Transcript What is an operating system?

SAK3002 – IT and Its Applications
3
Chapter
COMPUTER
SOFTWARE
Chapter 3
SAK3002 – Information Technology and Its Application
SAK3002 – IT and Its Applications
Objectives of this chapter:
You can…
Identify the types of system software
Describe the functions of an operating system
Identify the types of operating system
Identify utility programs
Explain the purpose of the utilities program
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SAK3002 – IT and Its Applications
Overview
This chapter covers
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System Software
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Chapter 3
Operating System
Utility Program
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SAK3002 – IT and Its Applications
Introduction
Computer software is:
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A group of programs that connects user with
computer devices
Comprised of a sequence of instructions
Designed to instruct the computer to execute desired
functions by the users
SAK3002 – Information Technology and Its Application
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Introduction (cont’d)
Software Layers
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System Software
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What is system software?
Programs that
maintain operation
of computer
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Two categories
Operating Systems
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Utility Programs
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3.1 Operating System
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Operating System
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What is an operating system?
 A group of programs that organize and manage the
whole computer operations
 OS is a set of instructions that coordinate all the
internal activities among computer hardware,
application programs and users
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Operating System (cont’d)
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OS is controlled by the kernel.
What is a kernel?
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Kernel is the supervisor program that manage the
memory and devices
Kernel is loaded into the memory from the hard disk
(or other storage) during booting until computer is
turned off
It is known as memory resident (because it resides in
memory as long as the power is on. Non-resident are
other programs that resides in hard disk at the same
time)
SAK3002 – Information Technology and Its Application
SAK3002 – IT and Its Applications
Operating System (cont’d)
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The functions of an operating system
start the computer
(Booting)
manage programs
provide a user interface
administer
security
manage
memory
control a
network
provide file
management and other
utilities
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monitor
performance
establish an
Internet connection
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schedule jobs and
configure devices
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Operating System (cont’d)
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Booting
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Process of starting or restarting a computer
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Cold boot
Turning on
computer that has
been powered off
Warm boot
Restarting
computer that is
powered on
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Operating System (cont’d)
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A personal computer boot up process
Step 1. Power supply
Step 4. Results of POST are
sends signal to components in system unit
compared with data in CMOS chip
Step 2. Processor
on a USB drive, in floppy disk drive
or CD/DVD drive, and then hard
disk
Step 6. Kernel (core) of operating
system loads into RAM
accesses BIOS to start
computer
Step 3. BIOS runs tests,
called the POST, to
check components such
as mouse, keyboard,
and adapter cards
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Step 5. BIOS looks for system files
Step 7. Operating system loads
configuration information and
displays desktop on screen
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Operating System (cont’d)
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main functions of OS:
 Manage
computer programs
 Manage computer hardware
 Provides user interface
 Support application software
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Operating System (cont’d)
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Manage computer programs
Managing programs refers to how many users,
and how many programs, an operating system
can support at one time
 An OS can be single tasking, multi-tasking,
cooperative multi-tasking, preemptive multitasking, multithreading and multiprocessing
 Single tasking
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 Runs
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only one program at a time
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Operating System (cont’d)
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Multi-tasking
 Same
concept as multiprogramming
 Allows 2 or more programs at the same time
 Divide the programs into active and inactive. Active
application is called foreground application and
inactive application is background application
 CPU does not run the programs simultaneously but
manage the resources i.e. memory based on
active/inactive applications
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Operating System (cont’d)
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Cooperative Multi-tasking
 Based
on multi-tasking concept, whereby
foreground application controls CPU until program
ends
 But if program crashes/hang, OS needs to be
rebooted
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Preemptive Multi-tasking
 Based
on multi-tasking concept
 But if program crashes/hang, OS is able to take
over CPU so other programs can be maintained
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Operating System (cont’d)
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Multithreading
 One
program may execute more than one task
 Example print and edit at the same time
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Multiprocessing
 Use
of 2 or more processor at the same time
 Programs run simultaneously
 Each processor manage own resources
 Hardware dependant esp. motherboard
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Operating System (cont’d)
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Manage computer hardware
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Memory Unit
 OS
partitions the memory for each program.
 If memory is insufficient, OS may use virtual
memory, which allocates a portion of a storage
medium to function as additional RAM
 In virtual memory, programs/instructions are
stored in fixed-sized unit called pages
 If memory if full, OS will copy pages into swap file
in hard disk and reloaded into memory when
needed
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Operating System (cont’d)
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With virtual memory (VM), portion of hard disk is
allocated to function as RAM
Step 1. The
operating system
transfers the least
recently used data
and program
instructions to disk
because RAM is
needed for other
functions.
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Step 2. The
operating system
transfers data and
program instructions
from hard disk to
RAM when they are
needed.
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Operating System (cont’d)
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Input/Output Devices
 OS
provides interrupt handler, a mini program to
handle interrupt from input/output devices.
 Examples of interrupt are mouse
click/scroll/keyboard punch
 OS requires device driver to operates hardware
devices. Drivers are loaded during booting
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Operating System (cont’d)
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What is a device driver?
Program that
tells operating system
how to communicate
with device
Also called driver
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Device
Driver
With Plug and Play,
operating system
automatically configures
new devices as you
install them
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Operating System (cont’d)
Spooling
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Sending print jobs to buffer instead of directly to printer
Print jobs line up in queue
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Operating System (cont’d)
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Provides User Interface
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i.
OS manages communication between the
computers and users
Users may login, run application programs,
manage files (copy/save) and on/off computers
using any type of interface
There are 3 types of command instructions:
Command line
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Instructions to be typed in i.e. to save a file into diskette
is C:\WINDOWS>copy C:myfile.doc a:
Users have to memorize instructions
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Operating System (cont’d)
ii.
Menu-driven
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iii.
Graphical user interface (GUI)
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User selects instruction from a text-based pull-down
menu
Instructions are entered either via mouse click/
keyboard <ENTER> of arrow keys
User selects instruction by mouse click or keyboard
<ENTER> icons
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Operating System (cont’d)
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User interface
Controls how you enter data and instructions and how information
displays on screen
command-line interface
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menu-driven interface
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Operating System (cont’d)
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Graphical User Interface (GUI)
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User interacts with
menus and visual
images such as icons
and buttons
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Some characteristics of operating systems
Devicedependent
Runs only on
specific type of
computer
Proprietary
software
Privately owned and
limited to specific vendor
or computer model
Downward
compatible
Works with application
software written for
earlier version of
operating system
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Deviceindependent
Runs on many
manufacturers’
computers
Upward
compatible
Runs on new versions
of operating system
SAK3002 – Information Technology and Its Application
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Three categories of operating systems
Embedded
Network
Stand-alone
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Operating System (cont’d)
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Stand-alone
operating systems
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Example: Windows
Windows 7 was released in?
Windows Version
Year Released
Windows 3.x
1990
Windows NT 3.1
1993
Windows 95
1995
Windows NT Workstation 4.0
1996
Windows 98
1998
Windows Millennium Edition
2000
Windows 2000 Professional
2000
Windows XP
2001
Windows XP SP2
2004
Windows Vista
2006
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Stand-Alone Operating Systems
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Windows XP
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Fast, reliable Windows
operating system
Available in five editions:
Home Edition, Professional
Edition,
Tablet PC Edition,
Media Center Edition,
and 64-bit Edition
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Stand-Alone Operating Systems
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Windows Vista
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Successor to Windows XP,
containing a new interface
and new / enhanced features
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Available in several editions,
grouped into Home and
Business categories
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Stand-Alone Operating Systems
Mac OS X
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Available only for
computers manufactured
by Apple
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Macintosh operating
system has been
model for most GUIs
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Stand-Alone Operating Systems
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UNIX
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Used by power users
because of its flexibility
and power
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Most versions
offer GUI
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Available for
computers of all
sizes
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Stand-Alone Operating Systems
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Linux
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Popular, free, multitasking
UNIX-type operating system
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Open-source software—
code is available to
public
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Both a stand-alone
and a network
operating system
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Red Hat provides a version of Linux called Red Hat
Enterprise Linux.
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Operating System (cont’d)
Network operating system
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Allows users to share printer,
Internet access, files, and
programs on a network
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Administers security
by establishing user name and
password for each user
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Network Operating Systems
NetWare
Examples of network
operating systems
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Designed for
client/server
networks
Windows
Server 2003
UNIX / Linux
Upgrade to Windows
2000 Server
Multi-purpose
operating system
Solaris
 Version of UNIX
developed by Sun
Microsystems
 Specifically for
e-commerce
applications
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Embedded Operating Systems
 Embedded operating system
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Found on most mobile computers,
PDAs, and other small devices
Windows CE is
scaled-down version of Windows
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Embedded Operating Systems
Operating systems for PDAs
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Windows Mobile for Pocket PC
Palm OS for Palm
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Embedded Operating Systems
Embedded Linux
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Scaled-down Linux operating system
designed for PDAs, smart phones,
smart watches, set-top boxes,
Internet telephones, and other
devices
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Embedded Operating Systems
Symbian OS
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Open-source, multitasking operating system
designed for smart phones
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Make telephone calls,
save appointments,
browse Web, send
and receive e-mail
and faxes, and more
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3.2 Utility Program
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Utility program
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A small program that provides an addition to the
capabilities provided by the operating system
Performs maintenance-type tasks, usually related
to managing a computer, its devices, or its
programs.
SAK3002 – Information Technology and Its Application
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OS Utility Program
File manager
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Performs functions
such as copying,
renaming, deleting,
and moving files
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Image viewer displays
contents of graphics
file when you double
click on it
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OS Utility Program
Personal firewall
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Detects and protects a
personal computer from
unauthorized intrusions
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The latest update to
Windows XP
automatically enables
the built-in personal
firewall upon
installation
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OS Utility Program
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Uninstaller
Removes a
program and
all associated files
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In Windows XP,
uninstaller is in Add/Remove
Programs in Control Panel
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OS Utility Program
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Disk scanner
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Detects and corrects
problems on hard disk
Searches for and removes
unnecessary files
SAK3002 – Information Technology and Its Application
SAK3002 – IT and Its Applications
OS Utility Program
fragmented disk
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Disk defragmenter
Reorganizes files and
unused space on hard
disk so programs run
faster
disk after
defragmentation
process
Chapter 3
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OS Utility Program
Diagnostic utility
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Compiles technical information about
hardware and some software
Prepares report outlining problems
SAK3002 – Information Technology and Its Application
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OS Utility Program
Backup utility
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Copies selected files or
entire hard disk onto
another storage medium
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Most compress files
during backup to require
less storage space
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OS Utility Program
Screen saver
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Causes monitor’s screen to
display moving image or
blank screen if there is no
activity for a specified time
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To secure computer, user
configures screen saver to
require password to
deactivate
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Stand-Alone Utility Programs
Antivirus program
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Identifies and removes viruses
in memory, storage media, and
incoming files
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Must be updated frequently
Chapter 3
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Stand-Alone Utility Programs
What is a virus?
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Potentially damaging computer program
Affects computer without user’s knowledge
SIGNS OF
VIRUS
INFECTION
Chapter 3
• An unusual message or image is displayed on the
computer screen
• An unusual sound or music plays randomly
• The available memory is less than what should be
available
• A program or file suddenly is missing
• An unknown program or file mysteriously appears
• The size of a file changes without explanation
• A file becomes corrupted
• A program or file does not work properly
• System properties change
SAK3002 – Information Technology and Its Application
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Stand-Alone Utility Programs
Spyware
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Program placed on a computer without the user’s knowledge that
secretly collects information about the user
Often enters a computer as a result of a user installing a new program
A spyware remover is a program that detects and deletes spyware
SAK3002 – Information Technology and Its Application
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Stand-Alone Utility Programs
Internet filters
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Programs that remove or block certain items from
being displayed
Anti-Spam
Programs
Web
Filters
Pop-up
Blockers
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Stand-Alone Utility Programs
File compression utility
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Shrinks size of files to free up room and improve
performance
Compressed files are sometimes called zipped
files
Two popular utilities:
Winrar and WinZip
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Stand-Alone Utility Programs
CD/DVD burning software
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Writes text, graphics, audio,
and video files to a recordable
or rewriteable CD or DVD
SAK3002 – Information Technology and Its Application
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Stand-Alone Utility Programs
Personal computer maintenance utility
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Identifies and fixes operating
system problems and disk
problems
Some continuously
monitor computer to
identify problems
before they occur
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End of Chapter 3
Chapter 3
SAK3002 – Information Technology and Its Application