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A computer is a machine for manipulating data according to a list of instructions - a program. more...

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Computers are versatile. In fact, they are universal information processing machines. According to the Church-Turing thesis, a computer with a certain minimum threshold capability is in principle capable of performing the tasks of any other computer, from those of a personal digital assistant to a supercomputer, as long as time and memory capacity are not considerations. Therefore, the same computer designs have been adapted for tasks from processing company payrolls to controlling unmanned spaceflights. Modern electronic computers also have enormous speed and capacity for information processing compared to earlier designs, and they have become exponentially more powerful over the years (a phenomenon known as Moore's Law).

Computers are available in many physical forms. The original computers were the size of a large room, and such enormous computing facilities still exist for specialized scientific computation — supercomputers — and for the transaction processing requirements of large companies, generally called mainframes. Smaller computers for individual use, called personal computers, and their portable equivalent, the laptop computer, are ubiquitous information-processing and communication tools and are perhaps what most non-experts think of as "a computer". However, the most common form of computer in use today is the embedded computer, small computers used to control another device. Embedded computers control machines from fighter planes to digital cameras.

History of computing

Originally, the term "computer" referred to a person who performed numerical calculations under the direction of a mathematician, possibly with the aid of a variety of mechanical calculating devices such as the abacus onward. Examples of early calculating devices, the first ancestors of the computer, included the abacus and the Antikythera mechanism, an ancient Greek device for calculating the movements of planets, dating from about 87 BCE . The end of the Middle Ages saw a reinvigoration of European mathematics and engineering, and Wilhelm Schickard's 1623 device was the first of a number of European engineers to construct a mechanical calculator .

Charles Babbage was the first to conceptualize and design a fully programmable computer as early as 1820, but due to a combination of the limits of the technology of the time, limited finance, and an inability to resist tinkering with his design, the device was never actually constructed in his lifetime. A number of technologies that would later prove useful in computing, such as the punch card and the vacuum tube had appeared by the end of the 19th century, and large-scale automated data processing using punch cards was performed by tabulating machines designed by Hermann Hollerith.

Read more at Wikipedia.org