A computer is an electrical machine that can both process and store information. The information may consist of numbers, words, or both. Thus, the computer performs a wide variety of services controlled by inputting commands initiated by the users. The most commonly used inputting methods are keyboard and pointing device (e.g., a mouse).

The computer system is composed of hardware and software. Hardware consists of printed circuits, CPU (Central Processing Unit), memory chips, storage devices, connection ports, keyboards, printers, scanners, and monitors. Software consists of digital bits downloaded onto the storage devices. All pieces of hardware connected to the main unit, which houses the CPU, are called peripherals.

Software is sold in packages that are designed to perform different tasks commanded by the user(s) of the computer. One piece of software is called the operating system. This piece of software is crucial to the operation of the computer, as it acts as an interpreter between the machine (actually the machine language) and the wide variety of software that are designed to perform specific tasks.

Computers first began to be commercially used in the early 1950s. Computers first began to be widely used at home (therefore were given the name personal computers, or PCs) in the late 1970s with the introduction of the Apple II by Apple Computers. Earlier brands existed before the Apple II, but were not adopted on a large scale. The Apple II was the first personal computer to be supported by over 500 software packages written specifically for its operating system.