COMPUTER

A programmable machine. The two principal characteristics of a computer are:
· It responds to a specific set of instructions in a well-defined manner.
It can execute a prerecorded list of instructions (a program).
Modern computers are electronic and digital. The actual machinery -- wires, transistors, and circuits -- is called hardware; the instructions and data are called software.
All general-purpose computers require the following hardware components:
· memory : Enables a computer to store, at least temporarily, data and programs.
· mass storage device : Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.
· input device : Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.
· output device : A display screen, printer, or other device that lets you see what the computer has accomplished.
· central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions.