OS module 1-A

8/3/2019 OS module 1-A

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Introduction to


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Objectives

1.

A firm understanding about OS, its primarypurpose and goals to a computer system;

2. Trace the history of OS and the developmentof systems.

3. Concepts basic to OS;

4. OS components and its componentmanagement;

5. Computer system operations, structure of thecomputer systems and hardware protection;

6. Services of OS.


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Introduction

Major components of Computer Systems: Hardware

Computer users

Software

Note: Without software, computer is of little use. However

with software, computer can store, manipulate andretrieve information, and can engage in many otheractivities.


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Introduction

Software can be grouped into:

System software (OS and utilities)

Application software (user programs)

User1 User2 User3 User n

compiler assembler text editor databasesystems

A p p l i c a t i o n P r o g r a m s

OPERATING SYSTEMS

Computer Hardware


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Introduction

Utilities ApplicationSoftware

OS

device device device

CPU

M e m o r y


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Introduction

Without an OS, a user who wanted to run aprogram that uses some of the resources ofthe system will need to write a program that

includes code for driving the resourcesrequired. Code for handling keyboard,printers, etc. have to be written.


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Introduction

To alleviate these difficulties, OS contains setof procedures for driving the resources of thesystem, thus it frees the users from the dirty

details of writing these drivers for the devicesinvolved in the problem being solved.


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What is OS?

Program implemented either in firmware orsoftware which acts as an intermediarybetween the user of a computer and the

computer hardware.Collection of system programs (procedures)

that together control the operation of a

computer system. The purpose is to provide an environment

wherein users can execute programs


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Types of OS

Desktop OS

Typically installed on PC type of computer, usedby a singe user at a time, and may or may not be

connected to a network.

Server OS

Installed in a more powerful computer connectedto a network enabling multiple users to accessinformation such as e-mails, files, and software


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Network OS

NOS

Either desktop or server OS that enables acomputer to communicate with other computers

through network cable (eg. CAT-5/6) or wirelesstransmissions (eg. wiFi / wiMAX) and coordinatesnetwork communication from sharing files andhardware devices to sending e-mail and videoconferencing.


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Different OS

Mainframe OS

designed to optimize utilization of hardware.

PC OS

supports games, business applications, and thelike.

Handheld OS

designed to interface with the computer toexecute programs.


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Primary goals of an OS

1. Make the computer convenient to use

2. Use the computer hardware in an efficientmanner.


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Sizes of OS

Its size & complexity depend on a number offactors:

Computer system characteristics: (has one or more

processors)

Provides facilities: (allows interactive use or not?)

Applications to support (allows many users to use thesame application simultaneously or not?)


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Why study operating systems?

In this course, we will NOTwrite OS but One of the largest and complicated system

software.

Draws on lots of areas Software Engineering, Computer Architecture, Data Structures,

Networks and Algorithms etc.

If certain things in the OS need to be changed,

better understand them first!

Can apply techniques used in an OS to other areas complex data structures, conflict resolution, concurrency,

resource management


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What does an OS do?

It controls the function of the computersystem. OS includes programs that:

Initializes the hardware Provides basic routine for device control Provides for the management, scheduling

and interaction of tasks Maintain system integrity, and Handle errors


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Where are OS found?

Complexity of OS depends on the type offunctionality it provides:

Some OS manage many users on a network.

Found in petrol pumps, airplanes, videorecorders, washing machines and car engines.


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What is a General Purpose OS?

Provides the ability to run a number ofprograms.

MS Windows, UNIX, Linux, etc.


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Viewpoints of an OS

Similar to a government

Resource Allocator/Manager

Control Program

An extended machine

Note: OS runs in a kernel/supervisor/monitor

mode (protection from user by the hardware)


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Single-user vs. Multi-user OS

Single user OS provides access to the computersystem by a single user at a time. Examples are: Win95, WinNT, Win2K, Win XP

Provides with the capability to perform tasks onthe computer system such as writing programsand documents, printing and accessing files


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Single-user vs. Multi-user OS

A multi-user OS allows more users to accessthe computer system at one time via network,thus accessing the system remotely from

another terminal. Examples are UNIX and mainframes such as the

IBM AS400.


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Multi-user OS

Advantages

Hardware is very expensive, and it lets a numberof users share this expensive resource (reduced

cost) Since resources are shared, they are more likely

to be in use than sitting idle being unproductive.

(increased resource utilization)


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Multi-user OS

Disadvantages

More users slow down the performance of thesystem.

Cost of hardware, requires a lot of disk spaceand memory.

Multi-user OS cost is more than software for

single-user.


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Operating System Utilities

OS consists of hundreds of thousands ofprogram codes and stored on hard disk.Portions of the OS are loaded into theRAM when needed.

Utilities are provided for: Managing files and documents Development of programs and software Communicating with people and with other

computer systems Managing user requirements for programs,

storage space and priority.


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OS Interfaces

OS provides each user with an interfacethat accepts, interprets and executes user

commands or programs.

Shell or command line interpreter. (CLI)

In some systems, this might be a simple line-

by-line text mode (such as DOS or UNIX) orhighly graphical (such as Windows)


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What is a multitasking OS?

Provides the ability to run more than oneprogram at once.

Each of these tasks the user is doing appearsto be running at the same time

Advantage: increased productivity Disadvantage: more memory required.


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Multitasking withOne program


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Multitasking withTwo Programs


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Multitasking withThree Programs


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Utilization with multitasking


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Evolution of OS

Programmed in machine language and usedfront panel switches for input. The programmer is also the operator interacting with

the computer directly from the system console(control panel).

Introduce Device drivers (a subroutineperforming various I/O devices which involvescomplex sequences of device-specificoperations)

Setup time is very high.


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Evolution of OS

Problems:

Programmers needed to sign-up inadvance to use the computer one at a time.

Executing a single program (often called

job) required substantial time to setup thecomputer.


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A. Simple Batch Systems

Similar jobs are batched and run together withno direct interaction between user and thecomputer during execution.

Automatic job sequencing

Computers are extremely valuable.

Pre-OS: Resident Monitor Initial control in monitor Control transfers to job When job completes, control transfers back to

monitor


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Overlapped CPU and I/O operations

Online Processing CPU is directly connectedto card readers and line printers


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Overlapped CPU and I/O operations

Off-line Processing

Spooling Simultaneous Peripheral Operation Online.

Uses disk as input device and for storing output files.


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B. Multiprogrammed Batch Systems

OS keeps several jobs in memory at a time andpicks and begins to execute one of the jobs inthe memory.

Drawback: Causes the computer system to stopexecuting when the monitor encounters error(bug). Other jobs in the memory will not be

executed as well.


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C. Time sharing systems

Interactive Computing Allows interaction between user and process.

The CPU executes multiple jobs by switchingbetween them but the switches occur so

frequently that users may interact with eachprogram while it is running.

Monitor

Job 1

Job 2

Job 3

Job n

T1

T2

T3

T4


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Time sharing systems

Time sharing (or multitasking) is a logicalextension of microprogramming.

Job A Job B

0 5 10 15 20 25 30 35 40 time

Uniprogramming: Job A and B end at time 36CPU is idle 47%I/O is idle 53

CPU

I/O


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Time sharing systems

pure multiprogrammingJob A and B end at time 20.

0 5 10 15 time

Job A Job B

CPU

I/O


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Time-sharing mainframe withterminals

Mainframe

TerminalController


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Sample problem #1:

Consider a system designed to run only oneuser program at a time. Suppose the user isrunning a program designed to execute the ff

sequence of instructions:while (not end of input) {

read from the card readerprocess the data

: :write to the printer: :

}


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Sample problem #1(cont.)

Assuming that the computer system has thefollowing characteristics:

Card reader: 300 cards / min.

Line printer : 300 lines / min.

CPU : 1 s/instruction


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Sample problem #1(cont.)

Suppose it takes about 10,000 instructions toprocess each line (one card) of input, then a cardwill require the ff:

Input phase

(1 min/ 300 cards) x (60,000 ms/min) = 200 ms

Process phase

(10,000 inst) x (1 s/inst) x (1 ms / 1000 s) = 10 ms

Output phase

(1 min/ 300 cards) x (60,000 ms/min) = 200 ms

CPU utilization = (10 / 410) x 100% = 2.4 %

Therefore, it shows poor CPU utilization


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Its your turn

Sample Question #2:Given the followingcharacteristics of a single-user system:

Card reader : 600 cards /min

Line printer : 100 lines /min CPU : 1 sec / instruction

Suppose it takes 1,000 instructions to processeach line of input and produce one line of output,compute the CPU utilization, and input andoutput device utilization.


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D. Personal Computer

Personal Computer computer system dedicated to a single user

I/O devices

User convenience and responsiveness

Adopt technology developed for larger OS oftenindividuals have sole use of computer and do not needadvance CPU utilization or protection features

May run several different types of OS


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Types of parallel systems

Symmetric multiprocessing model (SMP) Each processor runs an identical copy of the OS

and these copies communicate with each other

Many processes can run at once withoutperformance deterioration

Most modern OS support SMP systems

CPU 1 CPU2 CPU3 CPU4


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Types of parallel systems

Asymmetric multiprocessing model (AMP)

Each processor is assigned a specific task;master processor schedules, and allocated work

to slave processors. More common in extremely large systems

Master CPU

Slaves CPU


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Assignment

Research on the differences betweenSymmetric and Asymmetric multiprocessingsystems in terms of their:

Function

Use / Application

Give applications for each


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F. Distributed Systems Distribute computation among several

processors.


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F. Distributed Systems Loosely coupled systems

processors do not share memory or a clock, instead,each processor has its own local memory.

Requires networking infrastructure LAN or WAN implementations May be either client-server of peer-to-peer systems

Resources on each machine are managed by

that machines OS and working together tomanage the collective network resources

R f b ildi Di t ib t d


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Reasons for building DistributedSystems

Resource sharing

Computation Speedup allows to distribute the computation among various

sites. Movement of jobs is called load sharing

Reliability

Communications


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Distributed Systems : Clustered

Clustering allows two or more systems toshare storage.

Provides high reliability

Asymmetric clustering

one server runs the application while otherservers standby

Symmetric clustering

all n hosts are running the application.


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G. Real-time systems

Used as a control device in a dedicatedapplication Eg. controlling scientific experiments, medical

imaging systems, industrial control systems, and

some display systemsReal-time OS

Designed to support execution of tasks withinspecific clock time constraints.

Correctness of a processing task is dependenton the clock time at which the processingoccurred

Example: Windows XP, Mac OS X


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Real-time systems

Deadline (time critical) requirement well-defined fixed-time constraints.

Eg. Industrial control systems, weapons

systems, computer controlled products, ballisticmissile control systems, airline reservationsystems.

Network to access Real time


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Network to access Real-timeNetware server

NETWORK

Windows XP Windows XP

Windows XP Mac OS X Netware server

H dh ld S


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Handheld Systems

Personal Digital Assistants (PDAs)

Cellular telephones

Issues

Limited memory

Slow processors

Small display screens

(still true today?)


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H. Embedded Systems

Also known as dedicated systems.

Perform a specific task only and cannot run awide variety of programs unlike general-

purpose systems.

Migration of OS Concepts and


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Migration of OS Concepts andFeatures


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Major Milestone in OS development

UNIX (1968)

8-bit OS

First widely used multiuser , multitasking OS for

minicomputers

CP/M (1975)

8-bit OS

First OS that allowed serious business work onsmall personal computer. VisiCalc (1978) was thefirst business calculation program for CP/M.


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MS-DOS (1980) 16-bit OS

First OS for IBM PC family of computers. Lotus 1-2-3 and WordStar were introduced for PC.

PC-DOS (1981) 16-bit OS

IBM version of MS-DOS

Mac OS (1984) 16-bit OS

First graphical user interface OS that introduced

the use of mouse to PC-based systems.


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Mac OS X

OS X is version 10 of the Apple Macintosh OS.

First "complete revision" of the OS since the

previous version is OS 9, with a focus onmodularity so that future changes would beeasier to incorporate.

Incorporates support for UNIX -basedapplications as well as for those written just forthe Macintosh.


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Mac OS X Original Mac OS X release has code name

(name after big cats) Cheetah.

Public Beta was called Kodiak Mac OS X 10.1 was called Puma

Mac OS X 10.2 was called Panther

Mac OS X 10.3 was called Jaguar

Mac OS X 10.4 was called Tiger

Mac OS X 10.5 was called Leopard (2007)

Mac OS X 10.5 was called Snow Leopard


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Linux

Unix-like OS designed to provide PC users a freeor very low-cost OS

Has a very efficient and fast-performing system.

Linux's kernel was developed by LinusTorvalds at the University of Helsinki in Finland

An acronym for Linus Unix.


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Windows 3.0 (1990)

16-bit OS

First usable version of a graphical OS for the PC

Windows for Workgroups (Windows 3.11)

1993, 16-bit OS

First Microsoft Windows with peer-to-peernetworking support for the PC.



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Windows NT (New Technology) 1993, 32-bit OS

Microsofts first attempt to bring a true 32-bit

preemptive, multitasking OS with integratednetwork functionality offered in a workstation andserver versions.

Windows 95 (1995) 16/32-bit OS Upgrade to Win 3.x with improved user interface,

hardware support with 32-bit code, and providesbackward compatibility for 16-bit applications.



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Windows 95

Released on August 24, 1995

Referred to as Windows 4.0 or by the internal

codename Chicago


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Windows 98 (1998) 32-bit OS

Implemented many bugs fixes to Windows 95,

more extended hardware support, and fully 32-bit.

Windows 2000 (2000) 32-bit OS

Revision of Win NT that is faster and morereliable, comes in several versions includingProfessional, Server, Advanced Server, andDataCenter.



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Windows ME (Millennium Edition)

2000, 32-bit OS

Upgrade of Win 98 designed for home use with

improved multimedia capabilities

Windows XP (2001)

32/64-bit OS

Successor to Win Me 2000 Professional withHome, Professional, Tablet PC, and MediaCenter versions.



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Windows XP

Has a codename of Whistler

Stands for eXPerience.

XP shared the Whistler code-name with Windows2003 Server.


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Windows Server 2003 (2003)

32/64 bit OS

Has Standard, Web, Enterprise, and DataCenter

Editions designed as a server platform for MS.NET initiative which integrates all types ofdevices PC, handheld computers, cell phones,and home appliances for communications over

the internet.

Windows Vista (2008)

Windows 7 (2009) - Windows 8



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Assignment

Research on other open-source OS (min. of10). Write important information regardingsuch OS including:

Description and history

Proponents and supporters

Prog. Language used, OS which was based

Year it was first release, and its versions Licensing, Server/workstation/mobile, others

Print the OS milestone graph.


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Mobile OS

Symbian OS iPhone OS

RIM's BlackBerry Windows Phone,

Linux Palm WebOS,

Android Maemo


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End of Presentation

OS module 1-A

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