1
SWE3001 – Operating Systems
Slot: B1
Faculty: Prof. M. Premalatha, SCOPE, VIT Chennai
Mob: 9884326554
E-Mail: 50289@vitstudent.ac.in; premalatha.m@vit.ac.in
2
Modules
Introduction
Process
Process Synchronization
CPU Scheduling and Deadlocks
Memory Management
Virtual Memory
Mass-Storage Structure
Contemporary Issues
3
Book
A.Silberschatz, P.B. Galvin & G. Gagne, Operating system concepts,
Ninth Edition, John Wiley, 2013
Link for Silberschatz’s Contents
https://www.os-book.com/OS10/slide-dir/index.html
4
Module 1
Computer System Organization - Computer System Architecture
Dr. Abdul Quadir Md, SCOPE
VIT Chennai
5
Computer System Organization
What is an Operating System? 6
An arbitrator between a PC user and the
hardware.
Make the hardware appropriate to use.
Manages system resources.
Use the hardware in an effective way.
7
Computer System Structure
Divided into four components:
Hardware
Operating system
Application programs
Users
8
System Diagram
user user user
1 2 ... n
compiler text editor ls
system and application programs
operating system
hardware
What OS do? 9
Depends upon view point
Users want : convenience, ease of use , good
performance
Don’t care about resource utilization
Users of dedicate systems have dedicated resources
Some computers have little or no user interface,(eg:
embedded computers and automobiles)
Operating System Definition 10
OS is a resource allocator
Manages all resources
OS is a control program
Manages execution of programs
Operating System Definition (Cont.) 11
No generally recognized definition
The one program running at all times on the
computer is the kernel
Everything else is either
a system program ( or)
an application program.
Computer Startup 12
Bootstrap program is loaded at power-up or
reboot
Typically stored in ROM or EPROM - known as
firmware
Initializes all aspects of system
Loads operating system kernel and starts
execution
13
Computer System Organization
Computer System Organization 14
Many devices connected
through common bus providing
access to shared memory
Concurrent execution of CPUs
and devices competing for
memory cycles
Computer-System Operation 15
I/O devices and the CPU can execute concurrently
Each device controller is in charge of a particular
device type
Each device controller has a local buffer
CPU moves data from/to main memory to/from
local buffers
I/O is from the device to local buffer of controller
Device controller informs CPU that it has finished
its operation by causing an interrupt
Common Functions of Interrupts 16
Interrupt – sudden stoppage in the execution of a
program
Interrupt service routine
Interrupt architecture must save the address of the
interrupted instruction
A trap or exception is a software-generated interrupt
caused either by an error or a user request
An operating system is interrupt driven
Storage Structure
17
18
Classification of Computer Memory
19
Storage-Device Hierarchy
20
Computer System Architecture
Computer-System Architecture 21
Most systems use a single general-purpose processor
Multiprocessors systems also known as parallel systems, tightly-coupled
systems
Advantages include:
Increased throughput
Economy of scale
Increased reliability
2 types:
Asymmetric Multiprocessing – each processor is assigned a specie task.
Symmetric Multiprocessing – each processor performs all tasks
Symmetric Multiprocessing 22
Asymmetric vs symmetric Multiprocessing
23
24
Types of Systems
Single Tasking System
Multi-User Operating System
Batch Operating System
Time-Sharing Operating Systems
Distributed Operating System
Network Operating System
Multitasking System
Real-time system
25
Single Tasking System
Only one program can perform at a time
Simple to implement
only one process attempting to use resources
Few security risks
Poor utilization of the CPU and other resources
Example: MS-DOS
Multi-User Operating System 26
Many multiple users that are on different
computers to access a single system's OS
resources simultaneously
The OS shares resources between users,
Some examples of a multi-user OS are Unix,
Virtual Memory System (VMS) and
mainframe OS.
27
Batch Operating System
It does not interact with the computer directly.
Takes similar jobs having same requirement
Group them into batches.
To sort the jobs with similar needs.
Time-Sharing Operating Systems
28
Each task is given some time to execute
Each user gets time of CPU as they use single system
Also known as Multitasking Systems
The time that each task gets to execute is called
quantum
After this time interval is over OS switches over to next
task
Advantages of Time-Sharing OS:
Each task gets an equal opportunity
Less chances of duplication of software
CPU idle time can be reduced
29
Distributed Operating System:
Various autonomous interconnected computers
communicate each other using a shared communication
network.
Independent systems possess their own memory unit and
CPU
These are referred as loosely coupled systems or
distributed systems
These system’s processors differ in size and function.
Network Operating System
30
These systems run on a server
These type of operating systems allow
shared access of files, etc
All the users are well aware of the
underlying configuration, of all other users
within the network, their individual
connections etc
Known as tightly coupled systems.
31
Multitasking System
Very complex
Serious security issues
how to protect one program from another sharing the
same memory
Much higher utilization of system resources
Example: Unix, Windows NT
32
Real-time system
Hard real-time system:
Time-critical deadlines that must be met
Else a catastrophic system failure can occur.
Absolutely, positively, first time every time
Examples:
– air traffic control
– vehicle subsystems control
– Nuclear power plant control
33
Real-time system
Soft real-time system:
Undesirable, but not catastrophic, if deadlines are occasionally
missed
Also known as “best effort” systems
Examples:
– multimedia transmission and reception
– networking, telecom (cellular) networks
– web sites and services
– computer games
34
ns ?
e st io
y Q u
A n
35
References
Silberschatz, Gagne, Galvin: Operating System Concepts, 6th Edition
36
You!
hank
T
