Thehistory of computer science began long before the modern discipline ofcomputer science, usually appearing in forms likemathematics orphysics. Developments in previous centuries alluded to the discipline that we now know as computer science.^[1] This progression, from mechanical inventions andmathematical theories towardsmodern computer concepts and machines, led to the development of a majoracademic field, massive technological advancement across theWestern world, and the basis of massive worldwide trade and culture.^[2]

The earliest known tool for use in computation was theabacus, developed in the period between 2700 and 2300 BCE inSumer.^[3] The Sumerians' abacus consisted of a table of successive columns which delimited the successiveorders of magnitude of theirsexagesimal number system.^[4]: 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 theChinese abacus.^[5]

In the 5th century BC inancient India, thegrammarianPāṇini formulated thegrammar ofSanskrit in 3959 rules known as theAshtadhyayi which was highly systematized and technical. Panini used metarules,transformations andrecursions.^[6]

TheAntikythera mechanism is believed to be an early mechanical analog computer.^[7] It was designed to calculate astronomical positions. It was discovered in 1901 in theAntikythera wreck off the Greek island of Antikythera, betweenKythera andCrete, and has been dated tocirca 100 BC.^[7]

Mechanical analog computer devices appeared again a thousand years later in themedieval Islamic world. They were developed byMuslim astronomers, such as the mechanical gearedastrolabe byAbū Rayhān al-Bīrūnī,^[8] and thetorquetum byJabir ibn Aflah.^[9] According toSimon Singh,Muslim mathematicians also made important advances incryptography, such as the development ofcryptanalysis andfrequency analysis byAlkindus.^[10][11]Programmable machines were also invented byMuslim engineers, such as the automaticflute player by theBanū Mūsā brothers.^[12]

Technological artifacts of similar complexity appeared in 14th centuryEurope, with mechanicalastronomical clocks.^[13]

WhenJohn Napier discoveredlogarithms for computational purposes in the early 17th century,^[14] there followed a period of considerable progress by inventors and scientists in making calculating tools. In 1623Wilhelm Schickard designed the calculating machine as a commission forJohannes 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.^[15] Around 1640,Blaise Pascal, a leading French mathematician, constructed a mechanical adding device based on a design described byGreek mathematicianHero of Alexandria.^[16] Then in 1672Gottfried Wilhelm Leibniz invented theStepped Reckoner which he completed in 1694.^[17]

In 1837Charles Babbage first described hisAnalytical 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 aprogramming language with loops and conditional branching. Although never built, the design has been studied extensively and is understood to beTuring equivalent. The analytical engine would have had a memory capacity of less than 1kilobyte of memory and aclock speed of less than 10Hertz.^[18]

Considerable advancement in mathematics andelectronics theory was required before the first modern computers could be designed.

In 1702,Gottfried Wilhelm Leibniz developedlogic 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.^[20] He anticipatedLagrangian interpolation andalgorithmic information theory. Hiscalculus ratiocinator anticipated aspects of theuniversal Turing machine. In 1961,Norbert Wiener suggested that Leibniz should be considered the patron saint ofcybernetics.^[21] Wiener is quoted with "Indeed, the general idea of a computing machine is nothing but a mechanization of Leibniz's Calculus Ratiocinator."^[22] But it took more than a century beforeGeorge Boole published hisBoolean algebra in 1854 with a complete system that allowed computational processes to be mathematically modeled.^[23]

By this time, the first mechanical devices driven by a binary pattern had been invented. TheIndustrial Revolution had driven forward the mechanization of many tasks, and this includedweaving.Punched cards controlledJoseph Marie Jacquard's loom in 1801, where a hole punched in the card indicated a binaryone and an unpunched spot indicated a binaryzero. 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.^[23]

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.^[24]

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.^[25] During her work with Babbage, Ada Lovelace became the designer of the first computer algorithm, which could computeBernoulli numbers,^[26] 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.^[27] 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.^[28]

Following Babbage, although at first unaware of his earlier work, wasPercy 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.^[29][30]

Two other inventors,Leonardo Torres Quevedo andVannevar Bush, also did follow on research based on Babbage's work. In hisEssays on Automatics (1914), Torres designed an analytical electromechanical machine that was controlled by aread-only program and introduced the idea offloating-point arithmetic.^[31][32][33] In 1920, to celebrate the 100th anniversary of the invention of thearithmometer, he presented in Paris the 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.^[34] Bush's paperInstrumental 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.^[35]

In an 1886 letter,Charles Sanders Peirce described how logical operations could be carried out by electrical switching circuits.^[36] During 1880–81 he showed thatNOR gates alone (or alternativelyNAND gates alone) can be used to reproduce the functions of all the otherlogic gates, but this work on it was unpublished until 1933.^[37] The first published proof was byHenry M. Sheffer in 1913, so the NAND logical operation is sometimes calledSheffer stroke; thelogical NOR is sometimes calledPeirce's arrow.^[38] Consequently, these gates are sometimes calleduniversal logic gates.^[39]

Eventually,vacuum tubes replaced relays for logic operations.Lee De Forest's modification, in 1907, of theFleming valve can be used as a logic gate.Ludwig Wittgenstein introduced a version of the 16-rowtruth table as proposition 5.101 ofTractatus Logico-Philosophicus (1921).Walther Bothe, inventor of thecoincidence circuit, got part of the 1954Nobel Prize in physics, for the first modern electronic AND gate in 1924.Konrad Zuse designed and built electromechanical logic gates for his computerZ1 (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 anad hoc manner, lacking any theoretical rigor. This changed withswitching circuit theory in the 1930s. From 1934 to 1936,Akira Nakashima,Claude Shannon, and Viktor Shetakov published a series of papers showing that thetwo-valuedBoolean algebra, can describe the operation of switching circuits.^{[40][41][42][43]} This concept, of utilizing the properties of electrical switches to do logic, is the basic concept that underlies all electronicdigital computers. Switching circuit theory provided the mathematical foundations and tools fordigital system design in almost all areas of modern technology.^[43]

While taking an undergraduate philosophy class, Shannon had been exposed toBoole'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.^[44]

Before the 1920s,computers (sometimescomputors) 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.^{[45][46][47][48]} Some performed astronomical calculations for calendars, others ballistic tables for the military.^[49]

After the 1920s, the expressioncomputing machine referred to any machine that performed the work of a human computer, especially those in accordance with effective methods of theChurch-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 theanalog 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 phrasecomputing machine gradually gave way, after the late 1940s, to justcomputer 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 theoreticalTuring Machine, created byAlan 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 byKurt Gödel with hisincompleteness theorem (1931). In this theorem, he showed that there were limits to what could be proved and disproved within aformal system. This led to work by Gödel and others to define and describe these formal systems, including concepts such asmu-recursive functions andlambda-definable functions.^[50]

In 1936 Alan Turing andAlonzo Church independently, and also together, introduced the formalization of analgorithm, with limits on what can be computed, and a "purely mechanical" model for computing.^[51] This became theChurch–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.^[51]

In 1936,Alan Turing also published his seminal work on theTuring machines, an abstract digital computing machine which is now simply referred to as theUniversal Turing machine. This machine invented the principle of the modern computer and was the birthplace of thestored program concept that almost all modern day computers use.^[52] 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 consideredTuring computable.^[53]

TheLos Alamos physicistStanley Frankel, has describedJohn von Neumann's view of the fundamental importance of Turing's 1936 paper, in a letter:^[52]

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...

Kathleen Booth wrote the firstassembly language and designed the assembler and autocode for theAutomatic Relay Calculator (ARC) atBirkbeck College, University of London.^[54] She helped design three different machines including the ARC, SEC (Simple Electronic Computer), andAPE(X)C.

The world's first electronic digital computer, theAtanasoff–Berry computer, was built on the Iowa State campus from 1939 through 1942 byJohn V. Atanasoff, a professor of physics and mathematics, andClifford Berry, an engineering graduate student.

In 1941,Konrad Zuse developed the world's first functional program-controlled computer, theZ3. In 1998, it was shown to beTuring-complete in principle.^[57][58] Zuse also developed the S2 computing machine, considered the firstprocess control computer. He founded one of the earliest computer businesses in 1941, producing theZ4, which became the world's first commercial computer. In 1946, he designed the firsthigh-level programming language,Plankalkül.^[59]

In 1948, theManchester Baby was completed; it was the world's first electronic digital computer that ran programs stored in its memory, like almost all modern computers.^[52] The influence onMax Newman of Turing's seminal 1936 paper on theTuring Machines and of his logico-mathematical contributions to the project, were both crucial to the successful development of the Baby.^[52]

In 1950, Britain'sNational Physical Laboratory completedPilot ACE, a small scale programmable computer, based on Turing's philosophy. With an operating speed of 1 MHz, the Pilot Model ACE was for some time the fastest computer in the world.^[52][60] Turing's design forACE had much in common with today'sRISC architectures and it called for a high-speed memory of roughly the same capacity as an earlyMacintosh computer, which was enormous by the standards of his day.^[52] Had Turing's ACE been built as planned and in full, it would have been in a different league from the other early computers.^[52]

Later in the 1950s, the firstoperating system,GM-NAA I/O, supportingbatch processing to allow jobs to be run with less operator intervention, was developed byGeneral Motors andNorth American Aviation for theIBM 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.

The first actual computer bug was amoth. It was stuck in between the relays on the Harvard Mark II.^[61]While the invention of the term 'bug' is often but erroneously attributed toGrace 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" (seesoftware bug for details).^[61]

Claude Shannon went on to found the field ofinformation theory with his 1948 paper titledA Mathematical Theory of Communication, which appliedprobability 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, includingdata compression andcryptography.^[62]

From experiments with anti-aircraft systems that interpreted radar images to detect enemy planes,Norbert Wiener coined the termcybernetics from the Greek word for "steersman." He published "Cybernetics" in 1948, which influencedartificial intelligence. Wiener also comparedcomputation, computing machinery,memory devices, and other cognitive similarities with his analysis of brain waves.^[63]

In 1946, a model for computer architecture was introduced and became known asVon 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.^{[citation needed]} 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.^[64]

Von Neumann's machine design uses a RISC (Reduced instruction set computing) architecture,^{[dubious –discuss]} 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)^[65] 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 asif statements orwhile loops. The branches serve asgo to 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)."^[64] The architecture also uses a program counter ("PC") to keep track of where in the program the machine is.^[64]

The term artificial intelligence was credited by John McCarthy to explain the research that they were doing for a proposal for theDartmouth Summer Research. The naming of artificial intelligence also led to the birth of a new field in computer science.^[66] On August 31, 1955, a research project was proposed consisting of John McCarthy, Marvin L. Minsky,Nathaniel Rochester, andClaude 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 aprogram 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 inbinary (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.^[67]

Minsky's process determined how theseartificial 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 throughmathematical theory andcomputations.^[68] However, they were only to receive partial test results.

The idea behind self-improvement is how a machine would useself-modifying code to make itself smarter. This would allow for a machine to grow in intelligence and increase calculation speeds.^[69] 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.Abstractions in computer science can refer to mathematics and programming language.^[70]

Their idea ofcomputational creativity is how the program or a machine can be seen in having similar ways of human thinking.^[71] 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.

• 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

• Evans, Claire L. (2018).Broad Band: The Untold Story of the Women Who Made the Internet. New York: Portfolio/Penguin.ISBN 9780735211759.
• Grier, David Alan (2013).When Computers Were Human. Princeton: Princeton University Press.ISBN 9781400849369 – via Project MUSE.

• Tedre, Matti (2014).The Science of Computing: Shaping a Discipline. Taylor and Francis / CRC Press.ISBN 978-1-4822-1769-8.
• Kak, Subhash : Computing Science in Ancient India; Munshiram Manoharlal Publishers Pvt. Ltd (2001)
• The Development of Computer Science: A Sociocultural Perspective Matti Tedre's Ph.D. Thesis, University of Joensuu (2006)
• Ceruzzi, Paul E. (1998).A History of a Modern Computing. The MIT Press.ISBN 978-0-262-03255-1.
• Copeland, B. Jack."The Modern History of Computing". InZalta, Edward N. (ed.).Stanford Encyclopedia of Philosophy.ISSN 1095-5054.OCLC 429049174.

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• Oral history interviews

• History of computer science
• History of science by discipline
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