Chapter 6Chapter 6 System SoftwareSystem Software

6.1Introduction of Operating System 6.2Functions of OS 6.3More About OS 6.4Device Drive 6.5Utility Software

6.16.1 Introduction of Operating SystemIntroduction of Operating SystemOperating system (OS)

organise and control the resources of the PC

shield users from the underlying complex operations

Layered software architecture

6.16.1 Introduction of Operating SystemIntroduction of Operating SystemBIOS: lowest layer of software that exercises direct control over hardware

OS works between the applications and BIOS.

Standard interface is established between layers.

Each layer provides services and functions for the above layers.

6.26.2 Functions of OSFunctions of OSProcess management

Provide supervisory calls for managing processes

Administer the allocation of system resources between processes

6.26.2 Functions of OSFunctions of OSMemory management

Manage the allocation of memory among processes

Control the memory management hardware

Ensure that each process has enough memory to execute

6.26.2 Functions of OSFunctions of OSFile system management

A collection of file system objects are organised

Formatting and copying disks

Displaying lists of files

Checking the amount of used and free space

Copying, renaming, deleting, moving and sorting files

6.26.2 Functions of OSFunctions of OSDevice management

share input and output devices among the processes requesting them

6.26.2 Functions of OSFunctions of OSUser interface

Users should know how to operate the user interface

DOS: command-line driven OS

Graphical User Interface (GUI)input commands by pointing at and clicking menus and icons on screen

more user-friendly than text commands

enrich user interaction by incorporating multimedia features

6.36.3 More About OSMore About OSType of OS

Single-user, single-task

Single-user, multi-task

Multi-user

Multiprocessing

Real-Time Operating System (RTOS)

6.36.3 More About OSMore About OSSingle-user, single-task OS

enable one user to do one thing at a time effectively

e.g. DOS, Palm OS

Single-user, multi-task OSallow a single user operate several programs at the same time

commonly used in desktop and laptop computer

e.g. Windows XP

6.36.3 More About OSMore About OSMulti-user OS

allow many users to use computer’s resources simultaneously

e.g. mainframe and supercomputers

Multiprocessing OSsupport two or more CPUs running programs at the same time

6.36.3 More About OSMore About OSReal-Time Operating System

support the execution of tasks within rigid time constraints

e.g. industrial control systems, weapon systems

6.36.3 More About OSMore About OS

Linuxefficient Unix-like OS

provide PC users a free or low-cost OS

strong inherent networking power

6.36.3 More About OSMore About OSLinux

adequate server capabilities for Web, FTP and email

publicly open and is expanded by contributors

low demand on hardware resources

availability of many free applications

6.36.3 More About OSMore About OS

Evolution of OS for home PC

DOSsingle user, single task system

command-line driven OS

6.36.3 More About OSMore About OS

Evolution of OS for home PC

Windows 3.XGUI operating environments

need DOS to run

6.36.3 More About OSMore About OSEvolution of OS for home PC

Windows 95multitasking OS

improved graphical interface

support networking, plug and play technology, long filenames

contain tools to access the Internet

6.36.3 More About OSMore About OSEvolution of OS for home PC

Windows 98upgraded version of Windows 95

incorporate Microsoft Internet Explorer into the OS

provide better Internet and multimedia support

6.36.3 More About OSMore About OSEvolution of OS for home PC

Windows MEupdated version of Windows 98

rich set of multimedia and entertainment support

6.36.3 More About OSMore About OSEvolution of OS for home PC

Windows XP Home Edition

latest Windows OS for home user

more intuitive visual design

advanced digital media features, firewall utility and remote support

6.46.4 Device DriversDevice DriversDevice driver

control a particular type of device attached to the computer

convert I/O instructions of OS to messages understood by device type

examples: printer, video adapters, CD-ROM drives and disk drives

device driver layer: hide the differences among I/O controllers from the OS

closely linked to the device controller

6.46.4 Device DriversDevice Drivers

Installing a device driver

6.56.5 Utility SoftwareUtility SoftwareUtility software

a program that provides an add-on to the functions provided by the OS

make the computer easier and more reliable

not essential

e.g. virus protection, firewalls, disk repair / recovery

6.56.5 Utility SoftwareUtility SoftwareComputer virus

programming code that causes unexpected and undesirable events

transmitted through email attachments, downloads, disk or CD

virus creator embeds codes into a program

virus activates and attaches itself to other programs

some are annoying spanks

some destroy data or hard disk, corrupt programs

6.56.5 Utility SoftwareUtility SoftwareTypes of viruses

System or boot-record viruses

File infector viruses

Macro viruses

Trojan horse

6.56.5 Utility SoftwareUtility SoftwareSystem or boot-record viruses

infect executable code found in disk

attach to the DOS boot sector on disks or Master Boot Record of hard disk

File infector virusesSome attach to program files (.COM or .EXE files)

Some infect any program for which execution is requested

Some appear as wholly-contained programs or scripts

6.56.5 Utility SoftwareUtility SoftwareMacro viruses

hidden within documents or data

unleashed when the macro is run

infect MS Word applications

Trojan horseharmful code is embedded in seemingly harmless programs or data

get control of system and do specified damages

6.56.5 Utility SoftwareUtility SoftwareAnti-virus programs

screen e-mail attachmentscan the whole systemidentify and remove the virus found in memory, storage media or incoming filesidentify a virus by finding its virus signatureSigns of viruses

Unusual messages on screenDecrease system performanceMissing dataInability to access the hard drive

6.56.5 Utility SoftwareUtility Software

McAfee VirusScan

6.56.5 Utility SoftwareUtility SoftwareAnti-virus programs

Infected file is either removed or quarantined.Latest virus definitions should be obtained.Online anti-virus utility: protect PC connected to the Internet permanently

automatically check for virus definition updates and software updates

Delete the email with suspected infection

6.56.5 Utility SoftwareUtility SoftwareFirewall

A set of related programs protect the resources of a private network from other networksinstalled in network gateway serverwork with a router program

determine each network packet whether forward it to its destination

work with a proxy serverdetermine whether a data packet should be allowed to pass through the wall

6.56.5 Utility SoftwareUtility SoftwarePacket filtering firewall

based on the addressing information found in individual packetscompare the addressing information with its programmed security policy

Stateful inspection firewallextend the packet-by-packet filtering process to include multi-packet flowshas the intelligence to track individual flows

6.56.5 Utility SoftwareUtility SoftwareProxy Server

a gateway between the protected network and the Internetprevent packets from travelling directly between the Internet and protected network

6.56.5 Utility SoftwareUtility SoftwareDisk cleanup utility

delete unwanted fileimprove the performance of computers

6.56.5 Utility SoftwareUtility SoftwareDisk scan

detect and correct physical and logical errors on hard disks and floppy diskssearch for and remove unwanted filesTypes of errors:

cross-link files: two or more files share the same portion of the hard disklost file fragment: separate fragments of a larger fileinvalid file information: incorrect information about file names, data and time

6.56.5 Utility SoftwareUtility SoftwareDisk defragmenter

rearrange files, programs and unused space on hard diskincrease the speed of OS and programs

6.56.5 Utility SoftwareUtility SoftwareHow disk defragmenter is formed?

F3 is deleted and space is left.

F5 with 3 clusters is split into two portion

Each file is stored as a linked list of cluster in hard disk

6.56.5 Utility SoftwareUtility SoftwareEfficiency of hard disk decreases with the number of fragmented filesDisk defragmenter in Windows

rearrange the fragmented files and unused spacehelp restore the efficiencyimprove the access time

6.56.5 Utility SoftwareUtility Software

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