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.
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
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
1. Production of error messages.
2. Maintenance of internal time clock and log system
usage for all users.
3. Provides easy communication between the
computer system and users.
4. Resource Allocator
6. Executes application software
7. Memory management
8. 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:-
• Desktop O/S:
• Designed to support a single user or a small
work group of users.
• Departmental O/S:
• Supports from a few dozen to a few hundred
8. CATEGORIES OF OPERATING SYSTEMS
• Enterprise O/S:
• Generally supports thousands of users and
• 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
• 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
1. Windows 3.1
• It is a transition windowing system between
MS-DOS and Windows95, Windows 98 and
• It is not actually an operating system, but a
GUI that operates with, and extends the
capabilities of MS-DOS
12. Desktop Operating System
1. 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
• It also offers plug-and-play capabilities by enabling
the operating system to recognize new hardware
and install the necessary software (device drivers)
13. Desktop Operating System
1. Windows 98
• Offered minor refinements, bug fixes, and
enhancements to windows 95.
3. Windows NT
• An operating system for high-end desktops and
• It provides the same GUI as Windows 95, 98, and
• Has more powerful multitasking, and memory
• It is popular in networked systems in business
14. Desktop Operating System
1. 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.
6. Windows CE (Compact Edition)
• Is a 32-bit operating system designed for hand-held
PCs, and wireless communication devices.
15. Desktop Operating System
1. IBM’s OS/2 Operating System
• A 32-bit operating system that supports multitasking,
and supports networked applications.
• Macintosh Operating System
• For Apple Macintosh microcomputers.
• Is a 32-bit operating system that features
multitasking and powerful graphics capabilities.
16. Desktop Operating System
• Provides many sophisticated desktop
features, including multiprocessing and
• Is valuable to business organizations because
it can be used on many different sizes of
computers ( different hardware: non Intel and
• Was popularized by Sun Microsystems.
17. Desktop Operating System
• A powerful version of Unix .
• Completely free of charge.
• It offers multitasking, virtual memory management, and TCP/
• 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
1. Java Operating System
• Is designed for hand-held products and
• 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
20. Departmental Server Operating
The major departmental server operating systems
• Windows NT server
• IBM’s OS/2 Warp Server
• Novell NetWare
• IBM’s OS/400
21. Departmental Server Operating
Although some of these are also desktop OS, all can
serve as departmental server OS because of their:-
• Strong scalability
• Fault tolerance
• TCP/IP networking
• Network management
22. Enterprise Operating Systems
23. Enterprise Operating
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
Enterprise operating systems support:
• Secure electronic commerce
• Multiple concurrent users
• Large (terabyte) databases
• Millions of transactions per day.
25. Types of O/S
• Time sharing
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
• For example, the user may be running one program
and simultaneously listening to a music file.
27. Multiprogramming Operating
• 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
• 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
• 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
• 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.