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Unit 7: Windows Operating Systems

7.1 Definition of Windows Operating Systems
Notes
An operating system (OS) is a set of programs that manage computer hardware resources and
provide common services for application software. The operating system is the most important
type of system software in a computer system. A user cannot run an application program on the
computer without an operating system, unless the application program is self booting.
Time-sharing operating systems schedule tasks for efficient use of the system and may also include
accounting for cost allocation of processor time, mass storage, printing, and other resources.
For hardware functions such as input and output and memory allocation, the operating system acts
as an intermediary between application programs and the computer hardware, although the
application code is usually executed directly by the hardware and will frequently call the OS or be
interrupted by it. Operating systems are found on almost any device that contains a computer—
from cellular phones and video game consoles to supercomputers and web servers.
Examples of popular modern operating systems include Android, iOS, Linux, Mac OS X,
and Microsoft Windows.

Types
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 vs. Single-user
A multi-user operating system allows multiple users to access a computer system concurrently.
Time-sharing system can be classified as multi-user systems as they enable a multiple user access to
a computer through the sharing of time. Single-user operating systems, as opposed to a multi-user
operating system, are usable by a single user at a time. Being able to have multiple accounts on a
Windows operating system does not make it a multi-user system. Rather, only the network
administrator is the real user. But for a Unix-like operating system, it is possible for two users to
login at a time and this capability of the OS makes it a multi-user operating system.
Multi-tasking vs. Single-tasking
When only a single program is allowed to run at a time, the system is grouped under a single-
tasking system. However, when the operating system allows the execution of multiple tasks at one
time, it is classified as a multi-tasking operating system. Multi-tasking can be of two types: pre-
emptive or co-operative. In pre-emptive multitasking, the operating system slices the CPU time
and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and
Linux support pre-emptive multitasking. Cooperative multitasking is achieved by relying on each
process to give time to the other processes in a defined manner. MS Windows prior to Windows
2000 used to support cooperative multitasking.
Distributed
A distributed operating system manages a group of independent computers and makes them appear
to be a single computer. The development of networked computers that could be linked and
communicate with each other gave rise to distributed computing. Distributed computations are
carried out on more than one machine. When computers in a group work in cooperation, they make
a distributed system.

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