificial intelligence]]]]

=== John McCarthy, Marvin Minsky and artificial intelligence ===
{{Main|John McCarthy (computer scientist)|Marvin Minsky|Artificial intelligence}}
The term artificial intelligence was credited by John McCarthy to explain the research that they were doing for a proposal for the [[Dartmouth Summer Research Project on Artificial Intelligence|Dartmouth Summer Research]]. The naming of artificial intelligence also led to the birth of a new field in computer science.<ref>{{cite journal |last1=Moor |first1=James |title=The Dartmouth College Artificial Intelligence Conference: The Next Fifty Years |journal=AI Magazine |date=15 December 2006 |volume=27 |issue=4 |pages=87–91 |id={{ProQuest|208119658}} |url=https://ojs.aaai.org/aimagazine/index.php/aimagazine/article/view/1911 }}</ref> On August 31, 1955, a research project was proposed consisting of John McCarthy, Marvin L. Minsky, [[Nathaniel Rochester (computer scientist)|Nathaniel Rochester]], and [[Claude Shannon|Claude E. Shannon]]. The official project began in 1956 that consisted of several significant parts they felt would help them better understand artificial intelligence's makeup.

McCarthy and his colleagues' ideas behind automatic computers was while a machine is capable of completing a task, then the same should be confirmed with a computer by compiling a [[Computer program|program]] to perform the desired results. They also discovered that the human brain was too complex to replicate, not by the machine itself but by the program. The knowledge to produce a program that sophisticated was not there yet.

The concept behind this was looking at how humans understand our own language and structure of how we form sentences, giving different meaning and rule sets and comparing them to a machine process. The way computers can understand is at a hardware level. This language is written in [[Binary number|binary]] (1s and 0's). This has to be written in a specific format that gives the computer the ruleset to run a particular hardware piece.<ref>{{Cite book|last=Prudhomme|first=Gerard|url=http://worldcat.org/oclc/1089398724|title=Introduction to Assembly Language Programming|date=December 2018|publisher=Arcler Education Incorporated |isbn=978-1-77361-470-0|oclc=1089398724}}</ref>

Minsky's process determined how these [[Artificial neural network|artificial neural networks]] could be arranged to have similar qualities to the human brain. However, he could only produce partial results and needed to further the research into this idea.

McCarthy and Shannon's idea behind this theory was to develop a way to use complex problems to determine and measure the machine's efficiency through [[A Mathematical Theory of Communication|mathematical theory]] and [[Computational complexity theory|computations]].<ref>{{Cite book|first1=John|last1=McCarthy|author-link1=John McCarthy (computer scientist)|first2=Vladimir|last2=Lifschitz|author-link2=Vladimir Lifschitz|url=http://worldcat.org/oclc/911282256|title=Artificial intelligence and mathematical theory of computation : papers in honor of John McCarthy|date=1991|publisher=Academic Press|isbn=0-12-450010-2|oclc=911282256}}</ref> However, they were only to receive partial test results.

The idea behind self-improvement is how a machine would use [[self-modifying code]] to make itself smarter. This would allow for a machine to grow in intelligence and increase calculation speeds.<ref>{{cite journal |last1=Haenlein |first1=Michael |last2=Kaplan |first2=Andreas |title=A Brief History of Artificial Intelligence: On the Past, Present, and Future of Artificial Intelligence |journal=California Management Review |date=August 2019 |volume=61 |issue=4 |pages=5–14 |doi=10.1177/0008125619864925 }}</ref> The group believed they could study this if a machine could improve upon the process of completing a task in the abstractions part of their research.

The group thought that research in this category could be broken down into smaller groups. This would consist of sensory and other forms of information about artificial intelligence. [[Abstraction (computer science)|Abstractions]] in computer science can refer to mathematics and programming language.<ref>{{cite book |doi=10.1007/978-3-642-33475-7 |title=Theoretical Computer Science |series=Lecture Notes in Computer Science |date=2012 |volume=7604 |isbn=978-3-642-33474-0 |editor1-first=Jos C. M. |editor1-last=Baeten |editor2-first=Tom |editor2-last=Ball |editor3-first=Frank S. |editor3-last=Boer }}{{pn|date=March 2025}}</ref>

Their idea of [[computational creativity]] is how the program or a machine can be seen in having similar ways of human thinking.<ref>{{Cite web|title=The Creativity Post {{!}} What is Computational Creativity?|url=https://www.creativitypost.com/article/what_is_computational_creativity|access-date=2021-03-04|website=The Creativity Post|language=en-US}}</ref> They wanted to see if a machine could take a piece of incomplete information and improve upon it to fill in the missing details as the human mind can do. If this machine could do this; they needed to think of how did the machine determine the outcome.

== See also ==
* [[Computer museum]]
* [[List of computer term etymologies]], the origins of computer science words
* [[List of pioneers in computer science]]
* [[History of computing]]
* [[History of computing hardware]]
* [[History of software]]
* [[History of personal computers]]
* [[Timeline of algorithms]]
* [[Timeline of women in computing]]
* [[Timeline of computing 2020–present]]

== References ==
{{reflist | refs =
<ref name="Turing – Stanford">{{cite encyclopedia|last=Barker-Plummer|first=David|title=Turing Machines|url=http://plato.stanford.edu/archives/win2012/entries/turing-machine/|encyclopedia=Stanford Encyclopedia of Philosophy|access-date=2013-02-20|date=1995-09-14}}</ref>

<ref name="Von Neumann">{{cite book|last=Cragon|first=Harvey G.|title=Computer Architecture and Implementation|url=https://archive.org/details/computerarchitec00crag_064|url-access=limited|year=2000|publisher=Cambridge University Press|location=Cambridge|isbn=978-0-521-65168-4|pages=[https://archive.org/details/computerarchitec00crag_064/page/n10 1]–13}}</ref>

<ref name=Dictionary>{{cite book|title="Accumlator" Def. 3|publisher=Oxford Dictionaries|url=http://oxforddictionaries.com/definition/english/accumulator?q=accumulator|archive-url=https://web.archive.org/web/20130518200133/http://oxforddictionaries.com/definition/english/accumulator?q=accumulator|url-status=dead|archive-date=May 18, 2013}}</ref>

<ref name="Ada Lovelace">{{cite news|last=Isaacson|first=Betsy|title=Ada Lovelace, World's First Computer Programmer, Celebrated With Google Doodle|url=http://www.huffingtonpost.com/2012/12/10/google-doodle-ada-lovelace_n_2270668.html|work=The Huffington Post|access-date=2013-02-20|date=2012-12-10}}</ref>

<ref name="Charles Babbage">{{cite encyclopedia|title=Charles Babbage|url=https://www.britannica.com/biography/Charles-Babbage|encyclopedia=Encyclopædia Britannica Online Academic Edition|date=3 July 2023 |publisher=Encyclopædia Britannica In.|access-date=2023-07-06}}</ref>
}}

=== Sources ===

* {{Cite book|url=https://books.google.com/books?id=C8ouDwAAQBAJ&q=9780735211759&pg=PP1|title=Broad Band: The Untold Story of the Women Who Made the Internet|last=Evans|first=Claire L.|publisher=Portfolio/Penguin|year=2018|isbn=9780735211759|location=New York}}
*{{Cite book|url=https://archive.org/details/whencomputerswer00davi|title=When Computers Were Human|last=Grier|first=David Alan|publisher=Princeton University Press|year=2013|isbn=9781400849369|location=Princeton|url-access=subscription|via=Project MUSE}}

== Further reading ==
* {{cite book |last=Tedre |first=Matti |date=2014 |title=The Science of Computing: Shaping a Discipline |publisher=Taylor and Francis / CRC Press |isbn=978-1-4822-1769-8}}
* Kak, Subhash : Computing Science in Ancient India; Munshiram Manoharlal Publishers Pvt. Ltd (2001)
* [http://cs.joensuu.fi/pub/Dissertations/tedre.pdf The Development of Computer Science: A Sociocultural Perspective] Matti Tedre's Ph.D. Thesis, University of Joensuu (2006)
* {{cite book |last=Ceruzzi |first=Paul E. |author-link=Paul E. Ceruzzi |title=A History of a Modern Computing |date=1998 |publisher=The MIT Press |isbn=978-0-262-03255-1 |url=https://archive.org/details/historyofmodernc00ceru }}
* {{cite SEP |url-id=computing-history |title=The Modern History of Computing |last=Copeland |first=B. Jack}}

==External links==
{{Commonscat}}
*[http://www.computerhistory.org/ Computer History Museum]
*[http://www.eingang.org/Lecture/ Computers: From the Past to the Present]
*[https://www.history.navy.mil/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/NH-96000/NH-96566-KN.html The First "Computer Bug"] at the Naval History and Heritage Command Photo Archives.
*[http://www.bitsavers.org/ Bitsavers], an effort to capture, salvage, and archive historical computer software and manuals from minicomputers and mainframes of the 1950s, 1960s, 1970s, and 1980s
*[https://conservancy.umn.edu/handle/11299/59493 Oral history interviews]

[[Category:History of computer science| ]]
[[Category:History of science by discipline|Computer science]]
[[Category:History of computing]]