1. [n]  a machine for performing calculations automatically
2. [n]  an expert at calculation (or at operating calculating machines)

Computer
A sweeping saga of colorful geniuses, Rube Goldberg- type devices, false starts, dead ends, and serendipitous breakthroughs, this definitive history by two renowned scholars tells the real story of how the computer came to be. Most people trace the origins of the computer to three people: Alan Turing, the World War II cryptologist; John von Neumann, the father of scientific computing; and Steve Jobs, the popularizer of the personal computer. They`re wrong. The true story is much more complex, and infinitely more interesting. It begins at a time when computers were people, when women numbering in the hundreds sat together in a crowded room performing simple tasks and functioning as a whole, as a giant information-processing machine. From this humble beginning, the digital electronic marvel of today began to take shape. Here is the story of such early pioneers as William Mauchley, who tried to build a machine that would enable racetracks to post up-to-the-last-minute odds, and the riveting tale of Jay Forrester, whose determination to build a flight simulator led to the development of the first successful real-time computer. Flowing like a page-turning thriller, with each unlikely piece of the computers development falling into place, this fully documented, myth-breaking history finally sets the record straight and gives proper credit to the unsung heroes of the computer revolution.

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A machine that can be programmed to manipulate symbols. Computers can perform complex and repetative procedures quickly, precisely and reliably and can quickly store and retrieve large amounts of data.

The physical components from which a computer is constructed (electronic circuits and input/output devices) are known as "hardware". Most computers have four types of hardware component: CPU, input, output and memory. The CPU (central processing unit) executes programs ("software") which tell the computer what to do. Input and output (I/O) devices allow the computer to communicate with the user and the outside world. There are several kinds of memory - fast, expensive, short term memory (e.g. RAM) to hold intermediate results, and slower, cheaper, long-term memory (e.g. magnetic disk and magnetic tape) to hold programs and data between jobs.

See also analogue computer.