The operating system is 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, keeping track of files, and controlling devices such as disk drives and printers.
Most desktop or laptop PCs come pre-loaded with Microsoft Windows. Macintosh computers come pre-loaded with Mac OS X. Many corporate servers use the Linux or UNIX operating systems.
Types of operating systems
Real-time
A real time operating system is a
multitasking operating system that aims at executing real-time applications.
Real-time operating systems often use specialized scheduling algorithms so that
they can achieve a deterministic nature of behavior. The main objective of
real-time operating systems is their quick and predictable response to events.
They have an event-driven or time-sharing design and often aspects of both. An
event-driven system switches between tasks based on their priorities or
external events while time-sharing operating systems switch tasks based on
clock interrupts.
Multi-user
A multi user
operating system allows multiple users to access a computer system at the same
time. Time-sharing systems and Internet servers can be classified as multi-user
systems as they enable multiple-user access to a computer through the sharing
of time. Single-user operating systems have only one user but may allow
multiple programs to run at the same time.
Multi-tasking vs. single-tasking
A multi tasking operating system allows more than one program to be running at the same time,
from the point of view of human time scales. A single-tasking system has only
one running program. Multi-tasking can be of two types: pre-emptive and
co-operative. In pre-emptive multitasking, the operating system slices the CPU
time and dedicates one slot to each of the programs.
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