Understanding the Role and Services of an Operating System: A Comprehensive Overview, Slides of Computer Science

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1

Operating System

• A program that controls the execution of

application programs

• An interface between applications and

hardware

2

Operating System Objectives

• Convenience
  • Makes the computer more convenient to use
• Efficiency
  • Allows computer system resources to be used in an efficient manner
• Ability to evolve
  • Permit effective development, testing, and introduction of new system functions without interfering with service

4

Services Provided by the

Operating System

• Program development
  • Editors and debuggers
• Program execution
• Access to I/O devices
• Controlled access to files
• System access

5

Services Provided by the

Operating System

• Error detection and response
  • Internal and external hardware errors
    • Memory error
    • Device failure
  • Software errors
    • Arithmetic overflow
    • Access forbidden memory locations
  • Operating system cannot grant request of application

7

Operating System

• Responsible for managing resources
• Functions same way as ordinary

computer software

• It is program that is executed
• Operating system relinquishes control of

the processor

8

M emory

Computer System I /O Devices OperatingSystem Software

Programsand Data

Processor Processor

ProgramsOS Data

Storage

I /O Controller

I /O Controller

Printers,keyboards, digital camera,etc.

I /O Controller

Figure 2.2 The Operating System as Resource M anager

10

Evolution of an Operating System

• Hardware upgrades plus new types of

hardware

• New services
• Fixes

11

Evolution of Operating

Systems

• Serial Processing
  • No operating system
  • Machines run from a console with display lights, toggle switches, input device, and printer
  • Schedule time
  • Setup included loading the compiler, source program, saving compiled program, and loading and linking

13

Job Control Language (JCL)

• Special type of programming language
• Provides instruction to the monitor
  • What compiler to use
  • What data to use

14

Hardware Features

• Memory protection
  • Do not allow the memory area containing the monitor to be altered
• Timer
  • Prevents a job from monopolizing the system

16

Memory Protection

• User program executes in user mode
  • Certain instructions may not be executed
• Monitor executes in system mode
  • Kernel mode
  • Privileged instructions are executed
  • Protected areas of memory may be accessed

17

I/O Devices Slow

19

Multiprogramming

• When one job needs to wait for I/O, the processor can switch to the other job

20

Multiprogramming