Main types of computer

I, Computer: Definition

A computer is a machine that can be programmed to manipulate symbols. Its principal characteristics are:

It responds to a specific set of instructions in a well-defined manner.

It can execute a prerecorded list of instructions (a program).

It can quickly store and retrieve large amounts of data.

All general-purpose computers require the following hardware components:

Central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions organized in programs ("software") which tell the computer what to do.

Memory (fast, expensive, short-term memory): Enables a computer to store, at least temporarily, data, programs, and intermediate results.

Mass storage device (slower, cheaper, long-term memory): Allows a computer to permanently retain large amounts of data and programs between jobs. 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.

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.

II, Computer sizes and power

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.

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

Minicomputer: A multi-user computer capable of supporting up 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.