What is a Computer?

A computer is a programmable machine that responds to instructions in a set manner. It can execute a prerecorded list of instructions (a program).

The actual equipment — wires, transistors, and circuits — is called hardware; the instructions and data are called software and are stored in files.

Computers have the following components:

• memory to store temporarily data and programs.


• a mass storage device to permanently store data. Common mass storage devices include disk drives and CD-ROMs.


• input devices such as a keyboard and mouse, so you can enter data and instructions into a computer.


• output devices such as a monitor (screen), printer, or other device that lets you see what the computer has accomplished.


• central processing unit (CPU): The part of the computer that executes instructions (does the computing).


• operating system: a program that lets you access the computer's contents and that runs programs.


• applications: programs that accomplish a specific purpose to help you get your work done (such as word processing or calculating formulas).