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1.1 Sumit Mittu, Lecturer, Computer Applications, LPUOperating System Concepts

Chapter 1: Introduction

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In this lecture

Operating-System Evolution

Multi-processor Systems

Parallel Processing System Distributed System

Real-Time Operating System (RTOS)

OS for Hand-held and multimedia systems

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Objectives

To provide an insight into evolution of so-called

modern- operating systems

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Computing Environments

Traditional computer

Blurring over time

Office environmentPCs connected to a network, terminals attached to

mainframe or minicomputers providing batch andtimesharing

Now portals allowing networked and remote systemsaccess to same resources

Home networks

Used to be single system, then modems

Now firewalled, networked

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Such systems have more than one processors incommunication so as to boost the system performance.

The major advantages of such systems:

Increased throughput

By increasing no. of processors, we can get multiplejobs done at same time.

The speed-up ratio with N processors is however lessthan N due to certain overheads of processing

Economy of Scale

Overall cost of system is reduced as peripherals are

shared

Increased reliability

Failure of one processor may not mean failure ofcomplete system. It may just slow down the system.

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Multiprocessor systems come in two variants:

Tightly-coupled systems

Also known as Parallel Processing Systems

Multiple processors housed in same chassis/cabinet board

Loosely-coupled systems

Also known as Distributed Systems

Multiple processors installed in different systems,interconnected through networking technologies

Latest Developments in this area is:

Multi-core systems

Single processor chip with multiple processing chores

(units) in it.

Blade server systems

Multiple processor boards, I/O boards, networking boardsare placed in same chassis/cabinet

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(Parallel Processing) Operating systems for multi-processor systems can be

designed to let the system work in one of the two processingmodes:

Asymmetric Multi-processing (ASMP)Each processor is assigned a specific task

Processors are bound in a master-salve relationship

Symmetric Multi-processing (SMP)

All processors are peers, no master-slave relationship

Each processor can perform all types of tasks

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(Parallel Processing) The difference between symmetric and asymmetric

multiprocessing may result from either hardware or software.

Special hardware can differentiate the multipleprocessors, or

The software can be written to allow only one masterand multiple slaves.

For instance,

Sun's operating system SunOS Version 4 providedasymmetric multiprocessing, whereas

Suns operating system SunOS Version 5 (Solaris) issymmetric multiprocessing on the same hardware.

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Distributed System:

Client-Server Client-Server Computing

Dumb terminals replaced by smart PCs

Many systems now servers, responding to requests generated byclients

Compute-server provides an interface to client to requestservices (i.e. database)

File-server provides interface for clients to store and retrieve

files

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Distributed System:

Peer-to-Peer (P2P) Computing

P2P does not distinguish clients and servers

Instead all nodes are considered peers

May each act as client, server or both

Node must join P2P network

Registers its service with central lookup service on network,

or Broadcast request for service and respond to requests for

service via discovery protocol

Examples include Napsterand Gnutella

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Real Time Operating Systems

Used when rigid time requirements have been placed on operationof processor or flow of data

Often used as a control device in a dedicated application.

A real-time system has well-defined, fixed time-constraints.

Processing must be done within these constraints or else thesystem willFail.

Few Examples:

Systems that control scientific experiments

Medical imaging systems

Industrial control systems

Fuel-injection systems Weapon controllers

Home-appliance controllers, etc.

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Real Time Operating Systems

Real Time systems can be of two types

HARD REAL TIME SYSTEM

It guarantees that critical task be completed on time. All delays be bounded

Secondary storage of any sort is usually limited or missing

Required data being stored in short-term memory or ROM

SOFT REAL TIME SYSTEM

Less restrictive than hard real-time system

Critical real time task gets priority over other tasks andretains priority until it completes

OS Kernel delays need to be bounded

Have limited utility than hard real-time systems

Due to lack of deadline support, they are risky to use forindustrial control or robotics

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OS for Hand-held & Multimedia devices

The basic criteria for such systems is that they are limitedresources such as:

Small memory

No or small permanent storage

Small screen/display units

Limited input capabilities, etc.

Devices such as mobile phones, PDAs, Pocket-PCs, iPods, etc.

Common Operating systems for such devices:

Android

Symbian-OS

Windows CE

Windows Mobile Edition, etc.

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End of lecture #6

Documents

12735_os-06 [13-Feb]