A Short History On Computers Essay Research — страница 2

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generation of relay computers. ENIAC used 18,000 vacuum tubes, about 1,800 square feet of floor space, and consumed about 180,000 watts of electrical power. It had punched card I/O, 1 multiplier, 1 divider/square rooter, and 20 adders using decimal ring counters, which served as adders and also as quick-access (.0002 seconds) read-write register storage. ———————————————————————— The Modern Stored Program EDC Fascinated by the success of ENIAC, the mathematician John Von Neumann (left) undertook, in 1945, an abstract study of computation that showed that a computer should have a very simple, fixed physical structure, and yet be able to execute any kind of computation by means of a proper programmed control without the need for any

change in the unit itself. Von Neumann contributed a new awareness of how practical, yet fast computers should be organized and built. These ideas, usually referred to as the stored – program technique, became essential for future generations of high – speed digital computers and were universally adopted. The Stored – Program technique involves many features of computer design and function besides the one that it is named after. In combination, these features make very – high – speed operation attainable. If each instruction in a job program were used once in consecutive order, no human programmer could generate enough instruction to keep the computer busy. Also, it would clearly be helpful if instructions could be changed if needed during a computation to make them

behave differently. The all – purpose computer memory became the assembly place in which all parts of a long computation were kept, worked on piece by piece, and put together to form the final results. The computer control survived only as an “errand runner” for the overall process. The first generation of modern programmed electronic computers to take advantage of these improvements were built in 1947. This group included computers using Random – Access – Memory (RAM), which is a memory designed to give almost constant access to any particular piece of information. . These machines had punched – card or punched tape I/O devices and RAM’s of 1,000 – word capacity and access times of .5 Greek MU seconds (.5*10-6 seconds). Physically, they were much smaller than

ENIAC. The first – generation stored – program computers needed a lot of maintenance, reached probably about 70 to 80% reliability of operation (ROO) and were used for 8 to 12 years. This group of computers included EDVAC (above) and UNIVAC (below) the first commercially available computers. ———————————————————————— Advances in the 1950’s Early in the 50’s two important engineering discoveries changed the image of the electronic – computer field, from one of fast but unreliable hardware to an image of relatively high reliability and even more capability. These discoveries were the magnetic core memory and the Transistor – Circuit Element. These technical discoveries quickly found their way into new models of digital

computers. RAM capacities increased from 8,000 to 64,000 words in commercially available machines by the 1960’s, with access times of 2 to 3 MS (Milliseconds). Magnetic drums, magnetic – disk packs, or magnetic tapes were usually used. When the computer finishes with a problem, it “dumps” the whole problem (program and results) on one of these peripheral storage units and starts on a new problem. Another mode for fast, powerful machines is called time-sharing. In time-sharing, the computer processes many jobs in such rapid succession that each job runs as if the other jobs did not exist, thus keeping each “customer” satisfied. ———————————————————————— Advances in the 1960’s In the 1960’s, efforts to design and

develop the fastest possible computer with the greatest capacity reached a turning point with the LARC machine, built for the Livermore Radiation Laboratories of the University of California by the Sperry – Rand Corporation, and the Stretch computer by IBM. The LARC had a base memory of 98,000 words and multiplied in 10 Greek MU seconds. ———————————————————————— More Recent Advances The trend during the 1970’s was, to some extent, moving away from very powerful, single – purpose computers and toward a larger range of applications for cheaper computer systems. Most continuous-process manufacturing, such as petroleum refining and electrical-power distribution systems, now used computers of smaller capability for controlling and