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History of computing hardware

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   From early calculation aids to modern day computers

   Computing hardware is a platform for information processing.
   History of computing
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     * Hardware before 1960
     * Hardware 1960s to present

     * Software
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   Computer science
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   By country
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   Timeline of computing
     * before 1950
     * 1950-1979
     * 1980-1989
     * 1990-1999
     * 2000-2009
     * 2010-2019
     * 2020-present
     * more timelines ...

   Glossary of computer science
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   Parts from four early computers, 1962. From left to right: ENIAC board,
   EDVAC board, ORDVAC board, and BRLESC-I board, showing the trend toward

   The history of computing hardware covers the developments from early
   simple devices to aid calculation to modern day computers. Before the
   20th century, most calculations were done by humans.

   The first aids to computation were purely mechanical devices which
   required the operator to set up the initial values of an elementary
   arithmetic operation, then manipulate the device to obtain the result.
   Later, computers represented numbers in a continuous form (e.g.
   distance along a scale, rotation of a shaft, or a voltage). Numbers
   could also be represented in the form of digits, automatically
   manipulated by a mechanism. Although this approach generally required
   more complex mechanisms, it greatly increased the precision of results.
   The development of transistor technology and then the integrated
   circuit chip led to a series of breakthroughs, starting with transistor
   computers and then integrated circuit computers, causing digital
   computers to largely replace analog computers.
   Metal-oxide-semiconductor (MOS) large-scale integration (LSI) then
   enabled semiconductor memory and the microprocessor, leading to another
   key breakthrough, the miniaturized personal computer (PC), in the
   1970s. The cost of computers gradually became so low that personal
   computers by the 1990s, and then mobile computers (smartphones and
   tablets) in the 2000s, became ubiquitous.
   [ ]


     * 1 Early devices
          + 1.1 Ancient and medieval
          + 1.2 Renaissance calculating tools
          + 1.3 Mechanical calculators
          + 1.4 Punched-card data processing
          + 1.5 Calculators
     * 2 First general-purpose computing device
     * 3 Analog computers
     * 4 Advent of the digital computer
          + 4.1 Electromechanical computers
          + 4.2 Digital computation
          + 4.3 Electronic data processing
          + 4.4 The electronic programmable computer
     * 5 Stored-program computer
          + 5.1 Theory
          + 5.2 Manchester Baby
          + 5.3 Manchester Mark 1
          + 5.4 EDSAC
          + 5.5 EDVAC
          + 5.6 Commercial computers
          + 5.7 Microprogramming
     * 6 Magnetic memory
     * 7 Early digital computer characteristics
     * 8 Transistor computers
          + 8.1 Transistor peripherals
          + 8.2 Transistor supercomputers
     * 9 Integrated circuit computers
     * 10 Semiconductor memory
     * 11 Microprocessor computers
     * 12 Epilogue
     * 13 See also
     * 14 Notes
     * 15 References
     * 16 Further reading
     * 17 External links

Early devices[edit]

   See also: Timeline of computing hardware before 1950

Ancient and medieval[edit]

   The Ishango bone is thought to be a Paleolithic tally stick.^[a]
   Suanpan (the number represented on this abacus is 6,302,715,408)

   Devices have been used to aid computation for thousands of years,
   mostly using one-to-one correspondence with fingers. The earliest
   counting device was probably a form of tally stick. The Lebombo bone
   from the mountains between Eswatini and South Africa may be the oldest
   known mathematical artifact.^[2] It dates from 35,000 BCE and consists
   of 29 distinct notches that were deliberately cut into a baboon's
   fibula.^[3]^[4] Later record keeping aids throughout the Fertile
   Crescent included calculi (clay spheres, cones, etc.) which represented
   counts of items, probably livestock or grains, sealed in hollow unbaked
   clay containers.^[b]^[6]^[c] The use of counting rods is one example.
   The abacus was early used for arithmetic tasks. What we now call the
   Roman abacus was used in Babylonia as early as c. 2700-2300 BC. Since
   then, many other forms of reckoning boards or tables have been
   invented. In a medieval European counting house, a checkered cloth
   would be placed on a table, and markers moved around on it according to
   certain rules, as an aid to calculating sums of money.

   Several analog computers were constructed in ancient and medieval times
   to perform astronomical calculations. These included the astrolabe and
   Antikythera mechanism from the Hellenistic world (c. 150-100 BC).^[8]
   In Roman Egypt, Hero of Alexandria (c. 10-70 AD) made mechanical
   devices including automata and a programmable cart.^[9] Other early
   mechanical devices used to perform one or another type of calculations
   include the planisphere and other mechanical computing devices invented
   by Abu Rayhan al-Biruni (c. AD 1000); the equatorium and universal
   latitude-independent astrolabe by Abu Ishaq Ibrahim al-Zarqali (c. AD
   1015); the astronomical analog computers of other medieval Muslim
   astronomers and engineers; and the astronomical clock tower of Su Song
   (1094) during the Song dynasty. The castle clock, a hydropowered
   mechanical astronomical clock invented by Ismail al-Jazari in 1206, was
   the first programmable analog computer.^[disputed (for: The cited
   source doesn't support the claim, and the claim is misleading.)  -
   discuss]^[10]^[11]^[12] Ramon Llull invented the Lullian Circle: a
   notional machine for calculating answers to philosophical questions (in
   this case, to do with Christianity) via logical combinatorics. This
   idea was taken up by Leibniz centuries later, and is thus one of the
   founding elements in computing and information science.

Renaissance calculating tools[edit]

   Scottish mathematician and physicist John Napier discovered that the
   multiplication and division of numbers could be performed by the
   addition and subtraction, respectively, of the logarithms of those
   numbers. While producing the first logarithmic tables, Napier needed to
   perform many tedious multiplications. It was at this point that he
   designed his 'Napier's bones', an abacus-like device that greatly
   simplified calculations that involved multiplication and division.^[d]
   A modern slide rule

   Since real numbers can be represented as distances or intervals on a
   line, the slide rule was invented in the 1620s, shortly after Napier's
   work, to allow multiplication and division operations to be carried out
   significantly faster than was previously possible.^[13] Edmund Gunter
   built a calculating device with a single logarithmic scale at the
   University of Oxford. His device greatly simplified arithmetic
   calculations, including multiplication and division. William Oughtred
   greatly improved this in 1630 with his circular slide rule. He followed
   this up with the modern slide rule in 1632, essentially a combination
   of two Gunter rules, held together with the hands. Slide rules were
   used by generations of engineers and other mathematically involved
   professional workers, until the invention of the pocket

Mechanical calculators[edit]

   Wilhelm Schickard, a German polymath, designed a calculating machine in
   1623 which combined a mechanized form of Napier's rods with the world's
   first mechanical adding machine built into the base. Because it made
   use of a single-tooth gear there were circumstances in which its carry
   mechanism would jam.^[15] A fire destroyed at least one of the machines
   in 1624 and it is believed Schickard was too disheartened to build
   View through the back of Pascal's calculator. Pascal invented his
   machine in 1642.

   In 1642, while still a teenager, Blaise Pascal started some pioneering
   work on calculating machines and after three years of effort and 50
   prototypes^[16] he invented a mechanical calculator.^[17]^[18] He built
   twenty of these machines (called Pascal's calculator or Pascaline) in
   the following ten years.^[19] Nine Pascalines have survived, most of
   which are on display in European museums.^[20] A continuing debate
   exists over whether Schickard or Pascal should be regarded as the
   "inventor of the mechanical calculator" and the range of issues to be
   considered is discussed elsewhere.^[21]
   A set of John Napier's calculating tables from around 1680

   Gottfried Wilhelm von Leibniz invented the stepped reckoner and his
   famous stepped drum mechanism around 1672. He attempted to create a
   machine that could be used not only for addition and subtraction but
   would utilise a moveable carriage to enable long multiplication and
   division. Leibniz once said "It is unworthy of excellent men to lose
   hours like slaves in the labour of calculation which could safely be
   relegated to anyone else if machines were used."^[22] However, Leibniz
   did not incorporate a fully successful carry mechanism. Leibniz also
   described the binary numeral system,^[23] a central ingredient of all
   modern computers. However, up to the 1940s, many subsequent designs
   (including Charles Babbage's machines of the 1822 and even ENIAC of
   1945) were based on the decimal system.^[e]

    Detail of an arithmometer built before 1851. The one-digit multiplier
                  cursor (ivory top) is the leftmost cursor

   Around 1820, Charles Xavier Thomas de Colmar created what would over
   the rest of the century become the first successful, mass-produced
   mechanical calculator, the Thomas Arithmometer. It could be used to add
   and subtract, and with a moveable carriage the operator could also
   multiply, and divide by a process of long multiplication and long
   division.^[24] It utilised a stepped drum similar in conception to that
   invented by Leibniz. Mechanical calculators remained in use until the

Punched-card data processing[edit]

   In 1804, French weaver Joseph Marie Jacquard developed a loom in which
   the pattern being woven was controlled by a paper tape constructed from
   punched cards. The paper tape could be changed without changing the
   mechanical design of the loom. This was a landmark achievement in
   programmability. His machine was an improvement over similar weaving
   looms. Punched cards were preceded by punch bands, as in the machine
   proposed by Basile Bouchon. These bands would inspire information
   recording for automatic pianos and more recently numerical control
   machine tools.
   IBM punched-card accounting machines, 1936

   In the late 1880s, the American Herman Hollerith invented data storage
   on punched cards that could then be read by a machine.^[25] To process
   these punched cards, he invented the tabulator and the keypunch
   machine. His machines used electromechanical relays and counters.^[26]
   Hollerith's method was used in the 1890 United States Census. That
   census was processed two years faster than the prior census had
   been.^[27] Hollerith's company eventually became the core of IBM.

   By 1920, electromechanical tabulating machines could add, subtract, and
   print accumulated totals.^[28] Machine functions were directed by
   inserting dozens of wire jumpers into removable control panels. When
   the United States instituted Social Security in 1935, IBM punched-card
   systems were used to process records of 26 million workers.^[29]
   Punched cards became ubiquitous in industry and government for
   accounting and administration.

   Leslie Comrie's articles on punched-card methods and W. J. Eckert's
   publication of Punched Card Methods in Scientific Computation in 1940,
   described punched-card techniques sufficiently advanced to solve some
   differential equations^[30] or perform multiplication and division
   using floating-point representations, all on punched cards and unit
   record machines. Such machines were used during World War II for
   cryptographic statistical processing, as well as a vast number of
   administrative uses. The Astronomical Computing Bureau, Columbia
   University, performed astronomical calculations representing the state
   of the art in computing.^[31]^[32]


   Main article: Calculator
   The Curta calculator could also do multiplication and division.

   By the 20th century, earlier mechanical calculators, cash registers,
   accounting machines, and so on were redesigned to use electric motors,
   with gear position as the representation for the state of a variable.
   The word "computer" was a job title assigned to primarily women who
   used these calculators to perform mathematical calculations.^[33] By
   the 1920s, British scientist Lewis Fry Richardson's interest in weather
   prediction led him to propose human computers and numerical analysis to
   model the weather; to this day, the most powerful computers on Earth
   are needed to adequately model its weather using the Navier-Stokes

   Companies like Friden, Marchant Calculator and Monroe made desktop
   mechanical calculators from the 1930s that could add, subtract,
   multiply and divide.^[35] In 1948, the Curta was introduced by Austrian
   inventor Curt Herzstark. It was a small, hand-cranked mechanical
   calculator and as such, a descendant of Gottfried Leibniz's Stepped
   Reckoner and Thomas' Arithmometer.

   The world's first all-electronic desktop calculator was the British
   Bell Punch ANITA, released in 1961.^[36]^[37] It used vacuum tubes,
   cold-cathode tubes and Dekatrons in its circuits, with 12 cold-cathode
   "Nixie" tubes for its display. The ANITA sold well since it was the
   only electronic desktop calculator available, and was silent and quick.
   The tube technology was superseded in June 1963 by the U.S.
   manufactured Friden EC-130, which had an all-transistor design, a stack
   of four 13-digit numbers displayed on a 5-inch (13 cm) CRT, and
   introduced reverse Polish notation (RPN).

First general-purpose computing device[edit]

   Main article: Analytical Engine
   A portion of Babbage's Difference Engine

   Charles Babbage, an English mechanical engineer and polymath,
   originated the concept of a programmable computer. Considered the
   "father of the computer",^[38] he conceptualized and invented the first
   mechanical computer in the early 19th century. After working on his
   revolutionary difference engine, designed to aid in navigational
   calculations, in 1833 he realized that a much more general design, an
   Analytical Engine, was possible. The input of programs and data was to
   be provided to the machine via punched cards, a method being used at
   the time to direct mechanical looms such as the Jacquard loom. For
   output, the machine would have a printer, a curve plotter and a bell.
   The machine would also be able to punch numbers onto cards to be read
   in later. It employed ordinary base-10 fixed-point arithmetic.

   The Engine incorporated an arithmetic logic unit, control flow in the
   form of conditional branching and loops, and integrated memory, making
   it the first design for a general-purpose computer that could be
   described in modern terms as Turing-complete.^[39]^[40]

   There was to be a store, or memory, capable of holding 1,000 numbers of
   40 decimal digits each (ca. 16.7 kB). An arithmetical unit, called the
   "mill", would be able to perform all four arithmetic operations, plus
   comparisons and optionally square roots. Initially it was conceived as
   a difference engine curved back upon itself, in a generally circular
   layout,^[41] with the long store exiting off to one side. (Later
   drawings depict a regularized grid layout.)^[42] Like the central
   processing unit (CPU) in a modern computer, the mill would rely on its
   own internal procedures, roughly equivalent to microcode in modern
   CPUs, to be stored in the form of pegs inserted into rotating drums
   called "barrels", to carry out some of the more complex instructions
   the user's program might specify.^[43]
   Trial model of a part of the Analytical Engine, built by Babbage, as
   displayed at the Science Museum, London

   The programming language to be employed by users was akin to modern day
   assembly languages. Loops and conditional branching were possible, and
   so the language as conceived would have been Turing-complete as later
   defined by Alan Turing. Three different types of punch cards were used:
   one for arithmetical operations, one for numerical constants, and one
   for load and store operations, transferring numbers from the store to
   the arithmetical unit or back. There were three separate readers for
   the three types of cards.

   The machine was about a century ahead of its time. However, the project
   was slowed by various problems including disputes with the chief
   machinist building parts for it. All the parts for his machine had to
   be made by hand--this was a major problem for a machine with thousands
   of parts. Eventually, the project was dissolved with the decision of
   the British Government to cease funding. Babbage's failure to complete
   the analytical engine can be chiefly attributed to difficulties not
   only of politics and financing, but also to his desire to develop an
   increasingly sophisticated computer and to move ahead faster than
   anyone else could follow. Ada Lovelace translated and added notes to
   the "Sketch of the Analytical Engine" by Luigi Federico Menabrea. This
   appears to be the first published description of programming, so Ada
   Lovelace is widely regarded as the first computer programmer.^[44]
   Torres Quevedo's 1920 electromechanical arithmometer, one of several
   designs based on Babbage. This prototype automatically performed
   arithmetic operations and used a typewriter to send commands and print
   its results.

   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.^[45]^[46] Two other
   inventors, Leonardo Torres y Quevedo and Vannevar Bush, also did follow
   on research based on Babbage's work. In his Essays on Automatics (1913)
   Torres y Quevedo designed a Babbage type of calculating machine that
   used electromechanical parts which included floating-point number
   representations and built an early prototype in 1920. 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.^[47]

Analog computers[edit]

   Main article: Analog computer

   Further information: Mechanical computer

   Sir William Thomson's third tide-predicting machine design, 1879-81

   In the first half of the 20th century, analog computers were considered
   by many to be the future of computing. These devices used the
   continuously changeable aspects of physical phenomena such as
   electrical, mechanical, or hydraulic quantities to model the problem
   being solved, in contrast to digital computers that represented varying
   quantities symbolically, as their numerical values change. As an analog
   computer does not use discrete values, but rather continuous values,
   processes cannot be reliably repeated with exact equivalence, as they
   can with Turing machines.^[48]

   The first modern analog computer was a tide-predicting machine,
   invented by Sir William Thomson, later Lord Kelvin, in 1872. It used a
   system of pulleys and wires to automatically calculate predicted tide
   levels for a set period at a particular location and was of great
   utility to navigation in shallow waters. His device was the foundation
   for further developments in analog computing.^[49]

   The differential analyser, a mechanical analog computer designed to
   solve differential equations by integration using wheel-and-disc
   mechanisms, was conceptualized in 1876 by James Thomson, the brother of
   the more famous Lord Kelvin. He explored the possible construction of
   such calculators, but was stymied by the limited output torque of the
   ball-and-disk integrators.^[50] In a differential analyzer, the output
   of one integrator drove the input of the next integrator, or a graphing

   A Mk. I Drift Sight. The lever just in front of the bomb aimer's
   fingertips sets the altitude, the wheels near his knuckles set the wind
   and airspeed.

   An important advance in analog computing was the development of the
   first fire-control systems for long range ship gunlaying. When gunnery
   ranges increased dramatically in the late 19th century it was no longer
   a simple matter of calculating the proper aim point, given the flight
   times of the shells. Various spotters on board the ship would relay
   distance measures and observations to a central plotting station. There
   the fire direction teams fed in the location, speed and direction of
   the ship and its target, as well as various adjustments for Coriolis
   effect, weather effects on the air, and other adjustments; the computer
   would then output a firing solution, which would be fed to the turrets
   for laying. In 1912, British engineer Arthur Pollen developed the first
   electrically powered mechanical analogue computer (called at the time
   the Argo Clock).^[citation needed] It was used by the Imperial Russian
   Navy in World War I.^[citation needed] The alternative Dreyer Table
   fire control system was fitted to British capital ships by mid-1916.

   Mechanical devices were also used to aid the accuracy of aerial
   bombing. Drift Sight was the first such aid, developed by Harry
   Wimperis in 1916 for the Royal Naval Air Service; it measured the wind
   speed from the air, and used that measurement to calculate the wind's
   effects on the trajectory of the bombs. The system was later improved
   with the Course Setting Bomb Sight, and reached a climax with World War
   II bomb sights, Mark XIV bomb sight (RAF Bomber Command) and the
   Norden^[51] (United States Army Air Forces).

   The art of mechanical analog computing reached its zenith with the
   differential analyzer,^[52] built by H. L. Hazen and Vannevar Bush at
   MIT starting in 1927, which built on the mechanical integrators of
   James Thomson and the torque amplifiers invented by H. W. Nieman. A
   dozen of these devices were built before their obsolescence became
   obvious; the most powerful was constructed at the University of
   Pennsylvania's Moore School of Electrical Engineering, where the ENIAC
   was built.

   A fully electronic analog computer was built by Helmut Hoelzer in 1942
   at Peenemuende Army Research Center.^[53]^[54]^[55]

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

Advent of the digital computer[edit]

   The principle of the modern computer was first described by computer
   scientist Alan Turing, who set out the idea in his seminal 1936
   paper,^[56] On Computable Numbers. Turing reformulated Kurt Goedel's
   1931 results on the limits of proof and computation, replacing Goedel's
   universal arithmetic-based formal language with the formal and simple
   hypothetical devices that became known as Turing machines. 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
   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. Von
   Neumann acknowledged that the central concept of the modern computer
   was due to this paper.^[57] 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[edit]

   Further information: Mechanical computer S: Electro-mechanical

   The era of modern computing began with a flurry of development before
   and during World War II. Most digital computers built in this period
   were electromechanical - electric switches drove mechanical relays to
   perform the calculation. These devices had a low operating speed and
   were eventually superseded by much faster all-electric computers,
   originally using vacuum tubes.

   The Z2 was one of the earliest examples of an electromechanical relay
   computer, and was created by German engineer Konrad Zuse in 1940. It
   was an improvement on his earlier Z1; although it used the same
   mechanical memory, it replaced the arithmetic and control logic with
   electrical relay circuits.^[58]

   Replica of Zuse's Z3, the first fully automatic, digital
   (electromechanical) computer

   In the same year, electro-mechanical devices called bombes were built
   by British cryptologists to help decipher German
   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 (GC&CS) at Bletchley Park by Alan Turing,^[59] with
   an important refinement devised in 1940 by Gordon Welchman.^[60] 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 "cryptologic bomb"
   (Polish: "bomba kryptologiczna").

   In 1941, Zuse followed his earlier machine up with the Z3,^[58] the
   world's first working electromechanical programmable, fully automatic
   digital computer.^[61] The Z3 was built with 2000 relays, implementing
   a 22-bit word length that operated at a clock frequency of about
   5-10 Hz.^[62] Program code and data were stored on punched film. It was
   quite similar to modern machines in some respects, pioneering numerous
   advances such as floating-point numbers. Replacement of the
   hard-to-implement decimal system (used in Charles Babbage's earlier
   design) by the simpler binary system meant that Zuse's machines were
   easier to build and potentially more reliable, given the technologies
   available at that time.^[63] The Z3 was proven to have been a
   Turing-complete machine in 1998 by Raul Rojas.^[64] 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 electromechanical IBM SSEC and in Britain in the
   fully electronic Manchester Baby.^[65]

   Zuse suffered setbacks during World War II when some of his machines
   were destroyed in the course of 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

   In 1944, the Harvard Mark I was constructed at IBM's Endicott
   laboratories.^[66] It was a similar general purpose electro-mechanical
   computer to the Z3, but was not quite Turing-complete.

  Digital computation[edit]

   The term digital was first suggested by 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),^[67] completed a relay-based calculator he later dubbed
   the "Model K" (for "kitchen table", on which he had assembled it),
   which became the first binary adder.^[68] 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 binary logic, but
   many early machines were decimal computers. 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, 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 Schroeder and A. N.
   Whitehead.^[69] In 1879 Gottlob Frege develops the formal approach to
   logic and proposes the first logic language for logical equations.^[70]

   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 gates, which are now
   ubiquitous in digital computers.^[71] They showed^[72] that electronic
   relays and switches can realize the expressions of Boolean algebra.
   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.^[71]^: pp.494-495

  Electronic data processing[edit]

   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, the
   Atanasoff-Berry Computer, the Colossus computers, and the ENIAC were
   built by hand, using circuits containing relays or valves (vacuum
   tubes), and often used punched cards or punched paper tape for input
   and as the main (non-volatile) storage medium.^[73]

   Engineer Tommy Flowers joined the telecommunications branch of the
   General Post Office in 1926. While working at the 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 tubes.^[49]

   In the US, in 1940 Arthur Dickinson (IBM) invented the first digital
   electronic computer.^[74] This calculating device was fully electronic
   - control, calculations and output (the first electronic display).^[75]
   John Vincent Atanasoff and Clifford E. Berry of Iowa State University
   developed the Atanasoff-Berry Computer (ABC) in 1942,^[76] the first
   binary electronic digital calculating device.^[77] 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 distinguish it from modern computers.^[78]

   Computers whose logic was primarily built using vacuum tubes are now
   known as first generation computers.

  The electronic programmable computer[edit]

   Main articles: Colossus computer and ENIAC

   Colossus was the first electronic digital 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, 40 miles
   (64 km) north of London, achieved a number of successes at breaking
   encrypted enemy military communications. The German encryption machine,
   Enigma, was first attacked with the help of the electro-mechanical
   bombes.^[79] Women often operated these bombe machines.^[80]^[81] 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, a
   fixed-function machine to aid in code breaking.^[82] Tommy Flowers, a
   senior engineer at the Post Office Research Station^[83] was
   recommended to Max Newman by Alan Turing^[84] and spent eleven months
   from early February 1943 designing and building the more flexible
   Colossus computer (which superseded the Heath Robinson).^[85]^[86]
   After a functional test in December 1943, Colossus was shipped to
   Bletchley Park, where it was delivered on 18 January 1944^[87] and
   attacked its first message on 5 February.^[88]

   Wartime photo of Colossus No. 10

   Colossus was the world's first electronic digital programmable
   computer.^[49] 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 logical operations on its data,^[89] but it was not
   Turing-complete. Data input to Colossus was by 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 40 ft/s (12.2 m/s; 27.3 mph). 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.^[90] The first Mark 2 Colossus became operational on 1 June
   1944, just in time for the Allied Invasion of Normandy on 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 registers and systolic
   arrays, enabling five simultaneous tests, each involving up to 100
   Boolean calculations. This enabled five different possible start
   positions to be examined for one transit of the paper tape.^[91] As
   well as wheel setting some later 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. Ten Mk 2 Colossi were operational by the end
   of the war.

   ENIAC was the first Turing-complete electronic device, and performed
   ballistics trajectory calculations for the United States Army.^[92]

   Without the use of these machines, the Allies would have been deprived
   of the very valuable intelligence that was obtained from reading the
   vast quantity of enciphered high-level telegraphic messages between the
   German High Command (OKW) and their 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 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.^[f] A reconstructed working copy of one
   of the Colossus machines is now on display at Bletchley Park.

   The US-built ENIAC (Electronic Numerical Integrator and Computer) was
   the first electronic programmable computer built in the US. Although
   the ENIAC was similar to the Colossus it was much faster and more
   flexible. It was unambiguously a Turing-complete device and could
   compute any problem that would fit into its memory. Like the Colossus,
   a "program" on the ENIAC was defined by the states of its patch cables
   and switches, a far cry from the stored program electronic machines
   that came later. Once a program was written, 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

   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.^[94] One of its major engineering feats was
   to minimize the effects of tube burnout, which was a common problem in
   machine reliability at that time. The machine was in almost constant
   use for the next ten years.

Stored-program computer[edit]

   Main article: Stored-program computer

   Further information: List of vacuum-tube computers

   Early computing machines were programmable in the sense that they could
   follow the sequence of steps they had been set up to execute, but the
   "program", or steps that the machine was to execute, were set up
   usually by changing how the wires were plugged into a patch panel or
   plugboard. "Reprogramming", when it was possible at all, was a
   laborious process, starting with engineers working out flowcharts,
   designing the new set up, and then the often-exacting process of
   physically re-wiring patch panels.^[95] Stored-program computers, by
   contrast, were designed to store a set of instructions (a program), in
   memory - typically the same memory as stored data.


   Design of the von Neumann architecture, 1947

   The theoretical basis for the stored-program computer had been proposed
   by Alan Turing in his 1936 paper. In 1945 Turing joined the National
   Physical Laboratory and began his work on developing an electronic
   stored-program digital computer. His 1945 report 'Proposed Electronic
   Calculator' was the first specification for such a device.

   Meanwhile, John von Neumann at the Moore School of Electrical
   Engineering, University of Pennsylvania, circulated his First Draft of
   a Report on the EDVAC in 1945. Although substantially similar to
   Turing's design and containing comparatively little engineering detail,
   the computer architecture it outlined became known as the "von Neumann
   architecture". Turing presented a more detailed paper to the National
   Physical Laboratory (NPL) Executive Committee in 1946, giving the first
   reasonably complete design of a stored-program computer, a device he
   called the Automatic Computing Engine (ACE). However, the better-known
   EDVAC design of John von Neumann, who knew of Turing's theoretical
   work, received more publicity, despite its incomplete nature and
   questionable lack of attribution of the sources of some of the

   Turing thought that the speed and the size of computer memory were
   crucial elements, so he proposed a high-speed memory of what would
   today be called 25 KB, accessed at a speed of 1 MHz. The ACE
   implemented subroutine calls, whereas the EDVAC did not, and the ACE
   also used Abbreviated Computer Instructions, an early form of
   programming language.

  Manchester Baby[edit]

   Main article: Manchester Baby

   Three tall racks containing electronic circuit boards
   A section of the rebuilt Manchester Baby, the first electronic
   stored-program computer

   The Manchester Baby was the world's first electronic stored-program
   computer. It was built at the Victoria University of Manchester by
   Frederic C. Williams, Tom Kilburn and Geoff Tootill, and ran its first
   program on 21 June 1948.^[96]

   The machine was not intended to be a practical computer but was instead
   designed as a testbed for the Williams tube, the first random-access
   digital storage device.^[97] Invented by Freddie Williams and Tom
   Kilburn^[98]^[99] at the University of Manchester in 1946 and 1947, it
   was a cathode-ray tube that used an effect called secondary emission to
   temporarily store electronic binary data, and was used successfully in
   several early computers.

   Although the computer was small and primitive, it was a proof of
   concept for solving a single problem; Baby was the first working
   machine to contain all of the elements essential to a modern electronic
   computer.^[100] As soon as the Baby had demonstrated the feasibility of
   its design, a project was initiated at the university to develop the
   design into a more usable computer, the Manchester Mark 1. The Mark 1
   in turn quickly became the prototype for the Ferranti Mark 1, the
   world's first commercially available general-purpose computer.^[101]

   The Baby had a 32-bit word length and a memory of 32 words. As it was
   designed to be the simplest possible stored-program computer, the only
   arithmetic operations implemented in hardware were subtraction and
   negation; other arithmetic operations were implemented in software. The
   first of three programs written for the machine found the highest
   proper divisor of 2^18 (262,144), a calculation that was known would
   take a long time to run--and so prove the computer's reliability--by
   testing every integer from 2^18 - 1 downwards, as division was
   implemented by repeated subtraction of the divisor. The program
   consisted of 17 instructions and ran for 52 minutes before reaching the
   correct answer of 131,072, after the Baby had performed 3.5 million
   operations (for an effective CPU speed of 1.1 kIPS). The successive
   approximations to the answer were displayed as the successive positions
   of a bright dot on the Williams tube.

  Manchester Mark 1[edit]

   The Experimental machine led on to the development of the Manchester
   Mark 1 at the University of Manchester.^[102] Work began in August
   1948, and the first version was operational by April 1949; a program
   written to search for Mersenne primes ran error-free for nine hours on
   the night of 16/17 June 1949. The machine's successful operation was
   widely reported in the British press, which used the phrase "electronic
   brain" in describing it to their readers.

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



   The other contender for being the first recognizably modern digital
   stored-program computer^[103] was the EDSAC,^[104] designed and
   constructed by Maurice Wilkes and his team at the University of
   Cambridge Mathematical Laboratory in England at the University of
   Cambridge in 1949. The machine was inspired by John von Neumann's
   seminal First Draft of a Report on the EDVAC and was one of the first
   usefully operational electronic digital stored-program computer.^[g]

   EDSAC ran its first programs on 6 May 1949, when it calculated a table
   of squares^[107] and a list of prime numbers.The EDSAC also served as
   the basis for the first commercially applied computer, the LEO I, used
   by food manufacturing company J. Lyons & Co. Ltd. EDSAC 1 was finally
   shut down on 11 July 1958, having been superseded by EDSAC 2 which
   stayed in use until 1965.^[108]

     The "brain" [computer] may one day come down to our level [of the
     common people] and help with our income-tax and book-keeping
     calculations. But this is speculation and there is no sign of it so

   -- British newspaper The Star in a June 1949 news article about the
   EDSAC computer, long before the era of the personal computers.^[109]



   ENIAC inventors John Mauchly and J. Presper Eckert proposed the EDVAC's
   construction in August 1944, and design work for the EDVAC commenced at
   the University of Pennsylvania's Moore School of Electrical
   Engineering, before the ENIAC was fully operational. The design
   implemented a number of important architectural and logical
   improvements conceived during the ENIAC's construction, and a
   high-speed serial-access memory.^[110] However, Eckert and Mauchly left
   the project and its construction floundered.

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

  Commercial computers[edit]

   The first commercial computer was the Ferranti Mark 1, built by
   Ferranti and delivered to the University of Manchester in February
   1951. It was based on the Manchester Mark 1. The main improvements over
   the Manchester Mark 1 were in the size of the primary storage (using
   random access Williams tubes), secondary storage (using a magnetic
   drum), a faster multiplier, and additional instructions. The basic
   cycle time was 1.2 milliseconds, and a multiplication could be
   completed in about 2.16 milliseconds. The multiplier used almost a
   quarter of the machine's 4,050 vacuum tubes (valves).^[111] A second
   machine was purchased by the University of Toronto, before the design
   was revised into the Mark 1 Star. At least seven of these later
   machines were delivered between 1953 and 1957, one of them to Shell
   labs in Amsterdam.^[112]

   In October 1947, the directors of J. Lyons & Company, a British
   catering company famous for its teashops but with strong interests in
   new office management techniques, decided to take an active role in
   promoting the commercial development of computers. The LEO I computer
   (Lyons Electronic Office) became operational in April 1951^[113] and
   ran the world's first regular routine office computer job. On 17
   November 1951, the J. Lyons company began weekly operation of a bakery
   valuations job on the LEO - the first business application to go live
   on a stored program computer.^[h]

   In June 1951, the UNIVAC I (Universal Automatic Computer) was delivered
   to the U.S. Census Bureau. Remington Rand eventually sold 46 machines
   at more than US$1 million each ($10.4 million as of 2022).^[114] UNIVAC
   was the first "mass produced" computer. It used 5,200 vacuum tubes and
   consumed 125 kW of power. Its primary storage was serial-access mercury
   delay lines capable of storing 1,000 words of 11 decimal digits plus
   sign (72-bit words).

   Front panel of the IBM 650

   IBM introduced a smaller, more affordable computer in 1954 that proved
   very popular.^[i]^[116] The IBM 650 weighed over 900 kg, the attached
   power supply weighed around 1350 kg and both were held in separate
   cabinets of roughly 1.5 * 0.9 * 1.8 m. The system cost US$500,000^[117]
   ($5.05 million as of 2022) or could be leased for US$3,500 a month
   ($40,000 as of 2022).^[114] Its drum memory was originally 2,000
   ten-digit words, later expanded to 4,000 words. Memory limitations such
   as this were to dominate programming for decades afterward. The program
   instructions were fetched from the spinning drum as the code ran.
   Efficient execution using drum memory was provided by a combination of
   hardware architecture - the instruction format included the address of
   the next instruction - and software: the Symbolic Optimal Assembly
   Program, SOAP,^[118] assigned instructions to the optimal addresses (to
   the extent possible by static analysis of the source program). Thus
   many instructions were, when needed, located in the next row of the
   drum to be read and additional wait time for drum rotation was reduced.


   In 1951, British scientist Maurice Wilkes developed the concept of
   microprogramming from the realisation that the central processing unit
   of a computer could be controlled by a miniature, highly specialized
   computer program in high-speed ROM. Microprogramming allows the base
   instruction set to be defined or extended by built-in programs (now
   called firmware or microcode).^[119] This concept greatly simplified
   CPU development. He first described this at the University of
   Manchester Computer Inaugural Conference in 1951, then published in
   expanded form in IEEE Spectrum in 1955.^[citation needed]

   It was widely used in the CPUs and floating-point units of mainframe
   and other computers; it was implemented for the first time in EDSAC
   2,^[120] which also used multiple identical "bit slices" to simplify
   design. Interchangeable, replaceable tube assemblies were used for each
   bit of the processor.^[j]

Magnetic memory[edit]

   Diagram of a 4 *4 plane of magnetic core memory in an X/Y line
   coincident-current setup. X and Y are drive lines, S is sense, Z is
   inhibit. Arrows indicate the direction of current for writing.

   Magnetic drum memories were developed for the US Navy during WW II with
   the work continuing at Engineering Research Associates (ERA) in 1946
   and 1947. ERA, then a part of Univac included a drum memory in its
   1103, announced in February 1953. The first mass-produced computer, the
   IBM 650, also announced in 1953 had about 8.5 kilobytes of drum memory.

   Magnetic core memory patented in 1949^[122] with its first usage
   demonstrated for the Whirlwind computer in August 1953.^[123]
   Commercialization followed quickly. Magnetic core was used in
   peripherals of the IBM 702 delivered in July 1955, and later in the 702
   itself. The IBM 704 (1955) and the Ferranti Mercury (1957) used
   magnetic-core memory. It went on to dominate the field into the 1970s,
   when it was replaced with semiconductor memory. Magnetic core peaked in
   volume about 1975 and declined in usage and market share

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

Early digital computer characteristics[edit]

   Further information: Analytical Engine S: Comparison to other early

   CAPTION: Defining characteristics of some early digital computers of
   the 1940s (In the history of computing hardware)

   Name First operational Numeral system Computing mechanism Programming
   Arthur H. Dickinson IBM (US) Jan 1940 Decimal Electronic Not
   programmable No
   Joseph Desch NCR (US) March 1940 Decimal Electronic Not programmable No
   Zuse Z3 (Germany) May 1941 Binary floating point Electro-mechanical
   Program-controlled by punched 35 mm film stock (but no conditional
   branch) In theory (1998)
   Atanasoff-Berry Computer (US) 1942 Binary Electronic Not programmable
   -- single purpose No
   Colossus Mark 1 (UK) February 1944 Binary Electronic Program-controlled
   by patch cables and switches No
   Harvard Mark I - IBM ASCC (US) May 1944 Decimal Electro-mechanical
   Program-controlled by 24-channel punched paper tape (but no conditional
   branch) Debatable
   Colossus Mark 2 (UK) June 1944 Binary Electronic Program-controlled by
   patch cables and switches In theory (2011)^[125]
   Zuse Z4 (Germany) March 1945 Binary floating point Electro-mechanical
   Program-controlled by punched 35 mm film stock In 1950
   ENIAC (US) February 1946 Decimal Electronic Program-controlled by patch
   cables and switches Yes
   ARC2 (SEC) (UK) May 1948 Binary Electronic Stored-program in rotating
   drum memory Yes
   Manchester Baby (UK) June 1948 Binary Electronic Stored-program in
   Williams cathode-ray tube memory Yes
   Modified ENIAC (US) September 1948 Decimal Electronic Read-only stored
   programming mechanism using the Function Tables as program ROM Yes
   Manchester Mark 1 (UK) April 1949 Binary Electronic Stored-program in
   Williams cathode-ray tube memory and magnetic drum memory Yes
   EDSAC (UK) May 1949 Binary Electronic Stored-program in mercury
   delay-line memory Yes
   CSIRAC (Australia) November 1949 Binary Electronic Stored-program in
   mercury delay-line memory Yes

Transistor computers[edit]

   Main article: Transistor computer

   Further information: List of transistorized computers

   A bipolar junction transistor

   The bipolar transistor was invented in 1947. From 1955 onward
   transistors replaced vacuum tubes in computer designs,^[126] giving
   rise to the "second generation" of computers. Compared to vacuum tubes,
   transistors have many advantages: they are smaller, and require less
   power than vacuum tubes, so give off less heat. Silicon junction
   transistors were much more reliable than vacuum tubes and had longer
   service life. Transistorized computers could contain tens of thousands
   of binary logic circuits in a relatively compact space. Transistors
   greatly reduced computers' size, initial cost, and operating cost.
   Typically, second-generation computers were composed of large numbers
   of printed circuit boards such as the IBM Standard Modular
   System,^[127] each carrying one to four logic gates or flip-flops.

   At the University of Manchester, a team under the leadership of Tom
   Kilburn designed and built a machine using the newly developed
   transistors instead of valves. Initially the only devices available
   were germanium point-contact transistors, less reliable than the valves
   they replaced but which consumed far less power.^[128] Their first
   transistorized computer, and the first in the world, was operational by
   1953,^[129] and a second version was completed there in April
   1955.^[130] The 1955 version used 200 transistors, 1,300 solid-state
   diodes, and had a power consumption of 150 watts. However, the machine
   did make use of valves to generate its 125 kHz clock waveforms and in
   the circuitry to read and write on its magnetic drum memory, so it was
   not the first completely transistorized computer.

   That distinction goes to the Harwell CADET of 1955,^[131] built by the
   electronics division of the Atomic Energy Research Establishment at
   Harwell. The design featured a 64-kilobyte magnetic drum memory store
   with multiple moving heads that had been designed at the National
   Physical Laboratory, UK. By 1953 this team had transistor circuits
   operating to read and write on a smaller magnetic drum from the Royal
   Radar Establishment. The machine used a low clock speed of only 58 kHz
   to avoid having to use any valves to generate the clock

   CADET used 324-point-contact transistors provided by the UK company
   Standard Telephones and Cables; 76 junction transistors were used for
   the first stage amplifiers for data read from the drum, since
   point-contact transistors were too noisy. From August 1956 CADET was
   offering a regular computing service, during which it often executed
   continuous computing runs of 80 hours or more.^[133]^[134] Problems
   with the reliability of early batches of point contact and alloyed
   junction transistors meant that the machine's mean time between
   failures was about 90 minutes, but this improved once the more reliable
   bipolar junction transistors became available.^[135]

   The Manchester University Transistor Computer's design was adopted by
   the local engineering firm of Metropolitan-Vickers in their Metrovick
   950, the first commercial transistor computer anywhere.^[136] Six
   Metrovick 950s were built, the first completed in 1956. They were
   successfully deployed within various departments of the company and
   were in use for about five years.^[130] A second generation computer,
   the IBM 1401, captured about one third of the world market. IBM
   installed more than ten thousand 1401s between 1960 and 1964.

  Transistor peripherals[edit]

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

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

   During the second generation remote terminal units (often in the form
   of Teleprinters like a Friden Flexowriter) saw greatly increased
   use.^[k] Telephone connections provided sufficient speed for early
   remote terminals and allowed hundreds of kilometers separation between
   remote-terminals and the computing center. Eventually these stand-alone
   computer networks would be generalized into an interconnected network
   of networks--the Internet.^[l]

  Transistor supercomputers[edit]

   The University of Manchester Atlas in January 1963

   The early 1960s saw the advent of supercomputing. The Atlas was a joint
   development between the University of Manchester, Ferranti, and
   Plessey, and was first installed at Manchester University and
   officially commissioned in 1962 as one of the world's first
   supercomputers - considered to be the most powerful computer in the
   world at that time.^[139] It was said that whenever Atlas went offline
   half of the United Kingdom's computer capacity was lost.^[140] It was a
   second-generation machine, using discrete germanium transistors. Atlas
   also pioneered the Atlas Supervisor, "considered by many to be the
   first recognisable modern operating system".^[141]

   In the US, a series of computers at Control Data Corporation (CDC) were
   designed by Seymour Cray to use innovative designs and parallelism to
   achieve superior computational peak performance.^[142] The CDC 6600,
   released in 1964, is generally considered the first
   supercomputer.^[143]^[144] The CDC 6600 outperformed its predecessor,
   the IBM 7030 Stretch, by about a factor of 3. With performance of about
   1 megaFLOPS, the CDC 6600 was the world's fastest computer from 1964 to
   1969, when it relinquished that status to its successor, the CDC 7600.

Integrated circuit computers[edit]

   Main article: History of computing hardware (1960s-present) S: Third

   The "third-generation" of digital electronic computers used integrated
   circuit (IC) chips as the basis of their logic.

   The idea of an integrated circuit was conceived by a radar scientist
   working for the Royal Radar Establishment of the Ministry of Defence,
   Geoffrey W.A. Dummer.

   The first working integrated circuits were invented by Jack Kilby at
   Texas Instruments and Robert Noyce at Fairchild Semiconductor.^[145]
   Kilby recorded his initial ideas concerning the integrated circuit in
   July 1958, successfully demonstrating the first working integrated
   example on 12 September 1958.^[146] Kilby's invention was a hybrid
   integrated circuit (hybrid IC).^[147] It had external wire connections,
   which made it difficult to mass-produce.^[148]

   Noyce came up with his own idea of an integrated circuit half a year
   after Kilby.^[149] Noyce's invention was a monolithic integrated
   circuit (IC) chip.^[150]^[148] His chip solved many practical problems
   that Kilby's had not. Produced at Fairchild Semiconductor, it was made
   of silicon, whereas Kilby's chip was made of germanium. The basis for
   Noyce's monolithic IC was Fairchild's planar process, which allowed
   integrated circuits to be laid out using the same principles as those
   of printed circuits. The planar process was developed by Noyce's
   colleague Jean Hoerni in early 1959, based on Mohamed M. Atalla's work
   on semiconductor surface passivation by silicon dioxide at Bell Labs in
   the late 1950s.^[151]^[152]^[153]

   Third generation (integrated circuit) computers first appeared in the
   early 1960s in computers developed for government purposes, and then in
   commercial computers beginning in the mid-1960s. The first silicon IC
   computer was the Apollo Guidance Computer or AGC.^[154] Although not
   the most powerful computer of its time, the extreme constraints on
   size, mass, and power of the Apollo spacecraft required the AGC to be
   much smaller and denser than any prior computer, weighing in at only 70
   pounds (32 kg). Each lunar landing mission carried two AGCs, one each
   in the command and lunar ascent modules.

Semiconductor memory[edit]

   Main article: Semiconductor memory

   The MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS
   transistor) was invented by Mohamed M. Atalla and Dawon Kahng at Bell
   Labs in 1959.^[155] In addition to data processing, the MOSFET enabled
   the practical use of MOS transistors as memory cell storage elements, a
   function previously served by magnetic cores. Semiconductor memory,
   also known as MOS memory, was cheaper and consumed less power than
   magnetic-core memory.^[156] MOS random-access memory (RAM), in the form
   of static RAM (SRAM), was developed by John Schmidt at Fairchild
   Semiconductor in 1964.^[156]^[157] In 1966, Robert Dennard at the IBM
   Thomas J. Watson Research Center developed MOS dynamic RAM
   (DRAM).^[158] In 1967, Dawon Kahng and Simon Sze at Bell Labs developed
   the floating-gate MOSFET, the basis for MOS non-volatile memory such as
   EPROM, EEPROM and flash memory.^[159]^[160]

Microprocessor computers[edit]

   Main article: History of computing hardware (1960s-present) S: Fourth

   The "fourth-generation" of digital electronic computers used
   microprocessors as the basis of their logic. The microprocessor has
   origins in the MOS integrated circuit (MOS IC) chip.^[161] Due to rapid
   MOSFET scaling, MOS IC chips rapidly increased in complexity at a rate
   predicted by Moore's law, leading to large-scale integration (LSI) with
   hundreds of transistors on a single MOS chip by the late 1960s. The
   application of MOS LSI chips to computing was the basis for the first
   microprocessors, as engineers began recognizing that a complete
   computer processor could be contained on a single MOS LSI chip.^[161]

   The subject of exactly which device was the first microprocessor is
   contentious, partly due to lack of agreement on the exact definition of
   the term "microprocessor". The earliest multi-chip microprocessors were
   the Four-Phase Systems AL-1 in 1969 and Garrett AiResearch MP944 in
   1970, developed with multiple MOS LSI chips.^[161] The first
   single-chip microprocessor was the Intel 4004,^[162] developed on a
   single PMOS LSI chip.^[161] It was designed and realized by Ted Hoff,
   Federico Faggin, Masatoshi Shima and Stanley Mazor at Intel, and
   released in 1971.^[m] Tadashi Sasaki and Masatoshi Shima at Busicom, a
   calculator manufacturer, had the initial insight that the CPU could be
   a single MOS LSI chip, supplied by Intel.^[164]^[162]

   The die from an Intel 8742, an 8-bit microcontroller that includes a
   CPU running at 12 MHz, RAM, EPROM, and I/O

   While the earliest microprocessor ICs literally contained only the
   processor, i.e. the central processing unit, of a computer, their
   progressive development naturally led to chips containing most or all
   of the internal electronic parts of a computer. The integrated circuit
   in the image on the right, for example, an Intel 8742, is an 8-bit
   microcontroller that includes a CPU running at 12 MHz, 128 bytes of
   RAM, 2048 bytes of EPROM, and I/O in the same chip.

   During the 1960s there was considerable overlap between second and
   third generation technologies.^[n] IBM implemented its IBM Solid Logic
   Technology modules in hybrid circuits for the IBM System/360 in 1964.
   As late as 1975, Sperry Univac continued the manufacture of
   second-generation machines such as the UNIVAC 494. The Burroughs large
   systems such as the B5000 were stack machines, which allowed for
   simpler programming. These pushdown automatons were also implemented in
   minicomputers and microprocessors later, which influenced programming
   language design. Minicomputers served as low-cost computer centers for
   industry, business and universities.^[165] It became possible to
   simulate analog circuits with the simulation program with integrated
   circuit emphasis, or SPICE (1971) on minicomputers, one of the programs
   for electronic design automation (EDA). The microprocessor led to the
   development of microcomputers, small, low-cost computers that could be
   owned by individuals and small businesses. Microcomputers, the first of
   which appeared in the 1970s, became ubiquitous in the 1980s and beyond.

   Altair 8800

   While which specific system is considered the first microcomputer is a
   matter of debate, as there were several unique hobbyist systems
   developed based on the Intel 4004 and its successor, the Intel 8008,
   the first commercially available microcomputer kit was the Intel
   8080-based Altair 8800, which was announced in the January 1975 cover
   article of Popular Electronics. However, this was an extremely limited
   system in its initial stages, having only 256 bytes of DRAM in its
   initial package and no input-output except its toggle switches and LED
   register display. Despite this, it was initially surprisingly popular,
   with several hundred sales in the first year, and demand rapidly
   outstripped supply. Several early third-party vendors such as Cromemco
   and Processor Technology soon began supplying additional S-100 bus
   hardware for the Altair 8800.

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

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

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

   Systems as complicated as computers require very high reliability.
   ENIAC remained on, in continuous operation from 1947 to 1955, for eight
   years before being shut down. Although a vacuum tube might fail, it
   would be replaced without bringing down the system. By the simple
   strategy of never shutting down ENIAC, the failures were dramatically
   reduced. The vacuum-tube SAGE air-defense computers became remarkably
   reliable - installed in pairs, one off-line, tubes likely to fail did
   so when the computer was intentionally run at reduced power to find
   them. Hot-pluggable hard disks, like the hot-pluggable vacuum tubes of
   yesteryear, continue the tradition of repair during continuous
   operation. Semiconductor memories routinely have no errors when they
   operate, although operating systems like Unix have employed memory
   tests on start-up to detect failing hardware. Today, the requirement of
   reliable performance is made even more stringent when server farms are
   the delivery platform.^[166] Google has managed this by using
   fault-tolerant software to recover from hardware failures, and is even
   working on the concept of replacing entire server farms on-the-fly,
   during a service event.^[167]^[168]

   In the 21st century, multi-core CPUs became commercially
   available.^[169] Content-addressable memory (CAM)^[170] has become
   inexpensive enough to be used in networking, and is frequently used for
   on-chip cache memory in modern microprocessors, although no computer
   system has yet implemented hardware CAMs for use in programming
   languages. Currently, CAMs (or associative arrays) in software are
   programming-language-specific. Semiconductor memory cell arrays are
   very regular structures, and manufacturers prove their processes on
   them; this allows price reductions on memory products. During the
   1980s, CMOS logic gates developed into devices that could be made as
   fast as other circuit types; computer power consumption could therefore
   be decreased dramatically. Unlike the continuous current draw of a gate
   based on other logic types, a CMOS gate only draws significant current
   during the 'transition' between logic states, except for leakage.

   CMOS circuits have allowed computing to become a commodity which is now
   ubiquitous, embedded in many forms, from greeting cards and telephones
   to satellites. The thermal design power which is dissipated during
   operation has become as essential as computing speed of operation. In
   2006 servers consumed 1.5% of the total energy budget of the U.S.^[171]
   The energy consumption of computer data centers was expected to double
   to 3% of world consumption by 2011. The SoC (system on a chip) has
   compressed even more of the integrated circuitry into a single chip;
   SoCs are enabling phones and PCs to converge into single hand-held
   wireless mobile devices.^[172]

   Quantum computing is an emerging technology in the field of computing.
   MIT Technology Review reported 10 November 2017 that IBM has created a
   50-qubit computer; currently its quantum state lasts 50
   microseconds.^[173] Google researchers have been able to extend the 50
   microsecond time limit, as reported 14 July 2021 in Nature;^[174]
   stability has been extended 100-fold by spreading a single logical
   qubit over chains of data qubits for quantum error correction.^[174]
   Physical Review X reported a technique for 'single-gate sensing as a
   viable readout method for spin qubits' (a singlet-triplet spin state in
   silicon) on 26 November 2018.^[175] A Google team has succeeded in
   operating their RF pulse modulator chip at 3 Kelvin, simplifying the
   cryogenics of their 72-qubit computer, which is setup to operate at 0.3
   Kelvin; but the readout circuitry and another driver remain to be
   brought into the cryogenics.^[176]^[o] See: Quantum
   supremacy^[178]^[179] Silicon qubit systems have demonstrated
   entanglement at non-local distances.^[180]

   Computing hardware and its software have even become a metaphor for the
   operation of the universe.^[181]


   An indication of the rapidity of development of this field can be
   inferred from the history of the seminal 1947 article by Burks,
   Goldstine and von Neumann.^[182] By the time that anyone had time to
   write anything down, it was obsolete. After 1945, others read John von
   Neumann's First Draft of a Report on the EDVAC, and immediately started
   implementing their own systems. To this day, the rapid pace of
   development has continued, worldwide.^[183]^[p]

See also[edit]

     * Antikythera mechanism
     * History of computing
     * History of computing hardware (1960s-present)
     * History of laptops
     * History of personal computers
     * History of software
     * Information Age
     * IT History Society
     * Timeline of computing
     * List of pioneers in computer science
     * Vacuum-tube computer


    1. ^ The Ishango bone is a bone tool, dated to the Upper Paleolithic
       era, about 18,000 to 20,000 BC. It is a dark brown length of bone,
       the fibula of a baboon. It has a series of tally marks carved in
       three columns running the length of the tool. It was found in 1960
       in Belgian Congo.^[1]
    2. ^ According to Schmandt-Besserat 1981, these clay containers
       contained tokens, the total of which were the count of objects
       being transferred. The containers thus served as something of a
       bill of lading or an accounts book. In order to avoid breaking open
       the containers, first, clay impressions of the tokens were placed
       on the outside of the containers, for the count; the shapes of the
       impressions were abstracted into stylized marks; finally, the
       abstract marks were systematically used as numerals; these numerals
       were finally formalized as numbers. Eventually (Schmandt-Besserat
       estimates it took 5000 years.^[5]) the marks on the outside of the
       containers were all that were needed to convey the count, and the
       clay containers evolved into clay tablets with marks for the count.
    3. ^ Robson has recommended at least one supplement to
       Schmandt-Besserat (1981), e.g., a review, Englund, R. (1993). "The
       origins of script". Science. 260 (5114): 1670-1671.
       doi:10.1126/science.260.5114.1670. PMID 17810210.^[7]
    4. ^ A Spanish implementation of Napier's bones (1617), is documented
       in Montaner & Simon 1887, pp. 19-20.
    5. ^ Binary-coded decimal (BCD) is a numeric representation, or
       character encoding, which is still widely used.
    6. ^ The existence of Colossus was not known to American computer
       scientists, such as Gordon Bell and Allen Newell. And was not in
       Bell & Newell (1971) Computing Structures, a standard reference
       work in the 1970s.
    7. ^ The Manchester Baby predated EDSAC as a stored-program computer,
       but was built as a test bed for the Williams tube and not as a
       machine for practical use.^[105] However, the Manchester Mark 1 of
       1949 (not to be confused with the 1948 prototype, the Baby) was
       available for university research in April 1949 despite being still
       under development.^[106]
    8. ^ Martin 2008, p. 24 notes that David Caminer (1915-2008) served as
       the first corporate electronic systems analyst, for this first
       business computer system. LEO would calculate an employee's pay,
       handle billing, and other office automation tasks.
    9. ^ For example, Kara Platoni's article on Donald Knuth stated that
       "there was something special about the IBM 650".^[115]
   10. ^ The microcode was implemented as extracode on Atlas.^[121]
   11. ^ Allen Newell used remote terminals to communicate cross-country
       with the RAND computers.^[137]
   12. ^ Bob Taylor conceived of a generalized protocol to link together
       multiple networks to be viewed as a single session regardless of
       the specific network: "Wait a minute. Why not just have one
       terminal, and it connects to anything you want it to be connected
       to? And, hence, the Arpanet was born."^[138]
   13. ^ The Intel 4004 (1971) die was 12 mm^2, composed of 2300
       transistors; by comparison, the Pentium Pro was 306 mm^2, composed
       of 5.5 million transistors.^[163]
   14. ^ In the defense field, considerable work was done in the
       computerized implementation of equations such as Kalman 1960,
       pp. 35-45
   15. ^ IBM's 127-qubit computer cannot be simulated on traditional
   16. ^ The fastest supercomputer of the top 500 is now Frontier (of Oak
       Ridge National Laboratory) at 1.102 ExaFlops,^[184] which is 2.66
       times faster than Fugaku, now number two of the top 500.^[185]

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Further reading[edit]


   "online access". IEEE Annals of the History of Computing. Archived from
   the original on 2006-05-23.

     Ceruzzi, Paul E. (1998), A History of Modern Computing, The MIT Press

     Computers and Automation Magazine - Pictorial Report on the Computer
     * A PICTORIAL MANUAL ON COMPUTERS, Part 2 - 01/1958
     * 1958-1967 Pictorial Report on the Computer Field - December issues
       (195812.pdf, ..., 196712.pdf)

     Bit by Bit: An Illustrated History of Computers, Stan Augarten, 1984.
   OCR with permission of the author

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