chapter 6system software 6.1introduction of operating system 6.1introduction of operating system...
TRANSCRIPT
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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
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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
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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.
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6.26.2 Functions of OSFunctions of OSProcess management
Provide supervisory calls for managing processes
Administer the allocation of system resources between processes
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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
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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
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6.26.2 Functions of OSFunctions of OSDevice management
share input and output devices among the processes requesting them
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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
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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)
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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
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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
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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
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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
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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
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6.36.3 More About OSMore About OS
Evolution of OS for home PC
DOSsingle user, single task system
command-line driven OS
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6.36.3 More About OSMore About OS
Evolution of OS for home PC
Windows 3.XGUI operating environments
need DOS to run
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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
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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
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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
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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
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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
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6.46.4 Device DriversDevice Drivers
Installing a device driver
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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
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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
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6.56.5 Utility SoftwareUtility SoftwareTypes of viruses
System or boot-record viruses
File infector viruses
Macro viruses
Trojan horse
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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
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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
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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
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6.56.5 Utility SoftwareUtility Software
McAfee VirusScan
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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
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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
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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
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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
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6.56.5 Utility SoftwareUtility SoftwareDisk cleanup utility
delete unwanted fileimprove the performance of computers
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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
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6.56.5 Utility SoftwareUtility SoftwareDisk defragmenter
rearrange files, programs and unused space on hard diskincrease the speed of OS and programs
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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
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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
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6.56.5 Utility SoftwareUtility Software
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