Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press Computer Systems and Networks Chapter 8: Aspects of the operating system

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press Explain the need and function of ROM based BIOS; Identify and describe the functions of an Operating System; Describe the role of device drivers; Describe the operation of a multi-tasking technique; Outline the operation of virtual memory. Learning Objectives:

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press BIOS in relation to the computer software and hardware

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press The use of the reset vector

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press Some of the main tasks of an operating system 1.To receive input from the user (e.g. commands and data). 2.To act on commands provided by the user. 3.To provide output to the user. 4.To create environments in which a user program can execute. 5.To manage the file system (including the directory structure). 6.To enable programs to share resources and thereby support ‘multi-tasking’. 7.To provide resources for a user program via special instructions – often referred to as ‘system calls’. 8.To interface with hardware such as the keyboard, display screen, printers, hard disk drives, etc. Often such interfaces are implemented using programs called ‘device drivers’. 9.To provide security (e.g. password protection, the protection of files belonging to each user, etc). 10.To provide network communications and thereby allow computers to communicate. 11.To provide a convenient user interface (using, for example menus, icons, etc). 12.The provision of text editing facilities. 13.The provision of various utilities that may be accessed by a user such as ‘system tools’, ‘calculator’, ‘calendar’, etc. 14.The provision of back-up facilities.

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press The operating system provides resources to a user’s program

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press In this model, the process encapsulates a program and manages all communication.

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press Memory layout for a simple batch system

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press The simple multi-programming approach

Use with Computer Systems and Networks by Blundell, Khan, Lasebae and Jabbar ISBN © 2007 Middlesex University Press The use of a ‘device driver’ to communicate and interact with hardware systems.