Foreword:
Computer studies is a combination of technologies, skills and processes that are used to manage
information-related risks. This book is not just about the notes for the student or the teacher, but
also about empowering the reader with computer-based skills and knowledge that is so paramount
to the pursuance of a better life today.
There is a rare treat in the book stores around town for the reader of this book except this one,
which will not only open up your mind about computer studies but also enable its pass their exams
with flying colours.
The challenges in this subject and the computing industry at all levels are both difficult and
interesting; people are working on them with enthusiasm, tenacity and dedication to continuously
develop solutions so that they can keep up.
In this new age of global interconnectivity, this book is necessary as it is written purposely to cover
all the student’s needs throughout the course of Computer studies in O’ level covering all topics
from senior one to senior four. Not only the student, but also the teacher stands to gain from this
piece of work as it is aimed at simplifying their work in the dissemination of knowledge to the
learners. Therefore it’s a good step in that direction.
The book isn’t just filled with words, but also illustrations to ascertain the different things it talks
about.
I also acknowledge the help given towards the compilation of this book by the I.T Department of
Katwe Noor Secondary School most especially Madam Kauma Rashida, who is endowed with
tremendous experience in computer studies.
Kirumira Hussein
Author
This book belongs to:
Class:
Year:
Please feel free to send us your feedback in case of any additional material, queries and more
copies of this book at:
Email: kirhusgraphicsdesigners@yahoo.com / kirhus19@gmail.com
Tel: 0704 500 847
P.o.Box 21360 Kampala
Computer studies Revised Notes for O level by KH
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SENIOR ONE:
TOPIC 1: INTRODUCTION TO COMPUTERS
1.1 Computers today
A computer ; is an electronic multipurpose machine which is used to in-put data, process data,
store data and out-put data or retrieve information.
Characteristics of modern computers
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Speed: computer are quite fast in their operations in that their speed is measured in millions
instructions per second ie the computer is capable of processing 15 million instructions per
second
Accuracy: Ability of a computer to rarely make mistakes as this largely depends on the quality of
input hence the saying garbage in garbage out (GIGO)
Storage: for a computer to work it must have a work area or work space where data is stored
before and after processing. The space is known as memory
Diligence. Ability of computers to perform related tasks repeatedly without getting tired or
bored.
Artificial intelligence: computers are artificially intelligent as they can respond to requests given
to them and provide solutions. This is done by its programmability ie can be taught to make
decisions and functions accordingly
Automation: computers also work automatically; they do not need to be reminded to perform
any of the instructions when executing a programmed routine. E.g. making a routine daily alarm
at specific times
Versatility: Ability of a computer to handle different tasks at the same time or different
time
TERMINOLOGIES IN COMPUTER STUDIES
Data: means the raw material that is fed into the computer to be processed
This can also be defined as the unprocessed information.
Information: this is processed data or data that has been turned into a meaningful form.
Hard ware: This refers to physical tangible parts of a computer.
Soft ware: This is parts of a computer or instructions a computer must follow to accomplish a
given task.
Icons: Small pictures used to represent programs files, folders, short cuts, hardware or software
features.
File: Data that is stored in memory and named so that it can be easily retrieved for use
Window: A frame that may contain icons or text or pictures
Desktop: The first screen that you see once the computer is fully functioning
Booting: This means to start or restart a computer.
Bug: This is an error in a program that prevent the computer to work properly causing it to freeze
so that nothing works.
Debug: correcting errors in a program
Peripheral devices: These are the devices which can be connected to the computer other than
the basic ones. Examples of peripheral devices are printers, scanners, loudspeakers, joy sticks for
games.
Computer studies Revised Notes for O level by KH
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REASONS FOR STUDYING COMPUTERS
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To acquire general knowledge and skills in the use of computers and related technologies
To use the acquired knowledge in computer studies to enhance learning other subjects
To understand important issues of a technology based society and exhibit them using
computers
To acquire knowledge as a foundation for further studies in computer technology
To use a variety of computer technologies to assess, analyze and interpret information
Jobs
Passing exams
1.2 EVOLUTION OF COMPUTERS (ROOTS OF A COMPUTER)
 Origin of counting
 Mechanical era
 Electro-mechanical era
 Electronic era (including computer generation)
The evolution of computers refers to the stages the computer has under gone through to its current
version, there are many devices that have been used before the invention of the computers .These
include the following;
THE ABACUS
This was the earliest device to be used for adding and subtracting. It was first used in Japan and
China.
THE SLIDE RULE
This device was invented in 1620’s by Willliam Oughtred .The device was used to carry out addition
division, subtraction and multiplication.
NAPIER’S BONES
The device was designed by John Napier .The device uses a set of ivory rods that looked like bones.
The device was designed to solve mathematical calculations like multiplication, addition, subtraction
and division. It is similar on principle to the modern slide rule.
THE MECHANICAL ERA
This was the period between 1623-1944,The machines in this period had the following
characteristics ;
a. Moving parts
b. Electronic relays
c. Mechanical gears
d. Use of punched cards and tapes.
EXAMPLES OF MACHINES IN THE MECHANICAL ERA AND THEIR USES
PASCAL’S ADDING MACHINE.
This was designed by a French philosopher and mathematician called Blaise Pascal. It was the first
mechanical adding machine that uses a system of gears and wheels.
Computer studies Revised Notes for O level by KH
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LEIBNIZ’S STEPPED RECKONER
The device was invented by a German man called GOTTFRIED Wilhem Von Leibruit .The device was
used to perform arithmetic operations like addition, multiplication, subtraction and division.
JACGUARD LOOM
The machine was invented by French man called Joseph Marie Jacguard.
It was the first machine to store programmes using metal cards punched with holes to determine
the settings for the loom. The loom could be programmed to weave the entire rug in a complicated
pattern.
DIFFERENCE ENGINE
The machine was invented by Professor Charles Gabbage an English man. He proposed a new
calculator that was in many ways the fore –runner of today’s computers. He was the professor of
mathematics at the University of Cambridge; He proposed the construction of a difference engine
that could carry mathematical calculations.
ANALYTICAL ENGINE
This was the engine which combined the concept of mechanized calculation and stored program.
This was also invented by Charles Babbage .He also proposed the possibility of even more capable
device the Steam –Powdered machine that could manipulate and store data.
PROGRAMMED LOOP
The machine was invented by Ada Augusta Byron who collaborated with Charles Babbage on some
of his scientific wittings and came up with a programmed loop. This was the device which could be
programmed to conditionally loop or repeat in order to carry out the sequence of steps that are part
of mathematical calculations.
CENCUS TABULATION MACHINE
This was the machine which used punched cards to store data and tabulate data. The machine was
first proposed by Charles Babbage and Ada Augusta Byron but finally designed by Dr Herman
Holerrith in 1890.
To tabulate means to draw table and fill in it data
THE ELECTRO-MECHANICAL COMPUTERS ERA (1890 - 1946)
Before 1890, Electricity was not used by computers. As Electricity availability was becoming
widespread, it was involved in the use of computational devices. The popular developments of
computers in the Electro- mechanical era include:
i.
Hollerith's tabulating machine (1890)
ii.
Howard Aiken’s Harvard Mark I (1944)
iii.
Program “debugging”
Hollerith's tabulating machine (1890)
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.
The census results were "... finished months ahead of schedule and far under budget".
Howard Aiken’s Harvard Mark I (1944)
While a professor of Physics at Harvard University, Howard Aiken, 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 Aiken
renamed it the Mark I
Computer studies Revised Notes for O level by KH
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Electronic era (1946 - Today) including The Computer Generations
Application of mechanical gears in Computers stopped in the Electro-mechanical era.
Computer evolution since 1946 has been categorized into five generations.
Each generation had a major characteristic development (commonly referred to as Hallmark) and
distinct characteristics in terms of Physical setup, Technology, Software, and Set-backs of the
computers.
COMPUTER GENERATIONS
Def; Computer generation refers to the advancement of computer technologies over a period of
years.
The term generation means the state of improvement in the development of a product.
There are five computer generations;
a. First computer generation.
b. Second computer generation.
c. Third computer generation.
d. Fourth computer generation.
e. Fifth computer generation.
THE FIRST COMPUTER GENERATION,
This was the generation between 1944-1959 (USE OF VACCUM TUBES)
It was characterized by the following key characteristics;
1. Computers were very large, room sized computers.
2. Used thousands of vacuum tubes for internal operation.
3. Had so many wires.
4. They had maintenance problems.
5. They had limited primary memory.
6. Used punched cards and paper tapes for in put and out put was displayed out.
7. They generated a lot of heat.
8. Consumed a lot of power.
9. They were not reliable because of their design which relied on the Radio tubes.
10. Programming was mainly done by machine and assembly language and could solve one problem
at a time.
11. Introduction of the first electronic computers, the electronic Numerical integrator and calculator.
12. Introduction of the IBM 705 in 1955.
NOTE; Vacuum tubes are small light bulb size electronic tubes with glowing filament.
The computers of the first generation included the following;
 AUTOMATIC SEQUENCE CONTROLLED CALCULATOR
This was invented by Howard Aiken of Howard University .It was used only for numerical
calculation.
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ATANSOFF –BERRY Computers (ABC).
This computer utilized the logical operation to perform addition and subtraction. I was invented by
professor John V Antansoff and Cliffold E-Berry.
 Electronic numerical integrator and calculator(ENIAC)
This was developed by J Prosper Eckert and William J Mauchley.It was used to solve defense
programs dilemma.
Computer studies Revised Notes for O level by KH
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 UNIVERSAL AUTOMATIC COMPUTERS (UNIVAC I)
This was the first computer to be used for census bureau and was the first produced computer for
business. It was produced by Maurchley and Eckert.
 ELECTRONIC DISCRETE VARIABLE AUTOMATIC COMPUTER (EDVAC)
This was produced by Mauchley and Eckert .This computer utilized the idea of an electronically
stored program. It was produced in 1947.
THE SECOND GENERATION COMPUTERS 1959-1964(USE OF TRANSISTORS)
The key characteristics of this generation were;
1. Use of transistors for internal operations
2. Introduction of high level programming language e.g Basic and COBOL.
3. Computer became less expensive.
4. Computers gave less heat.
5. Processing speed increased.
6. Computers were small.
7. Computers became more reliable.
8. Introduction of super computers e.g. Livermore Automatic research computer (LARC).
9. Introduction of first translator based computer the model 1401 in 1959.
10. Computer used less power.
11. Computers consumed less power as compared to the first generation.
THE THIRD GENERATION COMPUTERS (1964-1971)
(USE OF INTEGRATED CIRCUITS)
The key characteristics of this generation were;
1. Introduction of integrated circuits or IC semi –conductor device conductors with several
transistors built into one physical component.
2. Introduction of operating (OS) e.g. Multics)
3. There was the use of parallel processing.
4. Low cost computers were produced.
5. High reliability computers.
6. IBM Company produced the RPG programming language in 1960.
7. Computers were more smaller
8. Low power consuming computers were produced.
9. Nicholas Wirth developed the Pascal programming language.
THE FOURTH GENERATION COMPUTERS (LARGE SCALE INTEGRATION CIRCUIT (LSIC)
The key characteristics were;
1. Use of large scale integration and very large scale integration circuits (VLIC).
2. Apple Computer Company began selling Apple 1 micro computers.
3. Development of micro processing.
4. Computers became more powerful and cheap.
5. Lap top computers were produced in 1988.
6. Multi - media using sound and video devices appeared in commercial application.
7. The Intel 14004 a special microprocessor was created in 1971.
8. The IBM co-operation begins selling IBM PC in 1981.
9. The computers were relatively small.
10. Computers were more speedy and consumed very little power.
Computer studies Revised Notes for O level by KH
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THE FIFTH GENERATION COMPUTERS
The key characteristics of this generation are;
1 Use of artificial intelligence.
2
Computers based on the use of artificial intelligence (AI) are expected to behave like humans
and engage in discussion with human beings.
3 More users, new multi media, fast connection and virtual
reality services will be in place.
4 Small sized computers are being used today.
5 Computers that use parallel processors are being developed along with new soft ware designs.
6 Computers are so fast.
7 Computer s of today generates less heat and consumes less power.
8 The computers of the fifth generation, internet is expected to be universal like Radio and
television.
9 Reduced instruction set computer technology is being used to develop a very faster computer.
1.3 uses and functions of a computer in our society
o Education
o Research
o Business
o Health
o Communication
o Military/security
o Home
o Entertainment / leisure
a.
GOVERNMENT INSTITUTIONS
Some of the government institutions include finance, planning, education e.tc. Computers are used
for the following functions;
i.
Keeping government records.
ii.
Improve efficiency within the civil services.
b. EDUCATION AND RESEARCH.
- Computers are used as teaching aids.
- Computers are for long distance learning.
- For research, they are used for accessing reference materials.
C - COMMUNICATION INDUSTRY
o In telecommunication industry computers are used to switch incoming and outgoing calls.
o Railway Corporation, computers are used to co-ordinate the movement of their wagons and
goods.
o In Air line industry. Computers are used for Air traffic control and surveillance of Air space using
Radar equipment as well as for reservation purposes.
o Shipping and cruise liner industries, computers are used to speed up cargo handling and
passenger booking.
D. POLICE AND DEFENCE.
 To keep database of finger prints
 Used in electronic intelligence gathering and military laser guided missile system.
 For base face recognition to analylise the traffic offenders and criminals.
E-HOME AND LEISURE
 Provide people with list of shopping items and electronic money transfer.
 For entertainment
Computer studies Revised Notes for O level by KH
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 For playing games
EMPLOYMENT
Keeping the records of the employees
1.4 Computer care and safety
COMPUTER LABORATORY CARE AND MAINTENANCE
A computer laboratory is a room that is specially designed and prepared to facilitate the installation
of computers and to provide a safe and conducive environment for using the computers.
Factors to consider when preparing a computer laboratory
• Security of computers, programs and other resources
• Reliability of the power source
• The number of computers to be installed and the available floor space
• The maximum number of users that the computer laboratory can accommodate
Why must there be safety rules and precautions in the computer laboratory?
• To avoid accidental injuries to the users
• To avoid damage of computers
• To provide a conducive and safe environment for computer use.
Factors to consider when buying computers
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•
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Needs of the organization/volume of transactions
System specifications like capacity of hard disks, RAM, processor speeds
Costs of system components and development
Source of system components
Environmental concerns
Available employee skills
Computer literacy
Computer literacy refers to having the knowledge and understanding of computers and their uses.
Computer literacy refers to having the basic understanding of what a computer is and how it can be
used as a resource.
Computer laboratory rules and regulations
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Avoid smoking and exposing computers to dust since they contain small abrasive particles that
can damage computer components and cause wearing of moving parts.
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Avoid carrying food and beverages to the computer room since these may fall into moving parts
causing rusting or electrical faults.
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Avoid unnecessary movements because you may accidentally knock down peripheral devices.
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At all times follow the right procedures while starting and shutting down the computer therefore
abrupt switching on and off the computer should be avoided since this can lead to damaging the
computer.
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Do not open up the metallic covers of computers or peripherals without permission and
particularly when the computer power is still on.
Computer studies Revised Notes for O level by KH
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Any repairs to the computer should be done by someone who has knowledge regarding
computer repairs.
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Any connections (keyboard, mouse, printer and monitor) to the computer should be done when
the computer power has been switched off.
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Computers should be regularly serviced and keep a regular record of computer servicing and
repair to establish maintenance costs and common problems to your computer.
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Guard your computer against new users who might spoil the computer and data corruption by
unauthorized parties
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Cover the computers after using them or when not in use. Let the computers cool down before
being covered to avoid trapping heat.
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The computers should be cleaned on a regular basis to remove dust from the keyboard, mouse
and other parts.
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Keep computers away from excessive dust and fit special curtains that would reduce entry of
dust particles and computers should not be exposed to direct sunshine.
Basic requirements for setting up a computer laboratory
UPS- Uninterruptible Power Supply
• If the power goes off, computer equipment must keep running. Even home computers need the
time to shut down properly. Damage to devices and data can occur when there is sudden power
loss or fluctuation.
• UPS, or Uninterruptible Power Supplies, provide power for devices in the event of a failure or other
electrical problems.
• A UPS is essentially a small battery that keeps the power supply on for long enough for you to
switch off the computer safely when there is a sudden blackout.
Air conditioner
• Air conditioning units monitor and maintain the temperature, air distribution and humidity in a
computer room.
• An Air conditioning unit is a device used for cooling and controlling the humidity and purity of the
air circulating in a space.
Computer studies Revised Notes for O level by KH
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Fire extinguisher
• Fire extinguishers are a critical component of saving property and lives in the case of a fire
emergency.
• Owning a fire extinguisher is a form of ensuring safety.
• All computer rooms need it just in case a fire starts.
• It can save our property from burning because the use of the device will help prevent it from
spreading and can even stop the flame in no time.
Security camera
 Security cameras act as a deterrent to theft and other crimes. Cameras monitor data centers or
blind spots outside of doors / Surveillance
 Play back for reference purposes
Blower
Used to blow/remove dust that may have entered inside the computer
• Antiglare screens
Regulate excess light from monitors especially CRT monitors.
Water proof covers
Protect computers from moisture, water and liquids.
Computer studies Revised Notes for O level by KH
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First aid box
A first aid kit is a box or bag that contains the necessary items for providing emergency care. It is
important to have first aid kits, because they allow someone who is injured, to be rapidly treated
with basic first aid, before they can be properly treated at the local hospital.
• Reasons to keep a first aid kit: Prevent infection, Prevent excessive blood loss, prevent scarring,
prevent an acute injury from becoming a chronic problem and Prevent death.
Wool carpet
 The wool carpet is used to trap dust that enters in the computer laboratory.
 Prevent damage of devices when they fall down.
 Trap dust
 Absorb moisture
 Prevent electric shock
Internet gateway
An internet gateway is your modem or router or any other peripheral which allows you to access the
internet.
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Burglar proofing
Burglar proofing provides protection against any forced physical entry into the computer laboratory.
Burglar proofing involves fitting metal grills in windows and doors.
Secure computer laboratory environment
• Protection against fire
Have gaseous fire extinguishers like those filled with carbon dioxide. Water based or powder
extinguishers should be avoided since they can cause damage to computer components.
• Computers should not share the same power line with other office machines to avoid overloading
the power units.
Cable insulation
• All power cables must be properly insulated and laid away from pathways in the room.
• Lay them along the walls in trunks. This prevents electric shock and power disconnections caused
by stumbling on cables.
Stable power supply
Protect computers from being damaged and data loss due to power instabilities by having:
• Uninterruptible power supply (UPS)
• Power s stabilizers maintain power at required voltages
• A surge protector can be used to protect computer equipment against under voltage and over
voltage.
Burglar proofing
• Consider installing security alarms at strategic access points that would alert the security
personnel in case of a break-in.
• Fit strong metallic grills and locks on doors, windows and strengthen the roof incase the roofing is
weak.
• Use Desktop locks, system unit enclosures and laptop locks.
Computer studies Revised Notes for O level by KH
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AIR CIRCULATION
• Have good air circulation in the computer room since users and computers emit heat energy.
• This is possible through having enough ventilation points like windows, installing an air
conditioning system.
• Avoid overcrowding of machines and users.
• All the above prevent suffocation and overheating.
Lighting
A computer laboratory must be well lit with appropriate wall paints to avoid eye strain, headaches,
stress and fatigue and always fit radiation filter screens to reduce light that reaches the eyes
Standard furniture
Have standard furniture so that the tables are wide enough and strong to bear the weight of the
computers and accommodate all peripherals.
The seat for the user must be comfortable and have a straight backrest that allows someone to sit
upright.
Physical security
• Employ security guards to keep watch over data and information centers.
• Apply burglar proof for the computer laboratory by reinforcing weak access points like windows,
doors, roofing with metal grills and strong padlocks.
• Set up alarms to alert you in case of break-ins.
• Use system locks (locked key systems) to make it difficult to access internal components like hard
disks and memory sticks.
• Use cables to lock the equipment to desk, cabinet or floor.
• Electronic locking mechanism with keys, swipe cards, finger print recognition.
• CCTV Cameras to keep watch over computer systems and centers.
Software security measures
• Computers shared by multiple users in a computer center should have security software installed
to limit and block certain activities for example deep freeze.
• Remote administration software should be considered with high number of computers in a
computer center.
• Computer management software to monitor and limit web browsing should be installed for
example K9 web protection.
• Group policy or security software to prevent malicious software from being executed and installed.
• Assigning unique authorized log-in for authentication before granting network access.
Computer studies Revised Notes for O level by KH
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Study questions
• Define the term computer laboratory
• Mention four factors to consider when preparing a computer laboratory.
• Why must there be safety rules and precautions in a computer laboratory? List any three reasons.
• List down two reasons as to why power cables in the computer laboratory need to be properly
insulated.
• Mention two reasons as to why computers need a stable power supply.
• Suggest two ways through which good air circulation can be achieved in a computer laboratory.
• Suggest two reasons why standard furniture must be provided for a computer laboratory.
• Mention five ways through which computers can be kept safe.
• Define the following terms
a) Computer literacy
b) Computer competency
c) Computer professional
Management of computers
Computer management is the process of managing, monitoring and optimizing a computer system
for performance, availability, security or any other operational requirement.
It is broad term that includes manual and automated administrative processes in the operations of a
computer.
Computer management includes various tasks such as:
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Updating or patching a computer’s operating system with the latest updates and fixes
Installing, configuring and executing anti-virus/anti-malware software on a computer to identify,
remove and provide protection against malicious attacks
Managing all components on the computer in relation to drivers, permissions and basic
functioning
Creating and managing users
Troubleshooting hardware, software or network and Internet errors
Using disk defragmentation and disk cleanup services to remove unnecessary data and improve
disk response
Enabling, disabling and optimizing startup and background applications to increase/maintain
processing speed.
Maintenance of computers
Computer maintenance is the practice of keeping computers in a good state of repair.
Computer cleaning involves physically cleaning the interior and exterior of a computer, including the
removal of dust and debris from cooling fans, power supplies, and other hardware components. This
should be done after certain period of time (weekly/monthly).
A computer needs to be maintained in order to keep working properly and in good shape and
contributes to keeping computer troubles at bay.
Typical computer maintenance tasks include backing up your files, running antivirus software,
installing software updates, using disk tools to keep your hard disk in good shape and physical
cleaning of your equipment.
Computer studies Revised Notes for O level by KH
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 Back Up Your Files
One of the most stressful experiences for a computer user is data loss. Most computers use a hard
disk drive as the primary storage device. Hard disk drives can function for many years, but at some
point, they will crash.
One of the solutions is to create a backup of your files. You can burn a CD or DVD with your most
critical files, copy your files to an external hard disk drive or use an online backup service. Whatever
strategy you use, just make sure you create a backup copy of your files on a regular basis.
 Use Antivirus Software
Computer systems face a number of security threats. The most serious threats consist of viruses.
A computer virus is a computer program that can cause damage to a computer's software,
hardware or data. It is referred to as a 'virus' because it has the capability to replicate itself
and hide inside other computer files.
The best way to deal with the threat of computer viruses is to use antivirus software. Antivirus
software helps to protect a computer system from viruses and other harmful programs.
Antivirus software prevents viruses from getting into your computer system, scans your online
activity to make sure you are not downloading infected files also helps to detect and remove viruses
from your computer system if you get infected.
 Use Disk Tools
Disk tools include a range of different tools to manage hard disk drives and other storage devices.
These are important because a hard disk drive failure can have disastrous consequences, including
losing all your data. Keeping disks running securely and efficiently is an important part of overall
computer maintenance.
Some of the recommended disk tu8ools you should use on a regular basis are disk cleaning and disk
defragmentation.
Computer studies Revised Notes for O level by KH
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 Do not download and install unknown software from Internet. This is the biggest mistake
most of the PC users are doing. Some of this software can damage the Windows registry,
which cause lot of errors.
 Install anti Spyware program to detect Spyware tools.
 Install a Personal Firewall. Most of the antivirus programs are bundled with Personal
Firewalls these days. Personal firewall is a barrier between your PC and the outside world.
This can protect your PC from hackers and Spyware tools.
 Uninstall unnecessary programs installed in your PC.
 Be very careful when you download music from the Internet. Always stick to one trustworthy
web site.
 Delete temporary Internet files.
 Set-up your PC to Download and install “Windows Updates" automatically. Windows updates
include Operating System patches for bugs and PC security related issues. These patches
can reduce many unknown computer problems.
Software update is also called a patch because it's 'patching' the software.
Ethics and integrity in computer use
 Computer ethics refers to a set of moral principles that regulate the use of computers.
 Or the human values and moral conduct relating to right and wrong behavior/decisions made
when using computers.
 Computer integrity refers to steadfast loyalty to a strict moral or principled set of laws regarding
computer use
Some of the Computer ethics and integrity that should be put in mind when using computers
include:
1. Respect the privacy of others. Do not in any way examine or change files or passwords
belonging to others. Do not violate the privacy of individuals or organizations.
2. Respect the integrity of the computing systems. Do not develop or use programs that
invade, damage, or alter computing systems or software. Do not in any way harass other users.
3. Always identify the user accurately. Never use someone else's account. Do not use
fraudulent means to avoid accounting for the use of computing services.
4. Respect copyrights and licenses. To copy a licensed computer program is illegal; it is indeed
theft.
5. Respect the intellectual property of others. Individual programming assignments are
expected to be done by individual students; do not take another's work or ideas to call your
own.
6. Exhibit responsible, sensible use of computer hardware, software, and data.
Computer studies Revised Notes for O level by KH
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1.5 Keyboard and navigation
Keyboard. It’s an input device that converts letters and other characters into electric signals
readable by the processor. It has a type writer area, function keys, cursor movement keys and
numerical keypad. It’s a device which enables a computer user to communicate to the computer
system.
Different keys of the keyboard
a. Type writer area: this comprises of alphabetical letters from A-Z and numerical numbers 0-9.
b. Function keys. These are programmable keys that do specific tasks in a given application
package.
c. Cursor control/arrow keys. These control the movement of the cursor within the screen.
d. Space bar. This moves the cursor one step or position to the right and it is used to provide
space between words or letters.
e. Back space key. This is used to erase any character to the left of the cursor. It also moves any
word or sentence to the right of the cursor.
f. Delete key. This erases any character on the right of the cursor and moves any word or
sentence to the left or towards the cursor.
g. Keyboard status keys. These control the state of the keyboard. They include; shift key, caps
lock, Num lock, Alt key and Ctrl key.
h. The shift key. This enables one to access the character or symbol which appear on top of some
keys. It also opposes the effect of the caps lock.
i. The caps lock. This facilitates the typing of alphabetical letters in upper case or lower case.
j. The Num lock. This enables one to use the numerical keypads.
k. The Enter key. This is used to confirm a given command as instrument for execution purpose.
It also helps to start a new paragraph or sentence.
l. The Alt key. This is used to make a menu ready for selection of items on it.
m. The Page Up key. This is used to move the cursor up by one page
n. The Page Down key. This is used to move the cursor down by one page.
Pointing devices
A pointing device is an input device. It is used to control the movement of the pointer or cursor on
the screen.
Uses of pointing devices
They can be used for:
 Sending command signals to the computer.
 Selecting items on the screen.
 Selecting commands from commands menu.
 Drawing graphs etc.
Most Important Pointing Devices
The most important pointing devices are as follows:
1. Mouse
2. Trackball
3. Pointing Stick
4. Joystick
5. Touch Pad
6. Touch Screen
Computer studies Revised Notes for O level by KH
7. Light Pen
8. Digitizer
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9. /Graphic Tablet
1- Mouse
Mouse is the most commonly used pointing input devise. It is used to control the cursor or pointer on the
screen and to give commands to the computer. It is very easy to use. The mouse is attached with the
computer by a cable or wireless connection.
The top of mouse contains one wheel and 2 or 3 buttons. These buttons can be clicked or double clicked to
perform different tasks.
Example: For example, an object (icon) on the screen is selected by clicking the left button of mouse.
Similarly, a program or folder is opened by double clicking the left button of mouse.
Two Types of Mouse
The most popular types of mouse are as follows:
(i) Mechanical Mouse: It has a small ball at the bottom. The ball rotates as the mouse is rolled over a flat
surface. Usually, a rectangular rubber pad (known as mouse pad) is used as flat surface. As the mouse is
rolled over the flat surface, the pointer moves in the same direction on the screen.
(ii) Optical Mouse: It has no ball at the bottom. It uses the laser technology to detect the mouse movement.
Nowadays, it is commonly used in personal computers (PCs).
Mouse techniques
CLICK: to press and release the left mouse button once
Double click: to press the left mouse button twice quickly
Drag: to move an item by pointing on it and holding down the left mouse button moving it to a new location
and releasing the button.
Right click: to press and release the right mouse button once
2-Trackball
A trackball is a pointing input device. It performs functions like a mouse but it is a stationary device. It has
move-able ball on its top. The ball is rotated or rolled with fingers (or palm of the hand) to move the pointer
on the screen. Like mouse, a trackball also has buttons used to send the commands to computer.
The trackball is usually available laptop compute. It is fixed on its keyboard. It is also available as separate
input device.
3- Touch Pad
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Touch Pad is a pressure-sensitive pointing device. Touch pad is also known as track pad. It is also stationary
device like trackball but it has no moving arts. It is a small, flat surface (or sensitive pad) over which a user
slides fingertip to move the pointer on the screen.
Touch Pad also has one or two buttons. These buttons are located near the pad. These buttons work like
mouse buttons. Touch Pad is normally used with laptops. Nowadays, it is also available as separate input
device. It is fixed on separate keyboard.
4- Pointing Stick
A pointing stick is a pressure-sensitive pointing device. It looks like a pencil eraser. It exists between keys of
keyboard. It is used to control the movement of a pointer on the screen. The pointer in the screen moves in
the direction in which the pointing stick is pushed. Pointing stick input device is normally used with laptop
computers.
5- Joystick
Joystick is a pointing device. It consists of a vertical handle or hand-held stick. The stick is mounted on a base.
The hand-held stick is used to control the movement of pointer on the screen. Joystick also contains one or
two buttons. The button of the joystick is pressed to activate certain event or action. Joystick is basically used
to play video games. It is also used in some computer-aided design (CAD) system.
6- Touch Screen
A touch screen is a special video display screen. Input is given to the computer directly by touching the screen
with user fingertip. Most touch screen computers use sensors in the computer's screen to detect the touch of a
finger. Usually touch screen used to make selection from a menu of choices displayed on the screen. Touch
screen is often used in ATM. Touch screen systems are also used in restaurants, supermarkets, departmental
stores etc.
In some computer systems, pen-based or light pen input devices are used. The user touches the screen with a
pen. However, the term touch screen implies a system that accepts input data by touching the screen with the
user's fingertip.
7- Light Pen
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The light pen is a hand-held pointing input device. It looks like a pen. It is a light-sensitive input device. It is
connected with the computer by a wire. The tip of pen contains a light-sensitive element. This device also
contains a button.
Input is given to the computer directly by touching the screen with pen. When the pen is touched with the
screen, it detects or senses a position on display screen. The user points the object to be selected on the
display screen and then presses a button on the light pen.
Light Pen device is usually used by engineers and graphic designers. This input device requires special
monitor. Light pen is used in Personal Digital Assistant (PDA) and other types of hand-held computers.
8- Digitizer or Graphics Tablet
Digitizer is used for drawing new images or tracing old images. Usually, it is used for
making maps and engineering drawings. A digitizer is also known as graphics tablet. It
consists of a flat, rectangular board (or pad) and an input device stylus or puck. Each
location on the rectangular board points to corresponding position on the computer
screen. The stylus or puck is connected to the board / pad by a wire.
SENIOR ONE
TERM: TWO
1.7. CATEGORIES / CLASSIFICATION OF COMPUTERS
Computers are broadly classified into the following:
Classification by capacity/size
Classification by power
Classification by purpose
Classification by function
CLASSIFICATION BY CAPACITY
This is the classification of computers in which we look at the physical size of a computer (its volume) and the
number of people the computer can accommodate at a time.
Computers under this category include the following;
 Main frame computers
 Mini computers
 Micro computers
 Super computers/Monster.
Main Frame Computers
 They were very large almost to fill the whole room.
 They were water or air cooled computers.
 They were very expensive.
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



It could accommodate up to 1000 people at ago.
They were the earliest computers which were around up to 1960’s.
Main frame computers have several powerful processors.
Mainframe computers can process large amounts of data quickly.
 The examples of the main frame computers are; IBM 4381, ICL39 series and CDC Cyber series.
 Mini computers
 They were the small versions of the main frame.
 They were less powerful in operation than the main frame computers.
 They have fewer processors and they can support up to 100 users at ago.
 They can be- used in banking institutions, education establishments and developed areas.
 They are also protected from external environment.
 They have the same basic structures as the larger main frame computers and support the same
peripheral devices supported by the main frame.
 The min computers are heavily used as net work servers in the business industry.
SUPER MICRO COMPUTERS/MONSTER
This is the heavy powerful computer which can support up to 4 users at a time.

They are computers with a high mathematical capability
 Large computers with fast processing using multiple processors and superior technology hence can process
trillion of instructions per second.
 Super computers are mainly used for research purposes, aeroplane design ,oil exploration ,weather fore
casting, for space calculation and other activities that cannot be handled by the main frames and less
powerful machines.
 They are the biggest computers and most expensive than any other computer we have.
 It is used in entertainment industry for animation.
Examples are CRY T3D and NEC 500.
THE MICRO COMPUTERS
These computers have the following characteristics;
i.
These are smaller computers that serve a single user at ago .
ii.
They are mainly used in homes ,offices, and are commonly referred to as personal computers.(PC’s)
iii.
The heart of the microcomputer is the microprocessor (a single chip containing the arithmetic
and logic units.)
Examples of micro computers are Tower PC’s Desktop computers lap tops, Note books, and personal Digital,
assistant or palm tops.
 Note book computers; This is the smaller version of the laptop computers .It is of a small size and low
weight and easy to carry any where .It can store the same amount of data and having a memory of the
same size as that of the personal computer.
 Personal computer (PC’s) These are also small sized computers, small in size and of less cost .Examples
are the Desk tops and laptops.
 Laptop computers; These are light weight computers with built in monitor, keyboard, hard disk drive,
battery and adapter that can be plugged in the electrical outlet.
 Tower pc’s are those in which the case sits as a ’tower’ often on the floor besides a desk.
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

Personal digital assistants (PDA’s) These are also known as hand held computers or palm tops
,combine personal organization tools (schedule planners ,address book to-do lists)with the ability in some
case to send faxes.
Desk top computers; Are those in which the system unit or the main housing sits on a desk, with key
board in front and monitor often on top.
CLASSIFICATION BY FUNCTION
According to Function, we base on what computers do and how they do it.
We have four classifications of computers by function:
i.
Networked
ii.
Stand-alone
iii.
Real-time Systems
iv.
Integrated Systems
Networked computers
These are computers connected by channels to other computers so that they can
communicate with each other and share resources like data, internet connection,
printers, etc.
Stand-alone computers
This is a computer that operates and does everything independently. Stand-alone computers do not have any
internet connection or a connection to the outside world.
A photocopying machine is a stand-alone device because it does not require a computer, printer, modem, or
other device. A printer, on the other hand, is not a stand-alone device because it requires a computer to feed
it data.
Real-time systems
These are systems that respond to an event that has occurred within a certain specified time frame.
Real-time means that after an event has occurred, a system or application has to react to that event within a
certain time period or deadline. For example, computers for a banking system are real time systems.
Integrated system
An integrated system is a group of interconnected units that form a functioning computer system.
An integrated system has separate programs that perform separate functions but they all contribute to the
same output.
CLASSIFICATION BY PURPOSE
In this classification, computers are classified according to what they were designed to do. Some are designed
to perform general duties while others do specific duties. These include;
i.
Special purpose computers.
ii.
General purpose computers.
Special purpose computer
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These are the computers which are designed to perform specific tasks or a particular specific purpose.
They are found in scientific laboratories where they perform complicated mathematical operations.
Examples of such computers are;
a. Missiles
b. Pocket calculators
c. Building lifts.
They perform a specific number of functions.
General purpose computers
These are the computers which are designed to a wide variety of operations using a wide variety of
programming languages .Such computers are found in Universities where different types of programmes are
written.
Examples of such programmers are;
a. Registration by staff.
b. Research by professors.
c. Class assignments.
CLASSIFICATION BY POWER
This is the classification of computers according to the processor power.
Examples of such computers are;
386 processor running at less than 33 MGz speed ,486 processor with speed ranging between 33-66 MHz
,Pentium I,II,III and IV the speed ranges between 77 MGz 2.5 GHz and above.
The most common types of processor power are:- 80286, 80386, Pentium I, II, III, IV
CATEGORIES OF COMPUTERS
Computers can be categorized according to the process they use to represent data. People communicate
through speech by combining words into sentences. Human speech is analog because it uses continuous
(wave form) signals that vary in strength and quality. Most computers are digital.
Computer categories are basically three:
1.
Digital computers
2.
Analog computers
3.
Hybrid computers
Analog computers
An Analog Computer is a computing device that uses continuously changing values to represent information. It
generally deals with physical variables such as temperature, weight, voltage, pressure, speed, etc.
The results given by the analog computers are approximate since they deal with quantities that vary
continuously. Almost all of the measuring devices are “Analog computers”.
Examples of Analog computers




Thermometers,
Voltmeters, and Ammeters
Speedometers, Barometers
Traditional automatic watches
Digital Computers
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These are computers that use discrete (discontinuous) values, i.e. binary digits (0, 1) to represent data. The
binary digits simply mean the presence or absence of an electric pulse/ voltage.
The state of being on is represented by 1 and off is represented by 0.
Although digital representations are discrete, the information represented can be either discontinuous, such as
numbers, and letters, or continuous, such as sounds, images, and other measurements of continuous systems.
Digital computers are more accurate and work at a very fast rate.
Examples of Digital Computers Include:



All Personal computers (PCs)
Laptops,
Digital Watches
Hybrid Computers
A hybrid computer combines the desirable features of analog and digital computers. A hybrid computer
accepts analog signals and converts them to digital for processing.
It is mostly used for automatic operations of complicated physical processes and machines.
Now-a-days analog-to-digital and digital-to-analog converters are used for transforming the data into suitable
form for either type of computation. Hybrid computers are mainly used for specialized tasks.
Examples of Hybrid computers
Digital petrol pumps are an example of hybrid computers. They measure physical quantities and represent its
values in digital form.
In Hospitals’ Intensive care units, analog devices measure the patients temperature, blood pressure and other
vital signs.
These measurements which are in analog are then converted into numbers and supplied to digital components
in the system.
1.8. The computer system
A computer system is the set of interrelated elements working together in an integrated way to achieve a set
objective.
The four main components of a computer system are;
Computer hardware; This refers to the physical or tangible parts of a computer.
Computer software; These are instructions or programs a computer must follow to accomplish a given task.
Human ware or live ware; This is the user or a person who operates the computer.
Data and information have been defined above.
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Data refers to raw facts and figures that are entered into the computer for processing. OR Data is anything in
a form suitable for input into a computer for processing.
Data can also be grouped into two:


Unprocessed data Like Letters, digits and symbols (e.g., a, b, c, &, ...), Musical notes, etc.
Processed data (Information) Like a words (e.g boy), a mathematical formula, grades, a piece of music, a
song etc.
Information communication technology (ICT)
ICT means the scientific means of sending and receiving information using the scientific means e.g.
computers, networks, internet, e.t.c which requires understanding and feed back.
ICT brings together technologies used in the collection, storage, processing of data, and in the transmission
and retrieve of information, together with associated methods and applications.
TYPES OF INFORMATION SYSTEMS
The two forms are;
a. Manual information system.
b. Computerized information system.
Data processing is the same whether manually or by the use of a computer.
Computers use programs instead of instruction books and they store data on disks and tapes instead of filling
cabinets but their work still follows ,the input ,processing, output and storage pattern.
When compared with human beings;
a. Computers can process data more quickly.
b. Are generally accurate (where as human beings are prone to errors).
c. Can process both larger volumes of data and more complex data.
d. Store larger volumes of data.
e. Share information at a very high speed with other computers using networks.
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However manual or human data processing is more suitable when judgment is involved in the work
(remember computers don’t think though it is said we are entering or we have rather entered the fifth
generation of computers where computers will behave as if they think by using the Artificial intelligence (AI
technology).
ADVANTAGES OF USING COMPUTERS
Speed; A computer is speedy as it can take Millions of instructions per second.
Storage; a computer can store data and information for along period of time and safely.
Versatile; Computers are versatile as they can do different things at the same time.
Flexible; Computers are flexible as they can do other works of other machines like phones, radio, fax e.t.c.
Recreation; Computers offer recreational facilities like games, sports, movies e.t.c.
Accurate; Computers are very accurate but their accuracy depends on the users degree of accuracy .That is
why we have the saying GIGO (Garbage in Garbage out)
Diligence; Modern computers can work for so long hours without getting bored or tired.
Volume and complexity; Computers are capable of handling big volumes of data and complex materials.
Access to information; The use of data base and the ability to link a number of users via some form of
network improves the distribution of information within and beyond the organization.
Interactive; A computer is interactive, it can respond to instructions given to it.
Communicative; A computer can communicate with one another through net work and Internet.
a. Computers are convenient to use.
b. Computers produce neat work.
c. Computer is programmable.
d. Computers are economical.
e. Computers can automate work.
DISADVANTAGES OF USING COMPUTERS
Un employment; Computer lead to un employment by taking most of the work that humans would have
done
Cost; Initial cost of computers is high and maintenance is rather expensive.
Fatigue; Computers cause fatigue as the result of spending a lot time using them.
Delicate; Computers are delicate thus have to be handled with care.
Viruses; Computers are affected by computer viruses that undermine their operation and credibility.
Piracy; Piracy means accessing the computer system illegally for the purpose of stealing the documents
(information) or soft ware .This is another computer crime.
Hackers; This means the process of accessing the computer illegally but with no intention of stealing the
documents e.g playing games.
Eye defect; Due to direct light the eyes may be spoilt. Use screen protective.
Pornography; This refers to showing naked people or sexual acts in order to cause sexual excitement.
SENIOR ONE
TERM: THREE
TOPIC 2: COMPUTER HARDWARE
It’s a general term used to describe all the various physical or tangible parts of a computer like monitor,
printer, keyboard etc.
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2.1 Components of computer hardware
 Input devices/ units
 Output devices
 Storage devices (primary and secondary storage
Secondary storage “optical, magnetic and optical-magneto”
 Processing unit
2.2. Application of hardware components
Input Devices
These are devices that feed the computer with data and information. They include; a keyboard, scanner,
mouse, digital cameras, joy stick, smart cards, credit card, automated Teller Machine card (ATM card), light
pen, magnetic ink character reader(MICR), optical mark reader (OCR), bar code readers, optical character
readers, touch screen, digitizer among others.
Keyboard. It’s an input device that converts letters and other characters into electric signals readable by the
processor. It has a type writer area, function keys, cursor movement keys and numerical keypad. It’s a device
which enables a computer user to communicate to the computer system.
Mouse. This is a hand held pointing device which is used to point, select, move and draw object in the
computer screen. Examples of mice include: codeless, touch pad (touch tone pad), mouse stick.
Scanner. This is advice that is used to read graphical data or information into a computer e.g. logos,
emblems, photos, pictures etc. scanners are usually used to capture existing documents in an electronic form
for further processing or incorporating into other documents. Text and graphics can be scanned and images
can be manipulated by changing the colors, the sharpness and contrast etc.
Types of scanners
o Hand scanners. These are used in scanning small objects e.g. logos, signatures, emblems, budges, thumb
prints etc.
o Flat bed scanner. These are heavy scanners which are used for scanning commercial photos and pictures.
Credit card. It’s a small plastic card that allows its holder to buy goods and services on credit and to pay at
fixed intervals. It has a strip of magnetic tape fixed on it containing coded information which is usually the
owner’s code. The card is inserted into a slot where magnetic data may be picked. Details of the transaction
are then recorded against the credit card number and the owner’s account is credited with the transaction.
Bar code reader. Most items manufactured are labeled with a Universal Product Code (UPC), identifying the
items .the label code is in terms of bars with coded spacing and thickness. These bars contain information in
code that a computer can interpret. Most supermarkets today use this system and the codes can be seen on
every item on stock. This enables fast pricing, identification and accurate stock tracking/taking. A bar code
reader is a device used to read these codes and send request to central computer on which the database of
the organization is stored, the central computer sends a response about the product details i.e. its price,
name, manufactured date etc.
Optical mark reader. This is a device which can detect the presence or absence of a mark on a paper. Light
is shown onto the paper and the reflected light is detected. This device is used for reading answers to
questions in an exam or survey.
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The magnetic ink character reader. This is used to read characters written using magnetic ink. They are
used in banks to read cheques and at points of sales in shops.
The voice recognition device. This is used to recognize words from a person and follow the instructions. An
example of its use is in a computer which opens money safe, if the correct password is said.
The joystick. It’s a device connected to a terminal with a control level that can be moved or titled in various
directions for moving the cursor to any position on the screen. It’s commonly used in computer graphics and in
playing games.
A light pen. It consists of a stylus connected by a cable to the terminal that can sense the light from a
position on the screen and convert it into an electrical signal transmitted to the computer. It can be used to
move or delete images on the screen or to create new images.
Touch screen. With touch screen, users of computers just have to point on a particular item they want to
select from the screen using their fingers. When a particular part is touched, the screen can sense that part
and the item in that area will be selected.
Digital cameras. These take photographs like normal cameras do. The only difference is that digital cameras
do not create an image on a film like ordinary cameras but instead the image is stored on the camera and
after downloaded onto a computer for editing and printing.
Output Devices
These are components which bring out the information to the user’s disposal. They include:
Monitor / Visual Display Unit (VDU)
Printers
The loud speakers
Plotters
projectors
The communication channel-links the computer through telephone lines
The monitor. This is a device which shows/gives the soft copy of the data/information in the computer.
Monitors are either based on a cathode-ray tube (CRT) or LCD (liquid crystal Display)
Advantages of CRT monitors over LCD
 CRT monitos have wider view angle than the LCDs
 CRT monitors are resistant to harsh conditions like dusty conditions
 CRT monitors are cheaper than LCDs
 CRTs have a very fast response time
 CRTs are not affected by the problem of dead pixels as images are painted on the screen
 Etc
Disadvantages of CRT over LCDs
- CRTs consume a lot of power than LCDs
- They consume a lot of space i.e. they are big in size
- They are not portable
Advantages of LCDs over CRTs
- They use less power than CRTs
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- They are portable
- They emit less radiations than CRTs
Disadvantages of LCDs over CRTs
- LCDs have a small view angle than the CRTs
- LCD monitors are not resistant to harsh conditions like dusty conditions
- LCD monitors are expensive than CRTs
- LCDs are affected by the problem of dead pixels as images are painted on the screen etc.
NOTE: Resolution refers to the number of distinct tiny points visible in the screen known as pixels (picture
element). The higher the number of pixels used the better the clarity of the image formed.
-
Display scrren’s resolution refers to the clarity of the image and it is directly related to the number of pixels
used to create the image. The hogher the number of pixels used the higher the resolution.
The monochrone: this is the single colour monitor. It is like the black and white TV
The polychrome monitor: this is the coloured monitor. It is like a coloured TV.
Printers. These are devices which gives a hard copy of the soft copy of the data or information held in the
computer.
Printers are output devices that produce text and graphics on paper. They are connected by a cable to a PC
through a special socket on the computer referred to as a printer port.
Types of printers:
They are basically two types of printers i.e. impact and non-impact printers.
Impact printers are the ones which print by physically striking their print heads on the printing media like
paper, cloth etc. e.g. Dot matrix which print using a set of pins on a print head, Daisy wheel which print using
a wheel of characters etc. Their print heads press the paper with the ribbon to produce the printout.
Non-impact printers are the ones which print by not physically striking their print heads on the printing
media like paper, cloth etc They use chemicals, laser or heat to produce the image. They give out high quality
printouts. E.g. laser jet which uses toner contained in toner cartridges and ink jet which uses ink contained in
ink cartridges.
Advantages of daisy wheel
 Can print letter quality characters
Disadvantages
 Their speed is very slow
 They cant print graphics
Advantages of dot matrix printers
 They can withstand dusty environment, vibrations and extreme temperature.
 They can print on continuous paper or multipart documents.
 They are the only printers which can use stencils.
 They are relatively cheaper.
Disadvantages
 They are generally noisy because of the striking mechanism.
 Print quality of Dot-matrix is not as good as those from ink-jet printers and laser printers.
 They are relatively slow.
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 They are not readily available on the market.
 They are not easily serviced because they are based on old technology.
 The color print is limited to two i.e. black and red.
Advantages of impact printers
 The cost of impact printers is low.
 More tolerant to a variety of print media (paper types)
 Less sensitive to environmental conditions can print in hostile environments.
Disadvantages
 Poor quality print
 Lack of flexibility and performance with respect to complex fonts, images and color
Non-impact printers are quiet. These are printers that use chemical lasers to form images that eventually
become characters. They form characters and graphics on a piece of a paper without actually striking the
paper e.g. LaserJet printers.
They use chemicals, laser or heat to produce the image. They give out high quality printouts. E.g. laser jet
which uses toner contained in toner cartridges and ink jet which uses ink contained in ink cartridges.
Advantages of laser jet printers
 They produce a very high quality output.
 Are very quiet and very fast
 They are capable of producing color prints
 Their maintenance cost is also low as toner takes long to get finished
Disadvantages
They are expensive to acquire
The toner they use is hazardous to human life.
Advantages of Ink-jet printers
o Color ink-jet printers are cheaper to buy than color laserjet printers
o They are generally quiet and not noisy like the Dot-matrix.
o Can produce high quality color output
o They are also cheap as compared to the laser printers
Disadvantages
o They have a low printing speed compared to the laserjet printers.
o They also require specialized paper to produce high quality color output.
o They are expensive to maintain.
Storage devices (MEMORY)
These are devices that are used in computers to store data. Computer memory can be divided into three:
 Secondary storage devices
 Primary storage devices (also called main memory $ cache)
 Read only memory (ROM)
Secondary storage devices or auxiliary storage devices are devices used to store information/data
permanently even when power is switched off (its non-volatile)
Examples
Hard disks, Floppy diskettes, Compact disks, Digital versatile disks, Flash disks, Memory cards Etc
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Types of secondary storage devices
1. Magnetic secondary storage devices
2. Solid state secondary storage devices
3. Optical secondary storage devices
MAGNETIC SECONDARY STORAGE DEVICES
Magnetic tape: is a storage medium that consists of a thin tape with a coating of a fine magnetic material
used for recording digital data.
Magnetic tapes generally transfer data a bit slower than hard drives, however magnetic tapes are cheaper and
are more durable.
Floppy diskette: is secondary storage medium that can be used to store data in a permanent manner. It
stores data in form of tracks and sectors.
But inserting a floppy disk into system we must use a floppy disk drive. The capacity of the floppy disk is
1.44MB.
Zip disks: is a high capacity floppy disk drive that is slightly larger than a normal floppy disk. They can hold
100 or 250 MBs of data, they are durable and good for backing up data
Magnetic hard disk: is the main and usually largest data storage device in a computer. A hard disk is
generally the fastest in all secondary storage devices and has the large data storage capacity.
Advantages of magnetic storage devices
 Inexpensive storage
 There is direct access on any part of a drive
 There is very fast access to data
 Very large amounts of storage space
Disadvantages of magnetic storage devices
 Data can be altered by magnetic fields, dust and mechanical problems
 Gradually lose their charge over time ie there is data loss over time
 Hard disks eventually fail which stops the computer from working.
 Cannot transfer the disk to another computer easily
SOLID STATE SECONDARY STORAGE DEVICE
This is a data storage device based on electronic circuits with no moving parts. Solid state devices use a
special type of memory called flash memory.
Flash memory is a type of electronically Erasable Programmable Read Only memory . flash memory
is non-volatile but data stored in it can be erased or changed.
Examples of solid state storage devices
i.
Memory cards
ii.
Flash disks
iii.
Smart cards
Hard disk. This is a round pancake-shaped permanently sealed metallic magnetic device on which large
amounts of data are stored and always linked or fitted inside a computer.
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Floppy disk. This is small portable plastic disk used to store data or information. It utilizes its magnetic
properties to keep data or information.
Digital Versatile Disks (DVD’s). They look exactly like CD’s except that DVD’s have got very big storage
capacity than CD’s. CD’s have the capacity ranging from 500MB’s to 700MB’s but DVD’s range from 1 GB to 20
GB’s.
Zip drives. These are related to diskettes but they are bigger than diskettes in terms of size and storage
capacity. They have storage capacity ranging from 100 MB to 2 GB’s.
Compact Disks (D’s) /Optical disks. They are categorized into
 Compact Disk Read Only Memory (CD-ROM). With these disks, you just read what is there but you
cannot erase or write on them.
 Compact Disk Recordable (CD-R). This type can be written to but only once. This means that once you
write on this disk, you can’t erase to write new information or make changes to the existing one.
 CD Re-writable (CD-W). These disks can be written to as many times as you want. This means that
after writing on this type of disk, you can erase that data and write on it again.
Punched card. It’s a rectangular card used to store data by the presence or absence of small holes that can
be punched in specific locations on the card. These cards were used with first computers before disks were
invented.
Precautions measures taken in keeping diskettes
 Do not fold, spindle or mutilate a disk.
 Do not place a diskette near a magnetic field such as near a radio speaker, on top of your system unit or
near electric motor etc.
 Do not expose a diskette to direct sunlight for long periods.
 Keep a diskette away from intensive heat.
 Always keep it in its jacket so that the exposed surface is covered.
 Do not drop it on a hard surface e.g. on the floor.
 Do not drop water on the exposed surface of the diskette.
 Do not expose it on X-ray.
 Do not insert or remove it from its drive when the drive active light is on.
 Do not force it into its drive. It should slip in with little or no resistance.
 Do not write labels directly on it. Use a felt pen.
Differences between hard disk and floppy disk
Hard disk
floppy disk
 Stores more information
stores less information
 Metallic
plastic
 Fixed
flexible
 Reads information faster
it is slow
 Exposed to less risks
exposed to more risks
The primary memory. This is a type of memory that stores data and instructions only when the computer is
working. It’s a temporary type of memory that can lose its contents when power to the computer system is
turned off (volatile memory)
There are two types of primary storage:
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

Random Access Memory (RAM)
Cache memory
RAM Random Access Memory (the main memory of the computer)
This is the working memory and main memory of the computer that temporarily store data and programs that
are being accessed by the computer.
The data and programs that are stored on RAM are volatile i.e. it be lost in case power in the machine is
switched off.
Types of RAM:
 Static RAM (SRAM)
 Dynamic RAM (DRAM)
SRAM Static RAM uses a completely different technology. S-RAM retains stored information only as long as the
power supply is on. Static RAM’s are costlier and consume more power. They have higher speed than D-RAMs.
It’s a form of RAM that is more expensive to produce, but is generally faster and requires less power than
DRAM and, in modern computers, is often used as cache memory for the CPU.
DRAM. This is a form RAM which stores information for a very short time even when the power supply is on.
X-tics of RAM
 Its volatile
 RAM is read and write memory
 It can be upgraded i.e. increased in size
 Stores data and instructions temporarily
Cache memory. Cache memory is a small-sized type of volatile computer memory that provides high-speed
data access to a processor and stores frequently used computer programs, applications and data.
It is the fastest memory in a computer, and is typically integrated onto the motherboard and directly
embedded in the processor
Read Only Memory – Non-volatile primary storage
This is another type of memory that holds information which was put there at the time of manufacturing. It
can’t be modified and additions can’t be made. A computer has a set of in-built instructions it has to know
what to do when turned on.
The instructions built into ROM are permanent.
The computer can read or follow instructions in ROM but can’t change them or add to them. That is why the
memory is called Read Only.
It’s a stable memory i.e. it’s not affected by power cut off. An example of ROM memory is the PC’s ROM BIOS
(Basic Input and Output System) chip. This ROM chip contains a set of instructions that the microprocessor
uses when the PC is turned on or reset.
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Basic ROM types:
PROM (Programmable Read only Memory)
PROM is read-only memory that can be modified only once by a user. The user buys a blank PROM and enters
the desired contents using a PROM program. It can be programmed only once and is not erasable.
EPROM(Erasable and Programmable Read Only Memory)
The EPROM can be erased by exposing it to ultra-violet light for a duration of up to 40 minutes. Usually, an
EPROM eraser achieves this function.
EEPROM(Electrically Erasable and Programmable Read Only Memory)
The EEPROM is programmed and erased electrically. It can be erased and reprogrammed about ten thousand
times. Both erasing and programming take about 4 to 10 ms (milli second).
X-tics of ROM
 It keeps data and programs permanently
 Can’t be upgraded
 Its non volatile
 It only allows reading of data
Difference between RAM and ROM
RAM
ROM
1. Volatile, temporally
1.Non Volatile, permanent
2. Contents lost when power goes off
2. Contents remain when power goes off
3. Read and Write
4. Can be increased
5. Not installed at Factory
3. Read Only
4. Cant be Increased
5. Installed at Factory

STORAGE MEASUREMENT ISSUES
1. Bit; this is an equivalent of a single binary digit i.e. either 1 or 0.
2. Byte; this is the smallest unit for measuring computer memory. A byte is equivalent to eight (8) bits i.e.
1 byte = 8bits
3. Character; this refers to any letter, number, symbol or anything that can be typed on a computer’s
screen. A character is equivalent to a byte i.e. 1character = 1 byte = 8 bits
4. Kilobyte; this is approximately equal to a thousand bytes or 1024 bytes i.e. 1 KB = 1000 or 1024 bytes
5. Megabyte; it is approximately equal to one million bytes or 1048576 bytes i.e. 1 MB = 1000 or 1024
Bytes
1 MB = 1,000,000 bytes or 1048576 bytes
6. Gigabyte; it is approximately equal to 1 billion bytes i.e.
1 GB = 1000 or 1024 MB
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1 GB = 1,000,000,000 or 1,073,741,824 bytes
7. Terabyte; it is approximately equal to one trillion bytes i.e.
1 TB = 1,000,000,000,000 bytes.
Examples:
How many bits are in the word “school”?
e.g. 1)
How many bits are in the word “school”?
school
=
6 characters
1 character =
8 bits
6 characters = y
Y x 1 character = 8 bits x 6 characters
1 character
1 character
Y = 8x6
Y= 48 bits
2) How many bytes are in 64 bits?
Let the number of bytes be X
1 byte = 8 bits
X
= 64
X x 8 bits = 1 byte x 64 bits
8bits
8bits
X = 8bytes
3) How many characters are in 1000 bytes?
1 byte = 1 character
1000 bytes = 1000 characters
The number of characters is 1000.
4) Convert 2000 MB into GB
Let the number of GB be y.
1 GB = 1000 MB
Y x 1000GB = 1 GB x 2000MB
1000GB
1000MB
Y=2 GB
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Processing devices/ processor
This is the heart of the computer where the entire processing takes place. It is sometimes referred to as the
brain of the computer. It is the center of activities in the computer hence referred to as Central Processing
Unit.
The microprocessor does the following:
 Carries out commands to make the hardware components perform actions
 Processing data. This involves performing logical instructions such as comparing and performing
mathematical instructions such as adding and subtracting.
A CPU comprises of the following parts;
a. The arithmetic and logic unit (ALU): performs calculations and decisions
b. The control unit: coordinates processing steps
c. The registers (temporary storage): small storage area
The Arithmetic and Logic Unit (ALU):
This is the component in the CPU, which handles all the arithmetic and logic operations of the computer
system. It is actually the calculator of the computer system.
The control unit
This is a component of the CPU which governs all activities within the computer.
It interprets instructions stored in the main memory and gives instructions to relevant parts of the computer
system.
The control unit performs the four steps carried out by the machine cycle within the CPU for each machine
language instruction. The machine cycle has got four steps which include;
 Fetching; this is a stage that involves retrieving an instruction from memory.
 Decoding; this translates the retrieved instruction into a series of computer commands.
 Executing; this executes/manipulates the computer commands
 Storing; this involves sending and writing the results of execution back to memory.
Processing terms
Multitasking, Multithreading, Time-sharing
 Multitasking
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 A processing activity that allows a user to run more than one application at the same time
 Multithreading
 A processing activity that is basically multitasking within a single application
 Time-sharing
 A processing activity that allows more than one person to use a computer system at the same
time
The machine cycle
This is where for every instruction, the control unit repeats a set of four basic steps.
The machine cycle steps
Step 1: Fetching the instruction. The instruction to be executed is obtained from memory.
Step 2: Decoding the instruction. The instruction is translated into commands the computer understand and
sent to the ALU.
Step 3: Executing the instruction. The commands are carried out.
Step 4: Storing results. The results are stored in registers or memory.
The registers
This is the component which stores instructions temporarily in the CPU while awaiting handling by the (ALU).
Communication devices
An electronic hardware device that can send and receive data on the network. They include:
Modem
It stands for modulator demodulator. An electronic device that convert digital signals into analog signals and
analog signals into digital signals.
Network interface card (NIC)
Also referred to as LAN adaptor or LAN card is used in local area network to establish the communication
between the devices (computers, printers etc.) attached on the network.
Bridge
Connects multiple network segments together
It’s an electronic device that connects two similar networks and controls the data flow between them.
Router
An electronic hardware device Directs data packets to a secure path to the final destination
Gateway
It’s an electronic hardware device that can perform logical functions. A gateway is a device or system
(collection of hardware and software) that connects two networks and translates information from one to the
other so that data can be transmitted between two dissimilar networks.
Repeater
A hardware device which is used to join same type of networks to extend the length of the communication
medium. It also simplifies the signals received from one network and sends the amplified signals to another
network.
Switch
Joins multiple computers to the network
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SENIOR TWO
TERM: ONE
TOPIC 3: COMPUTER SOFTWARE
3.1 Introduction to software
Software is the set of computer programs that provide instructions to computer hardware
It’s the software that instructs the hardware on what to do and how to do it.
Software can also be described as a sequence of logical instructions stored in memory that a computer
executes in the processing of data.
Program. This is a series of step-by-step instructions that provide solutions and tell the computer what to do.
They are logical arranged set of programming statement.
Characteristics of software
a) Correctness: the software should meet all the specifications stated by the customer.
b) Usability/learnabiity: the amount of effort or time required to learn how to use the software should be less
c) Reliability: the software product should not fail while processing a task.
d) Efficiency: the software should make effective use of the storage space and execute commands as per the
desired timing requirements.
e) Security. The software should not have negative effects on data it is processing or hardware on which it is
installed.
f) Safety. The software should not be hazardous to the environment and life.
g) Cost. It should be affordable in terms of cost.
h) Maintainability. Maintenance of the software should be easy for any kind of user.
i) Scalability. Software should be easy to upgrade for more functionality (or for more number of users).
j) Interoperability. This is the ability of software to change information with other applications e.g. exporting
MS excel data to ms word.
k) Portability. The ability of software to perform same functions across different environments and platforms,
e.g. same performance on dell, acer and hp computers.
Software is broadly divided into (types of software):
o System software and
o Application software
3.2
System software
System software refers to programs designed to manage the operations of computers and avail computer
resources to the users.
These are programs which control and support all other computer programs and the hardware.
Types of System software:
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



The operating system
Software development tools (programming languages, compilers, interpreters)
The utilities (utility software)
Data communication software
Operating system
These are programs that manage the computer resources. Op supervises and manages the different activities
that take place in the computer like the way the software uses the hardware. The operating system ensures
that the computer operates in a systematic reliable manner.
Types categories of operating system
Single programming operating system e.g. MS-DOS (Microsoft Disk Operating System), CP/M (Control
program for micro computers), XENIX, PC-DOS (Personal computer operating system). This operating system
can run one program at ago.
Multiple programming operating system e.g. UNIX, Zenix, Novel Netware, Ms-windows. This can run a
number of programs at the same time.
categories of operating system
Operating systems can be categorized into four major types:
1) Real-Time operating Systems:
Refers to multitasking operating system that aims at executing real-time applications. A real time application is
an application that responds to certain inputs extremely quickly. Very fast and relatively small operating
systems. Built into a device, not loaded from a disk drive. Used in MP3 players, Medical devices such as
medical diagnostics equipment, life-support systems etc.
2) Single-User/Single-Tasking Operating Systems:
Allows a single user to perform just one task at a time. Take up little space on disk. Run on inexpensive
computers
Examples include; MS-DOS and Palm OS for palm handheld computers.
3) Single-User/Multi-Tasking Operating Systems:
Allows a single user to perform two or more functions at once. Commonly used on personal computers.
Examples include; Microsoft Windows and MAC OS.
4) Multi-User/Multitasking Operating Systems:
Allows multiple users to use programs that are simultaneously running on a single network server.
Here, each user is given a user session on the server. UNIX, Linux are examples.
Maintenance can be easy and it requires a powerful computer.
Functions of operating system
 Hardware management. It enables a computer to communicate with peripheral devices such as a
printer, mouse etc. it controls all the input/output devices and the flow of data or information e.g.
telling the monitor to display the results.
 Software management. It provides a mechanism for initiating processes that include programs such as
Microsoft word and Microsoft Power Point.
 Data management. It manages files stored on a hard disk and other mass storage devices. It also
performs file management tasks like rrenaming and deleting.
 It provides memory space to program for execution.
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











Coordinate the flow of data between the various application programs and users.
Provides services for obtaining data.
It helps in multi-programming.
It enables booting a computer.
Sometimes they have in-built system utilities like debuggers and defragmenters which help in the
maintenance of disks.
It helps in mediating between the computer user and the computer system in order to help the user to
interact with the computer hardware to obtain results.
It coordinates all activities in the various parts of the computer.
It alerts the user and reports errors.
It manages resources such as the CPU and memory.
It manages multi-tasking (doing many tasks at once e.g. printing, inputting and processing) and multiprogramming (a technique of having more than one program in the main/ primary storage which
programs may be running/ are being processed at the same time). For example, having a word
document and excel spreadsheet open at the same time.
Ensures automatic update of time and date on the computer
It determines the interface of the desktop. Some operating systems are command based and thus
require one to type in commands (e.g. DOS) while others use graphics / pictures (e.g. windows XP)
Controlling system security by maintaining the use of passwords. A password is a set of system before
further access is permitted.
Programming Languages: These are coded instructions which are used when designing computer
programs. Programming languages provide a medium used to write instructions that command computer
hardware to perform particular tasks.
These languages are grouped into two major categories:
 Low level languages (L.L.L)
 High level languages (H.L.L)
LOW LEVEL:
These are the languages, which the computer can understand. They are machine dependant and are very
difficult for the programmer to understand. Examples include:
The machine language: this is written in the binary code i.e. the digits 0s and 1s are used. It is also
referred to as the first generation languages.
The Assembly Language: This language use letters to represent a group of words instead of presenting a
binary operation instruction to the computer as a set of ones and zeros. They use more English-like
instructions “ADD”. Each assembly language instruction is eventually translated into one machine language
instruction. The computerized translation program is referred to as an assembler.
The plan language.
High Level Languages: these are the languages which the programmer can easily understand. The
computer can not immediately understand these languages. In these languages, instructions are used like
wards and phrases and they are translated into a low-level language for computer to easily understand. High
level languages are now referred to as third-generation languages.
Examples include;
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BASIC: In full: beginners all-purpose symbolic instruction code. This is used for training computer
programmers.
COBOL: in full: Common business Orientated Language. This is an internationally accepted high level
programming language used for general commercial purposes.
FORTRAN: In full: Formula Translation. It’s a high level procedure orientated programming language used for
mathematical and engineering purposes.
ALGOL In full: Algorithmic language. It’s a high level procedure oriented programming language used for
mathematical purposes.
PASCAL: This was named after pascal the mathematician. It’s used for fast execution of mathematical
problems.
C language: This is a high level problem oriented programming language used for software development in a
UNIX environment.
C++ language, LISP, APL, PROLOG, DBASE IV language etc
Types of program Translator
 Assembler: this is a program for converting assembly language into machine code.
 Compiler: This computer program that translates a program or code written in a high level language into a
low level language, usually machine language.
 Interpreter. A programming language processor that translates a program line by line (statement by
statement) and carries out the specified actions in sequence.
Software Development Tools
These are system programs that assist in the preparation of a program and translate into machine code for
execution. Examples include; language translators, compilers, assemble, editors, debug aids.
Utility software
These are system programs used to support, enhance or expand programs in a computer system. They can
also be defined as software tools that are used to carry out organization and maintenance activities e.g.
deleting of unwanted materials, deleting those programs which cause the computer to work abnormally etc.
They are generally programs which perform tasks related to maintenance in your computer’s health, hardware
and data. They include:
 File viewer, displays and copies the content of a file
 Diagnostic utility. Compiles technical information about computer hardware and certain system software
programs and prepares a report outlining any identified problems.
 Disk scanner. Detects and corrects both physical and logical problems on a hard disk or removable drive,
searches for and removes unwanted files. Physical problem is one with the media such as scratch on the
surface of the disk.
 Logical problem is one with the data such as a corrupted file allocation table (FAT)
 Screen saver. Causes the monitors screen to display a moving image or blank screen if no keyboard or
mouse activity occurs for specified time period.
 Uninstaller. Removes an application as well as any associated entries in the system files.
 Backup up programs. These ones let you protect your files by making copies of them.
 Data recovery programs. These are used to restore data that has been physically damaged or
corrupted.
 Data compression programs. Reduces the size of the file
 Debuggers. These are programs which correct errors in a computer program.
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A bug is an error in a computer program and to debug means to correct errors in a program.
Defragmenters
These are programs, which bring fragments of a file together for storage in one location in the computer
memory.
Disk maintenance
Disk maintenance utilities like Norton disk doctor, scandisk etc. These programs detect errors on a
computer disk and fix them like checking for bad clusters on a hard disk or diskette and marking faulty
ones as bad cluster.
A bug: An error or defect in software or hardware that causes a program to malfunction. Often a bug is
caused by conflicts in software when applications try to run in a wrong or un expected way.
Debugging is the process of locating and fixing or bypassing bug s (errors) in computer program code or
the engineering of a hardware device.
Virus protection programs (Anti-virus programs)
This is anti-virus software which protects your system from viruses. A virus is a piece of computer code or
program that is hidden within an existing program. It overwrites or attaches itself to programs or data and
destroys or corrupts data. A virus interferes with the normal running of a useful computer program.
Anti-virus programs can be used to detect and remove viruses from your system and any other storage media.
Examples of anti-viruses include; central point anti-virus, Mac fee, Norton anti-virus, Avast etc.
Computer viruses
These are computer programs which silently replicate (reproduce) themselves on storage media without the
computer user realizing it.
These programs in many ways act much like a human virus that is why they are referred to as computer
viruses.
When a computer virus begins to replicate (reproduce), it may or may not be designed to cause trouble.
However, some computer viruses are very dangerous because they are designed to damage data.
Types of computer viruses
Sometimes virus hide in different places on the computer and in the process, perform various damages to the
computer. They include; File virus, Boot sector viruses and partition sector viruses.
File virus. This type of virus hides in program files, especially those files which have extension. EXE and COM.
Boot sector viruses. These viruses hide in the boot sector of a disk. This particular sector contains important
information about the disk’s logical setup.
Partition sector viruses. These hide in the primary sector of a hard disk. This area is where programs which
start a computer are stored. When a virus gets to this area, it at times changes the programs it finds there. In
the end, this may cause a computer not to start.
Other viruses include: overwriting viruses, multiple viruses macro viruses, companion viruses etc.
Sources of computer viruses
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Freeware and share. When infected software is installed on computer, it will automatically get infected.
Contaminated diskettes
Computer games especially. Games downloaded from the internet
Updates of software distributed via networks
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Symptoms of computer viruses
Executable files changing size for no obvious reason.
Program taking longer than usual load
Unusual error messages occurring more frequently
Programs and files disappearing mysteriously
Access lights turning on for non referred devices
Computer indicating that storage devices are full when there is still enough space
Ways of keeping computer virus programs out of your computer
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Getting aware of how computer viruses get into your computer for example some viruses are written to
ride along with another computer program. When a computer user inserts a disk into a computer with an
infected program on it, the virus is duplicated in the computer.
If you are aware of how computer viruses are transmitted, you can avoid them by being careful about
which program to use.
Using special virus detection program. These programs analyze every program and every disk that is
inserted into the computer to make sure that it is not caring any virus. If it does have a virus, detection
program can be used to eliminate a found virus from a disk. Example of such programs include Norton
anti-virus tool kit, Dr. Solomon’s anti-virus tool kit etc.
Avoid external disks especially diskettes as they may be carrying a virus. If you have an anti-virus
program, first check your disks before using them.
You have to be careful when downloading programs (freeware, shareware, computer games etc.) from the
internet as some of the programs contain viruses.
Perform a virus scan on your computer at least once a week and also other storage media like your
diskettes, backup tapes etc.
Always remember to update your anti-virus software. Every day, new viruses are created and the
designers of these virus programs first look at the available anti-virus programs so that they can create a
strange virus which can bypass those programs.
Characteristics of system software
Functions of system software
The three major functions of system software are allocating system resources, monitoring system activities,
and disk and file management.
1. Allocating system resources: The system resources are time, memory, input, and output. The time in
the CPU is divided into time slices. The time slices is measured in terms of milliseconds. Based on the priority
of tasks the time slices are assigned. Memory is also managed by operating system. Disk space is the part of
main
memory.
The
data
flow
is
controlled
by
operating
system.
2. Monitoring system activities: The system security and system performance is monitored by system
software. System performance includes response time and CPU utilization. System security is a part of
operating system. Multiple users can’t access without the security code or password.
3. File and disk management: The user needs to save, copy, delete, move and rename the files. The
system software will handle those functions. Disk and file management is the technical task.
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3.3 Application software
These are programs designed to solve specific problems of the user.
Or programs designed to enable a user to accomplish a specific task (s)
Application software is divided into two: i.e. off-shelf and Bespoke (custom-made) software/Tailor
made application software.
Off-shelf application software
These are already made programs bought ‘off-the shelves’ from a software shop or vendor.
It can also be defined as software that is ready-made and available to lots of people. You usually pay a license
fee to use it
Off- shelf application software can further be divided into Horizontal market applications (common
applications you can find on every office computer) and vertical market applications also known as
specialized application programs.
Horizontal market software
These are software tools that are useful to almost any one in any job. These are programs you can find on
almost every computer in every office.
Vertical market (specialized applications)
It consists of programs developed for a specific industry. Examples include Computer Aided Designs (CAD),
Bakery recipes, Bridge analysis, airline ticketing, airplane wing structure, robots swivel control, electronic
testing etc.
Advantages Off-shelf application

It is relatively cheap, especially when compared to custom written software

It is easily available from most computer shops

It will have been thoroughly tested so there won’t be any serious problems or bugs

There will be lots of user support i.e. books, user guides, online help and discussion forums on the
Internet
Lower training costs. If it is a commonly used package, users and I.T. staff may already be familiar
with it, saving on learning time and training costs. Or, there may be pre-existing training materials and
courses that you can leverage.
More functionality. Off-the-shelf software often has more functionality, because the developers try to
meet the requirements of as many users as possible. (There may even be functionality you didn’t realize
you need!)
Upgrades. The vendor will continue to develop the software, so you will likely get upgrades for free or at
a reduced cost, whereas in bespoke software you don’t get anything new unless you pay for it to be built.

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Disadvantages off-shelf include:

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
Limited to perform what they were designed for
Can easily be pirated
Vulnerable to virus
They make you to pay for many applications when you are to use a few.

Compromise. You may have to compromise on your requirements – it is unlikely you will find readymade software that does everything you need it to, exactly how you want it to.
May be overly complicated. The software may include functionality that you don’t need, as it is
trying to meet the different requirements of a number of users. This can make it more difficult to learn
and use.
You are not in control. The vendor’s plans for the future may not always fit with your own. As a
single customer amongst many, you may not be able to get the features you want implemented.

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Examples of application software include;
Microsoft word
Microsoft excel
Microsoft PowerPoint
Microsoft access
Microsoft publisher etc
Categories of application software:
o
Spreadsheets used for organization and analysis of data in tabular form.
o
Word-processors used to produce text documents that are professionally laid out.
o
o
o
o
o
o
o
Presentation software used for creating presentations to show to customers or staff
Databases used for keeping customer records, sales records, appointments system
Desktop publishing packages used for creating leaflets, posters, business cards
Graphics packages for manipulating images that can be used at home, school or a business
Web design application used for creating personal or business web sites
Communication software among others.
Computer-aided design (CAD) is the use of computer systems to assist in the creation, modification,
analysis, or optimization of a design. CAD software is used to increase the productivity of the designer,
improve the quality of design, improve communications through documentation, and to create a
database for manufacturing.
Bespoke (custom-made) software/Tailor made application software.
Bespoke software is written especially for you, to meet your specific business requirements.
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If very specialized software is needed, a company may decide to write or order its own software. This software
is called custom software. This software is developed by computer specialists or programmers. Examples may
include; report making software, loan portfolio software for Cairo bank, programming in D-base dealing in
hotel operations etc.
The advantages of bespoke (custom-made) software are:
Tailored to you. The software is developed and built to meet your specific requirements, ensuring that you
get software that works exactly how you need it to and delivers the results you want.
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More flexible. A bespoke system can evolve over time to match your changing requirements.
No per-user fees. If you own the software, you won’t have to extra per-user fees as your business
grows.
Not tied in. You own the intellectual property, so you are not tied to a specific vendor that could
potentially disappear at any time.
Competitive advantage. As your competitors won’t have the same software, it could give you a
competitive edge. An effective software package can make a company work more efficiently, improve their
performance and have a positive impact on customer satisfaction levels.
The disadvantages are:
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Higher initial costs. It will cost more at the beginning, as you have to pay the development costs.
Takes longer. Depending on the size and complexity of the software, it may take months or even years
to develop.
SENIOR TWO TERM: TWO
Word Processor
Word processor is an application program used to create, edit, format, save and print text document.
Advantages of word processors than ordinary type writers.
 Word processors are quick in producing documents
 They produce documents containing many data types
 Word processors produce better quality documents
 Read and revise a document on screen
 Change the formatting to get the desired visual effect
 Increase productivity by automating
 Produce as many copies as needed
 Save a document and work on it later
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Disadvantages
o Word processors require training to be used.
o They require application software to start using them
o They are only used with computer which eliminates the computer illiterates.
MICROSOFT OFFICE-WORD
Microsoft Word is a software program that is used to produce text documents that are professionally laid out.
-In general Microsoft Word is a Word processor, which generally deals with text production.
MS Word is a window based advanced word processor developed by Microsoft Corporation-incorporating
friendly interface, for the user with an aim or specification of the required format-With simplified procedures.
It comes in Microsoft OFFICE installation CD and versions include OFFICE 97, 2000, 2003 and now 2007 &
2010..
OTHER EXAMPLES OF WORD PROCESSORS
i)
ii)
iii)
iv)
v)
vi)
AmiPro
Word Star
Word Perfect
WORD Pad
Perfect writer
Open office writer
Features of MS Word
 Word wrap. This feature automatically sends a word that does not fit within the margin settings onto the
next line, without the user pressing enter key.
 Find. Allows the user to locate all occurrences of a particular character, word or phrase.
 Replace. Allows the user to substitute existing characters, words or phrases with the new ones.
 Mail merge. This feature is used to create similar letters to be sent to several people. The names and
addresses of each person can be merged with one single main document.
 Spell checker. Allows the user to check spellings of the whole document at one time or to check and even
correct the spelling of individual words as they are typed (auto correct)
 Thesaurus. Suggests alternative words with the same meaning (synonyms) for use in the document.
 Automatic page numbering. Numbers pages automatically in a document.
 Grammar checker. This reports grammatical errors usually by a wavy green line and suggests ways to
correct them.
 Tables. Allows user to organize information into rows and columns.
 Multi-columns. Arranges text into two or more columns that look similar to newspaper or magazine.
 Drop cap. A feature that formats the first letter in paragraph to be droped across two or more lines.
 Clip art. Refers to pre-made images about various subjects used to illustrate concepts in documents.
 Templates. A feature that establish the initial document layouts and formats for various document types.
 Word count. Establishes the number of words, characters, paragraphs etc in a document.
 Header and footer. Used to insert text in the top and bottom margin through the document.
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
Footnotes and endnotes. Features used as references that provide additional information about a word or
phrase within a document.
Difference between footnote and endnote
A term used to describe additional information found at the bottom of a page. Often a footnote will contain
the source of the information, or additional information about the text contained in the document.
Much like a footnote, an endnote is additional information or credits given at the end of the document
instead of at the end of each page.
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Insert and delete. Feature that allows a user to add and remove portions of text while editing document.
Bold, underline, italic. These and other formatting features that allow a user to improve on the appearance
of text.
Cut, copy, paste, insert, delete. These and other editing features enable a user to make changes to the
text in a document.
Getting Started with MS Word 2007
MS Word is a powerful word processor that makes it easy to create basic documents like letters and resumes.
This Tech Help sheet is based on MS Word 2007 and covers the following:
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Workspace overview (menus, toolbars, etc)
Creating new documents and opening existing ones
Moving, cutting, and copying text
Simple formatting
Launching Word and Workspace Overview
To launch MS Word, either double click on the Word icon if it appears on the desktop
or click on the Windows "Start Button" > Programs > Microsoft Office > Microsoft Word.
When you launch MS Word, you'll see something like the screen below. Take a moment to familiarize yourself
with the items indicated on the image.
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The MS Office Button
The MS Office Button is in the top left corner of the window and provides access to open, save, and print
documents.
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
Click on the Microsoft Office Button and then click on the desired option.
Menu options with an arrow have additional choices available in the area to the right.
Quick Access Toolbar
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The Quick Access Toolbar is just to the right of the Office Button.
When the cursor is over a button, the name of the button is displayed.
The options available it when Microsoft Office 2007 is first installed include Save, Undo, and Redo.
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The Ribbon
In Word 2007, the Ribbon is where you'll do most of your formatting and text manipulation, so take some time
to explore it.
The Ribbon consists of 3 types of items.
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Tabs-This is the main level and includes Home, Insert, Page Layout, etc.
Groups-Each tab has several groups that show related items together
Commands-A command is a button in a group or an item in a list.
Some tabs are only available when a particular item is selected. For example, the Picture Tools tab is only
shown when a picture is clicked on.
To use the Ribbon:

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Click on the desired tab.
The commands under each tab are grouped.
The name of the group is at the bottom.
Some groups have a Dialog Box Launcher button which opens the dialog box with more commands.
Creating a New Word Document
When you launch MS Word, a new document is already created for you. However, if you need to create
another new document while working on an existing document, do either of the following:


Office Button: > New; select Blank Document or a template.
Quick Access Toolbar, click the down arrow select new.
If you'd like some random text to work with to learn how to manipulate text, in your blank document, type:
=rand() and press the Enter key. Random text will magically appear!
Opening an Existing Document



Click on the Microsoft Office Button and then click on Open.
Navigate to the location of the desired file.
Choose the name of the file to work with and click on the Open button.
Cutting, copying, and pasting text
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Cutting, copying, and pasting text can be very convenient when you need to rearrange parts of a document.
Instead of re-typing like you would have to do on a computer, you can simply select the text you want to
move, cut it, and paste it in to another part of the document. If you want to use the text in several places in a
document, you can use copy/paste instead of cute/paste. In order to be able to manipulate text, you'll need to
be able to select it.
Selecting Text
There are several ways to select text. Use the one that is most comfortable to you and meets your needs most
efficiently.
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
Drag
selecting
Click where you want to start selecting text, press the left mouse button, drag across the text, then
release the mouse button where you want to end.
Shift-click
Click where you want to start selecting text, hold down the Shift key, move the cursor and then click
where you want to end the selected text.
Clicking
Once to put the cursor next to a letter; Twice (double-click) to select the word; Three times (tripleclick) to select the paragraph
Select
All
To select all the text in the document, Home Tab >Edit Group>Select All OR CTRL+A
Cutting and Pasting Text




Select the text to be moved.
Press Ctrl X OR on the Ribbon, click on the Home tab, then in the Clipboard group, click on the Cut
button.
Click where the selected text is to be moved.
Press Ctrl V OR on the Ribbon, click on the Home tab. In the Clipboard group, click on the Paste
button.
Copying and Pasting Text




Select the text to be copied.
Press Ctrl C OR on the Ribbon, click on the Home tab. In the Clipboard group, click on the Copy
button.
Click where the selected text is to be copied.
Press Ctrl V OR on the Ribbon, click on the Home tab. In the Clipboard group, click on the Paste
button.
Formatting Basics
Formatting refers generally to the appearance of the text in your document. Things like font face, font size
and color, bulleted lists, etc., are all controlled through different formatting tools.
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Selecting Font Size



Select the text to be changed.
On the Ribbon, click on the Home tab.
In the Font group, change the font and font size as desired.
o Note that you can grow and shrink font size or enter an exact number if you know what size
you want to use.
Alignment
In many instances, you'll want to line your text up either to the left, center, or right of the document.
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Select the text to be formatted.
On the Ribbon, click on the Home tab.
In the Paragraph group, click on the appropriate alignment button on the toolbar.
o Left-Text aligns to the left with an uneven edge on the right.
o Center-Text aligns to the center.
o Right-Text aligns to the right.
o Justify-Text aligns with the even edges on the left and right by spacing words across the page.
Creating a Bulleted List
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Click in the line of the text to be bulleted.
On the Ribbon, click on the Home tab.
In the Paragraph group, click on the Bullets button.
The Bullets button is a toggle, which means that if you select a line of text that is already bulleted, clicking on
the Bullets button will un-bullet that line.
Also notice that you can select the numbered Bullet button if you need an ordered list, too!
The Vertical and Horizontal Scroll Bars
The vertical and horizontal scroll bars enable you to move up, down, and across your window simply by
dragging the icon located on the scroll bar.
The vertical scroll bar is located along the right side of the screen.
The horizontal scroll bar is located just above the status bar. To move up and down your document, click and
drag the vertical scroll bar up and down. To move back and forth across your document, click and drag the
horizontal scroll bar back and forth. You won't see a horizontal scroll bar if the width of your document fits on
your screen.
The Status Bar
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The Status bar appears at the very bottom of your window and provides information such as the current page
and the number of words in your document.
You can change what displays on the Status bar by right-clicking on the Status bar and selecting the options
you want from the Customize Status Bar menu.
You click a menu item to select it. You click it again to deselect it. A check mark next to an item means it is
selected.
Understanding Document Views
In Word 2007, you can display your document in one of the five views: Draft, Web Layout, Print Layout, Full
Screen Reading, Outline Layout.
Draft View
Draft view is the most frequently used view. You use Draft view to quickly edit your document.
Web Layout
Web Layout view enables you to see your document as it would appear in a browser such as Internet
Explorer.
Print Layout
The Print Layout view shows the document as it will look when it is printed.
Reading Layout
Reading Layout view formats your screen to make reading your document more comfortable.
Outline View
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Outline view displays the document in outline form. You can display headings without the text. If you
move a heading, the accompanying text moves with it.
You should use Draft view for these lessons. Before moving ahead, make sure you are in Draft view:
1. Click the View tab.
2. Click Draft in the Document Views group. When the Draft option is selected it appears in a contrasting
color.
Click
During the lessons that follow, you will be asked to "click" items and to choose tabs. When asked to click:
1. Point to the item.
2. Press your left mouse button once.
If you are asked to double-click an item:
1. Point to the item.
2. Quickly press your left mouse button twice.
If you are asked to right-click:
1. Point to the item.
2. Press your right mouse button.
If you are asked to choose a tab, click the tab.
Checking the Spelling in a Document
Word has a built-in Spell Checker to check for misspelled words, duplicate words, and irregular capitalization in
documents, parts of documents, and text entry boxes. When Spell Checker finds a misspelled word, you can
replace it with the suggested word, edit the word manually, or skip the word. You can also define a
replacement for the word by adding it to a user word list.

In an open document, locate the Word Ribbon, click on the Review tab.
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In the Proofing group, click on Spelling & Grammar.
 The word in question will be shown in red in the context of the sentence.
 Choose one of the following:
Ignore Once - Don't replace the word.
Ignore All - Don't replace the word and don’t stop if the same problem is encountered again.
Add to Dictionary - Add the word to the dictionary. This is dangerous because it changes the Spelling
Dictionary.
Change - Change the word in red to the selected word in the Suggestions box.
Change All - Change all occurrences of the word in the document to the selected word in the Suggestions
box.
AutoCorrect - Sets the computer to automatically help with spelling. Note-automatic spelling must be turned
on in Options.
 Click on the Close button.

o
o
o
o
o
o
Note that if no words are recognized as being misspelled and no grammar errors are encountered, the window
does not open.
Saving a Document

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Click on the Microsoft Office Button and then click on Save As.
By Default, Word saves the documents to the My Documents folder as a .docx file. You can navigate to a
different location if you want to save the file somewhere else, like on a flash drive.
Click on the Save button.
Printing the Document
In order to print a document, the computer you're using must be connected to a printer. If you're using a
computer at a library or other computer center, ask to make sure there is a printer available before you count
on printing. Some libraries and other computer centers will charge a per-sheet fee for printing, so make sure
you're prepared for that, too.
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Click on the Microsoft Office Button and then choose Print.
Check to make sure the correct printer is chosen
Click on the down arrow in the Printer section and choose a printer.
In the Page Range section, decide which pages to print. (All, the current page, or a range of pages.)
In the Copies section, indicate how many copies. Click on the OK button.
SENIOR TWO
TERM: THREE
Presentation software
A presentation program is a software package used to display information in the form of a slide show.
Examples of presentation software:
 Microsoft PowerPoint
 Adobe Presenter 8
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Apple Keynote,
Apple Keynote
Corel Presentations
Harvard Graphics
Lotus Freelance Graphics
Slide Rocket
SlideWiki
USES OF PRESENTATION SOTF WARE
1. Used for designing and branding.
2. Used for training like in seminars
3. Used for advertising.
4. Used to draw organization charts.
INTRODUCTION TO POWER POINT
PowerPoint is application software used for slide preparation and presentation.
Terms associated with power point
Slide. The place provided to design the presentation where we can type the text and insert the pictures etc to
make them more interactive.
Or a slide is a displayed screen or a page during a presentation.
Slide Layout: This is the outlook of the slide
Or the specific arrangement of text and images on a slide
Design Template: The specific “look” of a slide or group of slides. A design template can be very basic - with
black text on a white background - or it can be very colorful and complex. Typically, PowerPoint presentations
have the same design template for all slides, although it is possible to select a different design template for
each slide. Later, I’ll show you how to select different design templates.
Slide Show: The way a presentation appears when you are presenting it. When you display your slides in a
slide show, the slides typically take up the whole screen.
Slide show is the full screen view of slides
Slide Transition: A slide transition refers to the visual movements as a slide changes from one to another.
Animations: These are visual effects applied to individual items on the slide such as graphics and bullet
points.
FEATURES OF THE PRESENTATION SOFTWARE
 It has got transitions that make the presentation active.
 Slides that can contain any mixture of text, images, video, animations, links and sound.
 Slide master that allows the style (font, font size, background etc) to be set once and then used
throughout the presentation.
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Animation effects that bring your slides to life by allowing various elements on each slide to appear after a
certain amount of time or when a presenter presses a button.
Transitions which show how the slides move one after the other.
Slide notes which allow the presenter to see the current slide and any notes associated with it on his/her
display.
Insert slide feature; This allows the user to insert a slide any where in the presentation either at the
beginning ,middle or at the end
Deletion of inserted slide; This allows the user to erase any information on the inserted slide.
Cut and paste of slides; This can be done to change the position of a slide removing the slide from its own
position to another position .It allows animations and sound manipulation.
Font specification
Spelling checker.
Advantages of presentation software.
 It simplifies work in that a lot of information can be delivered to a large mass of people or audience.
 It eliminates boredom during presentation because of beautiful backgrounds, transitions and
animations.
 Work is well organized because of the way text boxes are organized on each slide.
 It has different slide layouts for a different purpose e.g. slides with charts, slides with outlines etc.
Disadvantages
 It requires trained personnel in order to use it
 It requires a computer in order t use this type of software
 It requires one to have the application software to use this application.
Key points to note for a good presentation
 Use visual aids (photos, chats and other graphics) whenever possible.
 Use simple, direct sentences and avoid using lingo and wordy constructs. This will make the concept
clearer and easier to understand.
 Try to use only one main idea per slide; too many thoughts or ideas on a slide may confuse the
audience.
 Maintain a consistent layout and color scheme to create continuity and cohesiveness.
 Try to limit yourself to a maximum of one minute per slide.
 Use large type and an easy to read font. Do not use all capital letters.
 Use contrasting colors. (Use a light background color for overhead transparencies).
 Be sure to cite all literature where appropriate and be aware of copyright laws.
STARTING UP POWERPOINT 2007
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
Click on the Start button, located in the lower left corner of the Windows task bar.
Point to All programs, click Microsoft Office.
Select Microsoft Office PowerPoint 2007.
PowerPoint 2007 will open displaying a blank the new PowerPoint environment slide.
SOME PARTS OF MS POWERPOINT 2007
Quick Access Tool Bar: Quick Access Toolbar is located to the right of the Microsoft Office Button. By
default the Quick Access Tool Bar displays the Save, Undo, and Repeat buttons and is used for easy access to
frequently used commands
Title Bar: A horizontal bar at the top of an active document. This bar displays the name of the presentation
and application. At the right end of the Title Bar, as in previous versions is the Minimize, Restore and Close
buttons.
Ribbon: is located in the upper-left corner of the window. The Ribbon exposes most of the feature that use to
be hidden in File Menus. The Ribbon makes it easier to see and find commands to format your document.
Tip: The Ribbon can be reduced to a single line of tabs by pressing CTRL + F1.
Microsoft Office Button: A button that provides access to menu commands in. Here is where you will find
commonly known features such as New, Open, Save, Print and Recent Documents.
Tab: An area on the Ribbon that contains buttons organized in groups. The default tabs are Home, Insert,
Design, Animations, Slide Show, Review and View.
Slide Pane: Workspace to create, edit or format, slides. View Toolbar: A toolbar that enables, adjusts, and
displays different views of a presentation’s content.
Notes Pane: Here you type notes that apply to slide. You can print your notes and refer to them when you
give your presentation or handout to your audience.
Status Bar: A horizontal bar at the bottom of an active window that gives details about the active
presentation
Slides and Outline Tab Pane:
Slide tab allows you to view slides thumbnail-sized making it easy for you to navigate through your
presentation and to see the effects of any design changes.
You can also easily rearrange, add, or delete slides here.
Outline tab is where you can start writing content, Capture ideas, plan how to present them, and move slides
and text around. The Outline tab shows your slide text in outline form. Slide Pane: Status Bar: Notes Pane
View Toolbar:
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The Home tab: is organized in six groups mainly related to slide layout and formatting: Clipboard, Slides,
Font, Paragraph, Drawing, and Editing. For example, the Home tab will allow you to quickly create a new slide
Choose a layout, add and format text and shapes
The Insert tab: is organized in five groups: Tables, Illustrations, Links, Text, and Media Clips. Here you find
all objects you would include with your slides, such as, tables, text boxes, pictures, sounds, diagrams,
hyperlinks, charts, headers and footers
The Design tab: is organized in three groups: Page Setup, Themes, and Background.
The Themes group command allows you to completely change the look of your presentation. This includes the
Colors, Background, Fonts.
The Animations tab: is organized in three groups: Preview, Animations, and Transition to this Slide. Here is
where you find the tools to set the animating effects to your presentations and slide transitions.
The Slide Show tab: is organized in three groups: Start Slide Show, Setup, and Monitors. Here is where you
prepare you presentation, add narration, choose which slide to start with and set up the view when multiple
monitors are involved.
The Review tab: is organized in three groups: Proofing, Comments, and Protect. Here is where you will find
your spelling and grammar checker, in addition to this when you have someone review your presentation this
is where comments can be added and addressed.
The View tab: is organized into six groups: Presentation Views like
Normal view: This is the main working window in the power point.
Slide sorter view: is the window in power point that displays thumb nail version of all your slides arranged in
horizontal row.
Slide show view takes up the full computer screen, like an actual slide show presentation. In this full-screen
view, you see your presentation the way your audience will, Show/Hide, Zoom, Color / Grayscale, Window,
and Macros. Here you can change the display of your presentations, make a quick switch to Notes Page view,
turn on gridlines, or arrange all your open presentations in the window. Live Preview Temporarily applies
formatting on select text or objects whenever a formatting command is hovered. This allows you to quickly see
how the formatting options will look in place before they are made. Live Preview
CREATING A NEW PRESENTATION
1. Click Microsoft Office Button
2. Click New, New presentation screen appears
3. Double-Click on Blank Presentation
OPENING AN EXISTING PRESENTATION
1. Click the Microsoft Office Button.
2. Click Open.
3. In the Open dialogue box, navigate to the open, and then double-click the file.
CREATING A NEW SLIDE
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1. On the Home tab, in the Slides group, click New Slide.
CHOOSING A LAYOUT FOR A NEW SLIDE
1. From the Outline and Slides tab Pane, click on the slide you are selecting a new layout for.
2. On the Home tab, in the Slides group, click Layout.
3. Click Layout Style of your choice.
ADDING TEXT TO A SLIDE
Slide layouts contain placeholders. The dotted border represents placeholders; just click inside the border and
you can add text or insert objects. The slide’s layout will determine the position and size of placeholders.
1. Click inside a text placeholder.
2. Type or Paste the Text or object.
Note - If your text exceeds the size of the placeholder, PowerPoint reduces the font size and line spacing
incrementally as you type, to make the text fit.
DELETING A SLIDE
1. Right-click the slide that you want to delete.
2. Click Delete Slide.
SELECTING A THEME FOR YOUR PRESENTATION
On the Design tab, in the Themes group, click the document theme that you want, or click more to
see all available document themes.
TIP - You can apply a theme to all slides at any given point in time. Whenever you feel like changing
the theme, you can.
INSERTING OBJECTS INTO YOUR PRESENTATIONS / INSERTING PICTURES TO YOUR
PRESENTATION
1. From Insert Tab, in Illustrations Group, click Picture.
2. Double-Click Folder where picture is stored
3. Double-Click on picture you want to insert
INSERTING CLIP ART INTO YOUR PRESENTATION
1. From Insert Tab, in Illustrations Group, click Clip Art.
2. Search field will appear. Enter keyword in Search for field.
3. Click Go.
4. Results appear, click on image you choose then drag image into your open slide.
Note - Once Picture or Clip Art is inserted, if you want to resize it or give it special effects. Click on the
image and the Picture Tools appear on the Ribbon. Click the Format tab, and use buttons and options
there to work with the picture.
INSERTING SHAPES INTO YOUR PRESENTATION
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1. Home tab, in the Drawing group, click Shapes. Or from the Insert tab, click Shapes.
2. After selecting the desired shape, drag your mouse across the slide to draw the shape.
Note - Once your shape is inserted, if you want to resize it or give it special effects. Click on the shape and
the Drawing Tools appear on the Ribbon. Click the Format tab, and use buttons and options there to work with
the shape.
ADD TEXT TO A SHAPE
Shapes such as squares, circles, callouts, balloons, and block arrows can contain text. When you type
text into a shape, the text attaches to the shape and moves and rotates with it.
To add text that becomes part of a shape, select the shape and then type or paste the text.
INSERTING CHARTS INTO YOUR PRESENTATION
Inserting Charts created in Excel
1. In Excel, select the chart by highlighting the cells.
2. From the Home Tab Clipboard group, click Copy.
3. In PowerPoint, click in the placeholder on the slide where you want to insert the chart. 4. On the
Home tab, in the Clipboard group, click Paste.
Inserting a Chart from within PowerPoint
1. In PowerPoint, click the slide where you will insert chart.
2. On the Insert tab, in the Illustrations group, click the type of chart you want to use.
3. In the Insert Chart dialog box, click chart, then click OK.
Office Excel 2007 opens in a split window and displays sample data on a worksheet.
In Excel, to replace the sample data, click a cell on the worksheet. 4. Type your data that you want.
Inserting SmartArt Graphics
On the Insert tab, in the Illustrations group, click SmartArt.
1. In the Choose a SmartArt Graphic dialog box, click the type and layout that you want.
2. Enter your text by doing one of the following:
a. Click in a shape in your SmartArt graphic, and then type your text.
b. Click Text in the Text pane and then type or paste your text.
c. Copy text from another program, click Text, and then paste into the Text pane. A SmartArt graphic is
a visual representation of your information that you can quickly and easily create, choosing from
among many different layouts, to effectively communicate your message or ideas.
SAVING A NEW PRESENTATION
1.
2.
3.
4.
Click on Microsoft Office Button.
Click Save-As.
In the File name type the name of the presentation.
Click Save.
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Note - If you need to save in a different location click the down arrow on the right end of the save in
box and then choose your location.
CHANGING THE ORDER OF THE SLIDES
1. In the Outline and Slides tab Pane, click the Slides tab.
2. Click on the slide thumbnail that you want to move, and then drag them to their new location.
Tip - To select multiple sequential slides, click the first slide, and then hold down SHIFT while you click the
last slide that you want to select. To select multiple non-sequential slides, hold down Control while you click
each slide that you want to select.
INSERTING OBJECTS INTO YOUR PRESENTATION
From the Animation Tab PowerPoint 2007 enables you to easily apply animation effects to make your
presentation more appealing. You can choose to have your slides fade-in or dissolve.
In addition to this, you can control the timing of the transition from slide to slide and how the transitions will
occur.
Just go to the Animation tab, click on the slide you wish to add the animation and select an option. The
finishing tasks for creating your presentation are located on the Slide Show and Review Tabs.
Use the Slide Show tab to create narration, set-up views, and multiple monitors. The Review tab is for spell
check and reviewing comments.
KEYBOARD SHORTCUTS FOR PRESENTATION ACTIVITY SHORTCUT
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Start a presentation from the beginning. F5
Perform the next animation or advance to the N, Enter, Page Down, Right Arrow, next slide. Down
Arrow, Or Spacebar
Perform the previous animation or return to P, Page Up, Left Arrow, Up Arrow, Or the previous slide.
Backspace
Go to slide number. Number+Enter
Display a blank black slide, or return to the B Or Period presentation from a blank black slide.
Display a blank white slide, or return to the W Or Comma presentation from a blank white slide.
Stop or restart an automatic presentation. S
End a presentation. Esc Or Hyphen
Erase on-screen annotations. E
Return to the first slide. 1+Enter
Display the shortcut menu. Shift+F10
Go to the first or next hyperlink on a slide. Tab
The Ribbon can be reduced to a single line of CTRL+F1 tabs
Print preview CTRL+F2
To close the presentation CTRL+F4
To restore the presentation CTRL+F5
To minimize the presentation CTRL+F9
To duplicate the image Select the object and press CTRL+D
To group the objects first select what you want to group and then press CTRL+G
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Making a good presentation can be easy if you include the following elements:
Element 1:
Simple slides, with no more than one concept per page, and no more than 25-30 words per page.
Good
Not so good
Element 2:
Text and images should be kept within a reasonable distance from the edges of the slide. This prevents the
slide from looking over-crowded.
Good
Not so good
Element 3:
Slides that are easy to read. Avoid flashy color schemes, fonts, and animation. These features should
complement a presentation, and not be the presentation itself.
Good
Not so good
Software user interface
This is the visual part of a computer application or OS through which a user interacts with a computer or
software.
Graphical user interface (GUI)
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Is a type of interface that allows a user to use menus and visual images such as icons, buttons and other
graphical objects to issue commands.
Advantages of GUI
 It is user friendly because it is easy to learn and work with.
 There is no need to type and memorise any command language.
 The interface is similar for any application
 GUI has a coloured screen with icons each representing a program which is appealing to the user.
 It has help documentation.
Disadvantages of GUI
 They need significantly more memory (RAM) and processing power to run than other interface types
 It also occupies more disk space to hold all files for different functions.
 It difficult to automate functions for expert users.
 They can be irritating to experienced users when simple tasks require a number of operations
Command Line Interface (CLI)
This is a text-based interface that is used to operate software by entering commands.
Advantages f (CLI)
 It uses the fewest system resources in terms of memory and processing power.
 It is faster for expert users because they can quickly access commands.
 Many commands can be grouped together as batch files so that repetitive tasks can be automated.
Disadvantages
 It is difficult to use because some commands are hard to memorize
 Text editing can be strict and tiresome because commands have t be typed precisely. If there is a
spelling error the command will fail.
 It is time consuming because if you mis-type an instruction, it is often necessary to start from scratch
again.
 For efficient use, it requires the user to learn complex commands.
Comparison between GUI and CLI
SENIOR THREE TERM: ONE
TOPIC 6: SYSTEM START-UP AND CONFIGURATION
6.1. COMPUTER BOOTING
Booting means starting a computer. There are two main ways of booting a computer i.e. cold booting and
warm booting.
Types of booting
Cold booting is the starting of a computer from its off state from the mains. Involves switching on a
computer right from the main power supply, stabilizer or uninterruptible power supply (UPS), the system unit
and the monitor
Warm booting is the restarting of a computer by either the restart button or pressing the following keys
together and then releasing them at the same time Ctrl+Alt+Delete. Normally, a computer is warm booted
after it hanged i.e. not responding to any command
The booting process
i.
Power on and access the BIOS.
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ii.
The BIOS runs the complementary metal oxide semiconductor (CMOS) on the motherboard. CMOS helps to
keep track of the current date and time (system time)
The BIOS the runs Power-On self Test (POST). POST checks whether all the basic hardware (RAM, Disk
Drives, keyboard) are working properly.
Once the above operation is complete, BIOS looks for an OS to load.
The operating system is then loaded.
iii.
iv.
v.
6.2. System configuration
The way a system is set up, or the assortment of components that make up the system. Configuration can
refer to either hardware or software, or the combination of both. For instance, a typical configuration for a PC
consists of 32MB (megabytes) main memory, a floppy drive, a hard disk, a modem, a CD-ROM drive, a VGA
monitor, and the Windows operating system.
It may mean the Preferred hardware-software arrangement (specific to a particular computing environment)
involving dip-switch settings, interface settings, jumper settings, hardware drivers, software options, etc., that
determines what the system will do and how its parts will interact.
The devices that may be configured include:
 The hard drive (disc) setting partitions.
 The disc drives.
 The printers.
 Monitors. To the desired display.
System specifications
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What to consider when purchasing a computer
The computer platform. Here you consider which type of microcomputer would you like to buy it Toshiba,
Macintosh, hp or IBM
Hard disk. The choice of a hard disk mainly depends on several factors ie the tasks that the computer will
be used whether the operations will keep on increasing requiring more memory or will be constant.
Display device. Currently there are two types of displays ie CRT and LCD. CRT occupy bigger space and
consumes a lot of power whereas LCD are better
Expansion slots. Expansion slots are found on desktop computers which provide space for expansion
cards (add-on-cards) that might have ports for additional peripheral components like TV cards
Sound Card. When planning to work with multimedia packages, especially sound, an appropriate card has
to be sought of.
Modems. These are used to transmit data to and from the computer. So you have to consider whether
the modem is capable of both wireless and wire internet connection
PC Casing. This refers to the physical structure of the box that contains and shields the working
components of a computer ie do you need a tower casing or standard desktop casing
PC case molding. Which sharp and design do you want
Cost
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COMPUTER PARTS
PARTS OF A COMPUTER SYSTEM
PARTS
OF A COMPUTER
The monitor: This is a device which shows/gives the soft copy of the data/information in the computer.
Monitor
There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal display)
monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and
lighter. CRT monitors, however, are generally more affordable.
Keyboard. It’s an input device that converts letters and other characters into electric signals readable by the
processor. It has a type writer area, function keys, cursor movement keys and numerical keypad. It’s a device
which enables a computer user to communicate to the computer system.
Mouse. This is a hand held pointing device which is used to point, select, move and draw object in the
computer screen. Examples of mice include: codeless, touch pad (touch tone pad), mouse stick.
Printers. These are devices which gives a hard copy of the soft copy of the data or information held in the
computer. Printers are output devices that produce text and graphics on paper. The two main types of printers
are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print
in black and white or in full color and can produce high-quality photographs when used with special paper.
Laser printers are faster and generally better able to handle heavy use.
Speakers. Speakers are used to play sound. They may be built into the system unit or connected with cables.
Speakers allow you to listen to music and hear sound effects from your computer.
System unit; A casing /box that houses the internal electronic components
Is an enclosure that contains most the computer components.
CD/DVD Drive
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This a computer hardware device that reads compact discs and DVDs
Hard drive
System devices
System unit. Is an enclosure that contains most the computer components.
Or is a casing /box that houses the internal electronic components
RAM chip. A primary data storage device which allows data to be accessed at a high speed in any order.
Or this is a working of the a computer which stores data temporarily
Power supply. A device that supplies the required amount of power to all components of a computer.
Or a computer hardware that converts AC to DC for computer use
Bus. A communication system/path/highway through which data travels to and from different parts of a
computer.
Peripheral devices. Electronic equipments connected from outside the computer and even if removed, the
computer continues to work.
CMOS (Complementary metal oxide semi-conductor). This is an on board battery powered semi-conductor
chip inside the computer that stores information. It ranges from managing system time and date to system
hardware settings for the computer.
Expansion slots. This is a socket on the motherboard that is used to insert expansion cards for the circuit
board. It provides additional features to a computer such as video cards; TV cards graphic cards and Ethernet.
Motherboard; this is the main circuit board of the microprocessor where all internal components of a
computer are attached. It contains connectors for attaching additional components e.g. RAM chips, CPU etc.
Computer drives; a drive is a medium that is capable of reading and writing information from storage devices.
E.g. hard disk drive, floppy drive, CD/DVD drive etc.
CONNECTION AND SETUP OF HARDWARE COMPONENTS
FORMATTING DISKS; Disk formatting is the configuring process of a data storage media such as a hard disk
drive, floppy disk or flash drive for initial usage.
1.3.
SYSTEM INSTALLATION
Is the act of making the program ready for execution.
Installation: refers to the process of adding hardware components to the computer or activating software
such that it works with the computer.
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Software Installation: is the process of activating software such that it works with a computer.
Hard ware installation: Refers to the process of adding hard ware components to the computer.eg disc
drive, printer, camera
An installation program or installer is a computer program that installs files, such as applications, drivers, or
other software, onto a computer.
Uninstaller utility; software is a program that deactivates an application from the computer.
Program Files' is a standard folder in Microsoft Windows operating systems in which applications that are not
part of the operating system are conventionally installed.
A software suite or application suite is a collection of computer programs —usually application software or
programming software
Installing device drivers.
A device driver is a program that controls a particular type of device that is attached to your computer. There
are device drivers for printers, displays, CD-ROM readers, diskette drives, and so on.
Uninstallation; means to remove an application from a computer. Uninstalling removes all files that were
added to the computer when the application was initially installed.
A boot disk is a removable digital data storage medium from which a computer can load and run an
operating system or utility program.
1.4.
Computer troubleshooting
This is any form of problem solving on a computer system often applied to repair failed products or process
State any three ways how to troubleshoot a computer
 restarting of the computer
 check the electric power cables weather connected well
 listen for unusual sounds
 look inside the system unit for wires that are not plugged
 disconnect peripheral devices e.g. printers and restart
System performance
7.1. Introduction to computer communication
The transmission of data from one computer to another, or from one device to another. A communications
device, therefore, is any machine that assists data transmission. For example, modems, cables, and ports are
all communications devices.
Definition of terminologies
Computer Network
A computer Network is a collection of two or more computers and devices connected by channels so that they
can communicate with each other and share resources:
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Examples of resources
 data, a single internet connection,
 software,
 peripheral devices, processing power.
Encoding
This is the process through which Information (e.g. data, text, voice or video) from the sending device is
converted into signals which the communication medium can carry.
Transmission
This is the process through which the signals are broad cast/ sent out through the medium to the receiving
device.
Decoding
This is the process through which the signals are converted back into the information in its original form in the
receiving device.
Telecommunication
refers to transmission of data and information over a long-distance, eg television
Teleprocessing:
This refers to access and modification of computer files located elsewhere.
Downloading:
To Download is to transfer a file to your computer from another.
Uploading
means to transfer a file from your computer to another.
Throughput
refers to the rate of how much data is moved during a certain amount of time.
Bandwidth.
The amount of signals that can travel over a communications channel sometimes. The higher the bandwidth,
the more data and information the channel can transmit.
Data Encryption
This is Process of converting data into coded form (cypher text) to prevent it from being read or understood
by unauthorized people. Encrypted data is difficult to decode without a secret key
Communications Software
This refers to a set of instructions (software) needed by a computer before it starts sending and receiving
data from other computers.
Importance of computer communication
 It allows sharing of hardware like printers.
 It allows sharing of software between two or more computers, hence reducing on cost.
 It allows sharing and transfer of data and information stored on other computers on the network.
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Facilitate communications between people e.g. through electronic-mail, Mobile phones,e.t.c.
Computer communication has security & tight control measures over data access.
It enables online learning and collaborative research.
It allows access to common databases for example in banks.
Has enabled improved travel service through e-bookings and e-reservation.
Provides for online employment e.g. telecommuting.
Limitation of computer communication
 Data theft. If a computer is a standalone, physical access becomes necessary for any kind of data
theft. However, if a computer is on a network, a computer hacker can get illegal access.
 Rapid Spread of Computer Viruses: If any computer system in a network gets infected by
computer virus, there is a possible threat of other systems getting infected.
 Expensive Set Up: The initial set up cost of a computer network can be high depending on the
number of computers to be connected.
 Dependency on the Main File Server: In case the main File Server of a computer network breaks
down, the system becomes useless.
 Exposure to External Exploits. Someone on a different computer can send data to the computer in
such a way as to attack it - make it lock up or crash, make it slow down, or even take control of it.
 Automatic Downloads. If a computer is connected to a network, it's easier to download and install
software from the network onto the computer without any human intervention. If the new software
hasn't been tested, it could cause unpredictable behavior.
 Computer Networks can Fail. Computer networks can be so powerful and useful that it is very vital
for them to be used. All of the computers in an office building might become completely useless if a
single network component fails.
Transmission media (Channels)
Transmission media refers to the physical materials that are used to transmit data between computers.
For communications between computers that are linked by cable, there are three choices:
 Twisted wire,
 Coaxial cable,
 Fiber optic line.
1. Twisted wire
Twisted pair cable comes in two varieties: Shielded and Unshielded Twisted Pair (UTP). UTP is the most
popular.
Advantages:
 It is of low cost
 small in size
 easy to install
 It is the most popular and generally the best for schools.
Disadvantage:
 Subject to interference
 limited distance, usually less than 100 meters
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diagram of a twisted wire
70
2. Coaxial cable
Coaxial cable consists of a single copper wire surrounded by at least three layers:
 An insulating material
 A woven or braided metal
 A plastic outer coating.
Cable TV wiring often uses coaxial cable because it can be cabled over longer distances than twisted-pair
cable.
Advantages
 Coaxial cable is insulated more heavily than twisted-pair cable. So it is highly resistant to signal
interference.
 Used for longer distances (300 – 600 meters)
 Transmits faster than UTP
Disadvantages
 Heavy & bulky
 Needs booster over longer distances
diagram of a coaxial cable
3. Fiber Optic Cable
Each strand, called an optical fiber, is as thin as a human hair.
Each optical fiber is surrounded by an insulating glass cladding and a protective coating.
Fiber-optic cables are used by many local and long-distance telephone companies, cable TV, and in high-traffic
networks or as the main cable in a network.
Advantages:
 Carry significantly more signals than other cables.
 Faster data transmission.
 Less vulnerable to electrical noise from other devices
 Better security for signals during transmission.
 Smaller size, and much thinner and lighter than other cables.
Disadvantages:
 Expensive as compared to other media
 Harder to install and modify.
diagram of a fiber optic cable
Wireless Broadcast
Wireless telecommunications technologies transport digital communications without cables between
communications devices.
Wireless transmission media used in communications include broadcast radio, cellular radio, microwaves,
communications satellites, and infrared & bluetooth.
Wireless transmission is more convenient than installing cables but it has slower data transfer than hard-wired
methods and it is also Subject to interference
Microwave
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Microwaves are high-frequency radio waves that are sent through the atmosphere and space to deliver
telecommunications services, including TV distribution. It is dependent on line of sight.
Advantage:
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Speed of light
Microwave signals can carry thousands of channels at the same time
Disadvantage:
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Line-of-sight only- (there is need for radio transmitters in networks using air interface (radio waves) to
be positioned free of obstacles)
Satellite
A satellite is basically a microwave station placed in outer space. The satellite receives a signal from the earth,
amplifies it, and then rebroadcasts it at a different frequency to any number of earth-based stations.
Advantage: Always in sight
Disadvantage: Expensive uplink and downlink facilities
Infrared and Bluetooth
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IrDA (Infrared Data Association) ports transmit data via infrared light waves. As long as the devices are
within a few feet and nothing obstructs the path of the
infrared light wave, data can be transferred without the use of cables.
Bluetooth port is an alternative to IrDA. Bluetooth technology uses radio waves to transmit data
between two devices.
Many computers, peripherals, smart phones, PDAs, cars, and other consumer electronics are Bluetoothenabled, which means they contain a small chip that allow them to communicate with other Bluetoothenabled computers and devices.
DATA TRANSMISSION
 Telecommunications involves the transmission of data, information, and instructions among computers.
 Any transmissions sent during these communications can be categorized by a number of characteristics
including the signal type, transmission mode, transmission direction, and transmission rate.
 Signal Type: Recall that computers produce digital signals yet telephone equipment originally was
designed to carry only voice transmission in the form of an analog signal.
Analog Signals
 An analog signal uses variations which are represented by a continuous waveform to convey
information.
 It is particularly useful for wave data like sound waves.
 Analog signals are what normal phone line and sound speakers use.
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Digital Signals
A digital signal is a series of discrete (discontinuous) bits which are simply the presence or absence of an
electric pulse. The state of being on or off represents the binary digit of 1 or 0, respectively.
Advantages of digital signals include:
 Digital signals can be copied exactly without any loss of quality
 Digital signals can be further processed by computer.
Transmission Modes
 When two devices exchange data, the data flows between the devices as a continuous stream of bits.
 There are two basic transmission techniques for separating the groups of bits: asynchronous
transmission and synchronous transmission
Asynchronous transmission
 Asynchronous transmission transmits one byte at a time over a line at random intervals.
 Each byte is framed by controls—a start bit for marking the beginning of the byte, a stop bit for
marking the end of the byte, and a parity bit for error checking.
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Asynchronous transmission is relatively slow and used for low-speed transmission.
Synchronous transmission
 Synchronous transmission transmits groups of bytes simultaneously at regular intervals.
 The beginning and ending of a block of bytes is determined by the timing of the sending device and
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receiving devices.
Although synchronous transmission requires more complicated and expensive communications devices,
it provides much higher speeds and greater accuracy than asynchronous transmission.
Transmission Direction
The direction in which data flows along transmission media is characterized as
 simplex,
 half-duplex,
 full-duplex or
 multiplex
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Simplex transmission
Simplex transmission sends data in one direction only. Simplex transmission is used only when the sending
device does not require a response from the receiving device. One example of simplex transmission is
television broadcasting.
Half-duplex transmission
Half-duplex transmission allows data transmission in either direction, but only one way at a time. Many fax
machines, police radio calls, credit card verification systems and automatic teller machines use half-duplex
transmission.
Full-duplex transmission
In full-duplex transmission, data can flow in both directions at the same time. A regular telephone line, for
example, supports full-duplex transmission, allowing both parties to talk at same time.
Multiplex transmission
In multiplex transmission, several different types of signals can be carried at once through the same line. E.g.
During Video calls where Images
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7.2. Networks
What is a Network?
A network is the connection of two or more computers/computing devices in order to share resources,
exchange files, or allow electronic communications. The computers on a network may be linked through
cables, telephone lines, radio waves, satellites, or infrared light beams.
TYPES OF NETWORKS
The three basic types of networks include: LAN, MAN and WAN.
LOCAL AREA NETWORK (LAN)
A network is said to be Local Area Network (LAN) if it is confined relatively to a small area. It is generally
limited to a building or a geographical area, expanding not more than a mile apart to other computers.
LAN configuration consists of:
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A file server - stores all of the software that controls the network, as well as the software that can be
shared by the computers attached to the network.
A workstation - computers connected to the file server (Mac or PCs). These are less powerful than the
file server
Cables - used to connect the network interface cards in each computer.
Types of LANs / Network models
The two major types of network operating systems are:
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Peer-to-Peer
Client/Server
Peer-to-Peer
In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the
resources available on the network. Peer-to-peer networks are designed primarily for small to medium local
area networks. AppleShare and Windows for Workgroups are examples of programs that can function as peerto-peer network operating systems.
Peer-to-peer network operating systems allow users to share resources and files located on their computers
and to access shared resources found on other computers.
However, they do not have a file server or a centralized management source (See fig. 1).
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Fig. 1. Peer-to-peer network
Advantages of a peer-to-peer network:
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Less initial expense - No need for a dedicated server.
Setup - An operating system (such as Windows XP) already in place may only need to be reconfigured
for peer-to-peer operations.
Disadvantages of a peer-to-peer network:
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Decentralized - No central repository for files and applications.
Security - Does not provide the security available on a client/server network.
Client/Server
A server is a centralized computer that controls the shared resources on the network while a client computer is
a computer that sends requests to the server and it is dependant on the server.
Client/server network allows the network to centralize functions and applications in one or more dedicated file
servers (See fig. 2).
Fig. 2. Client/server network
Advantages of a client/server network:
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Centralized - Resources and data security are controlled through the server.
Scalability - Any or all elements can be replaced individually as needs increase.
Flexibility - New technology can be easily integrated into system.
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Interoperability - All components (client/network/server) work together.
Accessibility - Servers can be accessed remotely and across multiple platforms.
Disadvantages of a client/server network:
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Expense - Requires initial investment in dedicated servers.
Maintenance - Large networks will require a staff to ensure efficient operation.
Dependence - When server goes down, operations will cease across the network.
Client-server model
METROPOLITAN AREA NETWORK (MAN)
Metropolitan Area Network (MAN) covers relatively larger geographic areas, such as cities. Often used by local
libraries and government agencies to connect to citizens and private industries
WIDE AREA NETWORK (WAN)
Wide Area Networks (WANs) connects larger geographic areas, such as London, the UK, or the world. In this
type of network dedicated transoceanic cabling or satellite uplinks may be used.
Intranet is a private network that allows access to organization data/information to only members of the
organization.
Extranet is a private network that allows access to organization data/information to members within the
organization and some authorized outsiders like suppliers
Advantages of computer Networks
Speed. Networks provide a very rapid method for sharing and transferring files. Without a network, files are
shared by copying them to floppy disks, then carrying or sending the disks from one computer to another. This
method of transferring files (referred to as sneaker-net) is very time-consuming.
Cost. Networkable versions of many popular software programs are available at considerable savings when
compared to buying individually licensed copies. Besides monetary savings, sharing a program on a network
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allows for easier upgrading of the program. The changes have to be done only once, on the file server, instead
of on all the individual workstations.
Security. Files and programs on a network can be designated as "copy inhibit," so that you do not have to
worry about illegal copying of programs. Also, passwords can be established for specific directories to restrict
access to authorized users.
Centralized Software Management. One of the greatest benefits of installing a network at a school is the
fact that all of the software can be loaded on one computer (the file server). This eliminates the need to spend
time and energy installing updates and tracking files on independent computers throughout the building.
Resource Sharing. Sharing resources is another area in which a network exceeds stand-alone computers.
Most schools cannot afford enough laser printers, fax machines, modems, scanners, and CD-ROM players for
each computer. However, if these or similar peripherals are added to a network, they can be shared by many
users.
Electronic Mail. The presence of a network provides the hardware necessary to install an e-mail system. Email aids in personal and professional communication for all school personnel, and it facilitates the
dissemination of general information to the entire school staff. Electronic mail on a LAN can enable students to
communicate with teachers and peers at their own school. If the LAN is connected to the Internet, students
can communicate with others throughout the world.
Flexible Access. School networks allow students to access their files from computers throughout the school.
Students can begin an assignment in their classroom, save part of it on a public access area of the network,
then go to the media center after school to finish their work. Students can also work cooperatively through the
network.
Workgroup Computing. Workgroup software (such as Microsoft BackOffice) allows many users to work on a
document or project concurrently. For example, educators located at various schools within a county could
simultaneously contribute their ideas about the new curriculum standards to the same document and
spreadsheets.
Disadvantages of computer Networks
Expensive to Install. Although a network will generally save money over time, the initial costs of installation
can be prohibitive. Cables, network cards, and software are expensive, and the installation may require the
services of a technician.
Requires Administrative Time. Proper maintenance of a computer network requires considerable time and
expertise. Many schools have installed networks, only to find that they did not budget for the necessary
administrative support.
File Server May Fail. Although a file server is no more susceptible to failure than any other computer, when
the files server "goes down," the entire network may come to a halt. When this happens, the entire school
may lose access to necessary programs and files.
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Cables May Break. The Topology chapter presents information about the various configurations of cables.
Some of the configurations are designed to minimize the inconvenience of a broken cable; with other
configurations, one broken cable can stop the entire network.
Other disadvantages of networks
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Server faults stop applications being available
Network faults can cause loss of data.
Network fault could lead to loss of resources
User work dependent upon network
System open to hackers
Decisions tend to become centralized
Could become inefficient
Could degrade in performance
Resources could be located too far from user
Internet
It’s the global interconnection of computers to share information and data.
Internet is an arrangement of connected computers, which lets the computer users all over the globe
exchange data.
Connecting to the Internet
Requirement
 A computer or PDA or cell phone
 An account with an ISP (Internet Service Provider)
 A modem (modulator/demodulator) for dial-up services or a NIC (Network Interface Card) for DSL/Cable
services
Connection Types
 Broadband Services. This is a high speed internet connection method that is provided through either a
cable or telephone companies.
 WAN
LAN (Local Area Network). A network of computers that are in the same physical location, such as home or
building. Usually connected using Ethernet. A standard on how computers communicate over a shared media
(cable)
WLAN (Wireless LAN)
 Wi-Fi (Wireless Fidelity). A wireless technology that connects computers without cables
 Access Point (AP). A device (base station) that connects wireless devices together. usually connected to a
wired-network
 ESSID (Extended Service Set ID)
A “name” for the AP, eg. Mobile net
 Hotspots. These are sites that offer internet access over a wireless local area network by use of a router
that connects to an ISP
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 Dial-up Services. This method requires users to link their phone lines to a computer in order to access the
internet
 Modem (Modulator/demodulator) A device that converts analog signal to digital (modulation) and vice
versa (demodulation).
 ISDN (Integrated Services Digital Network). This allows users to send data, voice and audio content over
digital telephone lines. The installation of ISDN adapters require at both ends of transmission an ISP.
 DSL (Digital Subscriber Line). A technology that provides digital data transmission over unused frequencies
on traditional telephone lines.
 Cable. A technology that provides digital data transmission over cable TV infrastructure
 Satellite. A technology that provide digital data transmission over satellites. Need a satellite dish
State the advantages and disadvantages of using the Internet
Advantages of the Internet:
 Communication: By sending an e-mail, we can contact a person who is physically present thousand
miles away within the fraction of a second’s time.
 E-commerce is the idea that is implemented for any form of business transactions that entails
transmission of data from one corner of the world to another. E-commerce has become a fantastic option
through which you can shop anything.
 Online Chat: There are many ‘chat rooms’ on the web.
 Downloading Software: This is one of the most happening and fun things to do via the Internet.
 Online learning. It facilitates long distance learning.
 Entertainment. A wide variety of entertainment including video games, music, movies, chat room, news
and others can be accessed through the Internet.
 The biggest benefit offered by the Internet is information. It functions as a valuable resource of
information. You can find any type of information on any subject with the help of the search engines like
Yahoo and Google.
 Formation of communities. Internet helps in formation of communities or forums. Here a number of
people can participate in different types of debates and discussions express their views and gather
valuable knowledge.
 A variety of other advantages offered via Internet, include: job searching, online banking, buying movie
tickets, hotel reservations and consultation services etc.
Disadvantages of the Internet:
 Pornography: This is a very serious issue concerning the Internet, especially when it comes to young
children.
 Spamming: This refers to sending unsolicited e-mails in bulk, which serve no purpose.
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Virus threat. Virus is a program that interrupts the usual operation of your personal computer system. PCs
linked to the Internet have high probability of virus attacks and as a result of this your hard disk can crash,
giving you a lot of trouble.
Theft of personal details while using the Internet, there is high probability that your personal details like
name, address and credit card number may be accessed by con artists and used for fraudulent purposes.
Some people are getting addicted to the internet and thus causing problems with their interaction of
friends and loved ones
It provides a lot of wrong information. This is because any one can post anything and much of it is
garbage.
Factors that determine internet speed.
 Internet traffic; the server speed of the site you are visiting determines the speed of the internet.
 Device hardware; your computer’s resources like speed, memory etc also determine the internet speed i.e.
if they are inadequate, the speed will be low.
 Viruses and malware; these consume significant resources like memory and adversely affect internet
speed.
 Number of applications running; multiple programs using internet like downloading music with ITUNES and
surfing the web using Firefox will reduce the overall speed.
 Number of devices connected; multiple laptops, tablets, smart phones reduce the overall speed of each
device on the internet.
Internet service provider (ISP) . A company that provides internet access to individuals and business.
Examples; Info com, Mai web, communication companies like MTN, AIRTEL, AFRICELL etc.
Services provided by ISP include; internet access, Domain name registration, E-mail accounts, web hosting, Ip
addresses and ranges.
Factors to consider when selecting an ISP
 Price; one should select an ISP whose price is friendly.
 Technical support; Be sure the ISP you select provides technical support that meets your organization's
requirements or that can offer help incase things go wrong.
 Viability; when selecting an ISP, do some checking to see how long the company has been in existence,
track of records and whether or not they received an award.
 Performance; whether you are paying for a high speed connection or just using dial up, you should check
the ISP’s track records for such things as uptime and overall throughout.
Internet communication services
a) Email Services
Electronic mail (or e-mail) is an Internet service that allows those people who have an e-mail address
(accounts) to send and receive electronic letters.
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Advantages of email:
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Cost .Email is cheap: businesses can save large amounts of money using e-mail, in lieu of long-distance
phone calls and postal deliveries.
Time .Email will reach its destination across the world in a few seconds as opposed to days or even weeks
with the postal service.
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Convenient .Email doesn't worry about crossing time zones or that colleagues are not in their offices to
take telephone calls.
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Email can be sent to groups of people at the same time. This facilitates collaborative working and efficient
dissemination of information.
Doesn't use any paper (good for the environment).
Can attach large documents and other files with a click of a button (and without using up resources like
paper).
Unlikely to be lost
Faster to arrive
Allows sending messages to several people at a time
Cheaper in terms of costs incurred
Less prone to illegal access
Allows sending multimedia format document
Several documents can be sent at once
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Disadvantages of emails:
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User has to open email website or email program to read the message. If you do not login, unread
messages can remain unread forever.
Socially, writing a letter and talking over a phone is thought to bring you closer to the recipient compared
to writing an email through a computer.
A lot of unwanted emails from spammers can fill your email inbox and important emails may not get
delivered.
Email attachments can bring virus into your computer if not scanned by the network or virus program on
your computer.
Emails cannot really be used for official business documents.
Less hand-writing practice.
Can be bad for your eyes if you spend too long sending e-mails on your computer.
Messages may be misinterpreted easily.
Components of an e-mail
Address or To
This is where the address of the person whom you are sending the message must be typed. E.g.
siraji1987@learnonline.ac.ug to mean the massage is for siraji belonging to learn online which is an academic
institution (ac) of Uganda (Ug)
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The subject
This is where you type subject or theme of your document e.g. Inquiry, Application to someone.
CC.
Carbon copy: here you type the addresses of those to whom you are sending carbon copies. They can be as
many
addresses
for
cc
as
you
wish
only
are
separated
by
commas
e.g.
Ronnie@yahoo.com,opio@goodwillenc.co.ug, siraji3rk@yahoo.com.
BCC
Blind carbon copies: here you type the addresses as in cc, but the recipients will not know whether the other
has received the copy.
Other internet communication services/tools
b) Instant messaging; this type of online chat which offers real time text transmission over the internet.
c) Video conferencing; this is a technology that allows users in different loctions to hold face-to-face meetings
on the internet. It involves transmission of audio and video data.
Equipments for video conferencing
Computers, web cam, a microphone, skype, speakers, high speed internet, video conferencing software
Advantages of video conferencing
 It can take place without leaving the office
 It minimizes travel costs
 Meetings can be called instantly
 Delegates can still attend the meeting even if they are physically unable
 It saves time
 Increases productivity by sharing of data.
Disadvantages
 Confidential documents that need to be viewed and signed in person may not be used.
 It is more expensive
 It is limited to certain number of participants
 Stability of connection requires complex technology
d) Chat room; this is a software application in which participants can engage in real time discussions about a
specific topic with one another.
e) News group. This is an internet based discussion about a particular topic. It ranges from transport, cars,
investments etc.
f) Cloud computing; In cloud computing a type of Internet-based computing," where different services —
such as servers, storage and applications — are delivered to an organization's computers and devices
through the Internet.
Or the practice of using a network of remote servers hosted on the internet to store and manage resources.
Examples include; e-mail communication, online storage such as Google drive, Drop box, web hosting services
etc
g) Web browser
Web Browser is a software tool or program that allows you to navigate through the web.
Or it’s an application software that allows users to access/connect to the internet or
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It’s a tool that allows you to view web pages and interact on the internet.
Examples of web browsers include: Google Chrome, Mozilla Firefox, Internet Explorer, Opera, and Safari,
Konqueror, Flock , etc.
h) Search engine
Search engine. It’s a program or web site that can be used to search for keywords on web pages throughout
the World Wide Web.
A web search engine is a type of website that helps computer user find specific information on the Internet.
Search engines include: Google, Yahoo!, Ask.com, Forestle, Bing and Alta Vista.
Searches for information from the Web
Uses search engine syntax.
i) Website
Web site is the location of a web domain name in a computer somewhere on the internet.
Types of Websites
Static-Content:
In static Websites, the information does not change, and the same information is displayed to all visitors.
Mostly coded in HTML so easier to build.
Most commonly used for simple sites.
Updating is difficult.
Cannot do complex tasks, such as providing user interactivity.
Dynamic-Content: Dynamic website pages are able to accept input data (fill-in forms) and store that
information in a database on the server, allowing a visitor to create a user profile and personalized
experience.
In Dynamic Websites, the information may change at any given time and according to the visitor. Mostly built
in scripting languages like Javascript, and can be more difficult to build.
Used for large sites with a lot of content, sites that need extensive updates, use real time services (e.g. online
stores), and/or require automatic changes (e.g. blogs). Updating is easy.
Can do complex tasks, allowing for user interactivity and providing customized, personalized information
Personal Websites
A platform for individuals to provide information about themselves, promote themselves, create an online CV
and/or portfolio, keep in touch with family and friends, share photos and videos, expand hobbies and
interests, and express thoughts and ideas.
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Commercial/Business Websites
A platform for companies or organizations to provide information about themselves, market or sell their
products and/or services, and provide customer support
Informative Websites
These are dedicated to providing information. They may include news websites, online encyclopedias,
educational websites, and websites providing topic-specific information like sports data, medical information,
weather reports, stock market quotes and analysis, and TV guides.
Search Engines/Directories
These are search engines index material on the web that automatically respond to a search query with links to
relevant websites.
Directories list businesses by different categories and/or locations.
Wikis
A wiki is a specialized form of content-managed web site designed to support the easy collaborative creation
of web pages by groups of users.
Wikis differ from blogs and other cms options in that wikis allow all users to change the content of the wiki
pages, not just to post comments about the content.
Examples of wiki are Wikipedia, online encyclopedia can be publicly accessible and edited by any user.
Blogs
Web logs, or blogs, are the most popular, inexpensive, and widespread form of web content management.
Blog software such as Blogger, Roller, or WordPress allows nontechnical users to combine text, graphics, and
digital media files easily into interactive web pages.
Blog – online journal used to express ideas/opinions
E-Commerce website – platform to sell products online
Forum – promotes discussions among people with mutual interests
Media-Sharing Website – where people can share pictures, videos, music, etc.
Review Websites – where people can write and/or view reviews of products, services, etc.
Social Networking Website – where people can meet, interact and share multi-media.
Webmail – provides e-mail services
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The World Wide Web
(Abbreviated as WWW commonly known as the web) is a system of interlinked hypertext documents
accessed via the Internet.
Or it’s a vast collection of linked documents held on computers all over the world and is accessible via the
internet.
Netiquettes
Refers to the do's and don'ts of online communication
Or rules and regulations governing online communication
Here are some of the Best Rules of Netiquette
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Keep messages brief and use proper grammar and spellings
Never read someone’s private email
Respect other people’s privacy
Know where you are in cyberspace. Understand the group of people you are interacting with. When you
join a new group, first understand its likes and dislikes before giving your full contribution
Post only acceptable information that has no harm to the public
Minimize use of uppercase in text when sending messages
Be forgiving of other’s people’s mistakes like spelling error, a stupid question or unnecessary long answers
because experts on internet were once beginners.
Respect other people’s time and bandwidth. Ensure that time and bandwidth people spend reading your
posting is not wasted. Send a well prepared message and ensure that its sent to right recipient.
Make yourself look good online
Avoid impersonation
Be ethical and aim at acting within the laws of society and cyberspace
Don't spam. That is, don't repeatedly post the same advertisement for products or services. Most sites
have strict and specific rules about who is allowed to post ads and what kind of ads they are.
Remember that your posts are public. They can be read by your partner, your children, your parents, or
your employer.
Do not post copyrighted material to which you do not own the rights.
Treat others as you would like to be treated.
Types of Network Topology
Network Topology is the schematic description of a network arrangement, connecting various nodes (sender and
receiver) through lines of connection.
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BUS Topology
Bus topology is a network type in which every computer and network device is connected to single cable. When
it has exactly two endpoints, then it is called Linear Bus
topology.
Features of Bus Topology
1. It transmits data only in one direction.
2. Every device is connected to a single cable
Advantages of Bus Topology
1. It is cost effective.
2. Cable required is least compared to other
network topology.
3. Used in small networks.
4. It is easy to understand.
5. Easy to expand joining two cables together.
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Disadvantages of Bus Topology
1. Cables fails then whole network fails.
2. If network traffic is heavy or nodes are more the performance of the network decreases.
3. Cable has a limited length.
4. It is slower than the ring topology.
RING Topology
It is called ring topology because it forms a ring as each computer is connected to another computer,
with the last one connected to the first. Exactly two
neighbours for each device.
Features of Ring Topology A number of repeaters are
used for Ring topology with large number of nodes,
because if someone wants to send some data to the last
node in the ring topology with 100 nodes, then the data
will have to pass through 99 nodes to reach the 100th
node. Hence to prevent data loss repeaters are used in the
network.
1. The transmission is unidirectional, but it can be made bidirectional by having 2 connections
between each Network Node, it is called Dual Ring Topology.
2. In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in
them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.
3. Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass
through each node of the network, till the destination node.
Advantages of Ring Topology
1. Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes
having tokens can transmit data.
2. Cheap to install and expand
Disadvantages of Ring Topology
1. Troubleshooting is difficult in ring topology.
2. Adding or deleting the computers disturbs the network activity.
3. Failure of one computer disturbs the whole network.
STAR Topology
In this type of topology all the computers are connected to a single hub through a cable. This hub is the
central node and all others nodes are connected to the
central node.
Features of Star Topology
1.
Every node has its own dedicated connection to
the hub.
2.
Hub acts as a repeater for data flow.
3.
Can be used with twisted pair, Optical Fibre or
coaxial cable.
Advantages of Star Topology
1. Fast performance with few nodes and low
network traffic.
2. Hub can be upgraded easily.
3. Easy to troubleshoot.
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4. Easy to setup and modify.
5. Only that node is affected which has failed, rest of the nodes can work smoothly.
Disadvantages of Star Topology
1. Cost of installation is high.
2. Expensive to use.
3. If the hub fails then the whole network is stopped because all the nodes depend on the hub.
4. Performance is based on the hub that is it depends on its capacity
MESH Topology
It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each
other. Mesh has physical channels to link devices.
There are two techniques to transmit data over the Mesh topology, they are :
1. Routing
2. Flooding
MESH Topology: Routing
In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct
the data to reach the destination using the shortest distance. Or, routing logic which has information
about the broken links, and it avoids those node etc. We can even have routing logic, to re-configure
the failed nodes.
MESH Topology: Flooding
In flooding, the same data is transmitted to all the network nodes, hence no routing logic is required.
The network is robust, and the its very unlikely to lose the data. But it leads to unwanted load over the
network.
Types of Mesh Topology
1. Partial Mesh Topology : In this topology some of the
systems are connected in the same fashion as mesh topology but
some devices are only connected to two or three devices.
2. Full Mesh Topology : Each and every nodes or devices are
connected to each other.
Features of Mesh Topology
1. Fully connected.
2. Robust.
3. Not flexible.
Advantages of Mesh Topology
1. Each connection can carry its own data load.
2. It is robust.
3. Fault is diagnosed easily.
4. Provides security and privacy.
Disadvantages of Mesh Topology
1. Installation and configuration is difficult.
2. Cabling cost is more.
3. Bulk wiring is required.
TREE Topology
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It has a root node and all other nodes are connected to it forming a hierarchy. It is also called
hierarchical topology. It should at least have three levels to the hierarchy.
Features of Tree Topology
1. Ideal if workstations are located in
groups.
2. Used in Wide Area Network.
Advantages of Tree Topology
1. Extension of bus and star topologies.
2. Expansion of nodes is possible and easy.
3. Easily managed and maintained.
4. Error detection is easily done.
Disadvantages of Tree Topology
1. Heavily cabled.
2. Costly.
3. If more nodes are added maintenance is difficult.
4. Central hub fails, network fails.
HYBRID Topology
It is two different types of topologies which is a mixture of two or more topologies. For example if in
an office in one department ring topology is used and in another star topology is used, connecting
these topologies will result in Hybrid Topology (ring
topology and star topology).
Features of Hybrid Topology
1. It is a combination of two or topologies
2. Inherits the advantages and disadvantages of
the topologies included
Advantages of Hybrid Topology
1. Reliable as Error detecting and trouble
shooting is easy.
2. Effective.
3. Scalable as size can be increased easily.
4. Flexible.
Disadvantages of Hybrid Topology
1. Complex in design.
2. Costly.
Factors to consider When Choosing a Topology:
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Cost.
Future growth:
Length of cable needed.
Number of computers to be connected
Level of security required
SENIOR THREE
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INTRODUCTION TO SPREADSHEET
A spreadsheet is an interactive computer application program for organization and analysis of data
in tabular form.
Features of spreadsheet software
 Formulas to perform varying grades of mathematics.
 Text editing and formatting features
 Data storage and sorting facilities
 Relative and absolute referecing options
 Graphs and charts to visually represent data.
 Data import and export functions.
 Cells for data storage.
Functions of spreadsheet
 Creating, editing, saving and printing spreadsheets.
 Creating formulas, functions and graphs
 Data entry and analysis
 Sorting and filtering data
 Creating business forms such as invoices and purchase orders.
 Importing and exporting data.
 Creating and editing tables and charts
 Merging and splitting cells
 Inserting columns and rows etc.
Examples of spreadsheet
Microsoft excel, Lotus 1-2-3, Corell quarto, VisiCalc, Supercalc etc
MS EXCEL.
Excel is calculation/mathematics oriented application software.
It is used to prepare payroll, inventory and other accounts related statements.
It is a large electronic spreadsheet (table) made of rows and columns, so this is also called
spreadsheet program.
Screen elements in excel:
1. Menu bar: used to display the menu names, which contains number of commands. E.g.
home, insert, page layout etc.
2. Tool button: frequently used commands are made into buttons for easy access.
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3. Toolbars: collection of tool buttons of same category. E.g. standard and formatting
toolbars.
4. Formula bar: used to display the contents or the formula of the active cell.
5. Cell reference area. Used to display the address of the active cell.
6. column heading: used to display the name of the column (E.g. A,B,C…IV)
7. row heading: used to display the number of rows (E.g. 1,2,3,….16394)
8. Sheet: made up columns and rows.
9. One sheet contains 65536 Rows and 256 Columns.
10. Sheet tab: used to display the name of the sheet. E.g. sheet1, sheet2 etc.
11. Workbook: is the name of the excel file which contains 16 sheets by default. We can
increase or decrease the number of sheets in a workbook.
12. Cell: cell is an intersection of a column and row.
13. Cell address: each cell is represented by a unique code is called cell address. It is made up
of the column name and row number of that cell. E.g. A1, F40 etc.
Relative and absolute references
Relative Cell References
Is where cell references in formulas automatically adjust to new locations when the formula is
pasted into different cells
Example: =SUM(B5:B8), as shown below, changes to =SUM(C5:C8) when copied across to the next
cell.
Absolute Cell References
Is where cell references in formulas do not adjust when the formula is pasted into different cells.
Example:
In the example below, when calculating commissions for sales staff, you would not want cell
B10 to change when copying the formula down. You want both the column and the row to
remain the same to refer to that exact cell. By using $B$10 in the formula, neither changes
when copied.
Cell reference type summary
Reference type
formula
Relative
=A1
Absolute
=$A$1
Mixed
=$A1 or
A$1
what happens after copying the fomula
Both the column letter A and row Number 1 can
change
The column letter A and row number 1 do not
change
The column letter A doesn’t change and the row
number 1 can change or vice versa
Data types in Excel: normally four types of data types are used in excel.
1. Character /text data type: any combination of numbers, spaces, symbols and non-numeric
characters will be used. The default alignment is of the character data is left
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2. numeric data type:
Contains only numbers
A numerical data can contain only the following characters.
0 1 2 3 4 5 6 7 8 9 $ % etc
The default alignment is right.
3. Date data type:
The data which is treated as a date.
When you type the date, use the month, date, year format and separate by a slash (/) or a
hyphen (-)
The default alignment is Right.
4. Time data type;
The data which consider as a time
Use+: to separate the hour, minute, second.
Use a or p to indicate AM or PM (leave a single space before a or p)
The default alignment is Right.
FUNCTIONS
Functions are the pre defined formulas used in excel. Or function is a preset formula that is
intended to carry out a specific calculation.
e.g. =average(A1:A4)
functions can be more efficient way of performing mathematical operations than formulas. E.g. if
you wanted to add the values of cells D1 to D10, you would type the fomula
=D1+D2+D3+D4+D5+D6+D7+D8+D9+D10.
After the formula is typed into the cell, press ENTER and the calculation executes immediately.
A shorter way would be to use the sum function and simply type =sum(D1:D10).
Other common functions include: average, sum etc.
Common excel errors
#DIV/0!
You'll see this error if you try to divide a number by zero, or divide a number by an empty cell.
For example if you type =20/0 you'll see this error message.
Solutions:
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Check that you have the correct data in the cells referenced in the formula.
Check that your data is in the correct cells.
#VALUE!
It occurs if you use text instead of a number in certain formula. For example =D2*D3 would
give this error if either cell contained text. You could create the same error message by
typing the formula =4*"shop" because you are telling Excel to multiply a number by text.
#NAME?
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This message occurs if you enter an incorrect function name, or range name or cell reference.
So for example if you mistype "SUM" as "SIM" and type in a function as =SIM(D4:D8) then
you'll see this error message, because there is no such function.
#REF!
Excel creates this message if a cell reference in a formula has been deleted. For example if
your formula is D2+D3 and you later delete row 3, you'll see this error message. This because
Excel cannot determine which cell reference to use after the row is deleted.
#NUM!
This error occurs if there is a problem with a number in a formula or function. For example this
can be caused by a calculation resulting in a number too high or too small for Excel to cope
with. Some functions iterate and go through lots of calculations to determine a final answer
and these answers can be sometimes out of range. This can also occur if the wrong data type
is used in a function which requires numerical data.
#######
This is not strictly an error message but we'll include this anyway. This occurs if a calculation
results in a number is too wide to be displayed. For example a calculation resulting in the
value £100,000,000 will show as ##########. To cure this, you need to autofit the
column size or manually resize it.
#NULL! errors occur if:
multiple cell references in a formula are separated by a space instead of a mathematical
operator such as a plus sign ( + ) - example: =A1 A3+A5;
the start and end points of cell ranges are separated by a space instead of by the range
operator - the colon ( : ) - example: =SUM( A1 A5);



individual cell references in a formula are separated by a space instead the union operator
- the comma ( , ) - example: =SUM( A1 A3,A5);
Solutions: Separate cell references correctly.


separate cell references in a formula with a mathematical operator - example:
=A1+A3+A5;
separate the start and end points of a range with a colon ( : ) - example:
=SUM(A1:A5);
#REF! Errors - Invalid Cell References
An invalid cell reference error occurs when a formula contains incorrect cell references - rows
6 and 7 in the example above. This happens most often when:



individual cells or entire columns or rows containing data referenced in a formula are
accidentally deleted;
data from one cell is moved (using cut and paste or drag and drop) into a cell that is
referenced by a formula;
a formula contains a link - using OLE (Object Linking and Embedding) - to a program
that is not currently running.
Solutions:


use Excel's undo feature to recover data lost in deleted cells, columns or rows;
if the data cannot be recovered, re-enter the data and adjust the cell references if
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
needed;
open programs containing OLE links and update the worksheet containing the #REF!
error.
SENIOR THREE TERM: THREE
TOPIC 9: WEB DESIGNING
9.1.
Introduction to the web design
Introduction
 With the World Wide Web's explosion of popularity, millions of individuals and businesses
around the globe have tried their hand at publishing their own website.
 While the hypertext markup language (HTML) is easy to learn, its necessary learning curve
delays the web development process. Web authoring software removes this learning curve
and allows users to quickly and easily publish on the Web.
 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.
Web Design software Examples
There are lots of good web design software on the market today.
 Note Pad
 Microsoft FrontPage 2003
 Adobe Dreamweaver CS4
 WebPlus X4 (Now owned by Microsoft)
 Microsoft Expression Web 3.0 & Studio 3
 Namo WebEditor 8 & Professional
 Sothink DHTML Menu 9 & Tree Menu 2
 Antenna Web Design Studio 3
 AllWebMenus PRO 5
 PhotonFX Easy Website Pro 4
Terminologies
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
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(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.
 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) 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. eg <u> 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)
 WEB MAILPROVIDER
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
 WEBSITE
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A collection of related or hyperlinked web pages
 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.
Features of web authoring software
These are the basic features common to the working environment of most popular web
authoring software programs.
1. Views
 Most web authoring software provides multiple views of the web page you're working on.
 Standard, normal, or design view - This is typically the default view, which is a blank
screen on which you type, paste, or insert content. It uses the WYSIWYG principle. This
is very similar to a word processor screen.
 Code view - Allows you to view and work directly with the HTML code created for you by
the web authoring software.
 Split - Both of the above views are displayed simultaneously in separate windows.
2. Creating Headings and Subheadings
 In Normal or Design View, Web authoring software. A text formatting toolbar typically
includes buttons for bolding and italicizing text, and probably additionally includes some
means of identifying a heading or subheading.
3. Inserting Links
 In web authoring software products, you add a link to a document by selecting Insert from
the menu, then Link or Hyperlink. Most web authoring software tools additionally provide a
button or icon that allows you to quickly insert a link.
4. Inserting Images
 In many web authoring software products, you add an image to a document by selecting
Insert from the menu, then Image or Picture.
 After you have inserted the image into your webpage, you can edit its attributes in a
Properties dialog box or panel. You can change the image's height and width, put a border
around it, make it into a link, and add alternate text for users who can't see the image
5. Some web authoring packages use built-in file transfer protocol (FTP) capabilities to publish
the designed pages to a web server and allow the user to edit publish files while making realtime changes.
6. Web authoring software also allows users to create cascading style sheets (CSS) and web
design templates, create and add specialized scripts (including JavaScript applications) and even
automatically affix file properties like create date, author information, and copyright data
7. Themes: This feature provides a ways to accomplish a consistent look and feel for all pages
on web site at once
8. Task panes. A dropdown arrow allows you to switch
 Between various Panes offering options to work of different items.
9. Help Feature Most web authoring software also have a help area which users can use to find
information about the software.
Features and Qualities of a Good Website



The web must have a home page. This means a page at the top of any tiered structure or at
the centre of a web you design on paper.
You should name the home page Index.htm (or Index.html) in line with web server protocol.
Should not have too much on one page. It's better to use lots of pages with a small amount
of information on each.
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






Should have links to other areas on all pages for easy navigation through the website
Should load quickly
Should have a title and brief summary about the page
Should have date of last Update
Page (file) names should be eight characters or less. Although many servers and systems
now support long filenames, it isn't universal by any means.
Should have a feedback page or a link to the webmaster who will be the first contact for
your website’s visitors
Should have Simplicity = Elegance
Importance of a website



Making of a website favors publishing of data and information in a bid to create awareness
about something on the internet.
A website is an avenue for sharing knowledge through intercontinental interaction for
example through teleconferencing and discussion boards.
Website development enhances skill building such as writing, editing, layout and design;
providing motivation and pride of ownership
Limitations of a website
 Expenses: Websites are not easy to setup and maintain due to annual subscription to ISPs
or web hosts
 Timely updating issues: Information keeps on changing and this requires constant
revision and effecting changes as necessary.
 Copyright issues: It is a crime to publish information from copyrighted sources without
permission from the original authors.
Considerations for Webmasters
Webmasters should have the following points in mind when designing a website:
 They should be original and avoid violating copyright laws.
 The web pages should have valuable content for public consumption, tailored for consumer
requirements
 They should take into account the type of browsers the clients have: some versions may not
be able to display advanced webpage elements
 They should use minimum graphics
 They should limit the use of frames
Why should a school have a website
A website is a collection of hyperlinked html documents (web pages) with related information,
meant to creating awareness about something on the internet.
In a school setting, there is a lot of awareness required between the administration, staff,
students and parents.
Below are the major reasons why a school should have a website:
1. Making of a website quickens the publishing of information to the community such as abrupt
announcements, circulars, results, etc. Once uploaded, it will be already accessible to the
targeted readers
2. Through a website, the school can get feedbacks from the community through online user
comments and questions.
3. If students are involved in the Website development process, this enhances skill building
such as writing, editing, layout and design.
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4. A school website provides motivation and pride of ownership. This can be evidenced through
use of customized email. Eg xxx@jinjacol.sc.ug instead of xxx@yahoo.com
5. Information listed on a school website removes doubt. Information such as school fees, and
Everything presented at the site appears in a positive light, as compared to information from
other sites about the school which may be false.
6. If a school ha a website, they can use the web mail service to send parents and other
stakeholders items such as newsletters, remainders e.t.c
7. A website increases ways of contact. Once you have a website you can list your website
address on your business cards, report cards, and even the school signpost.
8. Internet today is being used 24 / 7 and is accessible from every house. People are becoming
highly dependent on the internet. By having a web presence, the market of the school
expands your significantly.
9. A school website helps students and parents to make a wise academic choice after using
the vast quantities of information about a given college or university.
In conclusion, a well-designed website is just as important a public relations tool as school catalogs
and brochures. If a school has web presence, it can be listed in web search engines and know
worldwide. Today everything you need is achieved at the click of a button.
SENIOR FOUR TERM ONE
TOPIC 10: DATABASES
10.1. Introduction to databases
A database is a collection of arranged data in a way that allows access, retrieval, and use of the
data. Sometimes referred to as database management systems (DBMS)
A database is a Collection of related data.
Database is a collection of records stored for a particular purpose. The data in a database are
arranged in columns and rows.
Database software tools are primarily used for storing, modifying, extracting, and searching for
information within a database.
Examples of data stored in a database
-students in a school
-mobile phone numbers
-account numbers in a bank
To work on a database, there is need for a database management system (DBMS)
A DBMS is a software that handles the storage, retrieval and updating of data in a computer.
Features of a DBMS
 Database objects such as tables, forms, reports, queries, modules and macros.

Importing and exporting functionalities.

Ability to identify data duplicates and redundancies
Functions of a DBMS
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To store, add, delete and update the data in the database
To provide various ways to enter and view the data in the database
Advantages of a DBMS
There is reduced data redundancy. DBMS helps in controlling having multiple copies of the same
data. By controlling redundancy, storage space is saved.
It ensures data
Importance of a database
 Databases provide an efficient way to store, retrieve and analyze data. While system files can
function similarly to databases, they are far less efficient.
 Databases are especially important for business and research.
 Computers can perform calculations far faster than humans, and they use programmed logic to
make decisions. However, computers are also capable of storing a tremendous amount of
information, and the amount of data computers can store continues to increase. Databases are
at the forefront of making this information available to programs and to computers.
 Most medium and large companies rely on databases for storing customer information. They
also use them to store accounting information.
 Some of the largest databases in the world store weather information. There are simply too
many weather data points for humans to analyze, and finding signs of small but significant
climate shifts would be impossible without databases.
Advantages of a DBMS
 There is reduced data redundancy. DBMS helps in controlling having multiple copies of the same
data. By controlling data redundancy, storage space is saved.
 It ensures data consistency. With consistency, when a data item which appears more than once
in the database is updated the DBMS automatically updates each occurrence of a data item in
the database. Consistency is a achieved by reducing redundancy.
 Easy data sharing. DBMS enables data to be shared by authorized users with ease.
 Ease of data update and retrieval. With the use of multiple tables and relationships in DBMSs,
data is easy to retrieve and update.
 DBMS have enhanced data security. DBMS protects database from unauthorized users by the
use of passwords.
 DBMSs allow simultaneous access by more than one user.
 DBMS provides for backup and recovery procedures. DBMSs provide for automatic creation of
data backup and restore if required.
Disadvantages of a DBMS
 They are complex to manage. The professional operation of a database system requires
appropriately trained staff
 A database system is a multi-use software which is often less efficient than specialised software
which is produced and optimised exactly for one problem.
 There are higher chances that some users may abuse the shared data.
 DBMS require sophisticated hardware, software and skilled personnel which is expensive.
 Data loss is significant in case of failures because all data is integrated into a single database.
EXAMPLES OF DATABASE SOFTWARE INCLUDE:

Microsoft access
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







Microsoft visual
Borland dBase
Lotus Approach
Corel paradox
Claris file maker pro etc
MySQL
Oracle
FileMaker.
Properties of objects
Access is an object oriented application — that is, it is made up of different components called
objects. Tables, fields, forms, reports and queries are a few examples of objects in an Access
database system.
Table.is a MS access object where data is stored in a database. In Access, data is stored in tables.
A table is a set of columns and rows, where each column referred to as a field. Each value in a field
represents a single type of data. Each row of a table is referred to as a record.
Query. Is a MS Access object used to retrieve specific data from your database and to answer
questions about your data. For example, you can use a query to find the names of the employees in
your database who live in a particular state.
Form. Ms access object that gives you the ability to choose the format and arrangement of fields.
You can use a form to enter, edit, and display data.
Report. Ms access object used to organize or summarize your data so you can print it or view it on
screen. You often use reports when you want to analyze your data or present your data to others.
Macros. Macros give you the ability to automate tasks. You can use a macro to add functionality to
a form, report, or control.
Modules. Like macros, modules give you the ability to automate tasks and add functionality to a
form, report, or control. Macros are created by choosing from a list of macro actions, whereas
modules are written in Visual Basic for Applications.
An object has certain characteristics associated with it, known as properties e.g. its name, size,
color etc. The properties of an object can usually be inspected and altered.
Right-clicking an object with the mouse generates a shortcut menu to its list of properties, along
with a list of the operations that may be carried out on it.
There are some common terms associated to databases that include the following.
i)
Field
In a database, a field is the entire column that contains similar data items for example, the
names column that contains each individual’s name is a field. It also applies to those of sex,
district and salary. Therefore these are referred to as the sex field, the name field, district field
and salary field respectively.
ii)
Record
A record is a set of entire data items in a row. In the above table if for example we consider the
data items in the second row, it contains Martin in the names field, m in the sex field, Kampala
in the district field and 120,000 in the allowance field. All this information can be described as a
record that pertains to Martin.
iii)
Field name
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Title for a column in a database table
For example the titles; names, sex, district, and allowance are field names. They are also
referred to as the field labels.
iv)
Data types
Defines the nature of data to be entered in a given field of the database table
A data/field type specifies the format to which the data items are stored. Different data items
are stored differently in a database. For example, not all numerals are numeric data types.
Microsoft Access supports up to nine different types of data. These could be text, memo,
number, date/time, currency, yes/no, OLE object, auto number, lookup or hyperlink field. The
table below summarizes the implications of each of these fields.
Field
Type/data
type
Auto Number
Currency
Date/time
Hyperlink
Text
Lookup wizard
Memo
Numbers
OLE
Yes/No
Data Stored
A number that is automatically assigned incrementally or
randomly to a particular record and decimal place
A numeric field that is automatically assigned a currency sign,
thousands separator and decimal places.
A date or time data types you can change the appearance of each
from the general tab.
Stores data types like internet address (e.g. www.cnn.com)
Any characters that will not be used for calculations for example
phone numbers
Stores values that are from an external table, query, or a list of
specific values
Whole sentences of up to 64,000 characters in length including
spaces
Any numerals that may be used in calculations for example
amounts.
Any linked object like a picture, sound, document or photograph.
A logical field that will need only a yes or a no, true or false, on
or off
v)
Field properties
Specifies how data in a table should be stored/handled/displayed.
A field property is the specific characteristic of a particular field. Field properties are specified
from the general tab on the data-table structure. They include field characteristics like field size,
caption, format, decimal places, and others. Field properties change depending on the type
specified. The table below summarizes some important field characteristics/properties.
Field property
Allow zero length
Caption
Decimal places
Implication
If set to yes, even an empty string will be accepted as a valid
entry in this field
Specifies a different name to be used as a field label instead of
the specified field name
Specifies the number of decimal places the figures should
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Default value
Field size
Format
Indexed
Required
Input mask
Validation
Rule/Validation
Text
.
have
Specifies the data entry value to be entered automatically for
each field unless changed
Specifies the maximum length of characters (including spaces)
any data item in this field should have.
Specifies the appearance of any data item in that particular
field samples of the supported formats are normally on the
drop-down list box that appears when you click in the format
box
Specifies whether the data in this field should be listed
chronologically and whether to allow duplicate data item.
If set to yes, this field cannot be set left blank during data
entry.
Specifies a specific template for entering data items in a
particular field.
The Validation Rule property is used in conjunction with
Validation Text to specify requirements for entered data. The
rule sets the conditions and the text specifies the warning
message that will be issued if the conditions are breached. For
example, you could specify that numbers entered into
a field must be in the range 1-500 and set up a message such
as “The value entered must be between 1 and 500”, which will
be displayed when a value outside this range is entered.
Introduction to Microsoft Access 2007
Introduction
A database is a collection of information that's related. Access allows you to
manage your information in one database file. Within Access there are four major areas: Tables,
Queries, Forms and Reports
• Tables store your data in your database
• Queries ask questions about information stored in your tables
• Forms allow you to view data stored in your tables
• Reports allow you to print data based on queries/tables that you have created
Creating a Database
1) Start Access
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2) Select Blank Database
3) In the File Name field enter a name for the database
4) Click Create
2
Microsoft Access automatically creates a new table in the database called
Table1. This is a temporary name until the table is saved.
Understanding the Views
There are 2 basic views when you work in a table: Design View and Datasheet View.
Design View is used to set the data types, insert or delete fields, and set the Primary key. Datasheet
View is used to enter the data for the records. By default, Access places you in Datasheet View.
To Switch to Design view:
1) Click the View button on the Home Ribbon
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2) Type a name for the table
3) Click OK
Before proceeding, it is important to understand common Microsoft Access Data
Types. (Explained in the table below)
To Enter Fields in a Table:
1) Type a name for the first field in the table
2) Press Enter
3) Select a data type
4) Press Enter
5) Type a description for the field
6) Press Enter
Continue this until all necessary fields have been entered into the table.
Note: The order that you enter the field names is the order the fields will appear in the
table and on a form.
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To View the Datasheet:
Click the View button on the Ribbon
Setting a Primary Key
The Primary Key is the unique identifier for each record in a table. Access will not allow duplicate
entries in a Primary Key field. By default, Access sets the first field in the table as the Primary Key
field. An example of a Primary Key would be your Social Security Number. This is something unique
about you and should not be duplicated.
To Set a Primary Key:
1) Switch to Design View
2) Position your cursor in the field you wish to set as the Primary Key
3) Click the Primary Key button on the Ribbon
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To Switch Back to Datasheet View to Enter your Records:
Click the View button on the Ribbon.
Entering Data in a Table
Once you have entered the fields and set the data types it is now time to enter the records in a
table.
To Enter Data in a Table:
1) Make sure you are in Datasheet View
2) Enter the data into the table by pressing the tab key to move from one cell to another
3) When you have completed the record (row), press Enter
When inputting data into the table, Access automatically saves the data after each new record.
Input Masks
An Input Mask is used to pre-format a field to “look/act” a certain way when a user inputs data.
Example: You could create an input mask for a Social Security Number field that
automatically inserts the dash.
The Input Mask data can either be stored in the table or simply displayed and not stored.
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To Create an Input Mask for a Field
1) Open a table in Design View
2) Click in a field for which you’d like to create an input mask
3) In the Field Properties section at the bottom of the screen, click in the
Input Mask line and notice the Build button that appears at the right end of the line (see below)
4)
5)
6)
6
7)
8)
Click the Build button
Select Input Mask
Click Next
Select a Placeholder character
Click Next
9) Select Without the symbols in the mask
10) Click Next
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11) Click Finish
Now, when entering data that has been formatted with an Input Mask, you do not have to type the
format into the record. 7
The following is an example of a table with a field that has been formatted with an Input Mask on
the Social Security Field.
Notice, the only thing that the user has to enter is the digits, not the symbols.
Navigating Records
Use the arrows at the bottom of the table to navigate among records.
You are able to navigate from the first record, previous record, next record, last record, and create
a new record (as shown in the picture below).
Notice that the total number of records in the table is shown at the right end of the navigation
arrows.
Sorting Records in a Table
By sorting your records in a table, you are easily able to view/locate records in your table.
To Sort Records in a Table:
1) Position your cursor in the field that you wish to sort by, by clicking on any record in that field.
2) Click either the Sort Ascending or Sort Descending icon
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Notice, the table above has been sorted by the Last Name field in ascending order.
8
Queries
You use Queries to view, change, and analyze data in different ways. You can also use them as a
source of records for forms and reports.
To Create a Query:
1) Click the Create tab on the Ribbon
2) Click Query Design icon
3) Double-click Create Query in Design View
4) Select the table that you would like to base your Query on
5) Click Add
6) Close the Show Table window
The table(s) will now be displayed in the upper part of the Query Design Screen by boxes containing
the tables’ fields.
7) Double click on the field names in the field list window which you would like to include in the
Query
Defining Criteria in the Query
In order to control which records are displayed, you must define criteria in a
Query. The most common type of Query is the Select Records Query which will be discussed
below.
To Define Criteria for your Query:
1) Position your cursor in the criteria row in the field for which you wish to define the criteria for
2) Enter the criteria
Example: To find all people it the table who live in Edison:
• Position your cursor in the criteria row of the City field
• Type Edison
• Click the Run Query button
Below is a picture of the results of the above query:
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The result of a query is called a recordset. A recordset can be sorted, printed or filtered in the
same manner as a table.
To Save the Query:
1) Click the Save Icon
2) Enter a name for the Query
3) Click OK
Note: When saving a select Query, you are saving the question that you are asking, not
the results that you see when you run the Query.
Creating a Form Using the Forms Wizard
A form is a database object that is used to enter or display data in a database.
To Create a Form Using the Wizard:
1) Navigate to the table you want to base the form on
2) Click Create on the Ribbon
3) Click Forms
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You are able to navigate using the navigation arrows at the bottom of the form.
Note: The form feeds the table. If you edit a record on the form, or create a new record,
that data will be passed to the table it is associated with.
To Enter a Record on the Form:
1) Click the View button on the Ribbon to switch from Layout View to Form
View
2) Enter the data for each field in the record, pressing the Enter key to move to the next field
3) Press Enter after you have entered data for the last field
This will send the record to the table.
11
Reports
Reports can be based on tables or queries and can be made with the Report Wizard.
To Create a Report Using the Report Wizard:
1) Click the Create tab on the Ribbon
2) Click the Report Wizard icon
3) Select the table or query upon which the report will be based
4) Select the fields that you want to include on the report by double clicking on them
5) Click Next
6) If you would like to add grouping to your report, select the field you wish to group by double
clicking on it (Example: City)
7) Click Next
8) Select a style for the report
9) Click Next
10) Type a title for the report
11) Click Finish
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To Print a Report
1) Open the report by double clicking on the object in the Navigation Pane
2) By default, the report opens in Print Preview.
To Adjust the Orientation:
Click the portrait or landscape icon on the Print Preview Ribbon
To Adjust the Margins
1) Click them Margins icon on the Print Preview Ribbon
2) Select a margin size
To Print the Report
1) Click the Print Icon on the Print Preview Ribbon
2) Select the Printer
3) Click OK
Summary of operators available in queries
Arithmetic Operators:
+
-(unary)
*
/
\
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Adds two operands.
e.g. [GCSEs]+[A levels]
Subtracts two operands.
e.g. [Value]-30
Changes sign of operand.
e.g. -6789
Multiplies two operands.
e.g.[Units]*[Unit Price]
Divides one operand by another.
e.g. [Total] / 2
Divides one integer operand by
another.
e.g. [Units] \ 4
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Mod
^
Comparison Operators:
=
>
<
>=
<=
<>
Returns remainder of division by
an integer.
e.g. [Units] Mod 5
Raises an operand to a power
(exponent).
e.g. [Value] ^ [Exponent]
Equal to.
e.g. =69
Greater than.
e.g. >69
Less than.
e.g. <69
Greater than or equal to.
e.g. >=69
Less than or equal to:
e.g. <=69
Not equal to.
e.g. 69<>96
Logical Operators:
Return the logical values True, False or Null.
And
Or
Not
Logical and.
Logical or.
Logical not.
Other Operators:
Is
Like
In
Between
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Used with Null to determine if a
value is Null or Not Null.
e.g. Is Not Null
Determines whether a string
value matches a “pattern”. Used
in conjunction with wildcards (see
Section 5.6).
e.g. Like”*JOHN*
Determines whether a string
value is equal to any of a list of
values.
e.g. In(“Collingwood”, “Grey”,
“Hatfield”)
Determines whether a numeric
value lies within a range of
values.
e.g. Between 30 and 50
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SENIOR FOUR TERM: TWO
TOPIC 11: ELEMENTARY PROGRAMMING
11.1. Introduction to programming
11.2. Developing a simple program
TOPIC 12: TRENDS IN COMPUTING
12.1. Computer integrity and security
Software integrity
Hardware integrity
Computer intrusion
Computer protection
 Use of surge protectors
 Use of UPS
 Use of strong passwords
 Use of antivirus
 Physical on site security i.e. computer locked in a room
 Use of fire walls
 Data encryption
Most common computer security threats and what you can do to protect yourself from
them.
A threat, in the context of computer security, refers to anything that has the potential to cause
serious harm to a computer system.
THREAT 1: VIRUS
A virus is a piece of software that can replicate itself and infect a computer without the permission
or knowledge of the user. A virus can only spread when it is transmitted by a user over a network or
the Internet, or through removable media such as CDs or memory sticks.
Prevention, detection and removal:
Antivirus software detects and eliminates known viruses.
THREAT #2: SPAM / SPIM / SPIT
SPAM is the sending of e-mail messages in bulk which are unnecessary. Email addresses are
collected from chat rooms, websites, newsgroups and by Trojans which harvest users’ address
books.
SPIM is spam sent via instant messaging systems such as Yahoo! Messenger, MSN Messenger and
ICQ.
SPIT is Spam over Internet Telephony. These are unwanted, automatically-dialed, pre-recorded
phone calls using Voice over Internet Protocol (VoIP).
Prevention, detection and removal:
ISPs attempt to choke the flood of spam by examining the information being sent and traffic
patterns. User systems may use spam filters to screen out email messages with suspect titles or
from suspect persons, as well email messages from blocked senders.
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THREAT #3: SPOOFING, PHISHING AND PHARMING
Spoofing is an attack in which a person or program masquerades (false show / pretence) as
another. A common tactic is to spoof a URL or website (see phishing).
Phishing is a common form of spoofing in which a phony web page is produced that looks just like
a legitimate web page. The phony page is on a server under the control of the attacker. Criminals
try to trick users into thinking that they are connected to a trusted site, and then harvest user
names, passwords, credit card details and other sensitive information.
Phishing is typically carried out by email or instant messaging. The email message claims to be from
a legitimate source but when the user clicks on the link provided, he or she lands on the fake web
page.
Pharming is an attack in which a hacker attempts to redirect a website's traffic to another, bogus
website. Pharming can be conducted either by changing the hosts file on a victim’s computer or by
exploitation of a vulnerability in DNS server software. DNS servers are computers responsible for
resolving Internet names into their real IP addresses — the servers are the “signposts” of the
Internet.
Prevention, detection and removal:
spoofing, phishing, and to a lesser extent, pharming, rely on tricking users rather than advanced
technology, the best way to handle these threats is through vigilance. Don’t open emails from
unknown sources or click on links embedded in suspect messages.
Check the security guidelines of websites such as PayPal so that you can distinguish between
legitimate and bogus emails.
THREAT #4: SPYWARE
Spyware is software that aids in gathering information about a person or organization without their
knowledge and that may send such information to another entity without the consumer's consent.
Spyware is software that is secretly installed on a computer without the user’s consent. It monitors
user activity or interferes with user control over a personal computer.
Prevention, detection and removal: Anti-spyware programs can combat spyware in two ways:
1
Real-time protection: these programs work just like anti-virus software. They scan all
incoming network traffic for spyware software and block any threats that are detected.
2
Detection and removal: users schedule daily, weekly, or monthly scans of their computer
to detect and remove any spyware software that has been installed. These antispyware programs
scan the contents of the Windows registry, operating system files, and programs installed on your
computer. They then provide a list of threats found, allowing the user to choose what to delete and
what to keep.
Some popular antispyware programs are Spybot - Search & Destroy, PC Tools’ Spyware Doctor, as
well as commercial offerings from Symantec, McAfee, and Zone Alarm.
THREAT #5: KEYSTROKE LOGGING (KEYLOGGING)
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A keylogger is a software program that is installed on a computer, often by a Trojan horse or
virus. Keyloggers capture and record user keystrokes. The data captured is then transmitted to a
remote computer.
Prevention, detection and removal:
For the time being, therefore, the best strategy is to use common sense and a combination of
several methods:



Monitoring which programs are running: a user should constantly be aware of which
programs are installed on his or her machine.
Antispyware: antispyware applications are able to detect many keyloggers and remove them.
Anti-keylogging software:keylogger detection software packages use “signatures” from a list
of all known keyloggers to identify and remove them.
THREAT #6: ADWARE
Adware is software which automatically plays, displays, or downloads advertisements to a
computer. The adware runs either after a software program has been installed on a computer or
while the application is being used. In some cases, adware is accepted by users in exchange for
using software free-of-charge. Not all adware is innocuous, however. Some types of adware are also
spyware and therefore a threat to privacy.
Prevention, detection and removal:
As adware is also often spyware or malware, programs have been developed to detect, quarantine,
and remove both spyware and adware. Ad-Aware and Spybot - Search & Destroy are two commonly
used programs.
THREAT #7: BOTNET
A Botnet (also called a “zombie army”) is a collection of software robots, or bots, that run
automated tasks over the Internet. The term “botnet” is generally used to refer to a distributed
network of compromised computers (called “zombie computers”). These “zombies” typically run
programs such as worms, Trojan horses, or backdoors.
Botnets are frequently used to launch Distributed Denial-of-Service (DDoS) attacks against websites.
Newer bots can automatically scan their environment and propagate themselves using vulnerabilities
and weak passwords.
Prevention, detection and removal:
Detection focuses on either the computer itself or the network. Both approaches use trial and error
to try to identify bot behavior patterns.
THREAT #8: WORM
A computer worm is a self-replicating, malicious software program. Unlike a virus, it does not
need to attach itself to an existing program or require user intervention to spread. It uses a network
to send copies of itself to other computers on the network.
Prevention, detection and removal:
Since worms spread by exploiting vulnerabilities in operating systems, computers should be kept
current with the latest security updates or “patches” from operating system vendors.
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To prevent infection, users need to be wary of opening unexpected emails and should not run
attached files or programs, or visit websites that are linked to such emails. Users should be
constantly on guard against phishing.
Antivirus and antispyware software, if kept up-to-date, are also helpful, as is the use of a firewall.
THREAT #9: TROJAN HORSE
A Trojan horse or Trojan is a piece of software which – like the Trojan Horse of Greek mythology
– conceals a payload (often malicious) while appearing to perform a legitimate action. Trojan horses
often install “backdoor programs” which allow hackers a secret way into a computer system.
Prevention, detection and removal:
Normally, antivirus software is able to detect and remove Trojan horses automatically. They may
also be deleted by clearing the temporary Internet files on a computer, or by finding the offending
file and deleting it manually (in safe mode).
THREAT #10: BLENDED THREAT
A blended threat is a threat that combines different malicious components, such as a worm, a
Trojan horse and a virus. In this way, a blended threat uses multiple techniques to attack and
propagate itself.
Prevention, detection and removal:
See respective entries for worm, Trojan horse and virus.
THREAT #11: DENIAL-OF-SERVICE ATTACK (DOS ATTACK)
As its name implies, a Denial-of-Service or DoS attack is an attempt to make a computer
resource such as a website or web service unavailable to users. One of the most common methods
of attack involves saturating the target (victim) machine with external communications requests.
Prevention, detection and removal:
Surviving an attack: The easiest way to survive an attack is to plan ahead. Set aside a separate
emergency block of IP addresses for critical servers with a separate route.
Firewalls: Firewalls follow simple rules to allow or deny protocols, ports or IP addresses. Some
firewalls offer a built-in emergency mode. If the number of incoming packets per second exceeds a
set value for more than the specified time, the firewall classifies it as a DoS attack and switches to
emergency mode. In this mode, all inbound traffic is blocked except previously established and
active connections, but outbound traffic is allowed.
Some DoS attacks are too advanced for today's firewalls. If there is an attack on port 80 (web
service), for example, firewalls cannot prevent the attack because they cannot distinguish between
good traffic and DoS traffic. Another problem is that firewalls are too deep in the network hierarchy.
Your router may be overwhelmed before the traffic even gets to your firewall.
Computer crime
It refers to any crime that involves a computer and a network. The computer may have been used
to carry out a crime, or it may be the target.
Computer crime is a form of crime where the Internet or computers are used as a medium to
commit crime.
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These include:
Hacking,
Denial of service attacks,
Unauthorized use of services
Cyber vandalism,
Copyright infringement,
Child pornography,
Fraud,
Money laundering, and counterfeiting,
Cyber terrorism,
Phishing,
Pharming,
Spoofing,
Malware such as viruses,
Identity theft and
Cyber stalking
Hacking is the activity of breaking into a computer system to gain unauthorized access to
information. The unauthorized revelation of passwords with intent to gain unauthorized access to
private communication of a user is one of widely known computer crimes. Another highly dangerous
computer crime is the hacking IP addresses in order to transact with a false identity, thus remaining
anonymous without carringout the criminal activities.
Phishing is the act of attempting to acquire sensitive information like user name password and
credit card details by distinguishing as a trustworthy source. Phishing is carried out through emails
or by luring the users to enter personal information through websites. Criminals often use websites
that have a look and fill of some popular webs which makes the users feel safe to enter their details
there.
Computer viruses are computer programs that can replicate themselves and harm computer
systems on a network without the knowledge of the system users. Viruses spread to other
computers through sharing infected network files, through the network as a transport medium, by
the means of removable devices like USB drives, DVDs, CDS. Computer viruses are all, forms of
malicious codes written with an aim to harm a computer system and destroy information. Writing
computer viruses is a criminal activity as virus infections can trash computer systems, thereby
destroying great amounts of critical data.
Cyber stalking; the use of communication technology e.g. the internet to stalk a person online.
The stalker sends threatening emails, spreads false information and accusation transmits to threats
on the internet and damages data and equipment. Cyber stalkers often target the users by
means of chartrooms, online forums and social networking websites to gather information
and harass the users on the basis of the information gathered ,obscene emails, abusive phone
calls and other such serious effects cyber stalking has made it a type of computer crime.
Identity theft involves stealing money and obtaining other benefits by using another person’s
identity. It is the act of pretending to be someone else by using someone else’s identity as ones’
own. Financial identity theft involves the use of false identity to obtain goods and services and a
commercial identity theft is the using of someone else’s business name or credit card details for
commercial purposes. Identity cloning is the use of another user’s information to pose as a false
user. Illegal migration, terrorism and black mail are often made possible by means of identity theft.
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Cyber extortion is a form of cyberterrorism in which a website, e-mail server, or computer system is
subjected to repeated denial of service or other attacks by malicious hackers, who demand money
in return for promising to stop the attacks.
Cyber terrorism in general, can be defined as an act of terrorism committed through the use of
cyberspace or computer resources
Spam
Spam, or the unsolicited sending of bulk email for commercial purposes, is unlawful in some
jurisdictions. While anti-spam laws are relatively new, limits on unsolicited electronic communications
have existed for some time.
Fraud
Computer fraud is any dishonest misrepresentation of fact intended to let another to do or refrain
from doing something which causes loss.
Other forms of fraud may be facilitated using computer systems, including bank fraud, identity theft,
extortion, and theft of classified information
Drug trafficking
Drug traffickers are increasingly taking advantage of the Internet to sell their illegal substances
through encrypted e-mail and other Internet Technology. Some drug traffickers arrange deals at
internet cafes, use courier Web sites to track illegal packages of pills, and swap recipes for
amphetamines in restricted-access chat rooms.
Cyber Crime” describes criminal activities committed through the use of electronic communications
media. or
Cyber crime can mean any criminal activity that takes place over the Internet. Examples include
fraud,
How to control computer crime
Just like any sort of crime, common sense is your most valuable ally when dealing with cyber
criminals, Never open suspicious documents.
Don't give out personal information to people you don't know. And be wary when approached with a
suspicious proposition.
Learn about cyber crime and talk to your family about how to identify scams.
Never give out your personal information to anyone you do not know on the Web.
Use a firewall to protect your computer from hackers. Most security software comes with a firewall.
Turn on the firewall that comes with your router as well.
Purchase and install anti-virus software such as McAfee or Norton Anti-Virus. AVG offers free antivirus protection if you do not wish to purchase software.
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Shop only at secure websites. Look for a Truste or VeriSign seal when checking out. Never give your
credit card information to a website that looks suspicious or to someone you don't know.
Use strong passwords on your accounts that are difficult to guess. Include both letters and numerals
in your passwords. Never use a word that is easy to guess -- like your wife's name.
Keep watch over your children and how they use the Internet. Install parental control software to
limit where they can surf.
12.2. Computer Ethics and integrity
 Computer ethics refers to a set of moral principles that regulate the use of computers.
 Or the human values and moral conduct relating to right and wrong behavior/decisions made
when using computers.
 Computer integrity refers to steadfast loyalty to a strict moral or principled set of laws regarding
computer use
Some of the Computer ethics and integrity that should be put in mind when using
computers include:
1. Respect the privacy of others. Do not in any way examine or change files or passwords
belonging to others. Do not violate the privacy of individuals or organizations.
2. Respect the integrity of the computing systems. Do not develop or use programs that
invade, damage, or alter computing systems or software. Do not in any way harass other users.
3. Always identify the user accurately. Never use someone else's account. Do not use
fraudulent means to avoid accounting for the use of computing services.
4. Respect copyrights and licenses. To copy a licensed computer program is illegal; it is indeed
theft.
5. Respect the intellectual property of others. Individual programming assignments are
expected to be done by individual students; do not take another's work or ideas to call your
own.
6. Exhibit responsible, sensible use of computer hardware, software, and data.
SENIOR FOUR TERM: THREE
TOPIC 12: TRENDS IN COMPUTING (…..continued)
12.5. System analysis
I.
II.
Systems analysis is the dissection of a system into its component pieces to study how those
component pieces interact and work.
System analyst is a person who researches problems, plan solutions, recommends software’s
and systems at least at the functional levels and co-ordinates development to meet business or
other requirements.
A system analyst does the following.
1. Identifies, understands, and plans for the organist ion planned systems, and ensure that new
technical requirements are properly intergraded with existing processes and skill sets.
2. Plans a new system from the beginning to the end.
3. Interacts with the internal users and customers to learn and document requirements that
shall be used to produce business requirements documents.
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4. Write technical requirements from a critical phase.
5. Interact with designers to understand software limitations.
6. Help programmers during system development; provide use cases, flowcharts or even data
base design.
7. Perform system setting.
8. Deploy the completed system.
9. Document requirements or contribute to user manuals.
10. Whenever a development process is conducted, the system analyst is responsible for
designing components and providing that information to the developer.
Computer professionals
A computer professional or specialist is a person who works in the field of information technology.
Below is a summary of common computer professionals.
Web developers. These design and create websites. They are responsible for the look of the site,
the site’s technical aspects like performance and capacity.
Software developers. These are the creative minds behind computer programs. Some develop
applications that allow people to do specific tasks on a computer or another device.
systems administrators. Systems administrators in organizations ensure that all computer
systems are well configured and are working properly.
Network administrators. Computer networks are critical parts of almost every organization.
Network administrators are responsible for the day the day-to-day operation of these networks.
Information security analysts. These plan and carry out security measures to protect an
organization’s computer networks and systems. They are important in averting cyber attacks.
Database administrators. These use specialized software to store and organize data. They make
sure that data are available to users and are secure from unauthorized access.
System analysts. These study an organization’s current computer systems and procedures and
design information systems solutions to help the organization operate more efficiently and
effectively.
IT support specialists. IT support specialists provide help and advice to people and organizations
using computer software or equipment. They assist computer users who are having computer
problems.
Programmers. These write and test code that allows computer applications and software
programs to function properly.
Data analyst. A data analyst inspects, cleans, transforms and models data with the aim of
discovering useful information, suggesting conclusions and supporting decision-making.
Computer technician. This is a person who repairs and maintains computers and servers. The
technician’s responsibilities may extend to include installing and updating software packages etc.
Network architects. Network architects design and build data communication networks, including
local area networks, wide area networks and intranets.
12.3 Computers and society
Impact of computer on society
 Increased interactions or collaborations through emails, chat rooms, video conferencing etc
 Increased inventions innovations such as wireless keyboards, wires mouse
 Improved and sustained quality goods and services due to automated production
 Improved corporate image ie firms use ICTs to create logos and headed letters
 Many IT products for the disabled are being created i.e Baillie Keyboards
 Increased investment opportunities in commercial telephone centers, internet cafes, chat room
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 Creation of jobs that require high skills e.g. IT technicians, computer operators, website
designers, software developers
Negative implications of computers
 Widens the gap between the information rich and the information poor as the rich produce
products faster on the market than the poor
 Isolates older people since they do not find it easy to learn ad use ICT gadgets very fast
 Computers avails people with lots of good and bad information from the internet
 Increased learning instability as people are compelled to learn new technologies that come up
every now and then
 Reduced physical activities which in turn creates lots of health problem e.g.. eye strain, back
problems etc
 Erosion of individual privacy as more and more people’s private data is being stored in
databases where others can access any time
 Increased unemployment as less skilled people get retrenched and their jobs taken over by
more effective ITs like Robots in factories
 Addiction to computer usage (internet, music, Games etc) is on increase
 The initial maintenance and ICT facilities is very high e.g internet access bills
 Virus threats as there is easy spread of virus through networking
 Increased computer crimes i.e. Hacking, phishing, software piracy etc
12.4. Emerging technologies
 Artificial intelligence
 Digital forensics is a branch of forensic science encompassing recovery and investigation of
material found in digital devices, often in relation to computer crime
 Artificial reality: artificial or simulated reality that is generated in 3D by a computer and
commonly known as VR, .artificial reality, virtual environments
III.
Expert system is a computer system that imitates the decision making ability of a human
expert. Expert systems are designed to solve complex problems by reasoning about knowledge,
like an expert, and not by following the procedure of a developer as is the case in conversional
programming. The first expert systems were created in the 1970’s.
IV.
Artificial intelligence (AI) is technology and a branch of computer science that studies and
develops intelligent machines and software.
Trial Qn:
State examples of data threats and give ways of curbing these threats.
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