Slide 1-1 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter...

Operating Systems: A Modern Perspective, Chapter 1

Slide 1-1

Copyright © 2004 Pearson Education, Inc.


Slide 1-2


1Introduction


Slide 1-3


Why Study Operating Systems?

• Understand the model of operation– Easier to see how to use the system– Enables you to write efficient code

• Learn to design an OS

• Even so, OS is pure overhead of real work

• Application programs have the real value to person who buys the computer


Slide 1-4


What is an Operating System?

• A program or collection of programs that act as intermediary between the user of a computer and the computer hardware.

• Operating system goals:– Make the computer convenient to use.

– Use computer resources in an efficient manner.

– Coordinate among the various users and programs that are competing for computing resources.


Slide 1-5


Perspectives of the Computer

ApplicationSoftware

SystemSoftware

Hardware

(a) End UserView

(b) ApplicationProgrammer

View

(c) OS ProgrammerView

ApplicationSoftware

ApplicationSoftware

SystemSoftware

SystemSoftware

Hardware Hardware

cutsave

printsend

malloc()fork()

open()read-disk

track-mouse

start-printer


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Slide 1-7


Operating System Definition

• OS provides an interface between the computer hardware and users, applications and system software.

• OS manages computer resources.• OS controls and coordinates the use of the

computing resources among the various users/programs:– resource sharing among computer users/programs– protect users from each others


Slide 1-8


System Software

•Independent of individual applications, but common to all of them

•Examples

–C library functions

–A window system

–A database management system

–Resource management functions

–The OS


Slide 1-9


Using the System Software

LoaderLoader

OSOSDatabaseManagement

System

DatabaseManagement

System

WindowSystem

WindowSystem

ApplicationProgrammer

Sys

tem

Sof

twar

e

LibrariesLibraries

CompilerCompiler

Hardware

CommandLine

Interpreter

CommandLine

Interpreter

LibrariesLibrariesLibrariesLibraries

Software APISoftware API


Slide 1-10


Application Software, System Software, and the OS

Hardware Resources

Trusted OS

(Abstract Resources)

Software-Hardware Interface

OS Interface

System Software

(More Abstract Resources)

API

Application Software

Human-Computer Interface


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The OS as Resource Manager

•Process: An executing program

•Resource: Anything that is needed for a process to run

–Memory

–Space on a disk

–The CPU

•“An OS creates resource abstractions”

•“An OS manages resource sharing”


Slide 1-12


Resource Abstraction

load(block, length, device);seek(device, 236);out(device, 9)

write(char *block, int len, int device,int track, int sector) {

... load(block, length, device); seek(device, 236); out(device, 9); ...}

write(char *block, int len, int device,int addr);

fprintf(fileID, “%d”, datum);


Slide 1-13


Disk Abstractions

load(…);seek(…);out(…);

void write() { load(…); seek(…) out(…)}

int fprintf(…) { ... write(…) …}

(a) Direct Control (b) write() abstraction

(c) fprintf() abstraction

ApplicationProgrammer

OS Programmer


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Abstract Resources

Hardware Resources

OS

OS Resources (OS Interface)

Middleware

Abstract Resources (API)

Application

User Interface


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Abstract Machines

ProgramProgram ResultResult



… …

Idea

Idea

Idea

PhysicalMachine

AbstractMachines

…


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Resource Sharing

• Space- vs time-multiplexed sharing

• To control sharing, must be able to isolate resources

• OS usually provides mechanism to isolate, then selectively allows sharing– How to isolate resources– How to be sure that sharing is acceptable

• Concurrency


Slide 1-17


The OS as a Conductor

The OS coordinates the sharing and use of all the components in the computer


Slide 1-18


Multiprogramming

…

AbstractMachine Pi

OS Resource Sharing

Pi MemoryPi Memory

Pk MemoryPk Memory

Pj MemoryPj Memory

…Time-multiplexed Physical Processor

AbstractMachine Pj

AbstractMachine Pk

Space-multiplexed Physical Memory


Slide 1-19


Multiprogramming(2)• Technique for sharing the CPU among

runnable processes– Process may be blocked on I/O– Process may be blocked waiting for other

resource, including the CPU

• While one process is blocked, another might be able to run

• Multiprogramming OS accomplishes CPU sharing “automatically” – scheduling

• Reduces time to run all processes


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How Multiprogramming Works

Process 1

Process 2

Process 3

Process 4

Space-multiplexed Memory

Time-multiplexed CPU


Slide 1-21


Speeding Up the Car Wash

VacuumInside

Wash Dry

VacuumInside

Wash Dry

(a) The Sequential Car Wash

(b) The Parallel Car Wash


Slide 1-22


Multiprogramming Performance

Time

Using the processor

I/O operation

0 ti

Pi’s Total Execution Time, ti

(a) Pi’s Use of Machine Resources

Time

P1

P2

Pi

PN

…

…

(a) All Processes’ Use of Machine Resources


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OS Strategies

• Batch processing

• Timesharing

• Personal computer & workstations

• Process control & real-time

• Network

• Distributed

• Small computers


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Batch Processing

Job 19

Input Spooler Output Spooler

Job 3

Input Spool Output Spool


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Batch Processing(2)

• Uses multiprogramming

• Job (file of OS commands) prepared offline

• Batch of jobs given to OS at one time

• OS processes jobs one-after-the-other

• No human-computer interaction

• OS optimizes resource utilization

• Batch processing (as an option) still used today


Slide 1-26


A Shell Script Batch File

cc -g -c menu.ccc -g -o driver driver.c menu.odriver < test_data > test_outlpr -PthePrinter test_outtar cvf driver_test.tar menu.c driver.c test_data test_outuuencode driver_test.tar driver_test.tar >driver_test.encode


Slide 1-27


Timesharing Systems

PhysicalMachine

AbstractMachines

…

Command

Command

Command

Result

Result

Result


Slide 1-28


Timesharing Systems(2)

• Uses multiprogramming

• Support interactive computing model (Illusion of multiple consoles)

• Different scheduling & memory allocation strategies than batch

• Tends to propagate processes

• Considerable attention to resource isolation (security & protection)

• Tend to optimize response time


Slide 1-29


Personal Computers

• CPU sharing among one person’s processes

• Power of computing for personal tasks– Graphics– Multimedia

• Trend toward very small OS

• OS focus on resource abstraction

• Rapidly evolved to “personal multitasking” systems


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Process Control & Real-Time

• Computer is dedicated to a single purpose

• Classic embedded system

• Must respond to external stimuli in fixed time

• Continuous media popularizing real-time techniques

• An area of growing interest


Slide 1-31


Networks

• LAN (Local Area Network) evolution• 3Mbps (1975) 10 Mbps (1980) 100 Mbps

(1990) 1 Gbps (2000)• High speed communication means new way to do

computing– Shared files– Shared memory– Shared procedures/objects– ???


Slide 1-32


Distributed OS

• Wave of the future

Distributed OS

App App

App

App

AppApp

Multiple Computers connected by a Network


Slide 1-33


Distributed Systems• Distribute the computation among several physical

processors.• Multiprocessor system: Tightly coupled systems –

processors share memory and a clock; communication usually takes place through the shared memory.

• Loosely coupled systems – each processor has its own local memory; processors communicate with one another through various communication lines

• Advantages of distributed systems:– Resource sharing, Computation speed up– Reliability, Communication


Slide 1-35


Small Computers

• PDAs, STBs, embedded systems became commercially significant

• Have an OS, but– Not general purpose

– Limited hardware resources

– Different kinds of devices• Touch screen, no keyboard

• Graffiti

– Evolving & leading to new class of Oses

• PalmOS, Pocket PC (WinCE), VxWorks, …


Slide 1-36


Evolution of Modern OS

Modern OS

Batch

Timesharing

PC & Wkstation

Network OS

Real-TimeMemory Mgmt

ProtectionScheduling

FilesDevices

Memory Mgmt

ProtectionScheduling

System software

Human-Computer Interface

Client-Server Model

Protocols

Scheduling

Small Computer

Network storage,Resource management


Slide 1-37


Examples of Modern OS• UNIX variants (e.g. Linux) -- have evolved

since 1970• Windows NT/2K -- has evolved since 1989

(much more modern than UNIX– Win2K = WinNT, V5

• Research OSes – still evolving …• Small computer OSes – still evolving …• Book provides Linux examples• This course will use Windows NT as the

main example


Slide 1-38


The Microsoft OS FamilyWin32 APIWin32 API

Windows CE(Pocket PC)

Windows CE(Pocket PC)

Windows 95/98/MeWindows 95/98/Me

Windows NT/2000/XPWindows NT/2000/XP

Win32 API SubsetWin32 API Subset

Win32 API SubSetWin32 API SubSet


Slide 1-39


Microsoft Windows NT

• Heavily window-oriented• Foundation behavior is windows-

independent– We will focus on the foundation– Use only the “MS-DOS prompt” -- cmd.exe

OS API

NT Kernel

NT User Interfaceand Graphics

NT Executive


Slide 1-40


Windows NT (cont)

• OS API has text orientation (like UNIX)

• Object-oriented implementation

• Heavy use of threads

• Broad spectrum of synchronization tools

• Modern I/O system


Slide 1-41


ApplicationsApplications

VxWorks Runtime SystemVxWorks Runtime System

VxWorks Organization

VxWorks Configurable Core OS Extension

VxWorks Configurable Core OS Extension

Wind MicrokernelWind Microkernel


Slide 1-42


Windows CE Organization

Kernel

OEM Abstraction Layer

Win32 API (& Network Extensions)

Graphics,Window Mgr,

andEvent Mgr

Device Drivers

ObjectStore

Networkand

CommServices

Shells and Applications

Slide 1-1 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter...

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