1. An operating system acts as an interface between the user and computer hardware, managing resources and allowing users to execute programs. 2. Key components of a computer system include hardware, operating system, application programs, and users. 3. The main functions of an operating system include memory management, process management, device management, information management, protection, and error handling.

1. OPERATING SYSTEMS
V.V.SUBRAHMANYAM
ASSOCIATE
PROFESSOR
SOCIS, IGNOU

2. COMPONENTS OF A COMPUTER
SYSTEM
The computer system is basically
divided into 4 components:
1. Hardware
2. Operating System
3. Application programs
4. Users

3. Users
Application Programs
Operating system
Computer Hardware
ABSTRACT OVERVIEW

4. HARDWARE
This provides the Basic system
resources.

5. SYSTEM SOFTWARE
• Refers to the Operating system and all
utility programs that manage computer
resources at a low level.
• It includes compilers, loaders, linkers
and debuggers.

6. APPLICATION PROGRAMS
A program or group of programs
designed for end users.
Examples: Word processing, Graphics,
Spreadsheets, Databases,
Games.

7. GOALS OF
AN OPERATING SYSTEM
• To make the computer system
convenient to use.
• To use the computer hardware in an
efficient manner.

8. PURPOSE OF AN OPERATING
SYSTEM
• The purpose of an operating system
is to provide an environment in which
a user may execute programs.

9. WHAT IS AN OPERATING
SYSTEM?
• An Operating System is an interface
between user and hardware of a
computer system.

10. WHAT IS AN OPERATING
SYSTEM?
• An Operating System is a system
software which may be viewed as an
organized collection of software
consisting of procedures for operating
a computer and providing an
environment for execution of programs.

11. OTHER DEFINITIONS
• An Operating System is a control
program.
• An Operating System is similar to a
Government.
• An Operating System can be defined
as a Resource Manager.

12. OTHER DEFINITIONS
• An Operating System is the layer between
the H/W and the S/W
• An Operating System is a virtual
computer manager
• Operating System is the first program run
on a computer when the computer boots
up

13. USER INTERFACE
A set of commands or menus through
which user communicates with the
program.

14. TYPES OF INTERFACES
• Command driven
• Menu driven
• Graphical user interface(GUI)

15. WAYS TO INTERACT WITH
OPERATING SYSTEM
• OPERATING SYSTEM CALLS
• OPERATING SYSTEM COMMANDS

16. SYSTEM CALLS
• Invokes services of the operating system
by means of run-time system calls.
• These are usually embedded in, and
activated during execution of programs.

17. SYSTEM COMMANDS
• These are used to obtain services of the
o/s by means of commands, typed at the
terminal or embedded in a batch job.

18. SYSTEM CALLS
System Calls provide the interface to a
running program and the O/S.
OPERATING SYSTEM COMMANDS
Users may interact with the O/S directly
by means of O/S commands.

19. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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20. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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The o/s keeps track of
the memory, what parts are
in use and by whom.

21. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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The o/s keeps track ofThe o/s keeps track of
processors and the statusprocessors and the status
of processes. It decidesof processes. It decides
who will have a chance towho will have a chance to
use the processor.use the processor.

22. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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The o/s keeps track of the devices,
channels, control units and
decides what is an efficient
way to allocate the device.

23. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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O/S keeps track of the information,
its location, use, status etc.
and decides who gets use
of the resources,
enforce protection requirements.

24. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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An o/s is to protect the userAn o/s is to protect the user
from unauthorized accessfrom unauthorized access
of his files or data.of his files or data.
And also it should protectAnd also it should protect
itself from usersitself from users

25. FUNCTIONS OF
OPERATING SYSTEM
Memory management
Process management
Device management
Information management
Protection
Error Handling
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An o/s must respond to
errors by taking the
appropriate actions.

26. TYPES OF OPERATING SYSTEMS
• Batch Operating Systems
• Multiprogramming Operating Systems
• Distributed Operating systems
• Network Operating systems

27. Batch Operating Systems
• Batch processing generally requires the
program, data and appropriate system
commands to be submitted together in the
form of a job.
• Batch O/s usually allow little or no
interaction between users and executing
programs

28. Contd…
• Scheduling in batch systems is very
simple and are processed in the order of
submission
• Memory management in batch systems is
also very simple.

29. Contd…
• Memory is divided into 2 areas:
• Permanently occupied by the resident
portion of the o/s
• Is used to load transient programs for
execution
• Examples include payroll, forecasting,
statistical analysis and large scientific
number crunching programs.

30. MULTIPROGRAMMING
• Multiprogramming is essentially
multiplexing of system resources
such as processor, memory, and
I/O devices among a number of
active programs.

31. Contd…
• Multiprogramming is used as a
technique to enhance the throughput
efficiency.
• Overlapping interleaving computing
of different jobs.
• More than one job is “ready” at the
same time.

32. Multiprogramming Operating Systems
• These are characterized by a multitude of
simultaneously active programs that are
competing for system resources, such as
processor, memory and I/O devices.
• It monitors the state of al active programs
and system resources.

33. Different types of
Multiprogramming Operating System
• Multitasking operating system
• Multiprocessing operating system
• Multiuser operating system

34. Multitasking Operating systems
• A multitasking o/s is distinguished by its
ability to support concurrent execution of
two or more active processes.
• It is often coupled with h/w and s/w
support for memory protection in order to
prevent erroneous processes from
corrupting address spaces and behavior
of other resident processes.

35. Multiprocessing Operating Systems
• These operating systems manage the
operation of computer systems that
incorporate multiple processors.
• Multiprocessor operating systems are
multitasking systems by definition
because they support simultaneous
execution of multiple processes on
different processors.

36. Multiuser Operating Systems
• Multiprogramming o/s usually support
multiple users and are called as multiuser
systems.
• These provide facilities for maintenance of
individual user environments, require user
authentication for security and protection,
and provide per-user resource usage
accounting.

37. “In general, Multiprogramming implies
multitasking , but multitasking does not
imply multiprogramming”

38. Multiaccess Operating Systems
• These allow simultaneous access to a
computer system through two or more
terminals.
• In general, multiaccess operation does
not necessarily imply multiprogramming.
Example: Airline ticket reservation system

39. Distributed operating systems
• It governs the operation of a distributed
computer system and provides a virtual
machine abstraction to its users.
• Key objective of a distributed operating
systems is transparency.

40. Contd…
• It facilitates access to remote resources,
communication with remote processes,
and distribution of computations

41. NETWORK OPERATING SYSTEM
• The term network operating system,
however, is generally reserved for s/w
that enhances a basic o/s by adding
networking features.
Examples:NOS's for DOS and Windows
systems include Novell Netware,
Artisoft's LANtastic, Microsoft LAN
Manager, and Windows NT.

42. Time sharing systems
• It is a popular representative of
multiprogrammed, multiuser systems.
• Giving the illusion to each user of having
a mcahine to oneself.
• These provide equitable sharing of
common resources.

43. Contd…
• Good terminal response time
• Most time sharing systems use time
slicing or round robin (RR) scheduling
• Applications include large CAD and text
processing systems.

44. Real-time systems
• These are mostly concerned with
responsive handling of external events
generated by the controlled system.
• To provide quick event response times,
and thus meet the scheduling deadlines.
• Applications include Industrial control,
telephone switching equipment, flight
control and real time simulation.

45. Process
• Process or Task is a dynamic concept
that refers to a program in execution.
• It is a smallest unit of work individually
schedulable by an operating system.

46. Processes and attributes
• Each process possesses certain attributes
that assist the O/s in managing it.
• The attributes includes current state,
scheduling priority, access rights and
other information.

47. Contd…
• Each multiprogramming o/s keeps track of
all active processes and allocates system
resources to them according to policies
devised to meet design performance
objectives.

48. Implicit tasking
• The processes are defined by the system.
• This is commonly encountered in general
purpose multiprogramming systems

49. Explicit tasking
• The programmers explicitly define each
process and some of the attributes.
• This is user in situations where high
performance of system activities is
desired.
• This result in faster execution of an
application.

50. Process Relationship
• There are 2 fundamental relations among
concurrent processes:
• Competition
• Cooperation

51. Process states
• Dormant
• Ready
• Running
• Suspended

52. Dormant state
• All process templates awaiting activation,
as well as programs not yet submitted to
the o/s, may be treated as dormant.

53. Ready state
• A ready process possesses all resources
needed for its execution, except the
processor.
• All ready processes are waiting to have
the processor allocated to them by the o/s

54. Running state
• A running process possesses all
resources for its execution, including the
processor.
• The running process executes its
sequence of machine instructions and
may call on the o/s to perform services
such as I/O operation or synchronization
on its behalf.

55. Suspended state
• A Suspended process lacks some
resources other than the processor, such
as a synchronization signal.

56. Process state-transition diagram
Running
Dormant
Ready
Suspended
Event occurs
Awaits eventTerminates
Created
Scheduled Preempted

57. Scheduler
• It is an operating system module which
selects one ready process for execution
whenever the O/S has control of the
processor and is about to transfer it a user
process.

58. Process control Block ( PCB)
• The O/S groups all information that needs
about a particular process into a data
structure called a process descriptor or
a process control block (PCB).

59. Contd…
• Process name (ID)
• Priority
• State
• H/W state (Processor registers and flags)
• Scheduling information and usage statistics
• Memory management information
• I/O status
• File management information
• Accounting information

60. Process Switch
• A transition between two memory resident
processes in a multiprogramming system
is called a process switch or task switch.