The document discusses different types of operating systems including desktop, departmental, and enterprise operating systems. It describes the key functions of an operating system as acting as an intermediary between the user and computer hardware to provide an efficient environment to run programs. Examples are given of different categories of operating systems based on the number of users supported and level of sophistication, including desktop systems for single users, departmental systems for dozens to hundreds of users, and enterprise systems for thousands of users.

1. Operating System

2. Operating System
• A special system software that acts as an intermediary
between a user of a computer and the computer hardware.
• Provides an environment in which the user can execute
programs/applications in a convenient and efficient manner.
User
Operating System
Hardware
Examples of OS: Windows, MS-DOS, Linux, Unix

3. Operating System.
Thus the main goals for an Operating system are:
• Make computer convenient to use (hides Hardware details)
• Utilize resources in efficient manner

4. Operating System
User
Application Software
Operating System
Computer hardware

5. Functions of O/S
1. Process Management
2. Memory Management
3. Deadlock Handling
4. File Management
5. I/O Management
6. Protection & Security
7. Job scheduling
8. Interpretation of commands and instructions.
9. Co-ordination of compilers and, assembler,
programs and other s/w of computer system.

6. Functions of O/S
10. Production of error messages.
11. Maintenance of internal time clock and log system
usage for all users.
12. Provides easy communication between the
computer system and users.
13. Resource Allocator
14. Intermediary
15. Executes application software
16. Memory management
17. CPU Scheduling

7. CATEGORIES OF OPERATING
SYSTEMS
Operating systems can be categorised by the
number of users they support as well as by their
level of sophistication.
Three categories are broadly recognized:-
1. Desktop O/S:
• Designed to support a single user or a small
work group of users.
2. Departmental O/S:
• Supports from a few dozen to a few hundred
users.

8. CATEGORIES OF OPERATING
SYSTEMS
3. Enterprise O/S:
• Generally supports thousands of users and
transactions simultaneously.
• Offers the greatest functionality, followed by
departmental operating systems, and then
desktop operating systems.
• The user interface is the least sophisticated on
enterprise operating systems.

9. Desktop Operating System

10. Desktop Operating System
• Supports a single user or a small group of users.
• Some examples of the operating systems in this
category are:-
1. MS-DOS:
• One of the original operating systems for the IBM
PC and its clones.
• A non-graphical, line oriented, command-driven
operating system, with a relatively simple interface
but not a friendly user interface.
• It was not capable of multitasking.
• It has now been almost totally replaced by GUI
products such as Windows 95, Windows 98,
Windows 2000 and Windows XP.

11. Desktop Operating System
2. Windows 3.1
• It is a transition windowing system between
MS-DOS and Windows95, Windows 98 and
Windows 2000.
• It is not actually an operating system, but a
GUI that operates with, and extends the
capabilities of MS-DOS

12. Desktop Operating System
3. Windows 95
• The first of a series of products in the Windows
operating systems that provides a GUI by using
icons to provide instant access to common tasks.
• It is a 32-bit operating system that features
multitasking, networking, and Internet integration
capabilities.
• It also offers plug-and-play capabilities by enabling
the operating system to recognize new hardware
and install the necessary software (device drivers)
automatically.

13. Desktop Operating System
4. Windows 98
• Offered minor refinements, bug fixes, and
enhancements to windows 95.
5. Windows NT
• An operating system for high-end desktops and
workstations.
• It provides the same GUI as Windows 95, 98, and
2000.
• Has more powerful multitasking, and memory
management capabilities.
• It is popular in networked systems in business
organizations.

14. Desktop Operating System
6. Windows 2000
• Microsoft changed the name of the upgrade of
Windows NT 5.0 to Windows 2000.
• This operating system has added security features.
• Runs on multiprocessor computers.
• Offers added Internet and Intranet functionality.
7. Windows CE (Compact Edition)
• Is a 32-bit operating system designed for hand-held
PCs, and wireless communication devices.

15. Desktop Operating System
8. IBM’s OS/2 Operating System
• A 32-bit operating system that supports multitasking,
and supports networked applications.
9. Macintosh Operating System
• For Apple Macintosh microcomputers.
• Is a 32-bit operating system that features
multitasking and powerful graphics capabilities.

16. Desktop Operating System
10.Unix
• Provides many sophisticated desktop
features, including multiprocessing and
multitasking techniques.
• Is valuable to business organizations because
it can be used on many different sizes of
computers ( different hardware: non Intel and
Intel processors).
• Was popularized by Sun Microsystems.

17. Desktop Operating System
11. Linux
• A powerful version of Unix .
• Completely free of charge.
• It offers multitasking, virtual memory management, and
TCP/IP networking.
• Originally written by Linus Tovalds at the University of
Helsinki in 1991.
• He then released the source code to the world.
• Like Unix, it runs on multiple hardware platforms.
• Is becoming widely used by Internet service providers.
• The clearinghouse for Linux information on the Internet may
be found at www.linuxhq.com

18. Desktop Operating System
12.Java Operating System
• Is designed for hand-held products and
network computers.
• Sun’s java operating system executes
programs written in Java language without the
need for a traditional operating system.
• It is designed for Internet and Intranet
applications and embedded devices.

19. Departmental Server
Operating
Systems

20. Departmental Server Operating
Systems
The major departmental server operating systems
include:-
• Unix
• Windows NT server
• IBM’s OS/2 Warp Server
• Novell NetWare
• IBM’s OS/400

21. Departmental Server Operating
Systems
Although some of these are also desktop OS, all can
serve as departmental server OS because of their:-
• Strong scalability
• Reliability
• Backup
• Security26
• Fault tolerance
• Multitasking
• Multiprocessing
• TCP/IP networking
• Network management

22. Enterprise Operating Systems

23. Enterprise Operating
Systems
The major enterprise operating systems include:
• IBM’s MVS (Multiple Virtual Storage)
• IBM’s VM (Virtual Machine)
• IBM’s VSE (Virtual Storage Extended)
• Digital Open VMS (Virtual Machine System)

24. Enterprise Operating
Systems
Enterprise operating systems support:
• Secure electronic commerce
• Multiple concurrent users
• Large (terabyte) databases
• Millions of transactions per day.

25. Types of O/S
• Multitasking
• Multiprogramming
• Time sharing
• Multiprocessing

26. MULTITASKING O/S
• Executing more than one task concurrently.
• Execution of two or more tasks/programs by one
user concurrently on the same computer with one
central processor.
• For example, the user may be running one program
and simultaneously listening to a music file.

27. Multiprogramming Operating
System
• Refers to concurrent execution of different users’
programs on a machine with a single processor.
• It is the execution of two or more programs
concurrently on a multi-user operating system.
• The processor spends a certain amount of time
executing each user’s program. As the processor
works much faster, it seems as though all the
programs are being run at the same time.

28. Time Sharing Operating
System
• Round-Robin processing of programs for several
users.
• A single computer processes the tasks of several
users at different locations based on the concept of
time slicing between the users.

29. Multiprocessing Operating
System
• Simultaneous processing of two or more programs by
multiple computers or processors linked together to
perform work simultaneously.
• This can involve processing of instructions from
different programs or different instructions within the
same program simultaneously.
• Implemented using concepts of parallel processing.

30. Real Time Operating System
• an operating system that guarantees a certain capability
within a specified time constraint
• Such applications include embedded systems and scientific
research equipment.
• Provides facilities which, if used properly, guarantee
deadlines can be met.
• Uses specialized scheduling algorithms in order to provide the
real-time developer with the tools necessary to produce
deterministic behavior in the final system.
• An RTOS is valued more for how quickly and/or predictably it
can respond to a particular event
• An early example of a large-scale real-time operating system
was the so-called "control program" developed by American
Airlines and IBM for the Sabre Airline Reservations System.