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Chapter 2 - M02_STAL6329_06_SE_C02.QXD 3:33 AM Page 50...

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CHAPTER O PERATING S YSTEM O VERVIEW 2.1 Operating System Objectives and Functions The Operating System as a User/Computer Interface The Operating System as Resource Manager Ease of Evolution of an Operating System 2.2 The Evolution of Operating Systems Serial Processing Simple Batch Systems Multiprogrammed Batch Systems Time-Sharing Systems 2.3 Major Achievements The Process Memory Management Information Protection and Security Scheduling and Resource Management System Structure 2.4 Developments Leading to Modern Operating Systems 2.5 Microsoft Windows Overview History Single-User Multitasking Architecture Client/Server Model Threads and SMP Windows Objects 2.6 Traditional UNIX Systems History Description 2.7 Modern UNIX Systems System V Release 4 (SVR4) BSD Solaris 10 2.8 Linux History Modular Structure Kernel Components 2.9 Recommended Reading and Web Sites 2.10 Key Terms, Review Questions, and Problems 50 M02_STAL6329_06_SE_C02.QXD 2/28/08 3:33 AM Page 50
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2.1 / OPERATING SYSTEM OBJECTIVES AND FUNCTIONS 51 We begin our study of operating systems (OSs) with a brief history.This history is it- self interesting and also serves the purpose of providing an overview of OS princi- ples. The first section examines the objectives and functions of operating systems. Then we look at how operating systems have evolved from primitive batch systems to sophisticated multitasking, multiuser systems.The remainder of the chapter looks at the history and general characteristics of the two operating systems that serve as examples throughout this book. All of the material in this chapter is covered in greater depth later in the book. 2.1 OPERATING SYSTEM OBJECTIVES AND FUNCTIONS An OS is a program that controls the execution of application programs and acts as an interface between applications and the computer hardware. It can be thought of as having three objectives: Convenience: An OS makes a computer more convenient to use. Efficiency: An OS allows the computer system resources to be used in an ef- ficient manner. Ability to evolve: An OS should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions with- out interfering with service. Let us examine these three aspects of an OS in turn. The Operating System as a User/Computer Interface The hardware and software used in providing applications to a user can be viewed in a layered or hierarchical fashion, as depicted in Figure 2.1.The user of those applica- tions, the end user, generally is not concerned with the details of computer hardware. Thus, the end user views a computer system in terms of a set of applications. An ap- plication can be expressed in a programming language and is developed by an appli- cation programmer. If one were to develop an application program as a set of machine instructions that is completely responsible for controlling the computer hardware, one would be faced with an overwhelmingly complex undertaking.To ease this chore, a set of system programs is provided. Some of these programs are referred
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