What is an Operating System, Simple Batch Systems, Multiprogrammed Batches systems, Time-Sharing Systems, Personal-computer systems, Parallel systems, Distributed Systems, Real-Time Systems.

1. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Affiliated to Institution of G.G.S.IP.U, Delhi
OPERATING SYSTEM
PAPER CODE - BCA 301
Charanpreet Kaur
Assistant Professor

2. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• To introduce an operation System and
describe the functionalities of
Operating System.
• To Understand the services provided
by an operating system.
OBJECTIVES OF THE SUBJECT

3. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Introduction: What is an Operating System, Simple
Batch Systems, Multiprogrammed Batches systems,
Time-Sharing Systems, Personal-computer systems,
Parallel systems, Distributed Systems, Real-Time
Systems.
• Memory Management: Background, Logical versus
Physical Address space, swapping, Contiguous
allocation, Paging, Segmentation.
• Virtual Memory: Demand Paging, Page Replacement,
Page-replacement Algorithms, Performance of Demand
Paging, Allocation of Frames, Thrashing, Other
Considerations.
OVERVIEW OF THE SYLLABUS
1st Unit

4. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Processes: Process Concept, Process Scheduling,
Operation on Processes.
• CPU Scheduling: Basic Concepts, Scheduling
Criteria, Scheduling Algorithms, Multiple-
Processor Scheduling.
• Process Synchronization: Background, The
Critical-Section Problem, Synchronization
Hardware, Semaphores, Classical Problems of
Synchronization.
2nd Unit

5. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Deadlocks: System Model, Deadlock
Characterization, Methods for Handling Deadlocks,
Deadlock Prevention, Deadlock Avoidance,
Deadlock Detection, Recovery from Deadlock
• Device Management: Techniques for Device
Management, Dedicated Devices, Shared Devices,
Virtual Devices; Input or Output Devices, Storage
Devices, Buffering, Secondary-Storage Structure,
Disk Structure, Disk Scheduling, Disk Management,
Swap-Space Management, Disk Reliability
3rd Unit

6. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Information Management: Introduction, A
Simple File System, General Model of a File
System, Types of File System File-System
Interface: File Concept, Access Methods,
Directory Structure, Protection: Goals of
protection, Domain of protection, Access rights,
Consistency Semantics Security: Authentication,
Program threats, System threats, Encryption.
4th Unit

7. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
INTRODUCTION
What is an Operating System?
 A program that acts as an intermediary between
a user of a computer and the computer
hardware.
 It provide a pleasant and effective interface
between the user and the hardware.
 It uses the computer hardware in an efficient
manner.

8. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Operating System is a program that controls
execution of application programs.
Hardware
O.S
System and application
programs
USERS
Abstract View of
Computer system

9. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Hardware:- It includes CPU, the memory, input
output(I/O) devices and provides the basic computing
resources for the system.
• Application Programs:- It includes Word Processors,
Spreadsheets, compilers, web browsers and define the
ways in which these resources are used to solve users
computing problems.
• Operating System:- coordinates its use among the
various application programs for the various users.
• Users:- They are the end users who interact with the
system.
Abstract View Of an Operating System

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

11. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
An operating system performs basic tasks such as:
 controlling and allocating memory
 process management
 controlling input and output devices
 facilitating networking
 managing file systems
 command interpretation
WHAT DOES AN OPERATING SYSTEM DO?

12. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• It is the control module of an operating
system.
• It is the one which loads first and remains in
the main memory.
• All the critical functions are implemented by
the kernel.
• It is that part of an OS which directly interacts
with the hardware.
KERNEL OF AN OPERATING SYSTEM

13. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• It provides the mechanism for creation and
deletion of processes.
• It provides process scheduling, memory
management, I/O management.
• It provides mechanism for synchronization of
processes.
• It provides mechanism for IPC (Inter Process
Communication)
Functions of Kernel

14. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Some Examples of Operating System

15. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
1. BATCH PROCESSING SYSTEMS
• In Batch processing same type of jobs batch (BATCH- a
set of jobs with similar needs) together and execute at a
time.
• The OS was simple, its major task was to transfer control
from one job to the next.
• The job was submitted to the computer operator in form
of punch cards. At some later time the output appeared.
EVOLUTION OF OPERATING SYSTEM

16. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• For example:- imagine that the operator received
one FORTRAN, one PASCAL and another FORTRAN
program. If he runs in the same order, he would
have to set up first the FORTRAN environment,
then set up the PASCAL environment and finally
again load the settings for running the FORTRAN
program.
• However, if he runs the two FORTRAN programs as
a batch, he needs to set up only once the FORTRAN
environment, thus saving the operator’s time.
BATCH PROCESSING SYSTEMS

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

18. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Multiprogramming is a technique to execute number
of programs simultaneously by a single processor.
• In Multiprogramming, number of processes reside in
main memory at a time.
• The OS picks and begins to executes one of the jobs
in the main memory.
• If any I/O wait happened in a process, then CPU
switches from that job to another job.
• Hence CPU in not idle at any time.
2. MULTIPROGRAMMING SYSTEMS

19. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Advantages:-
 Efficient memory utilization
 Throughput increases
 CPU is never idle, so performance increases.
 Supports multiple simultaneous interactive
users.
MULTIPROGRAMMING SYSTEMS

20. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Multiprocessing is the use of two or more central
processing units (CPUs) within a single computer
system.
• The term refers to the ability of a system to
support more than one processor and the ability
to allocate tasks between them.
• A multiprocessor is a computer system having
two or more processing units (multiple
processors) each sharing main memory and
peripherals, in order to simultaneously process
programs.
3. MULTIPROCESSING SYSTEMS

21. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
MULTIPROCESSING OPERATING SYSTEM

22. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Types of Multiprocessing Systems:-
1. Symmetric Multiprocessor System
2. Asymmetric Multiprocessor System
Symmetric Multiprocessor System
All the CPU’s are essentially identical and perform identical
functions.
CPU 1 CPU 2
CPU 3 CPU 4

23. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Asymmetric Multiprocessor System
Different processors do different tasks; one may
be a Master and it may control other CPU’s.
(MASTER)
CPU 3
CPU 1
CPU 3CPU 2

24. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Time sharing, or multitasking, is a logical extension of
multiprogramming.
• Multiple jobs are executed by switching the CPU between
them.
• In this, the CPU time is shared by different processes, so
it is called as “Time sharing Systems”.
• Time slice is defined by the OS, for sharing CPU time
between processes.
• A time shared system allows many users to share the
computer simultaneously.
4. TIME SHARING SYSTEMS

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

26. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• A distributed environment refers to the collection
of autonomous systems, capable of
communicating and cooperating with each other
through the network, are connected to each
other through LAN/WAN.
• A distributed OS is the one that looks to its users
like an ordinary centralized OS but runs on
multiple independent CPU’s.
• It allows users to access remote resources in the
same manner as they do with local resources.
5. DISTRIBUTED SYSTEMS

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

28. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• If there are no. of sites connected, then it
allows resource sharing in a distributed
system.
• There is computation speed up.
• Reliability is also better.
• Communication is also easy is these systems.
Advantages

29. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• A real-time operating system (RTOS) is an operating
system (OS) intended to serve real-time application
requests. It must be able to process data as it comes in,
typically without buffering delays.
• A real time OS has a well defined and fixed time
constraint.
• A primary objective of RTOS is to provide quick event
response times and thus meet the scheduling
deadlines.
• For example:- Air traffic control systems, medical
imaging systems, industrial control systems, etc.
4. REAL TIME SYSTEMS

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

31. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• A system consisting of more than one processor
and sharing resources like bus, clock, memory,
I/O devices is a parallel system.
• A single CPU may be slow therefore, many CPU’s
may parallely execute a single given problem.
• These systems reduce the time required for job
execution and increase the CPU throughput.
5. PARALLEL SYSTEMS

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