1. technology and computing
2. hardware
3. computer

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Student
Workbook
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Unit 2783 (V6)
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Demonstrate knowledge of
the components of
personal computer systems
 Easy to follow
 Step-by-step instructions
 Covers Unit Standard Criteria
A Cheryl Price Publication
Unit Standard 2783 (Version 6)
Demonstrate knowledge of the components of personal computer systems
This book covers the course outline for the following New Zealand Qualifications Authority Unit Standard:
Unit Standard 2783 -
GENERIC COMPUTING (Level 3, Credit 3)
Demonstrate knowledge of the components of personal computer systems
(Version 6)
All topics in this Unit Standard are included in the Student Workbook.
Cheryl Price
T.Dip.WP, T.Dip.T.
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Product Code: USB2783v6SW-0213
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© Cherylprice.co.nz Limited, February 2013
Disclaimer
PO Box 187
Matakana
Auckland 0948
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All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means,
electronic or mechanical, including photocopying, scanning, recording, or any information storage and retrieval system,
without permission in writing from Cherylprice.co.nz Limited. No patent liability is assumed with respect to the use of
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and authors assume no responsibility for errors or omissions. Neither is any liability assumed for damages resulting
from the use of the information contained herein.
Web address:
www.cherylprice.co.nz
Published in New Zealand
Phone: (09) 422 7230
Mobile: 021 715566
Fax:
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Table of Contents
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Data versus Information ................................................................................................................... 1
Digital versus Analogue ................................................................................................................... 2
Bits and Bytes .............................................................................................................................. 3
Counting with Binary Numbers ................................................................................................... 3
ASCII ........................................................................................................................................... 4
Unicode ........................................................................................................................................ 4
Kilobytes, Megabytes, Gigabytes . . . and Terabytes................................................................... 5
The Processing Cycle ....................................................................................................................... 5
Input ............................................................................................................................................. 5
Processing .................................................................................................................................... 5
Storage ......................................................................................................................................... 6
Output .......................................................................................................................................... 6
What are Peripherals? ...................................................................................................................... 7
Input Devices ................................................................................................................................... 7
Keyboard...................................................................................................................................... 7
Standard keyboard ................................................................................................................... 7
Natural keyboard (split or angled keyboard) ........................................................................... 7
Multimedia keyboard ............................................................................................................... 8
Mouse .......................................................................................................................................... 8
Traditional trackball mouse ..................................................................................................... 8
Optical mouse .......................................................................................................................... 8
Wireless mouse ........................................................................................................................ 9
Trackball ...................................................................................................................................... 9
Touchscreen ................................................................................................................................. 9
Scanner ...................................................................................................................................... 10
Flatbed scanners .................................................................................................................... 10
Handheld scanners ................................................................................................................. 10
Scanner/printer/copier ........................................................................................................... 10
Microphone ................................................................................................................................ 11
Storage Devices ............................................................................................................................. 11
Reading and Writing .................................................................................................................. 11
The Hard Drive .......................................................................................................................... 12
Hard Drive construction ........................................................................................................ 12
External and removable hard drives ...................................................................................... 12
USB/Portable hard drives ...................................................................................................... 13
Floppy Disks .............................................................................................................................. 13
Form and capacity ................................................................................................................. 13
Formatting and Write Protecting ........................................................................................... 13
Floppies' many uses ............................................................................................................... 14
Optical Discs .............................................................................................................................. 14
Compact Discs ....................................................................................................................... 14
Writable compact discs .......................................................................................................... 15
DVDs ......................................................................................................................................... 15
Writable DVDs ...................................................................................................................... 15
Combination Disc Readers/Writers ....................................................................................... 16
Disc speeds ............................................................................................................................ 16
Blu-ray Discs ............................................................................................................................. 16
Tape ........................................................................................................................................... 16
Backup ........................................................................................................................................... 17
Compression and encryption ................................................................................................. 17
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Types of backup..................................................................................................................... 18
Output Devices............................................................................................................................... 18
The Monitor ............................................................................................................................... 18
LCD monitors ........................................................................................................................ 19
CRT monitors ........................................................................................................................ 19
Monitor facts .............................................................................................................................. 20
Refresh rate ............................................................................................................................ 20
Pixels and Dot pitch ............................................................................................................... 20
Display Resolution ................................................................................................................ 20
Monitor standards .................................................................................................................. 21
Colour Depth/Bit Depth ............................................................................................................. 22
The Graphics Card ..................................................................................................................... 22
Onboard Video........................................................................................................................... 23
3D Graphics ............................................................................................................................... 23
Sound ......................................................................................................................................... 23
Sound card ............................................................................................................................. 23
Standards ............................................................................................................................... 24
Speakers/Headphones ............................................................................................................ 24
Printers ........................................................................................................................................... 24
Laser Printers ......................................................................................................................... 24
Ink-Jet Printers....................................................................................................................... 25
Dot Matrix Printers ................................................................................................................ 25
Fonts ...................................................................................................................................... 25
Resolution .............................................................................................................................. 26
Screen Resolution .................................................................................................................. 26
Printer Resolution .................................................................................................................. 26
Unprintable Region................................................................................................................ 26
Memory ................................................................................................................................. 27
Communication – The Modem ...................................................................................................... 27
Dialup Modems.......................................................................................................................... 27
Broadband Modems ................................................................................................................... 28
Digital Subscriber Line modems ........................................................................................... 28
Cable modems ....................................................................................................................... 28
Modem Types ............................................................................................................................ 28
Networking .................................................................................................................................... 29
Networking Hardware................................................................................................................ 30
Hub ........................................................................................................................................ 30
Bridge .................................................................................................................................... 31
Switch .................................................................................................................................... 31
Router .................................................................................................................................... 31
Network Interface Card ......................................................................................................... 31
P2P and Client/Server Networks ............................................................................................... 32
Peer-To-Peer .......................................................................................................................... 32
Client-Server .......................................................................................................................... 32
Network Topology ......................................................................................................................... 33
Bus Topology............................................................................................................................. 33
Ring Topology ........................................................................................................................... 33
Token Ring ............................................................................................................................ 33
Star Topology ............................................................................................................................ 34
Combined Topologies ................................................................................................................ 34
Cabling ........................................................................................................................................... 35
Twisted Pair ............................................................................................................................... 35
Coaxial ....................................................................................................................................... 35
Fibre-Optic Cabling ................................................................................................................... 36
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Processing Hardware ..................................................................................................................... 37
The System Unit ........................................................................................................................ 37
Power Supply ............................................................................................................................. 37
Motherboard............................................................................................................................... 37
Expansion cards ..................................................................................................................... 38
Onboard features.................................................................................................................... 39
Ports ........................................................................................................................................... 39
Central Processing Unit ................................................................................................................. 41
Control Unit ............................................................................................................................... 41
Bus ............................................................................................................................................. 41
Arithmetic Logic Unit (ALU) .................................................................................................... 41
Registers .................................................................................................................................... 42
Instruction Register................................................................................................................ 42
Accumulator .......................................................................................................................... 42
Program Counter.................................................................................................................... 42
Floating Point Unit ................................................................................................................ 42
Interrupts .................................................................................................................................... 42
Cooling ...................................................................................................................................... 43
Buses .............................................................................................................................................. 43
Types of Buses ........................................................................................................................... 43
Address Bus ........................................................................................................................... 43
Control Bus ............................................................................................................................ 44
Data Bus ................................................................................................................................ 44
External Data Bus .................................................................................................................. 44
Power Bus .............................................................................................................................. 44
Expansion Bus ....................................................................................................................... 44
Memory .......................................................................................................................................... 45
Random Access Memory (RAM) .............................................................................................. 45
RAM, CPU, and data flow..................................................................................................... 46
RAM on your motherboard ................................................................................................... 46
ROM .......................................................................................................................................... 47
BIOS .......................................................................................................................................... 47
CMOS ........................................................................................................................................ 47
Virtual Memory ......................................................................................................................... 48
Cache ......................................................................................................................................... 48
Fetch and Execute .......................................................................................................................... 49
The Four Stages of the Cycle..................................................................................................... 49
Fetch ...................................................................................................................................... 49
Decode ................................................................................................................................... 49
Execute .................................................................................................................................. 49
Store ....................................................................................................................................... 50
Communication between Components .......................................................................................... 50
Clock frequencies ...................................................................................................................... 51
Bus speed ................................................................................................................................... 51
CPU speed ................................................................................................................................. 51
Bit rate ....................................................................................................................................... 51
Computer Specifications ................................................................................................................ 52
Software ......................................................................................................................................... 53
System Software ........................................................................................................................ 53
The Operating System ............................................................................................................... 53
Modularisation ....................................................................................................................... 54
System utilities ...................................................................................................................... 54
Operating System Types ............................................................................................................ 55
Single user versus multi-user ................................................................................................. 55
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Single tasking versus multitasking ........................................................................................ 55
Single processing versus multiprocessing ............................................................................. 56
GUI versus command line ..................................................................................................... 56
Running Multiple Operating Systems........................................................................................ 57
Software Compatibility .............................................................................................................. 57
Common Functions ........................................................................................................................ 57
Operating System Examples .......................................................................................................... 58
Microsoft.................................................................................................................................... 58
DOS ....................................................................................................................................... 58
Windows 1.0-3.11.................................................................................................................. 59
OS/2 ....................................................................................................................................... 60
Windows 95, 98, Me.............................................................................................................. 60
Windows NT and 2000 .......................................................................................................... 62
Windows XP .......................................................................................................................... 62
Windows Vista ...................................................................................................................... 63
Windows 7 ............................................................................................................................. 64
Windows 8 ............................................................................................................................. 65
Apple.......................................................................................................................................... 66
'Classic' Mac OS .................................................................................................................... 66
Mac OS X .............................................................................................................................. 66
Other .......................................................................................................................................... 67
UNIX ..................................................................................................................................... 67
Linux ...................................................................................................................................... 68
Application Software ..................................................................................................................... 70
Hardware Support ...................................................................................................................... 71
System Requirements ................................................................................................................ 71
Application Interaction .............................................................................................................. 72
Data Translation Utilities ........................................................................................................... 72
Software Creation .......................................................................................................................... 73
Development Environments ...................................................................................................... 73
Levels of Programming Languages ........................................................................................... 74
Compilers, Interpreters and Assemblers – Language Translation Utilities ............................... 74
File Formats and Utilities............................................................................................................... 75
File Formats ............................................................................................................................... 75
File Conversion .......................................................................................................................... 75
File Conversion Processes ......................................................................................................... 75
File Conversion Utility Programs .............................................................................................. 76
Interaction between Hardware, Software, Data and Information .................................................. 77
Inputting Data ............................................................................................................................ 77
Processing and Storage .............................................................................................................. 77
Outputting Information .............................................................................................................. 78
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Data versus Information
The terms data and information are often used to mean the same thing. When it c omes to
computers, however, it's best to distinguish between the two.
Data is the plural of the word datum, which means a single piece of evidence. In computing
terms, data are the raw facts that are entered into a computer for processing. Data are used to
represent a fact, figure, or idea in a way that a computer can understand and work with.
Although the word "data" was originally used only as a plural, it is now used in place of
"datum" to also indicate a single piece of evidence.
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Information results from the processing of data by the computer. Information is presented in
some understandable way to the computer user. Data is abstract and unusable in its raw form
to the average computer user. It exists in the computer as a co llection of electrical signals.
Information, however, is meaningful to the computer user. Information is always presented in
a way that a person can understand, for example, on an output device such as a monitor, or on
a printed page.
Information
comes out
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Data
goes in
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Data is entered into the computer using an input device. These hardware devices provide a
way for people to "talk" to a computer in the computer's language. For example, when you
type on a keyboard you are sending signals to the computer that correspond to the letters you
are pressing. The combination of all those keystrokes, as well as mouse clicks and other
actions using input devices, can all result in a single document, like a business report.
There are many types of input devices that enable people to input data into the computer. They
include:
• Keyboards • Mice • Trackballs • Touchpads • Tablets • Scanners • Digital cameras
• Webcams • Microphones • Touch screens • Barcode readers • Digital music instruments
Note
Hardware is the generic term used to describe any part of the computer you can
physically touch.
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Processed data is delivered by the computer to the user as information through one or more
output devices. Like input devices, output devices bridge the gap between the computer and
human user—just in the opposite direction. They make what the computer is doing meaningful
and useful to the user. The business report the user typed using input devices can then be
displayed on an output device such as a monitor or a printer.
Output devices include:
• Monitors • Printers • Plotters • Speakers • Headphones
Digital versus Analogue
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Understanding how computers work also requires some understanding of the difference
between digital and analogue signals.
An analogue signal is continuous. Data is obtained from an analogue signal by measuring
small changes over time in this continuous signal. A good example of an analogue signal is a
sound wave through the air. The human ear distinguishes differences in sound by registering
the changes in the sound wave's frequency. A phonograph is an example of an analogue
device.
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A digital signal is a
sequence of 0s and 1s:
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A digital signal, however, is not continuous; it is discrete, or made up of individual elements.
Digital signals are sent using the binary number system of 0 and 1. Digital systems are rare in
the natural world, but computers rely on them. A computer is a digital device; its hardware and
software work with data in digital form. The 0 in a computer refers to an "off" electrical state;
a 1 means "on." An MP3 player is another example of a digital device.
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An analogue signal
is a continuous
Let's look at an example of analogue and digital devices that perform the same
function but in different ways. The traditional clock (right) is an analogue
instrument because the hands move continually around its face. The hands of
the traditional clock are controlled by the continuous movements of tiny
mechanisms inside it.
A digital clock, however, represents time in discrete increments, such
as hours, minutes, seconds, and divisions of seconds. Instead of the
mechanisms of a traditional clock, the digital watch has a digital
processor. The digital signal is pulsed so quickly that the digital clock
seems to present the time as smoothly as a traditional, analogue one.
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Bits and Bytes
Now let's look at how computers speak this digital language of 1s and 0s. The smallest unit of
data communications for a co mputer is called a bit, which is short for "binary digit." In
computers, a bit of data is represented by the
presence or absence of an electrical signal. If an
110110110101
electrical signal is present, the bit is represented
010111000111
011010010101
by a 1. If there is no signal, the bit is represented
010001110101
by a 0.
001001101001
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Taking this information, we can see that two bits
of information would have four possible
combinations: 00, 01, 10 , and 11. Three bits
would allow eight possible combinations: 000,
001, 010, 011, 100, 10 1, 110, and 111. Seven
bits, or a sequence of seven 0s and 1s, would have 128 possible combinations. This is the same
as 2 to the 7th power, or 27.
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Eight bits make up a byte. The bits in a byte follow a particular order understandable by the
computer. Historically, a byte contained the minimum number of bits required to encode an
alphabetic character in a computer. Today, with the adoption of many non-Western languages
into the computing world, a byte is not always sufficient to represent a character.
Counting with Binary Numbers
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How do you represent numbers in a binary, or base 2, system? As humans, we usually count
with a decimal, or base 10, system. Each place in a decimal or binary number has a value. For
example, the decimal number 4,517 has a 7 in the ones place, a 1 in the tens place, a 5 in the
hundreds place, and a 4 in the thousands place.
Here is the decimal number 4,690,489 with all of its decimal places named.
Number
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Place
4
Place as a
power of 10.
9
0
4
8
9
Millions
Hundredthousands
Tenthousands
Thousands
Hundreds
Tens
Ones
106
105
104
103
102
101
100
We can do the same thing for a binary number. Here is the binary number 10101101 with all
of its places named.
Number
1
0
1
0
1
1
0
1
Place
128s
64s
32s
16s
8s
4s
2s
1s
Place as a
power of 2.
27
26
25
24
23
22
21
20
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The first column, starting on the right, represents multiples of 1. The second row represents 2,
then 4, 8, 16, 32, 64, and 128 i n the subsequent columns. Notice that in both tables the
exponent increases by 1 each time you move to the left.
By using the values in the table, we can convert a b inary number to a d ecimal. The binary
number 10101101 would therefore represent one multiple of 128, zero of 64, one of 32, zero
of 16, one of 8, one of 4, zero of two, and 1 of 1. Adding these multiples together, we get:
128 + 32 + 8 + 4 + 1 = 173.
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Now let's use the table above to convert the decimal number 7 to binary. The highest binary
number that "works" is in the 4s place, so we put a 1 there. We have 3 remaining, so we put a
1 in the 2s place and another 1 in the 1s place. The decimal number 7 is 1112 in binary. Notice
the small "2" in the answer? That indicates the number is binary, or base 2. (We could put a
small "10" next to a decimal number if there were some question about the number system
being used. Otherwise, decimal is assumed.)
This shows us how to convert a binary number to base 10 and vice versa, but remember that
computers don't need to convert when working with data. As strange as binary math may seem
to us, computers are quite comfortable with it!
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ASCII
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ASCII stands for the American Standard Code for Information Interchange. It was developed
by the American Standards Association in 1968. ASCII was one of the early attempts to
provide a common way for computers to exchange data in a language they all could
understand.
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ASCII is a code, or character set, which uses binary numbers to represent the characters and
symbols of a language, such as English. Standard ASCII characters are 7 bits in size and are
written in one group of three numbers and a second group of four. The English capital letter A,
for example, is rendered in ASCII as 100 0001.
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ASCII is still widely used because it is understandable by any computer, but other character
sets have been developed which use 8 or more bits to represent characters. This has become
necessary to represent characters in non-English languages, as well as special symbols for
math and science.
Unicode
ASCII is gradually being superseded by a new computing industry standard called Unicode.
Unicode provides more than 100,000 c haracter representations in dozens of languages, with
the potential for even more. In addition to providing coding for non-Western languages,
Unicode accommodates right-to-left scripts such as Hebrew and Arabic. Development of
Unicode is overseen by the Unicode Consortium, a non-profit organization.
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Unicode was created in the late 1980s. It originally used 16 bits to represent each character,
meaning it could represent more than 65,000 (216) unique characters. The emphasis at the time
was on representing only modern languages, rather than also preserving older ones. In 1996,
however, Unicode's scheme was changed so that it could represent more than 1 m illion
characters.
Kilobytes, Megabytes, Gigabytes . . . and Terabytes
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The byte is also the foundation of understanding size in the computer world. Hard drives,
memory, documents, images, and many other objects are measured in bytes—or more likely,
kilobytes, megabytes, and gigabytes.
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Notice that each of these words consists of the word "byte" with a prefix indicating "how
many." Just as 1,000 m etres is a kilometre and 1,000 grams is a kilogram, 1,000 b ytes is a
kilobyte, shown with the notation KB. For example, 500 ki lobytes is usually written "500
KB." (A kilobyte is more accurately 1,024 bytes, or 210 bytes. Remember that computers think
in base 2, not decimal.)
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A megabyte (MB) is 1 million bytes and a gigabyte (GB) is 1 billion bytes. Today hard drives
of 1 trillion bytes, or a terabyte (TB), are becoming common. Computer technology has come
a long way since the floppy disk, which contained only 1.44MB of storage space.
The Processing Cycle
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A computer is constantly processing data while it is running. There are four main actions
undertaken during this process, in which data goes in and processed information comes out:
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• Input • Processing • Storage • Output
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Input
Raw data is entered into the computer using input devices such as keyboards.
Processing
Data processing is performed by the central processing unit or
CPU. The CPU is a key component found in the system unit
(contained in the computer’s case). The CPU interacts with other
parts of the system unit to process the raw data and turn it into
meaningful information.
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Data is processed by the computer using computer programs called software. Programs are
sets of instructions that tell a computer what to do with data after it has been inputted.
The processing being performed by a computer includes a range of activities, such as:
•
Verifying the accuracy of inputted data.
•
Performing any calculations required.
•
Consolidating separate pieces of data into a cohesive whole.
Computer programs are called software because, unlike hardware, they cannot be
touched physically.
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Storage
Before and after being processed, data is stored in one of a variety of locations in the system
unit. Data which is needed for current operations is stored in some type of memory. When the
data is needed again for processing it is retrieved from memory and acted upon b y the
processor. Data which is not currently needed for operations is stored on a medium like a disk
drive.
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The main storage device within the system unit is the hard disk drive (HDD). Most computers
also have removable storage capabilities like compact disc drives and floppy drives, and some
computer users have a personal flash drive that can be plugged into the computer's USB port.
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Output
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Output is the process of making information available to the computer
user. Information can be presented in many ways, such as an image
on a screen, a sound made through speakers, or a document printed on
paper.
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Important note: When a completed document is stored in a storage device such as a h ard
drive, it is still referred to as data (more specifically, as processed data). This is because
information is user-driven; it only becomes information when the computer user views it on
the screen or reads it on a printed document. The word "information" is only used for material
which is meaningful to a human, not to the stored electronic data.
Now that we have the basics, we can offer a definition of a computer:
A computer is a programmable machine that receives input, stores and processes data,
and provides output in a format that has meaning to the user.
Revision 1 (See page 1 of Student Exercise Book)
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What are Peripherals?
Peripherals are hardware devices that are not part of the core processing computer, but which
are attached to it. Some peripherals, such as a hard drive, can be attached inside the computer
system unit (that is, inside the computer's case). These are referred to as integrated
peripherals. Other peripherals, such as the keyboard, mouse, and printer, are attached to the
outside of the computer system unit.
Input Devices
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Input devices, as the name suggests, are used to input data into the computer for processing.
Keyboard
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The computer keyboard is the most commonly used computer input device. The computer
keyboard borrows its layout of letter keys from the traditional typewriter. It also has additional
keys, such as Ctrl, Alt, and the Function keys, which are of use in a computing context.
Keyboards allow you to communicate with the computer and to enter or edit data. They are
used to enter characters or perform functions that give instructions to a computer program.
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The keyboard contains a small microprocessor and a sensor grid upon w hich the keys rest.
When a key is pressed, the sensor grid detects it and sends a message to the keyboard's
microprocessor. The microprocessor then sends a message to the computer, telling it which
key has been pressed. The software that is being used then interprets the keystroke.
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There are various types and designs of keyboards available.
Standard keyboard
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The standard keyboard has all the keys positioned in straight rows. This version is most
similar to the traditional typewriter.
Natural keyboard (split or angled keyboard)
Natural keyboards, also called split keyboards, are
designed in a curve, with the keyboard split into
two halves—one for the keys struck by the left
hand, and one for the right. These are meant to
encourage a natural hand, wrist, and forearm
position.
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Multimedia keyboard
Multimedia keyboards have additional function buttons that are used to issue instructions to
the software. These extra keys provide additional functionality for quick access to often-used
software, for gaming, and for Internet access.
Mouse
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A mouse is an input device used to select and access features
within a software program. When a mouse is moved, a pointer,
or some other symbol determined by the software, also moves
across the monitor screen. This lets the user position the
pointer, or in the case of a word processing program, the
cursor, exactly where it is needed. Then an action can be taken,
such as typing text or launching a software application.
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The mouse also has buttons, which are used to perform actions.
The traditional PC mouse has two buttons at the top of the mouse. The left button is used to
select items and perform operations. The right button is used to display a so-called context
sensitive menu. The menu that appears when you click the right button depends upon the
software being used. Before 2005, the mouse used with Apple Macintosh computers had only
one button.
Some mice also have a scroll wheel, usually set between the two buttons. This wheel allows
the user to scroll up and down the screen and through documents. In some cases, the scroll
wheel can also be clicked, and so functions like a third button.
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There are several different mouse types available.
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Traditional trackball mouse
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With a traditional, trackball mouse, a ball located on its underside moves when the mouse is
moved. The movement of the ball is transferred to two sets of rollers that are touching it. The
movement of the rollers is registered by the software and is used to calculate the amount and
direction of movement of the pointer on t he screen. Trackball mice work best on specially
designed mouse pads, which provide a suitable surface for the ball to glide over.
Optical mouse
In an optical mouse, the trackball is replaced with a light-emitting diode (LED) and an optical
sensor. The movement and location of the mouse is detected by changes in reflected light. An
optical mouse can be used successfully on a wide range of surfaces; it does not require a
mouse pad. Optical mice tend to be more robust than trackball mice as they do not have
moving parts. The optical technology is also more accurate in detecting mouse movements.
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Wireless mouse
As the name suggests, wireless mice are not connected to the
system unit with a cable. Instead, radio waves or infrared
beams are used to communicate with the computer. The
mouse is powered by rechargeable batteries. The wireless
mouse offers the flexibility of being able to move the mouse
independently of the system unit. However, there is a limit to
the range at which the signals will work, and the mouse
batteries need to be replaced when they run out.
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Trackball
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Trackballs are used to perform the same functions as a mouse.
The ball is spun by the thumb to move the pointer to a location
on the screen that allows the user to select an object or access
features within a software program.
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The same working principles of a mouse apply to a trackball.
The ball's movements result in the movement of rollers inside
the trackball. The rollers are used to calculate the cursor
movement on screen. Trackballs also have some configuration
of buttons, also like a mouse.
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Touchscreen
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Laptop computers often have a built-in trackball. Large
trackballs are often used as a teaching aid for children or by
people with disabilities.
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Some types of computers let you use the monitor itself for input, instead of a mouse and
keyboard. These monitors are called touchscreens and they are popular on computers in public
places and on tablet PCs. Touchscreen monitors have a flat screen that responds to the touch of
a finger, a stylus, or a digital pen. The screen may also display a software keyboard to take the
place of a hardware one. Some newer touchscreens even have a multi-touch capability that lets
you perform actions with two fingers at once.
Touchscreens use many different technologies. One of the most popular is the resistive
touchscreen. It is made up of two flexible sheets of plastic coated with a material that is
sensitive to the touch. These sheets are separated by a gap of air. When the user presses on the
screen, the two sheets touch at that point. This creates an electrical connection which can be
received by the computer.
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Scanner
A scanner is used to convert a paper document into a digital form
that a computer can then process. Modern scanners can work with
documents that contain text or images, in black and white or in
colour. The scanner software often contains functions for
editing images or "reading" text. The ability to read text from
a scanned document and convert it into a document file is
called Optical Character Recognition (OCR).
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There are many kinds of scanners, but they all contain
a light and a scanning element. These are passed over the
document, recording a digitized image of it. The captured image is then sent to
the computer and can be manipulated by software.
Flatbed scanners
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A flatbed scanner is a scanner that sits on a desk. This type of scanner has a glass pane upon
which the document is placed, face down, either by hand or by a document feeder. (Document
feeders allow the easy scanning of multipage documents.) The light and scanning element are
then passed under the glass to create an image of the document.
Handheld scanners
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A handheld scanner can be used in the hand and on any size document.
The scanner is placed on top of the page and turned on, and is then
dragged down the page at a slow and constant speed. If an image is
large, parts of the picture will need to be scanned in separate stages
and then "stitched" together using software.
Scanner/printer/copier
Sa
Many scanners available today combine the input functionality of a scanner with the output
functionality of a printer and a photocopier. These versatile machines, often called
multifunction devices, are now becoming invaluable in both the home and small office.
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Microphone
A microphone allows you to record sound directly into your
computer. The analogue sound signal is digitized and turned into a
digital sound file, which can then be played back and edited using
special software. It is also possible to set up a computer to function
like a telephone, with the microphone and speakers replacing the
telephone handset. This is called computer telephony integration.
Headsets incorporating both headphones and a microphone are available for this use.
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Microphones are becoming more popular with the development of accurate speech recognition
software. This type of software allows you to give spoken commands to the computer. Speech
recognition software needs to be "trained" to be able to understand the user's speech patterns.
Speech recognition software is particularly useful for people with physical disabilities that
prevent them from using a keyboard.
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There are many different types of microphone, each using different technologies. All of them
are designed to pick up sound waves, which are collected by a diaphragm. These waves are
then converted into electrical signals that can be manipulated by software.
Exercise 1 (See page 2 of Student Exercise Book)
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Storage Devices
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Storage devices are used to store data so that it can be processed by the computer. Data storage
is one of two types: volatile and non-volatile. Volatile storage relies on electric power always
being available. Without power, the data can no longer be stored. An example of volatile
storage is the computer's random-access memory, or RAM. We will discuss RAM in a l ater
section. Non-volatile storage does not rely on a continual power supply. An example of nonvolatile storage is a disk drive.
Data can be retrieved from a connected storage device at any time for processing. There are
many types of storage devices available using widely different technologies. Some reside
inside the system unit while others are external to it and are joined to the computer through a
connection called a port.
Reading and Writing
Read: When data is accessed from a storage device, it is being read.
Write: When data is added to a storage device, it is being written.
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The Hard Drive
The hard drive, also known as the hard disk drive (abbreviated HDD), is the main data storage
area in most modern computers. A single computer may have a single hard drive or one
primary hard drive and one or more secondary hard drives.
The primary hard drive (named C:) is used to store the operating system and other basic data
needed to start up (or boot) and run the most basic computer functions. The primary and
secondary drives contain all of the programs installed on the computer, as well as files created
and stored by the user.
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The storage capacity of a hard drive is usually measured in gigabytes (GB), although terabytesize (TB) hard drives are now widely available in new PCs. New desktop PCs are generally
fitted with hard drives of between 100GB and 750GB.
Hard Drive construction
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The components of a standard hard drive are
contained inside a rectangular metal case. Inside the
case is a series of round, flat disks called platters,
which are coated on each side with a material that
allows them to store data in a series of magnetic
patterns. These platters are mounted at the centre onto
a spindle, which in turn is driven by a spindle motor.
Hard drives are usually 3.5 inches in diameter for
desktop PCs or 2.5 inches in laptops and other
portables.
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The data on t he disks is read by electromagnetic read/write heads, with one below and one
above each platter. The read/write heads are mounted on t he ends of slider arms, which are
connected to a device called an actuator.
External and removable hard drives
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External and removable hard disk drives work in essentially the same way as those connected
more permanently inside the computer case. External and removable hard drives have the
advantage of portability; they can be disconnected or removed, carried to a different computer,
and then reconnected.
An external hard drive consists or the hard drive itself, which is usually of the same form as an
internal hard drive, and an enclosure. The enclosure consists of a case to protect the hard drive
plus electronics that allow it to be connected to the computer via a cable. Most modern
external hard drives are connected to a computer via a USB port. The data transfer rate to an
external hard drive is slower than to an internally connected disk drive.
A removable hard drive fits into a special slot inside the computer case. It can be removed for
portability or security purposes.
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USB/Portable hard drives
As we noted, external and removable hard drives can be disconnected and
carried to a different location, making them portable. An even more
portable storage solution is the USB flash drive. These aren't disk drives
in the sense of a hard disk as described above. USB flash drives instead
use a form of non-volatile flash memory to store data and programs and
draw their power from the USB connection.
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USB drives can be very small—down to the size of a key—and thus are
highly portable. They plug into any computer with a USB port. USB
drives can hold several gigabytes of data. Today USB drives have taken on the same tasks that
floppy disks were previously used for. They have thousands of times the capacity of floppies,
however, and are more reliable due to their lack of moving parts. They are the most common
portable storage devices nowadays.
Floppy Disks
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The floppy disk drive (or FDD) was one of the original removable storage options for
computer users. Although new computers are rarely built with floppy disk drives, you may
still run across them in some settings.
Floppy disks in their various forms
were a standard means of carrying
data from one computer to another
from the mid-1970s to the late 1990s.
They have now been replaced by
cheaper, faster, and higher capacity
devices like USB drives, CDs, DVDs,
and memory cards.
Form and capacity
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The modern floppy disk is 3.5 inches square and provides 1.44 MB of data capacity. Why are
they called floppy disks when they aren't really "floppy" at all? The disk that holds data is
made of a flexible plastic material encased in a hard plastic shell. Earlier floppy disks, such as
the 8-inch variety, didn't have this hard shell, so it was truly "floppy" all the way.
Formatting and Write Protecting
Most floppies come already formatted. If not, simply insert the floppy into the drive and
follow the instructions for your operating system. For a Windows PC, right-click the A: drive
and choose Format from the pop-up menu. You can also prevent a floppy from being
accidentally overwritten with other data. To do so, move up the small tab in the upper-right of
the disk case so that the small window is open.
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Floppies' many uses
Floppies were used for many purposes other than the transferring of files. The earliest
computers contained the entire operating system on a floppy. Before the advent of the CD,
floppies were also the medium used to sell software. A word processing program, for example,
might be delivered on s ix or more floppies, which had to be inserted one after the other to
install the program. Computer system administrators often carried floppies containing
diagnostic tools they could use to troubleshoot a computer.
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Despite the disappearance of the floppy, its presence lives on i n the naming scheme for
computer drives. By default, the primary hard drive is labelled C:, with A: and B: being
reserved for floppy drives that are no longer present.
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Optical Discs
As computers became more powerful and able to work with larger amounts of data, the need
arose for a more capable removable storage system. In addition to holding only 1.44 M B of
data, the data transfer rate from a floppy to the other computer components was too slow.
Compact discs and digital video discs, both forms of optical media, came to the rescue.
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Compact Discs
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Compact discs were invented in 1982, but these original discs held only digital audio.
Compact discs designed to hold computer data were invented a few years later in 1985. These
discs are called CD-ROMs. The "ROM" part of CD-ROM stands for "read-only memory."
Data could be ready from these first CDs but could not be written upon them by the user. This
is different from the floppy and hard drive, which were read/write devices.
mp
Standard CD-ROMs hold up to about 700 MB of data, which was about 480 times the amount
a floppy could hold. This made them suitable for delivering large amounts of data, especially
data files like images, video, and sound. In addition to holding data, CD-ROMs are used to
distribute software.
Sa
A compact disc is 12 cm in diameter, 1.2 mm thick, and made of injection-moulded
polycarbonate plastic. The discs have a 15 mm hole at the centre. Data is arranged in a spiral
pattern, starting at the centre of the disc and working around to the outside. This spiral track
contains billions of pits, with spaces between them called lands, which are read by a laser. The
layer containing the data is coated with a thin layer of aluminium or gold, and then by a further
protective lacquer outer layer.
The CD drive reads the CD-ROM with a laser that passes over the spiral of pits and lands. The
variable sizes of the bumps and pits reflect light differently; data is read by registering these
changes. The reflected light is converted into a high-frequency signal and encoded into
readable data.
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Writable compact discs
Writable compact discs, called CD-Rs (for Compact Disc-Recordable), became available in
1988. These discs could be written to only once, unlike hard drives and floppies, which could
be written to many times. The first equipment created that could write compact discs was very
big and expensive. Early models cost tens of thousands of U.S. dollars and were the sizes of
cabinets. The discs were expensive, too. Blank CD-Rs for recording were around US$40 in
1991. Now CD writers are quite cheap and are standard equipment with all new computer
systems. Blank CD-Rs are also very inexpensive.
CD writers installed in computers write the data one track at a time, while writers for
commercial use—for example, making thousands of copies of a music CD—stamp the data
onto the disc surface in a single step.
You can record a music CD-R with a computer, and that CD can then be played on
most music CD players. A recorded CD-RW disc, however, cannot be played on most
music CD players.
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Note
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Rewritable compact discs, called CD-RWs (for Compact Disc-ReWritable), became available
in 1997. Data can be written to CD-RW discs many times, erased, and then written to again.
CD-RW discs are more expensive than CD-R disks, which has limited their popularity in most
settings.
DVDs
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The DVD (Digital Versatile Disc) was invented in 1995. A DVD looks like a compact disc but
has a much higher data capacity. DVDs most popular initial use was for showing recorded
movies. In most areas of the world, the DVD has replaced videotape for consumers wanting to
view movies at home. DVDs can also be used for data storage and software packaging in the
same way as CDs. DVDs come in several types, with data capacity from 4.7 GB up to about
17 GB.
Sa
The surface upon which data is written on a DVD is only half as thick as that of a compact
disc. The pits and lands are also much closer together, and the laser that reads the disk has a
much shorter wavelength than a CD reader's. These features are what allow the standard DVD
to hold so much more data than a CD.
Dual-layer DVDs (DVD-DL) provide about than 8.5 G B of data capacity, compared to the
standard DVD's 4.7 GB. Dual-layer DVDs have two, distinct layers of data on the disc. DVD
drives that support dual-layer discs shine the laser reader through the first layer to access the
data on the layer underneath.
Writable DVDs
The development of DVDs followed the same path as compact discs. The first discs were read
only and were written at a factory. A writable version of the disc and needed hardware came
later. Also like CDs, the cost of writable discs and the drives started high but now are
inexpensive and are standard components in most new computers.
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Unlike CDs, however, two different technologies exist for writable DVDs. These are denoted
by a – (minus) or a + (plus) sign. So there are DVD-R and DVD+R writable discs and
hardware. The rewritable DVDs are likewise labelled DVD-RW and DVD+RW. There are
also rewritable dual layer discs that are written the same except with the letters DL at the end.
Modern DVD writers can handle both technologies, so there is rarely any problem with
compatibility.
Combination Disc Readers/Writers
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It's no longer necessary to own separate disc drives for CDs and DVDs. Most modern optical
disc drives can read and write the full gamut of DVD and CD types. A list of Supported
Formats for a modern drive will look like this:
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DVD-ROM, DVD+R, DVD+R DL, DVD+RW, DVD-R, DVD-R DL, DVD-RW, DVD-RAM
(ver.2), CD-ROM (mode 1 and mode 2), CD-ROM/XA (mode 2, form 1 and form 2),
Photo CD (single and multiple sessions), CD Extra, CD-TEXT, CD-I (FMV), VIDEO CD,
DVD-Video, CD-Audio, CD-R, and CD-RW.
Disc speeds
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The speed of an optical disc device is defined as the multiple of a b ase rate of data transfer
speed. Speeds vary depending upon the operation being performed, such as reading, writing,
or rewriting. Read speeds are the fastest, writing second-fastest, and rewriting slowest.
The base rate of a CD drive is 150 KB per second. So a CD drive with a read speed of 1x is
transferring data at that speed. A drive with a read speed of 48x is transferring data at 48 x
150, or 7200 KB per second.
Blu-ray Discs
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The base rate of a DVD drive is about 1.4 M B per second. You can figure the speed of the
drive using the same method as above. A DVD drive that writes at 24x is writing data at about
33.6 MB per second.
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Blu-ray discs are the latest advancement in optical disc technology. A dual-layer Blu-ray disc
can hold 50 to 100 GB of data. They have been used mainly to show high-definition movies.
Adoption of Blu-ray was slow, however, compared to DVDs. This was in part because of the
cost of the discs and the hardware required. A high-definition television is needed to properly
display movies on Blu-ray discs.
Tape
Tape is an external storage medium which is most commonly used by corporations for backing
up and archiving large amounts of data. Data is copied from the hard disk and transferred onto
magnetic tape enclosed inside a case. Tapes are ideal for archiving large amounts of because
they are cheap and reliable.
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Tape stores data in a different manner than a hard disk, optical disc, and flash memory. Tape
stores data in a sequence. If you need a piece of data from the end of a tape, you have to wind
the tape to that point to access it. Other kinds of storage provide random access; when you
want a particular piece of data from a disk, you can go directly to it without having to go
through other data first. This is why tapes are mostly used for archiving; getting data off of
them is much slower than from a random-access device.
Exercise 2 (See page 3 of Student Exercise Book)
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Backup
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Data backup involves the duplication of locally stored data. This is done to avoid loss of
information in the event of the following situations:
A file may accidentally be deleted or overwritten by a user.
•
Computer hardware, particularly hard drives can
malfunction.
•
Malware, such as a computer virus, can delete or
corrupt data.
•
A fire, flood, or other event may damage the
computer.
•
Computers, especially laptops, can be stolen,
causing all data to be lost.
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•
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When data has been backed up, it can be restored with little to no work lost. The type of
backup you use depends upon the value of your data. Businesses typically back up data to an
offsite location, that is, not in the same location as the computer being backed up. D ata is
backed up to a server, a kind of computer that distributed data and services to a network. Now
if a disaster should strike or if the computer is stolen, the data is still safe and can be restored
from the server. Individuals who feel their data is not as crucial may choose to use onsite
backup.
Data can be backed up t o a variety of media, including hard drives, optical drives, and tape.
An alternative to buying your own backup hardware is to use on online backup service, such
as Mozy or Carbonite. With these services, you install software on your computer that
performs an offsite backup while the computer is on. Initial backups take quite awhile if you
have a lot of data, but subsequent backups are much quicker. You need a broadband Internet
connection to use these services.
Compression and encryption
Data that is backed up is usually compressed onto the storage media. This means the files are
stored in such a way that they take up less space on the storage media than they did originally.
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In the event of lost data, the compressed backup data is restored by decompressing the data
onto the hardware desired.
Data may also be encrypted before it is backed up. Encrypted data is processed in a way so
that no one can use it without knowing the password key it was encrypted with. This prevents
non-authorized personnel from using data stolen while in transit to a backup location or from
backup hardware.
Types of backup
There are three basic types of backup.
Unstructured and partial backups are the most common manual back-up methods,
especially for individuals. Specific files and directories are selected and then written to
backup media using a software program or by simple copying. This can result in a
collection of discs that aren't well documented, making restoration of data difficult.
•
A full backup backs up all of the files on the system which, if lost, would cause hardship
for the user. This is the most complete backup method, but it takes a long time and uses a
lot of storage space. Because of this, full backups are almost always used together with
incremental backups.
•
Incremental backups are used in conjunction with an initial, full backup. After the full
backup, an incremental backup only backs up files that have changed since the last
backup. Using incremental backups means you need to do a full backup only once.
Output Devices
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Input and output devices are sometimes referred to collectively as I/O devices.
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Note
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An output device is any piece of computer hardware that displays the processed data as
information to the user in a way he or she can understand. Output devices present information
in a variety of different forms.
The Monitor
The monitor, also called the visual display unit or simply the
screen, is the primary visual output of the computer, where the
data being processed by the computer is displayed.
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Monitor sizes are given as the length of the diagonal line from a bottom corner to the opposite
top corner. Most modern monitors are at least 17 inches, with 19-inch and larger monitors
becoming common. In addition, many computer monitors are sold now in a widescreen
format, as opposed the squarer format formerly popular.
Along with the computer's graphics card, the quality of monitor is the main factor in
determining image quality from a computer. (The role of the video card is discussed later.)
LCD monitors
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The LCD display monitor is becoming more and more popular as a replacement for the older,
cathode ray tube technology previously used. LCD stands for liquid crystal display. Monitors
using this technology are much more compact, lighter, use less
electricity, and now cheaper than CRTs, and generally provide a
sharper image. LCD monitors need to be viewed from directly in
front because its images will distort or change colour if viewed at
an angle.
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LCD monitors use the light modulating properties of liquid
crystals to function. Each pixel on the screen is composed of
these crystals and arrayed in front of a light source to produce
images.
Whereas the CRT works on the principle of emitting light, LCDs work on the principle of
blocking it. LCD, as the name suggests, uses crystals which become liquefied and change their
orientation when an electrical current is applied to them.
CRT monitors
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The LCD screen contains two pieces of polarized glass with the liquid crystals between them.
When the crystals have an electrical charge applied them, they change shape, varying the
amount of light that can pass through them. Varying in the amount of light allowed through
controls the display of images on the screen.
Cathode Ray Tube (CRT) monitors work on the same principles as an old-style television set.
The "tube" in the name is a vacuum tube, a technology which goes back decades. In a CRT
monitor, the graphics card sends data via a cable to three electron "guns" at the back of the
monitor. The guns, one for red, one for green, and one for blue, fire a controlled stream of
electrons at the phosphorus lining on the inside of the tube. The electron streams are fired in
rows of pixels from left to right and top to bottom. As they are struck by the beams, the
phosphors emit light. The colour and brightness of each pixel is dependent upon the intensity
of the individual electron beam from each gun. The size of the CRT's tube, especially in larger
monitors, makes it heavy and unwieldy compared to an LCD monitor.
Sa
15”
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Monitor facts
Refresh rate
A monitor’s refresh rate refers to the rate of speed at which a m onitor screen image is
refreshed or redrawn. The refresh rate is expressed in hertz, a general measurement of periodic
events expressed in cycles. In the case of monitors, if the refresh rate is 60 Hz, the screen will
refresh itself 60 times per second. CRT monitors should be set to refresh the screen at a speed
fast enough so that there is no noticeable flickering. A refresh rate of below 60 Hz will result
in a n oticeable flicker that can lead to eye fatigue. Generally, a refresh rate of 72 Hz is
sufficient. The capabilities of the video card, in addition to the monitor, determine what
refresh rates are available.
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Pixels and Dot pitch
The word "pixel" is short for "picture element." As
we mentioned, monitors work by creating a large
number of pixels which, when viewed together,
create on-screen images.
Original Image
Close-up, showing pixels
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Monitors use the raster method for displaying
images. Each image on a screen is composed of
many pixels of varying colour and brightness. The
resulting image is called a bitmap.
However, the pixel is not simply a little square, and it is not necessarily the smallest part of the
image. Each pixel is further divided into red, green, and blue dots. If the screen is set to its
maximum resolution, the pixel size will equal that of one dot pitch.
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Dot pitch is a complex measurement, but it generally equals the physical distance between two
adjacent "dots," whether a pixel or sub-pixel, on the screen. Dot pitch is one measurement of
the quality of monitors, with the lower the number the better the quality. Generally, the
smaller the dot pitch, the sharper and more detailed the image will be. Companies measure dot
pitch in different ways, however, so be aware of what the number actually means. groups of
phosphors – usually between 0.25 and 0.4 mm), but if it is set to a lower resolution each pixel
will comprise a number of dots.
Display Resolution
The display resolution of a screen is the measurement of the number of pixels displayed on the
screen at a time. This measurement determines the fineness or coarseness of an image. Choice
of a display resolution depends upon m any factors, especially the graphics card and the
monitor's size, shape, and capabilities.
Most monitors use a 4:3 aspect ratio, meaning that the number of pixels across the width is 4x
and the number of pixels vertically is 3x. Screen resolutions have improved along with
computer display technology. Older, 15-inch monitors may have a best resolution of 800 b y
600 pixels. Today, with monitors of 17 i nches and more, 1024 x 768 is considered the
minimum. A 20-inch widescreen monitor (with a 16:9 aspect ratio) can offer resolutions of
1600 x 900, while a 22-inch monitor can go up to 1920 x 1080.
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A higher resolution is not always better; the detail of on-screen objects increases, but they also
become smaller. Users need to find a happy medium between image detail and readability.
Monitor standards
The monitor standard combines with the specifications of the video card to determine such
things as the potential screen resolution and the number of colours that can be displayed on the
screen.
Colour Graphics Array (CGA)
Enhanced Graphics Array (EGA)
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CGA was the graphics standard used for the very first IBM computers from 1981, us ing 16
colours for fixed text and 4 colours (white, black, purple, and cyan) for graphics at a maximum
resolution of 320 x 200 pixels.
Video Graphics Array (VGA)
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Introduced in 1984, gr aphics chips build on t he EGA standard generated a digital signal for
colour and brightness, and therefore were not able to drive a modern, analog signal (VGA)
monitor. Sixteen colours were supported for both text and graphics in a resolution of 640 x
350 pixels.
The VGA graphics standard was introduced in 1987. VGA supports pixel address abilities of
up to 640 x 480 resolution and 16-bit colour (256 colours). VGA was the first analog standard,
with a refresh rate of 60 Hz or higher.
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Super Video Graphics Array (SVGA)
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SVGA, although not an official standard, is a widely used, enhanced version of VGA.
Resolutions of 800 x 600, 1,024 x 768, and higher are supported. Colour depths of 256 to 16.7
million are supported.
Extended Graphics Array (XGA)
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The XGA and XGA+ standards supported a resolution initially of 800 x 600 at high colour, or
65,536 colours. Later it supported 1,024 x 768 resolution at 256 colours, and then up to 1152 x
864.
Super Extended Graphics Array (SXGA)
The SXGA standard supports a resolution of 1,280 x 1,024 a t high colour. It is the most
common native resolution of 17-inch and 19-inch LCD monitors. SXGA+ extended the
resolution to 1400 x 1050. SXGA has a slightly different aspect ratio of 5:4, compared to
earlier standards' 4:3 ratio.
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High Definition (HD)
The HD standard is used primarily to refer to televisions rather than computer monitors. Most
computer monitors are already capable of HD or higher resolutions over VGA, DVI, or HDMI
connections. HD has a vertical resolution of 720 lines, compared to a standard television's 480
or 576 vertical lines. The HD standard has an aspect ratio of 16:9, compared to the 4:3 ratio of
standard computer monitors. This makes it suitable for showing theatrical movies, which use
the wider aspect.
Colour Depth/Bit Depth
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The colour depth (also called the bit depth) is the amount of information stored about a pixel’s
colour. The higher the number of bits that are used to describe the colours of a pixel, the finer
the colour detail shown on the screen.
Bit depth
Number of colours
displayed
Name of colour depth
4 bit
24 or 16
Standard VGA
8 bit
28 or 256
16 bit
216 or 65,000
24 bit
224 or 16.8 million
256 Colour Mode
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High Colour
The Graphics Card
True Colour
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Just as important as the monitor in enabling the display of graphics is the graphics card, or
graphics adapter. The graphics card is responsible for
creating the picture displayed by the monitor. It takes the
visual output from the computer in digital form and converts
it to an analogue signal. The signal is sent to the monitor,
which uses it to create the pixels that form an image.
In the early days of the PC, the visual output was mostly
simple text, so the CPU did all of the video processing.
However, with high colour graphics and higher resolutions,
today’s accelerated video cards function more as a highly
specialised processor for the visual output. In fact, graphics cards have become so powerful
that many require their own cooling devices, such as fans, to dissipate the heat they create.
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Onboard Video
In an effort to save expense, some motherboard manufacturers incorporate the video "card"
into the motherboard. Using a system known as Unified Memory Architecture, the video
chip set is integrated into the motherboard (the main computer circuit board). Traditionally,
this resulted in inferior video performance; however modern video chips are now offering
video quality equal to that produced by middle-range graphics cards. Onboard video (and
audio) are popular in business settings where the superior graphics performance provided by
the latest technology isn't necessary.
3D Graphics
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Standard video cards support only two-dimensions: height and width, or x
and y axes. In recent years, video technology has advanced to include the
third dimension of depth (the z axis). This is mainly due to the demand for
greater realism, more finely-detailed graphics, and higher screen refresh
rates needed in applications such as gaming. The demands of these programs started slowing
down the machines they were installed on, requiring more and more advanced graphics cards
with 3D capabilities.
Sound
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Far from just displaying text, today's computers are
expected to shine in all areas of multimedia: text,
images, video, and sound. Because of this, new
computers all contain some kind of audio
capabilities. Whereas the first computers relied solely
on the tiny speaker built into the case, they now offer
full stereo.
Sa
Sound became important with the advent of
multimedia CD-ROMs. These days it is common for websites, games, and other programs to
include sound. To be able to listen to these sounds you need to have a sound card and
speakers. To be able to record sounds yourself you will need a microphone as well.
Sound card
The sound card is an integrated peripheral used to manipulate sounds. Sound files are stored
on the computer in digital format, just like other data. A sound card has a digital-to-analogue
converter that converts the digital data into an analogue format that a s peaker can use. The
output signal is connected to speakers, an amplifier, headphones, or other device. The sound
card is also used to go in the other direction, from analogue to digital. A microphone plugged
into a sound card creates and analogue signal that the sound card converts into digital data.
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