An electronic tool that manipulates information by a predefined sequence of instructions. Computers have a simple ‘brain,’ called the central processing unit (CPU). That can do arithmetic and make decisions based on the results, and a memory stores the instructions and information. Strictly speaking, all other parts of a computer system are peripheral devices. But in practice, all computers have at least: an input device, such as a keyboard, using which the information is fed in; an output device, such as a screen or printer, which displays the results of their work; and extra memory in the form of magnetic disks or magnetic tape, called backing store. Inside a computer, both information and instructions are represented by binary numbers (see BINARY NOTATION), and an ll processing is done using these numbers. A computer needs to be given detailed instructions. Called a program before it can perform even the simplest task. The art of com posing these instructions is called *com puter programming. The general term for the programs that a computer needs to operate is software, while the computer and devices attached to it are called *hardware.
Traditionally. Computers have been classified into three types according to size. The largest is the *mainframe used typically for large-scale corporate data processing, and the smallest is the *per sonal computer, designed for a single user. Between these extremes is the*minicomputer. However, these distinctions have become blurred, as minicomputers and personal computers become more power ful. Moreover, mainframe and minicom puters have been replaced in many situations by groups of personal comput ers linked to form *local area networks.
Formerly, this type of machine was called a digital computer to distinguish it from other computing devices, such as the analog computer. The term ‘com puter’ is now synonymous with ‘digital computer,’ rarely used.
