【正文】 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。 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. 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, 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 will do just that. They will use ponents of modern construction, but with tolerances no better than Clement could have provided... and, after a bit of tinkering and detaildebugging, they will find that the machine does indeed work.) 1848 British Mathematician Gee Boole devised binary algebra (Boolean algebra) paving the way for the development of a binary puter almost a century later. See 1939. 1853 To Babbage’s delight, the Scheutzes plete 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。 it’s useful for any function that can be approximated by a polynomial over suitable intervals. Mueller’s attempt to raise funds fails and the project is fotten. 1801 JosephMaire Jacuard 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。 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。 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 earliest Programmable Electronic Computer first ran (in Britain), it contained 2400 Vacuum tubes for logic, and was called the Colossus. It was built, by Dr Thomas Flowers at The Post Office Research Laboratories in London, to crack the German Lorenz (SZ42) Cipher used by the ’Enigma’ machines. Colossus was used at Bletchly Park during WWII as a successor to April’s ’Robinson’s. It translated an amazing 5000 characters a second, and used punched tape for input. 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 it’s design falling into the wrong hands (presumably the Russians). One of the early engineers wrote an emulation on an early Pentium that ran at 1/2 the rate! 1946 ENIAC (Electronic Numerical Integrator and Computer): One of the first totally electronic, valve driven, digital, puters. 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 widely recognised as the first Universal Electronic Computer. 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 (UK), It ran it’s first program on this date. Based on ideas from Jon von Neumann (a Hungarian Mathematician) about stored program puters, it was the first puter to store both it’s programs and data in RAM, as modern puters so. By 1949 the ’Baby’ had grown, and aquired a magentic drum for more perminant 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 mmercial sale. 1949 May 6 Wilkes and a team at Cambridge University build a stored program puter EDSAC. It used paper tape I/O, and was the first storedprogram puter to operate a regular puting service. 1949 EDVAC (electronic discrete variable puter) First puter to use Magic Tape. This was a breakthrough as previous puters had to be reprogrammed by rewiring them whereas EDVAC could have new programs loaded off o