Module 1 - Camara Education
Module 1
Concepts of Information
Technology
Module Overview
Welcome to Module 1: Concepts of Information Technology. This
module provides necessary theoretical knowledge to understand the
functioning of a modern computer, its capabilities and applications in
everyday life. It also discusses information networks, data security and
copyright issues.
Upon completion of this module you will be able to:
§
Understand what hardware is, know about factors that affect
computer performance and know about peripheral devices.
§
Understand what software is and give examples of common
applications software and operating system software.
§
Understand how information networks are used within computing
and be aware of the different options to connect to the Internet.
§
Understand what Information and Communications Technologies
(ICTs) is and give examples of its practical applications in
everyday life.
§
Understand health, safety and environmental issues in relation to
using computers.
§
Recognise important security issues associated with using
computers.
§
Recognise important legal issues in relation to copyright and data
protection associated with using computers.
Terminology
Hardware
The physical part of a computer, including its
digital circuitry.
Personal Computer
(PC)
A general-purpose computer whose price, size and
capabilities make it useful for individuals.
Central Processing
Unit (CPU)
Device that controls the operations of all the
hardware of the system and is responsible for
storing and retrieving information on disks and
other media.
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Primary Memory
Provides temporary storage of programs in
execution and the data being processed.
Random Access
Memory (RAM)
Memory that holds information for the operating
system and applications while the computer is
running.
Read Only Memory
(ROM)
Forms the basic instruction set for operating the
hardware in the system.
Bit
The smallest unit of computer data, represented by
a zero or one.
Byte
A set of eight bits.
Input
The process of getting data into a computer
through devices such as a keyboard, mouse, or
scanner.
Output
The process of getting data out of a computer
through devices such as a monitor or printer.
Storage
Devices that store computer data for a long term,
such as hard drives, CD-ROM, or flash memory.
Software
The non-physical part of a computer; programs
and documentation that play a part in a computer
system’s operation.
Systems software
Programs that enable the computer to function,
improve its performance and access the
functionality of the hardware.
Application Software
Programs that enable the user to achieve specific
objectives such as create a document, use a
database, produce a spreadsheet or design a
building.
Graphical User
Interface (GUI)
Simplifies the work of the user whether by
providing an interface that includes icons, folders
and point-and-click functionality.
Systems
Development Life
Cycle (SDLC)
The stages of development of computer programs.
Local Area Network
(LAN)
A group of computers within the same building, or
within a group of buildings that are in close
proximity, that are connected together.
Wide Area Network
(WAN)
A group of widely dispersed computers that are
connected together.
Client-Server
A network of computers that have special
Network
dedicated tasks (servers) and computers that make
use of the services (clients).
Peer-to-Peer Network
Network on which all computers have equal status.
Intranet
A collection of all computers within an
organisation that can access each other in some
way.
Extranet
An extension of an organisation’s intranet to
include outside users.
Internet
The collection of all computers across the world
which can access each other in some way.
World Wide Web
Part of the Internet that consists of all the sites that
can be accessed using a web browser such as
Mozilla, Internet Explorer, Opera or Google
Chrome.
Ergonomics
The science of co-ordination of the physical and
psychological aspects of human beings with their
working environment.
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Computer Hardware
Section overview
Welcome to this section on Computer Hardware. After studying this
section you will be able to:
•
understand the term “hardware”.
•
understand what a personal computer (PC) is.
•
distinguish between a desktop, laptop and tablet PC.
•
identify common handheld devices.
•
know the main parts of a computer.
•
understand the functioning of the central processing unit (CPU).
•
know the factors that affect computer performance.
•
know about different types of computer memory, input/output
devices and storage devices.
•
know the common input/output ports.
•
identify some common input/output devices.
Main Concepts
What is computer hardware?
Computer hardware is the physical part of a computer, including its
digital circuitry, as distinguished from the computer software that
executes within the hardware. The central processing unit (CPU),
monitor, keyboard, mouse, etc. are some examples of computer hardware.
Personal computers
A personal computer (PC) is any general-purpose computer whose
original price, size and capabilities make it useful for individuals and
which is intended to be operated directly by an end user, with no
intervening computer operator. Personal computers are available in a
number of configurations, including desktops, laptops and tablet PC.
Desktop PC
A desktop PC is a personal computer that
is designed to be stationary, as part of an
office or desktop, rather than portable.
Typically the computer is housed inside a
metal or plastic case, along with devices
such as the power supply, cooling system
and a CD, DVD and/or USB drive. The
monitor, keyboard, mouse and other
peripherals are usually separate from the main computer.
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Laptop PC
A laptop PC is designed with portability in mind. The monitor, keyboard
and computer are combined into one unit. This type of computer weighs
much less than a desktop PC and usually fits inside a carrying case and
can be moved easily from place to place.
Laptop PCs often have all of the
features of a desktop PC built in,
including a sound system, network
capability and camera. In addition,
they usually have wireless network
capability so that users can connect to
networks wirelessly when they travel.
Laptop PCs have some limitations due
to their small size. Typically the processors used in Laptop PCs are not as
fast as those in desktop PCs because of overheating concerns. Also,
laptop PCs are often more expensive than a desktop of similar capability.
Tablet PC
A tablet PC is similar to a laptop PC, but
is equipped with either a touch screen or
graphics tablet so that the computer can
be operated with a stylus or fingertip.
Some tablet PCs also come with a
keyboard, making them more similar to
laptops.
Originally, tablet PCs were designed to
run with Windows XP Tablet Edition, but
versions of Linux can be installed easily.
Handheld portable devices
A handheld portable device or simply handheld is a
pocket-sized computing device, typically having a
display screen with touch input or a miniature
keyboard. In the case of the personal digital
assistant (PDA) the input and output are combined
into a touch-screen interface. Smartphones and
PDAs are popular amongst those who require the
assistance and convenience of a conventional
computer, in environments where carrying one
would not be practical.
Portable media players are a type of handheld device used to play audio
or video files. They typically have an audio port through which
headphones are used and may have a small screen for video. More
commonly, handheld devices are being designed to combine the functions
of a PDA, phone, camera and media player in one device.
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The main parts of the computer
Following are the main parts of a computer:
•
case/chassis
•
cooling system
•
motherboard
•
CPU (central processing unit)
•
input/output ports
•
memory
•
hard drive
•
sound system
•
power supply
•
input/output devices (monitor, keyboard, mouse, printer, etc.)
Computer Performance
Computer performance is characterised by the amount of useful work
accomplished by a computer system compared to the time and resources
used.
Depending on the context, good computer performance may involve one
or more of the following:
•
short response time for a given piece of work
•
high throughput (rate of processing work)
•
low utilisation of computing resource(s)
•
high availability of the computing system or application
•
fast (or highly compact) data compression and decompression
•
high bandwidth/short data transmission time
What can affect computer performance?
•
The number of programs that automatically run during startup,
•
The number of applications opened at the same time.
•
Memory capacity.
•
Disk space.
•
Clock rate.
Central Processing Unit (CPU)
At the core of every computer is a device
known as the central processing unit, or
CPU in short. The CPU, generally
referred to as processor, is the brain of
the computer. The CPU reads and
executes program instructions, performs
calculations and makes decisions. It
controls the operations of all the
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hardware of the system and is responsible for storing and retrieving
information on disks and other media.
On large computers CPUs require one or more printed circuit boards. In
the case of PCs and small workstations they are housed in a single chip
called a microprocessor.
Parts of the CPU
There are three main components to the CPU: the Arithmetic and Logic
Unit (ALU), the Control Unit and Primary Memory.
Arithmetic and Logic Unit
The actual data processing takes place in the Arithmetic and Logic Unit
(ALU) of a computer. The ALU is responsible for carrying out arithmetic
operations such as (+, -, *, ^, /), logical operations such as (AND, OR,
NOT) and relational operations such as (<, >, <=, >=). All programs
consist of complex sets of arithmetic and logical operations. All
mathematical operations are performed in binary numbers and all logic
operations through binary operations.
Control Unit
The Control Unit is responsible for loading and interpreting the
individual instructions that constitute the computer program. These
instructions are in a language called machine code represented in a
pattern of ones and zeros. The Control Unit also has the task of fetching
the data needed by the instructions and returning the results after the
instruction has been executed.
The Control Unit controls and coordinates all hardware operations. The
ALU responds to commands from the Control Unit. The primary
functions of Control Unit are to:
•
read and interpret machine language instructions
•
control transmission of data between ALU, registers, caches,
primary memory and auxiliary memory
•
control sequence of execution of program instructions
•
direct ALU to mathematical or logic operations
Primary Memory
Primary Memory provides temporary storage of programs in execution
and the data being processed. It is an immediate access storage device.
Primary Memory is covered in detail in the section on Memory and
Storage.
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Speed of the CPU: The CPU operates as a result of electronic pulses sent
to it by another device on the motherboard called the clock. The speed of
a CPU is measured by the maximum number of pulses it is able to handle.
This is measured in MHz (megahertz) or GHz (gigahertz):
1 MHz = 1 000 000 pulses per second
1 GHz = 1 000 000 000 pulses per second
A good personal computer will use a CPU with a clock speed of over
3 GHz. This means it receives 3 000 000 000 million pulses every second
from the CPU.
Previously CPUs could only do one operation per pulse but with
advances in technology, they have been able to improve this. For
example, they can do one operation at the start of the pulse and one at the
end of the pulse.
Present day systems are coming with multi-core processors. Multi-core
systems allow for more than two separate processors housed in the same
integrated circuit. For example, a dual processor system has two separate
physical computer processors located on the same motherboard or on
separate boards, but a dual-core configuration has two processors in the
integrated circuit. This provides much greater processing power.
Memory and Storage
Like our brains, computers have the need for short-term memory
(primary memory) and long-term memory (storage). Primary memory
stores information that the CPU needs to access while the operating
system and application software are running. It is memory that can be
accessed very quickly. Storage memory is a place to store information
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that needs to be saved for a long time, such as a word document or a
digital photo.
Primary memory and storage memory work together. When you open a
document you have saved on your computer, it is transferred from storage
(e.g. your hard drive) to primary memory. When you are finished
working with the document, it is saved back to the storage memory.
In this part we will:
•
understand different types of computer memory such as: RAM
(random-access memory), ROM (read-only memory) and cache
•
understand the difference between primary memory (RAM and
ROM) and storage memory
•
become familiar with some common storage devices
•
Compare the main types of memory storage devices in terms of
speed, cost and capacity such as: diskette, Zip disk, data
cartridges, CD-ROM, internal, external hard disk
Primary Memory
Primary memory is broken down into Read Only Memory (ROM) and
Random Access Memory (RAM).
Read Only Memory (ROM)
ROM forms the basic instruction set for
operating the hardware in the system. It
resides on a chip on the computer main
board and generally speaking does not
change even when the computer is shut
down (although it can be updated
manually). It is the memory that is used
when you first turn your computer on,
before any operating systems or
applications are loaded. If ROM is damaged, the computer won’t
function.
Random Access Memory (RAM)
RAM is memory that holds information
for the operating system and applications
while the computer is running. It is
volatile, constantly changing as the
computer is working. Unlike ROM, RAM
is completely cleared when the computer
is shut down. RAM is stored on chips that
attach to the computer main board and
these chips can be easily changed or upgraded.
RAM is measured by its capacity to store information, typically in
megabytes (MB) and gigabytes (GB). As operating systems and computer
applications become more complex, the amount of RAM needed to
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support the computer’s operation increases. In the year 2000, a PC might
have shipped with 256 MB of RAM, but systems in 2009 typically ship
with 2 GB of RAM or greater.
Cache
Because the CPU can perform its operations much faster than data can be
transferred from RAM, many CPUs have on-board cache memory. This
is a type of RAM that the control unit can access very quickly and use for
intermediate storage. Further, data and instructions can be loaded into
cache before they are actually needed. When they are needed, the transfer
is much faster than it would have been if the main RAM had been used.
Memory Measurements
Bits: In all the components of a computer, data and instructions are stored
as patterns of ones and zeros. These individual ones and zeros are called
bits.
In electronic components the one is stored by switching an electronic
switch on and a zero by switching it off. On a magnetic material, such as
the surface of a hard disk, the one may be stored with a clockwise
magnetic field and a zero with a counter-clockwise field.
The reason for the use of only ones and zeros stems directly from the fact
that modem circuitry makes use of electronic switches and these can only
be on or off. The term for circuitry based on switches is digital.
Arithmetic based on the use of only ones and zeros is called binary
arithmetic.
Bytes: Bits are grouped together into sets of eight. A set of eight bits is
called a byte.
ASCII or American Standard Code for Information Interchange was
a system of representing all the characters of the western alphabet and
certain special characters in a single byte. You can think of the byte as the
amount of memory required to store a single character.
As there are only 256 possible variations within eight bits, this is not
sufficient to represent other alphabets. As a result a new system, called
Unicode, has been developed to represent all the alphabets of the world.
This makes use of two bytes or sixteen bits. With two bytes 65,536
different characters and symbols can be represented.
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Units of Memory
Because we use very large numbers of bytes for storage, abbreviations
are used for large numbers. These are based on powers of two and are set
out in the following table.
kb
kilobyte
210 = 1 024 bytes
approx. 1 000 bytes
Mb
Megabyte
220 = 1 048 576 bytes
approx. 1 000 000 bytes
Gb
Gigabyte
230 bytes
approx. 1000 000 000
bytes
Tb
Terabyte
240 bytes
approx. 1000 000 000 000
bytes
The capacity of hard drives is measured in bytes. A modern hard drive
has a capacity of one Terabyte or more.
When files are stored on disk, the amount of space they occupy is
measured in bytes. The following screen shows a partial listing of files in
a directory. Notice the second column which contains the size of the file
in bytes. (Don’t be concerned with the detail of this screen - it is shown
purely for illustrative purposes.)
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When we work with files and directories, we often need to know how
large the files are or how much space a directory and it’s files occupies.
•
One byte is one character which is a number, letter or symbol. It
consists of eight bits (binary digits) and is the smallest unit of
information a computer can process.
•
One kilobyte is 1,024 characters and is approximately equal to
one page of text in double-spacing.
•
One megabyte is 1,048,576 characters and is approximately equal
to one book.
•
One gigabyte is 1,073,741,824 characters and is approximately
equal to 1000 books.
•
One terabyte is 1,099,511,627,776 characters and is
approximately equal to a whole library of books.
Storage
Storage memory is where information is stored for a longer term, such as
the files you save from your word processing program, the digital photos
and videos that you store on your computer, the software programs that
you have installed, or your computer’s operating system. When it is
actively being used by the CPU, this information is transferred from
storage memory to RAM, where it can be accessed very quickly.
When you load a software program such as Open Office or GIMP, the
time lag you experience is related to the transfer of information from
storage memory to RAM. Some storage devices transfer this information
much more quickly than others.
Storage devices are also characterised by the amount of information they
can contain.
Storage Devices
Diskette
A diskette comprises a plastic flexible disk
enclosed inside a tough plastic cover. At one end
is a window. When the diskette is placed inside a
diskette drive, the window is pushed to the side.
The read-record head inside the drive makes
contact with the magnetic disk.
Diskettes are slow and have a low capacity (1,44 Mb). Since they are
cheap, they still tend to be commonly used for storing small amounts of
data. Another advantage is that they can be used over and over again.
Unfortunately, many are not very good quality and data can become
corrupted and unusable very quickly. The disks can become corrupt
through many causes including disk, heat, magnetism or moisture.
Because of this they are not suited to backup purposes.
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Zip disk
A zip disk is a removable magnetic
disk which fits into a special zip
drive. The surface is coated with a
special scratch resistant material
which makes a zip disk a very
robust storage device. It comes in a
number of capacities: 100, 250 and
750 Mb. The speed of a zip drive is
faster than all but the very fastest of
CD drives. Its robustness and speed make it an excellent backup device.
However, its capacity is much less than that of hard drives and tape
drives which limits its use for very large amounts of data.
Data cartridge
A data cartridge is a tape very similar to
that found in a tape recorder, only of
much higher quality. These are used in a
device called a tape streamer to record
data. Data cartridges, especially if good
quality, are reliable and cheap devices
for creating backups of large quantities
of data. They are, however, rather slow and are not suitable for storing
information that needs to be accessed frequently. Data cartridges are
sequential devices, which means that to access an item of data on them,
all the preceding data needs to be read first. They are tending to become
obsolete as newer, faster and more reliable technologies are available.
CD ROM
A CD ROM uses optical technology.
When data is written, small pits are burned
into the surface using a highly focused
laser beam. These are read by another
laser beam.
There are two types of CD ROM used for
storage. The CD-R disks can only be
written to once. Once data has been
written to part of the surface, this part can
no longer be used. CD-RW disks are
designed so that one set of data can overwrite another. This allows the
disks to be re-used many times.
CD ROM provides a reliable and storage medium for backing up and
storing data. The speed is greater than that of a diskette but slower than
that of a hard drive. Writing to a CD ROM is a much slower process than
reading it. The capacity of a CD ROM is 750 Mb.
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DVD
The Digital Versatile Disk is a development of the storage technology of
the CD ROM. Using newer storage methods and higher quality media, a
DVD can store about 4 Gb of data or 7.6 GB of data on a dual-layer
DVD. This is enough to store a full length film.
Hard disk drive
A hard disk drive can be internal or
external. An internal drive is housed
inside the main unit and is
connected directly to the
motherboard of the computer. An
external drive is housed inside a
special caddy which connects to the
computer through one of its ports on
the main board.
An external hard drive is a good backup medium and allows large
quantities of data to be stored. Since the same drive can be connected at
different times to different computers, these drives provide a useful way
of transferring data between computers that are not connected through a
network. As they are electromechanical devices, they are subject to
mechanical failure if not handled with care. The small 2½” drives used in
laptops make excellent external hard drives since they are constructed to
be moved around.
Modern hard drives commonly have capacities up to a terabyte. They are
also relatively cheap in terms of the storage capacity they offer.
Because they contain moving parts, they do eventually fail. It is difficult
to predict when a hard drive might fail. Any suspicious noise coming
from a hard drive should be viewed with great caution and the data it
contains should backed up immediately. The expected life span of a hard
drive is measured as the mean time between failures. This is a very rough
average of the working life. Figures of 250,000 hours are often quoted
but these should be viewed with caution.
Numerous systems have been developed to protect data on hard disks.
One of these is mirroring, where the data is stored simultaneous on two
disks. The one disk becomes the mirror image of the other. If one fails,
the data is still one the other. In this case, the first disk is replaced, the
system creates a mirror image of the first disk automatically and the
system continues.
There are a number of measures of performance of a hard disk. One is the
speed at which the platters turn. Typically this is somewhere between
4800 and 7200 rpm, although there are faster, more expensive disks.
Another is the access time. This is the time it takes the disk to access an
item of data. A good figure here would be around 10 milliseconds (ms).
An ms is one thousandth of a second. Disks are also sometimes compared
in terms of their data transfer rates. This is a measure of how many bytes
can be read or written per second.
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Flash memory
Flash memory is another type of
external memory used by memory
cards and USB flash drives. These are
solid state devices (no moving parts)
that connect to the computer via the
USB port or other ports built for a
specific card type. These devices
provide a very fast and reliable method
of storing data externally.
Flash memory devices are typically quite small and can be made to fit
directly inside digital cameras, video cameras, audio devices, smart
phones and personal data assistants (PDAs). Information can easily be
transferred from these devices to the computer, or between computers, by
moving the flash memory.
At the moment they are more expensive per storage unit than hard drives,
especially the larger capacity devices, but they make up for it in
convenience and portability. They tend to be limited in their storage
capacity, currently to about 32 GB, however this figure can be expected
to increase quite dramatically over time.
Online file storage
Online file storage is an emerging technology that allows users to upload
their files over the Internet to a file storage site. This is typically a free
service for the storage of small amounts of data and a paid service for
larger amounts.
The advantage of storing files with one of these services is that users can
access their files from anywhere that there is an Internet connection. A
major disadvantage, of course, is that the files can’t be accessed if there is
no Internet connection. Other major concerns are the reliability of the
service and the security of the data. These services, therefore, are not
recommended for confidential documents or when access to files is
essential.
Relative cost of storage
As in the case of computers, the cost of memory is continually changing.
The price varies from country to country as well as according to
international demand. In order to compare the cost of memory, a common
measure is to calculate the cost per Mb. The following table compares the
cost per Mb of the different media.
Medium
Hard
disk
CD
Data
cartridge
Zip disk
Flash
disk
Floppy
disk
Relative cost per Mb
0.04
0.15
0.3
0.3
3
4
This table tells you that it is about 100 times as expensive to store an Mb
of data on a floppy disk as it is on a hard drive.
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Use this table with caution. Treat the values as very approximate relative
values. In other words use them as comparative values, not as monetary
values.
Formatting disks
A new diskette or hard disk is not able to record data immediately. The
disk first needs to be prepared by a process known as formatting. This
marks out concentric circles called tracks. Each track is divided into a
number of sectors. The tracks and sectors are marked out using magnetic
markers.
As data is recorded on a disk, it fills up. To be able to re-use a disk, it
may also need to be reformatted. This releases the areas that contain data
so that new data may be stored in its place. When a disk is reformatted,
the old data is lost.
When data is stored on a disk, it is not always stored in a continuous
pattern. Rather, the system stores data in the first free area it finds. When
this has been filled, it looks for additional free space and continues
storing the data. A file ends up being stored as a series of segments across
the disk. This breaking up a file into many segments is called
fragmentation.
Fragmentation slows down the operation of the disk as the system needs
to keep track of all the different segments. A disk may be re-organised to
reduce fragmentation by a process called defragmentation.
There are different file systems available, but in all cases the disk needs
to be prepared with the index area, tracks and sectors through formatting.
As mentioned previously, disks can be
reformatted. In this process everything on
the disk is erased and the disk is formatted
as if it was a new disk.
This diagram represents the tracks (green)
and sectors (red triangular area) that are
created when the disk is formatted and
ready to store data.
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Input and Output
The central processing unit, memory and storage form the core of your
personal computer, but for a computer to be truly useful there must be a
method to get information in (input) and out (output). This is
accomplished by using a variety of input and out devices that
communicate with the computer through input and output ports.
Input/Output ports
Input/Output ports refer to the memory addresses used by the CPU for
direct communication with input and output devices. The exchange of
commands or data between the processor and the device takes place
through the I/O port address of the device. There is a specific memory
address for each type of device.
Ports also refer to physical connections located on the outside of a
computer that allow for input or output devices to be connected to it. The
graphic below illustrates the common input/output ports found on a
computer.
Input/Output Devices
Input/Output devices are the hardware devices that allow you to
communicate with your computer. Input devices such as a keyboard,
mouse or scanner allow you to send information to the central processing
unit. Output devices such as a monitor or printer allow you to get
information back from the CPU.
Input devices
The original input device was the punched card,
a technology that predates computers by many
years. Stiff paper cards were prepared by
punching holes in specific locations and then
fed into a computer to input information.
The most common input devices for modern computers are the keyboard
and mouse. Keyboards have been part of personal computers from the
beginning. Originally, computer operating systems and applications were
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very text-based. A keyboard enabled a user to input text to operating
systems and applications such as word processers. They are still essential
for inputting text into word processed and other documents.
The computer mouse was developed to help computer users navigate
around a graphical user interface such as Microsoft Windows, Macintosh
OS, or Ubuntu Linux. A mouse makes it faster to load programs, open
documents and place your cursor where you want it or select objects
within an application. Extensions of the mouse include the trackball,
joystick, touchpad and touch screen display.
Multimedia Input Devices
More recently, input devices have been developed to take advantage of
the multimedia capabilities of modern computers. These include scanners
that allow you to scan and input graphic images; sound cards and
microphones that allow you to input audio files; digital cameras and
video capture cards that allow you to input photographic images and
video; and graphic tablets that allow you to draw directly into your
computer graphics applications.
Multimedia devices, together with the
Internet and other networks, have enabled us
to use computers to communicate with
others using text, audio and video.
Specialised Input Devices
Computers in places such as banks and retail
stores make use of such specialised input
devices as card readers and barcode scanners. A
card reader reads electronic information that is
embedded in bank cards, credit cards or other
information cards. The card reader sends the
information to a computer CPU which then processes the information by
enabling a financial transaction or displaying information on a screen.
A barcode reader is a type of optical scanner that reads the barcode of an
item and sends that information to the CPU. The barcode is used to gather
information about the item, such as price and to use that information to
prepare a receipt or to track inventory.
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Output devices
Output devices are computer hardware that receive information from the
CPU and present that information to the computer user. Common
examples of output devices include computer monitors, printers and
speakers.
Output for graphics
Computer graphics can be displayed using a monitor or a display
projector connected to the graphics output port.
Original computer graphics systems were capable of displaying only one
colour and used a monochrome monitor that could display 80 columns
and 25 lines of text. Modern graphics cards are circuit boards that attach
to the computer’s main board and are capable of much higher-end
graphics such as 3-dimensional and full-screen video. The following
subunits make up a graphic card:
•
Graphics Processing Unit (GPU) – a processor dedicated to
graphics functions such as graphics acceleration and 3dimensional graphics.
•
Video Bios – a basic program that governs the operation of the
graphics card and provides instructions so that the computer can
interact with the graphics card.
•
RAMDAC – a set of instructions for displaying information on
analog monitors.
•
Video ports – for attaching monitors or other display equipment.
Computer monitors have evolved with the increased graphics capabilities
of computers, to the point now where monitors are capable of displaying
high-definition video. The most common types of displays are:
•
CRT Monitors – use a cathode ray
tube to send a stream of electrons
onto a screen coated with phosphor.
The screen glows when struck by the
electrons. CRT monitors are still
used in many desktop computer
systems. CRT monitors typically
present excellent image contrast and
the viewing angle is very good
compared to other types of monitors.
19
•
LCD Monitors – liquid crystal displays
(LCDs) use two pieces of polarised glass
with a liquid crystal trapped between
them. The screen is lit from the back and
the crystals align to allow varying levels
of light to pass through. LCD monitors
require much less thickness than CRT
monitors and are therefore typically used
on laptop systems. Also, since they take up less space, generate
less heat and use less electricity, they are becoming the monitor
of choice for desktop systems as well.
•
Display projectors – display the
computer graphics by sending light
from a metal halide bulb through a
prism that separates the light into its
red, green and blue components and
then projecting the image onto a wall or
screen. These projectors have the
advantage of creating a large display that can be viewed by an
audience.
Computer displays are characterised by the following:
•
screen size: the size of the viewable area of the screen, measured
from one corner to the opposite corner
•
aspect ratio: the comparison of the width of the display to
height. Historically computer monitors had a 4:3 aspect ratio, the
same as traditional television sets. Widescreen LCD monitors
typically have an aspect ratio of 16:9 or 16:10
•
colour depth: the number of bits used to describe the colour of a
single pixel. High end displays can produce 16.8 million different
colours
•
dot pitch: a measure of the distance between dots of colour on a
display
•
refresh rate: the number of times each second at which the
display draws the data it receives (i.e. the screen refreshes). A
high refresh rate is important to prevent flickering and eye strain
while using the computer
Output for sound
Computers have been equipped with sound chips and internal speakers
from very early in their development but because of the limitations of the
hardware, the types of sounds that could be played were simple “beeps”.
The audio suffered from low volume and distortion which required other
system processes to stop while the sound played.
20
Modern computer systems use sound
cards either attached to or integrated
with the computer main board. These
sound cards usually come with their
own memory and therefore don’t take
away processing resources from the
main computer. The sound cards have
ports for attaching speakers,
headphones, microphones and other
devices such as media players. Modern sound cards, when accompanied
by high-end speaker systems, are capable of very good sound
reproduction.
Output for print
Printers are output devices that
produce a hard copy of electronic
documents on print media (usually
paper or transparencies). Like
computers, printers have evolved to
support such features as highdefinition graphics, full-colour
reproduction and photography.
Printers are classified by the type of print technology they use. The most
common types of printers are:
Toner-based printers – such as laser printers, use toner to
produce an image either in colour or shades of grey. Laser
printers have good print quality, good print speed and a low cost
per page compared to other print technologies. The high-end
colour laser printers are capable of producing photographicquality images, but at a relatively high cost.
Liquid-ink printers – such as colour inkjet printers, work by
propelling droplets of ink onto a page. They are the most
common type of printer for the consumer because of their low
cost and excellent print quality.
Note: some devices act as both input and output devices. An example is
the touch screen monitor, which has a graphics output function and a
touch pad input function.
21
Summary
In this section, you learned:
•
Computer hardware is the physical part of a computer, including
its digital circuitry. The central processing unit (CPU), monitor,
keyboard, mouse, etc. are some examples of computer hardware.
•
The main types of personal computers are:
•
•
•
22
o
Personal computers
o
Desktop PC
o
Tablet PC
o
Handheld portable devices
The main parts of the computer are:
o
case/chassis
o
cooling system
o
motherboard
o
CPU (central processing unit)
o
input/output ports
o
memory
o
hard drive
o
sound system
o
power supply
o
input/output devices (monitor, keyboard, mouse, printer,
etc.)
Computer memory can be classified as:
o
Primary Memory (read only memory or ROM and
random access memory or RAM)
o
Storage Memory (hard drives, CD-ROM, flash memory)
Hardware can be classified as:
o
Input Devices (mouse, keyboard, scanner)
o
Output Devices (monitor, printer, speakers)
Software
Section overview
Welcome to this section on Software. After studying this section you will
•
understand the term “software”
•
distinguish between operating systems software and application
software
•
understand reasons for software versions
•
understand the main functions of an operating system
•
know about different operating systems
•
know about graphical user interfaces (GUI)
•
know about common software applications such as: word
processing, spreadsheet, database, Web browsing, desktop
publishing, accounting, together with their uses
•
know about the process of analysis, design, programming and
testing often used in developing computer-based systems
Main Concepts
What is computer software?
Computer software is the non-physical part of a computer. It is a term
used to describe the programs and documentation that play a part in a
computer system’s operation. It is an integral part of a computer system
since it forms the set of instructions that a computer needs to run.
Without software, a computer system is simply a collection of metal,
plastic and other elements with no function.
Types of Software
Software is divided into two broad categories: systems software and
application software.
Systems software
Systems software is the term used to describe programs that enable the
computer to function, improve its performance and access the
functionality of the hardware. Systems software’s sole function is the
control of the operation of the computer. You can think of systems
software as providing the foundation for applications software.
Systems software is further subdivided into operating systems and
utilities. The operating system is the program that actually makes the
computer operate. Utilities are programs which either improve the
functioning of the operating system or supply missing or additional
functionality.
23
Application software
Application software is the term used for programs that enable the user to
achieve specific objectives such as create a document, use a database,
produce a spreadsheet or design a building.
Versions
Software developers continually strive to improve the performance of
their products and add new features. Especially in a world of competing
products, each developer needs to make their product perform better,
have fewer problems and have more features. The new releases of
software products are called versions. The versions use a numbering
system such as:
•
Ubuntu Linux 12.04
•
LibreOffice.org 4.1
A change in the number before the decimal point represents a major new
version while a change in the numbers after the decimal point represents
a less significant change.
Operating System Software
As mentioned earlier, it is the operating system that actually makes the
computer function. The following is a list of some of the functions of the
operating system:
•
boot-up the computer
•
control the hard drives: this includes such features as formatting
as well as saving files to and retrieving files from disk
•
control the input/output ports
•
control input devices such as keyboards, mice and scanners
•
control output devices such as the video display and printer
•
provide the functionality for computers to be linked in a network
•
provide the foundation for application software to be launched
•
enable application software to access and use the hardware
The following list names some operating systems. They are grouped
according to similarity.
24
•
Unix; Linux; Free BSD
•
Windows 95; Windows 98; Windows Me, Windows NT4
Workstation/Server; Windows 2000 Workstation/Server;
Windows XP; Windows 2003 Server; Windows Vista
•
Macintosh OS 9; Macintosh OS X
Application Software
The following table lists some types of application software, brand names
and function.
Application
Brand names
Word processor
LibreOffice.org Writer
StarWriter
Kword
Function
Create, store, format and edit
documents, letters and articles.
Word processors are used where
the emphasis is on manipulation
of text.
Microsoft Word
Lotus Ami Pro
Corel WordPerfect
Spreadsheet
LibreOffice.org Calc
StarCalc
Kspread
Microsoft Excel
Create financial statements,
balance sheets, perform statistical
and numerical analysis of data
and make forecasts based on
numeric data. Spreadsheets are
used where the emphasis is on
arithmetic.
Quattro Pro
Lotus 123
Presentation
LibreOffice.org
Impress
Create slide shows, lectures,
seminars and other types of
presentation.
StarImpress
Kpresenter
Microsoft PowerPoint
Database
Sybase
MySQL
Microsoft Access
Email client
Evolution, Kmail
Store and convert data into
information. Databases are
particularly useful in working
with large quantities of data.
Send, receive, store and organise
electronic mail.
Microsoft Outlook
25
Application
Brand names
Web browser
Mozilla
Function
Surf the Internet and view web
sites.
Netscape
Microsoft Internet Explorer
Desktop
publishing (DTP)
Microsoft Publisher
Page Maker
Accounting
GnuCash
Pastel Accounting
Web development
Dreamweaver
DTP is similar to word
processing except that there is
more emphasis on page layout
and the integration of diagrams.
Store accounting information and
produce reports, statements and
invoices.
Create web sites that can be read
by a browser.
Microsoft FrontPage
Graphics and
imaging
The GIMP
Adobe Photoshop
Create and manipulate graphics
images and store images in a
variety of formats.
Graphical User Interface
A graphical user interface or GUI is designed to simplify the work of the
user whether they are using the operating system or an application
package. The interface consists of a screen with a number of icons or
menus. Functions are executed by pointing and clicking with the mouse.
Some of the advantages of using a GUI are:
26
•
Less work for the user. To execute a function all you have to do
is point and click on an icon instead of typing out an instruction.
•
Quicker to learn.
•
Easy access to the basic functionality of the operating system or
application package.
•
Hides the underlying complexity from the user.
•
Simplifies and integrates multitasking. Multitasking refers to
using several applications at the same time. Opening a new
application or document involves a couple of mouse clicks.
Likewise switching between tasks also involves only a couple of
mouse clicks.
There are some disadvantages to using a GUI based operating system.
•
Not all the functionality is available. The icon represents the most
commonly used form of a function. A text based system gives
you access to all the options associated with a function. Power
users tend to switch between the GUI and the system prompt as
needed.
•
Being graphics based, a GUI runs more slowly than a text based
system. However, with the power and speed of modern
computers this is not the problem it once was.
The following screens illustrate a GUI in Linux (Ubuntu) and Windows
(Windows XP).
27
The following screen illustrates the use of a menu:
In each case, clicking on an icon will either execute a function or display
another set of icons containing the function.
Software for accessibility
Software for accessibility was developed to assist people with challenges
related to computer use. It encompasses a number of software programs
that are designed to address visual, auditory and kinesthetic challenges.
The programs can be classified as an extension to operating systems.
Speech recognition
Speech recognition software converts spoken word into machine-readable
input that can be opened with text editing software. It is especially useful
for people who have difficulty using their hands because of injury. Other
uses are for transcription, where long recordings of human speech have to
be transcribed to text.
Screen readers
A screen reader is a software program that interprets the information that
is on a screen and relays that information to the user in the form of
spoken word (text to speech) or Braille output.
Screen magnifiers
A screen magnifier is a software program that enlarges a portion of the
computer screen for visually impaired people with some visual function.
On-screen keyboard
An on-screen keyboard, or virtual keyboard, is a program that allow users
to enter keystrokes with multiple input devices, such as a computer
mouse, a head mouse, or an eye mouse. It provides an alternative
mechanism for people who cannot use a physical keyboard to enter
characters.
28
System Development
Program Development Life Cycle
The development of computer programs is a highly developed and
structured process involving a number of distinct stages as shown in the
table below. The stages of development are known as the program
development life cycle.
Stage
Analysis
Description
The problem or task is analysed and clarified. This involves
analysis of the way the task is currently being done and
consultation with end users.
The project is set out in broad outline. The work of this stage is
performed by systems analysts.
Design
The project is broken down into smaller sections. These too may
be further broken down until there are units. The method of
programming each unit is then specified in great detail. The
most suitable programming language for each unit is then
chosen. The complete specification is the final design. The work
of this stage is also performed by systems analysts.
The design is handed over to programmers who code the design
into programming languages such as C+ or Java. The work of
this stage is carried out by computer programmers.
Since programs are long and complex, they may contain errors
called bugs. These may be syntactical errors, in which the
programmer made a mistake in the structure of the command, or
logical errors. In these the program appears to work, but works
incorrectly. The process of testing is designed to find and
eliminate bugs. This stage involves end users to try out the
program, programmers to fix syntactical mistakes and systems
analysts to fix errors in the logic of the program.
Programming
Testing
The following are often also included as part of the development cycle.
Implementation
Once the systems analysts are satisfied that the system is
operating correctly, it is installed and implemented. Usually this
is done using a pilot group. In this implementation, the system is
implemented on a limited scale to start with. If any further bugs
are found, these can be eliminated before full scale
implementation.
Further development
Once the system has been in use for a while, further problems,
limitations or performance problems may become apparent. The
system will then be modified and new versions released with the
changes.
29
Summary
In this section, we learned:
•
Computer software is the non-physical part of a computer. It is
a term used to describe the programs and documentation that play
a part in a computer system’s operation.
•
Software is divided into two broad categories: systems software
and application software.
Systems software is the term used to describe programs
that enable the computer to function, improve its
performance and access the functionality of the
hardware.
o Application software is the term used for programs that
enable the user to achieve specific objectives such as
create a document, use a database, produce a spreadsheet
or design a building.
A graphical user interface or GUI is designed to simplify the
work of the user whether they are using the operating system or
an application package. The interface consists of a screen with a
number of icons or menus. Functions are executed by pointing
and clicking with the mouse.
o
•
•
The stages of software development are known as the program
development life cycle. The stages of the program development
life cycle are:
o
o
o
o
o
o
30
Analysis
Design
Programming
Testing
Implementation
Further development
Information Networks
Section Overview
Welcome to this section on Information Networks. After studying this
section you will be able to:
•
Understand the concept of networks
•
Distinguish between Local Area Network (LAN) and Wide Area
Network (WAN)
•
Understand the term client/server
•
Know the advantages associated with group working such as:
sharing printers, applications and files across a network
•
Differentiate between Intranet, Extranet and Internet
•
Understand what the Internet is and know some of its main uses
•
Understand what the World Wide Web (WWW) is
•
Distinguish the WWW from the Internet
•
Know about different types of communication technologies
•
Understand the terms analogue, digital, modem, transfer rate
•
Know about the use of telephone network in computing
•
Understand the terms Public Switched Telephone Network
(PSTN), Integrated Services Digital Network (ISDN),
Asymmetric Digital Subscriber Line (ADSL)
Main Concepts
What are computer networks
A set of computers connected
together so that they can
communicate is called a
computer network. This
involves installing network
cards in each computer. Each
computer is then connected
through cabling or wirelessly to
a central device called a hub.
Operating systems contain components that are dedicated to the task of
enabling computers to communicate over a network. This software makes
use of special rules of communication called protocols. There are many
different types of protocols used for a variety of purposes. The most
commonly used protocol for establishing and maintaining communication
across a network is called TCP/IP or Transmission Control
Protocol/Internet Protocol.
31
Client-server and peer-to-peer networks
Networks on which all computers have equal status are called peer-topeer networks.
On most networks, certain computers have special dedicated tasks. Since
these machines provide services to other computers, they are called
servers. The computers that make use of the services of servers are called
clients or workstations. A network such as this is called a client-server
network.
A server which is used for the central storage of files is called a file
server. Using a file server, users can access their work from anywhere on
the network. They can also make these files available to users on other
computers. File servers also enable users to co-operate on a task by
centralising the results of their work. Sending files to a server from a
client computer is called uploading, whereas receiving a file from a
server to a client computer is called downloading.
A computer attached to a printer which users can access is called a print
server. Having a single printer rather than a printer attached to each
computer obviously saves capital.
An increasingly important type of server is an applications server. In the
case of applications servers, application packages are not installed on the
workstations but on the applications server.
A communications server is a computer dedicated to connecting a
network to the outside world. These are often called proxy servers.
As the case of print servers illustrates, one of the greatest values of
having a network is that it enables resources to be shared.
LAN
A LAN or Local Area Network is a group of computers within the same
building or within a group of buildings that are in close proximity, that
are connected together.
WLAN (Wireless LAN)
A WLAN is a Local Area Network that is connected wirelessly.
WAN
A WAN or Wide Area Network is a group of widely dispersed computers
that are connected together. These could be across the same town or
across a country or even across the world. Apart from distance, the other
feature that distinguishes a WAN from a LAN is that the WAN would
make use of a range of communication technologies such as telephone,
microwave and satellite links.
32
Advantages of Networking
Sharing Printers and Files
A peer-to-peer network is where two or more computers are linked
together in order to share information and hardware.
It is a major advantage to be able to share printers, plotters and scanners.
When computers are networked together, there can be many PCs sharing
a printer as opposed to each one having to have its own printer which is
much more costly.
It is also possible to share data files across the network by creating a
share on the hard drive and allowing other people access to that
information.
If you want to share applications you would need to investigate a
client/server network solution and some of the advantages are listed
below.
File Servers
•
Users can access their work from any workstation connected to
the network.
•
Users can easily exchange work with colleagues.
•
Users can easily co-operate on tasks.
•
Backing up is centralised and can be placed under the control of
experts who will follow the correct procedures.
Printer Servers
•
Instead of having printers attached to each computer, printers
only need to be purchased for the print servers. This results in
financial savings.
•
As there are fewer printers to look after there is lower
maintenance.
•
As far fewer printers need to be purchased better quality printers
with advanced features can be purchased.
Application Servers
•
Software only needs to be installed on the applications server
instead of each workstation.
•
The software is configured in the same way for all users.
•
Upgrading of software only needs to be done on the server.
•
Cost of licensing software for an applications server is less than
the cost of many stand-alone versions.
•
Centralising applications software simplifies the process of
implementing software policies in an organisation. Software
policies refer to what software may be installed on computers and
how it may be used.
33
Internet Connection Sharing (Proxy Servers)
•
Proxy servers contain a repository of Internet sites recently
visited and cached for quicker access at a future date.
•
Proxy servers can be configured with firewall software. This
helps protect the network from attack by hackers.
•
Files can be filtered for computer viruses before being passed on
to the network.
•
Organisations can control access of users to outside sites.
•
Since there is only one point of communication there is a large
saving on line costs.
Communication Terminology
Analogue signals
Analogue signals are used on the Public Switched Telephone Network
(PSTN) as well as for normal AM and FM radio transmissions. An
analogue signal is one which varies continuously as, for example, in
ordinary speech. An analogue signal has a graphical form as shown in the
diagram below.
Digital signals
Digital signals are used in Integrated Services Digital Network (ISDN)
and Asymmetric Digital Subscriber Line (ADSL) connections (to be
discussed later). Newer television and radio transmission techniques are
also making using of digital technology.
Digital signals are two state signals corresponding to a switch which is on
or off. The same two state signal can also represent TRUE and FALSE or
1 and 0. A digital signal is also represented graphically in the diagram
below.
Modems
A modem or modulatordemodulator is a device connected
between a computer and a
telephone line. Its function is to
convert the digital signals of the
34
computer into a form suitable for transmission over a telephone line. It
must also do the reverse and convert the telephone line signals into a
form suitable for the computer. Note that the modem used to connect to
an ISDN line is different to that used to connect to an analogue line.
Data transfer rates
Each 1 or 0 that is transferred is referred to as a bit. The speed of a data
transfer is measured by the number of bits that can be transferred each
second or bps (bits per second). This is also sometimes called the baud
rate or bandwidth.
High speed lines have their speed measured in kbps or Mbps.
1 kbps = 1 024 bps (roughly 1 000 bps)
1 Mbps = 1 024 kbps = 1 048 576 bps (roughly 1 000 000 bps)
To put these figures in perspective, the maximum theoretically attainable
speed with an analogue line is 56 kbps. This figure is very seldom
attained and the reality is usually substantially lower. ISDN lines operate
at 64 kbps.
The Telephone Network in Computing
Communications between computers rely heavily on the public telephone
system. Newer telephone line technologies have improved the standard of
communications between networks considerably. The following is a brief
description of some of the technologies that are available.
PSTN
The PSTN or Public Switched Telephone Network refers to the original
telephone network. From a communications perspective it was slow and
unreliable. Some of the exchanges on a PSTN may still make use of
mechanical switches to route telephone calls. These add additional noise
to the line. When lines are noisy, signals have to be resent repeatedly
between the source and the destination. The PSTN makes use of analogue
technology which uses continuously variable signals. An example of an
analogue signal is ordinary speech. Newer digital technologies make use
of pulses of fixed magnitude and duration.
In order to improve connections, it is possible to have an analogue leased
line. This is a dedicated permanent telephone connection between two
computers using the PSTN.
In order to connect a computer to a telephone network, you need a
modem (modulator-demodulator). The function of the modem is to
convert the digital signals from the computer into an analogue form
suitable for transmission on the PSTN.
35
ISDN
ISDN or Integrated Services Digital Network is a technological
development that is able to make use of the existing PSTN cabling to
transmit digital signals.
Technically ISDN is an international standard for the transmission of
data, voice and video or normal voice or digital telephone lines. ISDN
supports rates of up to 64kbps. An ISDN connection consists of two lines
which can be used independently or together to give a combined rate of
128 kbps.
If you wish to connect a computer to an ISDN line you need a special
ISDN modem. This is a different type of modem to the one used with an
analogue line. Its purpose, however, is the same, to convert the digital
signals of the computer into a form suitable for transmission on an ISDN
line.
It is possible to get a dedicated connection between two computers using
ISDN. This is called a diginet connection.
The older telephone systems make use of electrical currents transmitted
through copper cabling. As electric signals are subject to interference,
they are not the ideal method of transmitting data. Newer telephone
systems make use of fiber optic cable. In fiber optic technology, light is
transmitted along the cable. As light signals are not subject to the same
interference problems as electrical signals, fiber optic is a far more
efficient and reliable system.
ADSL
ADSL or Asymmetric Digital Subscriber Lines allow the transmission
of high speed digital data over ordinary telephone lines using a
modulation technology called DMT or Discrete MultiTone. Ideally, fiberoptic is the ideal medium for high speed digital transmission. As the
installation of fiber-optic is expensive, ADSL provides a solution until
copper cable is replaced by fiber-optic.
Intranet, Extranet and Internet
Intranet
An intranet is a collection of all computers within an organisation that
can access each other in some way. Users may browse computers within
an intranet using a browser but will usually not be able to access the
wider Internet. In the same way, outsiders will not be able to access the
intranet of an organisation. An intranet can be thought of as a private
Internet.
36
Extranet
An extranet is an extension of an organisation’s intranet to include
outside users. In an extranet, outside organisations or individuals are
allowed access to certain parts of the intranet. This access is usually
controlled by means of passwords and access rights. These restrict which
users can access the extranet and what they can do once they have access.
The purpose of the extranet is to facilitate business transactions with
other organisations.
Internet
The Internet is the collection of all computers across the world which can
access each other in some way. The links between computers might
include telephone, fiber optic cable, radio, microwave or satellite. Today
tens of millions of computers are able to access each other. The Internet
has no central organisation which controls its use. Because the Internet
knows no borders, many governments have tried to control the flow of
information across the Internet. However, communications technology is
so varied and so widespread that this is a near impossible task.
Uses of Internet
Some of its main uses are to:
•
integrate the operations of multinational corporations
•
provide access to and share information and databases
•
transfer and share files between computers
•
facilitate business transactions
•
share resources and information
•
promote scientific co-operation between research institutions
•
provide a communications channel for the military
•
advertise a product or service
World Wide Web
The World Wide Web or WWW is a part of the Internet. The WWW
consists of all the sites that can be accessed using a web browser such as
Mozilla, Internet Explorer, Opera or Google Chrome. In order for a
browser to access a web site, the web site must contain files that have a
particular format constructed using HyperText Markup Language or
HTML. These sites are typically developed using special web
development applications, but it is possible to create simple web sites
using a word processor by saving the document in HTML format.
The HTML documents are stored as web pages on special servers known
as web servers. These run special web server software such as Apache
Web Server or Internet Information Services.
The WWW enables the free flow of information across the world.
Developments in technology have made access to the Internet easier and
37
faster. As a result the WWW also became known as the Information
Superhighway.
Most of the activities listed under the Internet in the previous section are
now actually carried out using the World Wide Web. In other words, the
sites are created in HTML or a similar format, are installed on web
servers and are accessed by web browsers.
Connecting to the Internet
Connecting to the Internet requires a client computer connected to some
type of device that transfers data to a server computer, which is also
connected to the Internet. Connection speeds and costs can vary quite
greatly between the connection types.
Dial-up connections
Accessing the Internet through a dial-up connection means that your
computer is literally dialing a telephone number. You must use a modem
between your computer and your phone line to convert the digital signal
coming from your computer to an analog signal carried by the phone line.
This analog signal is converted by another modem at the other end of the
phone line, which then connects to a computer that is connected to the
Internet.
Dial-up is a relatively slow way to access the Internet, with maximum
speeds of 56 kbps. Also, when you are connected to the Internet, your
phone line can’t be used make or receive phone calls.
Connecting with a mobile phone
Similar to dial-up, you can connect to the Internet using some mobile
phones. Again, the connection is relatively slow, depending on whether
your cell phone and access is analog or digital. Also, you probably will
have to pay your cell phone provider for a data service plan.
Some cell phones come equipped with e-mail applications and Web
browsers to make your Internet experience more usable.
Broadband connections
Broadband connections are able to carry a broad range of frequencies.
The broader the bandwidth of a connection, the greater the capacity for
carrying data. The two main types of broadband Internet connections are
ADSL and Cable.
Because broadband connections are “always on”, they require a high
level of security, including the installation of a firewall (a program
designed to prevent unauthorised access to a computer).
Cable
Cable connections to the Internet work by using the same cable that
carries television signals. The theoretical maximum speed for a cable
38
connection is 30 Mbps, but this is seldom achieved for a variety of
reasons, chief among which is that the more people in close proximity
that are using the Internet at any time, the slower the connection.
However, cable connections provide a much higher speed than dial-up
and are comparable to ADSL.
ADSL
ADSL (asynchronous digital subscriber line) connections work by
splitting your phone line into two separate channels, one for data
(Internet) and one for voice (phone calls). This means you can talk on the
phone and be connected to the Internet at the same time.
The speed of an ADSL connection ranges from between 256 kbps to
8 Mbps, depending on what your Internet Service Provider offers.
Satellite connection
If ADSL and cable connections to the Internet are unavailable, a third
broadband choice is satellite Internet. In this scenario, a computer is
connected through a modem to a satellite dish, which sends and receives
data from a satellite. Speeds are comparable to ADSL, but setup,
equipment and service costs are relatively high.
Summary
In this section, we learned that:
•
Computer networks are a set of computers connected together so
that they can communicate.
•
There are two main categories of computer networks:
•
o
Peer-to-peer network networks are networks on which
all computers have equal status.
o
Client-server network are networks on which certain
computers have special dedicated tasks. (called servers)
and other computers that make use of the services or
servers (called clients).
Networks can also be categorised by their range:
o
A LAN or Local Area Network is a group of computers
within the same building, or within a group of buildings
that are in close proximity, that are connected together.
o
A WAN or Wide Area Network is a group of widely
dispersed computers that are connected together.
o
An intranet is a collection of all computers within an
organisation that can access each other in some way.
Users may browse computers within an intranet using a
39
browser but will usually not be able to access the wider
Internet.
40
o
An extranet is an extension of an organisation’s intranet
to include outside users. In an extranet, outside
organisations or individuals are allowed access to certain
parts of the intranet.
o
The Internet is the collection of all computers across the
world which can access each other in some way.
The Use of Information Technology (IT) in Everyday Life
Section Overview
Welcome to this section on the use of IT in everyday life. After studying
this section you will:
•
understand the use of computers and communication technology
in our everyday life
•
be able to identify some situations where a computer might be
more appropriate than a person for carrying out a task and where
not
•
know some of the uses of large scale computer applications in
corporate, public, health and education
•
understand the term teleworking
•
list some of the advantages of teleworking such as reduced or no
commuting time, greater ability to focus on one task, flexible
schedules and reduced company space requirements
•
list some disadvantages of teleworking such as lack of human
contact and less emphasis on teamwork
•
understand the term electronic mail (e-mail) and know its main
uses
Computers at Work
Computers are ideal for repetitive work requiring speed and accuracy.
This is especially true of those situations where human beings would
become bored or simply cannot work fast enough. Some examples
include:
•
corporate data processing including functions such as sorting,
selecting and summarising
•
analysis of census and other demographic data
•
administration of the national revenue system
•
actuarial calculations
•
statistical analysis
•
corporate accounting functions
•
creation of animations for films
•
weather forecasting
•
forensic analysis such as DNA and fingerprint matching
•
manufacture of electronic components and circuitry
Computer Application in Different Sectors
Corporate Application
Corporations have to keep records of their staff, details of their clients,
levels of their stock, production schedules, debtors, creditors and a
41
myriad of other details. Many of these activities are themselves linked in
one or more ways. For example, stock levels of raw materials and
production schedules are very closely linked.
The ideal solution in a corporate environment is Enterprise Software.
This is a complex suite of applications that are created to work together.
Enterprise Software is designed to automate all the activities of an
organisation in one system. The different components or modules interact
with each other. For example, if production requires certain raw
materials, the appropriate production module will send a message to the
stock module that certain materials are needed and when they will be
needed. If the stock module determines that existing levels are too low, it
will send a message to another module responsible for orders. This
module will then check which supplier to use and automatically generate
an order stating the quantity needed and a deadline for delivery.
Organisations do not buy an entire enterprise package, but only the
modules that are relevant to the operation. Because of cost and
complexity, Enterprise Software is usually found only in large
organisations.
All organisations, no matter their size, can benefit from computer
applications. Examples found in business include:
•
Office application suites such as LibreOffice.org, Koffice,
StarOffice or Microsoft Office for creating documents,
spreadsheets and presentations.
•
Accounting packages such as Pastel Accounting for keeping
debtors and creditors records and creating statements and
invoices.
•
Inventory systems for keeping track of stock.
•
Desktop publishing packages such as Microsoft Publisher and
Page Maker for creating newsletters and press releases.
•
Client tracking software such as Gold Mine for representatives to
maintain regular contact with clients and record their activity.
•
Airline bookings systems which manage large amounts of data
and reservation details and also have the flexibility to handle
frequent changes to bookings.
•
Insurance claims systems to manage the processing and payment
of claims.
•
Online banking systems enable corporations and individuals to
have easy access to funds transfer and account maintenance.
Public Sector Applications
Inland Revenue
Governments need to keep records on millions of tax payers, both
individual and corporate. It also needs to calculate the tax each has to pay
and send out tax assessments. Sophisticated computer systems manage
these tasks. For example, the South African Revenue Services (SARS)
has a website that a taxpayer can register on and submit returns
42
electronically by filling in the return online and authorising payment
directly from their bank account.
National census and other demographic data
National economic and social planning requires that governments have a
good idea of the number of people in the country and in each region.
They need to know income and health levels and size of families. They
also need to know the skills and educational levels of different sections of
the population.
This information is obtained by means of a national census. Part of this
involves people filling in census forms and these being collected and
checked by census officials. In other cases, figures are obtained by
indirect methods such as aerial photographs. In all cases the data has to
be analysed to produce summaries that planners can use. This task can
only be done by specialised software designed for the purpose.
Other organisations also collect data for specific research purposes. For
example, Medical Research Councils will conduct research to determine
the prevalence of HIV/Aids. This research relies on sophisticated
statistical software to analyse the data.
Vehicle Registration
Every vehicle has a unique registration number. This number, together
with the vehicle and owner details is kept in a central database. This
database can be accessed not only by the municipal officials, but also by
other interested parties such as the police.
Voting registers
In order to vote, a person must be recorded on the voting register. This
register of voters contains millions of records. Records need to be
changed, deleted and added on a regular basis. Because of the sheer
volume, it would be difficult to maintain in any other way than a
computerised system.
Electronic voting
This is a system that is being introduced which will allow voters to
register their choice online to submit their ballot instead of the traditional
method of marking a piece of paper with a pen.
National Identity System
Governments are keeping records of all the citizens in a country. It keeps
records of births, marriages and deaths. It also issues identity documents
and passports. All this is only possible through the use of computerised
systems.
43
Health Sector Applications
Patient records
Patient records need to record not only personal details such as name,
address, relatives and employer, but most importantly detailed health
history, record of operations and medication. The more efficiently this
information can be stored and retrieved, the more efficiently the health
care system can be administered.
Scheduling
Hospitals are extremely busy organisations which usually function amidst
considerable stress. In order to use the facilities efficiently, where
possible, activities need to be scheduled. For example, the availability of
surgeons needs to be coordinated with the availability of operating rooms
and the urgency of treatments. With good scheduling systems, much of
the stress of the more routine activities can be reduced.
Ambulance control systems
By their very nature, ambulances do not work to a schedule. They are
needed at unexpected places and unexpected times. The best a system can
do is to optimise their use. That means knowing which ambulance is
nearest to a scene at any given moment. Modern software can provide the
ambulance driver details of the shortest route and the latest on-board
software makes use of speech synthesis which actually tells the driver
how to get to a destination as he is driving. This technology makes use of
in-built maps and global positioning (GPS).
Diagnostic tools
With diagnostic tools, a doctor feeds information about a patient’s
symptoms into the system. The system will respond with a series of
possible causes. It may ask for further information to refine the diagnosis.
At the moment these tools are not replacing the diagnostic skills of a
doctor, but rather help him/her explore alternative diagnoses.
Other diagnostic tools connect the patient directly to the computer. This
is commonly used in the diagnosis of cardiac problems. Not only are all
the different heart waves displayed on the screen, but the physician has
the option of magnifying or analysing any of the patterns in more detail.
They can also be stored and compared with the heart patterns at a later
stage.
Specialised surgical equipment
A modern trend is towards less invasive surgery. This involves inserting
catheters into different parts of the body through which miniature
cameras and surgical instruments are placed. The output from the
cameras is displayed on large screens. Other relevant data is also
analysed and displayed on screens. All of the activities are assisted by
special computer programs.
44
Education Sector Applications
Student records
Education institutions have electronic registration that allows students to
be registered on the system first and further information such as personal
records and results can be added as they progress through the course.
Student records keep personal details of students as well as their
academic records and fees/accounts. Where students have had
disciplinary problems, these are also recorded. Some institutions offer
health and accommodation services to students. All this information
needs to be recorded on a centralised system that can be accessed
according to the rights different users have. For example, although health
data may be recorded on a centralised system, only health workers would
have access to it.
The same student administration system would need to send out
examination results and accounts.
Timetabling
The process of timetabling involves scheduling staff, students and lecture
rooms at the same time. The scheduling also needs to take into account
the correct total amount of time allocated to staff, students and courses.
Further public holidays and term holidays need to be taken into account.
The larger the organisation, the more complex the process becomes.
Software programs are now available which can factor in all the different
parameters and produce a timetable. This can still be fine-tuned
manually.
Computer Based Training (CBT)
Computer Based Training makes use of the computer to instruct students.
The quality of CBT material varies widely. Some CBT material is little
more than a text book on the screen, but other makes use of interaction or
simulation to instruct. For example, if a student were learning word
processing, a simulated version of the word processor would appear onscreen. The program would demonstrate how to perform a task by
showing the activity of the cursor and the display of the menus. Most of
this software produces an audible output so that the student is able to
listen to a commentary on headphones as the activity is taking place onscreen.
Automated examinations
Automated examinations allow computerised systems to test students’
skills. These are most relevant to knowledge based or skills based
courses. Courses requiring critical analysis such as literature or
philosophy are not suited to this type of testing.
Knowledge based courses can be tested using randomised multiple
choice, true/false or similarly highly structured types of questioning. If
there is a sufficiently large test bank, students can be given a random set
45
of questions. This would mean that no two students would get the same
set of questions.
Skills based courses can be tested using a simulated environment. For
example, a pilot could take a test on flying an aircraft by taking a test in a
simulator. This would appear exactly like the inside of the cockpit.
Instead of windows, there would be computer screens with a simulation
of the outside. An examiner would control all aspects of the simulation
from a computer. The pilot would be required to respond by actually
“flying” the simulator. The computer in turn would be able to analyse the
quality of the “flying”.
Distance learning
In distance learning, the student manages their own learning timetable,
when and where to learn and how long to participate in activities.
Information and Communications Technologies can facilitate part of/the
whole process. The student can send assignments and questions to the
lecturer using email/online tools and the lecturer can respond using
email/online tools. An institution may put the courses on a web site that is
password protected. A student either reads the coursework directly on the
Internet or downloads it from the Internet. This has obvious cost and
administrative savings for the institution.
It also means it can recruit students from all over the world. Registration
and payment of fees can also be done online.
Homework/Projects using the Internet
The Internet contains enormous quantities of information. Some of this is
excellent, some very poor and much incorrect. To access information on
the Internet, a student makes use of a search engine such as Google.
Feeding in a number of key words can result in a list of many thousands
of sites being displayed. Each of these is represented by a hyperlink. This
is a link to another site. When you click on a hyperlink, you are
immediately taken to the site.
There are two important aspects to using the Internet to search for
information to do assignments:
1. The skilled use of a search engine: First you need to become
familiar with the different ways of using keywords and the
various criteria you can set. This comes with practice.
2. Sifting the good from the bad: There is no control over the
Internet. People can, and do, deliberately post incorrect or biased
information on the Internet. You need to be able to assess the
quality of what you read. For example, does the site give
references to its sources or is the information corroborated by
that on another independent site. Developing a critical mind in
determining the quality of information is as important as being
able to access information in the first place.
46
Teleworking Applications
Teleworking means literally doing work at a distance. This means instead
of going into an office, you work from home, a holiday cottage, another
country or any other location. When you telework, you can be thought of
as having a virtual office.
Modern technologies such as email, the Internet and Virtual Private
Networks (VPNs) have made teleworking a reality for many people. A
VPN makes use of the Internet and various security protocols to enable
remote users to connect to a company network. Apart from speed
limitations, it will appear as if they are working on the network inside the
organisation.
Not all occupations lend themselves to teleworking, but there are many
that do. Examples include journalists, writers, computer programmers,
graphic artists, consultants and representatives. Often teleworking is
associated with contract work. Professionals are paid to do specific tasks
and are given deadlines within which these have to be created. Where
they do it is not relevant as long as it is done professionally and on time.
Advantages of Teleworking
Professionals
•
Do not waste time on commuting between home and work.
•
Are free to undertake work where ever they are.
•
Have greater ability to focus on one task.
•
Have flexibility to arrange their work time according to their
needs and inclinations.
•
Generally have tax advantages as they can claim business
expenses.
Organisations
•
Save on office space, equipment and facilities.
Disadvantages of Teleworking
Professionals
•
May suffer from lack of human contact.
•
Need to be highly self-disciplined.
Organisations
•
May not get the benefits of teamwork.
•
May have less control over workers.
The disadvantages of teleworking can be overcome by requiring
professionals to spend a certain amount of time at the office. This does
not require that they actually have a workstation or office of their own.
They could be required to attend meetings or seminars. If they are
structured as part of a team working on a project, they could be required
47
to attend team meetings which focus on planning, allocation of tasks,
feedback or general motivation.
Electronic Mail (email)
Email refers to the transmission of messages between computers across a
network or across the Internet. Email allows text, graphics and sometimes
sound. Users are able to send files together with messages. These are sent
as attachments to the email. To use email, you need to have access to a
network or the Internet. A mail client is installed on the computer. This is
used for the creation, sending, receiving and storage of email messages.
Well known email clients include Evolution, KMail, Microsoft Outlook
and Outlook Express.
Web based email systems only require that you have access to the
Internet. Many of these such as Yahoo, Hotmail, Gmail and Eudoramail
are free. Web based mail systems act as remote mail clients. Effectively,
you log on to the mail client on the server using a web browser. From that
point on, it acts in much the same way as a mail client installed on your
own computer. You can log on to your web based mail system where
ever in the world you happen to be.
Email Addresses
Email addresses consist of two parts separated by an @ symbol. The first
part is the name of the user and the second part is the name of the mail
server.
For example, in the email address [email protected], the user name is
david and the name of the mail server is icdlafrica.com. This is the
address of the computer which holds his mail.
Advantages of email
•
It is very fast and efficient. Mail is transmitted from the sender to
recipient in a matter of seconds. Recipients can reply
immediately. If both happen to be on-line at the same time, they
can conduct a conversation using email.
•
Documents and files can be sent with the email. The only
limitation is the maximum size of attachments that your system
will permit.
•
It is very cost effective. The cost of sending an email is a fraction
of the price it would be to send it as a letter.
•
There is a saving on paper, printing, postage and envelopes.
•
Email clients can be organised so that copies of emails that have
been sent can be stored under appropriate directories.
Disadvantages of email
48
•
If there is a problem with the telephone lines/networks, email
cannot be sent or received.
•
There are certain security problems such as the interception of
email by hackers. This can be overcome by encrypting email.
This requires the email to be coded into an unintelligible form
using a key. The recipients system has access to the key and is
able to decrypt the email.
•
Occasionally problems in the complex system between sender
and recipient may occur, causing email to disappear. To know
when this has occurred, it is possible for your system to request a
receipt of delivery from the recipient’s computer.
•
Unsolicited email or spam is becoming a problem. Because it is
simple to send thousands of identical emails to users at the same
time, some merchants acquire lists of email addresses and
compile these into distribution lists. They then send the same
advertising email to everyone on the distribution list. To
overcome this, anti-spamming software is now available which
identifies certain addresses as sources of spam and discards any
mail that comes from them.
Electronic Commerce (E-commerce)
E-commerce is the name given to the process of carrying out commercial
transactions over the Internet.
One of the best known examples is Amazon.com. You can purchase
books anywhere in the world from this web site. You make payment
using your credit card at the time you make the purchase. Amazon.com
exemplifies many of the characteristics of e-commerce. You are entitled
to post a comment on the site, whether good or bad, about any book you
buy. Before you purchase a book, you can look through the comments of
other purchasers. They also have a procedure in place that allows you to
return books under certain circumstances.
To purchase goods using an e-commerce site you need to provide a name
and physical address to which the goods must be sent and a credit card.
You can also specify the delivery method. This will depend on how
urgently you need the goods and how much you are willing to spend on
delivery. Good e-commerce sites will tell you in advance the availability
of the goods, how long delivery will take depending on the delivery
method chosen and the cost of delivery.
There are two types of e-commerce site. Business to consumer or B2C
sites sell directly to the consumer. Other sites involve transaction between
business themselves. These are Business to Business or B2B sites.
CNP transactions
When a purchaser uses a credit card to purchase goods, this is known as a
Card Not Present or CNP transaction, since the vendor does not
physically see the credit card. A purchaser not only has to give the credit
card number but also the three digit security code. This means that there
are a number of dangers associated with CNP transactions.
In utilising CNP transactions, vendors need to be sure that:
•
The card is not being used fraudulently.
49
Purchasers need to be sure that:
•
They can afford the goods they are buying. It is very easy to
spend money using a credit card on the Internet.
•
The vendor will not abuse the information and make
unauthorised debits. Purchasers should not deal with any
unknown sites.
•
The information will not be stolen by employees and used
fraudulently. Once again, well known reputable sites will have
measures in place and will generally take responsibility if
anything does go wrong.
•
The information will not be stolen and used by hackers. Only use
sites that are able to encrypt the information you send using a
secure link such as SSL. This eliminates the risk of insecure
payment methods.
•
They do not use public accessible computers such as in Internet
cafés to do transactions. People can easily access information
provided through the computer after you have left.
Doing Business over the Net
Advantages of on-line purchasing
•
No restriction on shopping hours. You can purchase goods 24
hours a day, seven days a week.
•
You are not put under pressure by a salesperson and have time to
make a more rational purchase decision.
•
You are not restricted to shopping in an area to which you have
physical access. You can shop across the world.
•
Usually it is much cheaper to purchase goods on-line from a
virtual store. If you purchase at source you can eliminate the
mark up of intermediaries. Further, on-line sites have lower
overheads than conventional shops.
•
You have access to a wider range of alternatives.
Disadvantages of on-line shopping from a virtual store
50
•
It is more impersonal as you do not interact with a human being
with whom you can discuss the product you wish to buy.
•
You cannot physically see and touch the item you are buying.
•
There are certain risks associated with purchasing goods on the
Internet with a credit card. See the section on CNP transactions
above.
•
Returning defective or incorrect goods can be a problem. This is
especially the case if they have come from another country.
Summary
In this section you:
•
Discussed the use of computers and communication technology
in our everyday life, including:
o Corporate Applications
o
Public Sector Applications
o
Health Sector Applications
o
Education Sector Applications
•
Identified situations where a computer might be more appropriate
than a person for carrying out a task and where not.
•
Discussed some of the advantages of teleworking such as reduced
or no commuting time, greater ability to focus on one task,
flexible schedules, reduced company space requirements.
•
Discussed some of the disadvantages of teleworking such as lack
of human contact, less emphasis on teamwork.
51
Computer Security
Section Overview
Welcome to this section on computer security. After studying this section
you will:
•
understand the term information security
•
be familiar with privacy issues in computing
•
understand the importance of data backup
•
be aware of possible implications of theft of computers
•
understand the danger of computer viruses and the best practices
for downloading
Information Security
Because information and information technology are fundamental to just
about all aspects of modern life, the modern era is often referred to as the
Information age. By its very nature, much information is private and
confidential. Information security refers to all the procedures which are
used to protect information for deliberate or accidental misuse or
dissemination. Technically, it refers to the maintenance of the integrity of
information. Integrity means that the information remains correct at all
times and cannot be accessed by unauthorised agents.
Personal privacy
If personal information such as health or finance status, personal or
family issues and background details became available to unauthorised
agents, this could lead to the standing of individuals being seriously
compromised. In some cases it may have little more effect than a feeling
of invasion of personal privacy, while in other cases it may lead to
serious embarrassment, loss of status or job and even blackmail.
Company confidentiality
Business functions by trying to achieve a competitive edge. This is
achieved by making better products and having better marketing
strategies. If competitors found out the formulation of products or details
of manufacturing or the marketing plans for new products, a company
would lose its competitive edge. There is a whole dark area to business
known as industrial espionage in which a variety of means are used to
discover trade secrets and business dealings. Obviously, there is an
absolute imperative to maintaining the confidentiality of all company
information.
A less obvious breach of information security occurs through industrial
espionage where information is either changed or deleted to sabotage the
functioning of the organisation.
52
Protecting company information
There are a number of procedures companies can take to protect their
information and these would usually be detailed in a company policy
document which would be explained to staff on appointment. Often a
personal copy of this document is given to each employee for their
records.
Staff employment practices
Basic to good company security is loyal and trustworthy staff. If staff
members are likely to have access to sensitive information, they should
be thoroughly screened before they are employed. The more sensitive the
information they have access to, the more vital is this process. Promotion
to more sensitive positions can be based on a good history or loyalty and
trust. Part of the staff induction process and on-going staff training should
inculcate in staff the importance of security and an awareness of the
consequences of its violation.
Security procedures
Information should be classified on the basis of its sensitivity. Access
rights to this information should be limited to those who need to know.
To access certain information, an employee might need a special security
clearance. All access to sensitive information should be recorded. The
question of access rights is discussed further in the next section. Sensitive
information that is stored in the form of paper files should be kept in a
secure vault. Procedures should be in place to enable staff to report
breaches or suspected breaches of security. They should be able to report
these without fear of reprisal. In large organisations security departments
can be established specifically for the purpose of providing such channels
and monitoring security on an on-going basis. This is often done in
conjunction with forensic auditing. This is a special form of auditing to
detect mismanagement and corruption.
Privacy Issues
Information stored on computers
All computers from laptop computers to mainframes contain information.
Much of this, whether corporate or personal, is confidential. Many
thousands of laptop computers containing important company or State
information have been stolen. Since most corporate records are now kept
in electronic form on computer systems, procedures need to be put in
place to protect the computers.
Apart from deliberate violations by people, computers are also subject to
accidental damage and natural disasters.
Physical procedures
Physical access to mainframes should be restricted to operators and
systems administrators. Facilities should be fire and flood proof. Highly
53
sensitive installations should also have adequate protection from criminal
and terrorist activities.
Desktop and laptop computers are very vulnerable to theft. A simple
procedure is to only allow authorised people access to offices. The use of
security cameras can also act as a deterrent. Desktop computers can be
physically attached to the floor or a work surface.
Laptop computers present the greatest risk. They are not only light and
easy to pick up, but they are also more expensive and valuable than
desktops. The best protection is not to let them out of site. If a manager is
staying at a hotel, he or she can leave the computer in the hotel safe rather
than their room.
Software procedures
Information can be stolen, altered or deleted without the computer being
physically removed. The information may even be accessed across the
Internet.
Firewalls
A firewall is the first line of defence against hackers. It is a computer
program that is installed on a computer that connects a network to the
Internet. The firewall analyses the packets that pass in and out of the
network. It is programmed to follow certain rules which enable it to
decide whether or not to allow a packet to pass. There is firewall software
available that can be installed on a stand-alone PC.
Access rights
Access rights can refer to both physical and software. In a physical sense,
these refer to different members of staff who have to gain physical access
to certain areas. For example, access to the room containing the
mainframe may be restricted to operators. Software rights refer to the
level of access different users have to different levels of data and
information. For example, some users may have no access to certain data,
others may only be able to read the data but not change it. Others in turn
may have full rights to create and change data. Access rights are
associated with a user id and password. A user id could be a user name
or a combination of letters and numbers. To log on to a system a user
would need a user id and a password. As other users may know the user
id of colleagues, another level of security in terms of passwords needs to
be added. Passwords are private and should never be divulged to anyone
else. Users could have several user ids, each with a different level of
security. They would log on each time with the lowest level of security
they need to accomplish a given task.
54
Password policies
Password policies refer to guidelines or requirements on the structure and
use of passwords. They can be required for access to a computer system
or a group of files or a single file. The following are some guidelines for
password policies:
•
They should never be blank.
•
They should not be the names of family members or pets or
anything else that would be easy for an intruder to try out.
•
Ideally they should never be words, especially words like
administrator, admin or root.
•
They should never be less than five characters and preferably
longer. Short passwords can easily be determined by a brute force
password cracker. This is a piece of software that repeatedly
feeds in all combinations of letters and numbers until access is
gained. With short passwords this can be done in seconds.
•
A good policy is to use a meaningless combination of letters and
numbers that is seven or eight characters long. What some users
do is to take a meaningful word such as looking and replace the o
with the number 0 and the letter i with the number 1 so that the
password becomes l00k1ng. You could also make a less obvious
change, for example replace k with 3 and g with 9 so that the
password becomes loo3in9.
•
Passwords should be changed on a regular basis. Administrators
can set a policy that automatically causes passwords to expire
after a certain period of time, for example 7 days.
•
When using a PC, you would need to use an operating system
that provides genuine access protection with a user id and
password. This means using Linux or Windows
NT/2000/XP/2003. In Windows 95/98/Me the logon procedure
can be bypassed. If Windows NT, 2000, XP or 2003 are used, it
should be in conjunction with the NTFS file system (NTFS is the
standard file system of Windows NT and later versions of
Windows).
Data encryption
Data should be encrypted. Encryption scrambles the data and makes it
unintelligible without the use of a key. The key is used to decipher the
data.
55
Vulnerability of data (Data Backup)
Data is vulnerable in many ways:
•
The system on which it is stored can fail. For example, a hard
drive may crash due to component failure.
•
The medium itself may become corrupt. Where data is stored on
a magnetic medium, this can become corrupt due to a number of
factors including moisture, heat, magnetic fields and
electromagnetic radiation. Even optical storage which is highly
reliable should never be regarded as infallible.
•
The system can be stolen.
•
The system could be physically damaged through war, criminal
activity, vandalism or carelessness.
•
The system could be damaged as a result of a natural disaster
such as a flood, fire or earthquake.
•
The data could be deleted or changed through criminal activity,
vandalism or carelessness.
No matter what care you may take to protect a system, additional copies
of data need to be made and stored on a regular basis. Copies of data are
referred to as backups. The following are some guidelines to working
with backups.
Once backups have been created, they should be stored in a secure area at
a different site. Never keep backups on the same site as the system. They
could be stolen or destroyed along with the rest of the system.
•
Backups should be made on a very regular basis. Even for a small
organisation, this should be done daily. Even the loss of a single
day’s work would be a major problem. In large organisations
backing up may take place on an on-going basis. A schedule of
backing up should be clear policy and strictly adhered to.
•
More than one copy of data should be made. If the data is very
valuable, the different copies could be stored in different secure
locations.
•
Different versions of the backup should be retained. The
following is an example of a backup schedule that could be
followed.
The cycle of backing up starts on the first Monday of the month. At the
end of each day of the week a backup is made. At the end of the week,
there is a Monday, Tuesday, Wednesday ... Saturday backup. On Sunday
a backup is created and labeled Week 1 backup. This is kept for the rest
of the month. The weekday tapes are then reused and the process
repeated. At the end of the month you end up with a series of weekly
backups. The last one becomes the backup for the month and the process
starts over the next month. At the end of the year you then have a series
of monthly backups.
•
56
An appropriate medium for backing up must be used. In the case
of companies this would generally be done using tape, although
optical storage is becoming more common. For personal use, a
CD or DVD makes an excellent backup. Never use diskettes for
backup purposes. They are not reliable for this purpose. Even
when backing up a PC, make multiple copies and keep them at
another site for safe storage. You could, for example, use a safety
deposit box at a bank.
Often a network server has two identical hard drives, one being a mirror
image of the other. This means that if one fails the other one can take
over. In other words all the software on the first is identical to the
software on the second.
Software can be backed up by making a copy of the CD/DVD media and
then storing the originals and using the backups to install from. This is
allowed by most software manufacturers. The original is kept under lock
and key along with the licence numbers.
Implication of Theft
Highly portable devices such as cell phones, PDAs and laptop computers
can contain vital and confidential information. Even if the information is
not confidential, it could be vital to your work. Losing your contact list or
diary will very seriously compromise your business operations.
PDAs, cell phones and laptops usually contain contact lists and diaries.
Make sure that copies of these are kept elsewhere. Cell phones and PDAs
come with synchronisation software. This software links the device with
a personal computer or laptop and updates each of them with the latest
data. In other words, if you keep your diary on your PDA, synchronising
will automatically update the diary (and contacts) on the PC or laptop.
You should make sure that your diary and contact list are on two different
devices. These should be kept apart so that they are unlikely to be stolen
at the same time. Ideally, you should make backups of these at the end of
every day and keep these backups in a safe location.
Although you can at least retain your diary, contacts and files through the
use of backups, loss of these can compromise you seriously. If for
example, you keep information of your bank and credit cards details on
your PDA, cell phone or laptop, a criminal could make use of these if
they steal these devices.
Personal information and telephone numbers of friends and business
colleagues could make them vulnerable to the activities of criminals.
Computer Viruses
A computer virus is a program that is deliberately created to cause
annoyance or alter or delete data. Some viruses cause computer systems
to slow down to the point where they are not usable. One of the features
of viruses is that they are designed to replicate and spread.
57
Types of Viruses
Trojan: A Trojan (or Trojan horse) is a virus that hides itself inside
another legitimate program. When the program is used, the virus is
released and can begin its work of replication and annoyance or damage.
Worm: A Worm is a program that replicates itself over and over in the
computer’s memory until the computer can barely function. One of the
signs of invasion by a worm is the slowness of computers.
Time bomb: A time bomb is a virus which lies dormant until a certain
date or time or for a period of time. At this date or time, the virus
suddenly becomes active and carries out whatever task it is programmed
to do. This can include the deletion of everything on the hard drive.
Logic bombs: A logic bomb is similar to a time bomb, except that
instead of becoming active at a certain time, it becomes active when a
particular activity happens. For example, instead of formatting a diskette,
the virus causes the hard drive to be formatted.
Macro-viruses: Macro-viruses make use of a special customisation
feature in applications called macros. Macros allow you to create miniprograms to carry out certain tasks in your applications.
Spread of computer viruses
Viruses are spread in a number of ways:
•
downloads from the Internet
•
pirated software
•
exchange of diskettes
•
in attachments to emails and in emails themselves
•
in documents – macro-virus, described above, can be hidden in
ordinary documents, spreadsheets and presentations
Virus Protection
The actions of computer viruses were discussed in the previous section.
The measures you can take to protect yourself against viruses will be
discussed in the next section. One of the main measures to protect against
viruses, anti-virus software, is discussed in this section.
Anti-virus software
Anti-virus software scans files for pieces of code, called signatures,
which it recognises as part of a virus. Updating anti-virus software mostly
involves updating the signatures file. This should be done on an as
frequent as possible basis. This is even more the case when you receive
files regularly from outside sources. The actual anti-virus program itself
will be updated from time to time. These updates will include additional
features and improved methods of scanning.
58
It is important to keep in mind that no anti-virus software is perfect. It is
only as good as the techniques it uses for detecting viruses and the
currency of the signature file. There is always the chance that a virus will
go undetected. However, a good anti-virus system installed on your
system is essential and will usually detect most viruses.
When a virus is detected, the software will attempt to remove the virus.
This is called cleaning or disinfecting. It sometimes happens that the
system can detect the virus but not get rid of it. In this case, you will
usually be given the option of deleting or quarantining the infected file.
When a file is quarantined, it is made unusable and so unable to spread
the virus. A future update of the software may be able to remove the
virus. If it can the quarantine is removed.
Best Practices when Downloading
There are a number of measures you can take to protect yourself from
viruses:
•
Install good anti-virus software and update it on a regular basis,
for example at least once a month but preferably once a week.
But always remember, anti-virus software is not perfect. It cannot
be the only measure you take.
•
Scan all diskettes before reading them.
•
Enable the auto-protection feature on the anti-virus software to
scan emails.
•
Be wary of emails from unknown sources, particularly if they
contain attachments. Some very careful users delete emails they
are unsure of without opening them.
•
Use an Internet Service Provider that scans emails before
delivery.
•
Do not download files/software from unknown Internet sites.
•
Be careful of using diskettes from unknown sources.
•
Do not install pirated software.
59
Handling Viruses
Using Virus Scanning Applications
Because viruses are still uncommon on Linux systems, there has not been
a great deal of development of anti-virus software. One example of opensource antivirus software that scans computer files as well as incoming
emails is KlamAV.
The Importance of Updating Virus-Scanning Software Regularly
As viruses are created on an on-going basis, they need to be analysed
continuously by the developers of anti-virus software. Not only do the
developers need to be able to extract the signature of the virus, they also
need to analyse how the virus acts and how it can be removed from the
program. These changes then need to be incorporated into the anti-virus
software.
Users in turn need to download these changes and update their software.
The longer the period between updates, the more vulnerable computer
systems are to the action of new viruses. Updates are often made
available on a daily basis by developers.
Summary
In this section you:
60
•
became familiar with the main aspects of information security,
including:
o Personal privacy
o Company confidentiality
o Staff employment practices
o Security procedures
•
understand the importance of data backup
•
became aware of possible implications of computer theft
•
understand the danger of computer viruses and the best practices
for downloading files.
Copyright and the Law
Section Overview
Welcome to this section on Copyright and the Law. After studying this
section you will:
•
understand the concept of copyright when applied to software
and different types of electronic information
•
know about shareware, freeware and end user license agreement
•
be aware of data protection legislation
Copyright Concept
Copyright refers to the legally protected right to publish and distribute
any literary, musical, artistic or software material. This means that only
the developer and authorised sellers have the right to copy and distribute
computer software, video materials, music or text.
Because there is no control over the Internet, there are hundreds of sites
where software, music and videos can be downloaded. Access to
permanent connections makes downloading of large files physically
possible. Many of these sites are located in countries that do not protect
copyright.
The fact that it is possible to copy/download something, does not make it
legally and ethically right. Authors and developers are entitled to a return
on their creative efforts. Downloading pirated material is both ethically
and legally wrong. By reducing revenue, piracy can hamper the
development of software. Software development is expensive and part of
the royalties are needed for future development.
Software piracy is a form of theft. It is both a criminal and a civil offence.
Developers are entitled to claim damages in cases of piracy. Increasingly
they are making use of all legal avenues to reduce piracy and obtain
compensation where it has occurred. They are entitled to claim damages
against not only sites, organisations and individuals who make pirated
software available, but also those who make use of it.
Downloading from the Internet is not the only form of software piracy.
Making copies of software, other than for personal use, as well as
installing software on more computers than specified in the licence
agreement are also forms of piracy.
61
Copyright Issues
When you purchase software, you are actually purchasing the right to
install the software on a specified number of machines. Software usually
comes out in two forms, standalone and network. When you purchase
standalone software, you are purchasing the right to install it on a single
machine. Generally there are further restrictions that are specified in the
licence agreement. Licence agreements are covered in the next section.
When you purchase a network version of the software, you purchase the
right to install the software on computers attached to a particular network.
This may give you the right to install it on all the computers on the
network or a certain maximum number.
It is important to realise that you do not purchase the actual program. The
program remains the intellectual property of the developer. The concept
of intellectual property is used as the developer owns something abstract,
something which is the result of considerable intellectual effort. This also
means that you do not have the right to alter the program in any way
other than the configuration allowed in the installation.
However, you may store the program on CD, DVD, zip disk, diskette,
hard drive or tape, the program still remains the intellectual property of
the developer. This does not mean that you may lend the stored program
out to others, though. This would be a breach of copyright. The stored
version is for that purpose only as a backup and for the licensed user
only.
The section on licence agreements in the next section specifies some of
the copyright issues in more detail.
Licencing Issues
Licence agreements
As mentioned in the previous section, when you purchase software, you
only purchase the right to use the software subject to certain conditions.
These conditions are specified in the licence agreement. When you install
the software onto a computer, there is always a stage where you have to
make a selection that you have read and accept the terms and conditions
of the licence agreement. When you do this, you are agreeing to the
developer’s rights under copyright law.
The terms of the licence agreement include the following:
62
•
clarification of the licence as meaning the right to use the
software, not ownership of the intellectual property
•
the number of machines on which the software may be installed
•
restrictions on copying the distribution CD
•
restriction on the resale of the software
•
prohibitions on altering the code and reverse engineering.
Reverse engineering involves a process of uncovering the logic
and algorithms used to develop the program
Shareware
Shareware is software, generally downloaded from the Internet, which
can be freely used and distributed. However, it does require that if users
would like to continue using it, they pay the developer a fee. This is
nearly always done by means of a credit card transfer across the Internet.
When payment is received, users get a serial number which they insert
into the software.
To attempt to enforce payment, developers usually employ a number of
methods:
•
Nag notices. These are notices that appear on a regular basis
reminding the user that the software has not yet been registered.
•
Time limitations. The software can be used for a certain period of
time. At the end of this period it ceases to work.
Function limitations. The shareware version may exclude certain
key features.
These limitations would be removed when a valid serial number is
entered.
•
Freeware
Freeware is software which can be freely copied and distributed. Usually
there are certain restrictions such as it may not be resold or its source
should be acknowledged.
Open Source Software
An interesting evolution in software development is the Open Source
Movement. This movement has the objective of creating software that
can be distributed freely, changed and used at no charge. Developers all
over the world are encouraged to become part of the movement. Many
corporations are playing an active role in the development of open source
software. Two examples are Linux and LibreOffice.org. The development
of Linux is being actively supported by corporations such as IBM and
Sun Microsystems.
Open source software is still subject to a licence agreement. However, the
licence agreement is quite different in tone and purpose from that
attached to commercial software.
63
The following is an extract from the licence agreement of KOffice,
another Open Source office application suite.
Preamble
The licenses for most software are designed to take away your freedom to
share and change it. By contrast, the GNU General Public Licenses are
intended to guarantee your freedom to share and change free software-to
make sure the software is free for all its users.
This license, the Library General Public License, applies to some
specially designated Free Software Foundation software and to any other
libraries whose authors decide to use it. You can use it for your libraries,
too.
When we speak of free software, we are referring to freedom, not price.
Our General Public Licenses are designed to make sure that you have the
freedom to distribute copies of free software (and charge for this service
if you wish), that you receive source code or can get it if you want it, that
you can change the software or use pieces of it in new free programs; and
that you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to
deny you these rights or to ask you to surrender the rights. These
restrictions translate to certain responsibilities for you if you distribute
copies of the library, or if you modify it.
For example, if you distribute copies of the library, whether gratis or for a
fee, you must give the recipients all the rights that we gave you. You
must make sure that they, too, receive or can get the source code. If you
link a program with the library, you must provide complete object files to
the recipients so that they can relink them with the library, after making
changes to the library and recompiling it. And you must show them these
terms so they know their rights.
Data Protection Legislation
Because of the all-pervading nature of information and communications
technology as well as the ease with which data can be accessed and
transferred, some countries have introduced legislation to protect the
privacy of individuals and organisations.
The purpose of data protection legislation is to specify how data may be
obtained, stored and used. This type of legislation can be very technical
and complex. Some of the key points of the Data Protection Act of 1998
of the United Kingdom are set out below as an illustration of the issues
covered.
64
The provisions of the act refer to data in whatever way it is stored,
whether electronic or paper.
•
Personal data should be obtained in a fair and lawful way.
•
Data should be processed in accordance with its original purpose.
If data is to be used for purposes other than for which it is
collected, safeguards need to be put in place to avoid abuse.
•
Data must be up-to-date and accurate.
•
Data must not be kept for longer than is necessary.
•
Appropriate security measures must be in place to prevent:
- unlawful or unauthorised processing;
- accidental loss;
- damage; and
- theft.
•
Personal data may not be transferred.
•
Data may not be used for certain purposes such as direct
marketing.
In addition, subjects of the data have certain rights. These include the
right to access data held about them.
Summary
In this section, you:
•
discussed the concept of copyright when applied to software and
different types of electronic information
•
learned about shareware, freeware and end user license
agreements
•
learned about data protection legislation
65
Health Safety and Environment
Section Overview
Welcome to this section on Health, Safety and Environment. After
studying this section you will be able to:
•
understand what elements and practices can help create a good
working environment
•
become aware of issues related to health and environment and the
precautions that can be taken
Ergonomics
Ergonomics is the science of co-ordination of the physical and
psychological aspects of human beings with their working environment.
Although computers present us with great opportunities for making our
work easier, they do present some health and safety risks if used
incorrectly. The science of ergonomics tells us how to use computers
correctly.
Monitors
If you work with a monitor, tired, sore or blood-shot eyes indicate eye
strain. The following points indicate some aspects of monitors to be
aware of.
•
Refresh rate
The refresh rate of a monitor is the rate at which it updates the images on
the screen. When the refresh rate is too low, the screen appears to flicker.
Apart from the annoyance factor, this causes eye strain. The refresh rate
should be at least 72 Hz (72 times a second) and preferably higher.
•
Reflection/Glare
Reflections/glare on the screen can cause eye strain. This can be
overcome by using a monitor filter with an anti-glare screen or by placing
a special anti-glare cover in front of the screen.
•
Focus
The image on the screen should be sharp. Poor quality monitors have a
slightly blurred effect. This causes the eyes to continually attempt to
reduce the blur.
•
Low radiation
The beam of electrons that strikes the screen to display the image also
sends out electromagnetic radiation. There is some fear that this can be a
66
health hazard, particularly to pregnant women. Use a monitor with low
electromagnetic radiation.
•
Position
Place the monitor in a position where you can look into the distance at
regular intervals. To the side of a window is an ideal position. You need
to change the focus of your eyes on a regular basis to prevent eye strain.
•
Angle
The monitor should be slightly below eye level. Looking up at a monitor
can cause strain in the neck.
•
Rest
Take regular rest periods where you do not look at the monitor.
Keyboards and mouse
Repeated use of the same muscles and joints can result in a type of injury
called RSI or Repetitive Strain Injury. This type of injury can range from
inflammation of joints, to damaged ligaments and muscles or even
hairline fractures in bones. RSI is usually caused by the incorrect use of
the keyboard and mouse.
•
Ergonomic keyboards
Ergonomic keyboards are designed in such a way that the strain on the
hands and finger are reduced.
•
Touch typing
Learning to touch type can help reduce strain as it distributes the work
evenly between the fingers. Users who can touch type also tend to use far
less force when striking the keyboard.
•
Mouse mats (pads)
Mouse mats or pads are available with a cushion for the wrist to rest on.
Repeated clicking of the mouse buttons can lead to inflamed finger joints.
Resting the wrist on the cushion reduces this effect.
Rest: Take regular breaks to rest the muscles and joints.
67
Desks and chairs
•
Height and position of chairs
The height and position of the chair is an important factor in reducing
strain. These should be adjusted so that:
•
the feet can rest flat on the floor. This maintains blood circulation
•
the thigh is horizontal to the floor
•
the head can be kept upright in line with the spinal column. If the
chair is too high, the head will be bent. This will in turn cause
backache
A chair with adjustable height will allow you to find the most appropriate
and comfortable height for your build.
•
Posture
The back should be slightly bent forward. Sitting rigidly upright for long
periods can cause stress in the back and shoulders.
•
Support
There should be support for the lower back to avoid sitting in a hunched
position.
•
Rest
It is important to get up and move around on a regular basis and do some
stretching exercises to help relax tense muscles.
•
Height of the desk
A common problem is having a desk which is too high. This is largely a
matter of trial and error. A good test is whether the elbows are able to rest
comfortable on the work surface.
68
Health Issues
Lighting and ventilation
It is important to ensure that there is adequate lighting, but does not cause
a glare on the screen. Another important consideration is whether there is
enough air circulation in the room as computers generate a lot of heat and
if a room is not adequately ventilated it can become stuffy and cause
fatigue. It is also not good for the equipment so most companies make
use of air conditioning.
Other health problems associated with using a computer as discussed in
the previous section are listed below:
•
repetitive strain injury
•
eye strain caused by the glare on the screen
•
back problems due to poor seating or bad posture
Precautions
Apart from health issues, there are a number of safety issues associated
with the use of computers.
Adequate grounding (earth)
A faulty grounding system can cause electrical shock. A good system will
be properly grounded and will incorporate earth-leakage detection. If the
system detects a fault that could lead to electrical shock, a switch will trip
before any damage can be done.
Cabling
It is common to see electrical cabling lying on the floor of offices. Apart
from the fact that it looks untidy, workers can trip over cabling. Electrical
cabling should be installed by electricians so that there is a minimum of
open cabling. Electrical power sockets should be installed close to
workstations so that there is no need to run cabling across the floor. The
cabling between the power point and the computer should be secured
using cable ties.
Load on power points
There should be adequate power points for the equipment. Overloaded
power sockets are a fire hazard. If there is any sound of sparking in a
power socket, the cause should be investigated by a qualified electrician.
The Environment
Paper
One of the goals on information technology was the paperless office. The
reality is quite different and users are often careless and wasteful in the
69
use of paper. The cost factor will be considered in the next section. From
an environmental perspective, waste of paper is very damaging. Here are
some things that you can do to reduce the environmental impact.
•
Do not throw paper away. Set up a storage area for paper that
cannot be re-used. Have this collected on a regular basis for
recycling.
•
Print on both sides of the paper. Unless you are producing a
document in final form, print on the reverse side of used paper.
•
Alternatively, look for organisations that can make use of this
paper. Many poor schools would be very glad to get supplies of
paper that can still be used on one side.
Consumables
Often users throw used toner and ink cartridges away. There are two
alternatives. You can have them refilled or if this is not an option because
of guarantee restrictions on printers, you could resell them to companies
which refurbish cartridges for resale. In either case, you reduce the waste
output from your organisation.
Power
Another area where users are often careless is electrical power
consumption. For example, many users only switch their monitors off at
the end of the day so they do not have to boot up in the morning. Apart
from the security risk, this means that the computer is running all night
and wasting electrical power. Switch off any equipment that does not
need to be on.
When purchasing equipment, low power options should be selected. An
example would be the purchase of flat LCD screens over older CRT
monitors as these consume less power.
It is also possible to configure the computer to save power. For example,
when a component, such as the monitor, has not been used for a while,
the computer can shut it down after a period of time to save power.
Environmental Consciousness
Using networks and email, there
is little need to send printed
documents. Rather send them in
electronic format. In addition to
avoiding printing, it is faster and
more efficient.
Avoid printing documents even
for your own use unless it is
necessary. It is quite possible to
do much of your reading onscreen. Set the zoom and font size to facilitate on-screen reading.
70
Older, used computers present an environmental hazard when they go
directly to a landfill before being processed. Certain chemicals in the
computer’s construction can lead to degradation of land and water.
Research the options in your community for environmentally safe ways
to dispose of old equipment.
Summary
In this section you:
•
Learned how the science of ergonomics helps us to use
computers correctly to avoid physically injury.
•
Discussed health issues and other precautions that should be
taken when using computers.
•
Discussed the effects of our computer use and disposal on the
environment and ways we can minimise this effect.
71
Module summary
In this unit, you learned:
72
•
Computer hardware is the physical part of a computer, including
its digital circuitry.
•
What the main types of personal computers are.
•
What the main parts of the computer are.
•
The common types of computer hardware, including processors,
memory, input devices and output devices.
•
What computer software is.
•
Software is divided into two broad categories: systems software
and application software.
•
A graphical user interface or GUI is designed to simplify the
work of the user whether they are using the operating system or
an application package.
•
The stages of software development are known as the program
development life cycle.
•
Computer networks are a set of computers connected together so
that they can communicate.
•
The main categories of computer networks.
•
About the use of computers and communication technology in
our everyday life.
•
The concept of copyright when applied to software and different
types of electronic information.
•
How the science of ergonomics helps us to use computers
correctly to avoid physically injury.
•
About the effects of our computer use and disposal on the
environment and ways we can minimise the negative effects.
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