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    Generation of Computer

    First Generation:The first large electronic computer was completed in 1946 by a team lad by eckert and Mauchly at the University of Pennysylvania in U.S.A.This computer called electronic numerical integrator and caclulator(ENIAC) used high speed vaccum tubes switching devices.It had a very small memory and was designed primarily to calculate the switching devices.
    Second Generation:A big revolution in electronics took place with in the invention of transistors by Bardeen,Brattain and shockely in 1947.Trasistors made of germaninium semiconductos material weee highly reliable compared to tubes since trasistors had no filament to burnj.They occupied less space and used only a tenth of the power required by tubes.They also could switch from a 0,1 to a 1 state in a few microseconds about tenth of time needed by tubes.
    Third Generation: The third generation began in 1965 with germanium trasistors being replaced by silicon transistors.Integrated circuits circuits consisting of trasistors resistors and capacitors grown on a single chip of silicon eliminating wired interconnectin between components emerged.
    Fourth Generation:First decade(1876-1985)The fourth generation may be identified by the the advent of the microprocessor chip.Medium scale integrated circuits yieleded Large-scale Integrated (VLSI)circuits packing about 50000 transistors in a chip.Magnetic core memories were replced by semiconductors memories.In SECONd PHASE(1986-2000)the sewcond phase of fourth generation has seen a relentless increase in the speed of microprocessors and the size of main memory.The speed of microprocessors and the size ofmain memory and hard disk went up by a factor 4 every 3 years.
    Fifth Generation:It was early 90's that anew generartion computer will emerge which will have an architecture radically different from Von Neumann architecture. The goal was to have a machine which will allow specification oriented programming and incorporate artificial intelligence features.Meanwhile th relentless increase in number of trasistors which could be palced in a single chip went on.A processor architecture called very large instruction word (VLIW)processor with an instruction size of 128 to 256 bits and which can execute several parallel instruction emerged.

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