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Monday, 7 November 2011

computer



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.



  • Modern Computers:

    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.

    Computer Classification:

    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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