caltecacademy.comcaltecacademy.com/notes/s.4/s ,2, 3 4 computer theory... · web viewtable of...

TOBBY OKOL ECAT Tel: 0787401800/0751269627, E-mail: [email protected]

TABLE OF CONTENTS

TOPIC 1: INTRODUCTION TO COMPUTERS……………………………………..………2

TOPIC 2: COMPUTER HARDWARE……………………………………………….………47

TOPIC 3: COMPUTER SOFTWARE……………………………………………..….…….110

TOPIC 4: WORD PROCESSING…………………………………………...….……………137

TOPIC 5: SPREAD SHEET…………………………………………………..…………..….141

TOPIC 6: PRESENTATION………………………………………………..…………..……147

TOPIC 7: DATABASE……………………………………………………...………….......…149

TOPIC 8: WEB SITE DESIGNING………………………………………..……….….……156

TOPIC 9: WINDOWS ENVORONMENT…………………………………………….……166

TOPIC 10: SYSTEM START-UP AND CONFIGURATION…………………..…………174

TOPIC 11: COMPUTER COMMUNICATION AND NETWORKING……………….....183

TOPIC 12: ELEMENTARY COMPUTER PROGRAMMING………………………...…276

TOPIC 13: TRENDS IN COMPUTING………………………………………………….…285

COMPUTER ABBREVIATIONS AND GLOSSARY………………………………...……325

1


TOPIC 1:

INTRODUCTION TO COMPUTING

Introduction to Computers

Etymologically, the term computer is derived from a Latin word “Computare” meaning a

calculating machine or a programmable machine. Therefore a computer can be defined as a

multipurpose, automatic and electronic device that allows the user to input data, store data and

information in its own memory, process input data and output information for future reference.

It is an electronic device that converts raw data into meaningful information. It can also be

described as an automatic machine made up of electronic and electromechanical device which

manipulates and processes data.

Characteristics of Modern computers

Speed

Computers are quite fast in their operation in that their speed is measured in Millions of

Instructions per Second (MIPS) or Megahertz (MHz). Inside the computer's system unit, the

processing occurs through electronic circuits. Data and program instructions travel through these

circuits at speeds close to the speed of light. Many computers process billions or trillions of

operations in a single second.

Accuracy

Computers are known to be accurate. They can process large amounts of data and generate error-

free results, provided the data entered is correct. They hardly make any mistake. They are

capable of detecting and correcting any mistakes made. It follows therefore, that if wrong data is

fed into the computer, the resulting output will be incorrect.

2


Storage

For a computer to be able to work it must have a work space where data is stored before being

processed or where information is stored before being output to particular devices. This storage

space is known as Memory.

Automation

Computers work automatically. They do not need any supervision in order to perform

programmed routines. This is because of the instructions (programs) installed in them.

Diligence (Consistency)

Computers have the ability to perform the same task over and over for neither a long time

without getting bored and with nor mistakes (errors).

Artificial intelligence

Computers are artificially intelligent. They can respond to requests given to them and provide

solutions. This is because of the programs installed in them. Evidence is seen in industrial

Robots.

Versatility/Flexibility

Computers are capable of performing different kinds of tasks provided the specified task is

followed in a proper order.

Basic Parts of a Computer

A computer is made up of a collection of different parts that are interconnected and working

together in order to function a single entry.

3


Monitor

A monitor is a display device that looks like an ordinary television screen used for displaying

information in visual form such as text, graphics, still and moving pictures. There are two types

of the monitors: cathode ray tube (CRT) monitors and Liquid crystal display (LCD) monitors.

Without a monitor, it is very difficult to see what you enter into the computer

Keyboard

A keyboard is a primary input and control device of a computer that allows the computer user to

enter data and commands into the computer. It has a typewriter area that looks like or similar to a

typewriter keyboard.

Mouse

This is a handheld input pointing device that controls the movement of a pointer on the screen. It

is a device used to point and select items on the computer screen. It is small, oblong and

connected to the system unit by a long connecting cable. It is an extension of your hand since

you cannot touch inside the computer.

System unit

The system unities a rectangular box-like case placed on or under the table that houses both

internal and external electronic components of a computer.

Factors to consider when acquiring a computer

The cost of the computer

The storage capacity

The processing speed

User needs

Portability

The monitor size

Connectivity

Maintenance cost

Availability of hardware and software in the market

4


System requirements

Multimedia capability

Terminologies and concepts applied to computing today

There are many terminologies used in the field of computing. Below are some of the basic ones:

Computer studies: This is a subject which deals with the features of computers, ways and

methods of using computers so as to provide a basis for understanding the impact of

computers on individuals, organization and society.

Computer literacy: computer literacy is the nontechnical understanding of microcomputer,

how to use simple applications and of the role played by computers in the society. Computer

literacy includes an awareness of computers, knowledge about computers and interaction

with computers.

Notice: Awareness means being aware of the importance, versatility and the potential of

computers for their good and ill in the society. Knowledge, means learning what computers

are and how they work. Interaction means learning to use computer for some simple

applications.

Information Communication Technology (COMPUTER): This is the combination of

telephone lines, computers, hardwires and software which enable users to create access,

store, manipulate and transmit information.

Information Technology (IT): This is the study that involves the software and hardware to

design, implement and support a computer-based information system.

Data: Data refers to raw facts and figures that are processed into information. Examples are

numbers, exams scores, musical notes, words, and symbols etc.

Data entry

It is the act of in putting data into the computer. This is done by the help of input devices like

keyboard, mouse etc.

Information: Information is the processed data which is organized, meaningful and useful. Is

manipulated/ processed data e.g., Apple, boy, cat, report, letter, comments, grades etc.

5


Byte

A byte is a unit of computer memory or digital information that consists of eight binary digits

(bits).

NB. 1 byte stores 1 character.

Binary

The number system used to represent digital information in computers where data is expressed

by combinations of the digits 0 and 1, corresponding to power states "off" and "on" respectively.

Computer Memory

This is a store for digital Data, processed information and programs in a computer system.

RAM (Random Access Memory) is temporary and volatile working memory that contains all

the work in progress, since the user last saved to disk. RAM changes constantly as the computer

is used for different tasks and is lost when the computer is switched off.

Reasons why we study computer in secondary schools

1. To acquire general knowledge and skills in the use of computers and related technologies.

2. To use the acquired knowledge in computer studies to enhance learning other subjects.

3. To understand important issues of a technology based society and exhibit them using

computers.

4. To exhibit basic computer skills that is required for employment.

5. To acquire knowledge as a foundation for further studies in computer technology.

6. To use a variety of computer technologies to assess, analyze and interpret information.

7. To promote creative knowledge for problem solving such as multidimensional problems

that requires imagination and sensitivity to a variety of fields

8. To promote critical and analytical thinking for proactive (hands-on) solution such as

vaccine research, environmental protection, business, entertainment and education.

9. To create awareness in learners about the developments and emerging issues concerning

computing and society

6


10. To get jobs such as computer operators, Computer technicians, System analysts,

Computer programmers, Software engineers, Computer engineers, Database

administrators, website masters, Graphic designers, IT Teachers, etc.

History and evolution of computers

The word Evolution comes from the Latin word, ‘ēvolvō’ which literally means; to ‘unroll’, or to

‘unfold’.

Evolution of computers refers to the historical developments through which computers and

technology have passed, from the time they started to exist in ancient forms to their current state.

Knowledge about the history/evolution of computers gives us a deeper understanding of the

origin and the gradual Mechanical to Electro-mechanical to Electronic technological changes,

which have brought about the kind of computers we see today, and helps us to predict Computer

how they will be in future.

Origin of calculation

Although electronic computers have become popular in the past 4-5 decades, man had

always had the urge to solve problems and manage information/data in a much easier way.

As a result, various mechanical devices were invented by man to help him fulfill his needs.

So the origin of computing started with the early man who used fingers, stones, sticks, marks on

walls, sand, etc.

The word ‘compute’ was derived from two Latin words; ‘com’, which means ‘together’ and

‘putare’, which means ‘add, calculate, count, or estimate’.

Over the centuries, people have developed an amazing variety of data processing tools and

techniques. Some of these devices could not work on their own they required some human

assistance in order to carry out their tasks effectively

Examples of ancient counting and calculating devices include: The abacus, Napier’s bones, the

Slide rule.

7


Calculation era

The Abacus

Napier Bones

Slide Rule

Abacus (3000BC)

This was the first computing device used in the 16th Century in China and Japan to compute

volume for thousands of years Before Christ.

It consisted of a rectangular wooden rack which had horizontal wires running from left to

right. Theses wires had beads stuck on them. It is these beads that were used for simple

addition and subtraction.

Napier’s bones (1617)

It was invented by a Scottish Mathematician called John Napier in1617. It was made of ivory

rods which looked like bones and they had numbers painted on them.

It was used to solve mathematical problems involving multiplication, subtraction, division and

addition. This could be done by sliding the bones back and forth.

Slide rule

Slide rule was invented by British mathematician called William Oughfred in 1620 as the first

kind of analog computer. This device was made up of two sets of scales marked in logarithms.

This Mechanical Computer could also solve mathematical problems involving multiplication,

division, addition and subtraction. All these computations could be done by sliding its cursor.

8


Mechanical era (1623 – 1945)

Before 1642, all computation was done by humans. Manual devices used then could just aid the

users to keep track of numbers as they did the computing.

In the Mechanical Era (Period) however, machines and gears did the computations. This era also

saw the development of the world's first computer programmer Ada Byron Lovelace (1815-

1852)

The popular mechanical developments of computers in this period include:

Blaise Pascal's Calculator (1642)

Leibniz’s Stepped Reckoner (1694)

Jacquard’s Loom (1801)

Charles Babbage’s Analytical & Difference Engine (1834).

Hollerith’s Tabulator (1860)

Blaise Pascal's Calculator (1642),

Blaise Pascal calculator was invented in around1642 by Blaise to help his father who was a Tax

Collector to simplify his calculation from the taxes collected daily.

It was the first mechanical adding machine which used a system of gears and wheels. It consisted

of toothed wheels which were numbered from 0-9. When one wheel moved past the notch of

another wheel, it would cause it to rotate automatically.

9


Leibniz Stepped Reckoner(1694)

The Stepped Reckoner was a digital mechanical calculator invented by German mathematician

Gottfried Wilhelm Leibniz around 1672 and completed in 1694.

It was the first calculator that could perform all four arithmetic operations: addition, subtraction,

multiplication and division including square roots.

Jacquard Weaving Loom (1801)

Jacquard weaving loom was developed by Joseph Marie Jacquard of France in1801 who made

the first successful automatic draw loom by means of a series of instructions given to the threads

by a punched card system.

It was a textile weaving equipment whose instructions were stored on punched paper cards.

These instructions could automatically control this machine. He developed it with the intention

of devising means of simplifying the weaving process of complex patterns within the textile

industry.

Babbage’s Analytical Engine and Difference Engine

Charles Babbage from England is considered the first person to propose the concept of the

modern computer hence called the Father of Computing who partially invented two machines

that is different and analytical machines.

10


Difference Engine

In 1823, with the help of a grant from the British Government, he partially built a steam driven

mechanical calculator called the Difference Engine to compute logarithms tables.

Analytical Engine

He then thought of an Analytical engine which was a mechanical steam driven mechanical

machine which had many characteristics of a modern computer such as input, storage, control,

mill, and output. It uses punched cards to restore its data and instructions.

The First Computer Programmer

Lady Augusta Ada Byron Lovelace (1815-1852) is the first world computer programmer.

In 1842, Ada was asked to write a scientific interpretation of the Analytical Engine and its

operations. These extensive writings on the Analytical Engine later became known as the first

explanation of computer programming.

Notice; In between 1890 to 1946, there were another three inventions that took place. Among the

popular developments of computers within this era include;

Hollerith's tabulating machine (1890)

Howard Aiken’s Harvard Mark I (1944)

Program “debugging” (1944-1946)

Hollerith’s Tabulator

Dr. Herman Hollerith (1860 –1929) was an American statistician who developed a mechanical

tabulator based on punched cards to rapidly tabulate statistics from millions of pieces of data.

He decided to use punched cards to represent the data gathered for the USA population census of

1890, and to read and collate this data using an automatic machine.

Hollerith’s machine used a set of spring loaded wires suspended over the punched card reader.

When the wires were pressed onto the card, punched holes allowed wires to complete electric

circuits. The cards were coded for age, state of residence, gender, and other information

It was a hand operated computer which used punched card for storing and tabulating data. It

allowed the 1890 US census to be completed in less than three years.

11


It is said that before the introduction of this computer, it had taken the Bureau seven years to

compile the results but with this computer, it took the Bureau few months to compile the

results of 1890census.

He then left the census Bureau to start a business Firm (company) to produce punched card

machines. He called his company Dr. Hollerith’s Tabulating Machine Company. He later

named it the International Business Machine Corporation (IBM), the present day computer

manufacturer.

Howard Aiken’s Harvard Mark I (1944)

Howard Aiken Harvard Mark was a professor at Harvard University who was supported by IBM

to build an electro-mechanical computer which began computations for the U.S. Navy Bureau of

Ships.

The computer was called the Automatic Sequence Controlled Calculator – (ASCC) by IBM but

Harvard renamed it the Mark I.

It was very reliable, much more so than early electronic computers. The computer had

mechanical relays (switches) which flip-flopped back and forth to represent mathematical data.

It was huge, weighting some 35 tons with 500 miles of wiring.

The First Computer Bug

Dr. Grace Murray Hopper was a lady in the U.S. Navy Bureau of Ships, who worked with

Howard Aiken from 1944 and used his machine for gunnery and ballistics calculation

12


One day, the program she was running gave incorrect results and, upon examination, a moth was

found blocking one of the relays.

The bug was removed and the program performed to perfection. Since then, a program error in a

computer has been called a bug.

Debugging is a process of finding and correcting errors, in a computer program or a piece of

electronic hardware.

The Electronic era

The electronic computer generations

A computer generation refers development and accumulation of computer technology over

the years. Computers have gone through five (5) stages during their development each

generation is characterized by dramatic improvements in;

Technology to build the computer

Internal organization of the computer

Programming languages used.

The physical setup of computer i.e. the size

Increase in performance capabilities

The setback of the computers

FIRST COMPUTER GENERATION (1946 – 1956: vacuum tube)

Technological innovations

Vacuum tubes which were used for power distribution and internal operations

Magnetic drums which were used for storage

Punched cards for input and output

Characteristics of first computer generation

They had limited primary memory, a maximum of 2000bytes (2KB) of RAM

13


Programming was done in machine code.

They had a speed of 10 kilo instructions per second.

They consumed a lot of power.

They gave off a lot of heat.

They were very expensive

They had maintenance problems and needed a stand by technician.

They were very heavy (about 30tons)

They were very big (almost of a size of a room)

They had no operating system.

Examples of first computer generation

ENIAC (Electronic Numeric Integrator and Computer)

UNIVAC (Universal Automatic Computer)

EDVAC (Electronic Discrete Variable Automatic Computer)

IBM 650 (International Business Machine)

SECOND COMPUTER GENERATION (1957 – 1963: Transistor)


Transistors which were used for power distribution and internal operations

Magnetic core memories for storage

High level programming languages such as FORTRAN (Formula Translation,

COBOL (Common Business Oriented Language)

Super computers such as LARC and IBM 7030

Characteristics of second computer generation

Speed of operation increased to 200,000 – 300,000 instructions per second.

They generated less heat and consumed less power compared to their predecessors.

They became more reliable compared to the first generation computers.

The computers became smaller in size.

Computers became less expensive.

They had no operating system.

The primary memory increased to 32KB of RAM

14


Examples of second computer generation

NCR 501

CDC – 6600 mainframe computer

IBM 7030

TRADIC

IBM 7030

LARC (Livermore Atomic Research Computer)

THIRD COMPUTER GENERATION (1964 – 1979: Integrated circuits)


Integrated Circuits (ICs) for power distribution and internal operations

ICs were made by combining several transistors onto a single chip

Magnetic disks for storage

Production of the first mini computers

Introduction of the first operating systems

Characteristics of third generation computers

Introduction of simple programming languages like BASIC (Beginners All purpose

Symbolic Instruction Code)

Computers greatly reduced in size compared to their predecessors.

Computers became reliable, smaller in size, cheap and consumed little power

which made them popular.

The keyboards and monitors replaced punched cards for input and output.

Magnetic hard disks were developed for storage purposes

Memory size expanded to approximately 2 megabytes of RAM

Speed increased to 5 million instructions per second

Integrated Circuits consumed a lower electric power.

The noise produced by the computers reduced drastically

Examples of third computer generation

IBM 360 series

IBM 370

15

A microprocessor


PDP-11

8-bit microcomputers

FOURTH COMPUTER GENERATION (1979-1989: Microprocessor)


Development of the Large Scale Integration Circuits and

Very Large Integration Circuits which led to the invention of

microprocessor

Development of the first microcomputers

Characteristics of fourth generation computer

Introduction of microprocessor that led to the development of micro and mini computers

Introduction of 404 Intel chip

Primary memory increased in size to 128MB of RAM

The speed accelerated to 50 million instructions per second

Computers became more powerful and cheap

Introduction of robotic technology

There was limited artificial intelligence and expert system

Introduction of a wide variety of software

Development of programming languages which are easy to use which resemble

human languages like C, C+, C++ etc.

Direct use of input and output devices like keyboards, mice etc to provide a more

natural user interface

Examples of fourth computer generation computers

Mainframe computers such as; IBM308, and Amdah580

Computers with processors 8088, 802886, 80386

Apple Macintosh

FIFTH COMPUTER GENERATION (1990 – Present: Artificial intelligence)


Use of artificial intelligence

Production of Robots

Characteristics of fifth computer generation computers

16


Development of powerful and intelligent computers with the ability to see, listen, talk

and think started.

Innovation of biometric systems

Development of wireless communication

Increased use of wireless communication through the use of mobile phones

Computer hardware and software costs and sizes decreased drastically.

Development of networking technologies

Emerging telecommunication and computing technology

Use of Very large microprocessor circuits in parallel processing

Use of highly sophisticated operating systems

Innovation of CCTV for security purposes

Introduction of flash memory for data storage

Use of robots most especially in industries

Artificial Intelligence is a group of related technologies that attempt to develop machines

to emulate human like qualities such as learning, reasoning, communicating, seeing and

hearing.

Artificial intelligence includes:

Games playing: programming computers to play games such as chess and checkers

Expert Systems: programming computers to make decisions in real-life situations

(for example, some expert systems help doctors diagnose diseases based on

symptoms)

Natural Language processing: programming computers to understand natural

human languages

Neural Networks: Systems that simulate intelligence by attempting to reproduce the

types of physical connections that occur in animal brains

Robotics: programming computers to see and hear and react to other sensory stimuli

Computers of preceding/former generations.

Computer Generations and associated technologies

17


Generation Technology

First Generation Vacuum tubes

Second generation Transistors

Third generation Integrated circuits

Fourth generation Microprocessor

Fifth generation Artificial Intelligence

Uses of computers in the society

Below are some of the fields where we come in contact with computers.

1) Education

2) Research

3) Business

4) Health

5) Communication

6) Security/ Military

7) Home

8) Entertainment / leisure

9) Bank

10) Industry

11) Government

12) Transport

13) Farming

14) Supermarkets

Education

Education is one of the fields in society where computers have a wide-spread usage.

Students use computers and appropriate software to learn at their own pace. This learning

is known as Computer Assisted Learning (CAL).

Computers are use as learning aids.

Through use of computers and internet, distance learning has been possible.

Computer are use for educative entertainment

They are used by researchers to quickly gather and analyze experimental data.

Students are using computers to do school- related tasks like designing posters during

campaigns, publishing school newsletters etc.

Teachers are using computers and other related IT equipment to present teaching

materials in a more interesting way.

18


They use them to do internet research and enrich their notes or to keep up to date

information

In the advanced education systems, teachers use computers to deliver their lessons.

Teachers are using computers to compile and analyze student’s performance.

Computers are used to simulate experiments and other real life situations by teachers.

Computers are used in school libraries to take record of the stock of books and the

borrowers of the books.

School bursars are using computers to compile data concerning finances and payments of

institutions’ students and staff.

Organizations such as examination boards are using computers to mark answer scripts.

Most schools today are adopting the school administration and management systems

(SAMS) for keeping records about students and producing report cards and other related

documents.

School secretaries are using computers to quickly produce exams, and other

administrative documents.

School administrators are using computers to keep records of the employees personal

data

School administrators are using computers for communication purposes

Computers that are connected to internet have enable teachers and students to have access

to education information.

Computers have simplified registration of candidates more easily through e-registration.

Research

The use of computers have made searching the literature and references easier through

use of electronic databases on the World Wide Web.

Computers have tools such as Spell checking, cut-and-paste, etc., which make compiling

and editing research work easier.

Computers have a lot of statistical software available for performing calculations and

analysing the collected research data.

19


Computers allow data obtained from the research to be easily stored in softcopies as word

documents or excel spread sheets.

Computers allow research work to be converted to Portable Document Format (PDF) and

published to the World Wide Web.

Business

Computer has enable e-commerce business trisections to take place.

Computer has played a very important role in effective management and running of

business activities such as data management and data processing.

Computer has enabled easy calculation and decision making capabilities in the

commercial world.

Computers gadgets are helpful in inventory control and management in business

especially in good stocking, storage details and goods distribution.

Computer has enables business sectors to carry out advertisements and marketing of

goods and services.

Computer has enable customer care and services possible for example the use of Toll free

mobile communications for customers with the service providers. For instance may

business companies use SMS (Short Messaging Services) to reach out to their customers

Computers are very important in accounts and Pay roll management.

Business premises are using computer equipments to enhance their security for example

the use of CCTV cameras, sensor, voice recognition equipment, smart cards etc.

Business companies can use the internet to carry out research on quality and genuinity of

products.

Health

Computers are used to maintain patient‘s records in hospitals, clinics and other health

centers.

Computers are used to monitor patients ‘vital signs in hospitals, at home and clinics.

Computers are used to carry out computer – assisted medical tests in clinics and

hospitals.

Computers are used in diagnosing medical conditions of patients.

Doctors and other medical workers are using computers to carry out research about new

medicine and diseases.

20


Computers are used during implanting of computerized devices (i.e. Pace makers e.g.

heart) that allow patients to live longer.

Computes are used to control computer – controlled devices that require great precision

during operations such as laser eye surgery and heart surgery.

Computers are used by experienced doctors and surgeons to train others through

computer – aided surgery prior to performing surgery on live humans.

Modern hospitals and health centers are using computer assisted technology in baby

incubators to artificially grow babies.

The security of the hospitals, properties, and the patients is ensured by high end computer

devices such as CCTV cameras, sensors etc.

Communication

In telecommunication industry every telephone exchange relies on computers to switch

incoming and outgoing calls.

In the multimedia industry such as TV stations, Radio station, program managers keep

computer terminals on their desks to record urgent and important news.

E-mail: Electronic Mail sent from one person to another using connected computer helps

a lot in the area of communication.

Tele Conferencing and Video Conferencing enable people in different locations to

conduct meeting as if they are in the same location

Computers are used for Faxing that is sending an image of a document electronically.

Computers are use to send voice, image, text and data though Telephones and mobile cell

phones

Large population are using computers to communicate to one another via social network

such as face book, what sap, twitter etc

Security

Computers are highly used in fighting against crime by using digital forensic

(investigation involving crime scene) and CCTV cameras.

Security officers are using computer related devices such as Biometric devices to

identifying criminals.

Computers are highly used by army by gathering electronic news, detecting and tracking

of gadgets by using radar systems, warning systems and military laser.

21


Computers are essential in online communication by the military agencies

Computers are used in training and educating military forces especially with skills and

vital details regarding military tactics.

Computers are used to design and to test new security system

Security agencies use the phones and internet tapping techniques to track down crimes.

Traffic Police uses computer-controlled traffic lights to control traffic flow and speed on

the roads by using speed sensors to find over speeding drivers.

Homes

Many people are using computers for shopping purposes because they provide them

with lists of shopping items as well as prices and electronic fund transfer facilities.

People use computers in homes to pay bills through the payment by phone services

(PPS).

People use computers for education and research from home example online studies

People use computers in homes for communicating with friends and relatives via e-

mails, telephones, chat rooms, etc.

Many people are using computers to store family records such as names of family

members, family background, etc.

Computers are used by students and other learners in doing home assignments.

Entertainment

Computers are used to play music.

They are also used to play movies and videos which help in entertaining people

People use computers in playing modern computer games such as solitaire, Tetris, Free

Cell, Packman etc.

Computers are used in composing and editing video and audio clips.

Computers are also used in Cinema halls and podiums for faster instant audio and video

playback and presentation though projectors.

Bank

The use of computer related device like ATM (Automated Teller Machine) has enable

clients to draw their money with a lot of ease; ATM allows client to;

Make deposits of cash and cheques

Withdraw cash

22


Transfer money between accounts

Obtain account balances.

Computers are used to carry out online banking. They are used to transfer money

electronically among different accounts, apply for loans, and obtain bank statements,

account balances and credit card statements.

Computers are use for keeping record of all the banks’ clients in terms of their personal

data, account numbers, and their deposits and withdrawals on their respective accounts.

Computers are used to run Magnetic Ink Character Recognition (MICR) to process

cheques.

They are used to run microfilm and microfiche to store transaction records.

Computer related device like counting device is use for counting notes (money).

Computer related device such as CCTV cameras and sensors are use to ensure security in

banking environment.

Industry

Computers of all kinds are widely used for the daily operations in industries.

In Manufacturing Industries/Factories, Computers are used to make the production and

sometimes packaging processes faster.

Computers are used for online communication with different industries and businessmen.

Computers are used to manage large volumes of financial transactions within the

industries.

Computer driven machines such as robots are used to carry out repetitive tasks, lift

heavy equipment, and carry out tasks which require a high degree of precision.

They are used for research about new stock especially through the use of the internet.

Government

Computers are highly used in many government ministries such as finance, education,

etc, to store government records.

Computers are also used to improve the efficiency of work within the civil service.

Computers are used for easy communication between governmental institutions.

They are used for easy planning and budgeting for governments.

Computers are use to carry out statistical analysis of data such as population census bio

data

23


Government is using computer related devices such as CCTV to monitor all the

government premises for security purposes.

Computers have enabled the government in creating a national data base bank such as

that of national IDs, country population, number of civil servants, and number of students

in both government and private institutions for proper planning.

With the use of computer, the auditing department of government can easily monitor

public expenditure and finance in various government agencies.

With the use of COMPUTERs, the national electoral commission is able to carry out

democratic process such as national voter registration exercise, designing and printing of

voters cards and in coordinating of the tallying exercise nationally.

Transport

For Air transport, computers are used at the airports to take record of all the flights and

passengers for each and every place that will fly off or land at that Airport.

Used for security check-Ups at the Airports, e.g. to check whether one is smuggling in

or out weapons for war, drugs, etc.

While inside the Aeroplane, computers are used to give the pilot sense of direction by

indicating how high he is flying, the temperatures, the pressure and weather conditions

of the space in which he is flying. They also show some physical features which could

obstruct the planes movements.

In the cars, there is speedometer, which determines the speed at which the car is

moving.

Computer related devices especially satellite is use for tracking the lost cars

In a ship, computers are used to guide the captain movements while he sails. By

showing the landscape of the sea bed, the captain is able to draw the right direction and

bearing in which he should sail the sheep.

Farming institutions

Computers are use for keeping records of farm, customer details and sales.

Computers connected to the internet are use for carrying out research about new

technology in farming.

Use of mobile money services in paying and receiving payment for goods and services by

24


the farmers or farming institutions

Computers are use for branding of farm products.

Super markets

Use of bar code reader in reading serial numbers on packaged products.

Creating a data base and keeping customers records.

Computer related device like counting device is use for counting notes (money).

Use of CCTV cameras and sensors in ensuring security in the supermarket.

Computers are use for creating and printing customer receipts after purchase of items.

Computers are use for inventory management such as stock taking.

Computer care and safety

The computer laboratory

A computer laboratory is a room that has been especially prepared to facilitate installation of

computers and to provide a safe conducive environment for teaching and learning computer

studies. This is a place where computers are set for a particular task. While in the laboratory a

teacher should work closely with students to see that they master basic techniques.

Computer Literacy

Computer literacy is the nontechnical understanding of microcomputer, how to use simple

applications and of the role played by computers in the society.

It is the knowledge and ability to use computers and related technologies with a range of

skills covering levels from elementary use of programming and advanced problem solving.

The major goal of computer literacy is to promote the information culture, abstract

thinking, and ability to use computer skills for professional purposes in the future.

Computer literacy includes an awareness of computers, knowkedge about computers and

interaction with computers.

Awareness that is being aware of the importance, versatility and the potential of computers

for their good and ill in the society

Knowledge; learning what computers are and how they work

Interaction that is learing to use computer for some simple applications

Goals of computer Literacy

25


To enable people to learn and use computer programs with minimal help. To enable people of all ages an edge in both their career and education To expose knowledge and skills To employ in formations To express ideas compellingly To act ethically

Computer literacy involves having both the basic skills & intermediate skills.

Basic skills include;

Ability to start / switch on a computer (boot) Ability to use the mouse & interact with screen objects Being able to use the computer key board Ability to open & locate files Ability to shut down a computer properly. etc

Intermediate skills include;

1. Functional knowledge of word processing2. Functional knowledge of spreadsheets3. Functional knowledge of presentation software.4. Ability to use the email5. Ability to use the internet 6. Ability to install and uninstall software.

Computer Laboratory equipments and tools and their functions

Air conditioner: Regulates room temperature Bugler proofing: Prevents unauthorized access in the computer

laboratory. Woolen carpet: Absorbs dust & Shock. Toolkit: Used to store necessary tools required for computer

maintenance. Dust blower: Used to blow off dust from system unit components. Routers, modems gateways: connect the computers to the network.

26


A gaseous fire extinguisher: To prevent fire from spreading in case of a power outbreak.

Surge protector: This is an appliance that protects a computer from voltage spikes.

Curtains: These protect computers from direct sunlight. Dust covers: these are pieces of clothes covered on the computers after use

to prevent dust. Anti glare filters: these are covered onto the monitors to reduce on the

effect of bright light onto the retina. Water proof covers: Safeguards computer hardware from contact with

water & moisture Lightening conductor: prevent lightening from striking the computers. CCTV camera (closed circuit television camera): Monitor security of the

laboratory. Mouse pads: allows proper movement of the mouse as well as preventing

dust from entering the mouse sensor. Factors to consider when preparing a computer laboratory

Security of computer programs and other resources.

Reliability of the source of power

The number of computer to be installed and the available floor space.

The maximum number of users that the laboratory can accommodate.

Availability of fire fighting equipments

Availability of first aids kit

The room should be well ventilated

The room should be dust free environment

27


Typical computer laboratory

After establishment of the computer laboratory the number of safety precaution and practices

need to be observed in order to avoid accidental injuries to users, damage or lack of Conducive

environment for teaching and learning.

Safety precautions are measures to be put in place to prevent damages of computers and

equipments meanwhile safety practices are activities to be perform regularly to prevent damages

in the computer laboratory.

Therefore the following safety precautions and practices must be put into considerations;

1) Physical securityThis involves all activities done to eliminate the physical access by unauthorized people into the computer laboratory.

Ways of ensuring Physical security

1. Burglar proofing the lab.2. Locking the laboratory with a strong lock3. Employing a Security personnel4. Backing up information both onsite & offsite5. Installing an Alarm security systems6. Limiting access to computer ports

2) Software security

This involves all activities done to prevent computer software from being damaged by viruses and accessed illegally by hackers.

This can be done by;

28


a) Installing a strong Antivirus

b) Installing Anti spy ware

c) Installing Firewalls

d) Creating passwords

e) Separating users accounts

f) Software updating and upgrading

3) Electric power securityUnstable electric power supply can lead to damaging of electric equipments.To prevent damage due to electricity;

1) Use of surge protectors2) Use of uninterruptible power supply3) Providing a standby generator4) Use of good quality strong cables to connect computers.5) Proper insulation of cables to avoid the danger of exposing the users to

electric shock and power interruption.6) Connect all devices which use electricity to power regulators. These

regulators include; Uninterruptible Power Supply (UPS) Stabilizers etc. 7) Make sure that the sockets, extension cables, power cables and other

related electrical gardgets are properly connected and they are in good working conditions.

8) Also avoid over loading of sockets and having very many devices plugged into a single power outlet.

N.B .The major functions of ups are;

It regulates the amount of power entering into the device. To safely turn off the computerTo temporarily supply power to enable the user to complete work at handTo supply power to continue working when power goes offIt provides a power backup which can keep power for some time.

Fire outbreak in the computer labTo prevent fire from catching other equipments, the following should be place in a

29


computer lab;1) Fire extinguishers2) Smoke detectors3) First aid boxes 4) Air-conditioning.

Causes of fire outbreak in the computer labShort circuits due to Poor wiring of electric cablesUnstable power supplyPouring water onto the electric socketsPoor quality power cablesThunder strike / lighteningUnnecessary moving of equipment in the laboratory

Ways by which fire accidents can be prevented laboratory.a) By proper wiring of electric cables to prevent short circuitsb) By Installing power surge protectors such as UPS c) By Installing a lightening conductor on the laboratoryd) By avoiding food and water in the computer laboratorye) Avoid using computers during heavy rains.4) Security cameras (CCTV)

Installed Video surveillance systems inside and outside the computer lab to monitor and record criminals who vandalize or steal from the computer lab such as CCTV cameras (closed-circuit television) is a video camera that transmit a signal to a specific place on a limited set of monitors.Consider installing a security alarm at a strategic point in case of a breakage.

5) First aid kit

A first aid kit or first aid box is a collection of supplies and equipment for use in giving first aid to computer users in case of any accident during computer usage. so;

It is recommended that all kits are in a clean, water proof container to keep the contents safe and aseptic.

Ensure that the first aid kit has all the contents such as adhesive 30


bandages, regular strength pain medication, and low grade disinfectant. First aid kits must be checked regularly and restocked if any items are

damaged or expired.6) Fire extinguishersFire extinguisher is a portable device that discharges a jet of liquid, foam or gas to put off fire. It is normally filled with carbon dioxide gas which is used to extinguish fire.

Ensure that fire extinguisher is fixed in the computer lab in case of any emergency fire outbreak.

It is essential to always refill the fire extinguishers after a stipulated period of time.

It is also essential that all computer users are taught how to use fire extinguishers.

7) Air conditioningAir conditioning is the process of changing air temperature and humidity within an area to amore comfort condition. The machine used to modify the the air condition of a place is known as Air Conditioner or Air Con (AC). It is a machine designed to change air temperature and humidity within an area to a more comfort condition. It is used for cooling as well as heating depending on the air properties at a given time.

Ensure the installation of air conditioner to regulate temperature.

There must be a good air circulation in the computer room to avoid suffocation and overheating

Ensuring that the room has enough ventilation points like windows.

Avoiding overcrowding of either machine or users

Ensure proper ventilation to avoid damage by overheating The room must be well lit to reduce eye strain that eventually leads to

headache, stress and fatigue. Over bright wall paints reflect too much light causing eye strain.

Data risks in the computer laboratory

31


1) Data theft

2) Virus attack

3) Erroneous deletion of files

4) Failure to save files

5) Information theft and piracy

6) Cracking of software.

7) Damaging of the storage media

Ways of safeguarding data in a computer lab

1. Protecting files with a password

2. Backing up of data.

3. Separating users accounts on the computer

4. Installing strong antivirus software.

5. Scanning all storage media before opening them

How can a computer lab be safely used?

1. Plug all computer equipments into a surge protector to avoid power spikes and surges in electrical power which can damage the electrical equipments.

2. Set up a network layer firewall.

3. Setup weekly updates or weekly updates

4. Install an up-to-date anti-virus soft ware.

5. Back up your computers on regular basis.

6. Use the hard disc clean up and defragmentation utilities regularly.

7. Dust the computer screens regularly with a thin soft microfiber cloth

8. Clean the computer lab regularly

Computer laboratory rules and regulations

1. Do not open inside part of computer when cleaning, this should be done by a trained

personnel.

32


2. All CDS used for installation of programs and backups should be kept safely in Disk banks

and away from sun shine and magnetic media.

3. In areas where power fluctuates it is important to use a stabilizer or UPS to ensure steady

input power to the computer system.

4. Peripheral devices like printers should be serviced regularly.

5. Installation and updating of an antivirus should be done regularly.

6. All foreign storage devices like floppy disks, flash disks, and external hard disks should be

scanned from computer viruses.

7. Backup copies should be done regularly to ensure that there is no data loss made.

8. If you have unwanted copies of print outs these should be destroyed because data is not

supposed to fall in unauthorized hand.

9. Always lock up all the premises where computers are kept to prevent theft and intruders.

10. Minimize the number of user/visitors to your installation and do not allow any outsider to

your server apart from network administrator.

11. Always keep important information with passwords.

12. Never leave computers on after use and you should follow the systematic way of shutting

down.

13. Playing of computer games are prohibited from the lam.

Care for computer user and ergonomics

There are a number of health problems that are associated with improper and too long use of

computers and its related devices.

1. Musculoskeletal problems:

Muscle soreness and muscle fatigue are the most common complaints of regular computer users.

Back pain, chest pain, pain or numbness in arms, shoulder and feet top the list. These types of

problems mainly occur because your posture while using the computer is not correct. Either you

are sitting on an uncomfortable chair or your workstation is not supportive of correct posture.

33


Practical tips

Adjust your chair and desk such that your screen is either at your eye level or lower. Sit with

your back straight and legs perpendicular to the floor with feet resting flat on the floor. Your

elbows should rest at the sides.

Take mini breaks from work and stretch a bit or go for a short walk.

2. Repetitive stress injury

Pain in the neck, shoulder, or anywhere from the shoulder to fingers may indicate repetitive

stress injury. When you use your muscles in an awkward position, you may experience stiffness,

pain or swelling in that area. For example, twisting the wrist to use the mouse or specific typing

technique that causes stretching of fingers or pressure on the wrist can turn really painful. One of

the disorders that affect the fingers and wrist is carpal tunnel syndrome.

Practical Tips:

Adjust the mouse besides the keyboard. Move your entire arm, while moving the mouse.

Don’t just move your wrist by fixing it at one position. Typing should be gentle. Do not fix

your wrists in a certain position while typing.

Relax your arms or stretch when you are not typing or using the mouse.

3. Vision problems

Bright light and bad glare or flickering image can strain your eyes. Constantly focusing on the

screen without blinking can cause dry eyes. Computer vision syndrome is another problem that

you may suffer from.

Practical tips

Adjust the contrast and brightness such that your eyes are not strained. You can tilt your

screen to avoid glare.

Maintain a proper distance from the screen. Look away from the screen intermittently.

Don’t forget to blink.

34


4. Headache

Because of increased muscle tension or pain in the neck at the base of the skull, headache is

common problem with computer use. Many a times, prolonged use can affect eye power which

needs vision correction. This can also result in headache.

Practical tips

Get your eye power tested if headache is a common problem with computer use.

Keep your neck straight when in front of the computer. Constantly looking down or

stretching the neck sideways can also cause pain. Take breaks in between and circle your

neck a bit to release the strain.

5. Obesity

Studies have shown that prolonged use of computers, especially in children, is the major

contributing factor of sedentary lifestyle and childhood obesity.

Practical tips:

Set limits for your children if they insist to playing computer games non-stop.

Encourage your children to play outdoor games or to take up a hobby. Involve them in extra-

curricular activities

Adults who work for 7-8 hours should avoid spending time on computer after reaching home.

Your body and mind both need to relax. Join a gym or go for evening jog and stay physically

active.

6. Stress disorders

Technology has a huge impact on our behavior and emotions. Prolonged computer use along

with other factors like poor health, work pressure and job environment can make you susceptible

to stress. Moreover, the longer you uphold the stress, the more susceptible you become to other

health issues mentioned above. It can also lead to loss of concentration, dizziness and weariness.

35


Practical tips:

Be proactive and take necessary measures to beat stress before it affects your health.

Computer ergonomics

Computer ergonomic refers to the study how people interact with computer, its related devices

and all aspects of the working environment.

Computer ergonomics includes;

Furniture design

Equipment placement

User techniques

Hardware and software designs

Total working environment

Servicing and maintaining of computers

Computer servicing refers to the act of supporting and maintaining computer such as installing, maintaining, configuring, and diagnosing computer systems and networks meanwhile Computer maintenance is the practice of keeping computers in a good state of repair. Servicing and maintaining of computers involve the following practices;

Install Antivirus Software. ...Perform Regular Software Updates. ...Keep Your Keyboard Crumb Free. ...Use a Surge ProtectorBack up data.Cleaning dust from computers vents and Fans, cables etc Organize your installation disks. ...Clean up software. Clean up your operating system (OS). Upgrade and update all the software’s.Covers all the computers and the related devices in the computer lab.

36

http://i.viglink.com/?key=6e0325d6b6b47cbf00af2152d33feebe&insertId=b1746811b2286414fb5d868ac1595e60&type=CD&exp=-100%3ACILITE%3A13&libId=jfwbl4yi01021li2000DAavwf1hnu&loc=https%3A%2F%2Fwww.techwalla.com%2Farticles%2Fwhat-is-computer-hardware-servicing&v=1&out=https%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_nkw%3Dcomputer&ref=https%3A%2F%2Fwww.google.com%2F&title=What%20Is%20Computer%20Hardware%20Servicing%3F%20%7C%20Techwalla.com&txt=%3Cspan%3Ecomputer%3C%2Fspan%3E


All the worn out devices should not be use againSoftware update refers to the Patching of the software that you have already installed.

Reasons for software updating

1. To ensure that a computer has the most up to date information possible2. To keep the computer running efficiently3. To put in place limitations & changes to the security of the product

Software upgrade refers to the replacement of a product with the newer version of the same product.

Risks involved in software & hardware upgrading

1. Incompatibility of new hardware / software with other pieces of hardware in the system

2. The new version may contain bugs causing the program to malfunction3. The new version may be not friendly to the user.

Importance of servicing and maintaining of computer

To prolong the life time of the computersTo pre-empt the problems that may render the proper performance of the computer system.To reduced Likelihood of Lost Files.To update outdated software programs such as application programs, antivirus, and operating system.It increases the speed performance of the computer by defragmenting hard drive, running spyware and virus removal programs as well as installing the latest drivers and software updates.It protection computers against threats by keeping spyware and anti-virus programs updated and running on a regular basis.To detect early problems and eradicate them before becoming big problemsTo keep premises, equipment, machines and the work environment safe and reliableIt helps to eliminate workplace hazards

37


Tools used for computer servicing, repairing and maintenanceThese are important and essential devices that enable a person to install, remove, or perform other actions on the components within a computer. These tools/devices are categorized in the followings;

Electrostatic Discharge (ESD) ToolsHand toolsDiagnostic Tools

Software Tools Cleaning Tools Disk Management Tools Protection Software Tools

Electrostatic Discharge (ESD) Tools

These are devices used to prevent electrostatic discharge damage to computer equipment. There two types of ESD tool antistatic wrist strap and the antistatic mat. The antistatic wrist strap protects computer equipment when grounded to a computer chassis. The antistatic mat protects computer equipment by preventing static electricity from accumulating on the hardware or on the technician.

Hand tools

These are tools held in the hand and operated without electricity or other power. Most tools used in the computer assembly process are small hand tools. They are available individually or as part of a computer repair toolkit. Examples of hand tool include; Flat-head screwdriver, Phillips-head screwdriver, Torx screwdriver, Crimper, Wire cutters, tweezers, Flashlight, Wire stripper, Needle-nose pliers etc

Diagnostic tools

Diagnostic tools are tools or devices used to test, diagnose, and solve hardware-related problems. Examples of diagnostic tools include;

A digital multimeter is a device that can take many types of measurements. It tests the integrity of circuits and the quality of electricity in computer components.

38


A loopback adapter, also called a loopback plug, tests the basic functionality of computer ports. The adapter is specific to the port that you want to test.

Software Tools

Like hardware tools, there are a variety of software tools that can be used to help technicians pinpoint and troubleshoot problems. Software tools helps to diagnose computer and network problems and determine which computer device is not functioning correctly. A technician must be able to use a range of software tools to diagnose problems, maintain hardware, and protect the data stored on a computer; to be able to identify which software to use in different situations.

Examples of software tools are; Disk management tools and Protection Software Tools

Disk management tools are tools that help to detect and correct disk errors, prepare a disk for data storage, and remove unwanted files.

Examples of disk management tools:

FDISK a short form for fixed disk: A command-line tool that creates and deletes partitions on a hard drive.

Disk Management Tool: used to initialize disks, creates partitions, and formats partitions.

Format: used to prepare a hard drive to store information. ScanDisk or CHKDSK: used to checks the integrity of files and folders on a

hard drive by scanning the file system, and disk surface for physical errors. Defrag: used to optimize space on a hard drive to allow faster access to

programs and data. Disk Cleanup: used to clears space on a hard drive by searching for files

that can be safely deleted. System File Checker (SFC): A command-line tool that scans the operating

system critical files and replaces files that are corrupted.

39


Protection Software Tools: These are software tools used to protect data and the integrity of the operating system and hardware, guarding against virus attacks and to remove malicious programs.

Examples of protection software tools;

Windows security Center: it checks the status of essential security settings. The Action Center continuously checks to make sure that the software firewall and antivirus programs are running. It also ensures that automatic updates download and install automatically.Antivirus program: Protects computers against virus attacks.Antispyware program: Protects against software that sends information about web surfing habits to an attacker. Spyware can be installed without the knowledge or consent of the user.Window 7 Firewall: Runs continuously to protect against unauthorized communications to and from your computer.

Organizational Tools

These are tools used to keep accurate records and journals (documentation of work) during a busy workday. Example is work-order systems which are used by technicians to document their work.

Cleaning Tools These are tools used to keep the computer components and the work area clean and dust free environment.

Examples of computer cleaning tools are;

Clean cloth. Compressed Air Isopropyl Alcohol

Cotton Swabs Portable Vacuum Lens cleaning kit

N.B.The following parts and areas must be clean with the appropriate materials and detergents. Such parts include system unit, monitor, key board, mouse, component contacts, and working area must be clean.

40


Preventive measure during cleaning process must be put into considerations such as;

Proper handling of the computer parts not to fall down Ensuring that the appropriate tools are use and they must be in good

conditions. Before cleaning, ensure that those parts such as monitor, key board are

plug out of power. After cleaning them, plug back the power cord safely. Do not use a vacuum cleaner inside a computer or on a laptop keyboard

because the plastic parts of the vacuum cleaner build static electricity. Use little amount of water so that it does not drop inside the monitor

Keyboard Navigation and the Mouse

The keyboard

A keyboard is a primary input device made up of keys with numbers, letters, symbols and special

keys used to enter data into the computer.Each press of a key corresponds to a single written

character of text, but to produce some symbols, it requires pressing and holding several keys

simultaneously.

A keyboard is the main and most reliable computer input device which was invented by

Christopher Latham Sholes who was an American newspaper publisher .In 1866; he invented the

first practical typewriter and the QWERTY keyboard still in use today.

41


Keyboard layouts

The arrangement of the English language keyboard keys was modeled after the QWERTY type

writer keyboard developed by Christopher Sholes in 1868.

Its name was derived from the first six letters at the top of the keyboard.

NB; The alternative to the QWERTY keyboard is the Dvorak keyboard developed by Dr.

Dvorak in 1936. With the Dvorak, the most used letters are positioned in the middle row of the

keyboard, intending to reduce typing time and finger movements.

Types of keyboards

A standard computer keyboard

Wireless keyboard

Handheld keyboard

Laptop keyboard

Ergonomic keyboard

Enhanced keyboard

Parts of a computer keyboard

Functional keys

These are keys found across the top row of the keyboard. Each key is composed of letter F and a

number ranging from 1 to 12.

42


Each functional key performs a specific operation based upon the software being used.

Numeric keypad

This is an extra section to the right of the keyboard.

Navigation/Cursor/Arrow keys

These keys are used to navigate through documents and websites. They include the up, down,

left, and the right arrows.

Typewriter Keypad (Alphanumeric Keypad)

This consists of the keys in the centre of the keyboard. It has buttons with alphabetical letters and

numbers hence the name alphanumeric keypad. Most of the typing is done with these keys.

Special Keys

These are the keys that are used to perform specific functions in the computer. They include;

Shift key, Tab key, Control key, Caps Lock, Num Lock, Backspace key, Enter key, Delete key,

Alt key, etc.

Functions of some selected keys on the keyboard

i. Backspace key

It deletes the characters to the left of the cursor and moves the cursor to that position. Ctrl+

Backspace key removes the whole word to the left of the cursor.

ii. Caps Lock Key

43


A toggle key that, when activated, causes all alphabetic characters to be uppercase. To facilitate

continuous typing in upper case when activated.

iii. Delete Key

To remove the character, space, text or word to the right of the cursor position

Ctrl+Del remove the whole word to the right of the cursor position.

Sometimes labeled Del, deletes the character at the current cursor position, or the selected object,

but does not move the cursor.

For graphics-based applications, the Delete key deletes the characters to the right of the insertion

point.

iv. Space bar

To create space

For alignment

Moving the cursor to the next line

Pausing music in some music programmes e.g. Power DVD,

Playing games e.g. in pinball

Resizing or closing the current window with a modifier key e.g. Ctrl Key +Spacebar

Helps in scrolling in some web browsers when used with Shift Key

v. Shift Key

Activates second function of different keys

Activates sticky keys

Selects files and folders in specific order

Modifies function Keys e.g. Shift + F1 = F13 and Shift +F2=F14.

Anchors the insertion pointer in word processors

Used in modifying the mouse behavior while using a web browser

vi. Ctrl key

Short for Control, this key is used in conjunction with other keys to produce control characters.

The meaning of each control character depends on which program is running.

44


vii. Enter Key

Used to enter commands or to move the cursor to the beginning of the next line

viii. Esc Key

Short for Escape, this key is used to send special codes to devices and to exit (or escape) from

programs and tasks.

ix. Alt key

Short for Alternate, this key is like a second control key.

x. Arrow Keys

Most keyboards have four arrow keys that enable you to move the cursor (or insertion point) up,

down, right, or left. Used in conjunction with the Shift or Alt keys, the arrow keys can move the

cursor more than one position at a time, but this depends on which program is running.

Advantages of using a computer keyboard

1. Keyboards are very common (commonly supplied with computers)

2. Entering data and commands with keyboard is faster as compared to the mouse

3. Keyboards are more reliable

4. They are used for computer gaming

5. A keyboard is used to control computer

Disadvantages of using computer keyboard

1. It takes a lot of time to practice in order to type quickly

2. Keys can easily become faulty due to dust.

3. Some keyboards keys are very hard to press, causing fingers to hurt.

Computer key board combination and their uses

Alt+Tab: Switch between open programs or windows

Ctrl+A: Select all items in a document or window

Alt+F4: Close the active item, or exit the active program

Ctrl+S: Save the current file or document.

45


Ctrl+C: Copy the selected item

Ctrl+X: Cut the selected item

Ctrl+V: Paste the selected item

Ctrl+Z: Undo an action

F1: Get help

F2: Rename a selected item.

Tips for using your keyboard safely

Using keyboard improperly can cause soreness or injury to your wrists, hands, and arms,

particularly if you use your computer for long periods of time. To avoid this:

Place your keyboard at elbow level. Your upper arms should be relaxed at your sides.

Center your keyboard in front of you. If your keyboard has a numeric keypad, you can

use the spacebar as the centering point.

Type with your hands and wrists floating above the keyboard, so that you can use your

whole arm to reach for distant keys instead of stretching your fingers.

Avoid resting your palms or wrists on any type of surface while typing. If your keyboard

has a palm rest, use it only during breaks from typing.

While typing, use a light touch and keep your wrists straight.

When you're not typing, relax your arms and hands.

Take short breaks from computer use every 15 to 20 minutes.

The computer mouse

A mouse is a handheld operated input device used to position the cursor, point, select and move

objects on the computer screen.

Wheel Mouse housing

Secondary/Right mouse button

Connecting cable Primary/Left mouse button

46


The top and sides of a mouse have one to four buttons; some also have a small wheel. The

bottom of a mouse is flat and contains a mechanism, such as a ball or a light that detects

movement of the mouse.

TYPES OF MICE

1. Mechanical mouse

A mechanical mouse has a rubber or metal ball on its underside. Electronic circuits in the mouse

translate the movement of the mouse into signals the computer can process.

2. Optical mouse

Most computer users today have some type of optical mouse, which has no moving mechanical

parts inside. Instead, an optical mouse uses devices that emit and sense light to detect the mouse's

movement.

Some use optical sensors, and others use a laser. An optical mouse is more precise than a

mechanical mouse and does not require cleaning as does a mechanical mouse, but is more

expensive.

3. Air mouse

Is a motion-sensing mouse that, in addition to the typical buttons, allows you to control objects,

media players, and slide shows by moving the mouse in predetermined directions through the air.

For example, raising the mouse up would increase the volume on your media player.

4. Cordless mouse

The cordless mouse is a lot better than a normal mouse. It reduces the amount of work space

needed to move the mouse around.

This mouse runs on a battery. When you move the mouse it sends an infrared beam to a sensor

which interprets it causing the pointer to move

Mechanical mouse Optical mouse

47


Air mouse Cordless mouse

Basic activities performed by a mouse piece

1. Point

Means positioning the pointer on the screen to an object such as a button, a menu, an icon, a link,

or text

2. Click

Means pressing and releasing the primary mouse button, which selects or deselects items on the

screen or starts a program or program feature.

3. Right-click

Involves pressing and releasing the secondary mouse button, which displays a shortcut menu

4. Double-click

Means pressing and releasing quickly the primary mouse button twice without moving the

mouse; this action starts a program or program feature.

5. Drag

Means pointing to an item, holding down the primary mouse button, moving the item to the

desired location on the screen and then releasing the mouse button

6. Right-drag

Displays a shortcut menu after moving an object from one location to another

7. Rotate wheel (Scrolling)

Involves rolling the wheel forward or backward that scrolls up or down a few lines

Advantages of using a computer mouse

It is user friendly

48


It is faster to select items

It is easy and convenient to use with graphical user interface

It is good for limited desk space

Disadvantages of using a computer mouse

Difficult to input ex using a mouse

A mouse in not accurate enough for drawings

It is very slow to issue command using a mouse

The computer system Unit

The system unit is a box-like case that houses the electronic components such as the

motherboard, the disks, processor, memory, drive bays, the power supply and cooling systems

and other electronic components of the computer that are used to process data. All other

computer system devices, such as the monitor, keyboard, and mouse, are linked either directly or

indirectly into the system unit.

A drive bay is a rectangular opening inside the system unit that typically holds disk drives.

49


The computer system unit provides the following functions

1. It contains the framework to support a computer’s internal components and provide an

enclosure for added protection.

2. They provide an environment designed to keep the internal components cool.

A system unit contains the following electronic components;

Power Supply,

Mother board,

CPU,

System Clock,

Ports and connections

50


Internal cables

Storage drives (HDD,FDD,ODD)

RAM chips, Expansions lots,

Bus lines,

Ports,

PC slots and Cards,

Peripheral

The motherboard

The mother board is a single circuit board that provides the path through which the processor

communicates with memory components, other components, and peripheral devices.

It is the main circuit board in the system unit. It houses the CPU chip, Main memory chips and

expansion slots into which other circuit board can be inserted for the expansion of the computer

system.

Basic parts of a computer motherboard

An expansion slot is a socket on the motherboard that can hold an adapter card. An adapter card,

also called expansion card, is a circuit board that increases the capabilities of the system or

provides connections to peripherals. Some motherboards include all necessary capabilities and

do not require adapter cards.

Adapter cards are used for many supplemental capabilities, such as more memory, higher-

quality sound devices, a modem, extra ports, or graphics capabilities.

Commonly used adapter cards and their functions

Adapter Card Purpose

Sound card Connects speakers or a microphone

51


MIDI card Connects musical instruments

Network interface card

(NIC)

Connects other computers

Video card Connects a monitor

USB card Connects USB devices

TV tuner card Allows viewing of television channels

Video capture card Connects a video camera

Modem card Converts telephone or cable analog signals to digital and vice

versa

FireWire card Connects FireWire devices

N.B.Plug and Play (pnp) is the ability of the computer to recognize a new device and assists

in the installation of the device by down loading the necessary drivers automatically and

checking for conflicts with other devices.

It refers to the computer’s capability to automatically configure adapter cards and other

peripherals as you install them when the computer is still running.

Buses

The bus is a common electrical path that enables data flow between the various system

components. A bus allows the various devices inside and attached to the system unit to

communicate with each other.

Buses are used to transfer bits;

From input devices to memory,

From memory to the CPU,

From the CPU to memory,

52


From memory to output or storage devices

All buses consist of three parts:

1. A control bus is part of the system bus, used

by CPUs for communicating with other devices within the computer. A control bus

carries commands from the CPU and returns status signals from the devices.

2. Address bus carries the information about the device with which the CPU is

communicating

3. Data bus carries the actual data being processed,

Types of buses

1. System bus which is part of the mother board and connects the CPU to main memory.

2. Expansion bus which allows the CPU to communicate with peripheral devices

Examples of expansion buses and their functions

Bus Function

ISA (Industry Standard Architecture) bus It connects devices such as modem & sound cards, mouse

PCI (Peripheral Component Interconnect) bus To connect sound and network cards to the motherboard

PCI Express (PCIs) bus To connect a computer to one or more peripheral devices.

The Accelerated Graphics Port (AGP) bus It enable 3-D graphics to display quickly on ordinary

personal computers

Universal Serial Bus (USB) To define cables, connectors and protocols for connection,

communication, and power supply between personal

computers and their peripheral devices.

Fire Wire bus It is used to connect multiple devices to a computer to

enable high-speed transfers between computers.

PC Card bus It expands the bus bandwidthand throughput to 32 bits at

33MHz

Ports

53

https://en.wikipedia.org/wiki/Communications_protocol

https://whatis.techtarget.com/definition/3-D-three-dimensions-or-three-dimensional

https://en.wikipedia.org/wiki/Bus_(computing)

https://en.wikipedia.org/wiki/Address_bus

https://en.wikipedia.org/wiki/Central_processing_unit

https://en.wikipedia.org/wiki/System_bus


A port is a socket on the outside of the system unit that is connected to an expansion board on the

inside of the system unit. It is the interface or point of attachment to the system unit. Peripheral

devices, such as;

A keyboard, monitor, printer, mouse, digital camera, microphone, etc. often attaches by a cable

to a port on the system unit. Most of the time, ports are located on the back of the system unit,

but they also can be placed on the front.

Types of ports

Port Purpose

Serial port It is used to connect serial devices to the computer

and capable of transmitting one bit at a time.

Parallel port Parallel port is a parallel interface used for

connecting external devicesuch as a printers.

USB (Universal Serial Bus) port USB ports allow USB devices to be connected to

each other with and transfer digital data

54

https://www.webopedia.com/TERM/P/printer.html

https://www.webopedia.com/TERM/D/device.html


over USB cables.

Fire Wire port (IEEE 1394port) Is a port that provides a high-speed connection

between a computer and peripheral devices

MIDI (Musical Instrument Digital Interface) port Is an electronic connector that connect a wide

variety of electronic musical instruments, computers,

and related music and audio devices

eSATA (external Serial Advanced Technology

Attachment) port

Is a connector accessible from outside the computer,

to provide a signal (but not power) connection for

external storage device

PCMCIA (Personal Computer Memory Card

International Association) port.It is a configuration port used for computer parallel

communication peripheral interface, designed

for laptop computers.

SCSI (Small Computer System Interface) ports A SCSI connector is used to connect computer parts

that use a system called SCSI to communicate with

each other

55

https://en.wikipedia.org/wiki/SCSI

https://en.wikipedia.org/wiki/Laptop

https://en.wikipedia.org/wiki/Parallel_communication

https://en.wikipedia.org/wiki/Parallel_communication

https://en.wikipedia.org/wiki/Computer

https://en.wikipedia.org/wiki/Electronic_musical_instrument

https://en.wikipedia.org/wiki/Electrical_connector


IrDA (Infrared Data Association) port It is a port that allows the user to transfer data from

one device to another without any cables.

Bluetooth port A Bluetooth port enables connections for Bluetooth-

enabled devices for synchronizing. There are two

types of ports: incoming and outgoing. The incoming

port enables the device to receive connections from

Bluetooth devices while the outgoing port makes

connections to Bluetooth devices.

VGA (Video Graphics Adapter) port VGA) connector is a three-row 15-pin DE-

15 connector used to connect an analog PC monitor

to a PC or laptop

Ps/2 port The PS/2 port is a 6-pin mini-DIN connector used for

connecting keyboards and mice to a PC compatible

computer system

Network Port A network port is an endpoint of communication in

an operating system, which identifies a

56

https://en.wikipedia.org/wiki/Operating_system

https://en.wikipedia.org/wiki/D-subminiature

https://en.wikipedia.org/wiki/D-subminiature


specific process or a type of network service running

on that system

Audio port Audio port is used to link the computer's sound

hardware with speakers, microphone, headsets or

other audio equipments.

NB: Hot plugging / hot Swapping; is the ability to add or remove devices while a computer is

running.

Power supply unit

It provides the necessary electrical power to make the PC operate. The power supply converts

alternating current (AC) power from the wall outlet into direct current (DC) power which is a

lower voltage.

Memory chips (RAM& ROM)

These are devices that provides vast amount of memory required by the computer. Read Only

Memory (ROM) chips are located on the mother board. They contain instructions that the CPU

can access directly. ROM chips stores basic instructions for booting the computer and loading

the operating system.

Random Access Memory (RAM) is the temporary storage for data and programs that are being

accessed by the CPU.

Cooling systems (fans)

Case fans are devices installed inside the system unit to make the cooling process more efficient.

A heat sink draws heat away from the core of the CPU. A fan at top of the heat sink moves heat

away from the CPU. Cooling a system is necessary to protect the internal components from

damaged and also to fasten the working of the computer system.

57

https://en.wikipedia.org/wiki/Network_service

https://en.wikipedia.org/wiki/Process_(computing)


Internal cables

Hardware inside the system unit connects to the mother board by use of internal cables.

The computer clock

Every computer contains two types of clocks; Hardware clock (Real-time clock, RTC), and

System clock / Virtual Clock

Hardware Clock

It is a clock that maintains the time and date.

It is from this clock that the system clock is set when a computer is switched-on.

It runs continuously whether the computer is on or off.

It is maintained by use of a CMOS (Complementary Metal Oxide Semi-conductor)

battery.

System Clock

The system clock is a small crystal chip that is used by the CPU to synchronize the timing of all

computer operations. The faster the clock, the more instructions the CPU can execute per second.

The speed at which a processor executes instructions is called clock speed which is measured by

the number of ticks per second.

Peripheral Devices;

Peripherals are the generic name given to all input, output, and secondary that are part of a

computer system. These are any external devices that attach to the system unit. They include

keyboard, mouse, printers, scanners etc.

Central processing unit (CPU)

Central processing unit is an electronic device that interprets and carries out the basic

instructions that tell the computer how to work. It is the “Brain” of the computer.

Categories of computers

Computers are categorized according to how the processed data is

58


represented.

Therefore they are categorized into three categories i.e.

(a) Analog Computers

(b) Digital Computers

(c) Hybrid Computers

Analog Computers

Analog computers are computers used to process data in a continuous form. These

computers operate by measuring rather than counting.

These computers employ physical variables like temperature, voltage, weight, pressure,

speed to represent the quantities being manipulated.

Analog computers are used in engineering and scientific applications, weather

forecasting, green house controls and in manufacturing industries.

Analog data is data that is continuous in nature such as temperature, voltage, pressure

& weight

Examples of analog computers include; Thermometers, Voltmeters, Tide

predictors, Speedometers etc

Digital Computers

These are computers that process data in discrete form or value. Discrete values are

numbers that can be defined like, 1, 2, 3, etc.

They can count and process data in a more accurate way. They convert data into

digits) binary digits of 0 &1). These are computers used for business and scientific

applications.

Digital data is data that is discrete in nature such as 0 and 1.

Examples of digital computers include; Digital Watches, personal

computers, mobile phones.

Advantages of digital data over analog data

59


Digital data is more accurate that analog data

Digital data occupies less storage space than analog data

Digital data is transmitted faster than analog data

Digital data produces clearer output that analog data

Hybrid Computers

These are computers that have the combined features of both the digital and

analog computers.

Hybrid computers measure physical quantities and represent it values in a digital form.

The analog computer takes measurements in a continuous form and converts it into

numbers and supplied to digital components in the system.

Examples of hybrid computers include; digital petrol pumps, computer devices used in

hospitals to measure parameters such as patients temperature, blood pressure etc.

Differences between Digital and Analog

Digital Analog

More Accurate. Less accurate compared to digital.

Use binary code to represent information. Use a changing phenomenon due to environment

Have no interference and background noise. Have interference and background noise.Generally fast and cheap. Generally slow.Data does not degrade over time during transmission.

Data degrades over time during transmission.

Data can be compressed. Data can’t be compressed.Classification of computers

Computers are classified according to the following functionalities;

Purpose/Function

Size

Processor power

Classification of computers by Purpose

These are computer classified according to the work they are designed for, and they are further

classified into two classes;

60


Special Purpose Computers

These are computers that are designed to handle only one particular task. Their form of operation

is limited in nature.

Currently, these computers are employed in devices like missiles. These will never do anything

like word processing.

Examples of special computers include; Digital watches, Pocket calculators, Lifts in

buildings, Missiles

General Purpose Computers

These are computers designed to carry out a wide variety of tasks.

Among the variety of tasks perform by general purpose computers include performing

calculations, keep date and time, process word documents, store databases, tabulate

student‘s grades, play games, etc.

Examples of general purpose computers include;

Stand alone computers

Stand alone computers are computers that are not connected to a network and is capable of

performing the operations in the information processing cycle.

Networked computers (NC);

These are computers designed specifically to connect to a network especially the internet.

Real time systems

These are systems that process data without significant delay such

as;

Anti – missile defense systems,

Airplane landing control systems

Flight simulation systems

Electronic fund transfer systems

61


Ticket reservation systems.

Classification of computers by size

According to size or capacity, we base on the physical size the number of people the computers

can accommodate at the same time. Digital computers can be grouped into four classes as

follows:

.

Super Computers

Characteristics of super computers

They have a very high processing speed

They have a very high storage capacity

They are the biggest types of computers

They are very expensive computer

They are the most powerful computers

They are used for complex and sophisticated mathematical calculations

Examples of Super Computers: Cyber 70, IBM 4381 etc.

Mainframe Computers

These are powerful computers used mainly by large organizations for bulk data processing such

as census, and financial transaction processing.

They are very large and expensive computers capable of supporting hundreds of users

simultaneously.

These computers are designed to handle huge volumes of data and information.

Characteristics of mainframe computers

They can accommodate many users at a time.

62


They have a high storage capacity

They are bigger than mini computers

They have a high processing speed

They support a wide range of peripheral devices

They are sensitive to changes in temperature such as humidity; dust hence should be kept

in a well air conditioned room

Examples of Mainframe Computers; ICL 39 series, and CDC Cyber series

Mini Computers

Mini computers are multi-user computers that lie in the middle range between mainframe

computers and the smallest single-user systems.

They are similar to main frames but they are smaller in size, support a limited number of

peripheral devices connected to them.

They have a lower speed, have lesser storage capacity, and support fewer numbers of users at the

same time than compared to main frames

They can be used for applications such as accounts, payroll, stock control, etc.

They are used in industries to control the manufacturing process e.g. Car

assemblies, UNEB, UEB, etc.

Characteristics of mini computers

They are smaller in size that mainframe computers

They support limited peripheral devices

They have lower storage capacity

They have a very low processing speed

They support limited number of users between 50-200

Examples of minicomputer include; PDRS, PDP-11, IBM AS400 range, VAX. etc.

Micro Computers /Personal Computers (PCs)

Microcomputers are computers that can perform its entire input, process, output and storage

activities y itself.

63


Microcomputers are smaller than mini computers and are a single user capacity.

The keyboard, system unit and monitor of a micro computer can be used by one person at a time.

They are mostly used computers in day-to-day work.

Characteristics of Micro computers

They have smaller memory capacity

They use large scale interpreted circuits

They are relatively cheap, portable and convenient

They are smaller than any other computers

They are single user computers with network technology

They support wide few peripheral devices

They have high processing speed

They are computers with a micro processor as its central processing unit

Examples of micro computers include;

Desktop Computers

These are microcomputers designed to be stationed in one place preferably on top of the desk.

They can be used in offices, computer labs. They are the standard computers.

Tower Model Computers

These computers have a tall and narrow system unit that usually sits on the floor.

Laptop Computers

These are portable personal computers which is small enough to fit on the lap such that even if

one is in a bus or plane can still work like one on a desk top.

Notebook Computer;

This looks like a laptop but it is much smaller than a laptop.

Palmtop Computers / Personal Digital Assistants (PDAs)

These are hand held computers used by people who are ever on move by carrying it in the

palms.

Classification of computers by processor power

Micro Computers can be classified by their microprocessor model name or model number.

64


The leading processor chip manufacturers for personal computers are Intel, AMD, IBM, and

Motorola.

Due to the rapid changes in technology processor power is also rapidly increasing. Computers

are getting faster and faster each time a new microprocessor chip is introduced.

Examples of Microprocessors

The most common types of processor power are:-

80286,

80386,

Pentium I,

Pentium II,

Pentium III,

Pentium IV,

Pentium Duo core,

Core 2 Quad,

Celeron,

Celeron D,

Xeon,

Opteron,

Athlon,

Itanium

Intel Dual Core

Intel Dual core i3

Intel Dual core i5

Intel Dual core i7 etc.

The unit for measuring the processing power is the Hertz.

Due to the rapid changes in technology, processor power is also rapidly increasing.

Computers are getting faster and faster each year. The higher the processing powers the

faster the computer. Earlier computers had processing power of less than 0.4MIPS but today

15 MIPS is the least. (MIPS: Millions of Instructions per Second).

Computer information system

A computer system is a functional unit consisting of integrated assembly of devices, centered

on at least one processing mechanism which are used to input, process, store, and output data

and information. A computer system consists of interrelated organs or parts which function

together for the same goal. Failure of one of the system components may imply failure for the

whole system.

Components of a computer information system;

Hardware

Software

65


Data

Information

Users (Human ware)

Procedures

Communication

Hardware

Hardware comprises of the electronic and the electromechanical parts of the computer.

Hardware devices are the physical and tangible of a computer. Examples include;

Input devices

Processing devices

Storage devices

Output devices

Communication devices

Software

Software is electronic instructions that tell the computer how to perform a task. These are a

series of programs (instructions) that tell the computer what and how to work.

Data

Data refers to raw facts and figures that are processed into information. Data is the foundation

for information

Information

Information is the processed data which is organized, meaningful and useful.

Importance of information

In all organizations, managers depend on information to make decisions.

They also base on information when planning for the organizations.

They base on information when analyzing their performance.

They depend on information to forecast the likely outcomes of certain actions.

Information helps in discovering the past, present and future.

Procedures

66


These are rules or guidelines for people to follow when using hardware, software, and data. They

normally appear in documentation materials which contain guides for using the hardware and

software.

Users (human ware)

Human ware refers to the people who operate and initialize instructions to the computer system.

It is the most important component of a computer system

They design and develop computer systems, operate the computer hardware, create the

software, and establish procedures for carrying out tasks.

There are two categories of computer users;

Ordinary users are people without much technical knowledge of computers but uses computers

to produce information for professional or personal tasks, enhance learning, or have fun.

Professional users are people who had formal education in the technical aspects of

computers such as;

Computer programmer

System analyst

System administrator

Database administrator

Network administrator

Importance of users

Data entry

Manipulating the computer

system

Programming the computer

Administering the network

Analyzing the computer

system, etc.

Communication

Communication refers to the process of transferring data and information from one place to

another digitally.

Computer communication allows sharing of hardware, software and transfer of data and

information stored among computers in a network like Internet. It also facilitate communications

between people e.g. through e-mail. Examples include; Cables, Switches, Routers Modems, etc

Importance of communications

Linking up computer devices and computers

67


Enabling the flow of data

Enabling the flow of information

Enabling the flow of instructions

Networking of computers

Data and Information

Data

Data refers to raw facts and figures that are processed into information. Data is the foundation

for information. Data is classified into two categories that input data and output. Examples of

data include;

letters (e.g., a, b, c, ...)words and symbolsNumbersexamination scoresmusical notesNames e.g. Moses

Information

Information is the processed data which is organized, meaningful and useful. Is manipulated/

processed data, examples include,

Words (e.g., apple, boy, cat)a report, a letter, an essaya mathematical formulacomments, gradesa piece of music, a song

Information processing Cycle

This is a series of activities that take place in transforming data into information. It involves

input, processing, output and storage of information.

68INPUT


The four basic stages of information processing cycle include;-

Input of data

This is a means by which data is entered into the processing system by the use of the keyboard,

mouse, touch pad, microphone, scanner etc. It involves collecting of data from their sources and

recording it onto some media such as paper, questioners, voice or video recording and preparing

of the collected data by copying, grouping, or arranging of data in a more convenient way for

input.

Storage of data and information

This process includes storing of data and information. When data in entered, it is stored

temporarily by RAM to be process by CPU and when the process of execution is done, the

processed data is stored in storage devices such as floppy disks, flash disk, flash memory, disc

drives, and hard drives etc which are later retrieved for use references.

Processing of data

This involves the manipulation or arithmetic & logical operations of the input data. The

processing stage is based on the user’s instructions. The central processing Unit (CPU) is the one

responsible for processing of data.

Output of information

69

DATA

PROCESSING OF DATA BY

CPU

MEMORY

Storage Area (RAM & ROM)

INFORMATIONOUTPUTTT


Output is a means processed data is obtained and can be viewed in a readable form example as a

report. Devices commonly used by which for output of data include monitor screen, printer,

speakers etc.

Notice: In summary, there are four major functions of a computer:

1. Accepting data

2. Storage of data and information

3. Processing of data

4. Producing output

Advantages of using computer systems for information processing

1. Enormous amounts of data can be stored permanently for future use.

2. Computers can process large amount of data and generate error free results provided the

data entered is correct.

3. Large numbers of tasks can be performed at very fast processing speed.

4. The degree of accuracy is very high.

5. Efficiency and productivity in information processing can be realized.

6. The operations like deletion and modification of data can be done very easily.

7. Tasks can be completed with minimal human intervention

8. It allows for the decisions and logical comparisons.

9. It allows for the creation of standard libraries.

10. Sharing of data and information is possible when the computers have communication

capabilities.

11. It is possible to obtain the results in the formatted form.

12. The management can observe information and trends more quickly.

Disadvantages of using computer for information processing

1. The initial investment costs are high, such as costs on computers, skilled labor force and

software.

2. Mechanical faults within the computer system or damage may lead to system failure.

3. Extra costs are required to employ specialized staff or personnel to operate the computers

and even design the data processing system.

4. Face to face interaction among the staff may be reduced.

70


5. There is easier transmission of malicious codes or viruses in a network environment.

6. Some jobs may be lost due to computerization and thus may render the morale of the

workers.

7. The networking environment is susceptible to human abuse.

8. Extra costs may be needed in the security to protect personnel and staff from preying

eyes such as the use of sensor, CCTV cameras.

TOPIC 2:

COMPUTER HARDWARE

Introduction to Computer Hardware

Computer hardware refers to the physical and tangible components of a computer. These are

devices you can see, touch and feel.

Categories of Computer hardwires

1) Input hardware

2) Storage hardware

3) Processing hardware

4) Output hardware

5) Communication (Networking) hardware

Input hardware

Input is any data or program instructions people enter into the memory of a computer.

Terms related to input

Data

This is collection of raw unorganized facts, and figures to be processed by a computer.

Information

Information is processed data that is organized, meaningful and useful.

A program

Is a series of instructions that directs a computer how to perform the tasks necessary to process

data into information; A program is written by a programmer and then store the program in a

71


file that a user can execute (run).

A command

Is an instruction given to a computer program to perform a specific action; Commands can be

issued by typing keywords, pressing special keys on the keyboard, selecting menu choices,

clicking the mouse on a graphical user interface, speaking into a microphone, or touching an area

on a screen.

A user response

Is an instruction users issue to the computer by replying to a question posed by a computer

program; A response to the question instructs the program to perform certain actions.

Input devices

These are hardware components or devices that allow the user to enter data and instructions

(programs, commands, and user responses) into the computer. Input devices translate data

and communications into a form that the computer can understand. Each input device

outputs data in a unique way depending on the type of data being input. The data may be in

form of a sound, characters, graphics etc.

Examples of input devices

Keyboard

Pointing devices

Controllers for Gaming and Media

Players

Audio Input devices

Video Input devices

Scanning devices

Reading devices

Terminals devices

Biometric Input devices

Remote control

Sensor and Remote sensor

Keyboard

A keyboard is a primary input device made up of keys with numbers; letters, symbols and

special keys used to enter data into the computer by pressing of a key corresponds to a

single written character of text.

Pointing devices

72


Pointing devices are input devices that allow you to control a pointer on the screen and interact

with computer via a graphical user interface (GUI). Examples of pointing devices include;

A Mouse

A

trackball

A touch

pad

Pointing Stick

A touch screen

A light pen

A stylus and graphics tablet

Digitizers

A Mouse

This is a hand operated device used to position the cursor, point, select and

move objects on the computer screen.

A trackball

A trackball is like an upside-down mouse. It is a stationary pointing device with a ball

mechanism on its top. It is operated by rolling the ball directly with your hand.

A touch pad

A touchpad is a small, flat, rectangular pointing device that is sensitive to pressure and motion

used to move the pointer by sliding your finger tip across the surface of the pad.

Pointing Stick

A pointing stick is a pressure-sensitive pointing device shaped like a pencil eraser used

to move the pointer by pushing the pointing stick in any direction with your finger.

A touch screen

A touch screen is a touch-sensitive input display device used by touching any items, icons,

words, pictures, numbers, letter, or locations identified on the screen.

A light pen

A light pen is a handheld input device that detects the presence of light by pressing

the light pen against the surface of the monitor screen, a special type of paper, or a

graphic tablet. It can be used for writing, drawing by taping on the flat surface

drawing by taping on the flat surface.

73


A stylus and graphics tablet

A stylus is a small metal or plastic device that looks like a tiny ink pen but uses

pressure instead of ink to write text and draw lines on a pressure sensitive screen.

Stylus pen is a pen that allows the user to draw on a digitizing tablet that mirrors the

surface area of the computer screen.

A graphics tablet is a flat, rectangular, electronic plastic board on which a stylus writes or draws

Digitizers

These are devices that look like a mouse, except that it has a glass with a cross hair in the middle.

It is used with a digitizing tablet in making maps (cartography) and architectural drawings to

accurately trace out lines on a map. They are commonly used by architects, mapmakers,

designers, artists, and home users create drawings and sketches by using a pressure-sensitive pen

or a cursor (digitizer) on a graphics tablet. A cursor looks similar to a mouse, except it has a

window with cross hairs, so that the user can see through to the tablet

A mouse

A trackball A touch pad Pointing stick

A touch screen A light pen Graphic tablet Digitizer

Controllers for Gaming and Media PlayersThese are input devices used in video games and computer games to direct

movements and actions on- screen objects. Examples of game controllers and

media players include;

Game pads,

Joysticks and wheels,

Light guns,

Dance pads

Touch sensitive pads

A game pad

74


A game pad is an input device that is used to control the movement and actions of players

and objects in video/computer games by pressing its buttons with thumbs and moving sticks

in various directions to trigger events.

Joystick and wheels

A joystick is a handheld vertical lever mounted input device with buttons called triggers used by

moving the lever in different directions to control the actions of the simulated vehicle or player

by pressing the triggers to initiate certain events.

A wheel is a steering wheel- type input device used by turning the wheel to simulate driving a

vehicle. Most wheels also include foot pedals for acceleration and braking actions.

A light gun

A light gun is one the input devices used to shoot targets and moving objects by pulling the

trigger on the weapon or an item on the computer screen.

A dance pad

A dance pad is a flat electronic input device divided into panels that users press with their feet

in response to instructions from a music video game. It is operated by stepping on the correct

panel at the correct time, following a pattern that is synchronized with the rhythm or beat of a

song.

The touch-sensitive pad

It is an input device contains buttons that are operated with a finger by scrolling through when

playing music, viewing pictures, watching videos or movies, adjusting volume, and customizing

settings.

A game pad Joystick A wheel

A light gun A dance pad

Audio input

Audio input is the process of entering any sound into the computer such as speech, music, and

75


sound effects. To enter high-quality sound into a personal computer, the computer must have a

sound card.

A sound card is a device that can be slotted into a computer to allow the use of audio

components for multimedia applications. Without a sound card, audio input and output is not

possible.

Examples of audio input devices include;

Microphones

Voice recognition equipment

Tape players,

CD/DVD players,

MIDI devices

Dictaphone etc

A microphone

A microphone is an audio input instrument used for converting sound waves into electrical

energy variations, which may then input into the computer for processing, recording or audio

playback.

Microphones are connected to the sound card in the system unit.

Voice recognition equipments (VRE)

These are audio input devices used to capture sound such as multimedia computers, tape

recorders etc .they are capable of distinguishing spoken words and then converts them into text.

Tape players

Tape player is an analog audio device that records and plays back sounds, including articulated

voices, usually using magnetic tape in a cassette, for storage.

MIDI (Musical Instrument Digital Interface)

MIDI (musical instrument digital interface) is the standard that defines how digital musical

devices represent sound electronically. MIDI devices such as electronic pianos allow users to

record and edit music to produce sound.

76


Dictaphones

Dictaphone is an electronic audio input device that allows the user to record or create spoken

words or voices that are later repeated them aloud so that they can be written down as important

notes.

Microphone CD/DVD player Voice recognition equipment

Tape player MIDI Dictaphones

Video input

Video input is the process of capturing full-motion images such as still photos, motion pictures,

graphics, and video and storing them on a computer‘s storage medium.

Video input devices are input devices used to capture and enter images such as still photos,

motion pictures, graphics, video etc. into the computer for processing.

NOTICE; To enter video from an analog device into a personal computer, the analog signal

must be converted to a digital signal by plugging a video camera or other analog video device in

a video capture port on the system unit.

Common video input devices include:

Digital camera

Digital video camera

A webcam

Film camera

Camcorder

Digital camera

77


A digital camera video input device that allows users to take pictures and store the photographed

images digitally instead of storing on a traditional film. When you take pictures, the images are

electronically stored in the camera.

Types of digital cameras

Studio cameras, Field cameras

Point-and-shoot cameras

A studio camera is a stationary camera used in professional studio work. It is the most expensive

and has the highest quality.

A field camera is a portable camera that has many lenses and other attachments. It often used by

photo journalists.

A point-and-shoot camera it is more affordable, lightweight and provides acceptable quality

photographic images for home or small business users. A point-and-shoot camera often has

features of flash, zoom, automatic focus, and special effects. Some allow users to record short

audio narrations for photographed images, record short video clips, etc.

Digital video camera

A digital video (DV) camera is an input device by contrast records video as digital signals

instead of analog signals. For a video or the image to be displayed, it requires a video capture

card to convert analogue video signals into digital signals so that the computer can understand

the images

A webcam

A Web cam, also called a PC video digital camera is a type of digital video camera that

usually sits on top of the monitor that allows users to record, edit, capture video and still

images, and make video telephone calls on the Internet. During a video telephone call, both

parties can see each other as they talk. Some laptop computers have built-in Web cams.

Webcams enable users to:

capture video and still images,

send e-mail messages with video attachments,

add live images to instant messages,

broadcast live images over the Internet,

78


and make video telephone calls

Camcorder

This is a light weight video camera that records data in digital form onto a storage device such as

a video tape.

Film cameras

Film cameras are cameras that expose photographic film to light in order to take a picture. A

film is a chemical emulsion on a plastic substrate that is sensitive to light. When exposed, an

analogous image of the scene is created within the chemical layer of the material; thus, film

cameras are analog cameras.

Digital Camera Digital video camera

Webcam Camcorder Film Camera

Advantages of a digital Camera over the ordinary film camera

They are environmental-friendly

They records massive amount of videos unlike film camera

They have user-friendly features

They store large amount of Photos

They have high Operating Speed compare to film camera

They save money for buying films.

They allow images taken to be previewed and even edited on the camera.

Unwanted images can be deleted after preview.

79


Digital cameras are best for three – dimensional objects unlike film cameras

Disadvantages of digital camera

Digital cameras are very complex because the user must know how to upload and edit

photos using a computer

Digital cameras are sensitive and susceptible to extreme conditions such as heat, extreme

cold and moisture in comparison to the old film cameras that causes their malfunctions

Digital cameras consumption power faster than film cameras. This makes it necessary to

keep a few spare batteries in hand, especially during lengthy photo sessions.

They are normally expensive than the ordinary film cameras with the same functions.

Photo printing costs are higher than that of the ordinary film cameras.

Scanning devices

These are devices that capture data directly from source documents and converts it into a digital

form that can be stored into a computer. Most of the scanning services is done by a scanner

especially optical scanners.

A scanner is a light-sensing input device that converts hardcopy documents, drawings, or

pictures to an electronic version (softcopy), which can then be stored on a disk. The electronic

version of scanned material is in the form of rows and columns of dots called a bitmap. Each dot

on a bitmap consists of one or more bits of data.

N.B. Bitmap display screen permits the computer to manipulate pixels on the screen individually

rather than, enabling software to create a greater variety of images.

Optical Scanners

Optical scanners are light-sensing input devices that can convert text, drawings, or pictures

into computer-recognizable digital data by using a form of optical recognition. In a process

called imaging, a scanner converts source documents to an electronic version, which can then

be stored on a disk and retrieved when needed.

Examples of optical scanner include

Flatbed scanner

Sheet-feed scanner

Drum scanner

Handheld scanner

80


NB: The quality of a scanner is determined by its resolution and color depth.

Advantages of scanners

Scanners provide high quality in terms of resolution for both color and black and white

documents. They also provide enough detail and resolution to handle images,

photographs, graphics and designs.

Scanners make it unnecessary to retype text or redraw images. Thus, you can reproduce a

document or picture in as little as 10 seconds, even if the original took hours or days to

produce. The scanner can make this copy without damaging the original item.

Scanners don't depend on the use of a phone line like a fax machine does. Additionally,

there is no other end that needs to receive your scanned document in order to complete a

successful transfer.

Using a scanner can also be environmentally friendly that is to say, scanners create digital

copies of documents, photos and files on your computer that you can email to other

people or store and view on your own.

Scanners are very easy to use and the ones that are built into multifunction printers today

can be used essentially without instruction. Most settings are automatically adjusted and

fine-tuned, leaving a user to only select basic options such as photograph or document, or

color versus black and white.

81


Disadvantages of scanners

Scanned output varies depending on the quality of the lens inside the scanner, the

cleanliness of the scanner’s glass, and the condition of the original documents.

Scanners are very expensive in terms of buying and maintenance such as replacement of

lambs, and lens etc

Scanners are also relatively slow, so companies and individuals users will need to

consider the time involved in scanning all of their paperwork.

Scanners can be used to fake documents. For example, one of the quickest things that can

be faked with a scanner is an ID.

Most scanners restrict you to the size of an 8.5 inch by 14 inch page of paper, or in some

cases of photo scanners, even smaller. Larger flatbed scanners are expensive, and in most

instances, you’d scan a big document, poster or other item in sections, perhaps even

having to cut or fold it, to completely scan it.

Reading devices

Reading devices are input devices that capture data from a source document, which is the

original form of the data. Examples of reading devices include optical reading devices.

Optical reading devices are devices that use a light source to read characters, marks, and codes

and convert them into digital data that a computer can process.

Examples of optical reading devices include;

Optical character recognition (OCR) Readers

Optical mark recognition (OMR) readers

Bar code readers (BCR’s)

Radio Frequency Identification (RFID) Readers

Magnetic Strip Card Reader

Magnetic Ink Character Recognition (MICR) Readers

82


Optical character recognition (OCR) Readers

Optical character recognition (OCR) is a technology that reads typewritten, computer printed, or

handwritten characters from ordinary documents and translates the images into a form that the

computer can understand.

Advantages of OCR readers

They save lot of time when using a digital file rather than paper documents

OCR allows user to copy and paste from the document itself whether that's in PDF format

or MS Word format.

They are less expensive in terms processing documents.

They allow written and printed data to be read at the same time.

Hard copies of documents can be read directly into a computer without retyping.

The characters converted can later be edited by word processing software.

Disadvantages of OCR readers

They are expensive in terms a scanner, OCR software and maintenance.

They are not completely accurate when sending text because it require proofreading

afterwards

Often don‘t work well with hand written characters or those in unusual fonts.

Optical mark recognition (OMR) readers

These are input devices that read hand-drawn marks such as small circles or rectangles. A

person places these marks on a form, such as a test, survey, or questionnaire answer sheet.

The OMR device first reads a master document, such as an answer key sheet for a test, to

record correct answers based on patterns of light; the remaining documents then are passed

through the OMR device and their patterns of light are matched against the master document.

Advantages of OMR readers

They are much faster than someone manually entering large amounts of text

83


They consistently provides unmatched accuracy when reading data

They have better recognition rate than OCR hence can read marks.

OMR have large volumes of data that can be quickly collected without the need of

specially trained staff.

Their cost of data input is small.

The chance of data errors can also be reduced because it is not necessary to type the

details for data entry.

Disadvantages of OMR readers

All documents need to be checked over carefully and then manually corrected

If the original document is of poor quality or the handwriting difficult to read, more

mistakes will occur

They are not worthy working for small amounts of text

Documents for OMR are complicated to design.

The OMR reader needs to be reprogrammed for each new document design.

It needs the person putting marks on the documents to follow the instructions precisely.

Any folding or dirt on a form may prevent the form from being read correctly.

A bar code reader

It is an optical reader that uses laser beams to read bar codes by using light patterns that pass

through the bar code lines.

A bar code is an identification code that consists of a set of vertical lines and spaces of different

widths, or a two- dimensional pattern of dots, squares, or other images. The bar code

represents some data that identifies the item and the manufacturer.

Advantages of using Bar Code Reader and Bar Codes

They allow real time data to be collected accurately and rapidly.

Bar code readers enable fast data entry operations with less error.

They are less expensive.

Bar code readers smaller and lighter compared to RFID tags and easy to use.

The process of data entry is fast and accurate.

84


Bar codes can be printed by normal printing methods.

No need to write down any key in the name of the item or its accurate price.

Disadvantages of Bar Codes and Bar Code Readers

Barcodes do not have read/write capabilities.

It requires optical line of sight (LOS) scanning.

It is labour intensive as it requires to be scanned individually.

It is less secure compare to RFID which can be easily forged.

It is susceptible to environmental damage.

Scratched or crumpled barcodes may cause problems while scanning.

Only numbers can be coded

Bar codes cannot be read directly by people.

A bar code reader may misread a bar code if there is any dirt or mark on the code.

Radio Frequency Identification (RFID) Readers

Radio-frequency identification (RFID) is a technology that uses radio waves to transfer data

from an electronic tag, attached to an object, through a reader for the purpose of identifying and

tracking the object.

Radio Frequency Identification (RFID) Readers are also used for;

tracking times of runners in a marathon;

tracking location of soldiers,

tracking employee wardrobes,

tracking airline baggage,

tracking misplaced or stolen goods;

gauging pressure and temperature of tires on a vehicle;

tracking payment as vehicles pass through booths on rollway systems;

Checking out library books, etc.

Advantages of Radio Frequency Identification (RFID) Readers

The tag does not need to be in line of sight with the receiver to be read compare to a

barcode reader

RFID tags can store a lot of information, and follow instructions

85


They have the ability to pinpoint location

RFID technology is versatile: can be smaller than a thumb tack or can be the size of a

tablet, depending on its use

Disadvantages of RFID Technology

RFID are expensive because of batteries

There still needs to be regulations about RFID guidelines

RFID can be easily intercepted, even if it Encrypted

It takes a lengthy time to program RFID devices

The external electromagnetic interference can limit the RFID remote reading.

The coverage range of RFID is limited which is about 3 meters

Magnetic Strip Card Reader

A magnetic stripe card reader is a reading device that reads the magnetic stripe on the back of

credit cards, entertainment cards, bank cards, gift cards, and other similar cards. The stripe,

which is divided in three horizontal tracks, contains information identifying you and the card

issuer.

Advantages of MICR

The processing speed for cheques are very fast

They are more secure than OCR (Optical character recognition) technology

Documents prepared for MICR are difficult to forge.

Documents can still be read after being folded or split etc.

Disadvantages of MICR

The system can only accept a few characters

MICR readers and encodes are very expensive.

86


OCR OMR

Bar code Reader RIFD

Magnetic Strip card Reader MICR

Terminals

Computer terminals are electronic or electromechanical hardware devices that are used for

entering data into, and displaying or printing data from, a computer or a computing system.

The teletype was an example of an early day hardcopy terminal, and predated the use of a

computer screen by decades.

Terminal devices consists of a monitor (output), a keyboard (input), memory, and a video card

often housed in a single unit. A variety of terminals enable both input to and output from a

remote computer system. They are devices that send and receive computer data.

87

https://en.wikipedia.org/wiki/Teletype

https://en.wikipedia.org/wiki/Computing

https://en.wikipedia.org/wiki/Computer

https://en.wikipedia.org/wiki/Computer_hardware


Categories of terminals

Dumb terminals,

Smart terminals,

Electronic Point of sales (EPOS) terminal

Electronic Fund Transfer Point of Sale (EFTPOS) terminal

Intellectual terminal

A dumb terminal

It is a terminal that has no processing power, thus, cannot function as an independent device.

A dumb terminal can enter and transmit data to, or receive and display information from, a

computer to which it is connected. It connects to a host computer that performs the

processing and then sends the output back to the dumb terminal. The host computer usually is

a server or mainframe.

A Smart terminal

In addition to a monitor and keyboard, a smart terminal also has a processor that has the

capability of performing some functions independent of the host computer.

Electronic Point of sales (EPOS) terminal

This is a type of device used to record purchases at the point where the consumer purchases the

product or service.

Electronic Fund transfer of sale (EFTPOS)

These are terminals capable of transferring funds from customer’s bank account directly to a

retail outlet’s account after reading the customer’s network

Automatic Teller Machine (ATM) is a self-service banking machine that connects

to a host computer through a network. You insert a plastic bankcard with a magnetic

strip into the ATM and enter your personal identification number (PIN), to access

88


your bank account. Some ATMs have a touch screen; others have special buttons or

keypads for entering input.

Intellectual terminal

It has a memory and a processor so that it can perform some function independent of

the host computer.

Dump Terminal Smart terminal EPOS terminal

EFTPOS terminal ATM Intellectual terminal

Biometrics input devices

Biometrics is the technology that can be used to authenticate a person's identity by

verifying personal characteristics.

Biometric devices are input devices that translate a personal characteristic into a digital

code that is compared with a digital code stored in the computer. If the digital code in the

computer does not match the personal characteristic's code, the computer denies access to

the individual.

Examples of biometric devices;

A fingerprint scanner

A face recognition system

A voice verification system

A signature verification system

An iris recognition system

Hand geometry system

89


A finger

print

scanner;

A fingerprint scanner is a device that captures curves and indentations of a finger print. Some

grocery and retail stores now use fingerprint readers as a means of payment, where the

customer's finger print is linked to a payment method such as a checking account or credit card.

A face recognition system;

It is a device that captures a live face image and compares it with a stored image to determine if

the person is a legitimate user. Some buildings uses face recognition systems to secure access to

rooms.

Law enforcement, surveillance systems, and airports use face recognition to protect the public.

Some notebook computers use this security technique to safeguard a computer. The computer

will not start unless the user is legitimate.

A voice verification system;

A voice verification system is an input device that compares a person's live speech with their

stored voice pattern.

A signature verification system;

A signature verification system recognizes the shape of your handwritten signature, as well as

measures the pressure exerted and the motion used to write the signature. Signature verification

system uses a specialized pen and tablet.

An iris recognition system;

This is a device highly used in security areas. The camera in an iris recognition system uses iris

recognition technology to read patterns in the iris of the eye.

Iris recognition systems are used by government security organizations, the military and

financial institutions that deal with highly sensitive data.

Finger print scanner Face recognition system Voice verification system

90


Signature verification system Iris recognition system Hand geometry system

Advantages of biometric systems:

Improved security

Improved customer experience

Cannot be forgotten or lost

Reduced operational costs

Disadvantages of biometric systems:

Environment and usage can affect measurements

Systems are not 100% accurate.

Require integration and/or additional hardware

Cannot be reset once compromised

Remote control

A remote control (RC) also known as a clicker, flipper, tuner, changer or converter is a small

hand-held electronic device used for controlling other devices, such as a television, radio or

audio/video recording etc. Remote controls commonly operate via infrared signals but sometimes

by radio frequency signals. The remote control controls a variety of functions such as volume,

channel, track number and other functions. Modern remote control devices often have more

controlling functions than are found on the device itself, which may have only a few primary

essential controls.

91


Remote control is an input device that emits a beam of infrared light, which carries

data signals. A remote control is primarily a convenience feature for the user, and

can allow operation of devices that are out of convenient reach for direct operation

of controls from a short distance.

Sensor and Remote sensor

A sensor is electronic device which is used to record the present or changes in something for

instance the heat sensor

Remote sensing is the process of detecting and monitoring the physical characteristics of an area

by measuring it’s reflected and emitted radiation at a distance from the targeted area then

converted to electrical signals by sensors which input them to the commuter for processing.

For examples;

1) Cameras on satellites and airplanes take images of large areas on the Earth's surface,

allowing us to see much more than we can stand on the ground.

2) Sonar systems on ships can be used to create images of the ocean floor without needing

to travel to the bottom of the ocean.

3) Cameras on satellites can be used to make images of temperature changes in the oceans.

4) Large forest fires can be mapped from space, allowing rangers to see a much larger area

than from the ground.

5) Tracking clouds to help predict the weather or watch erupting volcanoes, and help watch

for dust storms.

There are two types of remote sensing instruments (sensors);

92


Active sensors provide their own source of energy to illuminate the objects they observe.

Passive sensors, on the other hand, detect natural energy (radiation) that is emitted or reflected

by the object or scene being observed.

Various sensors can be used to measure heat, light, pressure, acidity, oxygen concentration,

water flow etc. when the sensors are located at some distance from the computer system, they are

known as Remote sensors.

Storage Hardware’s (devices)

Storage devices also known as storage medium or storage media are hardware components that

write and read data to and from storage media. They are used for storing, porting and extracting

data files and objects. These devices hold and store data, instruction, and information both

temporarily and permanently, and they can be internal or external to a computer, server or any

similar computing device.

The purpose of storage devices is to store data entered before and the results after processing.

Definition of Terminologies used in storage

1. A Storage medium is the physical material on which a computer keeps data. There is a

variety of storage media available.

2. A Storage Device reads and writes data to and from a storage medium.

3. Reading is the process in which a storage device transfers data, from a storage medium

into memory.

4. Writing is the process in which a storage device transfers data from memory to a storage

medium (saving).

5. Access time, is a measure of the amount of time it takes a storage device to locate an

item on a storage medium.

6. Transfer rate is the speed with which data, instructions, and information move to and

from a device. Transfer rates for storage are stated in KBps (kilobytes per second)

7. Throughput is the rate at which the information can be written or read from the storage

device.

8. Storage Capacity is the total amount of data or information (characters) a storage

93


medium can hold.

9. Data and information access. Data and information access is either sequential or direct

(Random) access

Sequential Access: In this, data can be accessed sequentially that is one by one from its

location.

Random Access: In this type of access, the data can be accessed directly from its location; this

type of access provides fast access of data.

Types of storage devices

There are two types of storage devices commonly used for storing data, instruction and

information;

1. Primary storage devices

2. Secondary storage devices

Primary storage devices are also known as internal memory or main memory. They are devices

which store data and instructions temporarily for immediate access and use by the computer‘s

microprocessor.

Memory refers to the area or space in the computer where programs and data reside during

computer operations. It is a temporary store or space where instructions to be executed by the

processor and the data to be processed are placed while performing the processing operation.

A computer's memory in the system unit, located physically close to the CPU (to decrease access

time), it provides the CPU with a working storage area for program instructions, data and

information.

Memory usually consists of one or more chips on the mother board or some other circuit board in

the computer. It rapidly provides the instructions and data to the CPU.

Memory stores three basic categories of items:

1. The operating system and other system software that control or maintain the computer and its

devices; 2.Application programs that carry out a specific task such as word processing;

3 The data being processed by the application programs and resulting information.

94


Types of computer memory

Volatile memory

Non – volatile memory

Volatile memory

This is the type of memory where the contents or information within the memory are lost when

the computer power is turned off. Random Access Memory (RAM) is an example of a volatile

memory. It is also called Primary memory or Main memory.

Random Access Memory (RAM) is the memory chips that are mounted directly on the

motherboard or mounted on peripheral cards that plug into the motherboard.

Characteristics of RAM

It is a temporary memory.

The user can read from it and write to it.

It loses its contents when power goes off (i.e. it is volatile)

It can be increased.

Functions of RAM

To store data and instructions awaiting processing

It stores the intermediate results of computers working before they are communicated to

their recipients.

It stores instructions which are being obeyed by the computer.

Basic types of RAM

SDRAM (Synchronous Dynamic Random Access Memory)

DRAM (Dynamic Random Access Memory) must be refreshed (or recharged) constantly

by the CPU.

SRAM (Static Random Access Memory) is faster and more reliable than any form of

DRAM. The term static refers to the fact that it does not have to be re-energized as often

as DRAM.

Magneto resistive RAM (MRAM), stores data using magnetic charges instead of

electrical charges.

MRAM has greater storage capacity, consumes less power, and has faster access times.

95


Virtual RAM (VRAM): Modern operating systems can use spare storage space on the

hard disk as if it is working memory and this is referred to as Virtual memory or Virtual

RAM

Other terms related to RAM

Cache memory

Cache memory refers to the memory where data and instructions are temporarily held for

immediate access and use by the computer’s microprocessor. A cache is a relatively small block

of very fast memory designed for speeding up the internal transfer of data and software

instructions. It is used to speed up the computing process.

Virtual memory

Virtual memory is a type of memory allocated by the operating system to function as additional

RAM. This portion of storage medium is usually got from the hard disk. The area of the hard

disk used for virtual memory is called a swap file.

A buffer;

A buffer is an area of memory or storage in which data and information is placed while waiting

to be transferred to or from an input or output device.

There are two forms of buffer

Input buffer; is used between the input device (the sending device) and the CPU (the receiving

device). The role of the input buffer is to accept data/instructions at the speed of input device,

which is comparatively slow, and remits them at the high speed of the CPU as computer inputs.

Low speed High speed

Output buffer; the output buffer is used between the CPU and the output unit. The role of the

output buffer is to accept data and instructions at the high speed of the CPU and remits them at

the low speed of the output device, to go as computer outputs.

High speed Low speed

N.B: Buffering refers to the process of using the buffer to control the speed of communication

between the CPU and peripheral devices.

Importance of the buffers

96

Input device CPU

Output put device

Input Output buffer

Input buffer


They help the operating system to carefully monitor the contents in memory.

It helps the operating system to clear these items from memory when they are no longer

required by the CPU.

Spooling

Spooling is the process of placing print jobs in a buffer instead of being sent immediately to the

printer.

Non – Volatile memory

Non volatile memory is a type of memory where contents within the memory are not lost when

power is removed from the computer. Example of a non volatile memory is Read Only Memory

(ROM)

READ ONLY MEMORY (ROM)

Read-only memory (ROM) refers to memory chips storing permanent data and instructions. The

items stored in ROM chips cannot be modified

ROM is a non – volatile, permanent type of memory found in the computer that is to say the

contents of this memory cannot be irremovable and unchangeable.

ROM chips contain permanently written data, instructions, and information recorded by

manufactures which are called firm ware. Firmware allows the computer user to read and used

information, but cannot change anything.

Characteristics of ROM

The user can read the contents of ROM but can‘t make modifications or write to it.

97


It is a permanent memory

It is a non – volatile memory.

It cannot be increased.

Types of ROM

Programmable Read Only Memory (PROM)

It is a kind of memory which can only be programmed once after it has been manufactured. Once

the data and instructions are programmed into PROM chip, the chip functions like a regular

ROM and cannot be erased or changed. It is common with CD – W (Compact - Disk Writable)

Electronically Programmable Read Only Memory (EPROM)

Is a kind of memory on which instructions can only be erased once and then reprogrammed.

Afterwards, the reprogrammed instructions can never be altered. It is common with compact disk

re –writable.

Electronically Erasable Programmable Read Only Memory (EEPROM)

It is a type of memory that enables a user to store information on it as many times as one may

desire.

The instructions remain in memory until when one may wish to alter them. It is common in

applications such as most color TVs to store TV settings such as color, contract, brightness, and

Mobile phones to store phone numbers etc

Other terms related to ROM

BIOS (Basic Input / Output System)

It resides in the ROM. It is a sequence of instructions the computer follows to load the operating

system and other files when the computer is turned on.

CMOS (Complementary Metal Oxide Semiconductor)

It is used to store configuration information about the computer. This information includes; the

amount of memory installed, types of disk drives, the types of keyboard, monitor, current date

and time e.t.c.

CMOS technology uses a CMOS battery power to retain its information even when the computer

is turned off. Its contents can be changed. It provides high speeds and consumes little power.

Flash Memory

98


Flash memory is a chip that keeps its memory when the power is shut off. It can be erased

electronically and reprogrammed. Most computers use flash memory to hold their start-up

instructions because it allows the computer easily to update its contents. Flash memory chips

also store data and programs on many mobile computers and devices, such as; Smart telephones,

Digital cameras, pagers, PDAs, Automotive devices, portable media players, digital voice

recorders, and printers, etc.

Video memory Video memory or video RAM (VREAM) chips are used to store display images for the monitor.

The amount of video memory determines how fast images appear and how many colors are

available.

Differences between RAM and ROMRAM ROM1. Volatile, temporally 1.Non Volatile, permanent

2. Contents lost when power goes off 2. Contents remain when power goes off

3. Read and Write 3. Read Only

4. Can be increased 4. Can’t be Increased

5. Not installed at Factory 5.Installed at Factory

Secondary storage devices refer to the storage media designed to retain data, instructions, and

information in a relatively permanent form. These devices are non volatile that is to say they

save data and remain intact even if the computer is turned off.

These usually have large storage capacity, and they store data permanently. They can be both

internal and external to the computer, and they include the hard disk, compact disk drive and

USB storage device.

Categories of secondary storage devices

Secondary storage devices are categorized into three groups;

Magnetic storage devices

Optical storage devices

Solid state storage devices

99


Magnetic storage devices

Magnetic storage devices are storage devices that use a magnetic head to write

data to and from a magnetized medium. Magnetic storage medium can be as

basic as a plastic tape that is coated with fine particles of a metal like the ones

found in audio recording devices.

Examples of magnetic storage devices include:

i. Magnetic tape

ii. Floppy disk,

iii. Zip and Jaz disks

iv. Hard disks

Magnetic tape

Magnetic tape is a magnetically coated ribbon of plastic capable of storing large amounts of

data and information at a low cost. Tape storage requires sequential access, i.e. data must be

accessed in the order in which it is stored. If the computer is to read data from the middle of a

tape, all the tape before the desired piece of data must be passed over consecutively. Today,

magnetic tape storage is no longer used for routine processing. To read or to write the

information in a tape, the read/write head of the tape used in which the tape rolls.

Advantages of

magnetic tapes

Magnetic tape cartridge can store large amounts of data and information up to 1 Terabyte.

Data collection can go on without interruption overnight or for an entire weekend.

Magnetic tape can be recorded over and reused repeatedly.

Magnetic tape is inexpensive and budget friendly.

Its storage is large than that of floppy disks.

It is light and portable

Disadvantages of magnetic

tapes

100


Special equipment must be purchased and set up for recording and storing data. The data

can only be read on the special equipment.

If the data is stored near a strong magnetic field or a large speaker, the tape can be

damaged.

Magnetic tape has a lifespan of 15 years. Data quality gradually erodes over time.

It is necessary to keep older tape equipment just to be able to read the stored data.

Data access is only sequential which is time wasting. That is Random data access is not

possible

Floppy disks (diskettes)

A floppy disk is a portable in expensive storage medium that consist of a thin, circular, flexible

plastic disk with a magnetic coating enclosed in a square – shaped plastic shell. They can be read

from and written to using a Floppy Disk Drive (FDD). The drive is usually designated letter A

(for a computer with only one drive).

Formatting of storage media

Formatting is the process of preparing a disk for reading and writing by organizing the disk into

storage locations called tracks and sectors.

Reasons for formatting a disk

When the disk space is full

During fresh installation

When operating system is corrupted on a disk

In case of virus infection

Procedures of formatting a disk

Click on the start button

From the options choose and click my computer

Choose on the desired disk and right click

From the popup menu click format

Then click start button

Care for floppy diskettes

- Avoid touching the disk surface

101


- Avoid bending them or putting weights on them

- Avoid exposing them to sun or heat and cold

- Keep them in dust free environments

- They should not be exposed to chemicals such as cleaning solvents.

- Keep the diskettes in their jackets.

Advantages of floppy disks

They are portable

They are cheap

Data on a floppy disk can be accessed randomly

Data on a floppy disk can be writing – protected from being changed accidently.

They can be used to transfer data from one computer to another.

Disadvantages of floppy disks

They provide less storage capacity of 1.44MB (about 500 double-space pages

of text, several digital photographs, or a small audio file) compared to the hard

disks.

They are not durable

They can easily be damaged by magnetic fields

They operate at a low speed

Can easily be lost or misplace because of their size.

They can easily infect machines with viruses.

Zip drive

The Zip drive is a medium-capacity removable disk storage system with capacities of 100 MB to

750 MB that was introduced by Iomega in late 1994. These are storage devices that were made to

store medium amount of data. Their capacity is bigger than that of floppy disks. Data access is

random /direct. They have got a faster transfer rate.

Hard disk (Fixed disk/Hard driver)

This is a metallic magnetic media housed in an air tight rigid box, found inside the computer

system unit to avoid contamination. .It is a secondary storage device that consists of one or more

platters to which data is written using a magnetic head, all inside of an air-sealed casing. A hard

102

https://www.computerhope.com/jargon/p/platter.htm

https://www.computerhope.com/jargon/s/secostor.htm


disk is a non-volatile memory hardware device that permanently stores and retrieves data on a

computer.

Internal hard disks reside in a drive bay, connect to the motherboard using an ATA, SCSI,

or SATA cable, and are powered by a connection to the power supply unit

Types of Hard Disk

Internal hard disk is a type of hard disk fixed in the system unit and usually stores the operating

system required for the computer to work.

External hard disk is a separate free-standing hard disk that connects with a cable to a USB

port or FireWire port.

A removable hard disk is a hard disk that you insert and remove from either a dock or a drive.

An Internet hard drive, also called online storage, is a service on the Web that provides storage

to computer users, usually for a minimal monthly fee.

103

https://www.computerhope.com/jargon/s/sata.htm

https://www.computerhope.com/jargon/s/scsi.htm

https://www.computerhope.com/jargon/a/ata.htm

https://www.computerhope.com/jargon/m/mothboar.htm

https://www.computerhope.com/jargon/b/bay.htm

https://www.computerhope.com/jargon/i/internal.htm

https://www.computerhope.com/jargon/h/hardware.htm

https://www.computerhope.com/jargon/n/nonvolat.htm


Parts of a hard disk

Platter: It is the area where information is written to the disk. It spins constantly as it continues

to add important data to the computer hard disk

Spindle: It helps to hold the platter in order to enable it to rotate/spin at the necessary speed

Head: It is a form of magnet that helps in recording information to the hard disk drive.

Actuator: Its use is to read and record information continuously.

Actuator arm: it allows the head to move back and forth across the disk drive as it records

information.

Actuator Axis: It allows the actuator arm to move back and forth easily.

Jumper block: Allows a cable to be connected to the power supply of the computer and to the

mother board of a computer system.

Integrated Drive Electronics (IDE) connector: Allows a cable to run from the hard disk drive

to the motherboard of the computer system.

Power connector: It provides power from the power supply

Advantages of hard disks

They provide a greater storage capacity

They are speedy i.e. the time of data access is very fast and convenient

They are cheaper than floppy disks per megabyte.

They are more reliable than floppy disks.

There are fewer chances of being misplaced because they reside

inside the system unit

The life of hard disks is quite long once in use.

Disadvantages of hard disks

They are bulky (not portable)

They are susceptible to virus attacks especially in unprotected systems.

Since they are metallic, they expand and contract depending on the temperature

changes which may lead to data loss.

May easily fail due to violent shaking(vibration)

104


Magnetic tape Floppy disk

Zip & Jaz disks Hard disk

Optical storage devices

Optical storage is any storage method in which data is written/ recorded and read by

making marks in a pattern that can be read back with the aid of light, usually a beam

of laser light using optical discs for archival or backup purposes. The reflected light

is converted into a series of bits that the computer can process.

Optical discs (devices) are flat, round, portable storage medium made of metal, plastic, and

lacquer that is written and read by a laser. N.B A lacquer is a liquid which is painted on wood or

metal and forms a hard, shiny, protective surface when it dries

In optical technology, a laser hits a layer of metallic material spread over the surface

of a disk. When data is being entered, heat from the laser produces tiny spots on the

disk surface. To read the data, the laser scans the disk, and a lens picks up different

light reflections from the various spots.

Categories of optical discs

Optical discs are categorized into three general categories;

Compact disks (CDs)

Digital Video Discs (DVDs)

Blue-ray disks

Notice: DVDs have much greater storage capacity than CDs.

105

https://searchdatabackup.techtarget.com/definition/backup

https://searchstorage.techtarget.com/definition/storage


Compact disks (CDs)

Compact disks are flat, round, portable, storage medium usually with a diameter of 12cm and

thickness of a few millimeters. The CD is designated by a letter D for the hard disk is C

Characteristics of compact disks

They store items by using microscopic pits and land that are in the middle layer of the

disk.

Data access is random /direct.

They have very fast access time.

Data transfer rate is very high.

The contents of standard CDs are written by the manufacturer and only can be read and

used.

A typical CD holds from 650 MB to 1GB of data,

Advantages of compact disks

More portable than a hard disk

Has relatively large storage (650-700MB) than diskettes

They are easy to store

They have a very fast access speed.

They are not easily attacked by viruses

Disadvantages of compact disks

Any single scratch or breakage on a CD can render the whole CD useless.

Most CDs are read only.

Care for compact disks

Always store the CD in its jacket (jewel box) when not in use.

Always hold a compact disk by its edges.

Never touch the underside of the CD

Never stack disks on top of each other

Never expose CDs to excessive heat or sunlight.

106


TYPES OF COMPACT DISKS

CD –ROM

CD –R

CD –RW

Photo CD

CD – ROM (Compact Disk - Read Only Memory)

Compact Disk - Read Only Memory is a type of optical disc that users can read but not write or

erase-hence, the name read-only. The contents of standard CD-ROMs are written or recorded by

the manufacturer and can only be read and used. Contents of a CD – ROM can‘t be modified.

CD – R (Compact Disk -Recordable)

CD-R (compact disc-recordable) is a technology that allows you to write on a compact disc using

your own computer’s CD-R drive. Once you have recorded the CD-R, you can read from it as

many times as you desire. A CD-R is a multisession optical disc which allows you to write on

part of the disc at one time and another part at a later time. However, you cannot erase the disc's

contents.

CD – RW (Compact Disk -Rewritable)

Compact Disk -Rewritable is an erasable compact disk that can be written on multiple times; to

write on a CD-RW, you must have a CD-RW drive and CD-RW software.

A Picture (Photo CD)

A photo compact disk is a type of disk that contains only digital photographic images saved in

the jpg file format; A Picture CD is a multisession disc, i.e. you can write additional data to the

disc at a later time.

The images on a Picture CD can be printed, faxed, sent via electronic mail, included in another

document, or posted to a Website. Many people use Picture CD to preserve their photos.

Qn. Differentiate between a disc and a disk

A ‘Disc’ refers to optical media, such as CD, CD-R, DVD-R, DVD-RW, etc. These are a type of

removable storage devices that can be used to store files, songs, etc. Some of these files are read-

107


only (ROM), while others allow users to burn content on it either once or multiple times,

depending on the type. These ‘discs’ are removable, meaning they can be removed or ejected

from the computer.

A ‘Disk’ is a magnetic storage device, similar to floppy disks, the disk on the computer’s hard

drive and an external hard drive. These disks are usually sealed within a plastic or metal case in

order to protect the magnetic files on it from damage. Disks are rewritable, unless they are

locked by the administrator. Disks such as the hard drives on the computer can be partitioned

into smaller volumes. Hard drives are not removable from the computer, though floppy disks and

external hard drives do not need to be placed inside the computer and can be removed.

Digital Video/ Versatile Discs (DVDs)

Digital Video/ Versatile Discs (DVDs are flat, round, portable, storage medium usually with a

diameter of 12cm and thickness of a few millimeters with high capacity storage from 4.7GB to

17GB than compact discs. They are widely used for storing and viewing movies and other data.

Types of Digital Video/ Versatile Discs (DVDs);

DVD –ROM

DVD –R

DVD +RW

DVD-RAM

Digital video disc-Read Only memory (DVD-ROM);

Digital video disc-Read only memory (DVD-ROM) is an extremely high capacity compact disc

capable of storing from 4.7 GB to 17GB; In order to read a DVD-ROM, you must have a DVD-

ROM drive, which can also read CD ROMs.

DVD – RAM (Digital Video Disk - Random Access Memory)

Digital Video Disk - Random Access Memory is a recordable and rewritable version of DVD –

ROM, which allows items to be erased and recorded on it multiple times.

DVD – R (Digital Video Disk -Recordable)

Digital Video Disk -Recordable is a recordable and rewritable version of DVD – Rom which can

108


be written once and read for many times.

DVD – RW (Digital Video Disk -Rewritable)

Digital Video Disk -Rewritable is a recordable and rewritable version of DVD – ROM which can

be written and read for many times.

Blue-ray disks

Blue-Ray disks are a

recent replacement for DVDs. A Blue-Ray disc can hold 25 - 50GB of data (a dual-layer. Blue-

Ray discs are random-access devices.

They are used in the same way as DVD-ROMs but, since they can hold more data, they are also

used to store very high-quality, high-definition (HD) video.

The 'Blue' part of Blue-Ray refers to the fact that the laser used to read the disc uses blue light

instead of red light. Blue light has a shorter wave-length than red light (used with CDs and

DVDs).

Using a blue laser allows more data to be placed closer together on a Blue-Ray disc, than on a

DVD or CD, so Blue-Ray has a much higher storage capacity than these older discs.

Solid state storage devices

The term ‘solid-state’ essentially means ‘no mechanical or moving parts’ it is abbreviated

as “SSS”

Solid state storage devices are non-volatile computer storage devices that are made from silicon

microchips used to store and retrieve digital information electronically without any involvement

of moving or mechanical parts.

They differ fundamentally from the traditional electro-mechanical storage devices that read and

write data from a rotating magnetic disk.

109

https://en.wikipedia.org/wiki/Digital_information

https://en.wikipedia.org/wiki/Non-volatile_computer_storage


Characteristics of solid state storage devices

They have no mechanical or moving parts

They are non volatile devices

They operate much faster than traditional electromechanical storage devices

They consume less power and are more resilient under physical shock.

They are very expensive

They are built on flash memory architecture

They provide a temporary storage solution for portable information.

Solid State devices provide a quick, easy, and accessible way to gather, add, and

temporarily store genealogical information until it may be organized and stored in more

permanent formats.

There are three forms of solid state storage

Solid state drives

Solid state cards

Solid state modules

Solid state drives

A solid state drive is a type of mass storage device similar to a hard disk drive (HDD). It

supports reading and writing data and maintains stored data in a permanent state even without

power. Internal SSDs are connected to a computer like a hard drive, using

standard IDE or SATA connections.

Instead of storing data on magnetic platters, SSDs store data using flash memory. Unlike hard

drives, SSDs do not have any moving parts (which is why they are called solid state drives).

110

https://techterms.com/definition/solidstate

https://techterms.com/definition/flashmemory

https://techterms.com/definition/sata

https://techterms.com/definition/ide

https://techterms.com/definition/harddrive

https://techterms.com/definition/storagedevice


The most commonly used solid state drive is USB flash memory drive (disk)

A USB flash drive is a flash memory storage device that plugs in a USB port on a computer.

USB flash drives are convenient for mobile users because they are small and lightweight enough

to be transported in a pocket.

Current USB flash drives have data storage capacities ranging from 256 MB to 64 GB. USB

flash drives have become the mobile user's primary portable storage device

Solid state cards

Solid state cards are non-volatile cards without moving or mechanical parts that supports reading

and writing data and maintains stored data in a permanent state even without power.

Examples of solid state cards are;

A punch card

Flash memory card

Smart card

A punched

A punched card also known as IBM card or Hollerith card is a piece of stiff paper that contains

digital information represented by the presence or absence of holes in predefined positions.

It is a flat card which consists of rows of numbers and letters neatly arranged in columns. To

store data, the card is inserted in a computer drive and then the computer punched a series of

holes in the rows of characters to represent the data stored. It has a very low transfer rate. It has

111

https://en.wikipedia.org/wiki/Non-volatile_computer_storage


much access time, and data access is sequential.

Fig: A punched

card

Flash memory cards

Flash memory cards are tiny re-recordable solid-state devices with no moving parts capable of

retaining data without power. They are commonly used in electronic devices such as digital

cameras and mobile phones. They have transfer rates range from about 1 MBps to 20 MBps or

more.

A smart card

A smart card is similar in size to a credit card. It stores data on a thin microprocessor embedded

in the card. A smart card contains a processor and has input, process, output, and storage

capabilities. When the smart card is inserted into a specialized card reader, the

information on the smart card is read and, if necessary, updated.

Solid state modules

Solid state modules are solid state storage that resides in a Dual In-line Memory Module

(DIMM) or similar form factor. Solid state modules devices are physically smaller in size than

solid state cards; they have lower storage capacity normally used in mobile devices.

Examples of solid state modules include;

Microfilm Microfiche

112

https://searchstorage.techtarget.com/definition/DIMM


Photographic film

Microfilms

These are media used to store microscopic images of documents on roll or sheet film. The

images are recorded onto the film using a device called a computer output microfilm recorder.

The stored images are so small they can be read only with a microfilm or microfiche reader.

Microfilm is a 100- to 215-foot roll of film.

Microfiche

Microfiche is a small sheet of film, usually about 4 × 6 inches. The images are recorded onto the

film using a device called a computer output microfilm recorder. The stored images are so small

they can be read only with a microfilm or microfiche reader.

N.B Microfilm and microfiche have the longest life of any storage medium.

Photographic film

Photographic film is a sheet of plastic such as polyester coated with a light sensitive emulsion

that is used to record and store photographs.

Difference between primary storage and secondary storage

Primary storage Secondary storage

Memory is directly connected t and accessed by

CPU

Memory not connected to CPU

Memory is volatile Memory is non volatile

RAM is directly installed onto a motherboard Hard disk drive is connected to the motherboard by a cable

There is direct access by the CPU There is indirect access by the CPU

Data access is faster Data access is slower

113


Used for processing data Used for storing data

They are small in size They are lager is size

Units of Measuring Computer Memory

The smallest unit of measuring Computer Memory is a Binary digit (Bit). Binary digits are the

numbers 1 and 0 which can be represented in a computer by switching voltage on and off. Eight

little bits make one BYTE.

Definitions;

Bit;

A bit is the smallest unit of measurement of computer memory. Each 0 or1 is called a―Bit

Nibble

A nibble is a group of four (4) binary digits

Byte;

A byte is a group of eight binary digits. It is the fundamental (basic) unit for measuring

computer’s memory.

A kilo byte (KB);

A kilo byte is a group of 1000 bytes (or exactly 210 or 1024bytes)

Megabyte (MB);

A mega byte is a group of 1,000,000 bytes (or exactly 220bytes)

Giga byte (GB);

A Giga byte is a group of 1,000,000,000 bytes (or exactly 230bytes)

Terabyte (TB);

A Terabyte is a group of one trillion bytes

(240bytes)

114


Converting from binary to decimal

Multiply each bit of the binary number by its corresponding bit-weighting factor. Sum up all of

the products in step (a) to get the decimal number.

E.g.: Covert 1011 binary to Decimal

Soln: 1011 binary = 1x23 + 0x22 +1x21 +1x20 +

= 8+0+2+1

= 11

Converting from decimal to binary

Divide the decimal number by 2; and record the remainder. If the quotation is zero, the

conversion is complete. Otherwise repeat step (a) using the quotation as the decimal number. The

new remainder is the next most significant bit of the binary number. E.G.: Convert 11 decimal

to binary

2 11 1

2 5 1

2 2 0

2 1 1

0 0 0

=1011

115


PROCESSING DEVICES

Processing devices are devices that work together in gathering, decoding, executing and

outputting of information to the computer user. They are the computer electronic components

and chips houses in the system unit. The most important processing device is the central

processing unit.

Central Processing Unit

Central Processing Unit (CPU) is the most important component of a computer system that is

commonly referred to as the "brains" or the “Heart” of a computer because it monitors all the

computer operations; it is also called the processor or microprocessor.

Central Processing Unit (CPU) therefore means an electronic device that interprets and carries

out the basic instructions that tell the computer how to work. The CPU in other words controls

and coordinates the activities of all the other components of the computer system and performs

all the arithmetic and logical operations to be applied to the data.

Functions of a central processing unit (CPU)

1. It controls devices under its care

2. It helps in all stages of data processing

3. It performs logical computations & comparison of data

4. It determines how fast a computer performs a function

5. It is used as a yardstick to determine the type & the model of the computer

6. It helps the user to work with many programs at the same time.

7. It stores data temporarily for the computer

Types of central processing unit (processors)

Pentium Pro

Pentium II

Pentium III

Intel Core

Intel core 2

Core 2 quad

Celeron M

AMD Dual core

Intel Pentium Dual core

Parts of central processing unit

116


The CPU is made up of three main components/parts;

1) Control unit

2) Arithmetic and Logic Unit (ALU)

3) Registers ( Memory)

Control unit

The control unit is a group of electronic circuitry that has the overall function of directing and

controlling and coordinating most of the operations within the central processing unit.

It extracts instructions from memory and decodes and executes them. In fact it regulates the flow

of information through the processor. In short, it can be said, this component receives, decodes,

stores results and manages execution of data that flows through the CPU. Its communication

with both arithmetic unit and memory is inevitable.

Functions of the control unit;

Interpreting each instruction issued by program and then initiating the appropriate

action to carry out the instruction.

Directing data from storage to memory.

Sending data required for mathematical operations from the memory to the ALU.

Sending the data processed to the printer or a storage device.

Erasing/deleting/rubbing data from memory when instructed to do so.

Storing results in the CPU memory.

Machine cycle

117


A machine cycle is a series of operations performed to execute a single program instruction. For

every instruction, the control unit repeats a set of four basic steps that s. These four basic steps

include;

1. Fetching

2. Decoding

3. Executing

4. Storage

Step 1: Fetching. The control unit obtains /gets/fetches instruction to be executed from memory

(RAM).

Step 2: Decoding which means to interpret and understand the meaning of given information.

The control unit after receiving instructions, the instruction is then interpreted and translated into

commands the computer understand. Relevant data is moved from memory to the register, and

the location of the next instruction is identified.

Step 3: Executing. Carrying out commands by the given control and performing the actual

operation on the data such as arithmetic computation and logical comparison by ALU.

Step 4: Storage. Storing results into registers or memory

Notice: The first two steps are called instruction time (I-time), and the last two steps are called

execution time (E-time)

Arithmetic Logic Unit (ALU)

Arithmetic Logic Unit (ALU) is an electronic circuitry that executes all arithmetic and logical

operations. Its function is to perform arithmetic calculations such as addition, subtraction,

multiplication and division as well as comparisons. The unit also compares numbers, letters, or

special characters. There can be more than one Arithmetic logic unit in a CPU, and these ALUs

can also be used for the purpose of maintaining timers that help to run the computer.

Program registers (Memory Unit)

118


Register is a circuitry that acts as the main store, internal store or intermediate access storage

used to store data within the CPU while the computer is processing functions.

Register is a temporary storage area within the CPU which is responsible for holding data and

instruction to speed up processing.

Register is a part of the processor, not a part of memory or a permanent storage device. They are

additional storage locations that offer the advantage of speed.

Types of registers and their roles

1. Instruction register, which contains the instruction being executed;

2. Address register, which keeps track of where a given instruction or piece of data is

stored in memory.

3. Storage register, which temporarily holds data taken from or about to be sent to

memory.

4. Accumulator, which collects the result of computations;

5. General-purpose register, which is used for several functions, such as arithmetic

operations.

OUTPUT DEVICES

Output is data that has been processed into a useful form called information. Output can be in a

form of text, graphic, audio, and video.

Text consists of characters (letters, numbers, punctuation marks, or any other symbol requiring

one byte of computer storage space) that are used to create words, sentences, and paragraphs.

Graphics are digital representations of non-text information such as drawings, charts,

photographs, and animation (a series of still images in rapid sequence that gives the illusion of

motion).

Audio is music, speech, or any other sound.

Video consists of images played back at speeds to provide the appearance of full motion.

119


Output from a computer can either be is a hardcopy form or a softcopy form.

Hardcopy

A hardcopy is permanent reproducible information from a computer printed on printed materials

such as computer prints out, tale printer pages, fax pages, etc.

Advantages of a hardcopy

It cannot easily be changed without trace.

It can be read off-line without a computer.

It doesn‘t require computer devices in order to read the output hence becoming cheap.

Hardcopies last longer if stored in a safe place compared to a softcopy which must all

the time be changed with the technological developments taking place.

Hardcopies cannot be attacked by viruses as the case with the softcopy.

Disadvantages of a hard copy

It Is Expensive.

It Is Difficult To Store.

Other Users Can Make Copies Of The Hard Copy.

It Is Not Environmentally Friendly

Soft copy

A soft copy is the unprinted digital document file. It can be viewed through appropriate editing

programs like word processor, data base programs, presentation soft ware. It can also be moved

from one computer to another through a file transfer.

Advantages of soft copy

They are not presented physically

They only exist on the computer hard drive

They are used for personal purposes

They can easily be converted into a hard copy

They are less costly

Disadvantaged of soft copy

120


Information can easily be manipulated.

It cannot be read without a computer.

It requires computer devices in order to read the output.

Softcopy changes all the time when the technological development is taking place.

Softcopy can easily be attacked by viruses.

Output devices are devices used to bring out information from the computer and present it in a

suitable form to the user.

Examples of output devices;

Display devices

Printers

Speakers

Headsets

Earphones

Fax machines

Multifunction peripherals

Data projectors

Interactive whiteboard

Terminals

3D-spectacles

Display devices

Display devices also known as Visual Display Units (VDUs) are output devices that visually

convey text, graphics, and video information to the user. Information’s shown on a display

device are known as soft copy.

Examples of display devices include;

Liquid Crystal Display (LCD) monitors

Cathode Ray Tube (CRT) monitors.

Plasma monitors

Data projector

Head mounted display /A head gear

Light emitting diode (LED)

Liquid Crystal display (LCD monitor)

A liquid crystal display (LCD) monitor is a computer monitor or display that uses LCD

technology to show clear images, and is found mostly in laptop computers and flat panel

121


monitors.

They are available in a variety of sizes, with the more common being 17, 19, 20, 22, 24, 27, 45

or 65 inches. Many LCD monitor have wide screen, which are much wider than they are tall.

Advantages of LCD Monitors

They require little power.

They take up less desk space than CRT.

They emit very little radiation.

They are portable than CRTs

Disadvantages of LCD Monitors

They are very expensive than CRT monitors

They can only be viewed from a very narrow angle.

LCD color output is usually slow and poor

Factors that affects the quality of an LCD monitor

i) Resolution

ii) Response time,

iii) Brightness,

iv) Dot pitch,

v) Contrast ratio.

i) Resolution is the number of horizontal and vertical pixels in a display device. A pixel is a

single point in an electronic image.

A higher resolution uses a greater number of pixels and thus provides a smoother, sharper,

and clearer image.

ii) Response time of an LCD monitor or screen is the time in milliseconds (ms) that is takes

to turn a pixel on or off.

iii) Brightness of an LCD monitor or screen is measured in units.

A nit is a unit of visible light intensity equal to one candela (formerly called candlepower)

122


per square meter.

The candela is the standard unit of luminous intensity.

iv) Dot pitch, sometimes called pixel pitch, is the distance in millimeters between pixels on a

display device.

v) Contrast ratio describes the difference in light intensity between the brightest white and

darkest black that can be displayed on an LCD monitor.

A Cathode Ray Tube (CRT) monitors

A CRT (cathode ray tube) monitor is a desktop screen that contains a large sealed glass cathode-

ray tube. Inside the CRT, an electron beam moves back and forth across the back of the screen.

This causes dots on the front of the screen to glow, producing an image on the screen. Each dot

consists of a red, a green, and a blue phosphor, which combine to make up a pixel.

Advantages of CRT monitors

They operate at any resolution, geometry and aspect ratio without the need for

rescaling the image.

CRTs run at the highest pixel resolutions generally available.

Produce a very dark black and the highest contrast levels normally available.

CRTs produce the very best color and gray-scale and are the reference standard for all

professional calibrations.

CRTs are best for rapidly moving or changing images

Can produce fast and rich color output.

Can be viewed from a very wide angle.

They are cheaper than the LCD.

Disadvantages of CRT monitors

They are subjected to geometric distortion and screen regulation problems.

123


They are relatively bright but not as bright as LCDs. Not suitable for very brightly lit

environments.

Some CRTs have a rounded spherical or cylindrical shape screen.

CRTs give off electric, magnetic and electromagnetic fields that pose a health hazard

They are large, heavy, and bulky. They consume a lot of electricity and produce a lot of

heat.

A plasma monitor

This is a display device that uses gas plasma technology, which sandwiches a layer of gas

between two glass plates. When a voltage is applied, the gas releases ultra violet (UV) light. This

UV light causes the pixels on the screen to glow and form an image.

Advantages of plasma monitors

1. They can be mounted on the wall

2. They are less bulky than rear-projection televisions

3. They produces deep blacks allowing for superior contrast ratio

4. They have a wider viewing angle than those of LCD

5. They are less susceptible to reflection glare in bright rooms

6. Plasma monitor offer screen sizes up to 60 inches wide.

7. Have a richer color display than LCD monitors.

Disadvantages of plasma monitors

1. They have heavier screen-door effect compared to LCD or OLED based TVs.

2. Susceptible to screen burn-in and image retention

3. Susceptible to "large area flicker".

4. Generally do not come in smaller sizes than 37 inches.

5. Heavier than LCD due to the requirement of a glass screen to hold the gases

6. Use more electricity, on average, than an LCD TV

124


7. Do not work as well at high altitudes due to pressure differential between the gases inside

the screen and the air pressure at altitude.

8. They are more expensive.

Data projectors

A data projector is an output device that can take images generated by a computer and

reproduce them onto a screen, wall, or other surface so that an audience of people can see the

image clearly. For example, you could use a projector to show a presentation on a large screen

so that everyone in the room can see it.

There are three types of data projectors;

A liquid crystal display (LCD) projector

A digital light processing (DLP) projector

Cathode ray Tube projector

Applications of data projector today

Project a PowerPoint presentation at a business meeting.

Project a computer screen to teach a class in school.

Project a TV or computer with a movie playing to a large screen.

Demonstrate a product or service at a convention center.

Transform a wall, house, or other object to give it a different appearance.

Head mounted display (HMD) / headgear

A headgear is made up of two tiny display and sound systems that channel images and sound

from the source to the eyes and ears, thus presenting a stereo three dimensional sound effect in

the virtual world. The wearer may also put on a body suit that senses the body movement and

relays the data into the virtual reality system which in turn adjusts the position of the user in the

125

https://www.computerhope.com/jargon/p/powerpoi.htm

https://www.computerhope.com/jargon/o/outputde.htm


system.

Light Emitting Diode (LED) displays

Light emitting diode is a flat panel electronic device that emits light when an electrical current is

passed through it. They are typically used outdoors in store signs and billboards.

LEDs are commonly used for indicator lights (such as power on/off lights) on electronic devices.

They also have several other applications, including electronic signs, clock displays, and

flashlights. Some examples include street lights, the red lights on cars, and various types of

decorative lighting. You can typically identify LEDs by a series of small lights that make up a

larger display.

Advantages of display devices (Visual Display Unit)

Their time to display the image is fast.

Their screen displays can include text, graphics and colors.

Display devices are usually quiet.

No paper is wasted for obtaining the output.

Disadvantages of display devices (Visual Display Unit)

Information produced on the screen is only temporary and will be lost when the

power of the device is off.

Un suitable for users with display problems

Needs a separate device (Such as a printer) to produce the hardcopy

126


Printers

A printer is an external hardware output device that takes the electronic data stored on a

computer or other device and generates a hard copy of it on a standard size sheet of paper.

Printers are one of the most popular computer peripherals and are commonly used to print text

and photos.

Printers differ in terms of speed, storage, features, quality, and capabilities are available in a

range of prices.

CATEGORIES OF PRINTERS;

Character printers

Line printers

Dot matrix printers

Page printers

Daisy wheel printers

Braille printer

Impact Printers

These are printers that produce a hard copy output by the print heads physically touching the

print media. Print media include paper, transparencies, cloths, some plastics, etc. Impact

printers form characters and graphics on a piece of paper by striking a mechanism against an

ink ribbon that physically makes contact with the paper.

Examples of impact printers include;

Character printers

Line printers (High speed printers)

Dot matrix printers

Page printers

127

PRINTERS

Inkjet printers

Photo printers

Laser jet printers

Label printers

Plotters

Mobile printers

Thermal printers

IMPACT PRINTERS NON-IMPACT PRINTERS

https://www.computerhope.com/jargon/h/hardcopy.htm


https://www.computerhope.com/jargon/e/external.htm


Daisy wheel printers

Braille printers

Character printers

Character printers are types of printers that print one character at a time instead of one line at a

time. Character printers are rarely used today because of speed issues and because only text is

capable of being printed.

Line printers

A line printer also known as a band printer, chain printer, drum printer, and barrel printer is an

impact printer that prints one line of text at a time or entire line of text at once from one end of a

paper to the other end.

These types of printers are too fast to be measured in words or characters per minute, and in lines

per minute. For example, a line printer may be capable of printing over 3,000 lines of text per

minute

Dot Matrix Printers

Dot matrix printers are types of printers that produces characters and illustrations by striking pins

against an ink ribbon like in a type writer to print closely spaced dots in the appropriate shape.

Dot-matrix printers are relatively expensive and do not produce high-quality output

Page printers

Page printers are printers which processes and print a whole page at a time, as opposed to

printers which print one line or character at a time such as line printers and dot-matrix printers.

A page printer is a printer that prints one full page of text or graphics at a time, ejects that page

and then feeds in the next page to be printed. They are much faster than all other printers.

128

https://en.wikipedia.org/wiki/Dot-matrix_printer

https://en.wikipedia.org/wiki/Line_printer

https://en.wikipedia.org/wiki/Printer_(computing)


Daisywheel printer

Daisy wheel printers are printers consisting of a wheel and attached extension on which molded

metal characters are mounted. When it is printing the wheel rotates until the right character is

facing the paper. They produces quality texts but cannot produce graphics output. Printing

different types of font is impractical since the wheel has to be changed to get a different font

Braille printers

Braille printers are impact printers that create tactile dots on heavy paper, making written

documents accessible to blind individuals. They press dots down onto a piece of paper to let a

person using the Braille system read by using their fingers.

A Braille embosser is a device that connects to a computer to produce printed material in the

Braille writing system. They need special Braille paper which is thicker and more expensive than

normal paper. Once a copy produced, printing further copies is often quicker by means of a

device called a "thermoform", which produces copies on soft plastic.

Character printer Line printer Dot matrix printer

Page printer Daisy wheel printer Braille printer

Braille paper

Advantages of impact printers

They are easy to maintain (can withstand dusty environments, vibrations and high

temperatures)

They are more flexible and inexpensive.

They print various styles and heavy graphics.

They have a longer life span. Can print over 100 million characters in their lifespan.

129


Disadvantages of impact printers

They are noisy during operation.

They tend to overheat up especially during long printouts.

They have a lower print resolution compared to non – impact printers.

Their printing speed is too low.

They require special form of paper.

Non – impact printers;

These are printers that produce characters and graphics on a piece of paper without the

print heads physically touching the printing surface.

Examples of non-impact printers include;

Inkjet printers

Photo printers

Laser jet printers

Label printers

Plotters

Mobile printers

Thermal printers

Inkjet printers

Inkjet printers are types of printers that recreates digital image by propelling droplets of ink onto

paper, plastic, or other substrate.

In the inkjet printing mechanism, the print head has several tiny nozzles, also called jets. As the

paper moves past the print head, the nozzles spray ink onto it, forming the characters and images.

An inkjet printer can produce from 100 to several hundred pages, depending on the nature of the

hard copy, before the ink cartridges must be replaced. There is usually one black ink cartridge

and one so-called color cartridges containing ink in primary pigments.

They are used for printing greeting cards, banners, business cards, and letterhead, envelopes,

labels, greeting cards.

Cartridge

130


A cartridge is physical object in a protective plastic shell that contains a substance (black ink or

powder substances) that is inserted into a printer, allowing it to print. A compatible toner

cartridge is one that is specially designed to work with a particular brand and model of printer.

Photo printers

Photo printers are color printers that produce photo-lab-quality pictures. Some photo printers

print just one or two sizes of images. Others print up to letter size, legal size, or even larger.

Most photo printers are pict Bridge enabled, so that you can print pictures without a computer.

LaserJet printers

LaserJet printers are high-speed and quality nonimpact printer that uses photocopier technology.

When a document is sent to the printer, a laser beam "draws" the document on a selenium-coated

drum using electrical charges. After the drum is charged, it is rolled in toner, a dry black powder

type of ink. The toner adheres to the charged image on the drum. The toner is transferred onto a

piece of paper and fused to the paper with heat and pressure. After the document is printed, the

electrical charge is removed from the drum and the excess toner is collected. Most laser printers

print only in monochrome. A color laser printer is up to 10 times more expensive than a

monochrome laser printer.

Advantages of LaserJet printers

Are generally quiet and fast.

Can produce high quality output on ordinary papers.

Cost per page of toner cartridges is lower for than for other printers.

Disadvantages of LaserJet printers

The initial cost of LaserJet printers can be high.

A label printer

These are small printers that print on an adhesive (sticky) type of materials that can be

placed on a variety of items such as envelopes, packages, DVDs, photographs, file folders,

131

https://refreshcartridges.co.uk/igloo/wp-content/uploads/2012/12/Untitled.jpg


and toys. Most label printers also print bar codes. Label printers are different from ordinary

printers because they need to have special feed mechanisms to handle rolled stock, or tear

sheet (fanfold) stock

Plotters

Plotters are output device that is used to produce high quality graphics in a variety of colors.

Plotters are used to create maps, architectural drawings, graphs and charts.

These are sophisticated printers with a pen like print head that can accurately draw straight,

thin and meandering lines. They are used to produce high-quality architectural drawings

such as blueprints, maps, circuit diagrams, posters, and signs.

These printers are usually very costly, and are used in specialized fields such as engineering, and

graphic art. They use ink-jet printer technology, on a much larger scale, to print professional

quality displays. These printers typically can handle paper with widths up to 98 inches.

Advantages of plotters

Plotters can work on very large sheets of paper while maintaining high resolution.

They can print on a wide variety of flat materials including plywood, aluminum, sheet

steel, cardboard, and plastic.

Plotters allow the same pattern to be drawn thousands of times without any image

degradation.

Disadvantages of plotters

Plotters are quite large when compared to a traditional printer.

Plotters are also much more expensive than a traditional printer.

A mobile printer

This is a small, lightweight, battery-powered printer that allows a mobile user to print from

a notebook computer, Tablet PC, PDA, smart phone or other personal mobile device while

traveling. They fit easily in a briefcase alongside a notebook computer. Mobile printers

mainly use ink-jet, thermal, wax-transfer, or dye-sublimation technology.

There are two main approaches to mobile printing. One involves direct communication between

a mobile device and a printer and communication between a mobile device and a computer

connected to a printer.

132


Thermal printers

Thermal printers are non-impact printers generate images by pushing heated pins against a

coated heat-sensitive paper. The coating turns black in the areas where it is heated, producing an

image. Basic thermal printers are cheap, but the print quality is low and the images tend to fade

over time. Thermal printing technology is, however, ideal for use in small devices e.g. ATM

receipt printers.

Advantages of Thermal printers

They are inexpensive.

They are nearly noiseless

They consume very little power compared to other printers

They don‘t experience inconveniences like paper jams or blocked nozzles.

They can produce clear and crisp images with very high resolutions.

Disadvantages of Thermal printers

Needs a special temperature sensitive paper which may be expensive.

Over heats during printing.

The papers have limited shelf lives. They are easily damaged by sunlight,

humidity and chemical vapors.

The papers have to be specially prepared before they can be used in printing

Their print heads cannot be serviced or repaired even if a single dot heater fails.

The print speed is so slow because the heads have to be allowed time to cool before

the next printing cycle.

The print heads also have a short life span than for the other printers.

Inkjet printer Photo printer LaserJet printer Label printer

133


Plotters Mobile printer Thermal printer Cartridge

DIFFERENCE BETWEEN IMPACT AND NON-IMPACT PRINTERS

Impact Printers Non impact Printers

1. They print characters or images by striking

print hammer or wheel against an inked ribbon.

1. They print characters and images without

striking the papers.

2. Their speed is slower. 2. Their speed is faster.

3. Their printing quality is lower. 3. Their printing quality is higher.

4. They normally uses continuous paper sheet. 4. They normally uses individual paper sheet.

5. They generate lot noise during printing. 5. They generate no noise during printing.

6. They use inked ribbon for printing. 6. They use toner or cartridge for painting.

7. They are less expensive. 7. They more expensive.

8.Print heads are reliable, durable i.e. can last

for a long time

8.Print heads are less durable

9.They print limited colors 9.They are capable of printing strong clear

colors

10.They are not commonly used today 10.They are commonly used today

134


The difference between screen output and print output

Screen output Print output

Displays soft copy output Prints hard copy output

The output is temporarily incase power goes

off

The output is permanent i.e. It can be

maintained for future reference

The output is silent Produces a lot of noise when outputting

especially impact printers

Different styles of print e.g. italics, and color

displays possible.

A styled print is only possible with the

advanced models having the color capabilities.

It is very fast Comparatively slow

Factors to consider when selecting/ buying a printer

1. The initial price and the subsequent coast of maintenance

2. The coast of consumable items like paper quality, cartridges it uses, ribbons etc.

3. Volume of printing expected that helps on the selection of the printer speed range of the

computer.

4. The nature of report and print quality the printer can offer.

5. Range of viability for selected printer like multiple copy facility, print styles, page width

etc.

6. The type of the manufacturer should also be considered.

Speakers

Speakers are output hardware devices that connects to a computer to generate sound. The signal

used to produce the sound that comes from a computer speaker is created by the computer's

sound card.

They receive audio input from the computer's sound card and produce audio output in the form

of sound waves. Most computer speakers are active speakers, meaning they have an internal

135

https://pc.net/glossary/definition/output

https://pc.net/glossary/definition/soundcard

https://pc.net/glossary/definition/input

https://www.computerhope.com/jargon/s/souncard.htm



amplifier which allows you to increase the volume, or amplitude, of the sound. Speakers usually

come in pairs, which allow them to produce stereo sound from two separate audio channels.

Most personal computers have a small internal speaker that usually outputs only low-quality

sound. For this reason, many personal computer users add speaker systems to their computers to

generate a higher-quality sound for playing games, interacting with multimedia presentations,

listening to music, and viewing movies.

Headsets

Headsets are hardware devices that connect to a telephone or computer that allow the user to talk

and listen while keeping their hands free. Headsets are commonly used in technical support and

customer service centers which allow the employee to talk to a customer while typing

information into a computer.

Ear phones /Headphones;

Earphone is an electrical device worn on the ear to receive radio or

telephone communications or to listen to a radio, MP3 player, etc.

They are used on the web to listen to interviews, talk shows, sporting events, news, recorded

music, and live concerts from many radio and television stations.

These are used in a computer laboratory or other crowded environments, where speakers might

not be practical. They are normally connected in a port on the sound card, in a speaker, or on the

front of the system unit. With the headphone or earphone, only the individual wearing the

headset hears the sound from the computer

136



Fax (or facsimile) machine

A fax machine is a device that transmits and receives typed or hand written documents over

telephone lines. A stand alone fax machine scans the original document, converts the image into

digitized data, and transmits the digitized image. A fax machine at the receiving end reads the

incoming data, converts the digitized data into an image, and prints or stores a copy of the

original image.

Fax capability also can be added to a computer using an external fax modem.

Multifunction peripheral (MFP)

A multifunction peripheral (MFP) is a single device that performs a variety of functions

such as printing, copying and scanning that would otherwise be carried out by separate

peripheral devices. This looks like a copy machine but provides the functionality of a

printer, scanner, copy machine, and perhaps a fax machine.

Data projectors

A data projector is an output device that can take images generated by a computer and

reproduce them onto a screen, wall, or other surface so that an audience of people can see the

image clearly. For example, you could use a projector to show a presentation on a large screen

so that everyone in the room can see it.

There are three types of data projectors;

A liquid crystal display (LCD) projector

A digital light processing (DLP) projector

Cathode ray Tube projector

137



Applications of data projector today

Project a PowerPoint presentation at a business meeting.

Project a computer screen to teach a class in school.

Project a TV or computer with a movie playing to a large screen.

Demonstrate a product or service at a convention center.

Transform a wall, house, or other object to give it a different appearance.

Interactive whiteboard (IWB)

Interactive whiteboard also known as smart board is an instructional tool that allows computer

images to be displayed onto a board using a digital projector. The instructor can then manipulate

the elements on the board by using his finger as a mouse, directly on the screen. Items can be

dragged, clicked and copied and the lecturer can handwrite notes, which can be transformed into

text and saved.

Terminal output devices

Are electronic or electromechanical hardware device that are used for entering data into, and

displaying or printing data from, a computer or a computing system.

Spectacles

138

https://www.computerhope.com/jargon/p/powerpoi.htm


These are common in modern computer games especially on fights. The user wears the glasses

like ordinary sun glasses except that here, instead of seeing through the glasses, one will be

treated with high quality three – dimensional pictures. It is similar to being in a cinema hall.

COMMUNICATION DEVICES

Communication devices are devices that connects the communications channel to a sending

device by converting the data, instruction or information from the sending device into signals

that can be carried by a communications channel

Example of communication devices;

Modem

Router

Hub

Switch

Gateway

Cables

Bridge

Repeater

Network interface card

Multiplexer

Modem

A modem is a communication device that converts between analog and digital signals

Router

Router is an intelligent communications device that sends communications traffic to the

appropriate network using the fastest available path

139


Hub/concentrator

A hub is a communication device that connects multiple devices to the network. Its function is to

send and receive signals along the network between the devices connected to it by broadcasting

the data to all the devices/computers. It serves as a central meeting place for cables from

computers, servers and peripherals on the network.

Switch

A switch is a high-speed device that maintains a bridging table, keeping track of which hardware

addresses are located on which network segment. It maps the internet protocol (IP) address with

the Media Access Control (MAC) address of the LAN card.

Gateway

A gateway is a communication device that consist of a combination of hardware and software

that connects networks that use different protocol technologies by performing the required

protocol conversions

140


Cables

Cables are also known as cords, connectors or plugs refers to one or more wires covered in a

plastic covering that allows for the transmission of power or data between devices.

They are insulated wires having a protective casing and used for transmitting electricity or

telecommunication signals.

There are two main types of computer cables;

Data cables are cables that provide communication between devices. Power cables are any

cables that powers the devices

Bridge

A bridge is a communication device that links two local area networks that use the same address

method or protocol. It accepts all packets from each network addressed to devices on the other,

buffers them, and retransmits them to the other network.

Repeaters

141

https://www.computerhope.com/jargon/d/data.htm

https://www.computerhope.com/jargon/p/power.htm

https://www.computerhope.com/jargon/w/wire.htm

http://predire.ug/wp-content/uploads/2017/07/5-Metres-High-Speed-HDMI-to-HDMI-Cable.jpg

https://i.stack.imgur.com/l5Myy.jpg


A repeater is a communication device that accepts a signal from a transmission medium,

amplifies it, and retransmits it over the medium in order to overcome attenuation.

N.B Attenuation is the process by which signals undergo reduction in its strength as it

travels over long distances.

Network interface cards (NIC) or LAN Adapter

A network interface card is an electronic communication device or an expansion card that

enables and other devices a computer to connect to a network.

Multiplexer

Multiplexer is a communications device that combines two or more input signals from various

devices into a single stream of data and then transmits it over a single transmission medium.

TOPIC 3: COMPUTER SOFTWARE:

Computer software is a program that consists of step by step instructions that tell the computer

how to perform a given task. Software consists of computer programs that control the working of

the computer hardware.

142


A program; A computer program is a sequence of instructions, written to perform a specified

task with a computer. Without software, the computer hardware cannot do anything.

Characteristics of computer software

Computer software is intangible

Computer software gives instructions/procedures to computers

Computer software is copy righted

Computer software can be installed

Computer software is executable

computer software is loaded into Memory when running

All software has a source Code written by a programming Language.

What the software consumer wants

Cheap to buy

Easy to learn

Easy to use

Solves the problem

Reliable

Powerful

Fast

Flexible

Available (easy to obtain

What the software producer wants:

Cheap to produce

Well-defined behaviour

Easy to "sell"

Easy to maintain

Reliable

Easy to use

Flexible

Quick to produce

143

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Instruction_(computer_science)


Factors to consider before obtaining a software program

Correctness: does the software do what it is supposed to do (according to the design specs)?

Robustness: how does the software respond to unexpected conditions (wrong input)?

User-friendliness: is the software easy to use by users from the intended audience?

Adaptability: how difficult is it to modify the software to adjust to an ever-changing world?

Reusability: can parts of the software be easily reused to build other software systems?

Interoperability: does the software interface with other software systems?

Efficiency: does the software make good use of its resources (memory, disk, CPU, network)?

Portability: can the software to easily ported (moved) to other operating

Security: does the software protect the information it is responsible for?

Categories of computer software

Computer software is categorized into two groups;

144


System software

Application software

Systems software

These are a set of instructions that control the operation of the computer and its devices. It refers

to the various computer programs that control the way a computer operates. It is a collection of

software found in the CPU, and inside ROM (firmware).

Firmware is a small program recorded by the computer manufacturers at the factory on

electronic chips mounted on the computer’s motherboard or any other devices to control the

devices. Examples of devices that contain firmware include remote control, cell phones,

digital cameras and ROM chips.

Characteristics of system software

It is machine dependent.

It serves as the interface between the users.

They are written by computer programmers or professional system programmers.

Some system software resides in ROM (permanently) hence known as firm ware.

It is usually supplied by the manufacturers of the computer

Types of system software

Operating system

Utility software

Programming languages

Operating system;

Operating system is a set of programs that coordinate the operation of all hardware devices and

application software components of a computer. The operating system relies on device drivers to

communicate with each device in the computer.

A device driver is a program that controls a particular type of device that is attached to a

computer by converting the general input/output instructions of the operating system to messages

that a device type can understand. It is small program that tells the operating system how to

communicate with a device

145


Examples of operating system

Disk Operating System (DOS): It is the main system control program that enables the computer

to operate.

Windows Operating System: These are operating systems that use icon – based graphical user

interface that simplifies working on a computer such as Windows95, Windows98, windows 10,

windows 8.1, windows 7 etc.

Networking Operating Systems (NOS): These are system software’s that organize and

coordinates the activities on a local area network. They are designed to be used on several

computers that exist on a network. They include; Sun Solaris, UNIX, Linux, Novell Netware etc.

Tasks that are perform by networking operating system

Administration of network users

System maintenance tasks such as backup

File management tasks

Prioritizing print jobs on the network

Monitoring security on network resources

Palm operating system: Is an operating system designed for the hand – held computers

(Personal Digital Assistants– PDAs). An example of palm operating system is Pocket PC2002.

Ubuntu is a free and open source operating system and Linux distribution freely available with

both community and professional support. Ubuntu is offered in three official editions; Ubuntu

Desktop for personal computers, Ubuntu Server for servers and the cloud, and Ubuntu

Core for internet devices.

Functions of the Operating System

Controls the hardware resources like accessing disk drives, printers and keyboard

It calls into memory programs and instructions when required

It protect hardware, software and data from improper use e.g. when deleting a file.

It provides error correcting routines for instance when data is lost during transfer.

146

https://en.wikipedia.org/wiki/Cloud_computing

https://en.wikipedia.org/wiki/Server_(computing)

https://en.wikipedia.org/wiki/Personal_computer

https://en.wikipedia.org/wiki/Linux_distribution

https://en.wikipedia.org/wiki/Operating_system

https://en.wikipedia.org/wiki/Free_and_open-source_software


It helps in managing files and memory by allocating items to the area of memory while

they are being processed.

It Schedules and loads other programs in order to provide a continuous sequence of

operation.

It enable application software to interface with the hardware

Provides an interface between the user and the application software and the hardware

It monitors system performance by accessing and reporting information about various

system resources and other devices.

Classification of operating system

Operating systems are categorized based on the followings:

1) The number of tasks an operating system can perform concurrently

2) According to the number of users that can be logged in at a time

3) The human computer interface (HCI) used.

4) According to the processing mode

Classification according to tasks handled

Single operating system

Multitasking operating system

Multithreading operating system

Multiprocessing operating system

Multi programming operating system

Single task operating system is a type of operating system that allows processing of only one

user program at a time. This implies that the user can only run one interactive program at a time.

Multitasking operating system is a type of operating system capable of allowing multiple

software processes to run at the same time on one computer (CPU).

Multithreading operating systems is a type of operating system that allows different parts of a

software program to run concurrently. Multi threading is the ability of a program to manage its

147


use by more than one user at a time and to manage multiple requests by the same user without

having multiple copies of the program running on the computer.

Multi processing operating system is a type of operating system capable of supporting and using

more than one computer processor at a time

Multi programming operating system is a type of operating system cable of executing two or

more programs on a multi user operating system.

Classification according to the number of users

Single user operating system is a type of operating system designed to manage the computer so

that a single user can effectively do one task at a time. The Palm OS for Palm handheld

computers is a good example of a modern single-user, single-task operating system.

Multiuser operating system is a type of operating system that allows multiple users to use the

same computer at the same time.

Classification of OS according to human–computer interface

The user interface is the aggregate of means by which the user interacts with the computer

system. A user interface provides:

Input, allowing the users to manipulate a system

Output, allowing the system to indicate the effects of the users' manipulation

Types of computer user interface

Graphical user interface

Command line interface

Touch user interface

Voice recognition interface

Graphical user interface (GUI) operating systems

A graphical user interface (GUI) is a type of user interface that allows users to interact with

programs by manipulating graphics, along with a keyboard and pointing devices such as a

mouse, to provide an easy-to-use interface to a program.

148


Advantages of a GUI operating System

They make computer operation more intuitive, and thus easier to learn and use.

GUIs generally provide users with immediate, visual feedback about the effect of each

action. For example, when a user deletes an icon representing a file, the icon immediately

disappears, confirming that the file has been deleted.

GUIs allow users to take full advantage of the powerful multitasking capabilities of

modern operating systems by allowing such multiple programs to be displayed

simultaneously.

GUIs have windows that enable a user easily to view, control, and manipulate multiple

things at once.

GUI is easy to use because of the use of graphics because user simply uses the mouse to

choose the appropriate icons/commands.

GUI enables a user to create shortcuts, tasks, or other similar actions to complete a task or

run a program

Disadvantages of GUI operating System

GUI requires a lot of system resources (e.g. memory space) because of each of the

elements that need to be loaded such as icons, fonts, etc.

When it is not properly built, it can be very difficult to work with.

It requires the installation of additional software, e.g., the "runtime environment" in the

case of java.

It is very slow to download into memory.

The user choices are restricted to those on the menus

Command-line user interface (CLI) operating system

The command line is a user interface (CLI) that is navigated by typing commands at a command

prompt; for example, the root MS-DOS command line prompt generally is C:\>.CLI can only be

navigated by using a keyboard and entering commands; it does not use a mouse.

149

This method of instructing a computer to perform a given task is referred to as ‘entering’ a

command: the system waits for the user to conclude the submitting of the text command by

pressing the Enter key on the keyboard.

Advantages of command-line user interface

It does not require a lot of memory resources to run because it is light.

Users have much more control of their file system and operating system in a command

line interface. For example, users can easily copy a specific file from one location to

another with a one-line command.

It is precise because the user states exactly what he or she wants to do, and the more

sophisticated CLIs keep a record of the commands that have been issued.

Disadvantages of command-line user interface

Difficult to use by new users because of the memorization and familiarity of commands

needed to operate a command line interface new user find it much more difficult to

successfully navigate and operate a command line interface.

CLIs cannot show images.

It is fast and precise because command line users only need to use their keyboards to

navigate a command line interface and often only need to execute a few lines to perform

a task.

Difference between command Line Interface and Graphic User interface

CLI GUI

The user has to know the commands or look

them up

The commands are much more intuitive

The commands usually have to be entered in

full

Command shortcuts are possible such as

<Ctrl> C to copy

150


The user has to learn the commands and more

training is needed

Less learning and training by the user is

required

The interface can be daunting, more difficult

to use and the user is more likely to make

mistakes

The GUI is more user-friendly

There are no graphics Graphics are used to represent tasks, files etc.

There are no menus Menus are used for making choices and

selections

The user has complete control The user choices are restricted to those on the

menus

Commands have to be entered accurately with

the correct spellings and syntax (rules)

Spelling and typing errors are avoided

No pointing device is used A pointing device is used to select items and

make choices

Touch user interface

These are graphical user interface that uses a touch screen display as a combined input and

output device

Voice user interfaces

These are types of user interfaces that accept input and provide output by generating a voice

prompt by pressing keys or buttons or responding verbally to the interface.

Classification of operating System according to processing mode

151


Processing mode refers to the method of processing that the operating system supports.

Examples include;

Time operating system

Batch process operating system

Real-time operating system

Distributed operating system

Embedded operating system

Time sharing operating system is method where multiple users with different programs interact

at the same time on a multi-access system. For example in a learning institution where students

and professors are connected to the central CPU at one time from different terminals

Batch process operating system is where programs and data are collected together in a batch

queue before processing starts. Batch processing can be used for fairly automatic tasks; for

example, weekly or monthly payroll processing, processing utility bills (water, electricity, etc.)

and credit card bills.

Real-time processing operating systems are the type of operating system designed to respond

to an event within a predetermined time. As soon as the data is input, it is processed and output

immediately. These types of operating systems are found in environments where computers are

responsible for controlling systems continuously; for example, robotics, manufacturing,

interactive games, airlines and theatre booking systems.

Distributed operating systems are types of operating systems that manage a group of

distributed computers. Distributed computations are carried out on computer networks that work

in cooperation.

Embedded operating systems are types of operating systems designed to operate on small

machines like PDAs. They are able to operate with a limited number of resources.

Factors to consider when choosing an operating system

The Human–computer interface

The Applications intended for the computer.

152


The availability of operating system on the market.

The basic design of the computer.

The Hardware provisions of the computer.

The available of operating systems for all sizes of computers.

The operating system should be user friendly.

The cost of the operating system

Reliability and security provided by the operating system.

The number of processors and hardware devices it can support.

The number of users it can support

The availability of basic utilities and accessory programs within the operating system

Installation and un-installation of operating system

There are many reasons why you might need to install or reinstall an operating system:

When you need to upgrade to a more advanced operating system.

When the existing operating system files have been corrupted and it therefore no longer

functions.

When you need to set up a brand new machine which was supplied without an operating

system.

When you need to perform a recovery on your computer after it has suffered a fatal error

(accidental error)

In case of an irreparable Registry or System file corruption in the existing Windows

installation.

Note: Before doing a clean install of an operating system, you will need to back up your data

files.

Utility programs

A utility program is a type of system software that allows a user to perform maintenance-type

tasks, usually related to managing a computer, its programs and its devices.

Utility programs included with most operating systems provide the following functions:

153


Managing and searching for files,

Viewing images,

Securing a computer from unauthorized access,

Uninstalling programs,

Scanning disks,

Defragmenting disks,

Diagnosing problems,

Backing up files and disks,

Setting up screen savers.etc

Examples of utility program include;

A file manager;

It is a utility that performs functions related to file and disk management such as;

Formatting and copying disks

Organizing files in folders

Displaying a list of files on a storage medium

Checking the amount of used or free space on a storage medium

Organizing, copying, renaming, deleting, moving, and sorting files; and

Creating shortcuts.

A shortcut is an icon on the desktop that provides a user with immediate access to a program or

file.

Formatting a disk is the process of preparing a disk for reading and writing.

A search utility

A search utility is a program that attempts to locate a file on your computer based on the criteria

you specify. The criteria could be a word or words contained in a file, date the file was created or

modified, size of the file, location of the file, file name, and other similar properties.

A personal firewall

154


A personal firewall is a utility that detects and protects a personal computer from unauthorized

intrusions. Personal firewalls constantly monitor all transmissions to and from a computer. When

connected to the Internet, your computer is vulnerable to attacks from hackers (people who try to

access a computer or network illegally).

An uninstaller

An uninstaller is a utility that removes a program, as well as any associated entries in the system

files.

A disk scanner

A disk scanner is a utility that searches for and removes unnecessary files from the hard disk. It

is used to detect and correct both physical and logical problems on a hard disk or floppy disk and

searches for and removes the unwanted files. A physical problem is one with the media e.g. any

scratch on the surface of the disk.

A disk defragmenter

A disk defragmenter is a utility that reorganizes the files and unused space on a computer's hard

disk so that operating system can be able to access data quickly and running of programs faster.

Disk defragmentation enables data to be accessed more quickly and programs to be run faster.

NB; Defragmentation is the process of reorganizing the disk so that the files are stored in

contiguous sectors meanwhile Fragmentation on the other hand is the process of in which files

are divided into pieces scattered around the disk. Fragmentation occurs naturally when you use

a disk frequently, creating, deleting, and modifying files. At some point, the operating system

needs to store parts of a file in noncontiguous clusters.

A diagnostic utility

A diagnostic utility is a type of utility that compiles technical information about your computer's

hardware and certain system software programs and then prepares a report outlining any

155


identified problems.

A backup utility

A backup utility is a utility that allow users to copy, or back up, selected files or an entire hard

disk to another storage medium. During the backup process, the backup utility monitors progress

and alerts you if it needs additional media, such as another CD or tape.

Disk checker

Disk checker is a utility that scan the contents of a hard disk to find files or areas that are faulty.

Disk cleaner

Disk cleaner is a utility used to find files that are unnecessary to computer and can decide to

delete.

Disk compression

Disk compression is a type of utility used transparently to compress / uncompress the contents of

a disk, and increasing the capacity of the disk.

Network utility

Network utility is a utility used to analyze the computer's network connectivity, configure

network settings, check data transfer or log events.

A screen saver

A screen saver is a utility that causes a display device's screen to show a moving image or blank

screen if no keyboard or mouse activity occurs for a specified time. When you press a key on the

keyboard or move the mouse, the screensaver disappears and the screen returns to the previous

state.

Importance of a screen saver

156


To prevent ghosting problem that is images that are permanently etched on a monitor’s

screen

It prevents unwanted lookers from accessing information or data from your computer.

For advertising business on the screen

For entertainment- in which digital photos can be put on your screen as moving pictures

Debugger

Debugger is a utility program used during the testing of a program by tracing and removing of

errors from newly installed programs.

N.B. Debugging is a process of removing of errors from installed programs in the computer

system.

Antivirus utility

Antivirus utility is a utility used to detect remove, and prevent viruses from a computer‘s

memory or storage devices.

A file compression utility

A file compression utility is a type of utility used to reduce or shrink the size of a file. A

compressed file takes up less storage space on a hard disk than the original file. Compressing

files frees up room on the storage media and improves system performance.

Disk partition

Disk partition is a utility used to divide an individual drive into multiple logical drives, each with

its own file system which can be mounted by the operating system and treated as an individual

drive.

Programming languages

157


A computer program is a step by step set of instructions that a computer has to work through in

a logical sequence in order to carry out a particular task. The computer executes these

instructions when told to do so by the user.

Computer programming

Computer Programming is defined as the process of creating computer software using a

programming Language. Computer programs are written by Human individuals (Programmers).

Programming Languages

Programming languages are the vocabulary and set of grammatical rules for instructing a

computer to perform specific tasks. There are many different types of programming languages

each having a unique set of keywords (words that it understands) and a special syntax

(grammar) for organizing program instructions.

It is a set of instructions used to direct the operation of a computer.

Characteristics of programming languages

Every programming language has instructions for input and output.

They have instructions for calculations.

They have instructions for transfer of control instructions for data storage and retrieval

They gave instructions for data movements

Classification of programming languages

1. Machine code languages (First generation language)

2. Assembly languages (second generation language)

3. High level languages (Third generation language)

4. Fourth generation languages

5. Fifth generation languages

Categories of programming languages

There are two categories of programming languages;

158


Low Level Languages

High Level Languages

Low Level Languages

Low level languages are languages written without sequence of text including words, numbers,

and punctuations.

There are two types of low level languages;

Machine Code (First generation Language or1GL)

Assembly language (Second generation Language or 2GL)

Machine Code languages (First generation Language or1GL)

These are languages written in binary form represented in the binary system by 1 and 0

respectively. Machine language codes are very difficult to read and write by human beings hence

susceptible to errors.

Characteristics of machine code languages (First Generation Language)

They are fast to execute because it is already in the language that the computer can

understand.

Difficult to interpret hence requires the aid of a reference manual to interpret the

meaning of each code).

Very easy to make mistakes in the sequence of 1s and 0s; replacing a 1 for a 0 can result

in the wrong command/instruction being executed

It is difficult to identify mistakes made

Time-consuming and tedious to write

They are machine dependent

Programming becomes more difficult as the complexity of the program increases

Advantages of machine code languages

They are efficient

They allow control of each operation

They don’t require either a compiler or interpreter

159


Disadvantages of machine code languages

They are very difficult to learn and very unfamiliar to humans.

They are not user-friendly

Their programs cannot be use in a different machine because of different codes.

It is very tiresome to program in machine code language and many errors are likely to

occur.

It is difficult to identify mistakes made

Time-consuming and tedious to write

Assembly language (Second generation Language or2GL)

These are low level languages that consist of Mnemonics symbols (English like words) used to

represent the binary digits of zeros and ones of machine code language. An assembly language

program has to be translated into machine language by an assembler for a computer to

understand.

Characteristics of Assembly languages (Second Generation Language (2GL)

Similar to machine language, assembly languages are machine dependent.

Assembly languages are faster and more efficient in the use of hardware than high-level

programming languages.

Assembly languages have to be translated into machine language by language translators

known as assemblers for the processor to understand.

They are easier to be written than machine language

The code is not very easy to understand, hence the introduction of high level

programming languages.

Advantages of assembly languages

Programs are written more easily compare to machine language.

They had closer control over the computer hardware and executes very efficiently.

They are useful for writing operating systems and game programs which require fast and

efficient CPU.

160


Disadvantages of assembly language

They are designed for specific machines and specific processors.

Programming in these languages is tiresome because programs cannot be moved from

one computer architecture to another without re – writing the code.

Assembly codes needs translation to be executed by the computer.

Programmers are trained in learning and writing programs.

High Level Languages (Third generation Languages or3GLs)

High level languages are languages which consist of statements that resemble human language or

mathematical notations such as valid words, symbols and sentences

Characteristics of high-level languages

They are machine independent hence portable

They are user friendly and easy to learn

High-level language programs are easy to debug

They are more flexible hence they enhance the creativity of the programmer, increasing

productivity

They are executed much slower than low-level programming languages

They have to be translated into machine code before execution; this is done by compilers

and Assemblers.

One instruction translates into several machine code instructions

Advantages of high level languages

They are easy to learn because they use English like vocabularies

They are much easier to learn, understand, write, correct and revise compared to machine

language

They are machine independent and user friendly.

Programs are easy to modify correct errors and maintain

Disadvantages of high level languages

A source program needs a compiler/translator to converts it into machine code.

161


They take a lot of time because they consume large amount of memory.

They are less efficient in the use of CPU and other facilities.

Qualities if a good programming language

Suitability of the problem Clarity and simplicity Efficiency Availability Consistency

Categories of high level languages

i) Commercial languages

ii) Scientific languages

iii) Special purpose languages

iv) Multipurpose languages

v) Command languages for operating system

Commercial languages

This language was developed purposely for commercial use. Example of commercial language is

COBOL

It is an acronym for Common Ordinary Business Oriented Language. It was a high level

language widely used in business. COBOL has the ability to handle input and output of large

volumes of alphanumeric data.

Advantages of COBOL

It is fair and easy to understand.

It can be used on different types of computers.

It enables programmers to easily re – arrange records within a file.

It enables programmers to easily produce reports.

Disadvantages of COBOL

Coding is lengthy and tiresome to make.

162


It takes longer to learn

Scientific languages

These languages were developed purposely for engineering applications and for scientific use.

Examples include; FORTRAN (Formula Translation), and ALGOL (Algorithmic Language)

FORTRAN (Formula Translation)

It was developed in 1956 by IBM to provide an easier way of writing scientific and engineering

applications because of its simplicity, conciseness, standardization, efficiency and numerical

precision.

Advantages of FORTRAN

It is widely accepted and understood.

It is easy to write a simple FORTRAN program.

It has mathematical functions that are good for problems solving.

Disadvantages of FORTRAN

It is difficult to use in other applications other than scientific and engineering

applications.

It is not easy to accomplished input and output operations.

It is difficult to read reports and screen display.

ALGOL (Algorithmic Language). It is suitable for scientific and engineering computations.

Special purpose languages

These are languages intended to be tailor made for a particular type of problem, e.g. machine

control, wages, simulations, control experiments. Examples are; Ada and SQL (structure Query

language).

Multipurpose languages

These are languages which are intended to deal with a number of different types of application

areas especially in the areas of business and science, e.g. BASIC, Pascal, C, C++, and JAVA

163


BASIC (Beginners All Purpose Symbolic Instruction Code)

It was developed in 1964 to teach programming languages to beginners who did not have any

knowledge in programming. It is a simple language which is easy to learn and to use it.

Advantages of BASIC

It is easy to learn and use.

It is so popular

Several books exist that are used as self – teaching manuals.

Disadvantages of BASIC

It is not a standard language

There are many different versions of BASIC with so little compatibility between them.

PASCAL

It was named in remembrance of the inventor of the mechanical adding calculator, Pascal Blaise.

It was developed purposely to teach the concepts of structured programming.

Advantages of Pascal

It reinforces the principles of structured programming.

It is not limited to business or scientific applications.

C

It is a high level language. It is the most portable general purpose language. Derivatives of C are;

C+.

C++ the language is based on C and it is very popular for object oriented programming (OOP)

JAVA is an Object Oriented Programming (OOP) language that resembles a simplified form of

C++. Object Oriented Programming (OOP) uses objects which combine data and behavior. OOP

enables rapid program development. Examples include; Visual Basic.

Fourth generation Languages (4GLs / Application generators / program generators)

164


These are languages designed to make the process of creating a computer – based application

easier by doing the programming themselves. The user defines certain tasks and then the

application generators will create the program code that will perform the tasks that have been

defined. Examples of 4GLs

Structured Query Language

Fifth Generation Languages /5GLs (Artificial Intelligence Languages)

These are languages used in intelligent knowledge based systems (IKBs) such as robots.

They―think and reason like human beings because of the programs installed on them. They are

extremely used in artificial intelligence projects like space exploration.

Web development languages

These include HTML and JAVA. HTML (Hypertext Markup Language) is one of the

programming languages used to create web pages for the internet and intranets.

Factors to consider when choosing a good programming language

Suitability of the problem. Clarity and simplicity. Efficiency Availability Consistency

Language processors (translators)

These are programs used to translate high level programming languages to low level languages

that processors can understand.

Compilers

These translate a program written in a high level language into machine code language. The

entire program is translated into machine code at once.

Assemblers

These translate a low level language (assembly language) into machine code.

165


Interpreters

These translate source program, line by line while the program is running. This is done each time

a program is executed. As a result, a program running under an interpreter runs very slowly

compared to a compiled program.

Linkers

These are programs used to combine compiled programs and determine where the program will

be located in the memory.

APPLICATION SOFTWARE

Application software’s are programs that perform specific tasks for users. They are programs

designed to enable a computer to do a particular job.

Categories of application software

General-purpose software

This is software that is not written for any specific business or organization but which can be

used or adapted to suit a wide selection of users’ specific needs. For example, a teacher can use a

spreadsheet package to prepare a student end of term grades report, and a word processor to

write letters to parents, but the same packages could be used in business to perform different

tasks such as accounting or memo writing.

Specialized software

Specialized software is a program written for a specific task rather than for a broad application

area. These programs provide facilities specifically for the purpose for which they were

designed. For example, a payroll program will usually only be able to deal with all aspects of a

company’s payroll only, it cannot be used for other purposes such as word processing, or

drawing. Other examples of specialized software are expert systems, accounting programs and

theatre or airline booking programs.

Open source software (OSS)

166


Open source software is copyrighted software for which the software plus the source code are

freely distributed.

The OSS free software license/copyright permits users to use, change, and improve the software,

and to redistribute it in modified or unmodified forms. It is very often developed in a public,

collaborative manner.

Source codes (code) are the program instructions written in a computer programming language

to specify the actions to be performed by a computer.

A software license (copyright) is a legal instrument governing the usage or redistribution of

software to protect the interests of the program designer for example, software license may grant

an end-user permission to use one or more copies of software in ways where such a use does not

constitute copyright infringement of the software owner’s exclusive rights under copyright law.

In addition to granting rights and imposing restrictions on the use of software, a software license

contains provisions which allocate liability and responsibility between the parties entering into

the license agreement.

Freeware

Freeware is copyrighted software that is offered at no cost but whose source code is not

provided. Software that is not freeware is referred to as commercial software or pay ware or

commercial software.

Proprietary software (closed source software)

Proprietary software is copyrighted software obtained at a cost where the software publisher

grants a license to use one or more copies of the software, but the ownership of those copies

remains with the software publisher such that all rights regarding the software are reserved by

the software publisher.

Shareware

Shareware is copyrighted software that is distributed free on a trial basis (as a trial version) with

the understanding that the user may need or want to pay for it later.

167


Shareware developers offer the trial version of their program with a built-in expiration date, say

15, 30 or 60 days, as an enticement to buy the complete version of the program. Once the trial

period has passed, the program may stop running until a license is purchased.

Public domain software

Public domain software is the software which is not copyrighted because it has been formally

released to the public domain such that there is no copyright restriction on it.

Copy righted software

This is free software whose distribution terms ensure that all copies of all/modified versions of

the copyrighted software to carry the same distribution terms like the original version.

Software Piracy

Software Piracy is the unauthorized/illegal duplication and use of computer software/programs.

Integrated software

Integrated software is a single application package which combines the most commonly used

functions and commands or interface of many productivity software programs such as word

processor, spreadsheet, database, and communication and graphics presentation packages. For

example, most word processors such as Microsoft office have the capability of mailing, creating

web pages, drawing, charting, and others in addition to word processing.

Software suites

A software suite, also known as application suite or productivity suite, is a software package that

has several applications that work well together because they have related functions, features and

user interfaces, and are able to interact with each other.

Business applications often come in suites, e.g. Microsoft Office, OpenOffice.org, and iWork,

which bundle together a word processor application, a spreadsheet application, presentation

graphics, database and e-mail applications, etc.

Advantages of integrated software and software suites

168


It is easy to transfer data from one component of the application to another.

Integrated software takes up less disk space than individual packages.

The user can move much faster from one application to the next.

It is usually easier to learn how to use the applications in a software suite because the

user interface for choosing commands is similar for all applications.

A software suite tends to be more powerful and versatile than individual applications.

A software suite is less likely to crash and contains fewer errors (bugs), since it has been

widely tried and tested.

The producers of software suites often offer after-sales services (e.g. online help

facilities); users can also get support from user groups and magazines.

Software suites are usually cheaper to buy than purchasing the packages individually.

Disadvantages of integrated software and software suites

Not all the features of a single application are included.

Some integrated packages do not contain all the applications that may be required to

complete a task.

Classifications of application software

Application software’s are classified into two;

Special purpose/Custom (Tailor –made software)

General purpose/Off-the shelf software (standard software)

Special purpose/custom (tailor-made) software

Custom-made software is a program uniquely designed based on the user’s request to perform

particular user’s needs. It is designed to perform a specific group of tasks as requested by the

user that may differ from those done by other already available software.

The individual user hires programmers to design such a program which does not target the

general market and therefore is not available for sale to the general public.

Examples of custom made software

Locally made school management information systems (SMIS)

169


Inventory management systems

Payroll management systems

Library management systems

Advantages of Custom-made software

A custom-made application directly addresses the user’s needs because it is written to the

user’s requirements and fits in with his/her work.

The solutions it offers given the greatest depth, breadth and flexibility possible in meeting

the needs of an organization, since the software product is tailored to the organization’s

specifications.

The software developer delivers and installs the software and trains the end users in the

use of the new software.

The software also performs tasks that the general purpose software cannot perform.

This kind of software can be quickly changed when the needs of the organization change,

since the source code belongs to the company.

Disadvantages of custom made software

High costs of developing the software, on-site installation, support and training.

It takes time to acquire because of the need to get information necessary and to write the

code of the new software.

There is high possibility of undetected errors/bugs in the software.

Off-the-shelf software (OTS) or standard software

These are commercial software packages that are already-made and available for sale, lease, or

license to users and copyrighted, designed to meet the needs of a wide variety of users.

Most software developing companies such as Microsoft Corporation design package and make

available their software package for purchase on the software market for users to make a choice

to buy the software if they think it meets their needs.

Examples of off-shelf software packages

MS office suite

170


Computer game packages

Education software packages

Advantages of off-the-shelf software

Off-the-shelf software’s are relatively cheap. The cost of development can be spread over

a large number of users.

Off-the-shelf software offers a wide range of capabilities, perform several functions.

They are easily available from most computer vendors

This software is thoroughly tested so there are no serious problems or bugs.

Off-shelf has a lot of user support that is; books, user guides, online help and discussion

forums on the Internet.

Off-shelf is easy to learn and use (user friendly)

Off-shelf can be customized to the user’s needs.

The off the shelf programs are easy to install.

Disadvantages of off-the-shelf software:

Off-the-shelf software is highly complex because it includes large sections that a user

may never use.

Off-the-shelf software does not address needs of specific users.

Off-the-shelf software may take a long time to learn properly. This is because this

software tends to be large and complicated.

Using off-shelf is time consuming to learn and adopt because it requires the user to adapt

to the system itself to do the work.

It is very difficult to gain any competitive advantage from its use over business rivals

because they use the same software.

Examples of application software

Word processing software

Spreadsheet software

Database software

Presentation software

Desktop publishing software

Accounting software

Paint and image editing software

171


Web page authoring software

Video and audio editing software

Educational software

Entertainment software

Communication software etc

Uses of application software

There are many different applications programs:

Word-processor: allows you to create, edit, store and print a range of different text documents;

from letters and faxes to books and essays.

Spreadsheet: enables you to use formulas to perform a large number of calculations on data

stored in cells arranged in rows and columns. You can investigate a mathematical problem,

create a budget plan to forecast how much you can save in a year or model the results of a

science experiment and draw a chart of your results.

Database: uses forms to store data in tables made up of records and fields. The data can be

searched using queries in order to find out useful information. It can be used to create anything

from an address book to a complex application that produces end of year reports.

Graphics program: can be used to create posters, perform image processing in order to improve

or alter photographs or create original artwork.

DTP software: Desk Top Publishing software allows you to manipulate text and graphics in

frames on a page in order to create magazines, brochures and other complex documents.

Presentation Software: allows you to create a slideshow to illustrate a talk, or a presentation for

other people to investigate as a kiosk application.

Communication software: could include a web browser or email client software as well as

other programs that allow you to communicate with

Difference between an app and an application

172


An app is a piece of software designed for a single purpose or a single function meanwhile an

application is a piece of software that performs a variety of related functions. Typically, if an app

breaks, life goes on, while applications are considered critical to normal business function and

are therefore considered to be of higher value.

APPLICATION PROGRAMS

These are programs that are designed to perform specific tasks for the user. These are programs

that do the real work for the user. Examples include:-

Word processing

Spread sheets

Presentation

Databases

Graphic design

Desktop publishing

TOPIC 4: WORD PROCESSING

Word processing is the process of creating text based documents such as reports, letters,

brochures, memos, mailing labels and newsletters using word processor.

Word processor is software used to create, edit, format, save and print text based documents.

Examples of word processing software include;

Microsoft word

Corel WordPerfect

Lotus WordPro

WordPad

WordStar

Abi word.

Mac write

Ami pro.

Magic wand. e.t.c

Functions of word processing software

Allow text to be edited easily e.g. insert, delete and move text anywhere in the current

document

It can be used in mailing documents

It is use for mail merging letters.

It can be used in graphics creating and handling e.g. frames, shapes

173


It has inbuilt mathematical formulae especially in tables which can be used in

manipulating data easily.

It is used in creation of tables which are used to present data in a more organized way.

It can be used in sharing of documents.

It can be used by researches to compare data using graphs and charts.

It has a word count feature which can be used in counting if words easily.

It can be used in creating web pages for organizations.

They are used by researchers and managers to create foot notes and cross references.

They are used in creation of letters, document, memos etc

Helps in saving on a storage device

Word processors are used in formatting and designing of simple office publications.

Features of a word processor;

Editing is the process of making changes to the existing content of a document

Common editing features include; Copying, Cutting, Pasting, Inserting, Deleting, Undo, Redo,

Selecting, Find etc

Undo is the feature that allows actions that have been performed to be reversed such that if some

text was accidentally deleted, then the action can be undone.

Redo It is the feature that allows actions that have been undone to be reversed.

Insert is an editing feature that allows adding text or graphics to a document

Delete is a feature that allows the user to erase text or graphics from a document.

Cut is a feature used for removing the original text from its original position onto the clip board

Copy is a feature that allows the user duplicate a section of the text and stores it on the clip board

Paste is an editing feature that allows the user to insert a whole text or a section of text

somewhere else.

174


Find is a feature that allows the user to locate all occurrences of a particular character, word or

phrase.

Replace is a feature that allows a user to substitute existing characters, words or phrases with

new ones

Formatting is the process of making changes to the appearance of a document.

Levels of formatting

Character formatting which involves changing the font, font size, or font style of the text. It

involves applying the boldface, italics and underline text.

Paragraphs formatting; Involves changing the alignment of text, line spacing, indenting text,

tab settings and boarders

Section formatting allows the user to specify page numbers, headers and footers for different

sections or chapters of a document.

Document formatting allows the user to specify the overall page layout for printing. It involves

choosing the paper size (letter, legal, A4, A3), page orientation (portrait or landscape), changing

page margins (top, down, left or right) and the distances between the main body of text and the

edges of the paper.

Saving is the process of transferring data / information from memory to a storage medium such

as a floppy disk or a hard disk.

Print is the feature that allows the user to send a file to a printer to generate output on medium

such as paper.

Word wrap is a Microsoft Word feature which allows a user to type continually without

pressing the enter key at the end of each line.

Spelling checker allows a user to check the spelling of a whole document at one time or check

and correct the spelling or individual words as they are typed (Autocorrect).

175


Thesaurus is a Microsoft word feature that suggest alternative words with the same meaning

(synonyms) for use in the document

Mail Merge is a feature that allows the user to create similar letters, mailing labels, and

envelopes to be sent to several people.

A table is an Ms Word feature which allows a user to organize information into rows and

columns.

Macros allows a user to record or save frequently used keystrokes and instructions which can be

executed later by running the corresponding macros

Clip art gallery allows a user to insert drawings, diagrams and photographs into a document.

Drop cap is feature used to enlarged the beginning letter of a sentence or paragraph

Footnote is a feature used to comment or add additional text found at the bottom of a page that

helps to refer to a document

Endnote is a feature used to comment or add additional text found at the end of the document

that helps to explain word in a document.

N.B. Footnotes are used for detailed comments while endnotes are used for citation of sources.

Header is the area in the top margin of each page where text can be entered.

Footer is the area in the bottom margin of each page where text can be entered.

Line spacing refers to the vertical distance between lines of text. It is a feature allows a user to

select a vertical or horizontal spacing between the characters depending on his need.

Changing Case is a feature that allows a user to type text in different cases. These cases are:

Lowercase: All characters appear in small letters.

Uppercase: All characters appear in capital letters.

Title case: All the first letters of each word in a sentence appear in capital letters.

176


Toggle case: All characters changes from upper case to lowercases and vice versa.

Proof reading: is the process of reviewing a document to ensure the accuracy of its content. Proof reading tools include spelling and grammar checker and thesaurus, research, translate, word count etc

WYSIWYG (What You See Is What You Get) allow the user to print a document exactly as it

appears on the computer screen.

Advantages of word processing software over the ordinary typewriter

Easy and fast to make changes to the document

Have many features to create documents that look professional and visual appealing.

Documents can be previewed before being printed.

Documents can be saved for future reference and editing.

It is convenient in making letters and mailing labels.

It is possible to move blocks of text to different positions in the same document.

One can insert and delete lines of text.

The layout of the document can be altered before printing.

All typing mistakes can be corrected.

The document can be printed many times.

Text can be added to a document without having to type it again.

It can be used to mail documents unlike the ordinary typewriter.

It can create graphics such as shapes, frames etc.

It can be used to create WebPages.

One can easily count the words in the document using the word count feature.

It allows automatic insertion of footnotes and endnotes.

Disadvantages of word processing software

Data can sometimes be lost due to data corruption.

Some symbols aren’t easily accessible, which makes typing in different languages

that use a different alphabet is difficult.

177


Requires a computer to edit or view documents which may sometimes not be there.

Require skills to use

Require electric power to function

Factors to consider when choosing a correct word processor:

1. The operating system you are using and check whether it can support which word

processors

2. If its user friendly

3. Consider the user’s need

4. Consider the cost of purchase

5. Whether it has most common features available with most word processors

6. Whether it comes with a warranty

7. Whether it has inbuilt automatic updates

8. Whether it comes with a documentation that has help and support.

TOPIC 5: ELECTRONIC SPREADSHEETS

A spreadsheet is an electronic worksheet that is used to organize data in rows and columns and

perform calculations on the data. It is an electronic worksheet that is used to organize,

manipulate and graph data.

There are two types of spreadsheets;

1. The manual spreadsheets

2. The electronic spreadsheets

A manual spreadsheet is the type of the spreadsheet commonly used type of book keepers as a

ledger book with many sheets of papers divided into rows and columns on which data is entered

manually using a pencil or a pen

An electronic spreadsheet is the type of the spreadsheet that uses the computer program that

enable the computer use to enter values in rows and columns to manipulate them mathematically

by the use of a formula.

178


Uses of spreadsheets

It can be used by business men to record sales

It can be used by business men to produce invoices

It can be used to compile statements (e.g. Bank statements)

They are used for project planning and forecasting.

They can be use for creating personal lists such as shopping lists etc.

They are used for statistical analysis for instance in calculating average, mode, median

etc

They are use for budget planning such as weekly, motherly, annual budgets.

They are use for processing examinations results.

They are use in schools for creating class registers and mark sheet.

They are use in accounting by generating cashbook, ledger books, balance book etc.

Advantages of using spreadsheets

Handle a variety of applications

Easy organizing and processing of information

Automatic calculations

Enables easy formatting & editing of work

Speedy, flexible and efficient

Can be stored and retrieved at a later time

Reduces inventory (storage)costs

Easy sharing over the network

Neat work with various illustration like charts

Disadvantages of using Spreadsheets

It require a lot of resources like computers which are expensive

It is costly in terms of training personnel and resources needed

It is limited to power availability that is it can‘t work without power.

The whole work is lost in case of Virus attacks

Data can easily be change with ease by hackers.

179


Advantages of using electronic spreadsheets over manual worksheets

It is easy to make changes and corrections to data on the worksheet.

The rest of the worksheet is recalculated whenever data on a worksheet changes.

It is fast with the help of built-in functions and macros.

Calculation is always accurate, provided that data and formulae entered are correct.

It is easy to create different kinds of charts or to change chart types.

Information on charts is updated automatically whenever related data on the worksheet

changes

Spreadsheets are much larger than manual worksheets

They can perform mathematical, statistical and financial calculations quickly and

accurately.

Cells in electronic spreadsheets can use information from other cells

Electronic spreadsheets can be stored and retrieved for repeated use.

Examples of spreadsheet program

include;

Microsoft excel

Corel Quattro Pro

Lotus1-2-3

Super Calc

VisiCalc

Multiplan

Microsoft excel (ms excel)

This is an electronic spreadsheet that can be used for practically manipulating of data and

figures.

Parts of Ms Excel document

A cell is the intersection of a column and a row.

A cell address is a unique address which defines the location of a cell in a worksheet (e.g. A1,

A2, Q7, etc)

Range is a rectangular selection of a worksheet containing two or more cells

180


Work sheet is the biggest range consisting of all the cells in one sheet.

Work book is a collection of various worksheets

Range address is a range reference which has a format of top-left cell address and bottom-right

cell address (e.g. D12:F19)

Labels are text that identify the data and help to organize the worksheet. All label entries are left

aligned by default.

Column letter is a column that runs vertically on a work sheet and each one is identify by a

letter in the column header.

Row number is a row that runs horizontally on a work sheet and each one is identify by a

number in the row header.

Values are numbers to be used for calculations.

Cell reference is the location of a cell on a worksheet.

Types of cell references

Relative cell reference is a cell reference in which the cell address (e.g. B1 + C1) will be self

adjusted when the formula is moved or copied to another cell (e.g. B2 + C2)

Absolute cell reference is a cell reference in which the cell address (e.g. $B$2) is always fixed.

Mixed cell reference is a cell reference that uses absolute column and a relative row reference.

Example $A2 and A$2

Formulae and operators

A formula is a set of instructions for performing a calculation and displaying the resulting value

in the cell. A formula always begin with an equal (=) or a plus (+).

Types of formulae

Numeric (Arithmetic)

Text

181

Logical

Numeric (Arithmetic) formulae is a formula used to perform calculations on values and uses +,

-, *, ^ and % numeric operators for calculation.

Examples=25+5, =A15*B1/B5

A text formula is formulae used to manipulate text. The text is normally enclosed in (quotation

marks) and to combine strings of text, use & (ampersand).E.g =if (B1>80,”Good”)

Logical formulae is statements that evaluate a condition. They result into 1 if true and 0 if false.

They use =, <,>,>=, <= and <>, AND, OR, and NOT to calculate various conditions. Example

Entry Results=5>4 - Results in true or1=5<A1 - Result in 1 or true if A1 has a value less than5=AND(A1=1,A2=2) - Result in 1 or true (if A1 contains 1andA2contains2

=OR(A1=1,A2=2) - Result in 1 or true (if A1 contains 1orA2 contains2)

=NOT(A1=0) - Result in 1 or true (if A1 contains any value but not

zero)

Basic mathematical operators used in spreadsheets

Symbol Description Example() Parentheses =B2*(C4+D5)* Multiplication =B2*C4/ Division =B2/C4+ Addition =(B2+C4)- Subtraction =(B2-C4)% Percentage =C5*60%^ Exponential =C4^2

Rules governing formulas

1. Always begin the formula with an equal sign or plus sign.

2. Type names of the functions correctly

3. Use the number of brackets on either side

182


4. Do not leave unnecessary spaces between functions and brackets

5. Separate multiple arguments with commas

6. Enter the correct number of arguments in their correct order

Functions;

A function is a predefined formula that helps to perform common mathematical functions. Each

function has a specific order, called a syntax which must be strictly followed for the function to

work correctly.

Syntax order

All functions begin with the =sign. After the = sign, define the function name (e.g. SUM). One

or more arguments, numbers, and text or cell references enclosed in parentheses: if these are

more than one argument, separate each by a comma.

Types of functions used in spreadsheet

Statistical functions

Logical functions

Mathematical functions

Lookup functions

Examples of statistical functions

Function Example Description

Sqrt =SQRT(A4) Calculates the square root of a number

Count =COUNT(B1:B2) Counts the number of cells that contain value within a

range

Max =MAX(C2:C3) It returns the largest values in a set of values

Min =MIN(G1:G3) It returns the smallest values in a set of values

Mode =MODE(B2:C4) It returns the most frequently occurring value in a set of

values

Median =MEDIAN(B3:G8) it returns the middle value in a given range

Rank =RANK(A2,A2:A6,0) It returns the rank of a number in a list by comparing its

183


size relative to the others

Average =AVERAGE(C2:C5) It returns mathematical mean of a set of values that contain

numbers

Logical function

If =IF(LOGICAL_TEST_,VALUE_IF_TRUE,V

ALUE_IF_FALSE)

It returns a specified value if a

condition is evaluated is found to be

True and another value to be False

Mathematical functions

Sum =SUM( A1:A2) Returns all the values in range of cells

Products =PRODUCTS(A3:B3) It adds values in a range of cells and

returns the result in the specified cell

Sumif =SUMIF(A1:A10) It adds values in the cells specified by

a given criteria or condition

Countif =COUNTIF(A1:A10) It counts the number of cell within a

specified range that meet the given

criteria

Lookup functions

Hlookup =HLOOKUP( It looks up data that has been

formatted by columns instead of rows

Vlookup It look up data that has been formatted

by rows instead of columns

N.B. In IF function, there are three items between the round brackets to be notice

IF (logical test, value_if_true, value_if_false)

1. Logical test; This is the first argument that you want to test for.

2. Value_if _true; This is what you want to do if the answer to the argument is Yes.

3. Value_if_false; This is what you want to do if the answer to the argument is No.

184


Errors in excel and their possible causes and solutions

#DIV/0! Formula Error

Excel displays #DIV/0 error when a formula tries to divide a number by Zero or an empty cell.

For example = (A1/A2), where A1 contains 4 and A2 contains a null value (0). As shown below.

How to fix #DIV/0 error?

Simple, do not divide the value by Zero.

Change the Value of Cell A2 to a value that is not equal to 0.

Prevent the error from being displayed by using a Logical function IF

#N/A Formula Error

The N/A error is shown when some data is missing, or inappropriate arguments are passed to the

lookup functions (vlookup, hlookup etc.) of if the list is not sorted and you are trying to lookup

using sort option. You can also generate a #N/A error by writing =NA () in a cell.

How to fix #N/A error?

Make sure you wrap the lookup functions with some error handling mechanism. For example if

you are not sure the value you are looking is available, you can write something like =if (is error

(vlookup(…)),”not found”, vlookup(…)). This will print “not found” whenever the vlookup

returns any error (including #N/A)

#NAME? Formula Error

185


This occurs when Excel does not recognize the text in a formula. The most common reason why

you see this error is because you misspelled a formula or named range. There are few other

reasons why this can happen. For example =SU(A1:A3) as shown below.

How to fix #NAME? Error?

Simply correct SU to SUM

Make sure you have defined all the named ranges you are using in the formula.

#NULL! Formula Error

This error occur when you use incorrect range operators. For example the formula =SUM

(D30:D32 C31:C33) returns a #NULL! error because there is no separator between range 1 and

range2.

How to fix the #NULL! Error?

Make sure you have mentioned the ranges properly.

#REF! Formula Error

Excel displays #REF! Error when a formula refers to a cell that is not valid.

186


How to fix the #REF! Error?

First press CTRL+Z and undo the actions you have performed. And then rethink if there is a

better way to write the formula or perform the action (deleting cells).

#NUM! Formula Error

This is number error that you see when your formula returns a value bigger than what excel can

represent. You will also get this error if you are using iterative functions like IRR and the

function cannot find any result. For example the formula =4389^7E+37 returns a #NUM! Error

How to fix #NUM! error?

Simple, make your numbers smaller or provide right starting values to your iterative formulas.

###### Error

You see a cell full of # symbols when the contents cannot fit in the cell. For example a long

number like 15000000 entered in a small cell will show ####s. Also, you see the ###### when

you format negative numbers as dates.

How to fix the ###### error?

Simple, adjust the column width. And if the error is due to negative dates, make them positive.

#VALUE! Formula Error

187


Value error is shown when you use text parameters to a function that accepts numbers. For

example the formula = (A1+A2+A3) returns #VALUE! Error

How to fix the #VALUE! Error?

Make sure your formula parameters have correct data types. If you are using functions that work

on numbers (like sum, sum product etc.) then the parameters should be numbers.

TOPIC 6: ELECTRONIC PRESENTATION

Presentation is a collection of data and information to be delivered to a specific audience.

Electronic presentation is software used to create presentations which can communicate ideas

and other information to a group or audience. The presentation can be viewed as a slide show on

a large monitor or a projection screen. It involves presenter and the participants with visual

information which complements the talk. Examples of presentation software;

Microsoft PowerPoint

Corel presentations

Lotus Freelance

graphics

Harvard Graphics

Micro media director etc

Functions of a presentation

It allows text to inserted and formatted.

It is used to insert and manipulate graphics, images or animations with objects

It has a slide show system to display the designed slide content.

Qualities of a good power point presentation

188


Principles of a good presentation

Avoid excessive visuals and slides to detract you from your message.

Be the primary source of presentation but not power point slides.

Use flowcharts and photographs to illustrate more abstract points.

Think carefully about the sequence or the flow of your slides.

Factors to consider when designing a good presentation

Identify the goal of the presentation

Use slide design effectively

Include the title page with your name, contact, date and session topic for the presentation.

Include only the main points

Present information consistently

Include only one main concept per slide.

Include graphics, charts, and videos to keep your audience alert

Avoid fancy fonts

Don not includes too many slides in your presentation.

Avoid excessive use of animations and transitions

Common terms used in Microsoft Power Point;

Slide is an individual page in a presentation. They are normally viewed using projectors.

Title slide is the first slide in your presentation normally with a heading and sub-heading.

Slide Master/ Master Slide is a single slide that controls all other slides in a given presentation.

Any changes made to it affect the rest of the slides respectively.

Handout is a combination of 2 to 6 slide images on a single page.

Speaker’s notes are notes that help in the actual delivery of a presentation. Power point lets you

enter and print a notes page for each slide

Colour scheme is the overall colour design for all the slides in a presentation

189


Timing is the period of time a slide stays on the screen during a slide show.

Templates are already created files stored in the computer for reference purposes that defines

what your presentation will look like. Power point provides over 100 professionally designed

templates containing proven layouts, color schemes and background textures.

Slide Layout is the given design of a slide showing divisions/areas or sections of a slide where

work can be done. E.g. title only and blank slide layouts

Animations are visual effects applied to individual items in a slide such as graphics, images, titles

etc.

Transition is a way a slide moves off the screen and the next slide appears.

Wizard is a series of automatic steps that guides you through a task. It helps the user to choose a

style and design for the slides.

Transitional looping is a facility which sets up the presentation to run continuously until it is

stopped by the presenter.

Action buttons are built in button shapes that you add to a presentation to use as hyperlink.

Viewing a presentation

Power point provides five different presentation views i.e.

Outline view

Slide sorter view

Slide view

Notes page view

Slide show view

Slide view shows the user how the slide will appear when printed or displayed. It is similar to

page layout in a word processor for windows. All text, graphics and other media elements appear

in slide view.

190


Outline view enables one to outline content much as you would in a word processor to enter,

arrange and edit textual information. It is useful in organizing one‘s thoughts and developing

textual content for a presentation.

Slide sorter view provides a light table for viewing multiple slides. When selected, this view

arranges small thumbnail presentations of your slides, complete with text and graphics, rows and

columns.

Notes page view allows you to insert edit and delete reminder notes for yourself on each slide. It

allows you to use a slide‘s notes page for creating extended notes as an audience handout. It lets

you enter text and graphics in a notes place holder located below the image of the slide.

Slide show view (Also called on-screen presentation) is a view that takes up the full computer

screen, like an actual presentation. It lets you see how your graphics, timings, movies, animated

effects, and transition effects will look during the actual presentation to the audience.

Advantages of presentation software over traditional chalk and talk

1. It provides a wide variety of presentation formats and layouts for the slides.

2. Allows addition of multimedia components such as clipart images, video clips and audio

clips.

3. Allows setting of timing for the slides so that the presentation automatically displays the

next slide after a predetermined period of time.

4. Allows application of special transition effects on each slide.

5. The presentation can be viewed and printed in different formats.

6. Provides no dusty environment

7. Provides security through the use of password

8. Provides different print formats e.g. Handouts, slides.

TOPIC 7: DATABASE

A database is a collection of related information stored for a particular purpose. It is a collection

of interrelated data about a particular subject or for a specific purpose which allows a user to

retrieve, update and manipulate data any time. Examples of database include;

191


Telephone books (directories)

Customer address books

Dictionaries

Television guides etc

School registers

National voters register

National passport register etc

Characteristics of databases

The data is arranged in columns (fields) and rows (columns).

Each column has similar data items.

Each row contains information belonging to a single individual.

Qualities of a good database

Should make the best use of the computer resources

Should be fast

Should interface smoothly with the existing facilities

Should be updatable

Should provide easy access to authorized users

Should preserve data integrity

Should ensure the privacy of data

Database Management System (DBMS) is a collection of programs which allows a user to

create access and maintain a database.

Examples of DBMS

Dbase I, II, III, IV,V

Microsoft access

Oracle

Lotus Approach

SQL (Structured Query Language)

Functions of database management systems

It enable the user to add and delete records

It enable the user to update and modify the existing records

Provides an interface to the user to enter data

Ensure security for data against unauthorized access

192


It enable users to filter out records by meeting certain given criteria

Enables the creation of summary reports

Types of database management systems/ models

Database model refers to the way data can be stored, organized and manipulated.

There are five commonly logical types of database models;

1. Flat file model

2. Hierarchical database model

3. Relational database model

4. Network model

5. Object oriented model

Flat file model is a database made up of only one table. It is easy to set up and use

Hierarchical database is a type of database model in which data is organized into a tree-like

structure. Each record contains one root segment and a variable number of subordinate segments

that define a field within a record.

A relational database is a database which can take information from two or more database

tables and combine them into a new table or report.

NB: A relationship determines the way in which the details in one table are related to the details

in another table. It can be a one to one relationship, one to many or many to many relationships.

The network databases (Online databases) is a type of database model in which data

relationship, items and the database itself is link to each other in form of a network. Combines

records with link which are called pointers; the pointers physically establish the relationships

between records.

Object oriented model is a database model that appears as independent objects which can relate

with each other.

Advantages of using a Database Management System over manual based systems

193


Databases allow control of data redundancy because most of the data is storing in one

place hence less duplication

It provides security and authorization to its users.

Database management system provides possibilities for data backup and recovery.

It provides possibilities of data access via network connection.

Data is entered, stored, modified and accessed by methods that are not affected by

application programs.

Database management system eliminates data duplication that minimizes costs of

maintenance.

Disadvantage of using a Database Management System over manual based systems

There is lack of confidentiality, privacy, and security when information is made available

to user from the remote location

Data quality is compromised when there is increasing number of users accessing data

directly.

It provides threats to data integrity when different people are tempting to update the same

data at the same time.

They are also difficult and time consuming to develop.

Database management systems are expensive to set up and to maintain because of their

complexity and efficiency.

It creates user resistance to change from traditional file orient system to database

management system

Common terms/words used in Microsoft Access

An object is a compilation of table, quarry, form, reports, pages, modules and macro in a

database

A record is a row in a table that contains information about a given person, product or event

A table is a primary element used to collect data that are related to a particular subject organized

into rows (records) and columns (fields) similar to an electronic worksheet.

194


The table structure is the number of fields, field names, and field lengths and data types in the

database table

Table relationships are the associations of data between tables e.g. one-to- one & one-to-many

A file is a combination of related records.

A field is a column in a table that contains a specific piece of information within a record

A field name/Label is a title or a name of a particular column.

Field Length is the maximum number of characters that can be stored for data in a particular

field

Field properties refer to specific characteristics of a particular field.

Validation is the process of checking of input data for errors (e.g. data type) before processing

Data verification is the checking for mistakes when data is copied from one place to another

Data type (field type) is the type of value that you enter into the field. This is a column that

specifies data that will be stored in the field.

Examples of data type (Field type)

Data type (Field type) Description

Text (Short Text) Allows characters (numbers) up to 255 characters that can be calculated

Memo (Long Text) It is used for lengthy descriptive text and number which allow storage of

data up to 64,000 characters

Number Allow storage of numbers only for calculation

Date/time Allows date or time or a combination of both e.g. Date of birth

Currency Is a numeric field automatically assigned a currency sign

Auto number Creates a unique sequential number for each record

Yes/No Allows storage of logical or Boolean values of Yes/No, On/Off,

True/False

Object Linking and

Embedding (OLE object)

Allows a linkage to pictures, photographs & other objects created in

another program such as word document, excel spreadsheet

195


Lookup wizard Allows you to link the field to another table

Hyperlink Allows a link to an internet, internet site or to another location in the

database

Examples of Field properties

Field properties Description

Field size The maximum number of characters needed for any data item (by default 50)

Format The appearance of that particular item in that particular field

Indexed It specifies whether or not duplicates in the field should be allowed in order

to speed up the data search, sort, filter, etc.

Capitation This is a default label in a form or report e.g. DOB for date of birth, L/name

for last name, F/name for first name, M/S for marital status, etc.

Input mask Specifies the pattern or predefined format for data to be entered in that field

e.g. (--/--/--) i.e.dd/mm/yy for date or (-- :--:--) Hh: Min: Sec as for time, etc.

Others are :!( 999} OOO-OOOO for telephone number.

Default value A value that appears in the field automatically even before you enter there

anything i.e. it works as a placeholder e.g. MSMN/ _, U0063/ _, for index

no., 0.0 for numeric fields, etc.

Field validation rule An expression that defines data entry rules i.e. it limits values that can be

entered in that field e.g. "F" or "M" for sex, >=10 for age, "married" or

"Single" for marital status, etc.

Validation text An error message that appears when a validation rule is violated e.g. "Please

only For M for sex."

Required (Yes/No) Specifies whether or not an entry must be entered in that field i.e. if yes you

must type an entry but if No, you may proceed without entering anything.

Decimal places Specifies whether or not number and currency values should have decimals.

If yes, how many.

Allow Zero length A provision for a field to be left blank in case of unavailable data to be

entered later even if the setting for required is yes. To enter a null, leave the

required property as No and leave the field blank e.g. a company without a

196


fax machine/no., etc.

Database objects

A database is made up of several objects, grouped into a single file; among them include;

Database objects Description

Tables Are primary structures in a database that holds raw data

Queries These are tools used to select records from one or more tables in a database.

They do questioning tasks like how many boys from stream A

Forms These are graphical interfaces that are used to display and edit data. Forms

can be developed from a table or a query.

Reports These are tools that enable one to preview and print data in a meaningful

format.

Pages Are tools used for creating/editing world wide web pages

Macros These are simplified programming languages which you can use to add

functionality to a database

Modules These are collection of declaration, statements, and procedures that are stored

together as a unit, modules, like macros, are objects one can use to add

functionality to a database.

Query criteria

A query criterion refers to as expression in Microsoft office access. Criteria are similar to a

formula.

Consider the following criteria use in query;

Criterion Query result

“Kampala” Returns records where the location field is set to Kampala.

Not “Jinja” Returns records where the location field is set to a location other than

Jinja.

Like U” Returns records for all countries whose names start with "U", such as

197


UK, USA, and so on.

Not Like U” Returns records for all countries whose names start with a character

other than "U".

Like “*Lira*” Returns records for all locations that contain the string "Lira".

Not Like “*Lira*” Returns records for all locations that do not contain the string "Lira".

Like “*ina*” Returns records for all locations whose names end in "ina", such as

China and Argentina.

Not Like “*ina*” Returns records for all locations that do not end in "ina", such as China

and Argentina.

Is Null Returns records where there is no value in the field.

Is Not Null Returns records where the value is not missing in the field.

““(a pair of quotes) Returns records where the field is set to a blank (but not null) value. For

example, records of sales made to another department might contain a

blank value in the location field.

Not”” Returns records where the location field has a nonblank value.

““Or Is Null Returns record where there is either no value in the field, or the field is

set to a blank value.

Is Not Null And Not”” Returns records where the location field has a nonblank, non-null value.

>=“Jinja” Returns records of all locations beginning with Jinja and continuing

through the end of the alphabet.

Like“[A-D]*” Returns records for location whose names start with the letters "A"

through "D".

“Uganda” Or “USA” Returns records for Uganda and USA.

In (“Kampala”, “Jinja”) Returns records for all locations specified in the list.

Right ([Location],1)= “X” Returns records for all countries/regions where the last letter is "X".

Len ([Location])>10 Returns records for locations whose name is more than 10 characters

long.

Like "Chi??" Returns records for locations such as China and Chile, whose names are

five characters long and the first three characters are "Chi".

198


Different keys used in database

Primary Key is a key that uniquely identifies each record in the table. The primary key cannot

be the same for two records.

Foreign Key is a copy of the primary key in another table

Composite Key is a primary key that is comprised of two or more fields. It can also be called a

compound or concatenated key.

Wildcards

A wild card is a symbol used to replace or represent one or more characters. Wildcards are

typically either an asterisk (*), which represents one or more characters or question mark (?),

which represents a single character. A wildcard refers to a character that can be substituted for

zero or more characters in a string.

Wild card Description

? Allow a single character or digit at the position marked by?

* Allow any characters, digits, quantity at position marked by*

# Allow access to match any single numerical digit

Example:

J?lly will find Jolly, Jelly,Jilly only

Am* will find only words that begins with “Am” only such as America, amicable

FACTORS TO CONSIDER WHEN DESIGNING A DATABASE

The number of tables needed.

The number of fields and the field names

Unique identifiers of fields with uniquevales

Relationships between the tables if any

Practicability of the database

TOPIC 8: WEB SITE DESIGNING

199

https://techterms.com/definition/string

https://www.computerhope.com/jargon/c/charact.htm

https://www.computerhope.com/jargon/q/question.htm

https://www.computerhope.com/jargon/a/asterisk.htm

https://www.computerhope.com/jargon/s/symbol.htm


Web Design and Publishing is the process of planning, creating, manipulating, saving and

uploading hyperlinked html documents (web pages) to a computer network so that they can be

viewed via web browsers.

A website (or Web site) is a collection of related hyperlinked web pages hosted on a particular

web Server on the World Wide Web.

Each Web site may contain one or more web pages. Each site has a home page which is the first

document/page users see when they enter a site. The site might also contain additional documents

and files which must be hyperlinked. Each site is owned and managed by an individual, company

or organization.

A Web page is a document, typically written in HTML that is accessible via HTTP, a protocol

that transfers information from the Web server to display in the user's Web browser. It is written

in HTML (Hypertext Markup Language). A Webpage contains hyperlinks to other pages or sites.

A hyperlink is a reference or navigation element in a document to another section of the same

document or to another document that may be on a different website.

HTML uses blocks of text enclosed within angled brackets which are referred to as HTML tags.

These tags are codes which describe the structure and formatting of the document (how the web

page is displayed by the browser). For example, there are tags to describe normal text paragraphs,

headings, bullet lists, etc.

Web publishing process

This involves;

Web designing

Web authoring

Web authoring software

Web site hosting

Web site content management.

Web designing

200


Web designing is a process of conceptualizing, planning, and building a collection of electronic

files that determine the layout, colors, text styles, structure, graphics, images, and use of

interactive features that deliver pages to your site visitors.

This is the initial process of web publishing through which a web page is created. It’s about

organizing web content so that it can be easily found and easily read and is attractive to visitors.

Web authoring

Web authoring refers to designing and creation of a Web site, ranging from writing the site's

underlying code to writing the text to managing the site's upkeep. This can be done directly by

writing the html code, or using html tools that operate in the background to create the code while

the author is using a WYSIWYG interface.

Web authoring software

This is a category of software that is used to design web pages, it may not require one to have

any knowledge of HTML coding because it offers Web page design wizards and different web

page design templates for the user to pick from and simply insert content. The software will

generate the required HTML coding for the layout of the Web pages in the background based on

what the user designs. Examples of commonly used authoring software include Dreamweaver,

and Microsoft FrontPage, Note pad

Web site hosting

201

Website hosting is a service that allows individuals and organizations to have their own websites

accommodated on a particular web server from which they are accessed by others on the World

Wide Web. Web hosts are companies that provide space (web hosting) on a server they own for

use by their clients. Some web hosts provide free services while others charge a fee. Free web

hosting is advertisement-supported web hosting, and is often limited when compared to pay

hosting.

A website can also be hosted on a server in a home or on a local area network.

A web page is created using a language called, Hypertext Markup Language, better known as

HTML Code. You can write your own coding within a plain text editor, such as Notepad, or use

an HTML editor, which will write the code for you.

HTML codes, also referred to as HTML tags, are enclosed by the lesser than (<) and greater than

(>) brackets and may be written in capital or lower case letters.

The opening bracket is followed by an element, which is a browser command, and ends with the

closing bracket.

An element may also be followed by attributes, which are words describing the properties of the

element, and further instruct the browser.

Attributes are only contained in the opening HTML tags to the right of the element and are

separated by a space and followed by an equal (=) sign.

The value follows the equal sign and is enclosed in quotes.

Web site content management system

A content management system (CMS) is a system that provides a WYSIWYG interface to

manage the content of a website. This involves adding new content, editing, or modifying

existing content and removal of unwanted or expired content. It allows the content manager or

author, who may not know Hypertext Markup Language (HTML), to manage the creation,

modification or removal of content from a website without needing the expertise of a webmaster.

Examples of CMS include;

202

Example of basic document structure

<HTML>

<HEAD>

<TITLE>your document title goes here</TITLE>

</HEAD>

<BODY>

Your document text goes here

</BODY>

</HTML>

HTML

The very first tag in your document: <HTML> and the very last: </HTML>

HEAD

The second tag in your document. Enclosed within the beginning tag: <HEAD> and the ending

tag: </HEAD> is information about the document that will not display in the body of the

document.

TITLE

The document title, which is enclosed with a begin title tag: <TITLE> and an end title tag:

</TITLE>, all of which is enclosed with the HEAD tags above. The title does not display as part

203

of the document itself, but appears in the browser window title. It is also what is used to name

your document in a bookmark list.

BODY

The complete text of your document is wrapped by a begin body tag: <BODY> and an end body

tag: </BODY>.

Characteristics of a good web site

1. It should be easy to navigate with well arranged, easy to see navigation buttons.

2. Simple and clear layout of sections and content which makes it user friendly ie find content

easily.

3. It must be pleasing to the eye to encourage visitors to the site.

4. It should load quickly to avoid disappointing potential visitors to the site.

5. It should have readable font web safe eye pleasing colours so that visitors can read the

content easily.

6. It should be interactive with contact information, possibility of e-mail, online communication

forum and chats. Message boards etc.

7. Should have active links which enable visitors to access other references.

8. Should be frequently updated and must have a dated of last update.

9. The web pages must have web page titles and brief summaries about the page or site

Project work on web designing

You are required to design five web pages (use any web publishing software) for your school

taking into considerations the properties of a good web site.

Page one is the Home page which must include;

(i) A welcome note and information on the schools location and motto

(ii) The schools email address

(iii) The web links to the other pages

(iv)The navigation bars

204


(v) Company logo

Page two should show bullet list of departments available in the school. Add a link to the

school website for further information.

Page three should contain other facilities offered in the school e.g. swimming, school bus,

and internet services.

Page four should have brief information on your dormitory/house and a simple definitions

list stating the chorus of your house.

A table indicating 5 names of your dorm mates showing their Bio data(age, sex, home

town/district

Insert a relevant form control

Page five should have photo gallery of at least five images

Terminologies used in web designing

These are brief definitions of some of the common terms used in web design and publishing

Bookmark: A bookmark is an anchor tag that defines and links to a specific location in an

HTML document. Bookmarks are useful when you have long pages that are divided into logical

sections, or when you want to jump from one central list of links to multiple locations on a page.

File Transfer Protocol (FTP): The protocol used for copying files to and from remote computer

systems on a network using TCP/IP, such as the Internet.

HTML:(Hypertext Markup Language) A tagging system used to code documents so that they

can be published on the World Wide Web and viewed with a browser

HTTP: (Hypertext Transfer Protocol): The client/server protocol used to access information on

the World Wide Web.

HTTPS: (Hypertext Transfer Protocol Secure) is a combination of HTTP with the SSL/TLS

protocol to provide encrypted communication and secure identification of a network web server.

HTTPS connections are often used for payment transactions on the World Wide Web and for

sensitive transactions in corporate information systems.

205

HYPERLINK: The text or graphic that users click on to go to a file, a location in a file, an

Internet or intranet site, page, location, and so on. Hypertext is text with hyperlinks.

INDEX PAGE: The home page or URL of a website, usually serving as an introduction and

having links to other pages in the website

DOMAIN NAME: The unique name that identifies an Internet site. A domain name is an

identification label that defines a dominion of control on the Internet, based on the Domain

Name System (DNS).

IP ADDRESS: An (Internet Protocol address) is a numerical label that is assigned to any device

participating in a computer network that uses the Internet Protocol for communication between

its nodes.

JPEG / JPG:(Joint Photographic Experts Group) A graphics format used for photos and other

graphics with more than 256 colors.

Page title: The text that is displayed on the page banner of a Web page and in the title bar of a

Web browser.

URL: (Uniform resource locator) is the alphanumeric address that Web visitors use to locate

your Web site on the World Wide Web.

Tags: HTML tags are codes, of keyword elements enclosed by the lesser than (<) and greater

than (>) brackets, which give commands to a browser. e.g. is an HTML tag that tells the

browser to underline text on the webpage.

Web authoring software: A Web site development program that allows Web pages to be

visually created like a desktop publishing program. It generates the required HTML code for the

pages and is able to switch back and forth (in varying degrees) between the page layout and the

HTML.

Web Browser: Is application software which enables a user to display and interact with text,

images, and other information on a Web page (Examples: Opera, Google Chrome, Mozilla

Firefox, Internet Explorer, Netscape, etc.)

206


Web mail provider: A hosting company that primarily provides end users access to internet

services such as e-mail

Web server: A computer that stores and delivers (serves up) websites and their related files for

viewing on the Internet

Webmaster: A person who creates and manages the information and content, organizes and

maintains of a Web site

WYSIWYG: (What You See is What You Get) implies a user interface that allows the user to

view something very similar to the end result while the document is being created.

Homepage

It is the first page (starting page) of a website. It is the table of contents for a website.

A web page

A web page is an electronic document or files of information stored on the web /website. It can

contain text, animations, audio, and video that are connected to other documents.

What to consider when designing a web page

The target or primary audience of the web site.

The impression you wish the site to create to your visitors.

The purpose of the website. Whether personal, commercial or educational. This helps to

determine the design for it.

The browser types or version likely to be used by your primary audience to determine the

nature of materials to use in the website

How to organize the site links and web pages to enable easy navigation through the site by

visitors.

To obtain the relevant content to include in your page.

Obtaining permission to use other people’s copyrighted content or to link to other people’s

sites this protects you from any possible legal problems concerning copyright violation.

Qualities of a good web page

Should have a feedback

207


Should have good navigation buttons

Should load quickly

Should have fewer graphics. Too much graphics can make it to take too long to load,

take up too much space and client computers may not support different colour depths.

Should have a web page title and a summary about the page

Should have dates of the latest updates

Should have links to other pages or to sections within that page

Components of a web page

a) Page titles;

These indicate the name of the website

b) Buttons and icons

These are tools used to navigate through the website

c) Horizontal line separators

These are parallel lines separating different sections of a web page

d) Graphics (Images)

These are pictures used during the designing of the website.

e) Frames

These are used to provide more flexibility to a website

f) Sound buttons

These are buttons used to provide access to sound clips, interviews, music extracts etc, in

case a search engine is to produce sound.

g) Animations

These are components providing movement and actions in a web page. They are used to

make a web page more lively.

h) Hyperlinks

These are colored and underlined text or graphics that one clicks and go to a file, a location

in a file or an HTML page on the internet.

A hyperlink is a word, group of words or image that you can click on to jump to a

new document or a new section within the current document.

208


i) URL (Uniform Resource Locator)

This is an internet or web address describing the location of the server where the

website is located.

j) HTML lines

These are horizontal lines in an HTML page.

k) Comments

Comments can be inserted into the HTML code to make it more readable and

understandable. They are not displayed by the web browsers.

l) Ordered lists

These are lists with items marked with numbers.

1. Coffee

2. Milk

3. Black tea

m) Unordered lists

These are lists with items marked with bullets (typically small back

circles e.g.

Coffee

Milk

Black tea

n) Definition lists

It is a list of items with a description of each item.

o) Forms

These are used to select different kinds of user input. They are used to pass data to a server. They can contain elements like text fields, checkboxes, and radio buttons, submit buttons etc.

p) Text field

It is an input field that a user can enter text into;

e.g.

First name:

Last name:

209


q) Password field

Is an input field that a user can enter a password

into e.g.

Password:

r) Radio buttons

These are buttons in a web page that lets a user to select only one of a limited number

of choices.

They look like;

s) Check box

This lets a user select one or more options of a limited number of

choices. e.g.

I have a bike

I have a car

t) Submit button

This is a button used to send data to a server. e.g.; Username:

u) Drop down arrows

These are used to open dropdown menus

. A website

A web site is a collection of related or hyperlinked web pages.

TOPIC 9: DESKTOP ENVIRONMENT

Desktop environment

A desktop is the first seen by the user when a window is open. It consist of features mainly

shortcuts icons programs such as my computer, recycle bin web browser etc.

210


Shortcuts are icons on the desktop that provides a user with immediate access to a program or

file.

Icons are the smallest graphical or pictorial representation of several commands, an application,

a shortcut etc. it may represent a file, a folder, hardware utility, printer, disk drives etc.

Major icons on the desktop

1) My computer

2) Recycle bin

3) Network places (network)

4) My documents

My computer

This is a component or a system folder in the Microsoft windows file manager windows explorer

which allows the user to explore the content of their computer drives as well as managing their

computer files.

Recycle bin

Recycle bin is also known as Trash. It is a temporary storage for files that have been deleted in

the file manager by the user, but not yet permanently deleted for the file system.

My network places

My network place is an icon on the desktop that displays shortcuts to shared computers, printers,

and other resources on the network. My network place is open by clicking start button, and then

you click my computer then click my network location.

My documents

My document is a name of a special folder on the computer’s drive that the system commonly

uses to store a users documents, music, and pictures, downloads, and other files. It is a user’s

personal folder in which he/she can store documents, graphics, and other personal files.

211


Parts of a desktop

Start button

This is a button located on the left bottom corner of a desktop. It is a button when clicked takes

you to the other programs.

Task bar

A task bar is a located at the bottom of the screen that contains the active tasks that are currently

running on the computer.

Start menu

A start menu contains icons for programs, folders and access to control functions plus other

menus

Notification area

Notification area is an area that contains icons of special programs including the time and date of

the day.

All programs

These are lists of applications installed on the computer which can be opened from the list.

Search programs and files

Changing the appearances of a desktop

Such as desktop background, screen saver, and windows colour.

Procedures of changing desktop appearances

Right click on the empty space on a desktop

From the drop down menu choose personalize option

Adding a program to appear on a desktop

Procedures:

212


Click the start button

Select the desired program and right click

Click show on the desktop

Aligning icons on a desktop

Point the cursor on any empty space of a desktop

Choose the view option which will display a list of other options or rearranging icons on

the desktop

Select the desired option and click

File management

This is a system that an operating system or program uses to organize and keep track of files.

Any document is stored as a file by the computer. Each file has a file name. Each file name has

two parts: file name and file extension. By default the computer allocates a name to a file which

you can change.

A folder

A folder is a specific named location on a storage medium that contains related documents. It is a

virtual container within a graphical user interface in which groups of computer files and other

directories can be kept and organized..

Creating a folder

Right click the empty are on the desktop

Select new from the drop down menu that appears

Select folder

Give the appropriate name to the folder

Then press the enter key on the keyboard

Renaming a folder

Right click the folder

213


Select the option rename

Give the appropriate new name to the folder

Then press the enter key on the keyboard

Moving a folder

Point the cursor to the folder you want to move

Hold down the primary mouse button

Move the folder the desired location or another folder on the screen

Then release the mouse button.

Deleting a folder

Right click on the folder

Choose the delete option

Then click yes

A file

A file is a collection of related data.

Types of files

Regular files are files used to store data in the form of text or binary

Directory files are files that contain information used to access other files.

Special files are files that defines physical devices for the system

Video files for video development.

Web files for web activities such as wed development

System files are files that enable computer to function with the operating system

Image files used to develop photos and graphics.

Audio files for digital audio such as music sound etc.

Backup files for copies of files in a computer which can later be accessed in emergence

cases.

Archived file is a computer file used to store electronic information or documents that you no longer need to use regularly

Creating a file

214


Click on the file menu or the office button in the program you are using

Select the first option new and the click on it.

A dialogue box will appear and then click create

After working with the new file, click the file menu

Select save as option to give the file appropriate name

Then save the file either in my computer or my document or on the desktop by clicking

saves.

Saving a file

Click on the file menu or the office button

Select save as option

Give the file the appropriate name

Choose where to save the file either in my computer or my document, or on the desktop

And then click save

File name and file extension

A computer file is made up of two parts that a file name and a file extension which is separated

by a dot.

A file name is a name used to uniquely identify a computer file stored in a file system. It is

associated with the content.

On the other hand a file extension is a part or suffix at the end of a file name which identifies

the type of file it represents.

It is the end part of a file name that is separated by a dot, containing characters based on the

program used to create the file example tobbyecat. doc, meaning that tobbyecat is the file name

and .doc is the file extension.

Functions of a file extension

1. To identify the file type.

215


2. It identifies what program to associate the file with and how to properly open it using the

correct program.

3. It helps to easily locate files.

Common file extension

NO FILE EXTENSION FILE TYPE EXAMPLE

1 .doc Microsoft word Tobbyecat.doc

2 .xls Spreadsheet Mybook.xls

3 .ppt Presentation DMO.ppt

4 .db Database ICTdeprt.db

5 .pub Publication Cards.pub

6 .rtf Rich text format Invitation .rtf

7 .txt Unformatted text document Tobby.txt

8 .pdf Portable document format A level ICT.pdf

9 .exe Executable file Ecat.exe

10 .bat Batch file Autofile.bat

11 .gif Graphical interchange format. A digital image

file format

Photo.gif

12 .jpeg or mpg Joint photographic experts group. A digital image

file format

Nighty.jpg

13 .png Portable network graphics Tobby.png

14 .mpeg Moving picture expert group

15 .AVI Microsoft windows movie file

216


16 .BPM Graphical Bit Mapped File used in windows paint

17 .HTML Hypertext Markup Language is a Web page files

containing HTML or other information found on

the Internet

18 .SYS Various types of System files – usually drivers to

control devices

19 .xml Extendable markup language

File hierarchy

A file hierarchy defines directories (also called folders), which can contain files and other

directories.

The top-most directory in any file system is called the root directory.

A directory that is below another directory is called a subdirectory.

A directory above a subdirectory is called the parent directory.

File path

A file path or a file directory specifies a unique location of a particular file in a file system.

Example; C:\My Documents\assignments\English\nouns.doc

217

ROOT DIRECTORY

DIRECTORYDIRECTORY

SUB DIRECTORY SUB DIRECTORY


Root directory: C:\

Directory(folder): \My Documents\

Subdirectory(subfolder): \English\

file: \nouns.doc

A file path can be observed in the address bar of a particular window in which the file is being

used. A file path or directory consist of location of a file, user profile, folder, sub folder file, file

name and file type.

Example; D:\visitor\my document\sub ICT\S5 results.doc

D:\ file location

Visitor\ user profile

My document\ folder

Sub ICT\ sub folder

S5 results\ file name

.doc file type

Viewing file extension

Click start button

Click control panel

Click the tools drop down menu

Click folder options

Click view

Uncheck Hide extension for known file types

Click apply, then ok

Managing computer files

When using files on your computer system, there are some aspects one needs to put under

consideration such as storage of files, security for the files, backups, disk space usage and

defragmentation.

Such considerations include;

218


1. Create backups of your files that keeping copies of your files away from computer

to avoid some events such as data loss, disasters like fire out break etc.

2. Install antivirus software to protect your computer against malware.

3. Use file compression schemes to save disk space for files which takes up large

storage space.

4. Use disk fragmentation tool to allow faster computer processing.

5. Protect your files using encryption or password

How to create a file with password

Click on the file menu or the office button in the program you are using

Click on save as option

Click on the tool menu at the bottom of the dialogue box

Click on general options

Type the password of your choice and click ok

Retype the same password

Then click ok

File backup

File backup refers to the activity that involves creating copies of files away from the computer,

which can later be accessed or retrieved.

There are two forms of file backups

1. Local backup (offline backup)

It involves backing up important files to external storage devices such as flash disks, memory

cards, external hard disks, compact disks, Digital versatile disks, magnetic disks, zip drives etc.

2. Internet backup( online backup)

This involves sending your files to another site on the internet computer for safe keeping. You

can even create a backup on your email account.

Importance of backup

To recover from data loss in case of accidental deletion, data theft, data corruption

219


To safely stored data away from the computer

To ensure disaster data recovery plan

TOPIC 10: SYSTEM START-UP AND CONFIGURATION

System Startup is a general term used to describe the process of preparing the computer,

operating system, hardware, or software for operation. This action is more commonly referred to

as the boot or boot up.

The first thing a computer has to do when it is turned on is start up a special program

called an operating system.

As the computer is switched on, it does the Power – On Self Test (POST) before it starts.

The POST consists of RAM check, CMOS check, HDD controller check (Disk Drive

controller check).

In case one of the checks fails, then an appropriate error message is displayed on the

screen or an abnormal number of beeps are sounded. The whole process is called

BOOTING.

Computer booting

Booting is the process of starting or restarting a computer which involves loading an operating

system into memory.

Types of computer booting

There are two types of booting;

1. Cold booting

2. Warm booting

Cold booting

It is the process of starting a computer which has been totally off which involves loading the

operating system into memory.

Steps involved in cold booting

Switch on the main power source (i.e. socket)

Switch on the uninterruptible power supply

Switch on the system unit

220

https://www.computerhope.com/jargon/b/boot.htm


Finally switch on the monitor

Power on self test is conducted by the BIOS, Bootstrap loads the OS into RAM then the

desktop is activated

Warm booting

It is the process of restarting (resetting) a computer that is already turned on. In the windows

environment, it is normally performed by pressing Ctrl+Alt+Del keys on the keyboard.

Reason for warm booting

I. Whenever the computer devices such as keyboards, mouse, etc. stop responding to

commands issued to them.

II. After installing a software or hardware onto your computer.

III. After scanning for viruses.

IV. After uninstalling a software

V. In case one wants to recover from errors

VI. When a computer freezes

Computer booting processes

i. The power supply sends an electrical signal to the motherboard and other devices located

in the system unit.

ii. The CPU resets itself and looks for the ROM that contains the BIOS.

iii. The BIOS executes the Power on Self Test (POST) to ensure that all the computer

hardware is connected properly and operating properly.

iv. The results of the POST are compared with the data in the CMOS chip on the

motherboard.

v. If the POST is completed successfully, the BIOS look for the boot program that loads the

operating system.

vi. Once located, the boot program is loaded into memory and executed, which then loads

the kernel of the operating system into RAM.

221


vii. The operating system loads system configuration information and the remainder of the

operating system is loaded into RAM and the desktop and the icons display on the screen.

Kernel

The kernel is referred to as a memory resident because it remains in memory while the computer

is running.

It is the core of an operating system responsible for;

I. Managing memory,

II. Managing files and devices,

III. Maintaining the computer‘s clock,

IV. Starting applications and

V. Assigning the computer‘s resources such as printers, scanners, etc.

Conditions under which a computer may fail to boot

In case the hard disk is crash

When there is no installed operating system

When the bootable device is unavailable

System configuration

222


This is a process of setting specifications required for a computer or communication device to

properly be usable. That is why it is very important to understand the specifications of a

computer before buying it.

Computer specifications are technical descriptions of the computer's components and

capabilities.

Computer specifications to consider

Components Good Better Best

Processor Intel core i3 Intel core i5 Intel core i7

Memory 4Gb 8GB 16GB

Operating system Windows Xp Windows 7 Windows 10 (64 bits)

Storage 128Gb 256GB 512+GB

Monitor size

Video card Integrated 1-2GB nVidia GeForce 2+GB nVidia GeForce

Warranty 90 days 1 year 3 year +

Resolution 1366x768 1680x1050 1920x1080

How to connect a functioning computer

Before connection, the user must be able to acquire the following parts/peripheral devices;

AC main socket outlets

Uninterruptable power supply

UPS power cable

System unit

System unit power cable

Monitor

Monitor power cable

Mouse

Keyboard

VGA cable

Qn. Explain the procedures for assembling the above devices;

1. Connect a keyboard, mouse & a VGA cable from the monitor to the System unit.

223


2. Then connect the power cable of monitor to the power source & then that of the System

unit.

3. Then boot the computer.

Computer programA computer program is a series of instructions that directs a computer how to perform the tasks necessary to process data into information. Programmers write a program and then store the program in a file that a user can execute (run). When a user runs a program, the computer loads the program from a storage medium into memory.It is a list of instructions that tell a computer what to do because everything done on a computer is done by using a computer program. Examples of computer programs include; a web browser like Mozilla Firefox and apple safari, office suite, video games etc.How to start a computer program

Click on the start button Point the cursor to all programs Open a program folder or file by clicking on it or by double clicking on

the program on the desktop.Locating and opening application program

Application preprograms are the software programs used to solve specific end user needs.

Examples of application programs include word processors, database, presentation software, spreadsheets etc.

To open an application program;

Click start All programs Microsoft office

224


Click at the desired application program.How to shut down a computer

a) Save all you are doing,b) Close all the running program/ active windows.c) Click on the start buttond) Click turn off computere) Click turn off / shut down

Installing system and application software

Software installation

This is the process of making a program ready for execution.

Types of installation

1. Attended installation: 2. Silent installation: 3. Unintended installation4. Headless installation5. Clean installation6. Network installation

Program installation is the process of setting up of a program on a computer to be able to use it.

A utility responsible for installation of any application software is known as a program installer.

A program installer is a specialized program which automates most of the work required for a

program installation, some installers are specifically made to install the files they contain; other

installers are general-purpose and work by reading the contents of the software package to be

installed.

Operating systems are normally supplied with program installers that run when a new installation

is required. Many programs are supplied with a dedicated installer that must be run in order to set

up the program because the installation process requirements vary for each application.

Installation process

225


Open My Computer.

Open the drive that contains the installation files. It may be on a CD or DVD, in that case,

open the D: drive or the letter of the disk drive.

Within the drive that contains the files, locate either a setup or install file. The setup

executable file must have the .exe extension

Alternatively, click Start then Run. In case of windows 7, find run in accessories

In the Run Window, type x:\setup or x:\install where x is the letter of the drive you wish to

start the installation from.

Factors to consider before and when installing a program

Read the manuals for the program or the read me file located in the same directory as the

install commonly contain exact instructions on how to install a program.

Make sure that your computer meets the requirements of the program, game, or utility you

are attempting to install.

After installing or during the installation, a program may need to install other programs, files,

or utilities before it is able to run. If

When installing a program, utility, or game, it is always a good idea first to close or disable

any other programs that are running.

Restart the computer system after installing a new program for it to work well, the computer

may prompt you to reboot the system for the installed program to work.

Hard disk free space

Check on the amount of RAM

Compatibility with the computer basic design

Processor speed

Compatibility with other software

Devices on which software can be installed include;

226


Desktops

Smart Phones

I Pads

Laptops

Tablets

Reasons for installing software

In case of the new application package that must be installed in order to run on a

computer

When the previous installed program is corrupted which require its reinstallation

In case one wants to update the old version of the program by installing an update on it

In case a new device is attach to the computer, there is need to install the device driver

software

In case pdf plug-in which is a set of software components that adds specific capabilities

to a large software application.

Reasons for the failure of software to be installed

The software source CD may not be readable. Verify the disk is readable by reading the files

on the drive.

The computer system may not have the system requirements for the software to run, verify

that your computer meets the minimum requirements of the software program.

The software may not be compatible with the computer system. Make sure the program or

utility you are installing is compatible with the version of operating system you have on your

computer.

Most proprietary software requires that a registration code or serial number is entered before

the software is entered. If you lost your number or key or it does not work, you will need to

227


contact the developer of the program.

Installing device drives

The device driver is a program that controls a particular type of device that is attached to a

computer system. Modern operating systems are designed with many device drivers. The

operating system will automatically detect any new hardware attached to it and install an

appropriate driver and it will be able to work. However, if you buy a new type of device that the

operating system whose driver was not included in the operating system, you'll have to manually

install the new device driver.

Procedures followed when installing a new device

Open Windows Device Manager (Start>control panel> systems> hardware tab> device

manager

You may need to choose "View" and "Show hidden devices" to find it, or it may be

represented by a yellow question mark if there is no driver for it yet and the computer doesn't

recognize it. The categories may help you find it if Windows knows in general what type of

device it is. For example, if you have plugged in a new keyboard and there's a yellow

question mark under the "Keyboards" category, then you may need to reinstall the keyboard

drivers for it to work.

Once you have verified the Device Manager, reboot the computer.

As the computer is rebooting an “install new hardware” wizard should appear if Windows

detects the new hardware.

Select install for a list or specific location this time and click next. Uncheck "search

removable media" and check includes this location in search.

Click next and it will attempt to install the driver. Once done click next and your new driver

is install. A reboot might be required for the device to work properly.

If Windows does not detect any new hardware, open Control Panel and double-click the Add

hardware (or Add a device) icon to run the hardware detection wizard

Once drivers have been installed reboot.

Upgrading drivers for already installed devices

228


Open Windows Device Manager. In the Device Manager locate the device you wish to update

the drivers for.

Right-click the device and click Properties.

In the Properties window click the Driver tab.

Click the Update Driver button.

In the Hardware Update Wizard point Windows to the location of the updated drivers on

your hard disk drive

Once drivers have been installed reboot.

Uninstalling software

Software uninstallation is the deliberate process of removing part or all of a given software from

the computer. A utility used for uninstalling software is an uninstaller.

An uninstaller, also called a de-installer, is utility software which is designed to remove all or

parts of a specific other application software. It is always recommended to use an uninstaller to

uninstall a program.

Reasons for uninstalling software from the computer system;

The software may not be working properly due to corrupt files, or improper installation,

hence the need for a clean reinstallation of the program which requires that the program must

be uninstalled first.

It could be that the software is no longer being used and is unnecessarily taking up valuable

disk space.

The software may be conflicting with other programs installed on the computer.

The software may not be meeting your expectations, that is, it's not functioning as expected.

You may be running out of disk space, therefore you just want to free up some space on your

computer's hard drive.

229


It is always necessary to carry out a proper uninstallation through proper program uninstall

procedure instead of merely deleting the program folder and shortcuts

If you are using windows, get to Programs and Features control panel, then choose uninstall

program to properly uninstall the program;

Procedures of uninstalling software from the computer system


Go to the Control Panel and click

Click on uninstall a program

A list of programs will be displayed

Select the program you want to uninstall and click

Wait until the process of unistallation is done then you click close

Troubleshooting

Troubleshooting is the process of identifying, planning and resolving a problem, error or fault

within a software or computer system. It enables the repair and restoration of a computer or

software when it becomes faulty, unresponsive or acts in an abnormal way.

Troubleshooting is primarily done to keep a system or software in desired condition, specifically

when it encounters or exhibits a problem. It is a systematic approach done within one or more

phases depending on the complexity of a problem.

Typically, the first step involves identifying what the problem is followed by coming up with a

solution to counteract the problem and then implementing that solution. However, there can be

more than one reason for the problem, which will require a more complex solution. An

individual troubleshooting such a problem might test for different solutions to eliminate the

problem or fault.

230


Hardware troubleshooting is the process of reviewing, diagnosing and identifying operational

or technical problems within a hardware device or equipment. It aims to resolve physical and/or

logical problems and issues within a computing hardware. Hardware troubleshooting is done by

hardware or technical support technician.

Hardware troubleshooting processes primarily aim to resolve computer hardware problems using

a systematic approach.

The process starts by first identifying the problem and finding different issues that can cause

such a problem and eventually leading to implementing a solution or alternative. Hardware

troubleshooting is generally done on hardware equipment installed within a computer, server,

laptop or related device.

The various troubleshooting technique used in computer management includes;

a) Use of diagnostic utility

b) Scan disk utility

c) Starting the computer from an external device

Processes within hardware troubleshooting:

Removing, repairing and replacing faulty RAM, hard disk or video/graphic card.

Cleaning dusts from RAM and Video carts slot/ports and from cooling fan.

Tightening cable and jumpers on motherboard and/or components.

Software related hardware problems such as device driver update or installation.

How to troubleshoot a computer


Click the control panel

Under system and security click find and fix problems

Troubleshooting Processes

Identification of the malfunctions within the system

231


Generate possible causes of the malfunctions and eliminate them

Confirm that the solutions restore the process to its working state

Troubleshooting techniques

1) Isolating the problem by finding out if it is software or hardware related, if it is hardware

start with the obvious such as power and loose connections then run diagnostic test.

2) Researching for the ideas related to the problems which may involves asking friend for

advice or referring to reference books or searching from the internet

Common computer problems

a. Power button fails to start the computer.b. Application program running slowlyc. The computer runs slowlyd. Freezes of the computere. Failure of the sound to workf. The mouse or key board stops working

Freezing /hanging up.

This is a situation where the computer becomes completely unresponsive to the commands. When this happens, the user is unable to click anywhere on the screen, open or close any application or access shut down options.

If this happens; Warm boot the computer by pressing Ctrl + Alt + delete keys simultaneously.

Causes of system freezing

1. Overloading the machine with a lot of data and information.2. Multitasking (running too many programs at the same time.3. Virus attack4. When the running program has encountered a problem.5. High traffic in case of a networked system.

232


6. Low RAM7. Aging hardware8. Dust particles in the system unit9. Installing incompatible software on the machine.10. Corrupted operating system11. Entering too many commands at the same time.

TOPIC 11: DATA COMMUNICATION & NETWORKING

Definition of Data communication

Data communication is the process of transferring data, instructions and information from one

computer to another computer.

Elements of data communication

A sending device

Message

A communication device

A communications channel

Protocol

Communications software

A receiving device

A sending device;

A sending device is a device that initiates an instruction to transmit data, information, or

instructions. It can be a computer system, a terminal, a cellular telephone, a GPS receiver, an

Internet- enabled PDA, or another device that originates the message.

Message

This is the data/content/information to be transmitted over a transmission medium. The message

is usually in a discrete form.

A communication device;

233


Is a device that connects the communications channel to a sending device by converting the data,

instruction or information from the sending device into signals that can be carried by a

communications channel; It can be a modem, repeater, switch, router, gateway etc.

A communications channel/medium Also known as communication links or Data links a

communication channel is a medium over which Data travels/is transmitted from one computer

(device) to another. It is a path over which the signals are sent either physically (cables) of

wireless waves. It can be a standard telephone line.

Protocol

This is a set of rules and procedures for exchanging information among computer

device on a network.

A receiving device;

It is the device that accepts the transmitted signals from the sending device. They include

computers, fax machine, digital cameras, cellular telephone, smart phone, PDA, Internet

appliances, and Web-enabled devices.

Communications software;

This software consists of programs that manage the transmission of data, instructions and

information between the sending and receiving computers. It controls and manages the activities

and functions of the communications network.

Importance of computer communication

It facilitates communication over distant areas with help of email, chat etc services

It allows sharing of resources such as printers, routers, storage devices etc

It is reliable

It ensures cost effectiveness in the usage of resources in an organization.

It ensure security of data by putting in place administrative controls over the network

234


It enables distribution of processing facilities

Limitations of computer communication

There is increased risk of data corruption

Data and information transmitted by computer communication technology is vulnerable

to threats

The initial cost of buying communication devices are expensive and costly to maintain

There is great risk of malware infections such as viruses and worms

Computer communication offer worries like hardware and software failure and

troubleshooting

Definition of data communication tools

These are tools that enable the user to emulate and test the networks.

Types of electronic data communication tools

Mobile phones

Computers

Internet

Social network

Mobile phones

Wireless phones are the most dominant form of communication in the world. Text messaging is now

rampant because of the advent of smart phones which allows the mobile phones to have personal

computer functionality of sending large pictures and video files.

Computers

A computer is a multipurpose, automatic and electronic device which allows the user to input data, store

data and information, process data and output information for the future reference.

It is an electronic and automatic machine made up of electronic and electromechanical device which

manipulates and processes data.

Internet

235


Internet is an International/global interconnection of computer networks It is a global network where all

LANs (both big and small) worldwide are interlinked.

Social network

Social medium enable instant interactions among user, who can communicate directly through twitter,

face book, what saps etc.

Services offered by data communication tools

Voicemail

Fax

E –mail

Bulletin Board System (BBS)

Instant messaging (IM)

Chat room

Newsgroups (Discussion groups)

Internet telephony

Videoconferencing

Telecommuting

Groupware

Skype

Voicemail

This functions like an answering machine. It allows a caller to leave a voice message which is

stored in a voice mail box for the caller party. The called party can listen to the message, add

comments to the message and reply or forward the message to another mail box in the voice mail

system.

Fax

A facsimile (fax) machine is a device that transmits and receives documents over telephone lines.

Sent or received documents are called faxes. Fax capability can be added to a computer using a

faxmodem.

E –mail

Email is a transmission of messages via the internet and users can access it from countless

devices including cell phones. Email is virtually instant, much like modern communication

modes.

Bulletin Board System (BBS)

236


It is a computer that maintains centralized collections of electronic messages. They are declining

because of the emerging of internet which can serve the same purpose.


Instant messaging is a real time communications service that notifies a user when one or more

people are online and then allows the user to exchange messages or files with them.

Chat room

Chart room is a location on an internet server that permits users to chat with each other by typing

lines of text on the computer.

Newsgroups (Discussion groups)

It is an online area where users conduct written discussions about a particular subject.

Internet telephony

It is also called a Voice over IP (VoIP). It is a web based telephone that allows a user to talk to

others for just the cost of the internet connection. A microphone, sound card and special internet

telephony software are required for conducting internet telephony.

Videoconferencing

It is a meeting between two or more geographically separated people who use a network or the

internet to transmit audio and video data.

Groupware

It is a software application that helps groups of people to work together and share information

over a network. It enables members of a workgroup to communicate, manage projects, schedule

meetings and make group discussions.

Skype

This service allows users to communicate with peers by voice using a microphone, video by

using a webcam and instant messaging over the internet.

237


Telecommuting

Telecommuting is a work arrangement in which employees work away from the standard

workplace of a company, but communicate with the office using some kind of communications

technology

Advantages of telecommuting

Reduces time and expenses for travelling to and fro work.

Eliminated travelling during bad weather conditions

Allows flexibility in the work schedule

Reduces air pollution by vehicles driven to and fro work

Employers reduce costs due to less office space and furniture required.

Favors the disabled employees

Disadvantages of telecommuting

Reduces human face – to – face interactions among the working staff

If any device of the communications system fails, the work has to stop.

Leisure time at home may be replaced by work.

There is less security over the company’s information.

Global positioning (GPS)

It consists of one or more earth based receivers that accept and analyze signals sent by satellites

in order to determine the receiver‘s geographical location.

Uses of GPS

To locate a person or an object

To find the best route between two points

Monitor the movement of a person or object.

Create a map

To get weather information

Used by cars and ships to provide directions.

238


Difference between electronic and manual data communication tools

Electronic Manual

Require payment for the service Payment is not required

It is very costly to maintain They are very cheap to maintain

Computers are linked for easy

communication.

Drums are used as the most musical tool.

The invention of MMS, SMS, and EMS has

made communication more adaptive, and

motivate to both senders and receives.

A single communication tool such as a drum

has many techniques that enabled sound

communication

Mobile phones as a communication tools

have resulted into fast pacing communication

session.

Several drums, other than timpani drums can

be arranged together to create a drum kit.

Email for education purpose as a

communication tool has help teachers, at the

elementary, secondary level and parents to

communicate on line openly.

Massagers or courier carry messages from

the source to the recipient

Forms (modes) of Data transmission (Communication)

Data transmission/digital transmission/ digital communications is the physical transfer of data

over a point-to-point or point-to-multipoint communication channels. Examples of such channels

are copper wires, optical fibers, wireless communication channels, and computer buses.

Data is transmitted over networks using signals, which are transformed, or encoded, by

computers into the voice, video, graphics, and/or the print we see on our computer screens.

239


A signal is a series of electrical or radio waves which are sent to a radio or television in order to

produce a sound, picture or message. The signals used by computers to transmit data are either

digital or analog

Analog signals are continuous signals that vary in strength. Sound is an example of an analog

signal.

Digital signals are discrete/ discontinuous. Either there is a signal or there isn't a signal. Discrete

signals are represented by on (1) and off (0) pulses.

Modulation and Demodulation of Signal

Modulation refers to the process of converting digital signals into analog form so that data can

be sent over the phone line.

Demodulation is the process of converting the analog signals back into digital form so that they

can be processed by the receiving computer.

Notice; A modem is a hardware that performs modulation and demodulation processes.

240


Examples of data transmission (Communication) forms (modes)

Serial transmission

Serial transmission is the sequential transmission of one bit of signal at a time sent over a single

wire. Low data transfer rates are possible, but can be used to transfer data over longer distances.

Parallel transmission

Parallel transmission is the simultaneous transmission of the signal elements of a character or

other entity of data over two or more separate paths. Multiple electrical wires are used which can

transmit multiple bits simultaneously, which allows for higher data transfer rates than can be

achieved with serial transmission

Asynchronous Data transmission

Transmission where each group of digital or analog signals making up the code for one character

is separated and individually wrapped with a start BIT and a stop BIT and an error check BIT.

Asynchronous transmission is relatively slow because of the extra bits that must be sent with the

data bits for each character.

Synchronous Data transmission

This is the transmission where characters are sent as blocks of signals with header and trailer

bytes at the beginning and end of the block. Synchronous transmission is faster because

characters are sent as blocks; it is therefore used to transmit large volume of data at high speed.

241


DIRECTION OF DATA TRANSMISSION

Simplex transmission

This is a type of transmission where data flow in only one direction from the sending device to

the receiving device.

It is used only when the sending device doesn‘t require a response from the receiving device. It

is applied in security alarms and fire alarms that contain sensors, Radio and Television

broadcast, communication between a mouse and computer.

Half duplex

This type of transmission allows data to flow in either direction from the sending device to the

receiving device and back but not at the same time.

An example of a half-duplex system is a two-party system such as a walkie-talkie. It is used in

radio calls, ATM machines, Fax machines, credit card verification systems, etc,

Full duplex

This type of transmission allows data to flow in both directions at the same time for instance

modern telephone system; the sender can be able to talk while listening to the receiver on the

other side. . E.g. Land-line and Cell telephone networks are full-duplex, since they allow

both callers to speak and be heard at the same time

242


Point to point transmission

A point-to-point connection refers to a communications connection between two nodes or

endpoints.

Multi-Drop transmission

Multi –drop transmission is a transmission bus in which all components are connected to the

electrical circuit. A process of arbitration determines which device sends information at any

point. The other devices listen for the data they are intended to receive. There are both physical

(cable or wired) media, and wireless media.

Definition of data transmission media

243


This is a communication channel or path over which the data signals are sent from the source to

the destination.

Types of data transmission media

There are two types of transmission media, i.e.

Physical (Guided/bounded) transmission media

Wireless (Unguided/Unbounded) transmission media

Data Transmission media

Physical/Guided/Bounded Transmission

media

Wireless/Unguided/Unbounded transmission

media

Twisted pair Cables Microwaves

Unshielded twisted pair cable Satellites

Shielded twisted pair cable Infrared

Coaxial cables Bluetooth technology

Fiber Optic Cables Wi-Fi technology

This is a kind of media which uses wires, cables or other tangible material to send

communications signals. These include twisted pair cables, coaxial, and optical fiber cables.

Twisted pair cable

Twisted pair cables are types of cables in which two conductors of a single circuit are twisted

together for the purposes of improving electromagnetic compatibility and to reduce

electromagnetic radiation, crosstalk between neighboring pairs and rejection of

external electromagnetic interference.

Types of twisted pair cable

244

https://en.wikipedia.org/wiki/Electromagnetic_interference


Shielded twisted pair cable (STP)

Shielded twisted pair cable is a type of copper telephone wiring in which each of the two copper

wires that are twisted together are coated with an insulating coating that functions as a ground for

the wires. The extra covering in shielded twisted pair wiring protects the transmission line

from electromagnetic interference leaking into or out of the cable.

Unshielded twisted pair cable (UTP)

Unshielded Twisted Pair able is a pair of wires without a metal wrapper for shielding noise that

are twisted around each other to minimize interference.

Advantages of twisted pair cables

They are relatively cheap to use because its cost per unit length is low.

They are convenient to use because they are small in size.

They are easy to install because of their flexibility it is easily strung around the room or

wall.

Shielded twisted pair has a foil shielding to help provide a more reliable data

communication.

TP is easy to terminate

It is inexpensive and easy to install.

245

UTP connector (RJ 45)RJ stands for “registered jack”

https://www.webopedia.com/TERM/E/EMI.html


The Disadvantages of twisted pair cables

Used over a short distance, usually less than 100 meters

Twisted pair’s susceptibility (prone) to the electromagnetic interference which leads to

signal loss

They are easily damaged. Especial the UTP

They are low frequency cables. So they are not suitable for transmission of very high

frequency signals like cable TV, TV antenna and radio antenna signals

N.B The basic difference between STP and UTP is that Shielded twisted pair is a twisted pair

cable enclosed in foil or mesh shield that protects against electromagnetic interference

meanwhile Unshielded twisted pair is a cable with wires that are twisted together to reduce noise

and crosstalk.

And the deference between a wire and a cable is that a wire is a single conductor (material most

commonly being copper or aluminum) while cable is two or more insulated wires wrapped in

one jacket.

Coaxial cable;

This is an electrical cable connected over long distances that consists of a single copper wire

surrounded by three insulating layers i.e. an insulating material, a braided metal and a plastic

outer coating. Coaxial cable is insulated more heavily than twisted-pair cable, and thus is not as

susceptible to noise.

Features of coaxial cable

Both conductors share a common center axial, hence the term "co-axial"

It has a high bandwidth

It is highly resistant to signal interference

246


It is used for long distance (300-600 meters)

It is quite bulky and sometimes difficult to install

The most common type of connector used with coaxial cables is the BNC connector

It has higher installation costs

Coaxial is prone to lightning strikes which damage the cables or equipment on which it is

connected.

It is more expensive than twisted pair cables

It is not flexible

Advantages of coaxial cables

It has a high bandwidth capacity

It can be used for long distances between 300-600 meters

It is very effective at carrying many analog signals

It is resistance to signal interference because of its protection shield

Disadvantages of coaxial cables

It is not flexible

It is quite bulky and sometimes difficult to install

It is more expensive that twisted pair cables

It has high installation cost

It is prone to lightening strikes which can damage the cables.

Fiber – optic cable;

A fiber optic cable is a cable that contains hundreds of thin strands/fibers (tiny threads) covered

by insulated glass coated in plastic that use pulses of light to transmit data or signals .The

protective coating is to protect the fibers from heat, cold, electromagnetic interference from other

types of wiring, as well as some protection from ultraviolet rays from the sun. Fiber optics allow

247


for a much faster data transmission than standard copper wires, because they have a much

higher bandwidth.

Advantages of fiber optic cables over wired cables

Carry more signals that wired cables.

They transmit data faster.

They are less susceptible to noise from other devices

Has a better security for signals during transmission

They are small in size and lighter that wired cables.

Disadvantages of fiber optic cables over wired cables

They are more expensive

They are difficult to install and modify

They are delicate.

It is difficult o add additional nodes on the network

It is very complex to configure

Wireless (unguided) transmission media

This is a kind of media that sends communications signals through the air or space using radio,

microwave and infrared signals. Wireless telecommunications technologies transport digital

communications without wires between communications devices. They are used when it is

inconvenient, impractical, or impossible to install cables.

The transmission in wireless technology is facilitated by the use of antenna and receiver/aerials.

Antenna is an electronic conductor use either for radiating electromagnetic energy or for

collecting electromagnetic energy.

Categories of wireless transmission media

Broadcast radio

Bluetooth,

Microwaves

Communications satellite

Wi-Fi

Cellular radio

Infrared (IR)

248

https://www.computerhope.com/jargon/b/bandwidt.htm


Broadcast radio

Radio broadcast is a wireless transmission medium that uses radio waves through the air to send

transmissions over long distances to a large audience who will listen to the transmission through

a radio. Radio broadcast can be expanded by examining radio waves, radio transmitters and

receivers.

A transmitter is needed to send the broadcast radio signal. To receive the broadcast radio signal,

a receiver with an antenna that is located in the range of the signal is needed.

Broadcast radio is slower and more susceptible to noise than physical transmission media but it

provides flexibility and portability.

Advantages of Broadcast Radio

1. Radio covers huge population with a single message.

2. Radio can be enjoyed anywhere be it at home, in office or while driving car.

3. It is less expensive

4. You can advertise your product on radio and the rate of advertisement is usually lower than other

medium of communication.

5. Important information or news can be easily spread on radio.

6. For local market radio is one of the powerful medium of communication.

7. It utilizes modulation schemes such as AM and FM to leverage advantages of both of them.

8. It trains audience to be good listeners.

Disadvantages of broadcast radio

1. It favors only audio medium for communication.

2. It does not favors deaf people

3. It is greatly affected by bad weather

4. You need to adjust frequency properly.

5. Less and limited radio channels are available compared to other communication medium.

249


Bluetooth,

This is a short range wireless technology standard for exchanging data over short distances for

fixed and mobile devices. In order for devices to communicate, they must be able to understand

the blue tooth rules (protocols).

Advantages of Bluetooth Technology

Connection establishment is very quick because users only need to pair the Bluetooth

personal area network connection between two devices.

It has low power consumption.

It can pass through walls.

It has better range than Infrared communication.

There is no issue of interoperability among different Bluetooth vendor products.

It is used for voice and data transfer.

Bluetooth technology is adopted in many products such as head set, in car system,

printer, web cam, GPS system, keyboard and mouse.

Due to availability of Bluetooth headphones, calls can be taken on phone even while

driving and doing some other activity simultaneously.

Bluetooth devices are available at very cheap cost.

It has less interference compare to other wireless technologies

Easy to install

It makes connecting to different devices convenient

Disadvantages of Bluetooth Technology

It can easily be hacked into by intruders

If installed on a cell phone it is prone to receiving cell phone viruses

It only allows short range communication between devices

It can only connect two devices at once

It can lose connection in certain conditions

250


The bandwidth is lower compare to Wi-Fi.

Battery usage is more compare to the condition when Bluetooth is powered OFF

Microwaves

These are high-frequency radio waves that are sent through the atmosphere and space. They

provide a high speed signal transmission by receiving signals amplifies it and transmits it to the

receiving devices or retransmits it to the next microwave transmission tower. Microwave

transmission involves sending signals from one microwave station to another thus called fixed

wireless.

A microwave station is an earth-based reflective dish that contains the antenna, transceivers, and

other equipment necessary for microwave communications.

Microwaves transmit signals in a straight line with no obstructions between microwave antennas.

To avoid possible obstructions, such as buildings or mountains, microwave must be set on the

tops of buildings, towers, or mountains.

Advantages of microwaves

It is difficult to implement lumped components such as resistors, inductors and

capacitors at microwave frequencies.

Microwave communication is limited to line of sight mode only, where loses that we

face in the ground-wave and sky-wave propagations are absent or minimum

Antennas required at microwave frequencies are much smaller in size than those used at

lower frequencies hence low losses of signals

Their comparatively higher frequencies allow broadband width and high data flow

251


Disadvantages of microwaves

Microwave frequencies travel only in straight line path which are limited by horizon

hence difficult to propagate.

Microwave transmission towers are complex in construction, and are highly expensive.

Microwave systems do not pass through solid objects. This can be problematic in cities

with a lot of tall buildings or mountainous regions if you want to send a signal from one

end of the city to the other.

Microwave is subjected to electromagnetic interferences such as Electric motors, electric

power transmission lines that disrupts microwave communication

Microwave is also degraded by heavy wind turbines and moisture in the atmosphere such

as snow, heavy rain and fog in a phenomenon known as rain fade.

Microwave can be exposed to electronic eavesdropping

Applications of microwaves

Broadcasting and telecommunication

To detect the range, speed, and other characteristics of remote objects (Radar technology

is a technology that uses radio waves to find the position of objects which cannot be seen)

Radio astronomy

In navigation especially global navigation microwave systems (GNSS)

Heating and power application e.g. microwave ovens

Communications satellite; Satellites are communication devices stationed in space and use

microwave radio as their telecommunications medium to communicate with the earth based

communication facilities. These earth-based stations often are microwave station.

252


The above flow chart shows the general structure of a satellite communications system. A

Satellite in space links many earth communication facilities. The user is connected to the earth

station through the terrestrial network with various configurations including a telephone switch

or a dedicated link to the earth station. The signal generated by the user is processed and

transmitted from the earth station to the satellite.

Transmission from an earth-based station to a satellite is called uplink meanwhile transmission

from a satellite to an earth-based station is downlink. The uplink frequencies are kept different

from the downlink frequencies in order to avoid interference.

N.B Terrestrial systems are television channels which are broadcast from stations on the ground

and do not use satellites

Applications of satellites

They are used in applications such as;

Air navigation,

Television and radio broadcasts,

Weather forecasting,

Video conferencing,

Paging,

Global positioning systems,

Internet connections etc

Advantages of satellites communication

They receive and broadcast data/signals over larger geographical regions.

They sent a lot of data/ signals simultaneously.

They allow high quality broadband communication across continents

253

http://1.bp.blogspot.com/-hNNwA8K_OzM/UwQr6tzoRDI/AAAAAAAABVs/Vxv6P3ZSdOI/s1600/image002.gif


Satellite communication allows easily establishment of mobile communication

Satellite communication has high bandwidth.

Satellite communications are economical compared with terrestrial communication,

particularly for thin traffic remote areas and where long distances are involved.

They are cheaper over long distances.

Satellite communications allow additional connection on a network; so long as terrestrial

system has the ground-based equipments.

They allow earth Station to be removed from a location and reinstalled somewhere else.

Satellite communications allow users to have control over their own network.

Disadvantages of satellites

It takes long and time consuming to propagate satellite tower

The time delayed in propagation reduces the efficiency of communication satellite in data

transmission.

The initial cost is very expensive and costly

They are subjected to interference by phenomenon

Repair of the satellite is almost impossible, once it has been launched

The infrastructure needed to access satellite communications is also expensive.

Wi-Fi

Wi-Fi is a short form for "wireless fidelity," it is a wireless networking technology that allows

electronic devices to exchange data using radio waves over a computer network including high-

speed wireless Internet and network connections.

Devices that use Wi-Fi such as personal computer, video game console, and smart phones,

tablets, I-pads or digital audio player can connect to a network resource such as the internet via a

warless network access point.

254

https://www.webopedia.com/TERM/I/Internet.html

https://www.webopedia.com/TERM/W/wireless.html


Advantages of Wi-Fi

It is easy to add or move wifi clients or wifi stations to the wifi network created by AP

(Access Point).

Installation is very quick and easy. It does not require technical knowledge of wifi system

and its protocols.

Access to the wifi network can be availed from anywhere within the wifi AP (Access

point) coverage range.

It is easy to integrate wifi functionality in the mobile computing devices

Wi-Fi protected access encryption is considered secure

Different competitive brands of access points and client network inter-operate at a basic

level of service.

Manufacturers are building wireless network adapter into most laptops leading to the

reduction in the price of the chipsets for Wi-Fi

Wi-Fi allows cheaper deployment of local area network.

Disadvantages of Wi-Fi

Wi-Fi networks have limited range, and this range varies with frequency band

Devices that uses Wi-Fi has high power consumption

Wi-Fi connections can be disrupted or the internet speed lowered by having other devices

in the same area.

Wi-Fi is less secured than wired connections for instance Ethernet because an intruder

does not need physical connections.

The practical range of Wi-Fi does not favor mobile devices.

255


Cellular radio

Is a form of broadcast radio that is used widely for mobile communications, specifically wireless

modems and cellular phones. Cellular transmission uses radio waves; therefore, it is possible for

people with special receivers to listen to cell phone conversations.

Advantages of cellular radio systems

They have high user capacity that is the smaller the size of the cell, the number of

concurrent users. So huge cells do not allow for more concurrent users

They transmit less power because of the cells are smaller in size

For huge cells there are a number of interfering signals, while for small cells there

is limited interference only.

As cellular systems are decentralized, they are more robust against the failure of

single components.

Disadvantages of cellular radio systems

Small cells require a complex infrastructure to connect all base station. The

infrastructure required includes switches for call forwarding, location registers etc.

The mobile station has to perform a handover when changing from one cell to

another very frequently.

To avoid interference, frequency spectrum should be distributed properly with a

very less range of frequency spectrum.

Infrared (IR)

Is a wireless transmission media that transmits signals across relatively short distances to

transmit data between personal devices using infrared light waves for instance a computer and a

cell phone.

These devices have an IrDA port

that enables the transfer of data from

256


one device to another using infrared light waves. Infrared transmission can be used to establish a

wireless network with the advantage that devices can be moved, removed, and installed without

expensive wiring and network connections.

Advantages of IrDA (Infrared)

The devices are very cheap.

The devices are compact, light weight and consume low power.

The technology based devices are easy to use.

It is non interfering from RF waves.

They are more secure compare to RF technologies.

Disadvantages of IrDA (Infrared)

The area for data transfer is very less.

They are used for very short distance applications only.

Due to line of sight communication is blocked by obstacles.

They allow only one device at a time

They require both transmitter and receiver to be in line of sight.

Devices cannot move around while transmission is in progress.

Terminologies useful used in data transmission

Baseband transmission media is the kind of media that can only transmit one signal at a time.

Broadband transmission media is the kind of transmission media that can transmit multiple

signals simultaneously.

Latency is the time it takes a signal to travel from one location to another on a network.

Attenuation is the process by which signals undergo reduction in its strength as it travels

over long distances.

Throughput refers to the amount of data to be transferred from one location to another in a

given amount of time.

Bandwidth is the difference between high frequency and low frequency

257


Crosstalk is a signal transmission issue that causes a disruption in another circuit or channel.

Advantages of using wireless technologies

Wireless technologies overcome inconvenience of using too many wires for

communication.

Wireless technology makes it easy to set up temporary network installations

Wireless increase flexibility and mobility at the work place because works can sit

anywhere with their computers without being limited by the extent of cable connections.

Fast data transfer rates are possible where there are no environmental obstacles

Wireless technology is appropriate to use in places where cabling is practically

impossible.

Disadvantages of using wireless technologies

They are slower than LANs using cabling

They are prone to electrical interference from light and radio

They are subjected to obstruction especially walls

Wireless access point and Wi-Fi technology in general have limited range that is signal

strength decrease as the range increase.

Poor security of data on a wireless network, outsider can easily log on an unsecured

wireless network.

Factors to consider when choosing a communication/transmission media

Speed of data transmission

Cost of transmission media

Installation cost

Data security

Country/company policy

Availability of the communication media in the market

Size of the network

258


Implications of using data communication services

The integration of voice, video and data onto the same networks greatly simplify

networks and enable anyone to access any media at any point

Data communication services bring about standards by ensuring that hardware and

software produced by different vendors can work together.

Successful users of data communication services can gain significant competitive

advantage in the market place since they easily access their partners through faster

communication.

Future trends pervasive networking will change how and where we work and with whom

we do business.

Computer network

A Computer network is the interconnection of two or more computers and other devices for

purposes of sharing information and resources. The computers on a network must be linked by a

medium such as cables, a wireless device or a telecommunications system in order to exchange

data.

259


Why a computer Network?

Purpose of computer networking

To allow users to share information,

To enable sharing of software’s

To allow the users to share resources such as printers, modems, storage devices etc

To enable communication between computers users through tools like e-mail.

To enable data communication I.e. transmission of electronic content over a given

medium

To ensure security of data by putting in place administrative controls over the network

To share databases

Basic requirements for setting up a computer network

These are elements/components that make up a computer network to ensure that there is

communication between them. Among them include;

1. Computers/clients/workstations

2. Network hardware devices

3. Transmission or communication media/channels

4. Network software

5. Server

1. Computers/clients/workstations

These are other computer on the network except the server that sends request and receive

responses from the server

260


2. Network hardware devices

These are devices that handle the movement of data in a computer network.

Modems

Router

Hub

Switch

Gateway

Bridge

Repeaters

Network interface cards

Multiplexer,

A modem

The word "modem" is a contraction of the words modulator and demodulator i.e. Modulation

and Demodulation.

Modulation is the process of converting digital signals into analog signals while Demodulation

is the process of converting analog signals into digital signals.

A modem modulates outgoing digital signals from a computer or other digital device to analog

signals for a telephone line and demodulates the incoming analog signal and converts it to a

digital signal for the digital device.

Therefore a modem is a communication device that converts between analog and digital signals.

There are six types of modems

Dial – up modem

PC Card Modem

261


ISDN (Integrated Services Digital Network) and DSL(Digital Subscriber Lines)modems

Wireless modem

Cable modem

Fax modem

Dial-up modem

A dial-up modem usually is in the form of an adapter card that one inserts in an expansion slot

on a computer’s motherboard. This is the communications device that performs the function of

modulation/demodulation

Dial-up modem automatically dials telephone numbers, originate message sending,

and answer incoming calls and messages.

Both the sending and receiving ends of a standard telephone line must have a dial-up

modem for data transmission to occur.

PC Card modem

This is normally inserted into a PC Card slot of notebook and other mobile computers which

don‘t have built – in modems. The PC Card modem attaches to a telephone outlet with a

standard telephone cord.

Mobile users without access to a telephone outlet also can use a special cable to attach the PC

Card modem to a cellular telephone, thus enabling them to transmit data over a cellular

telephone.

ISDN (Integrated Services Digital Network) and DSL (Digital Subscriber Lines) modems

A DSL or ISDN modem is a communication device that sends digital data and information

from a computer to a DSL or ISDN line and receives digital data and information from a DSL

or ISDN line. ISDN and DSL modems usually are external devices, in which one end connects

to the telephone line and the other end connects to a port on the system unit. Most include built

in connectivity.

A DSL Modem

262


Wireless modem

A wireless modem is a communication device that converts digital data into radio signals and

back.

Fax modem

A fax modem is a communication device that enables a computer to transmit and receive

documents as faxes.

Router

Is an intelligent communications device that sends communications traffic to the appropriate

network using the fastest available path

Hub/concentrator

A hub is a device that connects multiple devices to the network and its function is to send and

receive signals along the network between the devices connected to it by broadcasting the data to

all the devices/computers. It serves as a central meeting place for cables from computers, servers

and peripherals on the network. The entire network shuts down if there is a problem on a hub

263


Switch

A switch is a high-speed device that maintains a bridging table, keeping track of which hardware

addresses are located on which network segment. It maps the internet protocol (IP) address with

the Media Access Control (MAC) address of the LAN card. It sends the data packets only to the

destined computer. Switches are used in the LAN, MAN and WAN.

Gateway

A gateway is a communication device that consist of a combination of hardware and software

that connects networks that use different protocols technologies by performing the required

protocol conversions

264


Bridge

A bridge is a device that links two local area networks that use the same address method or

protocol. It accepts all packets from each network addressed to devices on the other, buffers

them, and retransmits them to the other network.

Repeater

A repeater is a communication device that accepts a signal from a transmission medium,

amplifies it, and retransmits it over the medium in order to overcome attenuation. Hence

repeaters are needed over the medium to boost up these signals

N.B Attenuation is the process by which signals undergo reduction in its strength as it

travels over long distances.

Network interface cards (NIC) or LAN Adapter

A network interface card is an electronic communication device or an expansion card that

enables other devices on a computer to connect to a network.

265


Some NICs are built-in on the motherboard while others are built on a circuit board fitting into

an expansion slot inside the computer. N.B The Type of NIC determines the speed and

performance of a network.

There are three common NICs: Ethernet cards, Local Talk connectors, Token Ring cards

Multiplexer

Multiplexer is a communication device that combines two or more input signals from various

devices into a single stream of data and then transmits it over a single transmission medium.

3. Transmission or communication (Network) media/channels

Transmission or communication (Network) media/channels is also known as communication

links or Data links. It is a medium over which Data travels/ transmitted from one computer

(device) to another.

266

Wireless Network Card


4. Network software

Network software’s are Communication programs that are used in combination with network

devices to enable transmission of data between network terminals. They have features such as

Dialing, file transfer, internet access and others.

There are two categories of network software’s; Network operating system (NOS) and Network

protocols.

Network Operating System (NOS)

A network operating system is a supervisory software program that resides on the server and

controls a network by;

(i) Defining who can use the network

(ii) Determining how information is shared

(iii) Controlling access by multiple users to network resources such as files and hard ware

(iv) Provides for certain administrative functions, including security

Examples of common NOS;

Novell Netware

Microsoft Windows NT,

windows server*,

AppleShare,

UNIX,

Linux

Network operating system carries out the following administration activities:

1. Managing the Security of the network by providing Security features such as authentication,

authorization, logon restrictions and access control.

2. File management.

3. Providing basic operating system features such as support for processors, protocols, automatic

hardware detection and supporting multi-processing of applications.

4. Providing name and directory services.

267


5. Coordinates the activities of multiple computers across a network.

6. Providing file, print, web services, and back-up and replication services.

Network protocols

A protocol is a set of rules and procedure (standard) for connection and data transfer between

devices on a network. Protocols control all aspects of data exchange, which include the

following:

How the physical network is built.

How devices connect to the network.

How the data is formatted for transmission.

How that data is sent/transmitted.

How to deal with errors in data transfer.

The Protocols are created and maintained by a number of different organizations and committees

including:

Institute of Electrical and Electronic Engineers (IEEE),

American National Standards Institute (ANSI),

Telecommunications Industry Association (TIA),

Electronic Industries Alliance (EIA)

International Telecommunications Union (ITU).

Functions of protocol in a communications network

Identifying each device in the communication path

Securing the attention of the other device

Verifying correct receipt of the transmitted message

Determining that a message requires retransmission if it is incomplete or has errors.

Performing recovery when errors occur

Commonly used protocols

TCP/IP-transmission control protocol/Internet protocol.

268


HTTP- Hypertext transfer protocol

FTP- file transfer protocol.

POP- post office protocol

SMTP-Simple mail transfer protocol

IPX/SPX-stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and

SPX are networking protocols used primarily on networks using the Novell NetWare

operating systems

NETBEUI-(NetBIOS Extended User Interface) is a new, extended version of NetBIOS, the

program that lets computers communicates within a local area network. it does not support

the routing of messages to other networks,

Telnet (Telecommunication Network) for Remote access between computers

IMAP; Internet Message Access Protocol.

The Point-to-Point Protocol (PPP) which is a data link protocol commonly used in

establishing a direct connection between two networking nodes.

5. Server

A server is a computer that runs software that enables it to serve specific requests from other

computer (clients).

Implications of using computer networks

Positive implications (advantages)

It facilitates easy communication for instance through electronic mail.

Allow users to log on and access their work from any workstation on the network

Computer network provides rapid method of sharing files instead of using movable disks.

Computer networks enable workgroup computing

It allows software to be upgraded easily on the network since it is done at ago on the

server.

It enable online learning and collaborative research

Computer network allows sharing of data and information stored on any other computer

on the network.

269


It reduces on cost by sharing hardwires and software’s among the network since one

device is jointly used in the network instead of installing a hardware and a software to

each computer.

Negative implications (disadvantages)

Initial cost of installing a network on Cables, network cards, and software are expensive,

and the installation may require the services of a technician.

Networks require Administrative Time and expertise for Proper maintenance of a

network which leads to additional cost.

Time can be wasted on social networks instead of doing meaningful work.

The entire networker fails if the server crashes, When this happens, the entire

organization loses access to necessary programs and files.

There is increased risk of data corruption, since many users will be using the system to

access the same documents, some of whom may be careless or deliberately tamper with

it.

Increased exposure to hackers which puts private data at risk

There is a greater risk from viruses, because they are easily spread between the

computers that are part of the LAN.

A break in the communication channel can stop the entire network.

Different types of computer network

Communication networks can be grouped into the following categories based on the

geographical locations of its computer terminals;

LOCAL AREA networks (LANs)

Metropolitan area networks (MAN)

WIDE AREA networks (WANs)

Wireless local area network (WLAN)

Wireless Wide area network (WWAN)

International network (Internet)

270


Local Area Network (LAN)

A local area network is a network that connects computers and other devices within a small

geographical area such as a room or a building, home a school or a computer laboratory. The

devices are interconnected using a medium such as cables or a wireless medium

Types /categories of local Area Networks (Network Models or architectures)

There are two categories of local area network models or architectures;

Peer-to-peer networks

Clients-server networks

This is an interconnected group of equal computers where there is no hierarchy among them,

each computer acts as both a client and a server to others on the network.

Peer to peer Configurations

Characteristics of peer to peer network

All computers access resources equally.

Each computer stores files on its own storage devices.

Each computer has its own network operating system and application software.

271


It normally connects less than 10 computers together.

It is suitable for home and small scale business users

Each computer has resources it shares with others on the network.

Advantages of a peer to peer network

It is very simple/easy to setup

It is inexpensive to maintain

Do not require additional specialized network administration software

Do not require a dedicated network administrator.

Disadvantages of a peer to peer network

They are not easy to administer

Each user must be trained to perform administrative tasks

Reduced performance because all the devices share resources equally

It doesn‘t allow remote installation of software

It lacks security due to absence of a server.

It’s not appropriate for big networks (cannot be used for big networks).

Clients-server networks

This is a type of local area network that consists of a central computer (the server) on which

other computers (clients) are connected. The central computer providing services to client

computers

272


Characteristics of client server network

It can connect more than 10 computers

It requires a network administrator to manage the network

The server controls communication and shared network resources.

NETWORK SERVER

A server (Network server) is a computer on a network that controls and manages the network

resources, making them available to its clients (computers connected to it).

Client Computer

Client computer is one that is connected to the Network server to receive services from the

server.

Advantages of Client-server network

It offers a reliable centralized storage and sharing of files.

It ensures high security of the network through access controls installed on the server.

It is easy to monitor the network performance on the server

It is easy to solve network problems.

273


It’s cheap to install software which can be done on the server alone instead of all

computers on the network.

Disadvantages of client-server network

It’s expensive to setup.

Extra expenses on buying a server computer

Extra expenses on hiring a network administrator

The server is one point of failure. In case the server fails to work, the whole network

comes to a standstill

NB:

The major difference between peer – peer and client – server network lies in how the

data and information is stored.

Metropolitan Area Networks (MAN)

A metropolitan Area network is a computer network that connects two or more local area

networks together which are geographically separated but in the same city.

Routers, switches and hubs are the hardware devices used to create metropolitan Area network.

Wide Area Networks (WANs)

A wide area network is a network that connects two or more local area networks together over a

large geographical distance such as across districts, cities or regions. WANs make use of a wider

variety of communication media compared to LANs including Telephone lines, Microwave links

(wireless), Satellite connections and fiber optic cables.

274


Wireless local area network (WLAN)

Wireless local area network is a type of network that connects computers and other devices

provides in a small geographical using wireless distribution methods such as radio signals,

infrared or microwave or Bluetooth to communicate between the workstations and other devices.

Examples of wireless local area network devices are;

Wireless adaptor/card

Wireless Access Point

Wireless Bridge

Wireless router

Antennae

Wireless adaptor/card is a device that provides an interface between the network

operating system and an antenna to create a wireless connection to the network.

Wireless Access Point (WAP) is a device that connects wireless communication devices

together to form a wireless network. For a computer to be able to communicate with

wireless device, it must have a wireless network adaptor.

N.B Access Point (AP) is a wireless equivalent of a hub that receives buffers, and transmits data

by means of a wireless antenna between wireless local area network and a wired network

Wireless Bridge (outdoor local area network bridge) is a device used to connect local

area networks in different buildings.

275


Antenna is a structure made of metal rods or wires which receives and sends out radio

and television signals.

Wireless Local Area Network (WLAN) topologies

Wireless Local Area Network can be built with one of the following topologies:

Peer- to – Peer (Ad hoc) topology

Access Point – based topology

Point –to– Multipoint bridge topology

Peer –to- Peer (ad hoc) topology

This is a type of topology where devices are configured to communicate directly to each other.

Access point – based topology

This is a type of topology where access point(s) are used to enable a wireless device to

communicate with any other wired or wireless device on the network.

Access points are used to bridge traffic onto a wired or wireless backbone, or where network

devices are interconnected using access points.

276


Access points

Point – to – multipoint bridge topology

This is a wireless local area network topology where a wireless bridge is configured to connect a

LAN in one building to a LAN in another building even if the buildings are not close together but

within a clear line of sight.

Wireless Wide area network (WWAN)

This is a wireless network over a wide area in which separate areas of coverage are connected

wirelessly.

Examples of Wireless Wide Area Networks equipments especially long distance wireless

Satellite

Microwave dishes

Microwave antennae

277


Wireless application Protocol (WAP)

The Wireless Application Protocol (WAP) refers to a group of related technologies and protocols

widely used as a standard protocol in providing Internet access to mobile phones or other small

mobile devices.

International network (Internet)

Internet is an International/global interconnection of computer networks. It is described as a

network of networks; it is a global network where all LANs (both big and small) worldwide are

interlinked. These networks connect together in many different ways to form the single entity

that we know as the Internet. In fact, the very name comes from this idea of interconnected

networks.

Network topology

Topology is the physical and logical arrangement of a local area network. The physical topology

of a network refers to the physical arrangement of cables, computers, and other peripheral

devices in relation to each other on a network meanwhile Logical topology is the method used to

pass information between workstations on a network.

Types of physical network topologies

Bus network topology

Ring network topology

Star network topology

Hierarchical network topology

Mesh network topology

Hybrid topology

Tree topology

Point-to-Point

Bus topology or linear bus topology

Bus network topology is one that consists of a main, central cable known as the backbone with a

terminator at each end of it where all devices on the network are connected to the main/central

cable.

278


Advantages of Bus topology

It is less expensive than a star topology due to less footage of cabling, only needs one main

cable and no network hubs

It is good for smaller networks not requiring higher speeds

It has a high transmission speed if coaxial cable is used.

It is easy to add new workstations on the net work.

Multiple servers can be used.

Easy to connect a computer or peripheral to a bus.

Requires less cable length than a star topology.

Failure of one device doesn‘t affect others.

Disadvantages of Bus network

It is Limited in size and speed

The Entire network shuts down if there is a break in the main cable.

Difficult to troubleshoot. it is difficult to identify the problem if the entire network shuts

down

It is less secure since all data is transmitted down one main cable.

Transmission slows down as more work stations are added.

If the main cable fails, then all workstations are affected.

279

Bus Network Topology


Ring topology

This is a topology where all devices on the network are connected to one another in the shape of a

closed ring or a loop to form a ring. Data travels in form of a packet from one device to another

device around the entire ring in only one direction until it reaches its final destination.

In a ring topology, there are nodes and the work of these nodes is examined any data that

passes by to see if it is the address; if not, the data is passed on to the next node in the

ring.

Advantages of ring topology

It is a Very orderly network where every device has access to the token and the

opportunity to transmit

It performs better than a star topology under heavy network load

Can create much larger network using Token Ring

It is Cheaper to install than star network as there is only one cable between each

workstation.

High speed can be achieved as each workstation can boast the signal.

Disadvantages of a Ring network

One malfunctioning workstation or bad port in the central hub can create problems for the

entire network

Moves, additions and changes of devices affect the entire network.

Network adapter cards are expensive.

It is much slower than an Ethernet network under normal load

Less secure than star network as data pass through a number of workstations before

reaching its destination.

280


Star topology

A star topology is a type of topology designed where computers and other devices are connected

directly to a central network hub or switch thus forming star.

Data on a star network passes through the hub or switch before continuing to its destination. The

hub or switch manages and controls all functions of the network.

Extended Star topology

This is a network where more than one individual’s star topologies are connected together. At the

center of the star is a hub or a switch. It extends the length and size of the network.

Advantages of Star /extended star topologies

It is suited for large networks

It is easy to expand the network without any negative effects

If one cable or station fails, the entire network is not affected

281


It is easy to install, maintain and troubleshoot because the problem usually isolates itself.

Different types of cables can be used to maximize efficiency.

High speed transmission is possible since each station has a dedicated cable.

Greater security as connection from one station to server is unique.

No disruptions to the network when connecting or removing devices.

Disadvantages of Star/extended star topologies

Breakdown of the switch/Hub becomes a single point of network failure

It’s expensive to set up due to increased cabling costs and the need for a switch or hub.

Mass of cables are needed around in case of a large network.

If the cable fails the workstation cannot receive data via any other route.

The server can get congested as all communication must pass through it

Requires more cable length than a bus topology.

If the hub or switch fails, nodes attached are disabled.

Hierarchical topology

This is a type of topology that resembles extended star topology, except that computer controls

traffic instead of a hub or a switch.

Hybrid Topology

Hybrid topology is combination of two or more different topologies (bus, star, ring, etc.). The

hybrid network is based on both peer-to-peer and client-server relationship.

282

http://www.orosk.com/servers/

http://www.orosk.com/what-is-client/

http://www.orosk.com/peer-peer-topology/

http://www.orosk.com/what-is-network/

http://www.orosk.com/what-is-ethereum-classic/

http://www.orosk.com/ring-topology/

http://www.orosk.com/what-is-bus/

http://www.orosk.com/network-topology/


A hybrid topology is easier to connect to other computers than some other topologies. Also the

hybrid topology has a faster connection.

Advantages of hybrid topology

Very reliable and easy to detect the faulty system.

It is easy to troubleshoot.

It includes both wired and wireless network.

It is expandable network.

Disadvantages of hybrid topology

Its design is difficult to understand.

The cost of this network design is high, because of requirement of lot of cables, cooling

systems, etc.

MAU (Multi-station Access Unit) is required.

It is expensive to install and maintain

Tree topology

A tree topology is a type of network topology that has combined characteristics of bus and star

topologies; it consists of groups of star-configured workstations connected to a bus backbone

cable.

Tree topologies allow for the expansion of an existing network, and enable organizations to

configure a network to meet their needs. It can be used to connect a bus network in buildings onto

283

http://www.orosk.com/what-is-access/

http://www.orosk.com/what-is-mau/

http://www.orosk.com/cables/

http://www.orosk.com/what-is-lottocoin/

http://www.orosk.com/what-is-cost/


star topologies in different buildings.

Advantages of Tree topology

Allows for Point-to-point wiring for individual segments.

Expansion of Network is possible and easy.

It is easy to manage and maintain because the network is divided into segment

Error detection and correction is easy.

If one segment is damaged, other segments are not affected

Disadvantages Tree topology

Overall length of each segment is limited by the type of cabling used.

If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.

Difficult to troubleshoot problem.

This network is not secure, anyone can see transmitted data.

As more and more nodes and segments are added, the maintenance becomes difficult.

Mesh topology

This is a network where each device has its own connections to all other devices on the network.

It provides each device with a point-to-point connection to every other device in the network.

Data sent on a mesh network can take any of the several paths from the source to the destination.

284

http://www.orosk.com/what-is-data/


Advantages of Mesh topology

A mesh topology provides much protection from interruption of service because of

possible routes through the network that is the damage of one or several cables or

computers may not have vital impact except the involved computers

Mesh networks provide redundancy, in the event of a link failure; meshed networks

enable data to be routed through any other site connected to the network.

Disadvantages Mesh topology

Much cabling is needed hence expensive

Not easy to troubleshoot incase of failure

Not easy to install.

It is the most expensive and difficult to maintain topology because each device has a

point-to-point connection to every other device.

The damage of at least one cable or device may damage the network seriously If there are

only few cables in the network

Point-to-Point Topology

Point-to-point (PTP) topology is a type of topology that connects two nodes directly together.

285


The following examples are pure point to point links:

Two computers communicating via modems.

A mainframe terminal communicating with a front end processor.

A workstation communicating along a parallel cable to a printer.

Summary of physical types of topologies

Logical topology (Media Access Method)

Logical topology is how computing devices access the network and send data over the network.

The logical topology of a network determines how the devices communicate across the medium.

There are four commonly used media access methods:

A. Ethernet,

B. Token Ring,

C. Local Talk, and

D. Fiber Distributed Data Interface (FDDI)

E. Packet switching

F. Circuit switching

286


Ethernet

Ethernet is a type of local area network technology that uses coaxial cable or special grades of

twisted pair wires. Ethernet is also used in wireless LANs.

Token Ring

A network topology developed by IBM in which computers access the network through token-

passing.

A Token is a special packet that contains data and acts as a messenger/carrier between each

computer and device on a ring topology.

Each computer must wait for the token to stop at its node before it can send data over the

network so as to avoid collision of data packets on the network.

Token passing

287


Local Talk

Local Talk is a network access method designed by Apple Computer, Inc. specifically for

networking Macintosh computers • It provided a simple, cost-effective way of interconnecting

Macintosh devices • Local Talk uses a transmission method called Carrier Sense Multiple Access

with Collision Avoidance (CSMA/CA) • Local Talk relies on the AppleTalk protocol, but it may

also support the Macintosh version of TCP/IP called Mac TCP.

FDDI (Fiber Distributed Data Interface)

FDDI is a network topology that is used primarily to interconnect two or more local area

networks, often over large distances.

It uses fiber optics for speeds of up to 100 Mbps. It is used primarily to interconnect two or more

LANs, often over long distances

It also employs Token Ring passing process to transmit data; but use a dual counter-rotating ring

topology, meaning there are two rings of cable with two tokens circulating in opposite directions.

Packet switching

This is a data transmission technique which involves transmitting and routing of messages by

dividing the electronic message/data into packet segments and sending them rapidly and

sequentially over a network channel which are then reassembled into the original message at

their destination.

It involves breaking the data into individual segments known as packets which are transmitted

individually and then re-assembled when they reach the destination computer.

288


Circuit switching

Circuit switching is a method of communicating in which a dedicated communications path

referred to as a circuit or channel is established between two devices through one or more

intermediate switching nodes before communication between the devices takes place.

Each circuit that is dedicated cannot be used by others on the network until the circuit is released

and a new connection is set up. The telephone system uses circuit switching.

Summary Chart:

Physical Topology Common Cable Common Protocol

Linear Bus Twisted pair, Coaxial & fiber Ethernet & Local Talk

Star Twisted pair & Fiber Ethernet & Local Talk

Star-Wired Ring Twisted pair Token Ring

Tree Twisted pair, Coaxial &fiber Ethernet

Factors to consider when choosing a network topology

Cost of installation. A linear bus network may be the least expensive way to install a

network; you do not have to purchase concentrators.

Number of computers and other devices to connect/size of the organization

289


The architecture of the building to be used

The purpose of the network

Distance of connectivity

Safety provisions of the network

Personnel provisions/technicalities involved

Ease in accessing the network

Length of cable needed. The linear bus network uses shorter lengths of cable.

Future growth for instance with a star topology, expanding a network is easily done by

adding another concentrator

Cable type to use that is the most common cable in schools is unshielded twisted pair,

which is most often used with star topologies.

Network and Data security

Network and data security consists of the provisions made on computer network and policies

adopted by the network administrator to protect the network and the network-accessible

resources from unauthorized access to data, as well as guarding against Data loss and the

effectiveness (or lack) of these measures combined together.

Common computer Network problems and troubleshooting

Internet protocol (IP) conflicts that is when two computers are assigned the same IP

address erroneously

Solution: change the IP address for one of the computers.

Absence of connectivity

Solution: checking the physical connections and connection devices. And the distance between

devices in case of wireless network.

Check the router or hub to see if some machine is disconnected, or if it a case of is a faulty cable.

In this case: a good connection is shown by a green light.

Ensure that TCP/IP is configured.

290


Ensure all the computers on the network are within the same subnet with individual IP addresses.

Check if the file and printer sharing option is installed and functioning, and also define network

shares on each computer.

Slow connectivity: This can be due to i) collisions, which the network is incapable of

handling. ii) Heavy file transfers bring down the speed tremendously. iii) the network

card may also be overloaded.

The Solution: i) zip bulky files while transferring, which lower the pressure on the network.

ii) Check if the network card is not suspended in the transmit mode, which indicates that the

card is working overtime. All you need to do in such cases is, to replace the faulty components.

Firewall settings can interfere with file sharing on connected computers. It is true

that disabling security features can make your system vulnerable to attacks, but lowering

security levels should not cause too much trouble.

The Solution: Rigid Firewall settings need to be adjusted to allow networked computers to share

data. You may consider disabling the security settings temporarily, after having thoroughly

considered all security related threats.

Factors that affect the rate of transmission on a network

Several factors that can negatively affect latency include the distance between the two points, the

type of transmission media, and the number of nodes through which the data must travel over the

communications channel. For best performance, bandwidth should be high and latency low;

Frequency and bandwidth of the medium;[rate of transmission]. The higher the frequency, the

wider the bandwidth, the more data will be sent over a medium and vice versa.

NB; Bandwidth; is the difference between the highest frequency and the lowest frequency.

Line configurations; these are either point – to – point or Multipoint. A point – to – point

connects the sending and receiving devices such that a terminal with a central computer.

291


A Multipoint line is a single line that interconnects several communications devices to one

computer. Data moves faster in a point – to point than in a multipoint.

Serial and parallel transmission

In serial transmission, bits are transmitted sequentially, one after the other. In parallel

transmission, bits are transmitted through separate lines simultaneously. Therefore, data

transmission is faster in parallel transmission than in serial.

Direction of transmission

This can be simplex, half duplex or full duplex. In simplex, data can travel only in one direction.

In half duplex, data travels in both directions but only one direction at a time. In full duplex, data

travels back and forth at the same time.

Transmission mode

This can be either asynchronous or synchronous. In asynchronous transmission, data is sent one

byte (character) at a time. In synchronous transmission, large quantities of data are transmitted at

ago at regular intervals.

Packet switching

A packet is a block of data for transmission over a network. Packet switching is a technique for

dividing electronic messages into packets for transmission over a network to their destination

through the most convenient route. It can handle high volume of traffic in a network; It allows

more users to share a network, thereby offering cost savings.

Protocols (rules for data transmission)

A protocol specifies the type of electrical connections used the timing of message exchange,

error detection techniques; specify how the receiving devices will acknowledge sending devices

(handshaking) etc.

292


Network topology

There may be data collisions in a bus topology hence slowing down the network. A star and ring

topology has fewer collisions and usually runs faster.

Capacity of hardware in the network

The speeds of hubs, switches and NICs will greatly determine the speed of the network.

The server

The amount of RAM installed in the server and the speed of the hard disk greatly affects the

speed of the network.

Location of software and files

If software is stored on the workstation hard disks, it increases (speeds up) performance and

reduces network traffic.

Qn .Differentiate between standalone computers and networked computers

A standalone computers are computers that are not connected to a network and is capable of

performing the operations in the information processing cycle meanwhile Networked computers

are computers designed specifically to connect to a network especially the internet.

TOPIC 11: INTERNET AND WORLD WIDE WEB

Definition of internet

Internet is an International/global interconnection of computer networks It is described as a

network of networks; it is a global network where all LANs (both big and small) worldwide are

interlinked.

These networks connect together in many different ways to form the single entity that we know as

the Internet. In fact, the very name comes from this idea of interconnected networks.

293


History of the Internet

The Internet was originally developed in the late 1960’s by the US government department of

defense to improve secure communication between its military computers and enhance the

sharing of information and collaboration on military and scientific projects in four locations;

universities of California, Los Angeles, Santa Barbara, Utah and Stanford research institute.

This internet was known as ARPANET (Advanced Research Projects agency Network).

Characteristics of internet

It is made up of numerous networks worldwide.

There is No organization that has a direct control over the Internet.

It is dynamic; ever changing.

It offers very many services

The Internet size and technology is growing at a very faster rate.

It is not owned by any single organization (has no central control.

Advantages of using internet

The biggest benefit offer by internet is that it is a source of all valuable information

The primary goal of internet is communication because it offers a speedy communication

through the use of e-mail

294


The internet is now the most popular form of entertainment. Movies, songs, videos,

games etc. is available and can easily be downloaded from the internet

Internet has facilitated social networking that is the sharing of information to people

across the world. Any job vacancy, emergency news, ideas etc. can be shared in the

social networking websites such as Face book, what saps, twitter etc

As far as learning is concern, internet has now become a part of education in the sense

that online studies, e-library, uploading educational information’s, and research can

easily be carried out using internet.

All business deals can be carried in the internet like transaction of money that is e-money,

online reservations, online ticket booking for movie, online shopping, advertising for

goods and services.

Disadvantages of using internet

Internet leads to the loss of information that is information crucial to us or any important

files can be easily taken by the hackers.

Internet offers high possibility for the fraudulent people to easily access personal details

such as names, address, credit card number etc

Networked computers connected to internet are susceptible to virus attack leading the

crushing of the hard disk and alternate the normal behaviors of the computer.

Internet allows any body to access and down unnecessary materials and pornographic

photos and films hence leading to moral degeneration in the society

Internet had led to social disconnecting in the society that is reduction into face to face

interaction for example the use of social media such as face book, what sap, twitter etc.

Internet has also led to the distribution of unwanted bulky e-mails (spamming)

Uses of internet as a learning tool

Used to search for information using search engines and directories

E-mail system is used in collaborative learning.

Enables distance learning for those who are unable to attend collage/school physically.

Allow discussions over educational chat rooms.

295


Enables downloading of relevant documents.

Using computer assisted assessments (CAA) for online exams.

It enables the use of electronic libraries and textbooks.

Development of skills of research and communication by the students.

Assignment are received, done and sent across the network by the students.

Video conferencing is used to share views and ideas among students and teachers.

Advantages of internet in schools

A lot of information is obtained which is not available in a single textbook.

Updated or current information is obtained since internet is dynamic.

Learning is fun and easy as internet is exciting due to the multimedia content used.

It offers different sources of information hence a variety of opinions on a topic.

It is a quick way of getting information where internet connection is good.

It encourages group work through collaboration therefore sharing of information and

experience among students and teachers.

Related topics are easily accessible through hyperlinks.

Students are able to attend virtual classes.

Different skills such as typing, use of web browsers, problem solving, E-mail are

developed through the use of the Internet.

Instant or timely communication is done by use of the E-mail system.

Shopping for item such as books is made easy and less expensive.

Disadvantages of the Internet in schools

No Information control over the Internet such that all sorts of bad information is

accessed.

There is no privacy of information and information piracy is common.

Indecent materials are published on the Internet.

It’s not readily available to most people.

It is expensive to access drains school resources.

Time is lost where Internet speed is low due to poor links, hardware and congestion.

296


Some sites give outdated therefore misleading information because they are not regularly

updated.

Time wasting occurs when students easily stray into non essential materials.

Many Internet sites have been commercialized therefore emphasize adverts and selling

such that less free academic content is given.

Computer viruses can easily spread over the Internet.

Difficult to obtain information relevant to a particular level of a student.

It is possible to obtain contradictory information.

Many students and teachers do not have adequate skills of accessing the Internet.

Possible solutions to Internet issues

Use of firewalls against illegal access to networks

Use of updated antivirus software against viruses

Use of anti spyware against hackers.

Carefully choosing an ISP who will provide the best service within your means.

Installing filters against pornographic and other undesirable content.

Use of encryption software to protect sensitive information and prevent fraud.

Use of complicated passwords to restrict access to.

Use of digital certificates. This is a means of authenticating that an organization is genuine

and that any transaction undertaken with it will be honored. The certificate contains the name

of the organization and a serial number registered with a Certification authority who issues

the certificate.

Internet protocols

The Internet Protocol (IP) is the method or a standard set of rules for sending and receiving data

from one computer to another on the internet. For a computer known as Host to be recognized by

other devices, it must have an internet protocol address.

Internet protocol (IP) address is a number that uniquely identifies each compute on the internet.

IP address consists of four groups of number, each separated by periods e.g. 192.168.5.6. The

first three values that 192.168.5 usually identifies the network and the last value that 6 represent

the specific computer

297


Examples of internet protocols

Transmission communication protocol/internet protocol (TCP/IP)

Hypertext transfer protocol (HTTP)

File transfer protocol (FTP)

Basic requirements for internet connection

Host computer

Communication hardware such as Modem and router.

Communication Software such as a Web browser and internet protocols

Communication media such as VSAT, wireless antenna or telephone line.

Internet Service provider(ISP)

Internet service providers

Internet service provider (ISP) is a company that provides connection and services for accessing

and using the Internet at a monthly subscription fee.

Examples of internet service providers in Uganda

Airtel Uganda limited

Mtn Uganda limited

Africel Uganda limited

Uganda telecom limited (UTL)

Roke Uganda limited

Infocom Uganda limited etc

Services offered by internet service providers

They offer internet access and internet connectivity

They do system analysis and consultancy

They provide network servicing and maintenance

They Provide network security

They provide other services like website hosting

They facilitate domain name registration

They provide electronic mail services

They facilitate video conferencing

298


Factors to consider when choosing an internet service provider (ISP)

Setup costs

Experience for both ISP and client.

Auxiliary/additional services offered by the ISP e.g. E – Mail/telephone SMS facility.

Availability of online help.

Compatibility of ISP software with yours e.g. windows Vs Linux Vs Wang.

Efficiency/Effectiveness of ISP devices e.g. speeds of ISP modem, Bandwidth etc. cabling

architecture, Bit–Bus architecture for devices etc.

Available technology. For example, In case you intend to hire a dial-up service, you need to

consider the availability of a local phone number or toll-free number for access; this would

help to reduce cost of acquiring totally new technology or equipment.

You also need to consider the Technology offered by the ISP. Some technologies are older

and less efficient than others. The ISP should be able to offer the latest and most efficient

technology.

Technical support. What kinds of support services can the ISP provide; Are there any

additional charges for support?

The terms of service. You need to consider the terms of services offered by the ISP and

determine whether they meet your expectations or not, for example, is there a limit to the

number of hours per month you can use the service or is there a limit to the amount of

download or upload per month?, does this fit well within your needs?

Other services offered by the ISP that you can have on top of internet connection. E.g. web

hosting and domain services.

The fee charged for the services. What is the monthly fee for the service? Are there any

additional equipment or setup fees? What is the fee for extra e-mail accounts web site

hosting, and how do the costs compare with other service provider companies?

The size of the ISP’s Client base. ISP capacity is usually limited, the bigger the client base

the less reliable is the ISP.

Coverage. Does the ISP coverage reach your location or not?

299


Your Internet service needs. Suppose all you need to do is check e-mail and read web pages,

a dial-up connection may be enough. But most people also want to download music,

television shows, or watch videos. For these, you will need a faster connection with

broadband access, such as a digital subscriber line (DSL), a cable modem, or satellite.

Common terminologies used in internet connection

Dial-up (dun)

Bandwidth

Broadband internet access

Cable modem

Leased line

Bit rate

Dial-up (DUN)

This is a connection method where the client must request for a connection to the ISP server each

time he wishes to access the Internet.

Leased line

This is where there is a permanent connection between the user and the ISP at a fixed fee. This

connection normally uses digital subscriber line (DSL) technology

Cable modem

A cable modem is a type of modem that provides access to a data signal sent over the cable

television infrastructure. Cable modems are primarily used to deliver broadband Internet access,

taking advantage of unused bandwidth on a cable television network.

Broadband Internet access

Broadband Internet access (broadband) is high-speed Internet access.

Bandwidth

Bandwidth is the amount of Data that can be transmitted along a communication channel in a

given period of time which is measured in bits per second. The larger the range of frequencies, the

greater the amount of data that can be transmitted

Bit rate

300


Bit rate is the speed at which a particular transmission is taking place. It is measured in bits per

second (bit/s or bps) and represents the actual speed of transfer of data.

Factors that determines the internet access speed

The amount of bandwidth allocated by ISP.

Connection technology used; telephone lines are much slower than newer technology such

as ISDN and ADSL.

The volume of traffic. The more the number of people logged on the internet the slower

the internet speed.

Adapter or modem speed used.

The processing speed and amount of RAM of the host computer

Type of data/files being downloaded or uploaded.

The age of computer set, whether clone or new

Services offered by internet communication

Chat rooms

Mailing lists


Internet Relay chat (IRC)

News group

Message board (Internet forum)

Voice over internet protocol (VoIP)

Usenet

Video conferencing

Telnet

Electronic commerce (e-commerce)

Social network

Internet banking (e-banking)

Search Engine (Web Search)

Wikis and blogs

Discussion boards

Portals.

Podcasts.

E- Libraries

Electronic waste (e-waste)

E-mail

World wide web (www)

Chat rooms

A chat room is an online service that permits users to chat (converse) with each other

through the internet, traditionally in plain text only by typing lines of text in the

computer.

301


To start a chat session, a user must connect to a chat server through a chat program on his or her

computer. Some chat rooms support voice chats and video chats.

More recent developments in Web technology now allow the transmission of images

and emoticons in a chat room as well. Some chat rooms require a username and

password combination in order to log in or join a conversation, allowing for privacy

among the users.

Mailing lists

A mailing list also known as an email list or electronic mailing list is a collection of names and

addresses used by an individual or an organization to send material to multiple recipients. Rather

than individually sending an email to each user, mailing lists send email to specific user groups

through a single email message. The term is often extended to include the people subscribed to

such a list, so the group of subscribers is referred to as "the mailing list", or simply "the list".

Mailing lists are generally used as a means to share content, news and any

product- or service-related information with subscribers that is when a message is

sent to a mailing list, every person in the list will receive a copy of the message.


Instant messaging (IM) technology is a type of online chat that offers real-time text

transmission over the Internet between two parties, when each user chooses to

complete a thought and select "send".

Internet Relay chat (IRC)

Internet Relay Chat (IRC) is a text based communication

system that allow people to chat with one another on the Internet within the chart room. It allows

people within the same chart room to send and receive instant message

News group

302

https://simple.wikipedia.org/wiki/Internet


A newsgroup also called a discussion group is an online discussion forum accessible

through Usenet about a particular subject. To participate in a discussion, a user sends a

message to the news group and other users in the news group read and reply to the

message.

Internet forum (Message board)

An Internet forum, or message board, is an online discussion site where people can hold

conversations in the form of posted messages. They differ from chat rooms in that messages are

often longer than one line of text, and are at least temporarily archived.

Voice over internet protocol (VoIP)

Voice over Internet Protocol (also voice over IP, VoIP or IP telephony) is a methodology and

group of technologies for the delivery of voice communications and multimedia sessions

over Internet Protocol (IP) networks, such as the Internet.

Usenet

Usenet is a collection of newsgroup where the users can post messages and these posted

messages are distributed via Usenet servers. Each server holds the posted messages for a certain

period of time which is also known as retention time. Usenet can be compared with an internet

forum, but the main difference is that the messages are not stored in one server and are only

available for a certain amount of time.

Video conferencing

Video conferencing (or video conference) is a mean of conducting a

session/conference/discussion using a set of telecommunication technologies between two or

more participants at different geographical locations by using computer networks to transmit

audio and video data. Each participant has a video camera, microphone, and speakers mounted

on his or her computer. As the two participants speak to one another, their voices are carried over

the network and delivered to the other's speakers, and whatever images appear in front of the

video camera appear in a window on the other participant's monitor.

Telnet

303

https://www.webopedia.com/TERM/M/monitor.html

https://www.webopedia.com/TERM/W/window.html

https://www.webopedia.com/TERM/D/data.html

https://www.webopedia.com/TERM/V/video.html

https://www.webopedia.com/TERM/N/network.html

https://www.webopedia.com/TERM/C/computer.html

https://en.wikipedia.org/wiki/Internet

https://en.wikipedia.org/wiki/Internet_Protocol

https://en.wikipedia.org/wiki/Voice_communication

https://en.wikipedia.org/wiki/Chat_rooms

https://en.wikipedia.org/wiki/Online

https://techterms.com/definition/usenet


Telnet is a protocol used on the Internet or local area networks to provide a bidirectional

interactive text-oriented communication facility using a virtual terminal connection.

Electronic commerce (e-commerce)

E-commerce (electronic commerce or EC) is the buying and selling of goods and services, or

the transmitting of funds or data, over an electronic network, primarily the internet. These

business transactions occur either as business-to-business, business-to-consumer, consumer-to-

consumer or consumer-to-business

Business – to - Consumer (B2C)

This is a business transaction model that applies to any business that sells its

products or services to consumers over the internet.

Consumer – to Consumer (C2C)

This is a model that applies to sites primarily offering goods and services that

assist consumers interacting with each other over the Internet.

Business – to – Business (B2B)

Is the e – commerce which consists of businesses buying from and selling to each other

over the internet.

Consumer – to – Business (C2B)

This transaction applies to any consumer that sells a product or service to a business

over the internet.

Examples of transactions conducted online

Online shopping

Online banking

Advantages of e – commerce

It operates 24 hours a day hence transactions can be conducted at anytime.

Information about a product can be changed and be available quickly (i.e. it is easy to

update)

It gives immediate feedback

304

https://en.wikipedia.org/wiki/Text_terminal

https://en.wikipedia.org/wiki/Local_Area_Network

https://en.wikipedia.org/wiki/Internet


Allows manufacturers to buy and sell their products directly hence avoiding the cost of

middlemen.

Customers can easily compare prices.

It allows business to gather customer’s information, analyze it and react appropriately.

Businesses have access to millions of people with internet connections.

It widens the market easily. It can work globally hence saving time for participants on

both ends.

Distribution costs for information is reduced or completely eliminated.

It allows business companies to advertise for their products easily.

Social network

This is a dedicated website which enables users to post comments, and communicate with each

other to share their interests, ideas, stories, photos, music, and videos with other registered users

via internet by using social media such as face book, Twitter, MySpace, Bebo. Instagram, what

sap etc.

Bebo is a popular social networking site where users can share photos, stories, their journal, and

more with friends and family privately or publicly on the Internet.

Classmates is one of the largest and most used websites for connecting people who graduated

from a high school and allows you to keep in touch with them and any future reunions.

Face book is a popular destination for users to set up personal space and connect with friends,

share pictures, share movies, talk about what you're doing, etc.

Instagram is a mobile photo sharing service and application available for the iPhone, Android,

and Windows Phone platforms.

LinkedIn is one of the best if not the best locations to connect with current and past co-workers

and potentially future employers.

Twitter is another fantastic service that allows users to post 140 character long posts from their

phones and on the Internet.

Internet banking (e-banking)

305

https://www.computerhope.com/jargon/t/twitter.htm

https://www.computerhope.com/jargon/i/instagram.htm


Internet banking also known as electronic baking or online banking is an electronic payment

system that enables customers of a bank or other financial institutes to conduct a range

of financial transactions through the financial institution's website.

It is a method designed to enable the customers to have easy and safe access to the bank account

in order to carry out online transaction services electronically via the Internet.

Internet banking enables the following:

Accurate statement of all means available in your bank account

Statement of current account, credits, overdrafts and your deposits

Execution of national and international transfers in various currencies

Execution of all types of utility bill payments (electricity, water supply, telephone bills,

etc...)

Carrying out customs payments

Electronic confirmation for all transactions executed by E-banking

Management of your credit cards

Search Engine (Web Search).

Search engine is a service that allows Internet users to search for content via the World Wide

Web (WWW). A user enters keywords or key phrases into a search engine and receives a list of

Web content results in the form of websites, images, videos or other online data.

It is a software program or script available through the Internet that searches documents and files

for keywords and returns the results of any files containing those keywords. Today, there are

thousands of different search engines available on the Internet, each with their own abilities and

features and the most popular and well-known search engine is Google. Other popular search

engines include AOL, Ask.com, Baidu, Bing and Yahoo.

Wikis and blogs

A wiki is a website that allows multiple users to create, modify and organize web page content in

a collaborative manner via their web browsers. Wiki documents can be modified by anyone with

access to the website. It's a shared-authorship model; users can add new content and revise

306

https://www.computerhope.com/jargon/y/yahoo.htm

https://www.computerhope.com/jargon/b/bing.htm

https://www.computerhope.com/jargon/a/ask.htm

https://www.computerhope.com/comp/aol.htm

https://www.computerhope.com/jargon/g/google.htm

https://www.computerhope.com/jargon/i/internet.htm

https://www.computerhope.com/jargon/s/script.htm

https://www.computerhope.com/jargon/p/program.htm

https://www.computerhope.com/jargon/s/software.htm

https://en.wikipedia.org/wiki/Financial_transaction

https://en.wikipedia.org/wiki/Bank

https://en.wikipedia.org/wiki/Electronic_money

https://en.wikipedia.org/wiki/Electronic_money


existing content without asking for permission to do so. One of the largest and best-known

examples of a wiki is the Wikipedia free online encyclopedia.

A blog is a website where users post journal-like entries that are displayed in reverse

chronological order, with the most recent posting at the top of the page. Blogs can take the form

of online diaries, personal chronicles, travel logs, newsy columns and reports from special

events. They can include graphics, pictures, and even music and video clips.

Discussion boards

A discussion board is known by various other names such as discussion group, discussion forum,

message board, and online forum). It is a general term for any online "bulletin board" which

allows members to hold discussion online about a particular topic. Discussion is started by one

member posting a topic and other members of the same group begin to reply by sharing

information and ideas.

Portals.

A Web portal is a specially designed website that brings information from diverse sources, like

emails, online forums and search engines, together in a uniform way. Usually, each information

source gets its dedicated area on the page for displaying information (a port let); often, the user

can configure which ones to display. The extent to which content is displayed in a "uniform way"

may depend on the intended user and the intended purpose, as well as the diversity of the

content. Examples of portals include; HotBot, Alta Vista, Go.com, iGoogle, Excite, Yahoo etc.

Podcasts.

A podcast, or generically net cast, is an episodic series of digital audio or video files which a user

can download and listen to. It is often available for subscription, so that new episodes are

automatically downloaded via web syndication to the user's own local computer, mobile

application, or portable media player. It is distinct from Internet radio, which involves streaming

rather than downloading.

E- Libraries

307

https://en.wikipedia.org/wiki/Streaming_media

https://en.wikipedia.org/wiki/Internet_radio

https://en.wikipedia.org/wiki/Portable_media_player

https://en.wikipedia.org/wiki/Web_syndication

https://en.wikipedia.org/wiki/Download

https://en.wikipedia.org/wiki/Download

https://en.wikipedia.org/wiki/Computer_file

https://en.wikipedia.org/wiki/Digital_video

https://en.wikipedia.org/wiki/Digital_audio

https://en.wikipedia.org/wiki/Digital_media

https://en.wikipedia.org/wiki/Episode

https://en.wikipedia.org/wiki/Portlet

https://en.wikipedia.org/wiki/Website


E-Library /Digital Library is a set of documents available through electronic means by the use of

digital technologies that allow for the retrieval, archiving, preservation, and dissemination of

those documents .It is a special library with a collection of digital objects that can include text,

visual material, audio material, video material, stored as electronic media formats as opposed to

print, or other media.

Electronic waste (e-waste)

Electronic waste is a term abbreviated as "E-Waste” which refers to the disposal of broken or

obsolete electrical and electronic equipments (EEE) and its parts that have been discarded by the

owner as waste without the intention of re-use them.

Netiquette

Netiquette is a short form of network etiquette or Internet etiquette. Netiquette is a combination

of the words network and etiquette, and is defined as a set of rules for acceptable online

behaviors. Similarly, online ethics focuses on the acceptable use of online resources in an online

social environment.

In general, netiquette is the set of professional and social etiquettes practiced and advocated in

electronic communication over any computer network. Common guidelines include being

courteous and precise, and avoiding cyber-bullying. Netiquette also dictates that users should

obey copyright laws and avoid overusing emoticons.

Rules of netiquette

Keep messages brief by using proper grammar, spelling and punctuation.

Be careful when using sarcasm and humor as it might be misinterpreted.

Be polite and void offensive languages.

Read the message before you send it.

Use meaningful subject lines

308


Avoid sending or posting flames, which are abusive or insulting messages.

Avoid sending spam, which is the internet‘s version of junk mail.

Do not use all capital letters which is equivalent to SHOUTING!

Read the FAQ (Frequently Asked Questions), if one exists. Many news groups and

web pages have a FAQ.

Do not assume material is accurate or up-to-date. Be forgiving of other’s mistakes.

Never read someone’s-mails.

Differentiate between internet, intranet and extranet

Electronic mail (e-mail)

Electronic Mail is a method of exchanging messages between people using electronic devices. In

order for any two users to receive or exchange E-mail messages online, they must have E- mail

addresses.

E – Mail address

E-mail address is a set of characters such as letters, number, symbols etc that are required to send

and receive emails

Parts of an email address

Email address consist of four parts;

Consider this email address: [email protected]

1. Username: tobbyecat

2. @: at

3. Domain name: Gmail

4. Top level domain: com

Username:

A username is a name that uniquely identifies someone account on the email server that handles

the email.

@:

309


It separates username or account name from the name of the mail server.

Domain name:

It consists of Email server name (Gmail, yahoo, hotmail) that comes after the @ symbol in

an email address

A top level domain:

A top level domain refers to the last segment of a domain name, or the part that follows

immediately after the "dot" symbol. It usually a three letter extension which shows the type of a

particular organization.

Examples of top level domain names

Top-level domain name Purpose of host.com a business or commercial enterprise (trying to make money).ac an academic institution or a university.edu host is an educational institution.org a non-commercial organization.mil Military.net for network(ISP).gov Government

Country-codes Country.ca Canada.au Australia.nz New Zealand.ug Uganda.uk United Kingdom.za South Africa

Sending and receiving of an email

To send and receive emails, both the sender and the recipient must have the right tools.

An internet connection

An email address

An email client

Email client is software that runs on a personal computer and relies on an internet

connection to perform some of its operations.

It works with ISP (Internet Service Provider) that uses standard internet email protocols

that make i possible for people using different email client software to communicate with

310


one another.

Features of an email account

After successful signing in, the email service provider automatically provides your

account with features like:

Inbox for incoming massages

Outbox for outgoing massaged

Address box for storing your personal email address etc

Email message

An email message is a text, typically brief and informal, that is sent or received over a computer

network including attachments (such as image files and spreadsheets). Email message can be

sent to multiple recipients at the same time.

Email message comprises of the 3 parts, these are:-

1. Message Header

2. Message Body

3. Message Envelope

Message Headers

The message headers contain information concerning the sender and recipients. The exact

content of mail headers can vary depending on the email system that generated the message.

Generally, headers contain the following information:

From: Contains the E-mail address and the actual name of the sender of the e-

mail message.

To: Contains the E-mail address and the actual name of the recipient of the e-

mail message

Date: Contains the date and time when the E-mail message is sent.

Cc: Carbon Copy

Contains another E-mail address (es) of recipients to whom the same copy of the

E- mail message is being sent.

The recipients of such an E-mail are able to view the e-mail addresses of all

the other recipients who have received the same mail.

311


Bcc: Blind Carbon Copy

Contains another E-mail address (es) of recipients to whom the same copy of the

E- mail message is being sent.

But the recipients of such an E-mail are not able to view the e-mail addresses of all

the other recipients who have received the same email.

Subject: Contains the main theme/topic/content of the mail message.

Text area: This is the main area where the user enters/ types text to be sent as the

main mail.

Attachment: This is the area that enables the user to link non textural documents e.g.

photos, music, videos etc. to the email message to be sent together.

Send: This is the tab that issues instructions to clients email software to post the

massage

Message Body

The email body is the main part of an email message. It contains the message's text, images and

other data (such as attachments)

The message body must include salutation, the actual message, complimentary close, and a

signature or automatically generated text that is inserted by the sender's email system.

Message Envelope

When email is handed over from the sending computer to the receiving computer, the sending

computer declares a sender address (the “envelope-from", which is the address that

bounce messages will go to if delivery fails at a later stage) and one or more recipient addresses

("envelope-to").

Notice: For one to create email address and access to e-mail via the Web, he or she is required to

enter a username and a password.

A username is a name that uniquely identifies someone account on the email server that handles

the email.

A password is a private combination of characters associated with the user name that

allows access to certain computer resources or to a network. The password helps to

312


ensure that unauthorized users do not access the computer.

Characteristics of a good password

Should be easy to remember but not too obvious.

Should be longer, at least eight characters.

Should have a combination of mixed case letters and digits.

Should be easy to type without looking at the keyboard.

Avoid the followings with a password

Using your name, birthday, ID card number or telephone number.

A password of all digits or all the same letter.

Safeguarding your password

Do not share your password with others

Do not write down your password

Change your password frequently

Advantages of email

It is very quick to communicate quickly with anyone on the Internet.

It is a cheap means of transferring files.

Other computer files can be attached to the email.

Records and copies are kept automatically online.

Can be picked up anywhere in the world.

Can be sent at any time to its destination (it works24-7)

You can deal with your email at a convenient time.

You can send letters, notes, files, data, or reports all using the same techniques.

Disadvantages of an email

A computer and other hardware such as a modem are required hence expensive

It is not secure

It is easy to get on junk (useless) mail lists.

Email isn't necessarily private. Since messages are passed from one system to

another, and sometimes through several systems or networks, there are many

opportunities for someone to intercept or read email

313


Some email systems can send or receive text files only.

It's possible to forge email. This is not common, but it is possible to forge the address

of the sender. You may want to take steps to confirm the source of some email you

receive.

It's difficult to express emotion using email. The recipient doesn't have the benefit of

seeing your facial expressions or hearing your voice.

In case of any error in the address, email cannot be delivered.

Email consumes a lot of time hence promoting laziness

Parcels cannot be delivered via email which limit its usability

World Wide Web (www)

The World Wide Web (abbreviated as WWW or the Web) is an information space where

documents and other web resources are identified by Uniform Resource Locators (URLs),

interlinked by hypertext links, and can be accessed via the Internet. It is where all the Web pages,

pictures, videos and other online contents can be accessed via a Web browser.

Common terms used in World Wide Web

Web page

Web server

Web master

Hyperlinks

Web publishing software

Domain name

Uniform Resource Locator (URL)

Web browser

Search engine

Website

A web page

A web page is an electronic document or files of information stored on the web /website that

contain text, animations, audio, and video (i.e. multimedia elements), as well as built – in

connections (called hyperlinks) to other documents.

A web server

A web server is a computer that keeps and delivers web pages requested by users.

314


A webmaster

A web master is an individual person responsible for creating, managing and developing web

pages and maintaining a website.

Hyper links

These are built-in links to other related documents, allowing users to quickly navigate

from one document to another when clicked

Hyper text

Hyper text is a web page that has hyperlinks to other WebPages program used to access and view

web pages.

Homepage

Home page is the first page (starting page) or the table of contents of a website.

Web publishing software

Web publishing software is specially designed software designed for creating web pages

that contain text and multimedia elements. Examples include: Microsoft FrontPage,

Macromedia Dreamweaver, Adobe Go Live, Adobe Page mill etc.

Domain name

A domain name is the address which allows the Internet users to access a website. A domain

name is a website name. A domain name is used for finding and identifying computers on the

Internet. A domain name can be any combination of letters and numbers, and it can be used in

combination of the various domain name extensions, such as .com, .net and more.

No two websites can have the same domain name. A domain name is one that represents an IP

address of a computer on the network. It identifies the organization or group on the internet.

315


An example; www.bbc.co.uk

The domain is separated into four parts just like the IP address. A user normally finds it easier to

use a domain name instead of an IP address to access the internet, but the internet protocol only

understands IP addresses so the domain name must be translated(resolved) into an IP address by

the DNS server (domain name system)

Name resolution

Name resolution is a technique that allows names to

represent network addresses.

For example, the website “yahoo.com" can be accessed without knowing the actual IP address

that the device at Yahoo is configured to use. A name resolution service translates, or "maps", the

name “yahoo.com" into an IP address to reach the destination device

Domain name system (DNS)

Domain Name System (DNS) is a system on a computer that maps text names to IP addresses

automatically.

The Domain Name System (DNS) translates the easily memorized domain names (e.g.

www.google.com) to the numerical IP addresses needed for the purpose of locating computer

services and devices worldwide. The Domain Name System is an essential component of the

functionality of the Internet.

For example www.bbc.co.uk

Www; indicates the host server

,bbc; is the name of the organization (second level domain).

.Co; refers to as the top or high level domain name which indicates the type of the organization.

316

http://www.bbc.co.uk/


Domain name hierarchy on the domain name

The hierarchy of domains descends from the right to the left label in the domain. Each label

specifies a sub domain of the domain to the right.

Different levels of domain name;

Top level (highest level) domain name

Second level domain (SLD)

Third level domain

Top level (highest level) domain name

Top-level domain (TLD) is the last part of an Internet domain name, that is, the group of letters

that follow the final/last dot of a domain name.

Examples of top level domain

.org

.gov

.com

.net

Commonly used Top level domain names

.com indicates that the organization is a commercial one i.e. business

.gov indicates that it is for a government department

.ac is for an academic organization

.org is for a non commercial or non business organization

.sc is for a school organization

.net is for a company that provides internet services

Top level Domain of some countries

.uk which is the last part of the domain name indicates that the web site is based in the UK.

317


Each country has been assigned a two letter code Such as;

.au for Australia

.de for German(Deutschland)

.it for Italy

.es for Spain (espania)

.ug for Uganda

Second level domain (SLD)

The second-level domain is the label directly to the left of the top level domain.

Third level domain

This is the part of the domain name that is immediately to the left of the second level domain

For example, given the domain name www.bbc.co.uk

.uk: The top level domain name

.co: Second level domain

.bbc: Third level domain

Www: The host server

Uniform resource locator (URL)

Uniform Resource Locator is defined as the global address of documents and other resources on

the World Wide Web.

Uniform Resource Locator is use to visit WebPages and other resources on the web. The URL is

an address that sends users to a specific resource online, such as a webpage, video or other

document or resource. When you search Google, for example, the search results will display the

URL of the resources that match your search query. The title in search results is simply a

hyperlink to the URL of the resource.

Example: http://www.yahoo.com/household/stampcollecting/welcome.html

318

https://www.webopedia.com/TERM/W/World_Wide_Web.html

https://www.webopedia.com/TERM/R/resource.html

https://www.webopedia.com/TERM/D/document.html

https://www.webopedia.com/TERM/A/address.html

http://www.bbc.co.uk/


Parts of a Uniform resource locator (URL)

1. The protocol being used, which could be http or ftp

2. The domain name which is the location that contains the file of web page

3. The path to a web page which may contain a folder name and document file name both of

these separated by forward slashes

4. The query string, or parameters. These are optional but show information about the page/file

5. URLs don’t contain capital letters or spaces, but contains dots and forward slashes.

6. The Forward slashes specify the path to the location of the file needed.

Definition of a web browser (web Client)

This is the software program used to access and view web pages. A Web browser is

communication software designed to allow the user to access and view web pages (HTML

documents) on the Internet’s World Wide Web. The browser is designed to interpret hypertext

Markup (HTML) language.

HTML is a code in which web pages are written, therefore it requires a web browser which is

specialized software to able to retrieve and display text, and multi-media in HTML.

319


A browser is a software application for retrieving, presenting and traversing information

resources on the World Wide Web.

Types of web browsers

Opera

Google Chrome

Mozilla Firefox

Microsoft Internet Explorer

Safari

Netscape

Sea Monkey

Camino

iCab

Mozilla Suite

Sunrise

Functions of a web browser

To request for web pages from a web server when the user type in the uniform resource

locator.

The web browser accesses information from the web server using the HTTP protocol

over a network to communicate with the web server.

It displays web pages on the screen.

It is used for steaming video content over the internet.

Displays multimedia content.

The followings can be done using web browsers

View hundreds of millions of WebPages.

Use mail clients to Send and receive e-mail.

Download games, music and computer software.

Chat

Shop on line

See and hear recorded broadcasts

Participate in virtual conferences

A view channel, a channel is a website that automatically transmits information to your

computer at the time you specify.

320


Search engines

A search engine is software that allows one to search for web pages on the WWW by typing in a

search query relating to the topic that one is searching for.

It is a service that allows Internet users to search for content via the World Wide Web (WWW).

A user enters keywords or key phrases into a search engine and receives a list of Web content

results in the form of websites, images, videos or other online data.

It is a software program or script available through the Internet that searches documents and files

for keywords and returns the results of any files containing those keywords.

Different types of search engines

Features of a search engine

All pages are ranked by a computer algorithm not by subject category. They rank the most

relevant pages first or those that register most occurrences of the key word(s) usually more

accurate pages are listed before sites that include unreliable and erroneous material.

They are huge databases.

They are not evaluated-They contain the good and the bad so the user must evaluate

everything to determine its relevance.

321

https://www.computerhope.com/jargon/i/internet.htm

https://www.computerhope.com/jargon/s/script.htm

https://www.computerhope.com/jargon/p/program.htm

https://www.computerhope.com/jargon/s/software.htm


How search engines work

When the user type the key words in the search query in the search text box and presses ok button,

the search engine invokes a program that queries its database (a collection of all the web pages it

has access to). The results are returned to the user as a number of possible URL's ranked in

priority, the top URLs are the ones with most occurrences of the query words or phrases used.

Effective use of a search engine

Note that one can do a more complex search using more than one keyword and linking them

together with “AND” and “OR” or “NOT” (Boolean’s logic)

Be specific- e.g. if one wants to search about windows 98 bugs, the search query should be

“windows 98 bugs” not just “windows”

Using the symbols + or - the plus symbol lets you find pages that have all the words in the

query e.g. to get pages that refer to both john and Tom on the same page, use +john +Tom

Example 2 +computer +studies +schools gives pages on computer studies in schools

Use the – symbol to eliminate characters from the search.

Use parentheses to sequence operators and group words. Example; always group words

joined by OR with parentheses.

Narrow the search query to avoid irrelevant results.

Evaluation of search results

Not all that is published over the internet is good or accurate. So there is need to evaluate what

one finds. The following are the guidelines;

Accuracy

Is the information accurate?

Is it reliable and error-free?

Are the interpretations and implications reasonable?

Is there evidence to support conclusions?

Is the evidence verifiable?

Do the authors properly list their sources, references or citations with dates, page numbers

or web addresses, etc.?

322


Objectivity

What is the purpose of information?

What do the authors want to accomplish?

Does this purpose affect the presentation?

Is the information fact, opinion, spoof, or satirical?

Currency

Is the information current (up to date)?

Is it still valid?

When the site was last updated?

Is the site well-maintained?

Are there any broken links?

Coverage

Is the information relevant to your topic and assignment?

What is the intended audience?

Is the material presented at an appropriate level?

Is the information complete?

A website

A web site is a collection of web pages where information of a particular organization or

company is stored.

Basic types of websites

News websites

Informational websites

Online Business / marketing

websites

Wikis

Online social networks

Educational websites

E- Commerce website

Mobile device websites

Blogs

Personal websites

Photo sharing websites

323


News website

A news Web page contains news worthy material including stories, articles and videos relating

to current events, life, money, sports, weather etc.

Information website

Information website is a website that provides information such as census data, tax code, and

forms, government documents, public transportation schedules, and government budget and

research report.

E-commerce/ online business website

This is website that contains content that promotes selling and buying of goods, and services

online.

Educational website

An educational Web site offers exciting, challenging avenues for formal and information

teaching and learning. Some companies provide online training to employees and universities

offer online classes and degrees.

Entertainment website

An entertainment Web site offer music, videos, sports, games, ongoing Web episodes,

sweepstakes (Lottery), chats, and many other entertainment services.

Media sharing Web site

A media sharing Web site is a specific type of online social network that enables members to

share media such as photos, music, and videos.

Personal website

A personal Web page is maintained by a private individual who normally is not associated with

any organization. It is s type of website that allows an individual person to share with others

about his/her thoughts, photos, and experience including personal details.

Online Social Network website

An online social network also known as social networking Web site, is a Web site that

encourages members in its online community to share their interests, ideas, stories, photos,

music, and videos with other registered users. Examples include; Face book, twitter, what saps

etc.

324


Advantages of social networking website

Disadvantages of social networking website

They are addictive.

They are not regarded as formal

In case one forgets his/her password, signing in is not possible and this can lead to loss

of information.

Social Networks may violate privacy in case someone else gets to know your user

password.

Misinterpretation: One has to be careful while posting any kind of information on social

networks. If typed in a hurry, the matter could be misinterpreted.

Junk Messages: Social Networks are used a lot to send unsolicited messages and

unwanted advertisements.

Why people visit a web site

i. To find information they need

ii. To buy something online

iii. To get various multimedia elements for entrainment

iv. To be part of the community through social media

v. To complete a task

Characteristics of a good web site

A web site must be supported by a reputable institution without bias in the information

A website should be written at an appropriate level

It should list the author and the appropriate credentials

It should be well organized and the links should work well

The information on the web page should be current

The pages at the web site should download quickly and be visually pleasing and easy to

navigate

It should contain little advertising and be free of preconceptions

325


Functions of a web site

1. It acts as a source of information. It can be used in research to get information on the

internet about advertisements, entertainment, etc.

2. It helps users or a particular organization to share knowledge and information over the

internet

3. It provides motivations to the users of an organization

4. It encourages pride of ownership

5. It enhances communication and collaboration

6. It helps in storing important information for an organization.

7. It helps organizations in easy and quick advertisement of their products.

8. It enables organizations to upload and download information to and from the internet

respectively.

9. It helps organizations to easily maintain and update the information about them quickly

Importance of a web site to a school

1. It is used for communication purposes. The school can reach out to a wider audience

worldwide, for example, in school recruitment.

2. Used for mobilization of resources. The website can be used for resource mobilization as

it can reach out to a wide supporting audience.

3. For advertising purposes. The website can provide general information about the school.

4. The website can provide a forum for discussion of issues concerning the school using

blogs.

5. It can be used for teaching and learning in the following ways:

The website can provide subject content notes to students.

The website can present an opportunity for developing web designing technology

skills for students directly involved.

The school community can collaborate with other students worldwide for project

based learning.

6. The website can provide a forum for students and teachers to collaborate with others

elsewhere.

7. The site can provide a forum for parents and alumni feedback.

326


8. It can work as a depository (store) where student’s achievement data is posted for easy

access by the stakeholders.

9. It can help teachers to collaborate with other teachers worldwide.

10. The site can be used to publish students and teachers work.

Limitations of a web site to a school

1. Websites are expensive to be constructed. Therefore, some institutions may not be in

position to come up with one.

2. They require a lot of maintenance and update hence becoming expensive and time

consuming.

3. They limit customers from directly interfacing with the business men. This makes

customers to sometimes be cheated.

4. Very many people and organizations are creating websites with a lot of information

which is not legitimate and some organizations lay the public through the websites.

Guidelines for evaluating the value of a Web site

The institution hosting a website should support the web site without bias in the

information

The web site should be written at an appropriate level

The web site should list the author and the appropriate credentials

The web site should be well organized and the links should work properly

The information on the web page should be current

The pages at the web site should download quickly and easy to navigate

The web site must be objective

TOPIC 12: ELEMENTARY COMPUTER PROGRAMMING

A program is a set of step-by-step instructions that directs the computer to do the tasks you want

it to do and produce the results you want.

A computer requires programs to function. A computer program is usually written by a computer

programmer in a programming language.

327


A programming language is a set of rules that provides a way of telling a computer what

operations to perform.

A programmer, developer, dev, coder, or software engineer is a person who creates computer

software. The term computer programmer can refer to a specialist in one area of computers or to

a generalist who writes code for many kinds of software.

The roles of a programer

Converting problem solutions into instructions for the computer by preparing the

instructions of a computer program and runs those instructions on the computer, tests the

program to see if it is working properly, and makes corrections to the program.

The programmer also writes a report on the program. These activities are all done for the

purpose of helping a user fill a need, such as paying employees, billing customers, or

admitting students to college.

Computer programming is the process of writing instructions that get executed by computers.

The instructions, also known as code, are written in a programming language which

the computer can understand and use to perform a task or solve a problem.

There are at least three good reasons for learning programming:

Programming helps you understand computers. The computer is only a tool. If you learn

how to write simple programs, you will gain more knowledge about how a computer

works.

Writing a few simple programs increases your confidence level. Many people find great

personal satisfaction in creating a set of instructions that solve a problem.

Learning programming lets you find out quickly whether you like programming and

whether you have the analytical turn of mind programmers need.

Common terminologies used in computer programming

328


Source code

Source code is a program instruction written in a computer programming language to specify the

actions to be performed by a computer.

Pseudo code

Pseudo code is a computer programming language code that resemble plain English that cannot

be compiled but explain a resolution to a problem.

Object code

Object code is a program code that has already been translated into machine readable form

Syntax

Syntax is a set of rules or order to be followed when writing characters in a programming

Debugging

Debugging is a process that involves identifying a problem, isolating the source of the problem,

and correcting the problem by running the program

Algorithm

Algorithm is a list of procedure or instructions or formulas used to solve a problem.

A flow chart

A flowchart is a type of diagram that represents an algorithm, workflow or process.

The flowchart shows the steps as boxes of various kinds, and their order by connecting the boxes

with arrows. This diagrammatic representation illustrates a solution model to a given problem.

Basic Flow chart symbols

329


Features of programming language

Simplicity: A good programming language must be simple and easy to learn and use. It should

provide a programmer with a clear, simple and unified set of concepts, which can be easily

grasped. The overall simplicity of a programming language strongly affects the readability of the

programs written in that language, and programs, which are easier to read and understand, are

also easier to maintain. It is also easy to develop and implement a compiler or an interpreter for a

programming language, which is simple. However, the power needed for the language should not

be sacrificed for simplicity.

Naturalness: A good language should be natural for the application area, for which it has been

designed. That is, it should provide appropriate operators, data structures, control structures, and

a natural syntax to facilitate the users to code their problem easily and efficiently.

Abstraction: Abstraction means the ability to define and then use complicated structures or

operations in ways that allow many of the details to be ignored. The degree of abstraction

allowed by a programming language directly effects its writ ability. Object oriented language

support high degree of abstraction. Hence, writing programs in object oriented language is much

easier. Object oriented language also support re usability of program segments due to this

features.

330


Efficiency: Programs written in a good programming language are efficiently translated into

machine code, are efficiently executed, and acquire as little space in the memory as possible.

That is a good programming language is supported with a good language translator which gives

due consideration to space and time efficiency.

Structured:- Structured means that the language should have necessary features to allow its

users to write their programs based on the concepts of structured programming. This property of

a moreover, it forces a programmer to look at a problem in a logical way, so that fewer errors are

created while writing a program for the problem.

Compactness: In a good programming language, programmers should be able to express intended

operations concisely. A verbose language is generally not liked by programmers, because they

need to write too much.

Locality:-A good programming language should be such that while writing a programmer

concentrate almost solely on the part of the program around the statement currently being

worked with.

Features of a program

Portability: Portability refers to the ability of an application to run on different platforms

(operating systems) with or without minimal changes. Due to rapid development in the hardware

and the software, nowadays platform change is a common phenomenon. Hence, if a program is

developed for a particular platform, then the life span of the program is severely affected.

Readability: The program should be written in such a way that it makes other programmers or

users to follow the logic of the program without much effort. If a program is written structurally,

it helps the programmers to understand their own program in a better way. Even if some

computational efficiency needs to be sacrificed for better readability, it is advisable to use a more

user-friendly approach, unless the processing of an application is of utmost importance.

Efficiency: Every program requires certain processing time and memory to process the

instructions and data. As the processing power and memory are the most precious resources of a

331


computer, a program should be laid out in such a manner that it utilizes the least amount of

memory and processing time.

Structural: To develop a program, the task must be broken down into a number of subtasks.

These subtasks are developed independently, and each subtask is able to perform the assigned

job without the help of any other subtask. If a program is developed structurally, it becomes

more readable, and the testing and documentation process also gets easier.

Flexibility: A program should be flexible enough to handle most of the changes without having

to rewrite the entire program. Most of the programs are developed for a certain period and they

require modifications from time to time. For example, in case of payroll management, as the time

progresses, some employees may leave the company while some others may join. Hence, the

payroll application should be flexible enough to incorporate all the changes without having to

reconstruct the entire application.

Generality: Apart from flexibility, the program should also be general. Generality means that if

a program is developed for a particular task, then it should also be used for all similar tasks of the

same domain. For example, if a program is developed for a particular organization, then it should

suit all the other similar organizations.

Documentation: Documentation is one of the most important components of an application

development. Even if a program is developed following the best programming practices, it will

be rendered useless if the end user is not able to fully utilize the functionality of the application.

A well-documented application is also useful for other programmers because even in the absence

of the author, they can understand it.

Importance of programming

Programming helps the users to understand computers

Knowledge of using and programming computers is essential for scientists and engineers.

Writing simple programs increases the user’s confidential level

332


Limitations of programming

It is time consuming and tedious

The user has to master the codes of different languages

It is difficult to make correction when wrong codes are already compiled

The user has to study all the different languages

The Programming Process

Developing a program involves steps similar to any problem-solving task. There are five main

ingredients in the programming process:

1. Defining the problem

2. Planning the solution

3. Coding the program

4. Testing the program

5. Documenting the program

Defining the problem

Specifically, the task of defining the problem consists of identifying what it is you know (input-

given data), and what it is you want to obtain (output-the result). Eventually, you produce a

written agreement that, among other things, specifies the kind of input, processing, and output

required.

Planning the solution

Two common ways of planning the solution to a problem are to draw a flowchart and to write

pseudo code, or possibly both. Essentially, a flowchart is a pictorial representation of a step-by-

step solution to a problem. It consists of arrows representing the direction the program takes and

boxes and other symbols representing actions. It is a map of what your program is going to do

and how it is going to do it.

333


Pseudo code is an English-like nonstandard language that lets you state your solution with more

precision than you can in plain English but with less precision than is required when using a

formal programming language. Pseudo code permits you to focus on the program logic without

having to be concerned just yet about the precise syntax of a particular programming language.

However, pseudo code is not executable on the computer.

Coding the program

As the programmer, your next step is to code the program-that is, to express your solution in a

programming language. You will translate the logic from the flowchart or pseudo code-or some

other tool-to a programming language.

As we have already noted, a programming language is a set of rules that provides a way of

instructing the computer what operations to perform. There are many programming languages

such as BASIC, COBOL, Pascal, FORTRAN, and C. You may find yourself working with one

or more of these.

Although programming languages operate grammatically, somewhat like the English language,

they are much more precise. To get your program to work, you have to follow exactly the rules-

the syntax-of the language you are using. Of course, using the language correctly is no guarantee

that your program will work, any more than speaking grammatically correct English means you

know what you are talking about. The point is that correct use of the language is the required

first step. Then your coded program must be keyed, probably using a terminal or personal

computer, in a form the computer can understand.

One more note here: Programmers usually use a text editor, which is somewhat like a word

processing program, to create a file that contains the program. However, as a beginner, you will

probably want to write your program code on paper first.

Testing the Program

Some experts insist that a well-designed program can be written correctly the first time. In fact,

they assert that there are mathematical ways to prove that a program is correct. However, the

334


imperfections of the world are still with us, so most programmers get used to the idea that their

newly written programs probably have a few errors. This is a bit discouraging at first, since

programmers tend to be precise, careful, detail-oriented people who take pride in their work.

Still, there are many opportunities to introduce mistakes into programs, and you, just as those

who have gone before you, will probably find several of them.

Eventually, after coding the program, you must prepare to test it on the computer which involves

the following phases:

Desk-checking: This phase, similar to proofreading, is sometimes avoided by the programmer

who is looking for a shortcut and is eager to run the program on the computer once it is written.

However, with careful desk-checking you may discover several errors and possibly save yourself

time in the long run. In desk-checking you simply sit down and mentally trace, or check, the

logic of the program to attempt to ensure that it is error-free and workable.

Translating: A translator is a program that (1) checks the syntax of your program to make sure

the programming language was used correctly, giving you all the syntax-error messages, called

diagnostics, and (2) then translates your program into a form the computer can understand. A by-

product of the process is that the translator tells you if you have improperly used the

programming language in some way. These types of mistakes are called syntax errors. The

translator produces descriptive error messages. For instance, if in FORTRAN you mistakenly

write N=2 *(I+J))-which has two closing parentheses instead of one-you will get a message that

says, "UNMATCHED PARENTHESES." (Different translators may provide different wording

for error messages.) Programs are most commonly translated by a compiler.

A compiler translates your entire program at one time. The translation involves your original

program, called a source module, which is transformed by a compiler into an object module.

Prewritten programs from a system library may be added during the link/load phase, which

results in a load module. The load module can then be executed by the computer.

Debugging; A term used extensively in programming, debugging means detecting, locating, and

correcting bugs (mistakes), usually by running the program. These bugs are logic errors, such as

telling a computer to repeat an operation but not telling it how to stop repeating. In this phase

335

you run the program using test data that you devise. You must plan the test data carefully to

make sure you test every part of the program.

Documenting the Program

Documenting is an ongoing, necessary process, although, as many programmers are, you may be

eager to pursue more exciting computer-centered activities. Documentation is a written detailed

description of the programming cycle and specific facts about the program. Typical program

documentation materials include the origin and nature of the problem, a brief narrative

description of the program, logic tools such as flowcharts and pseudo code, data-record

descriptions, program listings, and testing results. Comments in the program itself are also

considered an essential part of documentation. Many programmers document as they code. In a

broader sense, program documentation can be part of the documentation for an entire system.

The wise programmer continues to document the program throughout its design, development,

and testing. Documentation is needed to supplement human memory and to help organize

program planning. Also, documentation is critical to communicate with others who have an

interest in the program, especially other programmers who may be part of a programming team.

And, since turnover is high in the computer industry, written documentation is needed so that

those who come after you can make any necessary modifications in the program or track down

any errors that you missed.

Developing a simple program

To develop and execute a program, the users need to understand three essential elements;

Editing: Where you will create the program source code

Compiling: Where your source code will be converted into a machine code

Executing (Running): Where your program will be run

Example

<html><head><title>Hello World!</title></head>

336

<body>

Hello World!

Huh, that's

<a href="http://www.yahoo.com/">Yahoo</a>

</body>

</html>

TOPIC 13: TRENDS IN COMPUTING

Computer integrity and security

Computer integrity refers to the faithfulness or loyality regarding the set laws to computer use

and its resources such as software and hardware devices.

The computer integrity falls into two categories that software integrity and hardware integrity.

In this era of technology, computer law is necessary to clarify actions that fall under the

computer law.

Computer intrusion (computer security threats)

Computer intrusion is a federal crime which needs to be governed by the laws. Such crèmes

include;

Access Device Fraud

Computer Fraud

Communication Interference

Wire and Electronic Communications Interception and Interception of Oral

Communications

Unlawful Access to Stored Communication

337


Recording of Dialing, Routing, Addressing and Signaling Information

Computer security threat is any event or action that could lead to damage to computer hardware

and software including the loss of data and information from an information system. These

illegal acts also refer to as computer crimes.

These computer security threats fall under three categories;

Hardware security threats

Software security threats

Network/Internet security threats

Network /Internet security threats

Internet and Network attacks are the criminal offenses done with use of the Internet and

computer networks in connection to hardware and software that are accessible to unauthenticated

users.

Information transmitted over networks has a higher degree of security risk than information kept

on a company‘s premises.

Even a computer not connected into network; an intruder can still have access to the hard drives

and destroy including the data saved on them. Therefore the security of computer hardware and

its components is necessary including protection of overall data.

Below are the most common and most damaging forms of security threats to network and

Internet users and site operators:

Malware

Unwanted programs,

Phishing and identity theft,

Hacking and cyber vandalism

Credit card fraud/theft,

Spoofing (pharming)

Denial of Service

Sniffing, insider attacks,

Poorly designed server and client software

338


Every unprotected computer is susceptible to the attack from malicious code.

Malware

Malware is software designed to infiltrate or damage a computer system without the owner's

informed consent. Malware is a general term used by computer professionals to mean a variety

of forms of hostile, intrusive, or annoying software/code.

Unwanted Programs:

These are programs on the internet that install themselves on a computer without the user‘s

consent such as adware, spyware, browser parasite.

Phishing and Identity Theft

Phishing is any deceptive (misleading/false), online attempt by a third party to obtain

confidential information for financial gain.

Hacking and Cyber vandalism:

A hacker is an individual who intends to gain unauthorized access to a computer system. Cyber

vandalism is the act of intentionally destroying computer equipment disrupting, defacing, or

even destroying the site.

Credit Card Fraud/Theft:

Theft of credit card data is one of the most feared occurrences on the Internet. Fear that credit

card information will be stolen frequently prevents users from making online purchases.

Spoofing (Pharming):

Spoofing is also called pharming. It involves redirecting a Web link to an address different from

the Intended one, with the site masquerading as the intended destination.

Denial of Service:

A denial of service attack is an assault whose purpose is to disrupt computer access to an

Internet service such as the Web or e-mail.

Sniffing:

A sniffing is a type of eavesdropping (spying) program that monitors information traveling

over a network.

339


Defense against internet and network attacks

Use a firewall

This is a software program that monitors all incoming and outgoing network traffic and allows

only the connections that are known and trusted.

Use antivirus software and keep it up-to-date

The program checks and cures both incoming and outgoing mail in real-time, is simple to install

and use. You only need to choose from three levels of protection.

Regularly check for spyware and adware

Spyware and Adware are files that can be installed on your computer without your permission.

These programs allow hackers to track your behavior on the Internet and retrieve your personal

information such as pin, credit card, phone and social security numbers, passwords, usernames,

etc.

Don’t open unknown email attachments

Don’t open any email attachments unless they are authored by a person or company that you

trust.

Disable hidden filename extensions

Windows operating systems contain an option to “Hide file extensions for known file types”

(enabled by default). Some email viruses take advantage of a hidden file extension. They use an

attachment which may appear to be harmless

Disable Java and ActiveX if possible

Java and ActiveX are used to write code that is executed by Web browsers. Although this code

generally adds useful features, it can be used by hackers, for example, to monitor your Internet

activity. You can disable Java and ActiveX in your browser at the cost of limited interaction with

some websites.

340


Turn off your computer or disconnect from the network when not in use

After the session, turn off your computer or otherwise completely disconnect it from the network

when you are not using it. This not only “protects” your computer from Internet security risks, it

forces your ISP to change your computer’s IP address more frequently, thus making it more

difficult for a hacker to get in.

Make regular backups of important data

A hard disk crash or physical theft of your computer results in the loss of all data stored on hard

disk. Keep a copy of important files on removable media such as floppy/ZIP disks or recordable

CD-ROM disks and store these disks somewhere away from the computer.

Route information through a proxy server

Proxy servers are software servers that handle all communications originating from or being sent

to the Internet, acting as a spokesperson or bodyguard for the organization.

Install intrusion detection software;

Intrusion detection software automatically analyzes vulnerabilities, identifies any unauthorized

intrusions, and notifies network administrators of suspicious behavior patterns or system

breaches.

Set of honey pots;

A honey pot is a vulnerable computer that is set up to entice an intruder to break into it.

Encryption all important files

Encryption involves converting data into a form that cannot be easily understood by others.

Use Biometric devices.

This is a form of identity access management and access control which uses measurable physical

and behavioral characteristics of individuals as a way of identifying them as the authentic users.

Examples of biometrics that might be used to authenticate a user include fingerprints, retinal

patterns, or speech/voice.

341


Avoid booting computers from infected floppies.

Avoid downloading programs from unknown/unlicensed sources.

Computer virus

A computer virus is a computer program that can copy itself and infect a computer without

permission or knowledge of the user. Viruses attach themselves to executable files that may be

part of legitimate programs. It is a computer code or program specially designed to damage or

cause irregular behavior in other programs in a computer.

Computer viruses are basically designed to carry out two tasks i.e.

To be able to replicate themselves from one computer to another

To be able to position themselves in a computer system and destroy software programs.

Types of computer virus

Computer viruses are categorized into two;

Non-resident viruses

Resident viruses

Non-resident viruses

Nonresident viruses are viruses that which search quickly for other hosts that can be infected.

Resident viruses

Resident viruses are types of viruses that do not search for hosts when they are started instead

they load themselves into memory during execution.

These types of viruses are permanent which dwells in the RAM memory. From there it can

overcome and interrupt all of the operations executed by the system: corrupting files and

programs that are opened, closed, copied, renamed etc.

Examples of resident viruses;

Multipartite Viruses

Direct Action Viruses

342


Boot Virus

Directory Virus

Macro Virus

Polymorphic Virus

File Infectors

Network Virus

Multipartite Viruses: Multipartite viruses are distributed through infected media and usually

hide in the memory. Gradually, the virus moves to the boot sector of the hard drive and infects

executable files on the hard drive and later across the computer system.

Direct Action Viruses: The main purpose of this virus is to replicate and take action when it is

executed. When a specific condition is met, the virus will go into action and infect files in the

directory or folder that it is in and in directories that are specified in the batch file.

Boot Virus: This type of virus affects the boot sector of a floppy or hard disk. This is a crucial

part of a disk, in which information on the disk itself is stored together with a program that

makes it possible to boot (start) the computer from the disk.

Macro Virus: Macro viruses infect files that are created using certain applications or programs

that contain macros.

Directory Virus: Directory viruses change the paths that indicate the location of a file. By

executing a program (file with the extension .EXE or .COM) which has been infected by a virus,

you are unknowingly running the virus program, while the original file and program have been

previously moved by the virus. Once infected it becomes impossible to locate the original files.

Polymorphic Virus: Polymorphic viruses encrypt or encode themselves in a different way

(using different algorithms and encryption keys) every time they infect a system.

File Infectors

This type of virus infects programs or executable files (files with an .EXE or .COM extension).

When one of these programs is run, directly or indirectly, the virus is activated, producing the

damaging effects it is programmed to carry out. The majority of existing viruses belongs to this

category, and can be classified depending on the actions that they carry out.

343


Network Virus: Network viruses rapidly spread through a Local Network Area (LAN), and

sometimes throughout the internet. Generally, network viruses multiply through

shared resources, i.e., shared drives and folders.

Sources of computer virus

1. Fake games

2. Through use of contaminated diskettes on several computers.

3. Through using pirated software.

4. Through using freeware and shareware from the internet.

5. Since these are free, they are good grounds for distributing viruses.

6. They also in most cases contain bugs which may turn into viruses unintentionally

7. Through software updates most especially over the internet or other networks.

8. Through sharing of data in a network.

How computer viruses spread

Booting a PC from an infected medium such as a floppy.

Executing an infected program.

Opening an infected file.

A virus can only spread from one computer to another when its host is taken to the

uninfected computer.

Viruses can spread to other computers over a network by infecting files on a network file

system or a file system that is accessed by other computers.

Viruses often travel via e-mail attachments. E-mail messages by themselves do not carry

viruses. Only .exe, .com or other types of executable files can carry a virus.

Diskette swapping: using other people’s diskettes for carrying data and programs to and from

affects the computer. Swapping means exchange of materials from one person to another.

Via networking connection: when people are trying to connect to the internet, they acquire

man made virus that affects their programs.

Via file down loading: downloading of files from the internet can spread viruses to your

computer.

Via computer laboratory where different users make unknown applications.

344


Via peripheral devices that uses parallel parts of connection.

Symptoms of computer virus

The computer runs slower than usual.

The computer stops responding, or it locks up frequently.

The computer restarts on its own.

Applications on the computer do not work correctly.

Disks or disk drives are inaccessible.

Strange error messages appears on the screen

An antivirus program cannot be installed on the computer, or the antivirus program will not

run.

New icons appear on the desktop that you did not put there, or the icons are not associated

with any recently installed programs.

Strange sounds or music plays from the speakers unexpectedly.

A program disappears from the computer even though you did not intentionally uninstall it

It shuts down unexpectedly or crashes frequently.

It experiences memory problems or runs out of disc space.

Unusual files or directories appear on your system.

Effects of computer virus

1. Some viruses are programmed to damage the computer by damaging programs, deleting files,

or reformatting the hard disk. Others simply replicate themselves and perhaps make their

presence known by presenting text, video, or audio messages.

2. They take up computer memory used by legitimate programs.

3. They can result in system crashes and data loss.

4. They can prevent a computer from booting.

5. The computer may freeze

6. Files on the computer become corrupted

7. Failure to do print jobs

8. Computers may fail to save or accessing a file to save

9. A computer gives un usual sound

345


10. It becomes very slow in operation

11. Files go on missing/ cannot be seen

12. Expected files increase in size

13. The computer take time to respond to instructions

14. There will be changes in operation of peripheral devices such as mouse and printers.

15. There will be permanent damages to data files and computer programs.

How to control computer virus

Do not use media like diskettes, backup tapes, CDs from unknown sources.

Scan all foreign media for viruses.

Install antivirus software;

Ensure that the anti – virus software is up to date;

Employ a firewall to protect networks;

Filter all email traffic

Educate all users to be careful of suspicious-mails;

Scan internet downloads;

Don’t run programs of unknown origin;

Make regular backups of critical data. A backup: is a duplicate of a file, program or

disk that can be used if the original is lost, damaged or destroyed.

Other forms of malicious attacks

Time bomb

It is a program code that is activated when it detects a certain condition or event. These events

can be famous days like Valentine, Fools – day.etc.

Droppers

These are programs that have been written to perform useful tasks like compressing

files, previewing video clips, etc. and in the process of performing those tasks; they

introduce viruses in the system.

Bugs:

346


A bug is unintentional fault in a program that is normally misinterpreted as a real virus. Moat

complex software in computer systems normally contains bugs. Minor bugs normally cause

simple inconveniences while major bugs can cause loss of data

Adware

It is a program that displays an online advertisement in a banner or pop-up window on

Web pages, email, or other Internet services.

Browser parasite

It is a program that can monitor and change the settings of a user‘s browser.

Spyware

It is a program placed on a computer without the user's knowledge that secretly collects

information about the user e.g. email address, instant messages, etc.

Worms

A worm is a computer program that sits in the computer‘s memory, rewrites

itself continuously into the memory until the system runs out of memory and

crushes. It differs from a virus in that the―reproduced segments keep

communicating with the mother code to function.

Trojan horse

It is a small program code hidden within legitimate software. Unlike a virus or a worm, a Trojan

horse doesn‘t have the ability to replicate itself but it is often a way for viruses or other malicious

code such as bots to be introduced into a computer system. They continue to operate as

legitimate software until at such a time that they are activated to cause trouble

Bots

Are a type of malicious code that can be covertly (secretly) installed on your computer when

attached to the Internet.

Once installed, the bot responds to external commands sent by the attacker, and your computer

becomes a―zombie, and is able to be controlled by an external third party

Meaning of Hacking

347


Hacking refers to unauthorized intrusion into a computer or a network. The person engaged in

hacking activities is known as a hacker. Hacker may alter system or security features to

accomplish a goal that differs from the original purpose of the system.

Hackers employ a variety of techniques for hacking, including:

Vulnerability scanner: That is checking computers on networks for known weaknesses

Password cracking: the process of recovering passwords from data stored or transmitted by

computer systems by guessing for the password repeatedly.

Packet sniffer: applications that capture data packets in order to view data and passwords in

transit over networks

Spoofing attack: involves websites which falsify data by mimicking legitimate sites, and they

are therefore treated as trusted sites by users or other programs

Root kit: represents a set of programs which work to subvert control of an operating system

from legitimate operators

Trojan horse: serves as a back door in a computer system to allow an intruder to gain access to

the system later

Viruses: self-replicating programs that spread by inserting copies of themselves into other

executable code files or documents

Denial of service: This is an attempt to make a computer or network resources unavailable to its

intended user.

Key loggers: tools designed to record every keystroke on the affected machine for later retrieval

Meaning of denial of service

Denial-of-service attack is a cyber-attack in which the perpetrator seeks to make a machine or

network resource unavailable to its intended users by temporarily or indefinitely disrupting

services of a host connected to the Internet. Hackers use DoS attacks to prevent legitimate uses

of computer network resources.

348

https://www.webopedia.com/TERM/C/computer.html

https://www.webopedia.com/TERM/H/hacker.html


Denial of service attacks are characterized by;

Attempt to flood a network, attempt to disrupt connections between two computers, attempts to

prevent an individual from accessing a service or attempts to disrupt service to a specific system

or person. Those on the receiving end of a denial of service attack may lose valuable resources,

such as their e-mail services, Internet access or their Web server.

Common Denial of Service Attacks

Buffer Overflow

The condition in which data transferred to a buffer exceeds the storage capacity of the buffer and some of

the data overflows into another buffer, one that the data was not intended to go into hence corrupting data

that is already contained in that buffer

Ping of Death

A type of denial of service attack in which the attacker sends a ping request that is larger than

65,536 bytes, which cause a buffer overload on the operating at the receiving end hence crashing the

system.

Smurf Attack

A type of network security breach in which a network connected to the Internet is swamped with replies

to ping requests. A smurf attacker sends PING requests to an Internet broadcast address. These are special

addresses that broadcast all received messages to the hosts connected to the subnet. When a single

attacker sends hundreds or thousands of ping messages the ping replies bring the entire internet service

down.

TCP SYN Attack

In a SYN attack, a sender transmits a volume of connections that cannot be completed. This causes the

connection queues to fill up, thereby denying service to legitimate TCP users.

Teardrop

349

https://www.webopedia.com/TERM/T/TCP.html

https://www.webopedia.com/TERM/V/volume.html

https://www.webopedia.com/TERM/T/TCP_SYN_attack.html

https://www.webopedia.com/TERM/H/host.html

https://www.webopedia.com/TERM/B/broadcast.html


https://www.webopedia.com/TERM/N/network.html

https://www.webopedia.com/TERM/S/security.html

https://www.webopedia.com/TERM/B/buffer_overflow.html

https://www.webopedia.com/TERM/B/byte.html

https://www.webopedia.com/TERM/P/PING.html

https://www.webopedia.com/TERM/D/DoS_attack.html

https://www.webopedia.com/TERM/B/buffer.html

https://www.webopedia.com/TERM/W/Web_server.html


https://www.webopedia.com/TERM/E/e_mail.html

https://www.webopedia.com/TERM/F/Flooding.html


A Teardrop is a type of denial of service attack where fragmented packets are forged to overlap each

other when the receiving host tries to reassemble them.

Denial of service attack control

Installing and maintaining anti-virus software

Installing a firewall, and configuration to restrict traffic coming into and leaving your

computer

Follow good security practices for distributing your email address.

Backdoor

A backdoor also known as manhole or trapdoor is a term used to describe a hidden method of

bypassing security to gain access to a restricted part of a computer system. For example, a

programmer may insert a piece of code that would allow them access to a computer or secure

area using a password that only they know.

Spoofing attack (Phishing)

Spoofing is a technique used to gain unauthorized access to computers, whereby the intruder sends

messages to a computer with an IP address indicating that the message is coming from a trusted host. To

engage in IP spoofing, a hacker first use a variety of techniques to find an IP address of a trusted host and

then modify the packet headers so that it appears that the packets are coming from that host.

Spoofing attack is a situation in which one person or program successfully masquerades as

another by falsifying data, thereby gaining an illegitimate advantage.

Forms of spoofing

Caller ID spoofing: This is where callers lie about their identity by presenting false names and

numbers as a tool to defraud other people.

E-mail address spoofing: This is where the email sender altered the information in emails by

hiding the origin of the email

Voice mail spoofing: This is a situation where somebody pretend as if is calling from your cell

phone when it is actually not.

350

https://www.webopedia.com/TERM/P/packet.html

https://www.webopedia.com/TERM/I/IP_address.html

https://www.webopedia.com/TERM/P/packet.html

https://www.webopedia.com/TERM/T/Teardrop_attack.html


Global Positioning System (GPS) spoofing: This is a situation where by the GPS sender

deceives a GPS receiver by broadcasting incorrect GPS signals, structured to resemble a set of

normal GPS signals, or by rebroadcasting genuine signals captured elsewhere or at a different

time.

Computer crime

Computer crimes are criminal activities which involve the use of information technology to gain

an illegal or unauthorized access to a computer system with the intent of damaging, deleting, or

altering computer data. They also include activities such as electronic frauds, misuse of devices,

identity theft, and data as well as system interference.

Computer crimes may not necessarily involve damage to physical property. They rather include

the manipulation of confidential data and critical information. They involve activities like

software theft, wherein the privacy of users is hampered.

There are four basic categories are utilized in describing computer crime. These are: theft,

fraud, copyright infringement and attacks.

Different forms (types) of computer crimes

Child pornography - Making or distributing child pornography.

Cracking - Breaking or deciphering codes that are being used to protect data.

Cyber terrorism - Hacking, threats, and blackmailing towards a business or person.

Cyber bully or Cyber stalking - Harassing others online.

Creating Malware - Writing, creating, or distributing malware (e.g., viruses and spyware.)

Denial of Service attack - Overloading a system with so many requests it cannot serve normal

requests.

Espionage - Spying on a person or business.

Fraud - Manipulating data, e.g., changing banking records to transfer money to an account.

Harvesting - Collect account or other account related information on other people.

351

https://www.computerhope.com/jargon/h/harvest.htm

https://www.computerhope.com/jargon/c/computer-fraud.htm

https://www.computerhope.com/jargon/d/dos.htm

https://www.computerhope.com/jargon/v/virus.htm

https://www.computerhope.com/jargon/m/malware.htm

https://www.computerhope.com/jargon/c/cyberbul.htm

https://www.computerhope.com/jargon/c/cracker.htm


Identity theft - Pretending to be someone you are not.

Intellectual property theft - Stealing practical or conceptual information developed by another

person or company.

Phishing - Deceiving individuals to gain private or personal information about that person.

Salami slicing - Stealing tiny amounts of money from each transaction.

Scam - Tricking a person into believing something that is not true.

Spamming - Distributed unsolicited e-mail to dozens or hundreds of different addresses.

Spoofing - Deceiving a system into thinking you are someone you really are not.

Unauthorized access - Gaining access to systems you have no permission to access.

Wiretapping - Connecting a device to a phone line to listen to conversations.

Sniffing: The act of intercepting internet protocol packets while getting transferred on a network

Eavesdropping: The act of secretly listening to the private conversation of others without their

consent

Smishing: The act of using cell phone text message to lure people to provide personal

information such financial ID, driving license number etc.

Safeguarding against computer crimes

Use of log files

Data encryption

Use of firewall

Use of updated antivirus software

Use of Biometric devices

Use of password

Putting up physical security mechanism such as CCTV cameras and sensors

Employing system administrators to centrally manage system resources

352

https://www.computerhope.com/jargon/u/unauacce.htm

https://www.computerhope.com/jargon/s/spoof.htm

https://www.computerhope.com/jargon/s/spam.htm

https://www.computerhope.com/jargon/s/scam.htm

https://www.computerhope.com/jargon/s/salami-slicing.htm

https://www.computerhope.com/jargon/p/phishing.htm

https://www.computerhope.com/jargon/i/identhef.htm


Computer protection (Computer security system)

Computer system security is the ability of a computer system to protect information and system

resources with regards to confidentiality and integrity. It refers to all processes and mechanisms

by which computer based equipment, information and services are protected from unauthorized

access or destruction including unplanned events and disasters.

Forms of computer security system

There are two forms or categories of computer security systems;

Physical security

Data security

Physical security is the protection of personal programs, networks and data from physical

circumstances and events that could lead to damage. The protection includes protection from

fire, natural disasters, buglers, theft, vandalism and terrorism.

In order to protect the physical equipments, the following physical security access control

measures must be put in place;

Use physical access controls such as locked doors and windows.

Use cables to lock the equipment to desk, cabinet or floor.

Install alarm systems to warn you in case of any intrusion

Use passwords, and biometric devices.

Install surveillance cameras to help you in easy monitoring of the hardware

Putting up strong burglar poof doors and windows to avoid thieves

Ensure that fire extinguisher is fixed in the computer lab in case of any emergency fire

outbreak

Consider installing a security alarm at a strategic point in case of a breakage.

Do not welcome strangers into the computer room.

Employing security guards to the entrance of the facilities

A possessed object is any item that one must carry to gain access to a computer or

computer facility such as card key to secure physical area

353


Data security refers to the methods of protecting a database from destructive forces and

unwanted actions of unauthorized users. For data protection to be ensured the user must employ

both hardware and software based security mechanisms such as;

Keep a copy of your data off site in case of any firebreak.

Make regular backups of critical data. A backup: is a duplicate of a file, program or disk

that can be used if the original is lost, damaged or destroyed

Protect data files by using password mechanism

Install intrusion detection software to provide extra protection against hackers and other

intruders.

Use data masking. Data masking is the process of obscuring a specific data within a

database table to ensure that data is maintain and sensitive information is not exposed to

unauthorized user.

Install reliable antivirus programs on your computer system and update it regularly.

You can use steganography program to hide data inside another data.

Use encryption mechanism. Encryption is the process of transforming plain text or data

into cipher (unreadable) text that cannot be read by anyone other than the sender and the

receiver. It is a process of covering readable data into unreadable characters to prevent

unauthorized access.

Install a firewall-The key defense against Internet attackers is an Internet firewall.

Avoid e-mail Attachments from Unknown Sources.

Avoid booting computers from infected floppies.

Avoid downloading programs from unknown/unlicensed sources.

Computer ethics

Ethics is a set of moral principles that govern the behavior of a group or individual. Therefore, computer

ethics is set of moral principles that regulate the use of computers. Some common issues of computer

ethics include intellectual property rights (such as copyrighted electronic content), privacy concerns, and

how computers affect society.

354


As technology advances, computers continue to have a greater impact on society. Therefore, computer

ethics promotes the discussion of how much influence computers should have in areas such as artificial

intelligence and human communication. As the world of computers evolves, computer ethics continues to

create ethical standards that address new issues raised by new technologies.

Ethical issues arising from the development and wide-spread use of ICT are of increasing concern.

Prominent examples include the limitations of privacy in social network sites, ownership and control of

data by search providers, the limitations on the use of large-scale public databases or ICT systems or the

possibility of moral agency by autonomous systems.

Common ethical issues in ICT

The most common ethical issues that need to be address in the ICT industry include;

Label issue: Libel is the publication of a false statement that injuries one’s business or personal

reputation.

Plagiarism: Plagiarism means using someone intellectual property such as ideas and written

works and claim that ideas is yours

Software piracy: Software piracy refers to the act of installing a copy of software into your

computer without authorization.

Misuse: Misuse is the use of the harmful acts such as hacking, spamming, cracking etc.

Copyright infringement: copyright infringement refers to the act of copying intellectual

property without the written permission from the copyright owner.

The rights owned by the owner of the copyright are:

The right to modify the work to create a new work

The right to distribute the work to the public by sale

The right to display a copy of the work directly to the public by posting it on the internet,

hanging it on public places, putting it on films or movies

Computer ethics and integrity

Computer ethics are moral guidelines or codes of conduct that govern the use of

computer and information systems.

On the other side computer integrity refers to the loyalty or faithfulness regarding

the set laws to computer use.

355


Codes of conduct

Codes of conduct are written guidelines that help to determine whether a specific action is ethical

or unethical.

Computer ethical codes of conduct

Computers should not be use to Harm Other People.

Computers should not be use to Interfere with Other People's Computer Work.

Users should not snoop around in Other People's Computer Files.

Computers should not be use for stealing.

Computers should not be use to Bear False Witness.

Users should not copy or use Proprietary software for which you have not paid.

Thou Shall Not Use Other People's Computer Resources without Authorization or Proper

Compensation.

Thou Shall Not Other People's Intellectual Output.

Computer users should think about the social consequences of the program one is

designing.

Users should always use computers in consideration and respect for others.

Unethical computer codes of conduct

Modifying people’s information on the internet without authorization

Selling someone information to other parties without the owner’s permission

Using someone information or resources without authorization

Stealing of computer software

Sending or posting flames which are so abusive or insulting messages

Invasion of privacy

Using capital letters which is equivalent to shouting

Computer privacy

Privacy is the moral right of individuals to be left alone, free from surveillance or

interference from other individuals or organizations, including the state.

Information Privacy refers to the right individuals, companies or organizations have

356


to deny or restrict the collection and use of information about them.

Different aspects of information privacy and violation

The use of Global Positioning system (GPS) and (RFID) technologies has led to the

violation of information privacy for example GPS which is use to tack the movement of

people by mobile signals, and the use of Radio frequency identification (RFID) enable

companies to track their customer’s purchases and profile their behaviors.

Online services such as flight tickets, hotel bookings, and internet banking has made

people to provide some important private information to other organizations.

Online social services such as email, what sap, twitter, face book etc are essential

communication tools these days but they are not secure ways to protect privacy.

Individual’s personal data these days can be traced and gained through databases,

spyware and cookies which give providers wider chances to access personal information.

A cookie is a small text file that a Web server stores on your computer that allows a

site to track the actions of its visitors. E-commerce, Webcasting, and other Web

applications often rely on cookies to identify users and track information about

viewers, customers, and subscribers.

A cookie resides on an individual’s hard drive, but does not interact with other

information store on the system.

Intellectual property rights

Intellectual property is a category of property that includes intangible creations of the human intellect,

and primarily encompasses copyrights, patents, and trademarks. It also includes other types of rights, such

as trade secrets, publicity rights, moral rights, and rights against unfair competition.

A right that is had by a person or by a company to have exclusive rights to use its own plans, ideas, or

other intangible assets without the worry of competition, at least for a specific period of time.

Intellectual property is divided into two categories:

Industrial Property includes; patents for inventions, trademarks, industrial designs and

geographical indications.

Copyright covers literary works (such as novels, poems and plays), films, music, artistic

works (e.g., drawings, paintings, photographs and sculptures) and architectural design.

357

https://en.wikipedia.org/wiki/Trade_secret


Types of intellectual property

Copyright

Copyright is a legal term used to describe the rights that creators have over their literary and

artistic works. Works covered by copyright range from books, music, paintings, sculpture and

films, to computer programs, databases, advertisements, maps and technical drawings.

Patents

A patent is an exclusive right granted for an invention. Generally speaking, a patent provides the

patent owner with the right to decide how - or whether - the invention can be used by others. In

exchange for this right, the patent owner makes technical information about the invention

publicly available in the published patent document.

Trademarks

A trademark is a sign capable of distinguishing the goods or services of one enterprise from

those of other enterprises. Trademarks date back to ancient times when artisans used to put their

signature or "mark" on their products.

Copy right law in Uganda

Copyright law in Uganda is currently is governed by; the Cop yright and Neighbouring Act, 2006

and the Copyright a nd Neighbouring Rights Regulations, 2010 .

The Act provides that NO person of any kind shall produce, reproduce, distribute, broadcast,

make available to the public, sale or offer for sale, lease or rent out or make public performances

or import for distribution …audio visual recordings in Uganda except under a licence issued by

the owner of the neighbouring rights or a Collecting society.

Computers and society

Impacts of computer technology in society

Computer technology has open opportunity for new job creation such as software

developers, system administrators, computer operators, database administrators etc.

With many improvements in computer technology, it has contributed to job replacement

for instance many computer illiterates have been replaced by skilled computer personnel.

358

http://ufmi.blogspot.com/p/home.html

http://www.nabotu.or.ug/userfiles/file/Copyright%20reg%202010.pdf

http://www.nabotu.or.ug/userfiles/file/Copyright%20reg%202010.pdf

http://www.wipo.int/clea/docs_new/pdf/en/ug/ug001en.pdf

http://www.wipo.int/clea/docs_new/pdf/en/ug/ug001en.pdf

http://www.wipo.int/trademarks/en/

http://www.wipo.int/patents/en/

http://www.wipo.int/copyright/en/


Besides that, the introduction of computer technology has led to job replacement for

example many security personnel have been replaced by the use of CCTV, and sensors

technologies

Computer technology in automation has greatly improved on the quality and quantity of

products being produced.

Introduction of computer technology has also greatly affected the nature of people work

for example secretarial work was done by the use of typewriter has been replaced with

the use of application software programs and the use of non impact printers.

The introduction of computer technology has open more avenues for computer crimes

such as electronic fraud, misuse of devices, identity theft etc.

The introduction of digital forensic is helping in recovery and investigation of material

found in digital devices related to computer crime.

The introduction of computer technology has open more avenues for computer crimes

such as electronic fraud, misuse of devices, identity theft etc.

The introduction of digital forensic is helping in recovery and investigation of material

found in digital devices related to computer crime.

On environment, the computer technology has enabled national meteorological centers

and the ministry of environment to improve disaster warnings and relief.

Computer technology has led to the improvement in agricultural and forestry sectors by

carrying out research towards better farming methods and mechanization.

The use of computer technology has brought about some negative impacts to the

environment such as:

Pollutant manufacturer of hardware equipments

Improper disposal of e-waste

The use of high energy consumption devices leading to global warming

Deforestation resulting from planting ICT masts, satellites, and setting up

of ICT related companies and factories

The use of various computer technologies have greatly contributed to many health related

problems such as:

Headache as a result of excessive use of computers

Neck pain as a result of improper sitting posture

359

https://en.wikipedia.org/wiki/Computer_crime

https://en.wikipedia.org/wiki/Computer_crime


Infections a s a result of germs from dirty keyboard, mouse, and the working area.

Repetitive stress injury resulting from wrist, hand, arm muscle strain and neck

Eye strain resulting from flickering and too much brightness of the monitor

Backache resulting from improper sitting and bad chair design.

Emerging technologies

Emerging technologies are technologies that are perceived as capable of changing the status

quo. These technologies are generally new but include older technologies that are still

controversial. Prediction suggests that with the rapid advancement in information and

communication technology more new technologies and computer related hardware devices,

software and applications are emerging up which will bring a lot of impacts in all aspects of life.

Lists of Emerging technologies

Artificial intelligence

Artificial Intelligence is a group of related technologies that attempt to develop machines to

emulate human like qualities such as learning, reasoning, communicating, seeing and hearing.

Three Dimensional (3D) optical storage media

This is a form of optical data storage in which data and information can be written, read and

recorded with three dimensional resolutions opposed by two dimensional resolution media such

as CD and DVD.

Fourth generation (4G0 cellular communication

4G cellular communication is a system that provides mobile ultra-broad band internet access to

laptops, USB wireless modems, smart phones, and to other mobile devices. It is a successor of

3G cellular communication.

Radio Frequency identification

Radio Frequency identification is the use of a wireless non-contact system that uses radio

frequency electromagnetic fields to transfer from a tag attached to an object for the purpose of

360


automatic identification and tracking.

Three Dimensional (3D) printing

3D printing is a combined system with Internet technology allow for digital blueprints of

virtually material products to be sent instantly to another person to be produced on the spot,

making purchasing a product online immediately.

Distributed ledger technology

Distributed ledger is a technology which provides transparent and immutable lists autonomous

transactions through the use of smart contracts. A smart contract is a vending machine that holds

goods until money has been received and then the goods are released to the buyer. The machine

holds the property and is able to enforce the contract. There were two main issues that needed to

be addressed before smart contracts could be used in the real world. The first one is the control

of physical assets by smart contract to be able to enforce agreements. Secondly, the last of

trustworthy computers that is reliable and trusted to execute the contract between two or more

parties.

Application areas of Emerging technologies

The use of mobile phones allows transfer or transaction of money from any bank or credit

line and vice versa.

The application of Radio Frequency identification in the area of identification and

tracking of assets use by many legal firms

One of the most common applications of car phones is in charging iphones and other

tablets freeing many people from the worry of charging their devices.

The application of digital forensics in criminal investigation before a criminal is

presented before the court of law.

The application of smart contract machine for holding goods until money has been

received and then the goods are released to the buyer by business companies.

Advantages of Emerging technologies

Easy Access to Information

361

https://en.wikipedia.org/wiki/Smart_contract


It has become pretty easy to get access to relevant information at anytime and anywhere. This

has been possible because of modern technologies like broadband internet.

Lots of data is being published and indexed online, sites like Wikipedia and YouTube have great

original content that is regularly used for research or entertainment.

With smart gadgets like the iPad, iPhone, Galaxy tablets, etc., users can easily have access to a

vast amount of information wherever they are through the use of the internet on these devices.

These smart gadgets make it easy to access the internet anywhere, and this simplifies the way we

get information.

Encourages Innovation and Creativity

Since technology seems infinite, it sparks the brain to work to its full potential. In the past, it

used to be very difficult to start a business, one had to have lots of capital, and they even had

limited access to business information.

Today, it is simple to start a business while at home. On this platform, creative developers post

projects to seek funding from the community; this helps them generate capital for their ideas

which later leads to the creation of new jobs and further innovation of technology. The other

creative works which have been facilitated by modern technology include Google, Apple, Face

book, Microsoft, Amazon, etc

Improved Communication

Communication is like water to life; it is essential to growth, we cannot progress without

communication. Modern technology has blessed us with advanced communication technology

tools. These include e-fax, electronic mail, mobile phones, video conferencing, instant text

messaging applications, social networking, etc.. All these modern communication technology

tools have simplified the way humans and businesses communicate.

The Convenience of Traveling/ Ease of Mobility

Modern transportation technology makes it very easy to travel long distances. Transport is a very

important both in our lives and in the business world. Transportation technology has evolved

362

https://www.useoftechnology.com/virtual-meeting-technologies/

https://www.useoftechnology.com/communication-technologies/

https://www.useoftechnology.com/technology-workplace-2/


with years. In the past, it used to be slow and expensive to move long distances. Nowadays, we

can cover a 10 miles distance within a few minutes using electric trains, airplanes or cars.

Improved Housing and Lifestyle

This is another excellent way how modern technology has simplified our lives. If you compare

the type of housing we used in 1900 and the architecture of houses today, the difference is

enormous. New architectural technology has improved the kinds of home we build. People with

money can afford floating homes, and glass homes or people with smaller means can make tiny

houses or mobile homes. Most of the items in our houses are now automated, for example, doors

use fingerprints, key cards, or Bluetooth on our mobile. Security has also increased at home with

the evolution of more robust integrated security system.

Improved Entertainment

Modern technology has played a significant role in changing the entertainment industry. Home

entertainment has improved with the invention of video games, advance music systems and

visual systems like smart televisions, which can connect live to the internet so that a user can

share what they’re watching with friends. Easy access and storage of music are ever present,

services like iTunes allow users to purchase and download music on their players at a small cost,

and this is a win-win situation for both musicians and the users. Additionally, bars, clubs, and

amusement parks have all benefited from advancements in technology. We can see things in 3D,

ride the highest roller coaster or be served by a robot at the bar, all possible through modern

technology.

Efficiency and Productivity

Modern technology has helped businesses increase production. Humans are slow, and sometimes

they fail to deliver on time and quality. Many companies have integrated modern technology in

their production line, increasing output and allowing for more consistent quality.

Convenience in Education

Learning is a process, and it is part of our daily lives. Modern technology has made it simple for

students to learn from anywhere through online education and mobile education. Also, students

363

https://www.useoftechnology.com/technology-for-education/


now use modern technology in classrooms to learn more effectively. For example, students use

tablets to share visual lessons and examples with peers in the classroom; this has made learning

more convenient and fun. Also, new modern educational technologies support individual

learning which gives students a chance to learn on their own with no need for tutors.

Social Networking

Modern technology has made it simple to discover our old friends and also discover new people

to network with; this is a benefit to both individuals and businesses. Many businesses have

embraced social networking technology to interact with their customers. Users of social

networks can share information with friends, live chat with them and interact in all sorts of ways.

Benefits to the Health Industry

Today most hospitals have implemented modern technology in surgical rooms, and this has

reduced mistakes made by doctors. Humans can easily make mistakes because of work overload

and stress factors. Additionally, the development community has developed health apps that

enable us to monitor our health, weight or fitness. These applications are used on mobile phones,

so users have access anytime.

Disadvantages of Emerging technologies

Increased Loneliness

Social Isolation is on the increase, people are spending more time playing video games, learning

how to use new modern technologies, using social networks and they neglect their real life.

Technology has replaced our old way of interacting. If a user can easily interact with 100 friends

online, they will feel no need to go out to make new friends which at a later stage can lead to

loneliness.

Job Loss

Modern technology has replaced many human jobs; robots are doing the jobs which used to be

done by humans. Many packing firms have employed robots on production lines to increase

364

https://www.useoftechnology.com/effects-technology-children/


production and efficiency, this is good news for businesses because it helps them make more

money and serve customers, but it is bad news for employees because they may become

redundant.

Excessive dependency:

Increased dependencies on modern tools and applications like calculators and spelling checkers

have reduced creativity. This affected the way we use our brains. Also depending on machines

and modern transportation put people at a distinct disadvantage, because they became less self –

reliant.

Security

Thankfully advances in technology have aided security, however, due to these advances;

everything is connected to the internet in some way. Our financial accounts, our photos, our cars,

mobile phone, everything touches the internet at some time. Due to the network of worldwide

devices and systems, many have fallen prey to an identity thief, hacked accounts by some

mischievous hacker. The road to recovery from these types of attacks can be extremely long and

painstaking.

World Destruction/Advanced Weapons

Modern technology has been the main aid in the increasing of endless wars. It aids the

manufacturing of modern war weapons. So when these weapons get into the hands of criminals,

they will use them for their selfish reasons. To add, these weapons often severely damage the

natural earth, making some areas uninhabitable.

High Maintenance costs

It is expensive to buy technology, but it is also costly to maintain it. Many small businesses can

not afford the cost of hiring a full-time technical person, so they resort to monthly tech

contractors who charge them for work done. If business technology tools like computers are not

well maintained, their performance will decrease and the process of buying new computers or

any other business technology can even be more expensive.

System Analysis

365

https://www.useoftechnology.com/4-security-tips-protecting-your-ecommerce-page/


Systems analysis is a problem-solving method that involves looking at the wider system,

breaking apart the parts, and figuring out how it works in order to achieve a particular goal.

A system is a set of components that interact to accomplish some purpose. For example, a computer

system contains processors, memory, electrical pathways, a power supply. others include College

system, Economic system, Language system, a Business and its parts - Marketing, Sales, Research,

Shipping, Accounting, Government.

The first step in solving a problem that involves a system is analyzing that system. This involves

breaking it down into the parts that make it up, and seeing how those parts work together.

Sometimes figuring out how a system works can involve turning off parts of the system and

seeing what happens, or changing parts of the system and seeing what the result is. If you change

what goes into a system, how does it change what comes out? Basically, systems analysis

involves techniques that allow you to understand how a system works.

Definition of terminologies

System: A system is a set of components that interact to accomplish some purpose.

Information System is interrelated components working together to collect, process, store, and

disseminate information to support decision making, coordination control analysis and

visualization in an organization.

Information: Data that have been transformed into meaningful and useful form to human

beings.

Data: Streams of raw facts representing events occurring in organizations.

366

InputProcessing

Classify

Arrange

OutputORGANIZATION

FEEDBACK

INFORMATION SYSTEM


Input: The capture or collection of raw data from within the organization or from its external

environment.

Processing: The conversion, manipulation, and analysis of raw input into a form that is more

meaningful to humans.

Output: The distribution of processed information to the people or activities where it will be

used.

Feedback: Output that is returned to the appropriate members of the organization to help them

evaluate or correct the input.

Computer-Based I.S. (CBIS): I.S. that rely on computer hardware and software for processing

and disseminating information.

System Analysis - Process of gathering and interpreting facts, diagnosing problems, and using the

facts to improve the system.

System analyst is an information specialist who performs systems analysis, design, and

implementation.

Systems Design - Process of planning a new system to replace or complement the old. Analysis

specifies what the system should do and design states how to achieve the objective.

Systems development Life Cycle (SDLC) is a series of stages applied to information system

development projects ensuring that all functional and user requirements, strategic goals and

objectives are met

Importance of system analysis

It helps in evaluating system request

It provides various experienced and knowledge at the time of evaluating system request

one person view point cannot affect the committee decisions

Phases of system analysis

367


These are series of stages applied to information system development projects ensuring that all

functional and user requirements, strategic goals and objectives are met. Theses phases are called

systems development Life Cycle (SDLC) which include;

Preliminary investigation

System analysis

System design

System coding

System Testing

System implementation

System maintenance

The different phases of system development life cycle are shown in Fig. 1.2 below.

System Study

Maintenance

Feasibility Study

Software

Implementatio

n DevelopmentSystem

Analysis

Life Cycle

Testing

System Design

Coding

368


Preliminary System Study

Preliminary system study is the first stage of system development life cycle. This is a brief

investigation of the system under consideration and gives a clear picture of what actually the

physical system is? In practice, the initial system study involves the preparation of a ‘System

Proposal’ which lists the Problem Definition, Objectives of the Study, Terms of reference for

Study, Constraints, and Expected benefits of the new system, etc. in the light of the user

requirements.

The system proposal is prepared by the System Analyst (who studies the system) and places it

before the user management. The management may accept the proposal and the cycle proceeds

to the next stage. The management may also reject the proposal or request some modifications in

the proposal. In summary, we would say that system study phase passes through the following

steps:

Problem identification and project initiation

Background analysis

Inference or findings (system proposal)

Feasibility Study

System Analysis

Systems analysis is a process of collecting factual data, understand the processes involved,

identifying problems and recommending feasible suggestions for improving the system

functioning.

This involves studying the business processes, gathering operational data, understand the

information flow, finding out bottlenecks and evolving solutions for overcoming the weaknesses

of the system so as to achieve the organizational goals.

System Analysis also includes sub-dividing of complex process involving the entire system,

identification of data store and manual processes.

The major objectives of systems analysis are to find answers for each business process: What is

being done How is it being done, who is doing it, When is he doing it, Why is it being done and

369


How can it be improved? It is more of a thinking process and involves the creative skills of the

System Analyst.

It attempts to give birth to a new efficient system that satisfies the current needs of the user and

has scope for future growth within the organizational constraints. The result of this process is a

logical system design. Systems analysis is an iterative process that continues until a preferred

and acceptable solution emerges.

System Design

Based on the user requirements and the detailed analysis of the existing system, the new system

must be designed. This is the phase of system designing. It is the most crucial phase in the

developments of a system. The logical system design arrived at as a result of systems analysis is

converted into physical system design. Normally, the design proceeds in two stages:

Preliminary or General Design

Structured or Detailed Design

Preliminary or General Design: In the preliminary or general de-sign, the features of the new

system are specified. The costs of implementing these features and the benefits to be derived are

estimated. If the project is still considered to be feasible, we move to the de-tailed design stage.

Structured or Detailed Design: In the detailed design stage, computer oriented work begins in

earnest. At this stage, the design of the system becomes more structured. Structure design is a

blue print of a computer system solution to a given problem having the

System Coding

The system design needs to be implemented to make it a workable system. This demands the

coding of design into computer understandable language, i.e., programming language. This is

also called the programming phase in which the programmer converts the program specifications

into computer instructions, which we refer to as programs. It is an important stage where the

defined procedures are transformed into control specifications by the help of a computer

370


language. The programs coordinate the data movements and control the entire process in a

system.

System Testing

Before actually implementing the new system into operation, a test run of the system is done for

removing the bugs, if any. It is an important phase of a successful system. After codifying the

whole programs of the system, a test plan should be developed and run on a given set of test

data. The output of the test run should match the expected results. Sometimes, system testing is

considered a part of implementation process.

Using the test data following test run are carried out:

Program test: When the programs have been coded, compiled and brought to working

conditions, they must be individually tested with the prepared test data. Any undesirable

happening must be noted and debugged (error corrections)

System Test: After carrying out the program test for each of the programs of the system and

errors removed, then system test is done. At this stage the test is done on actual data. The

complete system is executed on the actual data. At each stage of the execution, the results or

output of the system is analyzed. During the result analysis, it may be found that the outputs are

not matching the expected output of the system. In such case, the errors in the particular

programs are identified and are fixed and further tested for the expected output.

When it is ensured that the system is running error-free, the users are called with their own actual

data so that the system could be shown running as per their requirements.

System Implementation

After having the user acceptance of the new system developed, the implementation phase begins.

Implementation is the stage of a project during which theory is turned into practice. The major

steps involved in this phase are:

Acquisition and Installation of Hardware and Software

Conversion

User Training

371


Documentation

System Maintenance

Maintenance is necessary to eliminate errors in the system during its working life and to tune the

system to any variations in its working environments. It has been seen that there are always some

errors found in the systems that must be noted and corrected. It also means the review of the

system from time to time. The review of the system is done for:

Knowing the full capabilities of the system

Knowing the required changes or the additional requirements

Studying the performance

N.B. If a major change to a system is needed, a new project may have to be set up to carry out

the change. The new project will then proceed through all the above life cycle phases.

Computer professions (Careers in ICT industry)

This refers to the job titles or professions related to information communication

(ICT). The high growth rate in ICT industry has resulted into many new kinds

of jobs and careers.

Different careers in the field of computing

Computer operators

Responsibilities

Entering data into the computer for processing

Keeping up-to-date records of all information processing activities

Computer technician

Computer technician is a person responsible for the maintenance, upgrading and

repairing of computers and related devices

Responsibilities

Troubleshooting computer hardware and software related problems

Assembling and upgrading computers and their components

372


Ensuring that all computer related accessories such as printers, modems, storage media

and devices are in a good working condition.

Systems analyst

This is a person who is responsible for analyzing a company‘s needs or problems, then

designs and develops a computer based information system to help prevent the problem.

Responsibilities

Reviewing the current manual or redundant information system and making

recommendations on how to replace it with a more efficient one.

Working with programmers to construct and test the system.

Coordinating training for users on how to use the new system

Computer programmer

Responsibilities

Writing application programs or system programs.

Customizing commercial application package to suite the organization needs.

Testing, debugging, installing and maintaining programs developed or

customized for the organization.

Software developer (engineer)

Software developer is a person who is skilled in software development and

technical operation of computer hardware.

Responsibilities

Developing system and application software

Developing user and technical documentations for the new software.

Maintaining and updating the software to meet day to day requirements while

overcoming challenges.

Computer engineer

Computer engineer is a technical person with skills and knowledge of designing and

developing computer components such as storage devices, motherboards, and other

electronic components.

Responsibilities

373


Determine the electrical power requirement of each computer component.

Re – engineer computer components to enhance its functionality and efficiency.

Design and develop engineering and manufacturing computer controlled devices such

as robots.

Information systems manager

Responsibilities

He controls, plans, staffs, schedules and monitors all the activities of the ICT

department in the organization.

Test the impact that an alternative course of action might have on the business.

Ensures that all tasks in the IT department are done correctly and on time in order to

support business planning, control and decision making process.

Prepares budgets for the ICT department.

Keeps the department‘s inventory records up-to-date.

Managing the human resource within the ICT department.

Database administrators (DBA)

Responsibilities

Designing and developing database applications for the organization.

Setting up security measures needed to control access to data and information.

Keeping the database up-to-date by adding new records, modifying or deleting un

necessary records.

Computer trainer/Instructor/Teacher

Due to the dynamic nature of computers and information technology, there is a high

demand for qualified ICT trainers.

Responsibilities

Training people on how to use a computer and various application programs.

Developing training reference materials

Guiding learners on how to acquire knowledge through carrying out research.

Advising the learners on the best career opportunities in the broad field of ICT.

Preparing learners for ICT examinations.

374


Website administrator /Webmaster

Responsibilities

Developing and testing websites

Maintaining, updating and modifying information on the websites to meet new

demands by the users.

Monitoring the access and use of internet connection by enforcing security measures.

Downloading information needed by an organization or institution from the internet

websites.

Computer graphics designer

This is a professional responsible who designs and creates either graphics or 3D animations for

software programs, games, movies by people. This person must have a good understanding of

graphic software’s such as Adobe Photoshop, Adobe Illustrator, etc

Network administrator

Responsibilities

This is a professional person responsible for designing, setting up and maintaining a

network

Monitoring the network resources

Troubleshooting network related problems

Secretary

A secretary is a person who uses computers to keep all the necessary

information instead of keeping paper files

375


Abbreviation and Glossary

COMPUTER ABBREVIATIONS AND GLOSSARY

Aa

AD Analog to Digital

AC Alternating Current

ACC Accumulator

ACIA Asynchronous Communication Interface Adapter

ACK Acknowledge

ACR Audio Cassette Recorder

ACU Automatic Calling Unit

ADC Analog to Digital Converter

ADP Analog Data Processing

AI Artificial Intelligence

ALGOL Algorithmic Language

ALU Arithmetic Logic Unit

ANSI American National Standards Institute

APL A Programming Language

APT Automatic Programmed Tools

ASCII American Standard Code for Information Interchange

ASIC Application Specific Integrated Circuits

376


ASR Automatic Send or Receive

ATC Automatic to Copy

ATE Automatic Test Equipment

ATM Automatic Teller Machine

ATP Apple Transaction Protocol

ARPA Advanced Research Projects Agency

AMD Advanced Micro Devices

Bb

BASIC Beginners All-purpose Symbolic Instruction Code

BBS Bulletin Board System

BCC Block Character Check

BCD Binary Code Decimal

BCHC Bose- Chandhuri-Hocquenghem Code

BCS British Computer Society

BIM Beginning of Information Mark

BIOS Basic Input/output System

BNF Backus-Naur Form

BOS Basic Operating System

BOT Beginning Of Tape

BPI Bits per Inch

BSI British Standard Institute

377


BSC Binary Synchronous Communications

BTAM Basic Telecommunications Access Method

Cc

CAD Computer Aided Design

CAI Computer Aided Instruction

CAL Computer Aided Learning

CAM Computer Aided Manufacturing

CAM Content Addressable Memory

CAT Computer Aided Training

CAT Computer Aided Testing

CBL Computer Based Learning

CBMS Computer Based Message System

CBT Computer Based Training

CCD Charge Coupled Device

CCP Command Console Processor

CD Compact Disk

CD-ROM Compact Disk-Read Only Memory

CM Central Memory

CPE Central Processing Element

CPU Central Processing Unit

CGA Color Graphics Adapter

378


CIM Computer Input from Microfilm

CIR Current Instruction Register

CISC Complex Instruction Set Computer

CM Central Memory

CMI Computer Managed Instruction

CML Computer Managed Learning

CMOS Complementary Metal Oxide Semiconductor

CNC Computer Numeric Control

COBOL Common Ordinary Business Oriented Language

CODEL Coder/Decoder

CSMA-CD Carrier Sense Multiple Access-Collision-Detection

COM Computer Output on Microfilm

COMAL Common Algorithmic Language

CP/M Control Program for Micro computers

CP/M Control Program/Monitor

CORAL Common Real time Applications Language

CP Card Punch

CPM Critical Path Method

CPI Characters per Inch

CPS Character per Second

CR Carriage Return / Card Reader

379


CRC Cyclic Redundancy Check

CR/LF Carriage Return/Link Feed

CRT Cathode Ray Tube

CSM Combined Symbol Matching

CTRL Control

CTS Clear To Send

CU Control Unit

CUG Closed User Group

CAR Current Address Register

CIR Current Instruction Register

CWP Communicating Word Register

CD-R Compact Disk-Recordable

CD-RW Compact Disk-Rewritable

CVP Computer Virus Protection

CC Carbon Copy

CMY Cyan Magenta and Yellow

CLI Command Line Interface

Dd

3D Three Dimensional

DAC Digital to Analog Converter

DAMA Demand Assigned Multiple Access

380


DASD Direct Access Storage

DBA Database Administrator

DBMS Database Management System

DC Direct Current

DCD Data Carrier Defect

DCE Data Communications Equipment

DD Double Density

DDC Direct Digital Control

DDE Direct Data Entry

DD/D Data Dictionary/Directory

DDL Data Description Language

DDP Distributed Data Processing

DES Data Encryption Standard

DFD Data Flow Diagram

DIB Data Input Bus

DIN Deutsche Industry Norm

DIP Dual Inline Package

DIANE Direct Information Access Network for Europe

DMA Direct Memory Access

DML Data Manipulation Language

DOR Digital Optical Reading

381


DOS Disk Operating System

DP Data Processing

DPI Dots per Inch

DPM Data Processing Manager

DRAM Dynamic Random Access Memory

DRO Destructive Readout

DSR Data Set Ready

DSW Device Status Word

DTE Data Terminal Equipment

DTP Desk Top Publishing

DTR Data Terminal Ready

DVD Digital Video Disks

DVD Digital Versatile Disk

DNS Domain Name System

DSL Digital Subscriber Line

DARPA Defense Advanced Research Projects Agency

Ee

EDVAC Electronic Discrete Variable Automatic Computer

EAPROM Electrically Alterable Programmable-Read Only Memory

EAROM Electrically Alterable Read Only Memory

EBCDIC Extended Binary Coded Decimals Interchange Code

382


EBNF Extended Backups Naur Form

EBR Electron Beam Recording

ECL Emitter Coupled Logic

EDP Electronic Data Processing

EDS Exchangeable Disk Storage

EEPROM Electronically Erasable Programmable Read Only Memory

EEROM Electronically Erasable Read Only Memory

EFT Electronic Funds Transfer

EFTPOS Electronic Fund Transfer Point of Sale

EGA Enhanced Graphics Adapter

EIA Electronically Industry Association

EM End of Medium

EMI Electromagnetic Interface

ENQ ENQIRY

EOA End of Address

EOB End of Block

EOD End of Data

EOF End of File

EOJ End of Job

EOM End of Message

EOR End of Record

383


EOT End of Text/Transmission

EPOS Electronic Point Of sale

EPROM Electrically Programmable Read-Only-Memory

EROM Erasable Read Only Memory

EUL End User License

EIDE Enhanced Integrated Drive Electronics

ENIAC Electronic Numeric Integrator and Calculator

EDAC Error Detection and Correction

ESC Escape Character Code

ESDI Enhanced Small Device Interface

EXNOR Exclusive Nor

EXOR Exclusive OR

EDVAC Electronic Discrete Variable Automatic Computer

Ff

FAM Fast Access Memory

FD Full Duplex

FDC Floppy Disk Controller

FDX Full Duplex

FEDS Fixed and Exchangeable Disk Storage

FEP Front End Processor

FET Field Effect Transmitor

384


FF Form Feed/Flip-Flop

FIFO First in First out

FLOP Floating Point Operation

FD Floppy Disk

FORTRAN Formula Translator

FOSDISC Film Optical Scanning Device for Input into Computer

FROM Fusible Read Only Memory

FPD Flat Panel Display

FTP File Transfer Protocol

Gg

GINO Graphical Input Output

GKS Graphics Kernel System

GND Ground

GPIB General Purpose Interface Bus

GPR General Purpose Register

GPL General Public License

GB Giga Byte

GHZ Giga Hertz

GPS Geographical Positioning System

GUI Graphical User Interface

GIS Geographical Information System

385


GPD Gas Plasma Display

Hh

H&Y Hype nation and Justification

HD Half Duplex

HDLIC High Data Link Control

HDX Half Duplex

HLDLIC High-Level Data Link Control

HLL High Level Language

HMI Human Machine Interface

HOF Head of Form

HRG High Resolution Graphics

Hz Hertz

HDTV High Definition Television

HF High Frequency

HTML Hyper Text Markup Language

HPNA Home Phone Line Network Adapter

Ii

IAM Intermediate Access Memory

IAR Instruction Address Register

IAS Intermediate Access Store

IBG Interblock Gap

386


IC Integrated Circuit

ID Identification

IDP Integrated Data Processing

IEE Institution of Electrical Engineers

IEEE Instruction of Electrical and Electronic Engineers

IH Interrupt Handler

IKBS Intelligence Knowledge Based System

I/O Input/output

IOP Input/output Processor

IORQ Input/output Request

IP Information Provider

IPL Initial Program Leader

IPS Inches per Second

IPSE Integrated Project Support Environment

IR Information Retrieval

ISAM Indexed Sequential Access Method

ISDN Integrated Services Digital Network

ISO International Standards Organization

ISO/OSI International Standards Organizations/Open System Interconnection

ISR Information Storage and Retrieval

IT Information Technology

387


ITS Invitation to Send

ICU Intensive Care Unit

IDE Integrated Drive Electronic

IrDA Infrared Data Association

IRQ Interrupt Request

IP Internet Protocol

ISA Industry Standard Architecture

IRC Internet Relay Chart

ISP Internet Service Provider

IMAP Internet Mail Access Protocol

ICT Information Communication Technology

IPX Inter-network Packet Exchange

IR Instruction Register

IBM International Business Machine

IRG Inter-Record Cap

Jj

JCL Job Control Language

JPEG Joint Photographic Experts Group

Kk

KB Kilo Byte

KIPS Kilo Instruction per Second

388


KSR Keyboard Send/Receive

KW Kilo Word

KHz Kilo Hertz

KBps Kilobytes per Second

Ll

LAN Local Area Network

LASER Light Amplification by Stimulated Emission of Radiation

LSI Large Scale Integration

LIFO Last in First out

LCD Liquid Crystal Display

LCP Link Control Procedure

LSD List Significant Digit

LSB Least Significant Bit

LF Line Feed

LPM Lines per Minute

LIPS Logical Inferences per second

LISP List Processing

LLL Low-Level Language

LQ Letter Quality

LUT Look Up Table

LARC Liver more Automatic Research Computer

389


LED Light Emitting Diodes

LPT Line Printer

Mm

MROM Mask Read Only Memory

Mbps Megabits per second

MFLOPS Mega Floating Point Operations per Second

MAC Message Authentication/medium Access Control

MAR Memory Address Register

MB Mega Byte

MBR Memory Buffer Register

MCP Master Control Program

MDR Memory Data Register

MICR Magnetic Ink Character Recognition

MIMD Multiple Instruction Stream Multiple Data

MIPS Million Instructions per Second

MIS Management Information System

MISD Multiple Instruction Stream-Single Data

MMI Man Machine Interface

MOS Metal Oxide Semi-conductor

MAN Metropolitan Area Network

MIC Magnetic Ink Character

390


MSR Magnetic Strip Recognition

MODEM Modulator/Demodulator

MOSFET Metal Oxide Semi-conductor Field Effect Transistor

MPS Microprocessor System

MPU Microprocessor Unit

MSB Most Significant Bit

MSD Most Significant Digit

MSI Medium Scale Integration

MTBF Mean Time between Failures

MTF Mean Time to Fail

MUX Multiplexer

MM Memory Management

Nn

NAK Negative Acknowledgement

NCBD Natural Binary Coded Decimal

NC Numerical Control

NDR Non Destructive Readout

NEQ Non-Equivalence

NLQ Near Letter Quality

NMI Non-maskable Interrupt

NRZ Non-Return to Zero

391


NCSA National Centre for Super Computing Applications

NCP Network Control Protocol

NLSP Network Link Services Protocol

NIC Network Interface Card

NDT Non-Destructive Testing

Oo

OA Office Automation

OCP Order Code Processor

OCR Optical Character Reader

OCR Optical Character Recognition

OEM Original Equipment Manufacture

OMR Optical Mark Reader

OMR Optical Mark Recognition

OS Operating System

OSI Open System Interconnection

O/P Output

OV Overflow

OBR Optical Bar Recognition

OC Optical card

OT Optical Tape

OOPL Object Oriented Programming Language

392


Pp

PAD Packet Assembler Disassembler

PC Personal computer

PCB Printed Circuit Board

PCM Plug-compatible Manufacturer

PCU Peripheral Control Unit

PDL Page Description Language

PDL Program Design Language

PDN Public Data Network

PERT Program Evaluation and Review Technique

PIA Peripheral Interface Adapter

PID Personal Identification Device

PIN Personal Identification Number

PIO Parallel Input Output

PIPO Parallel Input/Parallel Output

PISO Parallel Input/Serial Output

PL Programming Language

PLA Programming Logic Array

PLD Programmable Logic Device

PL/M Programming Language for Microprocessors

PMOS P-channel Metal Oxide Semiconductor

393


POL Problem Oriented Language

POS Point of Scale

PPM Pages per Minute

PROLOG Programming in Logic

PROM Programmable Read Only Memory

PS Pico Second

PSN Packed Switched Network

PSU Power Supply Unit

PSW Processor Status Word

PTR Paper Tape Reader

PCs Punched Cards

PDP Personal Digital Assistant

POST Power on Self Test

Ps/21 Personal System 2 Interface

POP Post Office Protocol

PPP Point to Point Protocol

PCMCIA Personal Computer Memory Card International Association

PCI Peripheral Components Interconnection

Qq

QBE Query by Example

QISAM Queved Indexed Sequential Access Method

394


QSAM Queved Sequential Access Method

QL Query Language

Rr

R&D Research and Development

RAM Random Access Memory

RGB Red Green Blue

RISC Reduced Instruction Set Computer

RJE Remote Job Entry

RO Receive Only

ROM Read Only Memory

RPG Report Program Generator

RTE Real Time Execution

RTS Request to Send Signal

R/W Read/Write

R/WH Read/Write Head

RSI Repetitive Strain Injuries

RFC Request for Comments

RS Record Separator

Ss

SVGA Super Video Graphics Array

SAM Serial Access Memory

395


SAR Store Address Register

SBC Single Board Computer

SCR Sequence Control Register

SCSI Small Computer System Interface

SD Single Density/Disk

SDLC Synchronous Data Link Control

SIMD Single Instruction Stream Multiple Data Stream

SIO Serial Input Output

SIPO Serial Input/Parallel Output

SISD Single Instruction Steam Single Data Stream

SISO Serial Input Serial Output

SLSI Super Language Scale Integration

SNA Systems Network Architecture

SNOBOL String Oriented Symbolic Language

SP Stack Pointer

SPX Simplex

SQA Software Quality Assurance

SSD Single Sided Disk

SSI Single Scale Integration

STX Start of Text

SD Super Disk

396


SRAM Static Random Access Memory

SXGA Super Extended Graphics Array

SATA Serial Advanced Technology Attachment

STP Shielded Twisted Pair

SPX Sequence Packet Exchange

SMS Short Message Service

SMTP Simple Mail Transfer Protocol

SLIP Service Line Internet Protocol

Tt

TAB Tabulate

TAT Turn around Time

TDS Transaction Driven System

TTY Teletype

TV Television

TP Teleprocessing

TPI Tracks per Inch

TSW Telesoftware

TTL Transistor-Transistor Logic

TX Transmitter

TFTs Thin Film Transistors

TB Tera Byte

397


TCP/IP Transmission Control Protocol

TCP Transmission Control Protocol

TELNET Terminal Emulation Protocol

TLD Top-Level-Domain

Uu

UART Universal Asynchronous Receiver Transmitter

UBC Universal Block Channel

ULA Uncommitted Logic Array

UPC Universal Product Code

UPS Uninterruptable Power Supply

USART Universal Synchronous Asynchronous Receiver Transmitter

USASCII Universal synchronous Asynchronous Standard for Information Interchange

USRT Universal synchronous Receiver Transmitter

UV Ultraviolet Light

UXGA Ultra Extended Graphics Array

USB Universal Serial Bus

UTP Unshielded Twisted Pair

UHF Ultra High Frequency

URL Uniform Resource Locator

UDP User Datagram Protocol

UTL Uganda Telecom Limited

398


Vv

V&V Verification and Validation

VDT Visual Display Terminal

VDU Visual Display Unit

VFU Vertical Format Unit

VHD Very High Density

VLSI Very Large Integrated Circuits

VRAM Video Random Access Memory

VROM Video Read Only Memory

VRC Vertical Redundancy Checks

VS Virtual Storage

VGA Video Graphics Array

VCD Video Compact Disk

VR Virtual Reality

VSAT Very Small Aperture Terminal

VHF Very High Frequency

Ww

WAN Wide Area Network

WYSIWYG What You See Is What You Get

WYSIAYG What You See Is All You Get

WIMP Windows Icon Mouse Printers

399


WISC Writable Instruction Set Computer

WORM Write Once Read Many

WP Word Processing

WPM Words per Minute

WOS Windows Operating System

WAP Wireless Application Protocol

WWW World Wide Web

Xx

XGA Extended Graphics Array

XHTML Extensible Hyper Text Markup Language

XML Extensible Markup Language

Zz

ZIF Zero Insertion Force

COMPUTER TERMS

AAL (ATM Adaptation Layer): adapts PDUs passed down from higher layers onto ATM cells

Active hub: allows multiple devices to be wired to a central location to share the same media and

regenerate the signal; also referred to as multiport repeaters.

ADSL (Asymmetric Digital Subscriber Line): typical form of xDSL telephone companies offer

to residences

AGP (accelerated or advanced graphics port): a high-speed, point-to-point channel for attaching

a graphics card to a computer’s motherboard, primarily to assist in the acceleration of 3D

computer graphics

400


ALU (arithmetic logic unit): a digital circuit that calculates an arithmetic operation (e.g.,

addition, subtraction) and logic operations between two numbers; the fundamental building block

of the Central Processing Unit (CPU) or a computer

AM (amplitude modulation): a technique used for transmitting information via a radio carrier

wave

Amplitude: height of the wave at any point in the wave

ANSI (American National Standards Institute): a voluntary organization that coordinates the

development and use of consensus standards in the United States and represents the needs and

views of U.S. stakeholders in standardization forums around the globe

API (application programming interface): gives programmers a formal set of routines to call on

to use underlying network services

Application layer: performs the functions of file transfer, e-mail, etc. (see OSI Model)

Architecture: how a system is designed; includes how the components are connected to and

operate with each other

ARP (address resolution protocol): network layer protocol provided with TCP/IP; used to map

an IP (internet protocol) address to a MAC (media access card) address

ASCII (American Standard Code for Information Interchange): relates a number from 0 to 255

in the binary (base 2) form to keyboard characters

ASIC (application-specific integrated circuit): an integrated circuit designed for a particular use

(e.g., a chip designed solely to run a cell phone)

Asynchronous communication: describes when devices, such as computers, rely on their own

internal clocks; it provides connectivity to printers, modems, fax machines, etc.

ATM (asynchronous transfer mode): high bandwidth, cell-switching technology; designed to

carry many different types of information, including voice, video, image, data, and graphics;

another form of STDM (statistical time division multiplexing)

401


AUI (attachment unit interface): a 15-pin connection that provides a path between a node’s

Ethernet interface and the medium attachment unit (MAU); also known as a transceiver

AS (Autonomous system): collection of IP networks under the control of a single entity

B (bearer) channel: carries voice, video, image, or data traffic, depending upon the equipment

and applications available

Bandwidth: expressed in a range of frequencies using hertz as the unit of measurement; also

called analog capacity

Base 2 System: binary number system, only two discrete values (0 and 1) are possible and all

numbers are a combination of these two characters; digital signals are numbers sent in the Base 2

system

Base 10 System: the decimal system

Baseband: describes signals and systems whose range of frequency is measured from 0 to a

maximum bandwidth or highest signal frequency; sometimes used as a noun for a band of

frequencies starting at 0

BGP (border gateway protocol): an inter autonomous system routing protocol; a network or

group of networks under a common administration and with common routing policies

Bit: contraction of the expression “binary digit”; smallest unit of data in a computer

BIOS (basic input/output system): the firmware code run by an IBM-compatible PC when first

powered on, known as “booting up”; primary function is to prepare the machine so other

software programs can load, execute, and assume control of the PC

Bluetooth: specification that allows mobile phones, computers, and PDAs to be connected

wirelessly over short ranges

Bps: bits per second: common measure of data speed for computer modems and transmission

carriers

402


BRI (basic rate interface): an integrated services digital network configuration, usually intended

for the home and small enterprise (see also PRI)

Bricks and clicks: business that existed pre-Internet that now uses e-commerce technology to

sell on the Internet

Bridge: interprets the LAN hardware adapter address contained in MAC and decide whether to

filter or forward the frame; does not change the frame in any way

Browsers: client applications that access WWW servers

Building backbone: connects LANs within a building

Bus: electrical connection between any two components in a computer

Bus topology: system layout where electrical signals generated by a device connected anywhere

on the bus are received by all other connected devices

Byte: the standard size of data in a computer; 8-bits

Cache: keeps data the processor is likely to need quickly close at hand; increases processor

operation speed

CAD/CAM (computer-aided design/computer-aided MANUFACTURING ): software used to

design products such as electronic circuit boards in computers

Campus backbone: connects building LANs together

CD-R (compact disc - recordable): special type of CD-ROM that can be written onto by any

computer with a recording drive; can only be written onto once

CD-ROM (compact disc read-only memory): optical storage device read by lasers; can hold up

to 700 megabytes of data

CD-RW (compact disc - rewritable): special type of CD-ROM that can be written onto by any

computer with a recording drive; can be written onto more than once

403

http://jobsearchtech.about.com/od/techindustryresources/a/Tech_Terms_2.htm


CIR (committed information rate): describes the user information transfer rate the network

supports during normal network operations

CLEC (competitive local exchange carrier): In the US, a telecommunications provider company

(also called a carrier) that competes with other, already established carriers (the local telephone

company)

Client/server architecture: network where some computers are dedicated clients (workstations)

and some are dedicated servers; information is centralized on the server, and an administrator

sets policies and manages it

CMOS (complementary metal-oxide semiconductor) RAM: requires very little power; maintains

information even when the computer is off

Collision: occurs when several network users communicate at the same time and interfere

(collide) with one another

Collision domain: logical network segment where data packets can "collide" with one another

for being sent on a shared medium, in particular in the Ethernet networking protocol

Computer networking: a combination of hardware and software that lets the various computers

in an organization communicate with one another

Computer operating system (OS): special computer program that provides an environment in

which other programs can use the computer’s central processor and the attached input/output

devices

Connectivity devices: bring users of the network into contact with one another

Constant bit rate (CBR): transmission that uses a set amount of network capacity on a

continual basis; used when the arrival of the information is time-sensitive

Convergence: the merging and sometimes clashing of voice and data

CPE (customer premises equipment): generally refers to telephones, DSL or cable modems, or

purchased set-top boxes for use with communication service providers’ services

404


CPS (cycles per second): measure of how frequently an alternating current changes direction;

has been replaced by the term hertz (Hz)

CPU (Central Processing Unit): the brain of the computer system where calculations and

decisions are made; also referred to as the processor

CPU Speed: how fast the CPU works

CSU (channel service unit): provides a loopback function for telephone-company testing, and

checks bipolar signal generation

CRC (cyclic redundancy check): method of checking for errors in data that has been

transmitted on a communications link; a function used to produce a Checksum against a block of

data

CS (convergence sub-layer): particular protocols that are responsible for gathering and

formatting higher layer information so it can be processed by the lower layers

CSMA/CD (carrier sense multiple access/collision detect): set of rules for determining how

network devices response when two devices collide

D (data) channel: used for common channel signaling by both the telephone company switch

and the customer equipment; provides the call signals that set up B channel connections

DACS (digital access and cross-connect system): a piece of telecommunications equipment

used for routing T1 lines; can cross-connect any T1 line in the system with any other T1 line in

the system

Data: information manipulated inside the computer in the form of bits and bytes

Datagram: data packet that is sent over an IP network; associated with the network layer when

communication protocol is connectionless

DCE (data communications equipment OR data circuit-terminating equipment): a device that

communicates with a data terminal equipment (DTE) device in a particular standard

405


DDP (datagram delivery protocol): a member of the AppleTalk networking protocol suite,

mainly responsible for socket-to-socket delivery of datagram over an AppleTalk network

DE (discard eligibility): signal used to identify less important data traffic that can be dropped

during periods of congestion on the system

DLCI (data link connection identifier): a channel number that tells the network how to route the

data

DMA (direct memory access): a feature that allows certain hardware subsystems in a computer

to access system memory for reading and/or writing independently of the CPU; can include disk

drive controllers, graphics cards, network cards, and sound cards

DOS (disk operating system): a family of closely related operating systems (COS) that ran on

IBM PC type hardware.

DNA (digital network architecture): a set of specifications or protocols created by Digital

Equipment Corporation (DECnet) that evolved into one of the first peer-to-peer network

architectures

DNS (domain name system): service that connects a domain name to an IP address

DRAM (dynamic random access memory): primary choice for holding large amounts of

information due to its inexpensive cost; must be refreshed or rewritten frequently (about every

386 milliseconds)

DS0 (digital signal, level 0): basic digital signaling rate of 64 kbit/s, corresponding to the

capacity of one voice-frequency-equivalent channel

DS1 (digital signal, level 1): also known as T1; widely used to transmit voice and data between

devices

DSL (digital subscriber line): technology that delivers digital data transmission over the wires of

a local telephone network

DVD (digital versatile disc): can hold over seven times as much information as CDs

406


DWDM (dense wavelength-division multiplexing): an optical technology used to increase

bandwidth over existing fiber optic backbones (see building backbone, campus backbone)

EBCDIC (extended binary coded decimal interchange code): 8-bit character encoding table used

by ISM mainframes

EGP (exterior gateway protocol): a protocol commonly used between hosts on the Internet to

exchange routing table information

EMI (electromagnetic interference): radiation that causes unwanted signals (interference or

noise) to be induced in other circuits; also called radio frequency interference or RFI

Enterprise network: connects many types of networks

Ethernet: most commonly used protocol designed to change the packets into electrical signals

that can be sent out over the wire

Exterior protocols: routing protocol used between autonomous systems

FAT (file allocation table): table that the operating system uses to locate files on a disk; because

a file may be divided into many sections that are scattered around the disk, the FAT keeps track

of all the pieces

FDDI (fiber distributed data interface): a set of ANSI protocols for sending digital data over

fiber optic cable (see ANSI)

FDM (frequency-division multiplexing): permits a range of input signals to be carried over a

communication line that uses separate carrier frequencies for each signal channel; mostly used

for analog information but can carry digital

File management system: way to store and retrieve information from disk drives; controls how

files can be created, accessed, retrieved, and deleted

Firewall: a barrier between a network and the Internet through which only authorized users can

pass; set of security policies to screen incoming and outgoing messages; also used to isolate one

part of a network from another

407


Floppy drive: early versions were actually floppy; today, they use hard 3.5 inch disk; also

referred to as removable drive

Frame: data structure that collectively represents the transmission stream (headers, data, and the

trailer) and provides the information necessary for the correct delivery of the data

Frame relay: service with standards and specifications designed to transmit data; some users

have had success at transmitting voice

FRAD (frame relay access device): software that frames the customer’s payload with the Frame

Relay overhead information, including the first DLCI (data link connection identifier) address, to

prepare it for delivery to the network

Frequency: number of times a wave repeats a cycle in a one-second period; measured in cycles

per second, or hertz

FTP (file transfer protocol): application used to transfer a copy of a file from one computer to

another computer with one acting as client and the other as server; a login with a user name and

password is typically required

Full-duplex link: enables both sides to simultaneously send and receive data; could require two

separate cables, one in each direction or a single multiplexed cable

Gateways: a node on a network that translates (converts protocol) from one operating system

environment to another

Gateway routers: used to implement exterior protocols and interconnect autonomous systems

Gbps (gigabits per second; billions of bits per second): a data transfer speed measurement for

high speed networks

GUI (graphical user interface): easy way of accessing applications with the use of a pointing

device, such as a mouse; pronounced “gooey”

Half-duplex link: enables one side to transmit and receive, but not simultaneously; information

only flows in one direction at a time using a control procedure to mediate

408


Host-to-host layer: part of the TCP/IP model that performs the same function as the transport

layer in the OSI model

Host address: part of an IP address that is uniquely assigned by an administrator

HTTP (hypertext transfer protocol): protocol users interact with (by means of a browser) to

access Web pages over an internet or intranet

Hubs: bring the users of the network into contact with one another

Hz (hertz): unit of frequency; one hertz simply means one cycle per second, applied to any

periodic event (e.g., one tick of a clock is 1 Hz; the human heart beats at 1.2 Hz)

ILECs (incumbent local exchange carriers): a telephone company providing local service when

the Telecommunications Act of 1996 was enacted (see CLEC)

ILP (initial loader program): reads an existing file containing database records; also called a

boot-loader

Input/output management routines: provide orderly control and flow of information between a

computer’s main memory and attached peripheral devices

Interface: point in the system where the rules, control codes, formats, and information direction

(as dictated by the protocol) are implemented

Interior protocols: routing protocol used within/interior to an independent/ autonomous system

Internet layer: part of the TCP/IP model that performs the same function as the network layer of

the OSI model

Internetworking: connecting one network to another network

Interprocess communication: allows programs to share information dynamically, whether

running locally or remotely

409


I/O (Input/output devices): hardware used to enter and retrieve data from the system

IP (internet protocol): network layer protocol provided with TCP/IP; connectionless, unreliable

protocol that provides features for addressing, type or service specification, fragmentation and

reassembly, and security

IP address (internet protocol address): logical address assigned to every workstation, server,

printer, and router on any interconnected network

IPX/SPX (Internetwork packets exchange/sequenced packet exchange): a networking

protocol used by the Novell NetWare operating systems; it is a datagram protocol used for

connectionless communications

IRC (Internet relay chat): allows groups to communicate interactively via keyboard and screen

display

ISDN (Integrated Services Digital Network): a circuit-switched telephone network system

designed to allow digital transmission of voice and data over ordinary copper telephone wires

ISDN PRI: switched-line service from telephone companies that operates over T1 (or E1/J1)

facilities

IS-IS (intermediate system-to-intermediate system): an interior gateway protocol (IGP) intended

for use within an administrative domain or network

ISPs (Internet service providers): businesses or organizations that provide consumers with access

to the Internet and related services

IT (information technology): broad term that can refer to anything from mainframes to PDAs;

any technology that moves information (voice, video, or data)

ITU-T (ITU Telecommunication Standardization Sector): coordinates standards for

telecommunications on behalf of the International Telecommunication Union (ITU)

IXC (interexchange carrier): a telephone company that provides connections between local

exchanges in different geographic areas

410


Jitter: distortion in a digital signal caused by a shift in timing pulses; can cause data

interpretation errors

JPEG (Joint Photographic Experts Group): a lossy compression technique for color images;

pronounced jay-peg (see Lossy)

Kbps (thousands of bits per second): a measure of data transfer speed

kHz (kilohertz): a unit of measurement of frequency, also known as cycles per second; e.g., one

kilohertz equals 1,000 Hz, or cycles per second

LAN (local area network): network that operates within a small geographic area, usually within a

building, office, or department

LAPB (link access protocol, balanced): a data link protocol in the X.25 stack

LATAs (local access and transport areas): In the US, refers to a geographic region assigned to

one or more telephone companies for providing communication services

Layer 2 switches: interpret and make switching decisions on the LAN hardware adapter address

contained in the data link header of MAC frames; forward frames only to the destination

hardware address contained in the frame

LCI (logical channel identifier): used to define frequencies in use on M/A-COM EDACS

(Enhanced Digital Access Communications System) systems and LTR (logic trunked radio)

systems; more commonly known as logical channel number (see LCN); also known as virtual

channel

LCN (logical channel number): used to define frequencies in use on M/A-COM EDACS

(Enhanced Digital Access Communications System) systems and LTR (logic trunked radio)

systems; also known as the logical channel identifier (see LCI); also known as virtual channel

LE (local exchange): a regulatory term in telecommunications for local telephone company

Leased lines: another name for private lines, dedicated lines, or permanent circuits

LEC (local exchange carrier): a public telephone company in the US that provides local service

411


LGN (logical channel group number): together with the LCN (in the X.25 packet header),

identifies the actual logical channel number of the DTE-DCE link; a 4-bit field representing a

number between 0 and 15

Line layer: layer of the OSI physical layer that is responsible for synchronizing and multiplexing

multiple streams of data into one SONET stream within SONET frames; also monitors and

administers SONET multiplexers

LLC (logical link control): standard interface allowing any combination of MAC techniques and

physical media to be used simultaneously in the same workstations; shields higher layer

protocols from the peculiarities of the physical medium

Logical segmentation devices: allow network designers to maintain separate networks (often for

security reasons) that can still communicate with one another

Lossy: data compression method where compressing and then decompressing retrieves data that

may well be different from the original, but is "close enough" to be useful in some way

LU (logical unit): identifies an end-user in IBM's Systems Network Architecture (SNA)

MAC (media access control) address: unique 6-byte address associated with and coded into each

network interface card (NIC); address assignment is controlled by the IEEE

MAN (metropolitan area network): connects sites in and around a large city

MB (megabyte): unit of information or computer storage equal to either exactly one million

bytes or, in some cases, 1,048,567 bytes, or more rarely, 1,024,000 bytes; not to be confused

with Mb, which stands for megabits

Mbps (megabits per second): a unit of information storage; not to be confused with MB or

megabytes

Medium: transmission, or system that carries the message or data

MAU (medium attachment unit): converts signals on an Ethernet cable to and from AUI signals

412


Memory: desk space of the computer system; microchips located on the motherboard that hold

data and instructions for the CPU (central processing unit)

Memory management: allocates memory to separate tasks and protects data from corruption

Menu: used in some DOS shells and early versions of Windows; an improvement on the

command line but cumbersome when a task requires the submenu of a submenu of a submenu of

a menu item

Message: information content to be shared

MHz (megahertz): one hertz is one cycle per second; a megahertz is equal to one million cycles

per second

MIB (management information base): a type of database used to manage the devices in a

communications network

MPEG (Motion Picture Experts Group): digital video format identified by “.mpg” extension

after the file name; a working group of ISO/IEC charged with the development of video and

audio encoding standards; pronounced m-peg

MPLS (multiprotocol label switching): an initiative that integrates Layer 2 information about

network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous

system to simplify and improve IP packet exchange

Mpps (millions of packets per second): a measurement of information sent per second

Multiplexing: process of putting multiple signals on a wire simultaneously

Multiport repeaters: allow multiple devices to be wired to a central location, share the same

media, and regenerate (repeat) the signal; also referred to as active hubs

Multitasking routines: permit two or more distinct tasks to be performed concurrently by the

computer

413


Name resolution: process by which the peer-to-peer name used on each conversational level is

related to other levels

NAP (network access point): transitional data communications facilities at which Network

Service Providers (NSPs) would exchange traffic, in replacement of the publicly-financed

NSFNet Internet backbone; now replaced by modern IXPs

NAT (network address translator): involves re-writing the source and/or destination addresses of

IP packets as they pass through a router or firewall; also called network masquerading, native

address translation, or IP-masquerading

NetBIOS (network basic input/output system): allows applications on separate computers to

communicate over a local area network (LAN)

Network access layer: allows a computer to exchange data with another computer over a

common network medium; part of the TCP/IP model that performs the same functions as the

data link and physical layers of the OSI model

Network address: part of an IP address that is uniquely assigned by one of the ICANN-

sanctioned agencies

Network design: how the various clients and servers are arranged for purposes of connectivity,

performance, and security

NOS (network operating system): optimizes the client/server architecture; provides and supports

network services such as file services, e-mail, Internet and intranet services, and applications

NIC (network interface card): hardware adapter that provides communication capabilities;

responsible for building, transmitting, receiving, and decoding frames in a LAN environment;

serves as the interface between the networked devices and the connecting wires

NNTP (network news transfer protocol): makes USENET possible; protocol for the distribution,

inquiry, retrieval, and posting of news articles using a reliable stream-based transmission of news

among the ARPAInternet community

Nonvolatile memory: chips that hold information even when the system is turned off

414


NRZ-L (non-return to zero level): form of digital encoding; negative voltage is used to represent

a binary 1, and a positive voltage is used to represent a binary 0

NSP (network service provider): a business or organization that sells bandwidth or network

access by providing direct backbone access to the Internet, and usually access to it’s network

access points (see NAP)

OC1 (optical carrier, level 1): a fiber optic connection capable of transferring data at 51.85 Mbps

Operating environment: how the OS controls the hardware and application programs

OS (operating system): interface between the application (word processor, spreadsheet, etc.) and

the computer hardware

OSI (open systems interconnection) model: developed to provide a view of the distinct

functionalities that are required to implement each protocol layer; defines a complete range of

functions that can be achieved with data communications equipment

OSPF (open shortest path first): a link-state hierarchical interior gateway protocol (see IGP) for

network routing protocol.

415


416


417


418