Department of computer application- Introduction to Information Technology- Operating system Operating System Operating System Objectives Layers of Computer Systems Services Provided by the Operating System Functions of Operating Systems Types of Operating Systems Enhancing an OS A program that controls the execution of application programs An interface between applications and hardware Layers of Computer System Services Provided by the Operating System Program development Editors and debuggers Program execution Access to I/O devices Controlled access to files System access

1. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Affiliated G.G.S.IP.U, Delhi
Introduction to Information Technology
Topic: Operating System
Course: B.Com (Honours)
Paper Code: 888107
Keywords: Operating System, Functions of Operating System

2. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Operating System Basics
• Operating System
• Operating System Objectives
• Layers of Computer Systems
• Services Provided by the Operating System
• Functions of Operating Systems
• Types of Operating Systems
• Enhancing an OS

3. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Operating System
• A program that controls the execution of
application programs
• An interface between applications and hardware

4. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Operating System Objectives
• Convenience
– Makes the computer more convenient to use
• Efficiency
– Allows computer system resources to be used in an
efficient manner
• Ability to evolve
– Permit effective development, testing, and
introduction of new system functions without
interfering with service

5. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Layers of Computer System

6. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Services Provided by the Operating
System
• Program development
– Editors and debuggers
• Program execution
• Access to I/O devices
• Controlled access to files
• System access

7. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Services Provided by the Operating
System
• Error detection and response
– internal and external hardware errors
• memory error
• device failure
– software errors
• arithmetic overflow
• access forbidden memory locations
– operating system cannot grant request of application

8. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Services Provided by the Operating
System
• Accounting
– collect statistics
– monitor performance
– used to anticipate future enhancements
– used for billing users

9. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Functions of Operating Systems
• Provide a user interface
• Run programs
• Manage hardware devices
• Organized file storage

10. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Providing a User Interface
• User interface
– How a user interacts with a computer
– Require different skill sets

11. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Providing a User Interface
• Graphical user interface (GUI)
– Most common interface
• Windows, OS X, Gnome, KDE
– Uses a mouse to control objects
– Uses a desktop metaphor
– Shortcuts open programs or documents
– Open documents have additional objects
– Task switching
– Dialog boxes allow directed input

12. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Graphical User Interface

13. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Providing a User Interface
• Command line interfaces
– Older interface
• DOS, Linux, UNIX
– User types commands at a prompt
– User must remember all commands
– Included in all GUIs

14. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Command Line Interface

15. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Running Programs
• Many different applications supported
• System call
– Provides consistent access to OS features
• Share information between programs
– Copy and paste
– Object Linking and Embedding

16. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Managing Hardware
• Programs need to access hardware
• Interrupts
– CPU is stopped
– Hardware device is accessed
• Device drivers control the hardware

17. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Organizing Files and Folders
• Organized storage
• Long file names
• Folders can be created and nested
• All storage devices work consistently

18. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Types of Operating Systems
• Real-time operating system
– Very fast small OS
– Built into a device
– Respond quickly to user input
– MP3 players, Medical devices

19. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Types of Operating Systems
• Single user/Single tasking OS
– One user works on the system
– Performs one task at a time
– MS-DOS and Palm OS
– Take up little space on disk
– Run on inexpensive computers

20. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Single Tasking
• Operating System cannot be able to take control back from
the running process/task/application
• In case if a process call an I/O Instruction then Processor
must wait for I/O instruction to complete before preceding

21. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Types of Operating Systems
• Single user/Multitasking OS
– User performs many tasks at once
– Most common form of OS
– Windows XP and OS X
– Require expensive computers
– Tend to be complex

22. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Multitasking
• Operating System can take control back from the running process and
can give it to other.
• When one job needs to wait for I/O, the processor can switch to the
other job

23. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Types of Operating Systems
• Multi user/Multitasking OS
– Many users connect to one computer
– Each user has a unique session
– UNIX, Linux, and VMS
– Maintenance can be easy
– Requires a powerful computer

24. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Multi user/Multi tasking OS

25. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Enhancing an OS
• Utilities
– Provide services not included with OS
– Goes beyond the four functions
– Firewall, anti-virus and compression
– Prices vary

26. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Enhancing an OS
• Backup software
– Archives files onto removable media
– Ensures data integrity
– Most OS include a backup package
– Many third party packages exist

27. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Backup Software

28. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Enhancing an OS
• Anti-virus software
– Crucial utility
– Finds, blocks and removes viruses
– Must be updated regularly
– McAfee and Norton Anti-Virus

29. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Enhancing an OS
• Firewall
– Crucial utility
– Protects your computer from intruders
– Makes computer invisible to hackers
– Zone Labs is a home firewall
– Cisco sells hardware firewalls

30. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Enhancing an OS
• Intrusion detection
– Often part of a firewall package
– Announces attempts to breach security
– Snort is a Linux based package

31. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Enhancing an OS
• Screen savers
– Crucial utility for command line systems
• Prevents burn in
– Merely fun for GUI systems
– Screen saver decorates idle screens