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UNIT 27 - OPERATING SYSTEMS
Types of Operating Systems
Within the range of operating
systems, there are generally four types, categorised based on the types
of computers they control and the sort of applications they support. These
are:
- Real-time operating system - used to control machinery, scientific
instruments and industrial systems. An RTOS typically has limited user-interface
capability, and no end-user utilities. An important part of an RTOS
is managing the resources of the computer so that a particular operation
executes in precisely the same amount of time every time it occurs.
In a complex machine, having a part move more quickly just because system
resources are available may be just as catastrophic as having it not
move at all because the system is busy.
- Single-user, single task -this operating system is designed to manage
the computer so that one user can effectively do one thing at a time.
The Palm OS for Palm handheld computers is a good example of a modern
single-user, single-task operating system.
- Single-user, multi-tasking - This is the type of operating system
most people use on their desktop and laptop computers. Microsoft's Windows
and Apple's MacOS are both examples of operating systems that will let
a single user have several programs in operation at the same time. For
example, it's possible for a Windows user to be writing a note in a
word processor while downloading a file from the Internet while printing
the text of an e-mail message.
- Multi-user - A multi-user operating system allows many different
users to take advantage of the computer's resources simultaneously.
The operating system must make sure that the requirements of the various
users are balanced, and that each of the programs they are using has
sufficient and separate resources so that a problem with one user doesn't
affect the entire community of users. Unix, VMS and mainframe operating
systems, such as MVS, are examples of multi-user operating systems.
It's important to differentiate
between multi-user operating systems and single-user operating systems
that support networking. Windows 2000 and Novell Netware can each support
hundreds or thousands of networked users, but the operating systems themselves
aren't true multi-user operating systems. The system administrator is
the only "user" for Windows 2000 or Netware. The network support
and all of the remote user logins the network enables are, in the overall
plan of the operating system, a program being run by the administrative
user.
With the different types of operating systems in mind, it's time to look
at the basic functions provided by an operating system.
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