Operating Systems 182
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A computer's operating system is one of the most important "parts" of the computer. Almost every type of computer, including cellular telephones, needs an operating system in order to operate properly. When one turns on a computer, the operating system tells the computer what to do by controlling the system resources such as the processor, memory, disk space, etc. The operating system allows the user to work on the computer without having to know all the details about how the hardware works.

When choosing an operating system for a business, the primary considerations should be the hardware platform used, the number of users and attendant system security requirements, the ease of administration, the adaptability toward different uses, and the different applications that will be employed.


Most simple, single-function computers (such as in microwave ovens with digital keypads) do not require an operating system. In fact, trying to implement an operating system in these computers would be overkill. On the other hand, all personal desktop and laptop computers and servers do require an operating system. While there are hundreds of operating systems available, the most popular by far are the Microsoft Windows family of operating systems, the Macintosh operating system, and the Unix family of operating systems.

There are four general types of operating systems. Their use depends on the type of computer and the type of applications that will be run on those computers.

  1. Real-time operating systems (RTOS) are used to control machinery, scientific instruments, and industrial systems. In general, the user does not have much control over the functions performed by the RTOS.
  2. Single-user, single task operating systems allow one user to do one thing at a time. And example of a single-user, single task operating system is the operating system used by personal digital assistants (PDAs), also known as handheld computers.
  3. Single-user, multi-tasking operating systems allow a single user to simultaneously run multiple applications on their computer. This is the type of operating system found on most personal desktop and laptop computers. The Windows (Microsoft) and Macintosh (Apple) platforms are the most popular single-user, multi-tasking operating systems.
  4. Multi-user operating systems allow multiple users to simultaneously use the resources on a single computer. Unix is an example of a multi-user operating system.


One of the operating system's main tasks is to control the computer's resources—both the hardware and the software. The operating system allocates resources as necessary to ensure that each application receives the appropriate amount. In addition to resource allocation, operating systems provide a consistent application interface so that all applications use the hardware in the same way. This is particularly important if more than one type of computer uses the operating system or if the computer's hardware is likely to change. By having a consistent application program interface (API), software written on one computer and can run on other types of computers. Developers face the challenge of keeping the operating system flexible enough to control hardware from the thousands of different computer manufacturers.

Operating systems must accomplish the following tasks:

  1. Processor management. The operating system needs to allocate enough of the processor's time to each process and application so that they can run as efficiently as possible. This is particularly important for multitasking. When the user has multiple applications and processes running, it is up to the operating system to ensure that they have enough resources to run properly.
  2. Memory storage and management. The operating system needs to ensure that each process has enough memory to execute the process, while also ensuring that one process does not use the memory allocated to another process. This must also be done in the most efficient manner. A computer has four general types of memory. In order of speed, they are: high-speed cache, main memory, secondary memory, and disk storage. The operating system must balance the needs of each process with the different types of memory available.
  3. Device management. Most computers have additional hardware, such as printers and scanners, connected to them. These devices require drivers, or special programs that translate the electrical signals sent from the operating system or application program to the hardware device. The operating system manages the input to and output from the computer. It often assigns high-priority blocks to drivers so that the hardware can be released and available for the next use as soon as possible.
  4. Application interface. Programmers use application program interfaces (APIs) to control the computer and operating system. As software developers write applications, they can insert these API functions in their programs. As the operating system encounters these API functions, it takes the desired action, so the programmer does not need to know the details of controlling the hardware.
  5. User interface. The user interface sits as a layer above the operating system. It is the part of the application through which the user interacts with the application. Some operating systems, such as Microsoft Windows and Apple Macintosh, use graphical user interfaces. Other operating systems, such as Unix, use shells.


Windows is the name of a family of operating systems created by the Microsoft Corporation for use with personal computers. Windows employs a graphical user interface (GUI), which eliminates the need for the user to learn complex commands. With a GUI, the user instructs the operating system by using a mouse to point and click icons that are displayed on the screen. Microsoft Windows, first released in 1985, was originally designed as a GUI for DOS, which uses the command-line approach. In order to communicate with the computer, DOS users must type commands or instructions at the command prompt, and then the command-line interpreter executes those commands. The term "DOS" can refer to any operating system, but it is frequently used as a synonym for Microsoft Disk Operating System (MS-DOS). DOS has limited use with modern computer systems and applications because it does not support multiple users or multitasking. Some of the other operating systems, including Windows, can also execute DOS-based applications. Today, most DOS systems have been replaced by more user-friendly systems that use a GUI.

Windows 3.1 was released in 1991. By then, Windows had gained in market share. Microsoft released Windows 95 in August 1995. It was so well marketed and in such high demand that people bought the operating system, even if they didn't own a home computer. With each new release, from Windows 98 to Window 2000 to Windows XP, Microsoft gained popularity. Today, almost every new personal computer comes preloaded with the Windows operating system. Windows can be run on practically any brand of personal computers. It is estimated that 90 percent of personal computers run the Windows operating system. The remaining 10 percent run the Macintosh operating system.

UNIX is a multi-user, multitasking operating system, and was designed to be a small, flexible system used by computer programmers. Since UNIX was designed to be used by programmers, it is not considered to be very user-friendly for the average person. However, graphical user interfaces have been developed for UNIX to help alleviate the ease-of-use issue.

Linux is a UNIX variant that runs on several different hardware platforms. Linus Torvalds, a student at the University of Helsinki in Finland, initially created it as a hobby. The kernel, at the heart of all Linux systems, is developed and released under the General Public License (GNU), and its source code is freely available to everyone. There are now hundreds of companies, organizations, and individuals that have released their own versions of operating systems based on the Linux kernel.

Because of its functionality, adaptability, and robustness, Linux is able to compete against the Unix and Microsoft operating systems. IBM, Hewlett-Packard, and other computer giants have embraced Linux and support its ongoing development. More than a decade after its initial release, Linux is being adopted worldwide mainly as a server platform. More and more people are starting to use Linux as a home and office desktop operating system. The operating system can also be incorporated directly into microchips in a process called "embedding." Many appliances and devices are now starting to use operating systems in this way.

SEE ALSO: Computer Networks ; Computer Security ; Computer-Integrated Manufacturing ; Data Processing and Data Management ; Management Information Systems

Rhoda L. Wilburn


Coustan, Dave, and Curt Franklin. How Operating Systems Work. How Stuff Works, Inc., 2005. Available from < http://computer.howstuffworks.com/operating-system.htm >.

What is Linux? Linux Online. Available from < http://www.linux.org >.

Also read article about Operating Systems from Wikipedia

User Contributions:

this article is good one.it contains all the details in brief and consize form.
but ya there should be diagram representation..

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