IV 1 intro to OS

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Silberschatz, Galvin and Gagne20021.1

Introduction to Operating Systems

Evolution of OS; various OS.

OS Concept; OS Structure.

Processes:

Process Creation, Termination, Process States.

Threads, Implementing Threads in User Space.

Inter Process Communication:Race Condition, Critical Region, Mutual Exclusion

IPC Problems:

Dining Philosopher, Readers & Writers, SleepingBarber Problem.

Resources:

Introduction to Deadlock, Ostrich algorithm.

Deadlock Detection and Recovery & otheraspects.

Operating System Concepts


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Silberschatz, Galvin and Gagne20021.2Operating System Concepts

Chapter 1: Introduction

What is an Operating System?

Different Types of Operating System

Mainframe Systems

Desktop Systems

Multiprocessor SystemsDistributed Systems

Clustered System

Real -Time Systems

Handheld Systems

Computing Environments


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What is an Operating System?

A program that acts as an intermediary betweenauserof a computer andthe computer hardware.

Operating systemgoals:

Execute user programs and make solving user

problems easier.Make the computer system convenient to use.

Use the computer hardware in an efficient manner.


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Computer System Components

1.Hardware provides basic computing resources (CPU,memory, I/O devices).

2.Operating system controls and coordinates the useof the hardware among the various applicationprograms for the various users.

3.Applications programs define the ways in which thesystem resources are used to solve the computingproblems of the users (compilers, database systems,video games, business programs).

4.Users(people, machines, other computers).


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Abstract View of System Components

Boot Loader

Program


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Operating System Definitions

Resource allocator Manages and allocatesresources.

Control program Controls the execution ofuser programs and operations of I/O devices .

Kernel The one program running at all times(all else being application programs).


7/26Silberschatz, Galvin and Gagne20021.7Operating System Concepts

Mainframe Systems

Reducesetuptime bybatchingsimilar jobsAutomaticjob sequencing automaticallytransfers control from one job to another.First rudimentary operating system.

Resident monitor initial control in monitor

control transfers to job

when job completes control transfers back to

monitor



Memory Layout for a Simple Batch System



Multiprogrammed Batch Systems

Several jobsare kept in main memory at the sametime, and the CPU is multiplexed among them.



OS Features Needed for Multiprogramming

I/O routinesupplied by the system. Memory management the system mustallocate the memory to several jobs.

CPU scheduling the system must choose

among several jobs ready to run. Allocation of devices



Advantage of Multiprogramming

In Multiprogramming job switched toanother job and so on

CPU will never sit idle

OS has to make decision for the users



Time-Sharing SystemsInteractive Computing

TheCPU is multiplexed among several jobsthatare kept in memory and on disk (the CPU is allocatedto a job only if the job is in memory).

A job swappedin and out of memory to the disk.

On-line communication between the user and thesystem is provided;when the operating systemfinishes the execution of one command, it seeks thenext control statement from the users keyboard.

On-line system must be available for users to accessdata and code.



Desktop Systems

Personal computers computer system

dedicated to a single user. I/O devices keyboards, mice, display screens,small printers.

User convenience and responsiveness.

Can adopt technology developed for largeroperating system often individuals have sole useof computer and do not need advanced CPUutilization of protection features.

May run several different types of operatingsystems (Windows, Mac OS, UNIX, Linux)



Parallel Systems

Multiprocessor systemswith more than one

CPU in close communication. Tightly coupled system processors sharememory and a clock; communication usuallytakes place through the shared memory.

Advantages of parallel system: Increasedthroughput

Economical

Increased reliability

graceful degradationfail-soft systems


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Parallel Systems (Cont.)

Symmetric multiprocessing (SMP)

Each processor runs an identical copy of theoperating system.

Many processes can run at once withoutperformance deterioration.

Most modern operating systems support SMP

Asymmetric multiprocessingEach processor is assigned a specific task; masterprocessor schedules and allocate work to slaveprocessors.

More common in extremely large systems


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Symmetric Multiprocessing Architecture


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Real-Time Systems

Often used as a control device in a dedicatedapplication such as -- controlling scientificexperiments, medical imaging systems,industrial control systems, and some displaysystems.

Well-defined fixed-time constraints.

Real-Time systems may be eitherhardorsoftreal-time.


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Real-Time Systems (Cont.)

Hard real-time:

It guarantee that critical tasks be completed on time Secondarystorage limited or absent, data stored in short term memory,

or read-only memory (ROM)

Conflicts with time-sharing systems, not supported by general-purpose

operating systems.

Soft real-time

Critical real time task gets priority and

retains that priority until tasks completed Limited utility in industrial control of robotics

Useful in applications (multimedia, virtual reality) requiring advanced

operating-system features.


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Distributed Systems

Distributethe computation among several physicalprocessors.

Loosely coupled system each processor has itsown local memory; processors communicate with

one another through various communications lines,such as high-speed buses or telephone lines.

Advantages of distributed systems.

Resources Sharing

Computation speed up load sharing Reliability

Communications


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Distributed Systems (cont)

Requires networking infrastructure. Local area networks (LAN) or Wide areanetworks (WAN)

May be either client-server or peer-to-peer

systems.


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General Structure of Client-Server


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Clustered Systems

Clustering allowstwo or more systemstoshare storage.

Provideshigh reliability.

Asymmetric clustering:one server runs theapplication while other servers standby.

Symmetric clustering:all N hosts are runningthe application.


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Handheld Systems

Personal Digital Assistants (PDAs)

Cellular telephones

Issues:

Limited memory Slow processors

Small display screens.


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OS Evolution

MULTICS was developed from1965 to 1970 at MIT as

computingutility.

Many of idea are used by Bell Lab to develop UNIX.

UNIX OS developed by circa in 1970 for Microcomputer.

After that UNIX is basic OS to developed OS such as

Microsoft windows, IBM,OS/2


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Migration of Operating-System Concepts and Features


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Silb ht Gli dG 2002126O ti S t C t

Computing Environments

Traditional computing

Web-Based Computing

Embedded Computing

Documents

IV 1 intro to OS