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General-purpose computers need an operating system in order to run other programs. An operating system runs the computer and is the first software that is seen when the computer is switched on and the last when it is turned off.

The operating system carries out tasks, some of which include:
  • Controlling the computer hardware.
  • Monitoring and recognising keyboard inputs.
  • Sending output to the computer screen.
  • Managing software resources and providing a stable and consistent interface for applications to interact with hardware.


The first operating system was developed at Massachusetts Institute of Technology (MIT) in 1963 and was called the Compatible Time Sharing System (CTSS). This was then followed by the release of the Multics operating system, which came about as of a result of the collaboration of General Electric and AT&T Bell Laboratories.

AT&T however pulled out of the project in 1969 and went on to produce the Unix operating system, which has grown to become one of the mostly used operating system. There are several versions of Unix now available, thanks mostly to the fact that AT&T made the source code available to universities, used in many systems from supercomputers down to desktop personal computers (PCs).

Operating systems for the PCs did not really start till IBM started selling them in 1981. It offered several choices of operating systems to used on their products, amongst which was the PC ODS, which was developed by then a small company called Microsoft Corp. Microsoft has since grown from strength to strength to become the largest software company worldwide and now produces the most commonly used desktop operating system – Windows.

Microsoft along with IBM also developed the multitasking PC system, OS/2, in 1987 but the relationship fell apart in 1990, and Microsoft went on to produce Windows NT, most of which resulted from the OS/2 work it had done. Windows NT is popular operating systems for servers running on the Web.

However Windows is not having it all its way as it is beginning to face competition from the Linux operating system. Linux was developed in 1991 by Linus Torvaldis, who was at the time a student at the University of Helsinki, Finland. It started off as a class project which was meant to clone a Unix systems that could run on a PC. Now with help from other programmers on the Internet, Linux is a free full-scale operating system that is not only run on more Internet Web servers than any other operating system, but on almost all platforms from handhelds to mainframes.

Operating system can generally be classified into the following categories

  • Real-time operating system (RTOS): Real-time operating systems respond to input instantly and are used in computers found in machinery, scientific instruments and industrial systems.

  • Single-user, single-task operating system: Found in computers that allow the user to do only one thing at any one time. A good example is the PalmOS found in Palm handheld devices.

  • Single-user, multitasking operating system: Found in desktop and laptop computers and allows for one user to do more than one thing concurrently. Apple’s MacOS is an example.

  • Multi-user operating systems: The multi-user operating system allows fro more than one user to run one than one program at the same time. The operating systems does a juggling act to maintain each user’s resources, so if there is a problem with one user, it does not affect the others. A good example is Unix.

Common Operating Systems

Microsoft Products

  • Windows 95 – designed for the workstation, released in August 1995, support was for it was withdrawn in June 2001.

  • Windows 98 – designed for the workstation, released in May 1998, support was for it was withdrawn in June 2001.

  • Windows NT series– designed for both workstations and servers. Similar in appearance to Windows 98 but more robust with advanced security and administration. Released in 1995, supports end in April 2003, coinciding with the introduction of Microsoft's lastest product Windows Server 2003.

  • Windows 2000 series – Microsoft’s current flagship product. A follow-up to the Windows NT series. Introduced in February 2000.

  • Windows ME – A follow-up of Windows 98, released in September 2001, Microsoft stopped shipping copies of it in March 2001.

  • Windows XP – A follow-up to the Windows 2000 series and includes Microsoft’s .NET initiative.

  • Windows CE – Operating systems targeting handheld devices and other embedded systems.

Linux Variants

  • Red Hat – a well-rounded version of Linux, includes many applications. First released in 1994. Targets workstations and servers.

  • Corel – First released in 1998 by Corel. In 2001, Xandros acquired Corel Linux Business Division, and changed the operating system's name to Xandros. Targets workstations.

  • Debian Linux – First released in August 1993 and was developed by over 500 developers who volunteered from around the world. Targets workstations and servers.

  • Mandrake - targets both workstations and servers.

  • Caldera - targets both workstations and servers.

  • SuSE Linux - targets both workstations and servers.

Unix Variants

  • AIX – AIX is short for Advanced Interactive eXecutive and was introduced by IBM in February 1990. Designed for medium to large-scale servers and mainframes. Also works in workstations.

  • BSD – short for Berkeley Software Distribution. The Computer System Research Group at the University of California at Berkeley developed it in 1977. Comes in various flavours – BSD Internet Server (BSD/OS), FreeBSD, NetBSD and OpenBSD. They target all platforms from handhelds to servers.

  • DYNIX/ptx – Developed by IBM and was designed mainly for high-end commercial database management systems (DBMS) environments.

  • HP-UX – Developed by Hewlett Packard in 1986. Forms the foundation for many mission critical applications and IT services over the Internet.

  • MINIX – Free Unix clone that does not contain any of AT&T ‘ s code. Due to its small size, it is ideal for PCs.

  • Sun Solaris – Designed by Sun Microsystems. It runs on both workstations and servers.

Other Operating Systems

  • MacOS – Developed by Apple Computers to run on its computers, which range from handhelds to servers. Its desktop version was the first operating systems to adopt the ‘windows’ format.

  • OS/2 – Originally designed by IBM and Microsoft in 1987. However Microsoft pulled out of the partnership three years later and only IBM supports the later versions. Targets servers and workstations.

  • Netware – First released by Novell in 1984. Runs only on servers.

  • Palm OS – Produced by Palm Inc, which was formed in 1992. Designed to run on the popular Palm handheld devices.

  • Symbian OS – Was previously known by the name of EPOC, which was developed by Psion in 1981 to run on its handheld devices. However in 1998, Psion formed a partnership with major mobile makers and Symbian was born. It was to run on handheld devices and mobiles phones. However in 2001, Psion announced it was to stop manufacturing of its handheld devices and Symbian OS has now become one of the driving forces behind the smart phones.



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Last Updated: 10 August 2006.

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