Editing History of computing hardware (section)

==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 built with 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> The Z3 was proven to have been a [[Turing machine|Turing-complete machine]] in 1998 by [[Raúl Rojas]].<ref>{{Cite book|last=Rojas|first=Raúl|title=How to Make Zuse's Z3 a Universal Computer |date=1998 |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/1/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.