Introduction and Types of Operating System.pptx

CHAPTER 1
Introduction to Operating System
SIT COE Yadrav-Ichalkaranji

Contents-
Concept of OS
Components of OS
Operations of OS
oProgram Management
oResource Management
oSecurity and Protection

Concept of OS
Operating System is essential part of any
computer system.
An OS is a software consisting programs and
data that run on computers.
 A program that acts as an intermediary between
a user of a computer and the computer
hardware.

Operating System

Concept of OS (Cont.)
Operating system goals:
 Execute user programs and make solving
problems easier
 Make the computer system convenient to use
 Use the computer hardware in an efficient
manner

Four Components of a Computer
System

Components of OS
 Computer system can be divided into four components-
 Hardware – Provides basic computing resources.
 CPU, memory, I/O devices
 Operating System – It is an interface between user of
computer and computer hardware
 Controls and coordinates use of hardware among
various applications and users
 Application Programs – define the ways in which the system
resources are used to solve the computing problems of the
users
 Word processors, compilers, web browsers, database
systems, video games SIT COE Yadrav-Ichalkaranji

Components of OS(Cont.)
 Computer system can be divided into four
components-
 Users –
 People, machines, other computers

Operations of OS
o Program Management-
- A program under execution is called as process.
- A program reside on the disk .On disk it dose require any resources.
- A program gets executed in main memory. So it should be transferred
from disk to memory.
- From the computation context point of view, a process is defined by CPU
state, memory contents and execution environment.
- If many process remain busy in completing I/O,CPU is allocated to only
one process at a given point of time.
- If multiple user are working on the system, OS switches the CPU from
one user process to other
- The process management activities involve-
1. To provide control access to shared resources like file,
memory, I/O, and CPU.
2. Creation, execution and deletion of user and system
processes.
3.Resume a process execution or cancel it.
4.Schedule of a process. SIT COE Yadrav-Ichalkaranji

Operations of OS(Cont.)
o Resource Management-
-There are many resources available in the system.eg-CPU, memory, file
storage space, I/O devices, files, printers, etc.
-OS acts as the manager of these resources. It decides which resource
should be given to which program, for how much time and after use it reclaims the
resource.
- Multiple users/applications can share the resources. The reasons of
sharing are:
1. The devices are expensive, so sharing saves the cost.
2.The data needs to be shared as well as needs to be
communicated.
o Security and Protection-
- Security is easy to deal with accidental misuse with compare to malicious
misuse. The protection mechanisms are basically designed for protection from
accidents.
- Security measures deal with threats to resources that come from outside a
computer system, while protection measures strictly restricted to manage the internal
resources of the system, i.e how we provide controlled access to programs and data
stored in a system.
-Protection refers to the mechanism for controlling the access of the

Views of OS-
 Operating system can be easily understood by
following points:
User View
System view

Views of OS-(Cont.)
 User View-
- The user's view of the computer varies according to the interface being
used.
- Most computer users sit in front of a PC, consisting of a monitor, keyboard,
mouse, and system unit. Such a system is designed for one user to monopolize its
resources.
- If the user is working on the single autonomous PC for his work, then
performance is mostly taken into consideration .OS is designed to give ease of use
and gaining performance.
-Some users sit at a terminal connected to a mainframe or minicomputer.
Other users are accessing the same computer through other terminals. These users
share resources and may exchange information. The OS is designed to maximize
resource utilization.
- Some computers have little or no user view.
For example, embedded computers in home devices and automobiles may have
numeric keypads and may turn indicator lights on or off to show status, but they and

Views of OS-(Cont.)
 System View-
From the computer point of view, the operating system is the
program most intimately involved with the hardware.
There are two different views-
* An Operating system is a resource allocator.
- Manages all resources.
- Decides between conflicting requites for efficient
and fair resource use.
* The operating system is control program
- Controls execution of programs to prevent errors
and improper use of computer.

Different Types of Operating System
OS are mainly divided into two types-
1. Single User OS-
In which only one user can take the advantages of the various
features embedded in it.
Ex-MS-DOS
2. Multi User OS-
In which multiple users can take the various advantage of the
features embedded in it.
Ex-Windows XP,Windows-7,LINUX,UNIX etc.
The different types of Operating System are-
a) Batch Operating System
b) Multiprogramming Operating System
c) Time Sharing Operating System
d) Multiprocessor Operating System
e) Distributed Operating System
f) Real Time Operating System

Different Types of Operating System
Cont..
 Batch Operating System
-This type of operating system does not
interact with the computer directly.
-There is an operator which takes
similar jobs having same requirement and
group them into batches.
- It is the responsibility of operator to
sort the jobs with similar needs.

Advantages and Disadvantages of
Batch Operating System-
 Advantages-
◦ It is very difficult to guess the time required by any job to
complete. Processors of the batch systems know how
long the job would be when it is in queue
◦ Multiple users can share the batch systems
◦ It is easy to manage large work repeatedly in batch
systems
 Disadvantages-
◦ Lack of interaction between the user and the job.
◦ CPU is often idle, because the speed of the mechanical
I/O devices is slower than the CPU.
◦ Difficult to provide the desired priority.

Multiprogramming Operating
System
-Multiprogramming is the ability to execute multiple
programs at the same time on single processor machine .
-One or more programs reside in the main
memory which are ready to execute.
-The CPU can execute only one instruction at a
time. if the currently executing process performs i/o
operation or waiting for i/o then the OS may interrupt that
process and gives the control to other process residing in
main memory.
- The main aim of Multiprogramming is to make

User Area
System Area

Multiprogramming Operating
System-
 Advantages-
◦ High and efficient CPU utilization.
◦ User feels that many programs are allotted
CPU almost simultaneously.
 Disadvantages-
◦ CPU scheduling is required.
◦ To accommodate many jobs in memory,
memory management is required.

Multitasking Operating System
- Multitasking is the logical extension of
Multiprogramming.
- A user to perform more than one computer
task at a time.

Multitasking Operating System-
 Advantages-
◦ High and efficient CPU utilization.
◦ User feels that many programs are allotted
CPU almost simultaneously.
 Disadvantages-
◦ CPU scheduling is required.
◦ To accommodate many jobs in memory,
memory management is required.

Time Shared Operating System
• Time-sharing is a technique which enables many
people, located at various terminals, to use a particular
computer system at the same time.
•Time-sharing or multitasking is a logical extension of
multiprogramming.
•Processor's time which is shared among multiple users
simultaneously is termed as time-sharing.
• If n users are present, then each user can get a time
quantum. When the user submits the command, the
response time is in few seconds at most.
• In time sharing system there is a large computer to
which a number of terminals are connected as shown in

Advantages and Disadvantages -
 Advantages
 Provides the advantage of quick response.
 Avoids duplication of software.
 Reduces CPU idle time.
 Disadvantages
 Problem of reliability.
 Question of security and integrity of user programs
and data.
 Problem of data communication.

Multiprocessor Operating
System-
 Multiprocessor are increasing in
importance nowadays.
 These systems have multiple processors
working in parallel that share the computer
clock, memory, bus, peripheral devices etc.
 These system is also called as parallel
system or tightly coupled system.
 The main advantage of multiprocessor
system is to get maximum work in shorter

System-

Multiprocessor Operating System-
Asymmetric Multiprocessors Symmetric Multiprocessors.
◦ In these types of systems,
each processor contains a
similar copy of the operating
system and they all
communicate with each
other. All the processors are
not in master - slave
relationship.
◦ It is called as master-slave
architecture.
◦ In asymmetric systems, each
processor is given a predefined
task. There is a master
processor that gives instruction
to all the other processors.
Asymmetric multiprocessor
system contains a master slave
relationship.

System-
Advantages and Disadvantages -
 Advantages
 More reliable Systems
 Enhanced Throughput
 More Economic Systems
 Disadvantages
 Increased Expense
 Complicated Operating System Required
 Large Main Memory Required

Real Time Operating System
 Real time system means that the system is subjected to real time, i.e.,
response should be guaranteed within a specified timing constraint or
system should meet the specified deadline.
 Example: flight control system, real time monitors, Satellite etc.
 There are two types of Real Time Operation System-
◦ Hard real time system –
This type of system can never miss its deadline. It guaranteeing that
critical task be completed within their period. Tardiness means how late
a real time system completes its task with respect to its deadline.
Example: Flight controller system.
◦ Soft real time system –
This type of system can miss its deadline .Real time task will get
priority over other task. The usefulness of result produced by a soft real
time system decreases gradually with increase in tardiness.
Example: Telephone switches, routers, microwave ovens,etc.

Real Time Operating System
 Application of Real Time Operating
System-
1. Satellite
2. Simulations
3. Industrial control
4. Military applications.
5. Flight Control System

Difference between Time Sharing
and Real Time System

Distributed Operating System
 Various autonomous interconnected computers communicate
each other using a shared communication network.
 Independent systems possess their own memory unit and CPU.
 Remote access is enabled within the devices connected in that
network.

Distributed Operating System
In Distributed Operating System applications would be divided into
two types-
Horizontal Distribution Vertical Distribution
 In horizontal distribution all the
computer system are at same level.
 They are equally capable of
handling any functionality.
 Ex-Airline reservation-
In that hundreds of computers in the
network are able to book or cancel
any reservation.
Work
at same
levels
 In vertical distribution there are
various levels of functionality.
These levels normally reflect the
levels of in an organization.
 Ex- Any Organizational company
Division
Zones
Branches

Distributed Operating System:
Advantages and Disadvantages of Distributed System
 Advantages
◦ Failure of one will not affect the other network communication, as all systems
are independent from each other
◦ Electronic mail increases the data exchange speed
◦ Since resources are being shared, computation is highly fast and durable
◦ Load on host computer reduces
◦ These systems are easily scalable as many systems can be easily added to
the network
 Disadvantages
◦ Failure of the main network will stop the entire communication
◦ To establish distributed systems the language which are used are not well
defined yet
◦ These types of systems are not readily available as they are very expensive.

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