Page 36 - DCAP403_Operating System

Deepak Mehta, Lovely Professional University Unit 3: Operating System Structure

Unit 3: Operating System Structure Notes

CONTENTS

Objectives
Introduction
3.1 Operating System Services
3.2 System Calls

3.3 System Programs
3.4 Operating System Structure
3.4.1 Monolithic Systems
3.4.2 Client-server Model
3.4.3 Exokernel
3.5 Layered Structure

3.6 Virtual Machine
3.7 Summary
3.8 Keywords
3.9 Self Assessment

3.10 Review Questions
3.11 Further Readings

Objectives

After studying this unit, you will be able to:
Describe operating system services

Define system calls
Explain system programs
Know operating system structure
Describe layered structure

Introduction

Every general-purpose computer must have an operating system to run other programs.
Operating systems perform basic tasks, such as recognizing input from the keyboard, sending
output to the display screen, keeping track of files and directories on the disk, and controlling

peripheral devices such as disk drives and printers.
For large systems, the operating system has even greater responsibilities and powers. It is like
a traffic cop – it makes sure that different programs and users running at the same time do not

interfere with each other. The operating system is also responsible for security, ensuring that
unauthorized users do not access the system.
System calls provide an interface between the process and the operating system. System calls
allow user-level processes to request some services from the operating system which process

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