Lect 01 02 Introduction

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Welcome to

OPERATING SYSTEMS

(CS C372 & IS C362)

LECTURE 1: INTRODUCTION


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Introduction Instructors

Dr. Biju K Raveendran

Assistant Professor

A 413CS/IS Group

[email protected]

Consultation Time: Anytime between 10 A.M to 10 P.M Ms. Shubhangi K Gawali

Lecturer

A 418

CS/IS Group

[email protected]

2 August 2011 Biju K Raveendran@BITS Pilani. 2


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Policies to Follow Class room for Lectures & Tutorials

Class RoomLT1

No entry after 11:05 A.M (No excuses Please) No entry after 8:05 A.M (For tutorials)

No mark for attendance

Not allowed to leave in between the class

Lectures & Tutorials

All tutorials are converted to lecture sessions



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Course Administration Tests

Test 1

Day,Date & Time:Thursday, 17 09 2011

Weightage: 15% Mode: Closed Book

Test 2

Day,Date & Time:Thursday, 22 10 2011

Weightage: 15%

Mode: Closed Book

Make-up Policy

Medical certificate from the doctor (Dr. Ragvendra)

Photocopy of the medicial reports & Bills

No makeup for relatives marriage



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Course Administration Surprise Quizzes & Announced Quizzes

0 or more surprise quizzes + 0 or more Announced Quizzes

Surprise Quizzes: Any time during Class hours

Surprise Quizzes: Best (N-1) out of N is taken.

No makeup for surprise quizzes and Announced Quizzes

Weightage: 15%

Assignment(s) / Online(s) Programming in Nature.

Weightage: 25%

All deadlines are hard deadlines. Late submission is same as NO submission.



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Malpractice Regulations Any student or team of students found involved in mal practices in working out

assignments will be awarded negative marks equal to the weightage of thatassignment and will be blacklisted.

Any student or team of students found repeatedly more than once across allcourses involved in mal-practices will be reported to the DisciplinaryCommittee for further action. This will be in addition to the sanction mentionedabove.

A mal-practice - in this context - will include but not be limited to:

Submitting some other students / teams solution(s) as ones own;

Copying some other students / teams data or code or other forms of a solution; Seeing some other students / teams data or code or other forms of a solution;

Permitting some other student / team to see or to copy or to submit ones own solution;

OR other equivalent forms of plagiarism wherein the student or team does not work outthe solution and/or uses some other solution or part thereof (such as downloading it

from the web). The degree of mal-practice (the size of the solution involved or the number of

students involved) will not be considered as mitigating evidence. Failure on thepart of instructor(s) to detect mal-practice at or before the time of evaluation maynot prevent sanctions later on.



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Course Administration

Comprehensive Examination

Day, Date & Time: 09 12 2011 (AN)

Weightage: 30%

Mode: Closed Book



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Course Administration Material:

ftp://10.1.1.223/ACADEMICS_11-12/CS/CS_C372_OPERATING_SYSTEMS/

ftp://10.1.1.223/ACADEMICS_11-12/IS/IS_C362_OPERATING_SYSTEMS/

Text Book: Abraham Silberschatz, Peter Baer Galvin & Greg Gagne Operating

System Concepts, 8th edition, J ohn Wesley & Sons, 2008.

Reference Book: William Stallings, Operating Systems Internals and Design Principles,

6th edition, Pearson Edition, 2009.

Maurice J . Bach, The Design of the Unix Operating System, PHI,1993.

Note: Make it a habit to visit course ftp page. Thepage will be updated on a daily basis



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2 August 2011 9

Introduction What is an Operating system? Single most complex and essential software you run on your

machine.

Interface between the user and the computer hardware.

What does it do? How does it help? Helps user programmer by making the system easier (convenient)

to use.

Helps your programs run by providing resources and protectingthem.

Helps the system by keeping things running smoothly.

Helps the user programmer to do his job efficiently (use computer

hardware efficiently).

Biju K Raveendran@BITS Pilani.


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2 August 2011 10

Abstract View of System Components



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2 August 2011 11

Goals of an operating system Manage/coordinate hardware resources so that thesystem operates smoothly, efficiently, reliably andsecurely.

Present abstract system model to programmer thatpromotes simple and convenient access and control ofresources.

Maximize resource utilization. Operating system must contain functions needed by many

programs. I/O device control, memory allocation etc..

Selection of function must be in such a way that maximum numberof programs must get the benefit at the same time operatingsystem must not become bulky.



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2 August 2011 12

What if no operating system? All we have is a bare hardware We want to run a program

How do we load it?

How do we run it?

What happens when it completes?

For doing all these functions we need at least a minimal OS

It must be the resident code that run by default

Allow us to load program and run by allotting necessaryresources.

After completion of the user program control must comeback to the operating system.



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Types of OS Main frame systems

Batch, Multi programmed and Time sharing systems

Multi programming

Keeps multiple runnable jobs loaded in memory

Overlaps I/O processing of a job with computation ofanother.

Benefits from I/O devices that can operate asynchronously Requires the use of interrupts and DMA

Optimizes system throughput (number of jobs finished ina given amount of time) at the cost of response time.



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Time Sharing (Multi tasking) Systems

Logical extension of multiprogramming system A time unit is divided into small slice and each user can

be allocated CPU in round robin manner

Allows many users to share the computersimultaneously

Time shared OS uses multiprogramming and CPUscheduling to provide each user with a small portion of

time shared computer The CPU is multiplexed among several jobs that are kept

in memory and on disk.

Time sharing machine with Interactive I/O devicesimproves user response time

Gives illusion that each user has his own machine



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Desktop Systems computer system dedicated to a single user. Preferences -- User convenience and responsiveness

Multi processor Systems More than one processor in close communication, sharing the

computer bus, the clock and sometimes memory andperipheral devices.

Increased throughput, Economical, Increased reliability

Symmetric Multi processing systems

Tightly coupled system. Runs an identical copy of OS. Many processes can run at once without performance

deterioration. (modern operating systems support SMP)

Asymmetric multiprocessing

Master Slave Systems More common in extremely large systems



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Distributed Systems

Distribute the computation among several physical processors Loosely coupled system

Each processor has its own local memory; Processors communicate withone another through various communications lines, such as high-speedbuses or telephone lines.

Client server and Peer to Peer system

Enables Parallelism but speed up is not the goal.

Advantages Resources Sharing, Computation speed up load sharing,

Reliability, Communications

Clustered Systems Usually performed to provide high availability.

Asymmetric cluster: one machine will be in hot stand by mode

Symmetric cluster: 2 or more hosts are running applicationsand they are monitoring each other. Mode is more efficient.


Documents

Lect 01 02 Introduction