US-CERT Cyber Security Tip ST04-021 -- Understanding Your Computer: Operating Systems

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                      Cyber Security Tip ST04-021
             Understanding Your Computer: Operating Systems

   The operating system is the most fundamental program that runs on your
   computer. It serves as the basis for how everything else works.

What is an operating system?

   An operating system (OS) is the main program on a computer. It
   performs a variety of functions, including

     * determining what types of software you can install

     * coordinating the applications running on the computer at any given
       time

     * making sure that individual pieces of hardware, such as printers,
       keyboards, and disk drives, all communicate properly

     * allowing applications such as word processors, email clients, and
       web browsers, to perform tasks on the system (e.g., drawing
       windows on the screen, opening files, communicating on a network)
       and utilize other system resources (e.g., printers, disk drives)

     * reporting error messages

   The OS also determines how you see information and perform tasks. Some
   operating systems utilize a graphical user interface (GUI), which
   presents information through pictures (icons, buttons, dialog boxes,
   etc.) as well as words. Other operating systems can rely solely on
   text.

How do you choose an operating system?

   In very simplistic terms, when you choose to buy a computer, you are
   usually also choosing an operating system. Although you may change it,
   vendors typically ship computers with a particular operating system.
   There are multiple operating systems, each with different features and
   benefits, but the following three are the most common:

     * Windows - Windows, with versions including Windows Me, Windows
       2000, and Windows XP, is the most common operating system for home
       users. It is produced by Microsoft and is typically included on
       machines purchased in electronics stores or from vendors such as
       Dell or Gateway. The Windows OS uses a GUI, which many users find
       more appealing and easier to use than text-based interfaces.

     * Mac OS X - Produced by Apple, Mac OS X is the operating system
       used on Macintosh computers. With the exception of a different
       GUI, it is similar to the Windows interface in the way it
       operates.

     * Linux and other UNIX-derived operating systems - Linux and other
       systems derived from the UNIX operating system are frequently
       utilized for specialized workstations and servers, such as web and
       email servers. Because they often more difficult for general users
       or require specialized knowledge and skills to operate, they are
       not very popular with home users. However, as they continue to
       develop and become easier to use, they may become more popular on
       typical home user systems.
     _________________________________________________________________

     Authors: Mindi McDowell, Chad Dougherty
     _________________________________________________________________

     This document can also be found at
       
     <http://www.us-cert.gov/cas/tips/ST04-021.html>
       
     Copyright 2004 Carnegie Mellon University
       
     Terms of use
       
     <http://www.us-cert.gov/legal.html>
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