Computing timelines: 500 BC1949, 19501979, 19801989, 1990present
500 B.C.  The abacus was first used by the Babylonians as an aid to simple arithmetic at sometime around this date. The abacus in the form we are most familiar with was first used in China in around 1300 A.D.. 
1500  Leonardo da Vinci produced drawings of a device consisting of interlocking cog wheels which could 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 (see [here (http://dotpoint.com/xnumber/pic_leonardo_calc.htm)].) 
1614  Scotsman John Napier (15501617) published a paper outlining his discovery of the logarithm. Napier also invented an ingenious system of moveable rods (referred to as Napier's Rods or Napier's bones). These were based on logarithms 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. 
1623  Wilhelm Schickard[?] (15921635), of Tübingen, Württemberg (now in Germany), made a "Calculating Clock". This mechanical machine was capable of adding and subtracting up to 6 digit numbers, and warned of an overflow by ringing a bell. Operations were carried out by wheels, and a complete revolution of the units wheel incremented the tens wheel in much the same way counters on old cassette decks worked. The machine and plans were lost and forgotten in the war that was going on, then rediscovered in 1935, only to be lost in war again, and then finally rediscovered in 1956 by the same man (Franz Hammer)! The machine was reconstructed in 1960, and found to be workable. Schickard was a friend of the astronomer Johannes Kepler since they met in the winter of 1617. 
1625  William Oughtred[?] (15751660) invented the slide rule. 
1642  French mathematician, Blaise Pascal built a mechanical adding machine (the "Pascaline"). Despite being more limited than Schickard's 'Calculating Clock' (see 1623), Pascal's machine became far more well known. He was able to sell around a dozen of his machines in various forms, coping with up to 8 digits. 
1668  Sir Samuel Morland[?] (16251695), of England, produces a non decimal adding machine, suitable for use with English money. Instead of a carry mechanism, it registers carries on auxiliary dials, from which the user must reenter them as addends. 
1671  German mathematician, Gottfried Leibniz designed a machine to carry out multiplication, the 'Stepped Reckoner'. It could multiply numbers of up to 5 and 12 digits to give a 16 digit result. The machine was later lost in an attic until 1879. Leibniz was also the inventor of the binary number system and coinventor of calculus. 
1775  Charles, the third Earl Stanhope, of England, makes a successful multiplying calculator similar to Leibniz's. 
1776  Mathieus Hahn[?], somewhere in what will be Germany, also makes a successful multiplying calculator that he started in 1770. 
1786  J. H. Müller, of the Hessian army, conceives the idea of what came to be called a "difference engine". That's a specialpurpose calculator for tabulating values of a polynomial, given the differences between certain values so that the polynomial is uniquely specified; it's useful for any function that can be approximated by a polynomial over suitable intervals. Müller's attempt to raise funds fails and the project is forgotten. 
1801  JosephMarie Jacquard (17521834) developed an automatic loom controlled by punched cards. 
1820  Charles Xavier Thomas de Colmar (17851870), of France, makes his "Arithmometer[?]", the first massproduced calculator. It does multiplication using the same general approach as Leibniz's calculator; with assistance from the user it can also do division. It is also the most reliable calculator yet. Machines of this general design, large enough to occupy most of a desktop, continue to be sold for about 90 years. 
1822  Charles Babbage (17921871) designed his first mechanical computer, the first prototype of the difference engine, a reinvention of Müller's 1786 machine for tabulating polynomials. It was never built, although an attempt was made in 1832. 
1832  Babbage and Joseph Clement produce a prototype segment of his difference engine, which operates on 6digit numbers and 2ndorder differences (i.e. can tabulate quadratic polynomials). The complete engine, which would be roomsized, is planned to be able to operate both on 6thorder differences with numbers of about 20 digits, and on 3rdorder differences with numbers of 30 digits. Each addition would be done in two phases, the second one taking care of any carries generated in the first. The output digits would be punched into a soft metal plate, from which a plate for a printing press could be made. But there are various difficulties, and no more than this prototype piece is ever assembled. 
1834  George Scheutz[?], of Stockholm, produces a small difference engine in wood, after reading a brief description of Babbage's project. 
1834  Babbage conceives, and begins to design, his "Analytical Engine". The program was stored on readonly memory, specifically in the form of punch cards. Babbage continues to work on the design for years, though after about 1840 the changes are minor. The machine would operate on 40digit numbers; the "mill" (CPU) would have 2 main accumulators and some auxiliary ones for specific purposes, while the "store" (memory) would hold perhaps 100 more numbers. There would be several punch card readers, for both programs and data; the cards would be chained and the motion of each chain could be reversed. The machine would be able to perform conditional jumps. There would also be a form of microcoding: the meaning of instructions would depend on the positioning of metal studs in a slotted barrel, called the "control barrel". The machine would do an addition in 3 seconds and a multiplication or division in 24 minutes. It was to be powered by a steam engine. 
1842  Babbage's difference engine project is officially cancelled. (The cost overruns have been considerable, and Babbage is spending too much time on redesigning the Analytical Engine.) 
1843  Scheutz and his son Edvard Scheutz produce a 3rdorder difference engine with printer, and the Swedish government agrees to fund their next development. 
1847  Babbage designs an improved, simpler difference engine (the Difference Engine No.2), a project which took 2 years. The machine could operate on 7thorder differences and 31digit numbers, but nobody is interested in paying to have it built. (In 198991, however, a team at London's Science Museum did just that. They used components of modern construction, but with tolerances no better than Clement could have provided... and, after a bit of tinkering and detaildebugging, they found that the machine does indeed work. In 2000, the printer has also been completed.) 
1848  British Mathematician George Boole devised binary algebra (Boolean algebra) paving the way for the development of a binary computer almost a century later. See 1939. 
1853  To Babbage's delight, the Scheutzes complete the first fullscale difference engine, which they call a Tabulating Machine. It operates on 15digit numbers and 4thorder differences, and produces printed output as Babbage's would have. A second machine is later built to the same design by the firm of Brian Donkin of London. 
1858  The first Tabulating Machine (see 1853) is bought by the Dudley Observatory in Albany, New York, and the second one by the British government. The Albany machine is used to produce a set of astronomical tables; but the observatory's director is then fired for this extravagant purchase, and the machine is never seriously used again, eventually ending up in a museum. The second machine, however, has a long and useful life. 
1871  Babbage produces a prototype section of the Analytical Engine's mill and printer. 
1878  Ramon Verea[?], living in New York City, invents a calculator with an internal multiplication table; this is much faster than the shifting carriage or other digital methods. He isn't interested in putting it into production; he just wants to show that a Spaniard can invent as well as an American. 
1879  A committee investigates the feasibility of completing the Analytical Engine and concludes that it is impossible now that Babbage is dead. The project is then largely forgotten, though Howard Aiken is a notable exception. 
1885  A multiplying calculator more compact than the Arithmometer enters mass production. The design is the independent, and more or less simultaneous, invention of Frank S. Baldwin, of the United States, and T. Odhner, a Swede living in Russia. The fluted drums are replaced by a "variabletoothed gear" design: a disk with radial pegs that can be made to protrude or retract from it. 
1886  Dorr E. Felt (18621930), of Chicago, makes his "Comptometer". This is the first calculator where the operands are entered merely by pressing keys rather than having to be, for example, dialled in. It is feasible because of Felt's invention of a carry mechanism fast enough to act while the keys return from being pressed. 
1889  Felt invents the first printing desk calculator. 
1890  1890 U.S. census. The 1880 census had taken 7 years to complete since all processing had been done by hand off of journal sheets. The increasing population suggested that by the 1890 census the data processing would take longer than the 10 years before the next census  so a competition was held to try to find a better method. This was won by a Census Department employee, Herman Hollerith (18601929  who went on to found the Tabulating Machine Company (see 1911), later to become IBM. Herman borrowed Babbage's idea of using the punched cards (see 1801) from the textile industry for the data storage. His machines used mechanical relays (solenoids) to increment mechanical counters. This method was used in the 1890 census, the result (62,622,250 people) was released in just 6 weeks! This storage allowed much more indepth analysis of the data and so, despite being more efficient, the 1890 census cost about double (actually 198%) that of the 1880 census. The inspiration for this invention was Hollerith's observation of railroad conductors during a trip in the western US; they encoded a crude description of the passenger (tall, bald, male) in the way they punched the ticket. 
1892  William S. Burroughs (18571898), of St. Louis, invents a machine similar to Felt's (see 1886) but more robust, and this is the one that really starts the mechanical office calculator industry. 
1896  IBM founded (as the Tabulating Machine Company), see 1924. Founded by Herman Hollerith , see also 1890). 
1899  "Everything that can be invented has already been invented.", Charles H. Duell, director of the U.S. Patent Office 
1906  Henry Babbage, Charles's son, with the help of the firm of R. W. Munro, completes the mill of his father's Analytical Engine, just to show that it would have worked. It does. The complete machine is never produced. 
1906  Electronic Tube (or Electronic Valve) developed by Lee De Forest in America. Before this it would have been impossible to make digital electronic computers. 
1911  Merger of companies, including Herman Hollerith's Tabulating Machine Company, to Computing  Tabulating  Recording Company  which became IBM in 1924. 
1919  W. H. Eccles and F. W. Jordan publish the first flipflop circuit design. 
1924  February  International Business Machines (IBM corporation) formed after more mergers involving the Computing  Tabulating  Recording Company  see 1911. By 1990 IBM had an income of around $69 Billion (and 373,816 employees), although in 1992 recession caused a cut in stock dividends (for the first time in the company's history) and the sacking of 40,000 employees. 
1930  Vannevar Bush builds a partly electronic computer capable of solving differential equations 
19311932  E. WynnWilliams, at Cambridge, England, uses thyratron tubes to construct a binary digital counter for use in connection with physics experiments. 
1935  International Business Machines introduces the "IBM 601[?]", a punch card machine with an arithmetic unit based on relays and capable of doing a multiplication in 1 second. The machine becomes important both in scientific and commercial computation, and about 1500 of them are eventually made. 
1937  Alan Turing (19121954), of Cambridge University, England, publishes a paper on "computable numbers"  the mathematical theory of computation. This paper solves a mathematical problem, but the solution is achieved by reasoning (as a mathematical device) about the theoretical simplified computer known today as a Turing machine. 
1937  George Stibitz (c.1910) of the Bell Telephone Laboratories (Bell Labs), New York City, constructs a demonstration 1bit binary adder using relays. This is 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 Jan. 1940. 
1938  Claude E. Shannon (1916) publishes a paper on the implementation of symbolic logic using relays. 
1938  Konrad Zuse (19101995) of Berlin, with some assistance from Helmut Schreyer, completes a prototype mechanical binary programmable calculator, the first binary calculator it is based on Boolean Algebra (see 1848). Originally called the "V1" but retroactively renamed "Z1" after the war. It works with floating point numbers having a 7bit exponent, 16bit mantissa, and a sign bit. The memory uses sliding metal parts to store 16 such numbers, and works well; but the arithmetic unit is less successful. The program is read from punched tape  not paper tape, but discarded 35 mm movie film. Data values can be entered from a numeric keyboard, and outputs are displayed on electric lamps. The machine is not a general purpose computer because it lacks looping capabilities. 
1939  January 1  HewlettPackard formed by William Hewlett and David Packard[?] in a garage in California. A coin toss decided the name. 
1939  November  John V. Atanasoff[?] (1903) and graduate student Clifford Berry (?1963), of Iowa State College (now the Iowa State University), Ames, Iowa, complete a prototype 16bit adder. This is the first machine to calculate using vacuum tubes. 
1939  Start of WWII. This spurred many improvements in technology  and led to the development of machines such as the Colossus (see 1943). 
1939  Zuse and Schreyer begin work on the "V2" (later "Z2"), which will marry the Z1's existing mechanical memory unit to a new arithmetic unit using relay logic. Like the Z1, the Z2 lacks looping capabilities. The project is interrupted for a year when Zuse is drafted, but then released. (Zuse is a friend of Wernher von Braun, who will later develop the *other* "V2", and after that, play a key role in the US space program.) 
1939/1940  Schreyer completes a prototype 10bit adder using vacuum tubes, and a prototype memory using neon lamps. 
1940  January  At Bell Labs, Samuel Williams[?] and Stibitz complete a calculator which can operate on complex numbers, and give it the imaginative name of the "Complex Number Calculator"; it is later known as the "Model I Relay Calculator". It uses telephone switching parts for logic: 450 relays and 10 crossbar switches. Numbers are 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 is provided with three remote keyboards, at various places in the building, in the form of teletypes. Only one can be used at a time, and the output is automatically displayed on the same one. In September 1940, a teletype is set up at a mathematical conference in Hanover, New Hampshire, with a connection to New York, and those attending the conference can use the machine remotely. 
1941  Summer  Atanasoff and Berry complete a specialpurpose calculator for solving systems of simultaneous linear equations, later called the "ABC" ("Atanasoff Berry Computer"). This has 60 50bit words of memory in the form of capacitors (with refresh circuits  the first regenerative memory) mounted on two revolving drums. The clock speed is 60 Hz, and an addition takes 1 second. For secondary memory it uses punch cards, moved around by the user. The holes are not actually punched in the cards, but burned. The punch card system's error rate is never reduced beyond 0.001%, and this isn't really good enough. (Atanasoff will leave Iowa State after the US enters the war, and this will end his work on digital computing machines.) 
1941  December  Now working with limited backing from the DVL (German Aeronautical Research Institute), Zuse completes the "V3" (later "Z3"): the first operational programmable calculator. It works with floating point numbers having a 7bit exponent, 14bit mantissa (with a "1" bit automatically prefixed unless the number is 0), and a sign bit. The memory holds 64 of these words and therefore requires over 1400 relays; there are 1200 more in the arithmetic and control units. The program, input, and output are implemented as described above for the Z1. Conditional jumps are not available. The machine can do 34 additions per second, and takes 35 seconds for a multiplication. It is a marginal decision whether to call the Z3 a prototype; with its small memory it is certainly not very useful on the equation solving problems that the DVL was mostly interested in. 
1943  Computers between 1943 and 1959 (or thereabouts  some say this era did not start until UNIVAC I in 1951) are usually regarded as 'first generation' and are based on vacuum valves or electromechanical relays, punched cards and wire circuits. All programming was done in machine code. A typical machine of the era was UNIVAC, see 1951. 
1943  "I think there is a world market for maybe five computers.", Thomas Watson, chairman of IBM. 
1943  January  The Harvard Mark I (originally ASCC Mark I, HarvardIBM Automatic Sequence Controlled Calculator) was built at Harvard University by Howard H. Aiken (19001973) and his team, partly financed by IBM  it became the first program controlled calculator. The whole machine is 51 feet long, weighs 5 tons, and incorporates 750,000 parts. It used 3304 electromechanical relays as onoff switches, had 72 accumulators (each with its own arithmetic unit) as well as mechanical register with a capacity of 23 digits plus sign. The arithmetic is fixedpoint, with a plugboard setting determining the number of decimal places. I/O facilities include card readers, a card punch, paper tape readers, and typewriters. There are 60 sets of rotary switches, each of which can be used as a constant register  sort of mechanical readonly memory. The program is read from one paper tape; data can be read from the other tapes, or the card readers, or from the constant registers. Conditional jumps are not available. However, in later years the machine is modified to support multiple paper tape readers for the program, with the transfer from one to another being conditional, sort of like a conditional subroutine call. Another addition allows the provision of plugboardwired subroutines callable from the tape. Used to create ballistics tables for the US Navy. 
1943  April  Max Newman, WynnWilliams, and their team (including Alan Turing) at the secret Government Code and Cypher School ('Station X'), Bletchley Park, Bletchley, England, complete the "Heath Robinson". This is a specialized machine for cipherbreaking, not a generalpurpose calculator or computer but some sort of logic device, using a combination of electronics and relay logic. It reads data optically at 2000 characters per second from 2 closed loops of paper tape, each typically about 1000 characters long. It was significant since it was the forerunner of Colossus, see December 1943. 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 1937 paper. 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  September  Williams and Stibitz complete the "Relay Interpolator", later called the "Model II Relay Calculator". This is a programmable calculator; again, the program and data are read from paper tapes. An innovative feature is that, for greater reliability, numbers are represented in a biquinary format using 7 relays for each digit, of which exactly 2 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 will use the biquinary notation for the digits of floatingpoint numbers.) 
1943  December  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 WWII  as a successor to April's 'Robinson's. Although 10 were eventually built, unfortunately they were destroyed immediately after they had finished their work  it was so advanced that there was to be no possibility of its design falling into the wrong hands (presumably the Russians). One of the early engineers wrote an emulation on an early Pentium  that ran at half the rate! 
1946  ENIAC (Electronic Numerical Integrator and Computer): One of the first totally electronic, valve driven, digital, computers. Development started in 1943 and finished in 1946, 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 25kW of electrical power. It could do around 100,000 calculations a second. It was used for calculating Ballistic trajectories and testing theories behind the Hydrogen bomb. 
1947  end  Invention of Transistor at The Bell Laboratories, USA, by William B. Shockley[?], John Bardeen and Walter H. Brattain[?]. 
1948  June 21  SSEM, Small Scale Experimental Machine or 'Baby' was built at Manchester University, It ran its first program on this date. Based on ideas from John von Neumann (a Hungarian mathematician) about stored program computers, 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 I. The Ferranti Mark I was basically the same as the Manchester Mark I but faster and made for commmercial sale. 
1949  EDSAC  Maurice Wilkes and a team at Cambridge University build a stored program computer. It used paper tape I/O. 
1949  EDVAC (electronic discrete variable computer)  First computer to use Magnetic Tape. All previous computers, apart from the SSEM, had to be reprogrammed by rewiring them whereas EDVAC could have new programs loaded off of the tape. Proposed by John von Neumann, it was completed in 1952 at the Institute for Advance Study, Princeton, USA. 
1949  "Computers in the future may weigh no more than 1.5 tons.", Popular Mechanics, forecasting the relentless march of science. 
1949  CSIR Mk I (later known as CSIRAC), Australia's first computer, ran its first test program. It was a vacuum tube based electronic general purpose computer. Its main memory stored data as a series of acoustic pulses in 5 foot long tubes filled with mercury. 
Computing timelines: 500 BC1949, 19501979, 19801989, 1990present
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