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PROPRIETARY MATERIAL. © 2007 The McGrawHill Companies, Inc. All rights reserved. No part of this PowerPoint slide may be displayed, reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited distribution to teachers and educators permitted by McGrawHill for their individual course preparation. If you are a student using this PowerPoint slide, you are using it without permission.
Chapter 1: Introduction Dhamdhere: Operating Systems— Copyright © 2008
What is an operating system ?
• An operating system (OS) is a collection of programs that achieve effective utilization of a computer system by providing
– Convenient methods of using a computer
* Saves users’ time and boosts their productivity
– Efficient use of the computer
• An OS has several kinds of users
– The OS meets diverse requirements of different kinds of users
– Each user has a different view of what an OS is, and what it does. Each of these views is called an abstract view
Chapter 1: Introduction Dhamdhere: Operating Systems— Copyright © 2008
Abstract views
• An abstract view focuses on the essential characteristics of a system
– It contains some selected characteristics, and ignores others
* It helps to control complexity in designing and understanding a system, by hiding unnecessary detail
– For example, two abstract views of a car:
* The driver’s view contains the rear-view mirror, steering, gear shift, and speedometer but ignores engine details
* The mechanic’s view contains fluid levels, electrical system, …
Q: Give examples of abstract views
A: View of an abstract data type, object, ..
Chapter 1: Introduction Dhamdhere: Operating Systems— Copyright © 2008
Abstract views
• Abstract views are used in
– Software requirements specification
* Specify what functions a system should perform
The abstract view of a specific function helps in understanding the system data and fundamental operations on them
– Software design and implementation
* ‘Hiding’ the details of functions and subsystems while designing or implementing other functions and subsystems helps to control complexity
Chapter 1: Introduction Dhamdhere: Operating Systems— Copyright © 2008
A designer’s abstract view of an OS
• User interface: Accepts commands from users: GUI, command line interface • Nonkernel programs: Implement user commands
• Kernel: Core of the OS─controls the computer, provides functions & services
Chapter 1: Introduction Dhamdhere: Operating Systems— Copyright © 2008
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