ComputerData Recovery Web Hosting In current usage, a computer is a device which is used to process information according to a well-defined procedure. The word was originally used to describe people who were employed to do arithmetic calculations, with or without mechanical aids. The famed Leibniz himself complained of the time he expended in performing calculations. Starting in the 1950s computing machine was used to refer to the machines themselves; finally, the shorter word computer took over the term computing machine. Originally, computing was almost exclusively related to arithmetical problems, but modern computers are used for many tasks unrelated to mathematics, as their cost has declined, their performance has increased and their size is reduced. Within such a definition sit mechanical devices such as the slide rule, the gamut of mechanical calculators from the abacus onwards, as well as all contemporary electronic computers. Terms better suited for such broad meanings ascribed to the word "computer" would be " information processor", "information processing system", or even "controller". However, the above definition includes many special-purpose devices that can compute only one or a limited range of functions. When considering modern computers, their most notable characteristic that distinguishes them from earlier computing devices is that, given the right programming, any computer can emulate the behaviour of any other (limited only by storage capacity and execution speed), and, indeed, it is believed that current machines can emulate any future computing devices we invent (though undoubtedly more slowly). In some sense, then, this threshold capability is a useful test for identifying "general-purpose" computers from earlier special-purpose devices. This "general-purpose" definition can be formalised into a requirement that a certain machine must be able to emulate the behaviour of a universal Turing machine. Machines meeting this definition are referred to as Turing-complete. While such machines are physically impossible as they require unlimited storage and zero crashing probability, the attribute Turing-complete is sometimes also used in a lax sense for machines that would be universal if they had more (infinite) storage and were absolutely reliable. The first such machine appeared in 1941: the program-controlled Z3 of Konrad Zuse (but its Turing-completeness was shown only much later, namely, in 1998). Other machines followed in a flurry of developments around the world. See the history of computing article for more details of this period. |
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