Computers and Computer Systems I

A computer is a programmable device that can automatically perform a sequence of calculations or other operations on data without human aid. It can store, retrieve, and process data according to internal instructions.

A computer may be analog, digital, or hybrid, although most today are digital. Digital computers express variables as numbers, usually in the binary system. They are used for general purposes, whereas analog computers are built for specific tasks, typically scientific or technical. The term "computer" is usually synonymous with digital computer, and computers for business are exclusively digital.

The core of any computer is its central processing unit (CPU), commonly called a processor or a chip. The typical CPU consists of an arithmetic-logic unit to carry out calculations; main memory to store data temporarily for processing; and a control unit to control the transfer between memory, input and output sources, and the arithmetic-logic unit.

A computer as such is not fully functional without various peripheral devices for input and output and other functions. These are typically connected to the computer through cables, although some may be built into the same unit with the CPU, and occasionally non-cable technology, such as radio frequency, is used to link peripherals. Standard input peripherals include keyboards, mice, trackballs, scanners, light pens, microphones, and magnetic strip readers. Common output devices include monitors, printers, plotters, and speakers. Modems facilitate both input and output by communicating with other computers. Other types of peripherals include data storage devices like tape drives or optical disk drives for expanded storage capabilities or system backups.

Finally, for a digital computer to function automatically, it requires programs, or sets of instructions written in computer-readable code. This necessary component is commonly known as software.

The distinction between a computer and a computer system is largely academic, since the terms are used interchangeably. The familiar desktop computer set-up is technically a system, since nearly all such computers are used with at least a couple of the peripherals mentioned above. The notion of a standalone computer may be foreign to many people, but for business and technical purposes there are of course specialized computers that don't require such devices to serve their functions.