This article presents a detailed timeline of events in the history of computing hardware: from prehistory until 1949. For narratives explaining the overall developments, see History of computing.
Date  Event 

c. 19,000 BC  The Ishango bone, may indicate thateven so earlymaterial objects were used for simple arithmetical operations, and it may provide evidence of some knowledge of prime numbers (although this is disputed).^{[1]} 
c.  The abacus, the first known calculator, was probably invented by the Babylonians as an aid to simple arithmetic around this time period. It laid the foundations for positional notation and later computing developments. 
c. 1770 BC  First known use of zero by ancient Egyptians in accounting texts. 
c. 910 BC  The southpointing chariot was invented in ancient China. It was the first known geared mechanism to use a differential gear. The chariot was a twowheeled vehicle, upon which is a pointing figure connected to the wheels by means of differential gearing. Through careful selection of wheel size, track and gear ratios, the figure atop the chariot always pointed in the same direction. 
c. 500 BC  Indian grammarian Pini formulated the grammar of Sanskrit (in 3959 rules) known as the Ashtadhyayi which was highly systematised and technical. Pini used metarules, transformations, and recursions with such sophistication that his grammar had the computing power equivalent to a Turing machine.^{[]} Pini's work was the forerunner to modern formal language theory, and a precursor to its use in modern computing. The PaniniBackus form used to describe most modern programming languages is also significantly similar to Pini's grammar rules.^{[]} 
c. 200 BC  Indian mathematician/scholar/musician Pingala first described the binary number system which is now used in the design of essentially all modern computing equipment. He also conceived the notion of a binary code similar to the Morse code.^{[2]}^{[3]} 
c. 125 BC  The Antikythera mechanism: A clockwork, analog computer believed to have been designed and built in the Corinthian colony of Syracuse. The mechanism contained a differential gear and was capable of tracking the relative positions of all thenknown heavenly bodies. 
c. 9 AD  Chinese mathematicians first used negative numbers. 
c. 60  Hero of Alexandria made numerous inventions, including "sequence control" in which the operator of a machine set a machine running, which then follows a series of instructions in a deterministic fashion. This was, essentially, the first program. He also made numerous innovations in the field of automata, which are important steps in the development of robotics. 
190  First mention of the suanpan (Chinese abacus) which was widely used until the invention of the modern calculator, and continues to be used in some cultures today. 
Date  Event 

c. 639  Indian mathematician Brahmagupta was the first to describe the modern placevalue numeral system (Hindu numeral system). 
725  Chinese inventor Liang Lingzan built the world's first fully mechanical clock; water clocks, some of them extremely accurate, had been known for centuries previous to this. This was an important technological leap forward; the earliest true computers, made a thousand years later, used technology based on that of clocks.^{[]} 
c. 820  Persian mathematician, Mu?ammad ibn M?s? alKhw?rizm?, described the rudiments of modern algebra whose name is derived from his book AlKit?b almu?ta?ar f? ?is?b al?abr walmuq?bala. The word algorithm is derived from alKhwarizmi's Latinized name Algoritmi. 
c. 850  Arab mathematician, AlKindi (Alkindus), was a pioneer of cryptography. He gave the first known recorded explanation of cryptanalysis in A Manuscript on Deciphering Cryptographic Messages. In particular, he is credited with developing the frequency analysis method whereby variations in the frequency of the occurrence of letters could be analyzed and exploited to break encryption ciphers (i.e. crypanalysis by frequency analysis).^{[4]} The text also covers methods of cryptanalysis, encipherments, cryptanalysis of certain encipherments, and statistical analysis of letters and letter combinations in Arabic.^{[]} 
850  The Ban? M?s? brothers, in their Book of Ingenious Devices, invented "the earliest known mechanical musical instrument", in this case a hydropowered organ which played interchangeable cylinders automatically. This "cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century."^{[5]} They also invented an automatic flute player which appears to have been the first programmable machine.^{[6]} 
c. 1000  Ab? Rayh?n alB?r?n? invented the Planisphere, an analog computer.^{[7]} He also invented the first mechanical lunisolar calendar which employed a gear train and eight gearwheels.^{[8]} This was an early example of a fixedwired knowledge processing machine.^{[9]}^{[dubious – discuss]} 
c. 1015  Arab astronomer, Ab? Ish?q Ibr?h?m alZarq?l? (Arzachel) of alAndalus, invented the Equatorium^{[]}, a mechanical analog computer device used for finding the longitudes and positions of the Moon, Sun and planets without calculation, using a geometrical model to represent the celestial body's mean and anomalistic position.^{[10]} 
c. 1150  Arab astronomer, Jabir ibn Aflah (Geber), invented the Torquetum, an observational instrument and mechanical analog computer device used to transform between spherical coordinate systems.^{[11]} It was designed to take and convert measurements made in three sets of coordinates: horizon, equatorial, and ecliptic. 
1206  Arab engineer, AlJazari, invented numerous automata and made numerous other technological innovations. One of these is a design for a programmable humanoidshaped mannequin: this seems to have been the first serious, scientific (as opposed to magical) plan for a robot.^{[12]} He also invented the "castle clock", an astronomical clock which is considered to be the earliest programmable analog computer.^{[13]} It displayed the zodiac, the solar and lunar orbits, a crescent moonshaped pointer travelling across a gateway causing automatic doors to open every hour,^{[14]}^{[15]} and five robotic musicians who play music when struck by levers operated by a camshaft attached to a water wheel. The length of day and night could be reprogrammed every day in order to account for the changing lengths of day and night throughout the year.^{[13]} 
1235  Persian astronomer Abi Bakr of Isfahan invented a brass astrolabe with a geared calendar movement based on the design of Ab? Rayh?n alB?r?n?'s mechanical calendar analog computer.^{[16]} Abi Bakr's geared astrolabe uses a set of gearwheels and is the oldest surviving complete mechanical geared machine in existence.^{[17]}^{[18]} 
1300  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 
1412  Ahmad alQalqashandi gives a list of ciphers in his Subh ala'sha which include both substitution and transposition, and for the first time, a cipher with multiple substitutions for each plaintext letter. He also gives an exposition on and worked example of cryptanalysis, including the use of tables of letter frequencies and sets of letters which can not occur together in one word. 
c. 1416  Jamsh?d alK?sh? invented the Plate of Conjunctions, an analog computer instrument used to determine the time of day at which planetary conjunctions will occur,^{[19]} and for performing linear interpolation. He also invented a mechanical "planetary computer" which he called the Plate of Zones, which could graphically solve a number of planetary problems, including the prediction of the true positions in longitude of the Sun and Moon,^{[20]} and the planets;^{[21]} the latitudes of the Sun, Moon, and planets; and the ecliptic of the Sun. The instrument also incorporated an alhidade and ruler.^{[22]} 
c. 1450  Kerala school of astronomy and mathematics in South India invented the floatingpoint number system.^{[23]} 
1493  Leonardo da Vinci produced drawings of a device consisting of interlocking cog wheels which can be interpreted as a mechanical calculator capable of addition and subtraction. A working model inspired by this plan was built in 1968 but it remains controversial whether Leonardo really had a calculator in mind.^{[24]} Da Vinci also made plans for a mechanical man: an early design for a robot. 
1614  Scotsman John Napier reinvented a form of logarithms and an ingenious system of movable rods (1617, referred to as Napier's Rods or Napier's bones). These rods were based on the lattice or gelosia multiplication algorithm and allowed the operator to multiply, divide, and calculate square and cube roots by moving the rods around and placing them in specially constructed boards. 
1622  William Oughtred developed slide rules based on logarithms as developed by John Napier. 
1623  German polymath Wilhelm Schickard drew a device that he called a calculating clock on two letters that he sent to Johannes Kepler; one in 1623 and the other in 1624. A fire later destroyed the machine as it was being built in 1624 and he decided to abandon his project.^{[25]} This machine became known to the world only in 1957 when the two letters were discovered. Some replicas were built in 1961.^{[26]} This machine had no impact on the development of mechanical calculators.^{[27]} 
Date  Place  Event 

1642  French polymath Blaise Pascal invented the mechanical calculator.^{[28]} Called machine arithmétique, Pascal's calculator and eventually Pascaline, its public introduction in 1645 started the development of mechanical calculators first in Europe and then in the rest of the world. It was the first machine to have a controlled carry mechanism.^{[29]} Pascal built 50 prototypes before releasing his first machine (eventually twenty machines were built). The Pascaline inspired the works of Gottfried Leibniz (1671), Thomas de Colmar (1820) and Dorr E. Felt (1887).  
1666  Sir Samuel Morland (16251695), of England, produced a nondecimal adding machine,^{[30]} suitable for use with English money. Instead of a carry mechanism, it registered carries on auxiliary dials, from which the user reentered them as addends.  
1672  German mathematician, Gottfried Leibniz started designing a machine which multiplied, the 'Stepped Reckoner'. It could multiply numbers of up to 5 and 12 digits to give a 16 digit result. Two machines were built, one in 1694 (it was discovered in an attic in 1879), and one in 1706.^{[31]}  
1685  In an article titled "Machina arithmetica in qua non additio tantum et subtractio sed et multiplicatio nullo, diviso vero paene nullo animi labore peragantur", Gottfried Leibniz described a machine that used wheels with movable teeth which, when coupled to a Pascaline, could perform all four mathematical operations.^{[32]} There is no evidence that Leibniz ever constructed this pinwheel machine.  
1709  Giovanni Poleni was the first to build a calculator that used a pinwheel design. It was made of wood and was built in the shape of a calculating clock.^{[33]}  
1726  Jonathan Swift described (satirically) a machine ("engine") in his Gulliver's Travels. The "engine" consisted of a wooden frame with wooden blocks containing parts of speech. When the engine's 40 levers are simultaneously turned, the machine displayed grammatical sentence fragments.  
1774  Philipp Matthäus Hahn, in what is now Germany, made a successful portable calculator able to perform all four mathematical operations.  
1775  Charles Stanhope, 3rd Earl Stanhope, of England, designed and constructed a successful multiplying calculator similar to Leibniz's.  
1786  J. H. Müller, an engineer in the Hessian army, first conceived of the idea of a difference engine (first written reference to the basic principles of a difference machine is dated to 1784).^{[34]}  
1804  JosephMarie Jacquard developed the Jacquard loom, an automatic loom controlled by punched cards.  
1820  Charles Xavier Thomas de Colmar invented the 'Arithmometer' which after thirty more years of development became, in 1851, the first massproduced mechanical calculator. An operator could perform long multiplications and divisions quickly and effectively by using a movable accumulator for the result. This machine was based on the earlier works of Pascal and Leibniz.  
1822  Charles Babbage designed his first mechanical computer, the first prototype of the decimal difference engine for tabulating polynomials.  
1832  Semen Korsakov proposed the usage of punched cards^{[]} for information storage and search. He designed several machines to demonstrate his ideas, including the socalled linear homeoscope.  
1832  Babbage and Joseph Clement produced a prototype segment of his difference engine,^{[35]} which operated on 6digit numbers and secondorder differences (i.e., it could tabulate quadratic polynomials). The complete engine, which would have been roomsized, was planned to operate both on sixthorder differences with numbers of about 20 digits, and on thirdorder differences with numbers of 30 digits. Each addition would have been done in two phases, the second one taking care of any carries generated in the first. The output digits were to be punched into a soft metal plate, from which a printing plate might have been made. But there were various difficulties, and no more than this prototype piece was ever finished.  
c. 1833  Babbage conceived, and began to design, his decimal 'Analytical Engine'.^{[36]} A program for it was to be stored on readonly memory, in the form of punched cards. Babbage continued to work on the design for years, though after about 1840 design changes seem to have been minor. The machine would have operated on 40digit numbers; the 'mill' (CPU) would have had 2 main accumulators and some auxiliary ones for specific purposes, while the 'store' (memory) would have held a thousand 50digit numbers. There would have been several punched card readers, for both programs and data; the cards were to be chained and the motion of each chain reversible. The machine would have performed conditional jumps. There would also have been a form of microcoding: the meaning of instructions were to depend on the positioning of metal studs in a slotted barrel, called the "control barrel". The machine envisioned would have been capable of an addition in 3 seconds and a multiplication or division in 24 minutes. It was to be powered by a steam engine. In the end, no more than a few parts were actually built.  
1835  Joseph Henry invented the electromechanical relay.  
1840  Charles Babbage's first public exposition about his Analytical Engine at Accademia delle Scienze, Turin^{[37]}.  
1842  Timoleon Maurel patented the Arithmaurel, a mechanical calculator with a very intuitive user interface, especially for multiplying and dividing numbers because the result was displayed as soon as the operands were entered. It received a gold medal at the French national show in Paris in 1849.^{[38]} Unfortunately its complexity and the fragility of its design prevented it from being manufactured.^{[39]}  
1842  Construction of Babbage's difference engine was cancelled as an official project.^{[40]} The cost overruns had been considerable (£17,470 was spent, which, in 2004 money, would be about £1,000,000 ^{[41]}).  
1843  Per Georg Scheutz and his son Edvard produced a 5digit numbers and thirdorder model of the difference engine with printer; the Swedish government agrees to fund their next development in 1851.  
1846  Babbage began to work on an improved difference engine (the Difference Engine No.2), producing a completely executed set of plans by 1849.^{[42]} The machine would have operated on 7thorder differences and 31digit numbers, but nobody was found to pay to have it built. In 19891991 a team at London's Science Museum did build one from the surviving plans. They built components using modern methods, but with tolerances no better than Clement could have provided... and, after a bit of tinkering and detaildebugging, they found that the machine works properly. In 2000, the printer was also completed.  
1847  British Mathematician George Boole developed binary algebra (Boolean algebra)^{[43]} which has been widely used in binary computer design and operation, beginning about a century later. See 1939. 
Date  Place  Event 

1851  After 30 years of development, Thomas de Colmar launched the mechanical calculator industry by starting the manufacturing of a much simplified Arithmometer (invented in 1820). Aside from its clones, which started thirty years later,^{[44]} it was the only calculating machine available anywhere in the world for forty years (Dorr E. Felt only sold one hundred comptometers and a few comptographs from 1887 to 1890^{[45]}). Its simplicity made it the most reliable calculator to date. It was a big machine (a 20 digit arithmometer was long enough to occupy most of a desktop). Even though the arithmometer was only manufactured until 1915, twenty European companies manufactured improved clones of its design until the beginning of WWII ; they were Burkhardt, Layton, Saxonia, Gräber, Peerless, MercedesEuklid, XxX, Archimedes, etc...  
1853  To Babbage's delight, the Scheutzes completed the first fullscale difference engine, which they called a Tabulating Machine. It operated on 15digit numbers and 4thorder differences, and produced printed output just as Babbage's would have. A second machine was later built in 1859 to the same design by the firm of Bryan Donkin of London.  
1856  The first Tabulating Machine (see 1853) was bought by the Dudley Observatory in Albany, New York, and the second was ordered in 1857 by the British government. The Albany machine was used to produce a set of astronomical tables; but the Observatory's director was fired for this extravagant purchase, and the machine never seriously used again, eventually ending up in a museum. The second machine had a long and useful life.  
c. 1859  Martin Wiberg produced a reworked differenceenginelike machine intended to prepare interest rates (first publication in 1860) and logarithmic tables (first publication in 1875).  
1866  The first practical logic machine (logical abacus) was built by William Stanley Jevons.  
1871  Babbage produced a prototype section of the Analytical Engine's mill and printer.^{[46]}  
1878  Ramón Verea, living in New York City, invented a calculator with an internal multiplication table; this was much faster than the shifting carriage, or other digital methods of the time. He wasn't interested in putting it into production, however; it seems he just wanted to show that a Spaniard could invent as well as an American.  
1878  A committee investigated the feasibility of completing the Analytical Engine, and concluded that it would be impossible now that Babbage was dead. The project was then largely forgotten, except by a very few; Howard Aiken was a notable exception.  
1884  Dorr Felt, of Chicago, developed his Comptometer. This was the first calculator in which operands are entered by pressing keys rather than having to be, for example, dialled in. It was feasible because of Felt's invention of a carry mechanism fast enough to act while the keys return from being pressed. Felt and Tarrant started a partnership to manufacture the comptometer in 1887.  
1886  First use of Herman Hollerith tabulating system in the Baltimore Department of Health.  
1887  Herman Hollerith files a patent application for an integrating tabulator (granted in 1890), which could add numbers encoded on punched cards. First recorded use of this device was in 1889 in the Office of the Surgeon General of the Army. In 1896 Hollerith introduced improved model.^{[47]}  
1889  Dorr Felt invented the first printing desk calculator.  
1890  A multiplying calculator more compact than the Arithmometer entered mass production.^{[48]}^{[49]}^{[50]} The design was the independent, and more or less simultaneous, invention of Frank S. Baldwin, of the United States, and Willgodt Theophil Odhner, a Swede living in Russia. Fluted drums were replaced by a "variabletoothed gear" design: a disk with radial pegs that could be made to protrude or retract from it.  
1890  The 1880 US census had taken 7 years to complete since all processing had been done by hand from journal sheets. The increasing population suggested that by the 1890 census, data processing would take longer than the 10 years before the next censusso a competition was held to find a better method. It was won by a Census Department employee, Herman Hollerith, who went on to found the Tabulating Machine Company, later to become IBM. He invented the recording of data on a medium that could then be read by a machine. Prior uses of machine readable media had been for control (Automatons, Piano rolls, looms, ...), not data. "After some initial trials with paper tape, he settled on punched cards..."^{[51]} His machines used mechanical relays to increment mechanical counters. This method was used in the 1890 census. The net effect of the many changes from the 1880 census: the larger population, the data items to be collected, the Census Bureau headcount, the scheduled publications, and the use of Hollerith's electromechanical tabulators, was to reduce the time required to process the census from eight years for the 1880 census to six years for the 1890 census.^{[52]} The inspiration for this invention was Hollerith's observation of railroad conductors during a trip in the Western United States; they encoded a crude description of the passenger (tall, bald, male) in the way they punched the ticket.  
1891  William S. Burroughs of St. Louis invented a machine similar to Felt's (see 1884) in 1885 but unlike the comptometer it was a 'keyset' machine which only processed each number after a crank handle was pulled. The true manufacturing of this machine started in 1891 even though Burroughs had started his American Arithmometer Company in 1886 (it later became Burroughs Corporation and is now called Unisys).  
1899  Ry?ichi Yazu began^{[]} the development of a mechanical calculating machine (automatic abacus).^{[53]} Ryoichi independently conducted research on calculating machines, and it took three years to complete his biquinary mechanical desktop calculating machine, before applying for a patent in 1902.^{[54]} It was Japan's first successful mechanical computer.^{[55]}  
c. 1900  The Standard Adding Machine Company released the first 10key adding machine in about 1900. The inventor, William Hopkins, filed his first patent on October 4, 1892. The 10 keys were set on a single row.  
1902  First model of Dalton adding machine is built.^{[56]} Remington advertised the Dalton adding machine as the first 10key printing adding machine.^{[57]} The 10 keys were set on two rows. Six machines had been manufactured by the end of 1906.  
1905  Ichitaro Kawaguchi, an engineer at the Ministry of Communications and Transportation, built the Kawaguchi Electric Tabulation Machine, Japan's first electromechanical computer,^{[55]} used to tabulate some of the results of the 1904 Demographics Statistical Study.^{[58]}  
1906  Henry Babbage, Charles's son, with the help of the firm of R. W. Munro, completed the 'mill' from his father's Analytical Engine, to show that it would have worked. It does. The complete machine was not produced.  
1906  Audion (Vacuum tube or thermionic valve) invented by Lee De Forest.  
1906  Herman Hollerith introduces a tabulator with a plugboard that can be rewired to adapt the machine for different applications. Plugboards were widely used to direct machine calculations until displaced by stored programs in the 1950s.^{[59]}  
1919  William Henry Eccles and F. W. Jordan published the first flipflop circuit design.  
1924  Walther Bothe built an AND logic gate  the coincidence circuit, for use in physics experiments, for which he received the Nobel Prize in Physics 1954. Digital circuitries of all kinds make heavy use of this technique.  
1928  IBM standardizes on punched cards with 80 columns of data and rectangular holes. Widely known as IBM Cards, they dominate the data processing industry for almost half a century.  
1929  Westinghouse AC Calculating board. A Network analyzer (AC power) used for electrical transmission line simulations up until the 1960s.  
c. 1930  Vannevar Bush built a partly electronic differential analyser capable of solving differential equations.  
c. 1930  Welsh physicist C. E. WynnWilliams, at Cambridge, England, used a ring of thyratron tubes to construct a binary digital counter that counted emitted Alpha particles.^{[60]} 
Date  Place  Event 

1931  Kurt Gödel of Vienna University, Austria, published a paper on a universal formal language based on arithmetic operations. He used it to encode arbitrary formal statements and proofs, and showed that formal systems such as traditional mathematics are either inconsistent in a certain sense, or contain unprovable but true statements. This result is often called the fundamental result of theoretical computer science.  
1931  IBM introduced the IBM 601 Multiplying Punch, an electromechanical machine that could read two numbers, up to 8 digits long, from a card and punch their product onto the same card.^{[61]}  
1934  From 1934 to 1936, NEC engineer Akira Nakishima published a series of papers introducing switching circuit theory.^{[62]}^{[63]}^{[64]}^{[65]} This laid the foundations for digital circuit design, in digital computers and other areas of modern technology.^{[65]}  
1934  Wallace Eckert of Columbia University connects an IBM 285 Tabulator, an 016 Duplicating Punch and an IBM 601 Multiplying Punch with a camcontrolled sequencer switch that he designed. The combined system was used to automate the integration of differential equations.^{[66]}  
1936  Alan Turing of Cambridge University, England, published a paper on 'computable numbers'^{[67]} which reformulated Kurt Gödel's results (see related work by Alonzo Church). His paper addressed the famous 'Entscheidungsproblem' whose solution was sought in the paper by reasoning (as a mathematical device) about a simple and theoretical computer, known today as a Turing machine. In many ways, this device was more convenient than Gödel's arithmeticsbased universal formal system.  
1937  George Stibitz of the Bell Telephone Laboratories (Bell Labs), New York City, constructed a demonstration 1bit binary adder using relays. This was one of the first binary computers, although at this stage it was only a demonstration machine; improvements continued leading to the Complex Number Calculator of January 1940.  
1937  Claude E. Shannon published a paper on the implementation of symbolic logic using relays as his MIT Master's thesis. He cited and elaborated on Akira Nakashima's earlier work in switching circuit theory.^{[64]}  
1938  Konrad Zuse of Berlin, completed the 'Z1', the first mechanical binary programmable computer. It was based on Boolean Algebra and had some of the basic ingredients of modern machines, using the binary system and floatingpoint arithmetic. Zuse's 1936 patent application (Z23139/GMD Nr. 005/021) also suggested a 'von Neumann' architecture (reinvented about 1945) with program and data modifiable in storage. Originally the machine was called the 'V1' but retroactively renamed after the war, to avoid confusion with the V1 flying bomb. It worked with floating point numbers (7bit exponent, 16bit mantissa, and sign bit). The memory used sliding metal parts to store 16 such numbers, and worked well; but the arithmetic unit was less successful, occasionally suffering from certain mechanical engineering problems. The program was read from holes punched in discarded 35 mm movie film. Data values could have been entered from a numeric keyboard, and outputs were displayed on electric lamps. The machine was not a general purpose computer (i.e., Turing complete) because it lacked loop capabilities.  
1939  William Hewlett and David Packard established the HewlettPackard Company in Packard's garage in Palo Alto, California with an initial investment of $538 (equivalent to $9,353 in 2017); this was considered to be the symbolic founding of Silicon Valley. HP would grow to become one of the largest technology companies in the world today.  
1939 Nov 
John Vincent Atanasoff and graduate student Clifford Berry of Iowa State College (now the Iowa State University), Ames, Iowa, completed a prototype 16bit adder. This was the first machine to calculate using vacuum tubes.  
1939  1940  Helmut Schreyer completed a prototype 10bit adder^{[]} using vacuum tubes, and a prototype memory using neon lamps.^{[]}  
1940  At Bell Labs, Samuel Williams and George Stibitz completed a calculator which could operate on complex numbers, and named it the 'Complex Number Calculator'; it was later known as the 'Model I Relay Calculator'. It used telephone switching parts for logic: 450 relays and 10 crossbar switches. Numbers were represented in 'plus 3 BCD'; that is, for each decimal digit, 0 is represented by binary 0011, 1 by 0100, and so on up to 1100 for 9; this scheme requires fewer relays than straight BCD. Rather than requiring users to come to the machine to use it, the calculator was provided with three remote keyboards, at various places in the building, in the form of teletypes. Only one could be used at a time, and the output was automatically displayed on the same one. On 9 September 1940, a teletype was set up at a Dartmouth College in Hanover, New Hampshire, with a connection to New York, and those attending the conference could use the machine remotely.  
1940  Konrad Zuse completed the 'Z2' (originally 'V2'), which combined the Z1's existing mechanical memory unit with a new arithmetic unit using relay logic. Like the Z1, the Z2 lacked loop capabilities. The project was interrupted for a year when Zuse was drafted in 1939, but continued after he was released.
In 1940 Zuse presented the Z2 to an audience of the Deutsche Versuchsanstalt für Luftfahrt ("German Laboratory for Aviation") in BerlinAdlershof. 
Date  Place  Event  

1941 May 11 
Now working with limited backing from the DVL (German Aeronautical Research Institute), Konrad Zuse completed the 'Z3' (originally 'V3'): the first operational programmable computer. One major improvement over Charles Babbage's nonfunctional device is the use of Leibniz's binary system (Babbage and others unsuccessfully tried to build decimal programmable computers). Zuse's machine also featured floating point numbers with a 7bit exponent, 14bit mantissa (with a '1' bit automatically prefixed unless the number is 0), and a sign bit. The memory held 64 of these words and therefore required over 1400 relays; there were 1200 more in the arithmetic and control units. It also featured parallel adders. The program, input, and output were implemented as described above for the Z1. Although conditional jumps were not available, it has been shown that Zuse's Z3 is, in principle, capable of functioning as a universal computer.^{[68]}^{[69]} The machine could do 34 additions per second, and took 35 seconds for a multiplication. The Z3 was destroyed in 1943 during an Allied bombardment of Berlin, and had no impact on computer technology in America and England.  
1942 Summer 
Atanasoff and Berry completed a specialpurpose calculator for solving systems of simultaneous linear equations, later called the 'ABC' ('AtanasoffBerry Computer'). This had 60 50bit words of memory in the form of capacitors (with refresh circuitsthe first regenerative memory) mounted on two revolving drums. The clock speed was 60 Hz, and an addition took 1 second. For secondary memory it used punched cards, moved around by the user. The holes were not actually punched in the cards, but burned. The punched card system's error rate was never reduced beyond 0.001%, and this was inadequate. Atanasoff left Iowa State after the U.S. entered the war, ending his work on digital computing machines.  
1942  Helmut Hölzer built an analog computer to calculate and simulate^{[70]}V2 rocket trajectories.^{[71]}^{[72]}^{[73]}  
1942  Konrad Zuse developed the S1, the world's first process computer, used by Henschel to measure the surface of wings.  
1943 Apr 
Max Newman, WynnWilliams and their team at the secret Government Code and Cypher School ('Station X'), Bletchley Park, Bletchley, England, completed the 'Heath Robinson'. This was a specialized counting machine used for cipherbreaking, not a generalpurpose calculator or computer, but a logic device using a combination of electronics and relay logic. It read data optically at 2000 characters per second from two closed loops of paper tape, each typically about 1000 characters long. It was significant since it was the forerunner of Colossus. Newman knew Turing from Cambridge (Turing was a student of Newman's), and had been the first person to see a draft of Turing's 1936 paper.^{[67]}Heath Robinson is the name of a British cartoonist known for drawings of comical machines, like the American Rube Goldberg. Two later machines in the series will be named after London stores with 'Robinson' in their names.  
1943 Sep 
Williams and Stibitz completed the 'Relay Interpolator', later called the 'Model II Relay Calculator'. This was a programmable calculator; again, the program and data were read from paper tapes. An innovative feature was that, for greater reliability (errordetecting/selfchecking), numbers were represented in a biquinary format using seven relays for each digit, of which exactly two should be "on": 01 00001 for 0, 01 00010 for 1, and so on up to 10 10000 for 9. Some of the later machines in this series would use the biquinary notation for the digits of floatingpoint numbers.  
1943 Dec 
The Colossus was built, by Dr Thomas Flowers at The Post Office Research Laboratories in London, to crack the German Lorenz (SZ42) cipher. It contained 2400 vacuum tubes for logic and applied a programmable logical function to a stream of input characters, read from punched tape at a rate of 5000 characters a second. Colossus was used at Bletchley Park during World War IIas a successor to the unreliable Heath Robinson machines. Although 10 were eventually built, most were destroyed immediately after they had finished their work to maintain the secrecy of the work.  
1944 August 7 
The IBM Automatic Sequence Controlled Calculator was turned over to Harvard University, which called it the Harvard Mark I. It was designed by Howard Aiken and his team, financed and built by IBMit became the second programcontrolled machine (after Konrad Zuse's). The whole machine was 51 feet (16 m) long, weighed 5 (short) tons (4.5 tonnes), and incorporated 750,000 parts. It used 3304 electromechanical relays as onoff switches, had 72 accumulators (each with its own arithmetic unit), as well as a mechanical register with a capacity of 23 digits plus sign. The arithmetic was fixedpoint and decimal, with a control panel setting determining the number of decimal places. Inputoutput facilities include card readers, a card punch, paper tape readers, and typewriters. There were 60 sets of rotary switches, each of which could be used as a constant registersort of mechanical readonly memory. The program was read from one paper tape; data could be read from the other tapes, or the card readers, or from the constant registers. Conditional jumps were not available. However, in later years, the machine was modified to support multiple paper tape readers for the program, with the transfer from one to another being conditional, rather like a conditional subroutine call. Another addition allowed the provision of plugboard wired subroutines callable from the tape. Used to create ballistics tables for the US Navy.  
1945  Konrad Zuse developed Plankalkül, the first higherlevel programming language. He also presented the Z4 in March.  
1945  Vannevar Bush developed the theory of the memex, a hypertext device linked to a library of books and films.  
1945 
John von Neumann drafted a report describing the future computer eventually built as the EDVAC (Electronic Discrete Variable Automatic Computer). First Draft of a Report on the EDVAC includes the first published description of the design of a storedprogram computer, giving rise to the term von Neumann architecture. It directly or indirectly influenced nearly all subsequent projects, especially EDSAC. The design team included John W. Mauchly and J. Presper Eckert.  
1946 February 14 
ENIAC (Electronic Numerical Integrator and Computer): One of the first totally electronic, valve driven, digital, programcontrolled computers was unveiled although it was shut down on 9 November 1946 for a refurbishment and a memory upgrade, and was transferred to Aberdeen Proving Ground, Maryland in 1947. Development had started in 1943 at the Ballistic Research Laboratory, USA, by John W. Mauchly and J. Presper Eckert. It weighed 30 tonnes and contained 18,000 electronic valves, consuming around 160 kW of electrical power. It could do 5,000 basic calculations a second. It was used for calculating ballistic trajectories and testing theories behind the hydrogen bomb.  
1946 February 19 
ACE (Automatic Computing Engine): Alan Turing presented a detailed paper to the National Physical Laboratory (NPL) Executive Committee, giving the first reasonably complete design of a storedprogram computer. However, because of the strict and longlasting secrecy around his wartime work at Bletchley Park, he was prohibited (having signed the Official Secrets Act) from explaining that he knew that his ideas could be implemented in an electronic device.  
1946  The trackball was invented as part of a radar plotting system named Comprehensive Display System (CDS) by Ralph Benjamin when working for the British Royal Navy Scientific Service.^{[74]}^{[75]} Benjamin's project used analog computers to calculate the future position of target aircraft based on several initial input points provided by a user with a joystick. Benjamin felt that a more elegant input device was needed and invented a ball tracker^{[74]}^{[75]} system called the roller ball^{[74]} for this purpose in 1946.^{[74]}^{[75]} The device was patented in 1947,^{[74]} but only a prototype was ever built^{[75]} and the device was kept as a secret outside military.^{[75]}  
1947 September 
Development of the first assembly language by Kathleen Booth at Birkbeck, University of London following work with John von Neumann and Herman Goldstine at the Institute for Advanced Study.^{[76]}^{[77]}  
1947 December 16 
Invention of the transistor at Bell Laboratories, USA, by William B. Shockley, John Bardeen and Walter Brattain.  
1947  Howard Aiken completed the Harvard Mark II.  
1947  The Association for Computing Machinery (ACM), was founded as the world's first scientific and educational computing society. It remains to this day with a membership currently around 78,000. Its headquarters are in New York City.  
1948 January 27 
IBM finished the SSEC (Selective Sequence Electronic Calculator). It was the first computer to modify a stored program. "About 1300 vacuum tubes were used to construct the arithmetic unit and eight very highspeed registers, while 23000 relays were used in the control structure and 150 registers of slower memory."  
1948 May 12 
The Birkbeck ARC, the first of three machines developed at Birkbeck, University of London by Andrew Booth and Kathleen Booth, officially came online on this date. The control was entirely electromechanical and the memory was based on a rotating magnetic drum.^{[77]} This was the first rotating drum storage device in existence.^{[78]}  
1948 June 21 
the Manchester Baby was built at the University of Manchester. It ran its first program on this date. It was the first computer to store both its programs and data in RAM, as modern computers do. By 1949 the 'Baby' had grown, and acquired a magnetic drum for more permanent storage, and it became the Manchester Mark 1.  
1948  ANACOM from Westinghouse was an ACenergized electrical analog computer system used up until the early 1990s for problems in mechanical and structural design, fluidics, and various transient problems.  
1948  IBM introduced the '604', the first machine to feature Field Replaceable Units (FRUs), which cut downtime as entire pluggable units can simply be replaced instead of troubleshot.  
1948  The first Curta handheld mechanical calculator was sold. The Curta computed with 11 digits of decimal precision on input operands up to 8 decimal digits. The Curta was about the size of a handheld pepper grinder.  
1949 Mar 
John Presper Eckert and John William Mauchly construct the BINAC for Northrop.  
1949 May 6 
This is considered the birthday of modern computing.^{[]}Maurice Wilkes and a team at Cambridge University executed the first stored program on the EDSAC computer, which used paper tape inputoutput. Based on ideas from John von Neumann about stored program computers, the EDSAC was the first complete, fully functional von Neumann architecture computer.  
1949 Oct 
The Manchester Mark 1 final specification is completed; this machine was notably in being the first computer to use the equivalent of base/index registers, a feature not entering common computer architecture until the second generation around 1955.  
1949  CSIR Mk I (later known as CSIRAC), Australia's first computer, ran its first test program. It was a vacuumtubebased electronic generalpurpose computer. Its main memory stored data as a series of acoustic pulses in 5 ft (1.5 m) long tubes filled with mercury.  
1949  MONIAC (Monetary National Income Analogue Computer) also known as the Phillips Hydraulic Computer, was created in 1949 to model the national economic processes of the United Kingdom. The MONIAC consisted of a series of transparent plastic tanks and pipes. It is thought that twelve to fourteen machines were built.  
1949 
