What is 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.

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

Computers can be generally classified by size and power as follows, though there is considerable overlap:

• personal computer : A small, single-user computer based on a microprocessor. In addition to the microprocessor, a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.

• workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.

• minicomputer : A multi-user computer capable of supporting from 10 to hundreds of users simultaneously.

• mainframe : A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.

• supercomputer : An extremely fast computer that can perform hundreds of millions of instructions per second.

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About The Computer Society

With nearly 90,000 members, the IEEE Computer Society is the world's leading organization of computer professionals. Founded in 1946, it is the largest of the 39 societies of the IEEE.

The IEEE Computer Society's vision is to be the leading provider of technical information, community services, and personalized services to the world's computing professionals.

The Society is dedicated to advancing the theory, practice, and application of computer and information processing technology. Through its conferences, applications-related and research-oriented journals, local and student chapters, e-learning campus, technical committees, and standards working groups, the Society promotes an active exchange of information, ideas, and technological innovation among its members. In addition, the Society maintains close ties with the US Computing Sciences Accreditation Board and Accreditation Board for Engineering and Technology, monitoring and evaluating curriculum accreditation guidelines.

With about 40 percent of our members living and working outside the United States, the Computer Society fosters international communication, cooperation, and information exchange. To meet the needs of our members conveniently and efficiently, the Society maintains a service center office in Tokyo, Japan; a publications office in Los Alamitos, California; and its headquarters in Washington, DC.

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