© 2004, D. J. Foreman 1

CS350/550

Operating Systems

© 2004, D. J. Foreman 2

Administrivia Assignments

■ Homework on most chapters■ Approximately 8 lab assignments■ 6 Projects (5 for CS311)

Exams■ Midterm■ Final (comprehensive)

Quizzes■ Random, 10 minutes each (if any)

Grades required to pass (after curving)■ >= 70 average on labs(CS350)/projects ■ >= 70 average on (h/w + quizzes) together■ >= 60 on midterm to pass

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Course OutlineIntroduction 1 0.5 yH/W & S/W Concepts 2 3.5 yProcesses 3 3 yThreads 4 3Mutual Exclusion 5 3Monitors 6 3Deadlock 7 3Midterm 1.5Scheduling 8 3Real Memory Mgmt 9 3Virtual Memory Org 10 3Virtual memory mgmt 11 3Disk Performance 12 3File mgmt 13 3VM n/a 1.5Distributed Systems 1.5

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Introduction & Motivation

Wanted – a methodology to:■ get more work done in a fixed time■ allow multiple users on 1 computer■ allow programs to interact with each other■ maximize memory and CPU utilization■ reduce the need for device handling■ allow programs' parts to be shared■ make the system more usable (friendlier?)■ make system faster

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Why Study Operating Systems?

• Understand support structure so we can:– Exploit system features– Learn to write more effective code

• Learn to design an OS

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What IS an Operating System?A "virtual machine" that provides:

■ An abstraction of some virtual computer■ Common functionality for apps■ Security across apps/devices■ Some level of concurrency (maybe)■ Portability across real machines■ Simplified access to resources■ Sharing of resources■ Services for apps

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PerspectivesEnd user

■ Getting work doneApplication programmer

■ More efficient use of system■ Make work easier for user

O/S programmer■ Exploit h/w■ Enhance performance, usability

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Examples of System SoftwareTools - a DBMS

API's - functions to create windows

Resident programs – resource mgmt

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Abstractions User

■ Windows, folders

Application programmer■ OS, language API's■ Run-time libraries & DLL's■ Shell

OS programmer■ Hardware interfaces■ Machine instructions■ OS service interfaces

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Abstract View of System

User Space

O/S Space

Application Programming Interface

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The APIApplication Programming Interface

■ Exposes a portion of an environment■ Provides services

• I/O

• Memory

• Protection

• Security

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Evolution of OS'sUni-programming

■ DOSApparent multiprogramming

■ Windows Versions 2 to 3.1True multi-programming

■ UNIX/LINUX, OS/2, Windows95+■ Mainframe systems:

• MVS, VMS, VM

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OS Strategies Batch

■ All work pre-scheduled Timesharing

■ Multi-user, Interactive PC's and Workstations

■ Single-user, interactive Embedded

■ Satellites, robots, etc PDA's

■ Single-user, interactive, small Network OS's

■ Multi-machine, multi-user

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Resource ManagementResources

■ Memory■ CPU cycles■ I/O

• Includes networks, robot arms, motors

• That is, any means of getting information (or signals) into or out of the computer

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Resource SharingWhy do we need to share?

■ Greater throughput■ Lowers cost of resources■ Allows more resources to be available

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The KernelImplements O/S functionsPrivileged, non-interruptibleSometimes reduced to a "micro-kernel"

■ Absolutely minimal set of functions required to be in privileged mode

■ Micro-kernel does NOT include :• Device drivers

• File services

• Process server

• Virtual memory mgmt