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operating system
Last modified: Friday, January 04, 2002 

operating system
The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.

Operating systems can be classified as follows:

  • multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
  • multiprocessing : Supports running a program on more than one CPU.
  • multitasking : Allows more than one program to run concurrently.
  • multithreading : Allows different parts of a single program to run concurrently.
  • real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.
  • Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.

    As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.

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    For pages about operating system . Also check out the following links!

    Related Links

    DOS concepts and functions 
    This page is for novice computer users and provides a short introduction to computers and basic functions of an operating system. A table of contents then provides links to specific DOS concepts and functions.

    Virtual Doctor 
    Using the Virtual Doctor, users can acquire help with a specific problem, download software, grab updates for their operating system or receive expert tutorials catering to their specific needs.

    ACM SIG Operating Systems
    Addresses a broad spectrum of issues associated with operating systems research and development.

    CMX-RTX real time operating system
    Product feature page for the CMS-RTX real time multitasking operating system for microprocessors and microcomputers.

    OS News
    On-line magazine covering alternative operating systems and computing environments.

    Daily computer and operating system news and opinion commentary.

    Real-Time and RTOS Computing Resources
    List of sites related to real time operating systems and programming.

    RTMX operating system information page
    Provides product information for the RTMX real time operating system, including features and supported CPU types. In addition, there are links to related real time computing Web sites.

    Yahoo!'s operating systems page
    Yahoo!'s directory of links to operating systems.

    Yahoo!'s OS/2 operating system page
    Yahoo!'s directory of the OS/2 operating system.

    Yahoo!'s real time systems page
    Yahoo!'s directory of real time systems.

    Yahoo!'s UNIX page
    Yahoo!'s directory of UNIX operating systems links.

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    eBay: Operating Systems - Online marketplace for buying and selling operating systems. Operating Systems Comparison Shopping - offers price comparisons, consumer reviews, product features, and store ratings from over 2,000 stores across the web.

    related categories

    Operating Systems

    related terms





    command processor


    fatal exception error

    file management system

    flat file system



    Mac OS

    Microsoft Windows











    Windows 2000

    Windows CE

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