Chapter 6System Software  6.1Introduction of Operating System 6.1Introduction of Operating System 6.1Introduction of Operating System  6.2Functions of OS 6.2Functions of OS 6.2Functions of OS  6.3More About OS 6.3More About OS 6.3More About OS  6.4Device Drive 6.4Device Drive 6.4Device Drive  6.5Utility Software 6.5Utility Software 6.5Utility Software

6.1Introduction of Operating System Operating system (OS) organise and control the resources of the PC shield users from the underlying complex operations Layered software architecture

6.1Introduction of Operating System BIOS: 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.

6.2Functions of OS Process management Provide supervisory calls for managing processes Administer the allocation of system resources between processes

6.2Functions of OS Memory management Manage the allocation of memory among processes Control the memory management hardware Ensure that each process has enough memory to execute

6.2Functions of OS File 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

6.2Functions of OS Device management share input and output devices among the processes requesting them

6.2Functions of OS User 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

6.3More About OS Type of OS Single-user, single-task Single-user, multi-task Multi-user Multiprocessing Real-Time Operating System (RTOS)

6.3More About OS Single-user, single-task OS enable one user to do one thing at a time effectively e.g. DOS, Palm OS Single-user, multi-task OS allow a single user operate several programs at the same time commonly used in desktop and laptop computer e.g. Windows XP

6.3More About OS Multi-user OS allow many users to use computer’s resources simultaneously e.g. mainframe and supercomputers Multiprocessing OS support two or more CPUs running programs at the same time

6.3More About OS Real-Time Operating System support the execution of tasks within rigid time constraints e.g. industrial control systems, weapon systems

6.3More About OS Linux efficient Unix-like OS provide PC users a free or low-cost OS strong inherent networking power

6.3More About OS Linux adequate server capabilities for Web, FTP and publicly open and is expanded by contributors low demand on hardware resources availability of many free applications

6.3More About OS Evolution of OS for home PC DOS single user, single task system command-line driven OS

6.3More About OS Evolution of OS for home PC Windows 3.X GUI operating environments need DOS to run

6.3More About OS Evolution of OS for home PC Windows 95 multitasking OS improved graphical interface support networking, plug and play technology, long filenames contain tools to access the Internet

6.3More About OS Evolution of OS for home PC Windows 98 upgraded version of Windows 95 incorporate Microsoft Internet Explorer into the OS provide better Internet and multimedia support

6.3More About OS Evolution of OS for home PC Windows ME updated version of Windows 98 rich set of multimedia and entertainment support

6.3More About OS Evolution 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

6.4Device Drivers Device 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

6.4Device Drivers Installing a device driver

6.5Utility Software Utility 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

6.5Utility Software Computer virus programming code that causes unexpected and undesirable events transmitted through 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

6.5Utility Software Types of viruses System or boot-record viruses File infector viruses Macro viruses Trojan horse

6.5Utility Software System 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 viruses Some 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

6.5Utility Software Macro viruses hidden within documents or data unleashed when the macro is run infect MS Word applications Trojan horse harmful code is embedded in seemingly harmless programs or data get control of system and do specified damages

6.5Utility Software Anti-virus programs screen attachment scan the whole system identify and remove the virus found in memory, storage media or incoming files identify a virus by finding its virus signature Signs of viruses Unusual messages on screen Decrease system performance Missing data Inability to access the hard drive

6.5Utility Software McAfee VirusScan

6.5Utility Software Anti-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 with suspected infection

6.5Utility Software Firewall A set of related programs protect the resources of a private network from other networks installed in network gateway server work with a router program determine each network packet whether forward it to its destination work with a proxy server determine whether a data packet should be allowed to pass through the wall

6.5Utility Software Packet filtering firewall based on the addressing information found in individual packets compare the addressing information with its programmed security policy Stateful inspection firewall extend the packet-by-packet filtering process to include multi-packet flows has the intelligence to track individual flows

6.5Utility Software Proxy Server a gateway between the protected network and the Internet prevent packets from travelling directly between the Internet and protected network

6.5Utility Software Disk cleanup utility delete unwanted file improve the performance of computers

6.5Utility Software Disk scan detect and correct physical and logical errors on hard disks and floppy disks search for and remove unwanted files Types of errors: cross-link files: two or more files share the same portion of the hard disk lost file fragment: separate fragments of a larger file invalid file information: incorrect information about file names, data and time

6.5Utility Software Disk defragmenter rearrange files, programs and unused space on hard disk increase the speed of OS and programs

6.5Utility Software How 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

6.5Utility Software Efficiency of hard disk decreases with the number of fragmented files Disk defragmenter in Windows rearrange the fragmented files and unused space help restore the efficiency improve the access time

6.5Utility Software

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