Lecture 8: 9/19/2002 CS149D Fall 2002 1

CS149D Elements of Computer Science

Ayman Abdel-Hamid

Department of Computer Science

Old Dominion University

Lecture 8: 9/19/2002

Lecture 8: 9/19/2002 CS149D Fall 2002 2

Outline•Wrap up Chapter 2

•Problems 2.10, 2.20

•How CPU and memory communicates with other devices

•Chapter 3 Operating Systems and Networks

•Evolution of Operating Systems

•Operating System Architecture

Should cover sections 3.1 and 3.2

Lecture 8: 9/19/2002 CS149D Fall 2002 3

Communication with Other devices

Fig. 2.8 on page 100

Copyright © 2003 Pearson Education, Inc.

Lecture 8: 9/19/2002 CS149D Fall 2002 4

Evolution of Operating Systems•An operating System (OS) controls and coordinates usage of a machine’s resources (CPU, memory, disks, …)

•Single-processor machines in 1940s and 1950s

•Significant preparation of equipment to run a program

•Execution of a program job

•Separation of users and equipments (introduction of computer operator concept)

•Submit program to operator to run, along with any required data and special directions

•Operator loads program materials into machine’s mass storage

•Batch processing

Lecture 8: 9/19/2002 CS149D Fall 2002 5

Batch Processing

Copyright © 2003 Pearson Education, Inc.

No interaction with the program once submitted

Lecture 8: 9/19/2002 CS149D Fall 2002 6

Interactive Processing

What happens when you have multiple users?

Time-sharing solution (time slices)

(In single-user systems usually called multitasking)

Copyright © 2003 Pearson Education, Inc.

Lecture 8: 9/19/2002 CS149D Fall 2002 7

Software Classification

Copyright © 2003 Pearson Education, Inc.

Application: spreadsheets, games, program development software

Utility: utility to format a disk, copy a file, utility to handle network communication

Lecture 8: 9/19/2002 CS149D Fall 2002 8

Operating System Components

Copyright © 2003 Pearson Education, Inc.

Shell: interface between users and operating system.

Modern computers have a GUI shell (Graphical User Interface)

Window manager: component within the GUI shell

Kernel: internal part of an OS

Lecture 8: 9/19/2002 CS149D Fall 2002 9

OS Kernel Software Components

File Manager

Coordinate use of machine’s mass storage

Device drivers

Control operation of machine’s peripheral devices (printer, disk drive, monitor, …)

Memory Manager

Coordinate machine’s use of main memory

Scheduler

Which activity is executed next

Dispatcher

Controls allocation of time slices to activities

Lecture 8: 9/19/2002 CS149D Fall 2002 10

Boot Strapping an OS

Copyright © 2003 Pearson Education, Inc.