Basic Computing Simplified
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INTRODUCTION TO THE COMPUTER
Definition:
1. A computer is an automatic electronic device that inputs data, processes, stores it and output meaningful
information.
2. A computer is an automatic electronic device that helps in data processing tasks.
Data refers to a collection of raw facts or unprocessed information while Information refers to
data that has been processed into a meaningful form.
A computer follows a basic logical structure and performs the following basic operations for
converting raw input data into useful information.
a. Input. The process of entering data and instructions into the computer system
b. Processing Data. Performing arithmetic, and logical operations on data in order to convert
them into useful information.
c. Store Data. Saving data and instructions so that they are available for processing as and
when required.
d. Output Information. The process of producing useful information or results for the user,
such as a printed report or visual display.
e. Control of the workflow. Directing the manner and sequence in which all of the above
operations are performed.
Modern computers are electronic and digital. The actual device (wires, transistors and circuits
among others) is called the Hardware meanwhile the instructions/programs and data are called
Software.
The term hardware refers to the physical (tangible) components that you see. E.g. CPU (Central
Processing Unit), Monitor, Keyboard, Mouse, Printer, etc.
Software, on the other hand refers to sets of instructions/programs used in the running of the
computer hardware. E.g. Microsoft Windows 95, 2000, XP, Microsoft Excel, Publisher,
PowerPoint, etc.
Input
Data is entered via
keyboard, mouse,
microphone, etc
Processing
Storage
The information is digitized,
The information is
becoming a simple code that
the computer can store
stored as a part of the
computer’s memory
Output
Information is shared via
monitor, printer, speakers or
projector
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EVOLUTION AND GENERATIONS OF COMPUTERS
When we analyze critically, the evolution and generations of computers include:
 The origin – when and how they started.
 Personnel involved. I.e. the brains behind the inventions and changes up to date.
 Changes in physical size, costs, programs, accessories, programming languages and procedures.
 Emission of heat.
 User friendliness.
The invention of the abacus (Origin of calculation)
The abacus was a series of beads lined up in a tiny strong rope which was able to make people
calculate with little difficulty in their transactions. This was introduced in the Middle East
(China) in 500 BC. It remained the fastest form of calculation until in the middle of the 17th
Century. Each bead on the abacus below the middle bar stands for one unit and each bead above
the middle bar stands for 5 units.
Napier’s bones
Napier’s bones was developed by John Napier, a Scottish mathematician in the 17th century. It
helped in multiplication and division.
Pascal’s Arithmetic engine.
In 1642, a French scientist and philosopher named Blaise Pascal (1623-1666) invented the first
mechanical calculator. The machine comprised a system of gears and wheels that could add and
subtract decimal numbers. He named it Pasculine.
Leibniz wheel
In 1671, a German mathematician and philosopher Gottfried Wilhelm Leibniz (1646-1716)
came up with a similar but more advanced machine. He made an improvement on Pascal’s
machine. Instead of using wheels, it had a “stepped drum” (a cylinder with teeth of increasing
length around its edge), an innovation that survived in mechanical era for 300 years.
He is also remembered for inventing the binary code.
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Jacquard’s Loom
In 1801, Joseph Marie Jacquard invented a weaving loom with an automatic card reader, which
allowed it to use punched cards to program patterns of colors in woven fabric.
Charles Babbage’s Analytical difference engine.
Charles Babbage (1791-1871), regarded as the father of computing, developed an analytical
engine in 1832 that could feed in numbers and store them while complex calculations were
taking place. The output was on printed media. Before he could finish up the analytical engine,
he again came up with another design (the difference engine) that would use stored information.
While searching for other means to support his project, Babbage met ADA AUGUSTA, Lady
Lovelace. She was a very enthusiastic mathematician. She became the first computer
programmer, writing out the sequence of instructions for the analytical engine. Babbage never
finished any of his engines and Ada died quite young.
Hollerith’s tabulator.
Dr. Herman Hollerith (1860-1929) built one of the world’s first practical calculating machines
which was called the tabulator. His tabulator was used to compile the census data of the US.
By 1880s, the population of the United States had grown so much that it became hard to come up
with the statistics. The census took 7 ½ years to be analyzed. Dr. Hollerith then used his
tabulator to tally the 1890 census in only six weeks and completed the full analysis in just 2 ½
years. The Information was stored on punched cards and paper tapes.
He later left the census bureau and set up the Tabulating Machine Company in 1896 to
manufacture it commercially.
A few years later, it changed its name to the Computing Tabulating Recording (CTR)
Company and then in 1924, the company was named IBM (International Business Machine)
company
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COMPUTER GENERATIONS
Computer generations are the various stages through which computers have undergone.
First Generation (1940 – 1956)
In this generation, computers possessed the following characteristics:
 Use of vacuum tubes for internal operations.
 They were very expensive.
 They consumed a great amount of electricity.
 Use of punched cards for input and output was displayed on print outs.
 Use of magnetic drums for memory/storage.
 Very low processing speed compared to the next generations.
 Generated a lot of noise and heat during processing. Vacuum tubes produced a lot of light
which is typical of heat.
 They were very big in terms of physical size.
 They had relatively very limited storage capacities measuring in terms of bytes and kilobytes.
 They had no operating systems
 They had very limited usage as a result of very high cost of implications involved.
Examples of first generation computers include: The UNIVAC (Universal Automatic Computer,
EDVAC (Electronic Discrete Valuable Arithmetic Computer) and ENIAC (Electronic
Numerical Integrator and Calculator)
Second Generation (1956 – 1964)
The following features identify computers in this generation:
 Use of transistors for internal operation as opposed to vacuum tubes of the first generation.
 Use of magnetic tapes and disks for data backups. These were the first computers to store
instructions in their memory.
 Emission of less heat and noise compared to the first generation.
 Increase in processing speeds and reliability
 Reduction in sizes and costs of computer hardware and software.
 Use of microcomputers
 Introduction of interpreter programs as an interface between the user and the computer
system.
 Use of low level languages during programming. Mnemonic codes or abbreviations
(assembly languages) were used.
 Use of punched cards for input and printouts for output.
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Third Generation (1965 – 1970)
The most outstanding characteristics of third generation computers are:
 Introduction of Integrated Circuits (ICs) chips for internal operations
 Increased capacities of RAM, ROM and secondary storage devices.
 Reduction in the general physical size and cost of computers.
 Introduction of machine independent languages (High Level Languages, HLL) FORTRAN,
BASIC, etc. for programming.
 Introduction of microcomputers and multitasking
 Introduction of computer networking
 Use of operating systems for better interface, booting and general system management.
 Improvement in processing speeds, reliability and memory capacity compared to the first
generation.
Fourth Generation (1971 to present)
Computers in the 4th generation have the following characteristics:
 Introduction of Large Scale Integration (LSI), Very Large Scale Integration (VLSI) and
Grand Scale Integration (GSI). E.g. Pentium I, II, III & IV.
 Development of super and mainframe computers.
 Development of expert systems.
 Operating systems became more user friendly.
 More use of computers in business and domestic works.
 Introduction of query languages, report generators and application generators.
 Software tools performed tasks and leaving the computer to determine what to be done.
 Programming was done in High Level Languages (HLL). E.g. Structured Query Language
(SQL)
 Use of microprocessors.
 Development of Graphical User Interfaces (GUIs).
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Fifth Generation (Present and beyond)
This generation is assumed to be at its early stages. The fully developed fifth generation
computers are expected to have the following characteristics:
 Use of Very Very High Level Languages (VVHLL)
 Introduction of Ultra Large Scale Integration technology
 Use of natural interfaces like cyber world.
 Computer tools becoming more user friendly. E.g. interactive applications, databases,
spreadsheets, word processing, etc.
 Increased use of hybrid and neurologic systems.
 Computer use and programming are expected to be more and purely interactive (conversational)
 Use of parallel processing and superconductors to process multiple instructions to make
artificial intelligence a reality.
 Use of voice recognition devices
Other future generation of computers
Two major innovations are in the experimental stage; DNA computers and Optical computers.
With the DNA (Deoxyribonucleic Acid) computing, information can be written onto individual
DNA molecules. They process data in parallel and potentially twice as fast as today’s fastest
supercomputers.
Optoelectronic computers use beams of light instead of electrons. They are expected to process
information several times faster than the current computers.
Revision Questions
UCE 2009
3. Which of the following characteristics will be associated with future computers?
A. Expensive computers
B. Advanced robotics
C. Big sized system units
D. Inadequate storage systems
24. c) What electronic technology characterized each of the four generations of computers?
i) First generation
ii) Second generation
iii) Third generation
iv) Fourth generation
UCE 2008
21. a) Describe the term evolution of computers
b) Mention four characteristics of the first generation computers
c) How do the second generation computers differ from fifth generation computers? List down
four differences.
29. What are the possible characteristics of the future generation of computers?
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UCE 2007
1. The scientific milestone of using Integrated Circuits (IC) was a characteristic of the
A. First generation
B. Second generation
C.. Third generation
D. Fourth generation
2. What major invention defined the second generation of computers?
A. Magnetic cores
B. Machine language
C. Microprocessor
D. Transistor
28. Reasonably predict the future in computing; from the perspective of the past to the
present developments in the technology and use of computers.
1.
2.
3.
4.
5.
6.
7.
CHARACTERISTICS OF COMPUTERS
Speed. Computers are fast in processing data compared to the manual system. Their speed is
measured in Millions of Instructions Per Second (MIPs).
Diligence. Computers are capable of performing repetitive tasks over and over without
making any error, getting tired or bored.
Accuracy. Computers are perfect in performing tasks as compared to the manual system.
They are capable of detecting mistakes and correcting them once made by users. Hence
Garbage In Garbage Out (GIGO). This means when you input wrong data, you get wrong
information and vice versa.
Storage/Memory. Computers are capable of holding data for a long period of time without
losing or forgetting it.
Versatility. A computer is able to perform different tasks at the same time. Different
programs can be installed into a computer to create different programs. E.g. playing music,
computerized accounting, map drawing, typesetting documents, etc.
Automation. Computers receive instructions and work on their own automatically. They do
not need any supervision in order to perform programmed routines.
Artificial intelligence (AI). Computers are very intelligent devices that can receive, respond
and give appropriate response. This basically depends on the programs installed in them.
Uses/Advantages/application of Computers
1. Business. A computer is used in business for purposes such as e-commerce and e-business
transactions (buying and selling of goods, services, and works online). E.g. by distributing,
buying, selling and marketing products and services online.
2. Banking. Computers help banking institutions and individual customers to easily get access
to transfer and depositing of funds.
ATM machines are making it even easier for customers to deal with banks.
3. Insurance. Insurance companies are maintaining a database of all clients with information
showing Survival benefits, starting date of policies, Interests due, etc.
4. Education and training. Computer education is rapidly increasing with many universities,
colleges and public libraries online with websites to make easy access to educational
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information. Trainers also use computers to provide Computer based training and e-learning
courses. E.g. Computer Aided Learning (CAL) and Computer Aided Instruction (CAI)
5. Library services. Computers help library personnel to easily access and keep updated
records of books and other library materials.
6. In schools, universities and other educational institutions, computers are used to prepare a
database about performance of students.
7. Transport and communication. Computers are also used in transport and communication to
track movement of planes and trains, make reservations for travelers, hotels, send and receive
messages (e-mail SMS) over the internet.
8. Domestic and entertainment. Computers are used for recreation and entertainment purposes
like playing of computer games, listening to music, watching movies, etc.
9. Computers are used by musicians to make music productions
10. Industries. Computers are used in manufacturing processes such as use of robots to handle
tasks that are to be performed by humans.
11. Research. Computers are used by scientists for research purposes like introduction of new
drugs, exploring the space, etc.
12. Military organizations also use computers to locate enemy positions and direct missiles.
13. Meteorologists use computers for making weather forecast. I.e. predicting weather changes.
14. Hospitals. Doctors use computers to keep health details of patients, make medical tests, drug
prescription and carrying out sensitive operations on sensitive body parts like the brain, heart,
kidney, etc.
15. Revenue authorities keep records of tax payers and make tax assessments using computers
16. Bureaus of statistics also use computers to process and interpret statistical data such as
health, income, population among others.
17. Marketing. Computers are used in marketing for advertisement such as creating and
designing graphics, newsletters, brochures and draft press release. There are computerized
catalogues that provide access to product information and permit direct entry of orders to be
filled by customers.
18. Accountants use computers to keep financial records, make financial statements and
invoices.
19. Offices. Computers are used in modern offices to create documents, spreadsheets, databases,
presentations among others.
20. Engineering Design. Computers are widely used in engineering purposes. One of major
areas is CAD (Computer aided design) that helps in design of Ships, Buildings, Bridges,
Airplanes, planning towns, designing buildings, determining a range of buildings on a site
using both 2D and 3D drawings.
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21. Government. The government uses computers to prepare budgets, compute sales tax, income
tax, voters’ lists, driving licensing systems
22. Law enforcement agencies. Information stored on computers such as fingerprints, images
and other identification details help law enforcers to carry out criminal investigations.
Revision questions:
1. Match the following generations of computers with the technology used to develop them:
Generation
1st generation
2nd generation
3rd generation
4th generation
5th generation
Technology
Artificial intelligence
Very large integrated circuits
Transistors
Vacuum tubes
Integrated circuits
2.
3.
4.
5.
6.
Identify and explain at least five areas where computers are used in day to day activities
What were the characteristics of the first generation computers?
Who developed the analytical engine?
What is artificial intelligence?
Write the following initials in full:
a) ENIAC
b) VLSI
c) IC
7. Using the abacus, represent 5,780
8. Match the following computer application areas with the role played by computers in each
case.
Area of application
Role
Supermarket
Matching fingerprints
Hospital
Entertainment
Bank
Stock control
Hotel
Booking rooms
Home
Analyzing academic data
School
manufacturing process control
Industry
Life support machines
Police station
processing cheques
Negative impacts of computers
1. Disposal of damaged computer systems is hard since they cannot be decomposed but can
cause damage to the environment.
2. Long usage of computers without protective gears can lead to eyesight impairment
3. Computer systems are very delicate and they require experts knowledgeable in timely
maintenance and repairs.
4. There is high cost incurred in computer maintenance and repairs.
5. Computer systems require electric power in order to operate effectively which may not be
available in some places
6. Acquisition of computer systems are also expensive.
7. Computer systems require literacy in order to learn.
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8. Computer technology has encouraged forgery and conning of people’s property and loss
of lives as well.
9. The invention of computer technology has caused unemployment to many employees
since most organizations are using computers to reduce their workforce.
10. Secrecy is limited since computer technology can detect and penetrate virtually every
information storage using experts knowledge.
11. It is encouraging immorality through pornographic technology leading to decline in
moralities.
12. Viruses can spread through the internet into your system and may destroy your data or
information from the whole system.
13. E- Commerce has caused business irregularities since a commodity can be accessed and
purchased online and a different product may be delivered instead.
Revision Questions
UCE 2006
28. Suggest reasons why there is an increase in the use of computers in most
organizations in Uganda today.
UCE 2009
29. Suggest ways in which computers can be used in business and industry in Uganda
UCE 2008
27. “Computers are a necessary requirement.” How do computers affect people in
everyday life?
Limitations of computers
Much as computers are advantageous in our daily life, it also has limitations as
experience has shown.
1. Accuracy and correctness of programs. A computer operates basing on the program code set
by programmers; so the accuracy and correctness of the code leads to a right solution whereas the
incorrectness of the code leads to wrong solution.
2. Data accuracy and correctness. If a user feeds wrong data into the computer, the computer will
automatically output wrong information. Hence, GIGO – “Garbage In Garbage Out”
3. Experience. A computer cannot learn from past mistakes or correctness
4. Alternative. Computers do not have the ability to try other alternatives or options.
The concept of data and information
Data refers to a collection of raw facts, figures and symbols. Data can also be defined an
unprocessed information. Examples of data include: Hours worked by an employee, sales figure
for a day, etc.
Data can further be classified in two ways:
Primary data/Direct data: This is data which originates from the source. That is – first hand
data.
Secondary data. This is data that comes in a more roundabout way. It is data that has already
been researched. Examples include: Text books, magazines, newspapers, etc.
Other forms of data include: currency (data expresses in monetary value), number (0-9), Memo,
text (data from letters of alphabet or combination of alphabet and numbers), date/time, image,
voice, etc.
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Data processing methods include:
 Manual method; this is the use of human beings for data processing
 Mechanical; this involves the use of mechanical typewriters, abacuses, slide rules, etc
 Electronic data processing
 Electro – mechanical data processing
Information:
This is data that has been processed into a meaningful and useful form
Levels of information
 Strategic information
 Tactical information
 Operational information
Types of information
 Past information
 Present information
 Future information
 Strategic information
 Tactical information
 Operational information
The monetary value placed on information depends on:
 The accuracy of information
 Its intended purpose
Good information can do one or all of the following:
 Reduce cost
 Eliminate losses
 Lead to a more efficient use of resources
 Provide more management and accurate decision making
Qualities of a good information
 Timeliness. Having data at the right time
 Cost effectiveness. Having data which is within the means of a firm
 Completeness/comprehensiveness. Having information that is not lacking in any form
 Relevancy. Having data that is free from errors and doubts.
 Must be through an appropriate channel; i.e. a channel which is noise free
 User specific or easily attached to the user. It must be properly qualified or structured
 Accuracy. This is all embracing; i.e. time accuracy, cost accuracy, etc.
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INFORMATION & COMMUNICATION TECHNOLOGY (ICT) AND THE SOCIETY
ICT is the technology required for information processing, in particular, the use of electronic
computers, communication devices and software applications to convert, store, protect,
process, transmit and retrieve data and information.
ICT/IT can also refer to all computerized gadgets and devices capable of sending and
receiving of information.
ICT/IT can also be referred to as the study, design, development, implementation, and
management of computer based information systems, particularly software applications and
computer hardware.
Computers and communication have brought and is still bringing changes in our lives.
Therefore, it is very common to come across the following concepts:
 Information technology
 The communication revolution/telephone revolution
 Internet revolution
 Multimedia (data, sound & video)
 The binary age
 Information society
 The information super highway/ “Information” /I – Way/ Data – Way
 The digital age/Dot age, etc.
The need for better ways of doing things has caused more research for the best technologies,
more reliable information and best communication means hence the following concepts:
 Telecommunication. This refers to the use of electromagnetic systems for
communication over long distances. Such systems/devices include: Radio broadcast,
TVs, Telephones & cable TVs, etc.
 Information. Information refers to the knowledge obtained from reading,
investigation, study or research. It is a process whereby information is exchanged
between individuals using symbols, signs or verbal interactions.
 Communication. This is the electronic transfer of data from one place to another.
 Technology. It is the use of scientific knowledge, experience and resources to create
processed products that fulfil human needs.
Whereas old technologies of ICT/IT such as newspapers, recordings, radio, paper printed
photographs, film, television are fading, new technologies such as satellites, cellular
phones, compact discs, e-mails, internet, data, warehouses & databases, video
conferencing, fiber optic (for communication media), fax machines and computers have
come in place to replace the old technologies.
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Impacts/advantages of ICT/IT on our society
1. It has led to increased interaction through e-mails, chat rooms, video conferencing, etc.
2. It has led to increased sharing and access to common databases within and outside organizations
through networking.
3. In education, it has helped students, teachers and researchers to get access to relevant
information.
4. Processing of data is much faster on a computer. E.g. calculating an annual budget on a
spreadsheet.
5. Repetitive processing can be best done using computerized machinery e.g. Use of robots in
industries.
6. Increased access to information through DBMS (Database management Systems) thus making
research easier. E.g. finding a patient’s record in a doctor’s surgery can be done in seconds on a
computerized database systems.
7. Data storage capacity is almost unlimited in a computer system. For instance, large quantities of
data can be stored on media such as CDs or DVDs instead of paper and large filing cabinets.
8. Data communication is fast as data can be transmitted over a network in just a few seconds.
9. Data can be output on a computer in a variety of different formats. E.g. annual sales figures can
be printed as a spreadsheet, displayed as a graph or as a multimedia presentation involving text,
sound, graphics and animations.
10. It has led to increased inventions and innovations.
11. It has led to increased technology in management fields.
12. It has improved and sustained quality goods and services
13. It has increase efficiency and effectiveness, leading to increased productivity.
14. It has increased investment opportunities in commercial tele-centers, internet cafes, chat rooms, etc.
15. It has improved on the standard of living as people get shorter working hours.
16. Highly skilled jobs are being created like programing, systems analysis, software engineering,
etc. as a result of ICT/IT.
17. Many IT products are being made available for the disabled.
18. It has reduced cost of production through less demanding ICTs.
19. It has improved the corporate image.
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Negative impacts of ICT
1. Older generations find it difficult to catch up with the changing technologies today.
2. It bombards people with too much information especially through the internet both good and bad.
3. It has increased instability as people get compelled to learn new things every day.
4. It causes health problems such as eye sight losses, repetitive strain injury, etc.
5. Moral degeneration is caused through access to pornographic materials on the internet.
6. It has widened the gap between the rich and the poor as the rich use ICTs to produce faster and
flood the market.
7. It has eroded individual privacy as more data stored on databases can be accessed anytime.
8. It causes addiction to computers by young people. E.g. computer games.
9. Increased crimes through forgery and piracy.
10. Virus threats make data stored on computers very unsecure
11. Initial cost and maintenance costs of ICT is very high
12. ICT isolates man and erodes the social aspect of work as some people prefer performing official
duties from their homes.
13. ICT causes unemployment to the less skilled people.
14. People are rejecting the casual routine of even shopping for online shopping instead.
15. Depletion of resources is caused since printing is done on papers that requires many trees to be
cut down to be processed into paper thus even increasing global warming.
INFORMATION TECHNOLOGY
Is the development, implementation and management of computer based information systems,
mostly software applications and hardware.
IT professionals perform a variety of functions that range from installing applications to
designing complex computer networks and information databases.
Duties that IT professionals perform
 Data management
 Networking
 Engineering computer hardware
 Database and software design
 Management and administration of entire systems
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Components of Information Technology
 Computers. These are very important in order to input data, process, store and output
information. They are divided into four categories. E.g. Super computers, mainframe
computers, mini and microcomputers.
 Servers. A server is a central host computer that provides services to the client computers.
These services include storage and retrieval of information.
 Database Management Systems (DBMS). This is basically a set of software programs which
manages the storage, retrieval and organization of information in a computer.
 Networking. This refers to the interconnection of computers and peripherals through telephone
lines or other communication channels to share information and resources (such as printers,
scanners, etc.)
 Network security and cryptography. This refers to the provisions made in a computer
network to prevent unauthorized usage of information. It is also helpful in providing protection
from computer hacking at the cyber boundaries of an organization.
Careers in Information Technology
Technical support agent. To help customers resolve hardware and software issues.
Network administrator. Responsible for setting up computer-to-computer interactions, as well as
workstations and mobile devices.
Database engineer. To design databases for handling day-to-day operations like customer
account, order tracking, human resources and financial information.
Video game development. This requires individuals and teams who specialize in art, design, 3D
modelling, project management. Music composition and more.
Technical writer. Writing text books, manuals and training courses dealing with computer
hardware and software that conveys the needed information to the end-user.
Computer Literacy.
This refers to having knowledge and understanding of computers and their uses.
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THE COMPUTER LABORATORY
A computer laboratory refers to a room in which computers are kept and used for
learning purposes.
The following factors must be considered when preparing a computer laboratory:
i.
ii.
iii.
iv.
Security of computer hardware and software
Reliability of the source of power
Number of computers to be setup
Maximum number of users
Safety precautions, care and maintenance to be taken while in a computer laboratory
1) Avoid abrupt switching off your computer; always follow the right procedures of shutting
down your computer.
2) Ensure that you protect your computers using up-to-date antivirus to avoid viruses from
infecting your computer memory.
3) Avoid or scan foreign storage media before using them in your computer. E.g. floppy
diskettes, flash disks, etc.
4) Avoid opening programs you are not familiar with.
5) Avoid eating or drinking while using a computer since liquids can pour on the computer
hardware. E.g. mouse, keyboard among others.
6) Carry out open cleaning of computers regularly to ensure its effective functioning.
Remember to blow off dust inside your system.
7) Always cover your computer with a cloth or any other cover to avoid dust and moisture
form spoiling it.
8) Avoid downloading cache files or unsecure games from the internet since they are not safe.
9) Endeavor to use Universal Power Supply (UPS) or stabilizers to control power instabilities.
10) Always check the capacity of your hard disks and perform related maintenances like disk
cleaning, defragmenting, deleting unwanted files or folders to free up disk space, etc.
11) Never expose a diskette, flash disk, CD ROM/DVD, etc to magnetic fields or objects
12) Guard or protect your storage media such as CD/DVD/Flash disks when near X-ray
machines. Their magnetic fields can easily erase all the data from your storage media.
13) Avoid spilling anything such as beverages on storage media
14) Do not subject your storage media to extreme heat or coldness. Room temperature is
better for your storage media.
15) Never touch the shiny or glittering part of your storage media such as Compact Disks
(CDs). Oil and dirt from your hands can easily spoil the surface of the storage media; the
finger prints can also cause problems when the computer tries to read or write tie the
storage media.
16) Clean the storage media only using the recommended cleaning reagents but not any
cleaning product.
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17) Do not use any other person’s computer without prior permission from the owner.
18) Do not attempt to disclose or discover any other person’s password.
19) Do not copy or transfer any computer software without the user’s or owner’s permission.
20) Do not use any college, school or university computers to violate the terms of any
software license agreement or copyright provisions.
21) Do not copy, rename, change, examine or delete files of information belonging to some
other user.
22) Do not intentionally use computer facilities to harass others or to interfere with their
work. E.g. sending obscene, abusive, threatening message to a user or users.
23) Do not tamper with terminals, microcomputers or any other associated equipment and
faults should be reported immediately to the system administrator.
24) Do not attempt to modify system facilities, illegally obtain extra resources or degrade any
system’s performance.
25) Always close tasks running before shutting down the computer.
26) Refer services to fully qualified personnel in case of problems you cannot easily get the
solutions.
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Maintenance of computers (Measures that protect computers)
The following are some of the ways to keep your computer clean for maximum
performance:
Buy dust covers to prevent the build-up of dust on your computer
Place the computer in a cool area
Clean the computer on a regular basis
Properly manage the files on the computer’s hard drive. Remove old files from the computer hard
disk and back them up to an external storage device in case you need them.
Utilize virus protection and detection software to protect the computer against malicious
software
Avoid using a computer during a storm since lightning can affect them.
Use uninterruptible Power Supply (UPS) to protect the computer from crashing during
power surge.
Always backup information to external storage devices to avoid loss of data.
Recover from crashes by pressing Ctrl + Alt + Delete keys at the same time to reboot your
computer.
Never open an email attachment from unknown sources
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Do not download files from internet sites you don’t know and trust.
Never turn a computer off with the power switch except when the hard drive is not running
Never unplug peripherals from the computer when it is powered up as it may short out the
connector socket or the motherboard.
Keep at least 300MB of your C: drive free to avoid the computer from becoming slow and
dumping data to the hard drive.
Do not load too many programs onto the computer’s memory
Use firewalls to avoid unnecessary access to your system by hijackers.
Keep track of the software disks you receive because they contain valuable software drivers
and programs for windows.
Use burglar proofing. This includes filling grills on doors, windows and the roof to prevent
forceful entry into a computer room.
Install fire prevention and control equipment; such as smoke detectors, non-liquid based and
non-powder based fire extinguishers. Liquids may cause corrosion of computer equipment;
Powder particles may increase friction and wear of movable parts as well as causing disks to
crash.
The room should be well laid out. Computers should be placed on stable, wide desks to
avoid accidentally knocking them down. Cables should be laid out in trunks from user paths
to avoid people stumbling on them.
Installing lightening arrestors on the computer room.
How to keep a computer clean
 Never spray your computer’s monitor with water, instead use a lint-free cloth lightly with
glass cleaner and then clean the screen.
 Use specific computer vacuum cleaners to clean keyboards, computer case vents and
around drive openings.
NB: Never try to open your computer to clean the inside parts; take it to an authorized
technician for cleaning.
Measures that protect the user
i. All cables should be insulated to avoid danger of electric shocks to the users.
ii. Cables should be laid away from user paths to avoid stumbling on them.
iii. Providing antiglare screens (light filters) and adjustable screens to avoid eye strains and
exhaustion caused by CRT monitors.
However, modern flat panel displays such as
Liquid Crystal Display (LCD) do not strain the eye.
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iv. Provide standard furniture to avoid poor sitting posture which may lead to strain injury
and limb tiredness. The seat should have an upright backrest and should be high enough
to allow the eyes of the user to be level with the top of the screen.
v. The room should be properly ventilated to avoid dizziness caused by inadequate supply
of oxygen to allow computers to cool.
vi. Overcrowding in the computer room should not be allowed. This causes suffocation.
vii. The walls of the computer room should not be painted with over bright reflective oil
paints and the screens should be faced away from the window to avoid glare caused by
bright backgrounds.
1
Revision questions:
1. What is the name given to alternative sources of power?
A. Generators
B. UPS
C. Power backups
D. The sun
2. Which of the following will not ensure proper ventilation in a room?
A. Adequate windows and doors
B. Overcrowding
C. Installing fans’
D. Air conditioning systems
3. All the following are dangerous to a computer except one. Which one is it?
A. Water
B. Smoke
C. Proper ventilation
D. Dust
4. Why must foods and beverages be kept out of the computer room?
A. Because computer users should not eat
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B. Because spilling beverages may clog and destroy computer components
C. Because the smell of food is not good for the computer lab.
D. Because all foods affect computers
5. Which one of the following statement is correct?
A. Opening the system unit when it is still on
B. Using magnets in the computer room
C. Covering the computers with dust covers after shutting them down
D. Stepping on power and data cables
6. Why are powder fire extinguishers not allowed in the computer room?
A. Powder particles settle on storage devices and may crash them during read/write
operation
B. Powder is poisonous
C. It fills the room with mist
D. Powder changes to liquid when sprayed on fire
7. All the following are functions of the UPS except one. Which one is it?
A. It prevents sudden power surges to destroy the computer
B. It supplies power to the computer during blackouts.
C. It provides stable power supply (clean power)
D. It can be used as the main power source for computers
8. Which of the following reasons are likely to cause eye strain in the computer room?
A. Poor lighting
B. Bright monitor
C. Poor ventilation
D. Anti-radiation screen
9. All of the following are proper sitting postures while using a computer except one. Which
one is it?
A. Straight posture on the seat back
B. Feet firmly on the floor
C. High enough seat allowing eyes to be level with top of the screen
D. Bending the back backwards on a relaxing chair
10. What can be done to deter illegal access to a computer room by unauthorized persons?
A. Burglar proof the room by reinforcing doors and weak access points
B. Welcome strangers to the room
C. Leave the room open when nobody is using it
D. Switch off security alarm when leaving the room
NB: To clean a computer laboratory:
 Shut down all computers
 Wipe the keyboards with antimicrobial wipes
 Clean each mouse
 Clean the tops of the computer desks
 Wipe the buttons on the computers
 Dust the monitors
 Sweep the floors
 Wipe down the chairs
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Physical parts of a computer
A desktop computer is made up of a collection of different components that are interconnected in
order to function as a single unit. A typical desktop is made up of a system unit and other devices
connected to the system unit called peripheral devices. Examples of these peripheral devices
include; monitor/screen, keyboard, mouse, etc.
System Unit
This is the part that houses the brain of the computer called the CPU. It also houses other devices
called drives.
There are two types of systems unit namely; Tower and Desktop type.
Peripheral devices. These are devices connected to the system unit using special cables called
interface cables that transmit data and information to and from the devices. These cables are
attached to the system unit through ports.
Keyboard. This is a peripheral device that enables a user to enter data and instructions into a
computer.
Mouse. This is a pointing device that enables the user to execute commands.
Monitor. It is a device used for displaying information. It is called a monitor because it enables a
user to monitor or see what is going on in the computer.
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CLASSIFICATION OF COMPUTERS
Computers can be broadly classified by their size, process, purpose and processor power.
CLASSIFICATION BY SIZE.
Under this classification, we have Super computers, mainframe, mini and microcomputers.
1. Super Computers
Supercomputers are one of the fastest computers designed to handle sophisticated tasks. They are
very expensive and are employed for specialized applications that require huge amount of
mathematical calculations (number crunching). They are nearly 50,000 times faster than
microcomputers since they process data in Trillions of Instructions Per Second. For example,
they are used in weather forecasting, scientific simulations, animated graphics, fluid
dynamic calculations, nuclear energy research, electronic design, nuclear plants, and
analysis of geological data (e.g. in petrochemical mining).
Input Unit
2. Mainframe Computers
Mainframes are very large in size and are expensive computers capable of supporting a hundred
to a thousand users at once. Mainframe performs many programs at the same time and supports
many immediate execution of programs. They have stronger multi-processors compared to
mini computers, they are relatively big in terms of physical size compared to mini and
microcomputers. They are relatively expensive compared to mini computers. They are used
by banks, aviation companies and universities,
3. Mini Computers
It is a midsize multi-processing system capable of supporting 250 – 500 users at once.
They have relatively stronger multi-processors compared to micro computers, they are
relatively big compared to micro computers; they are used in small and medium sized
organizations.
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4. Micro/personal computers (PC)
These computers are the smallest, relatively inexpensive and designed for an individual user.
They are preferred mostly by homes and schools. Tey are called microcomputers because they
have CPUs called Microprocessors.
Examples include:
 Desktop computers. They are designed to be placed on top of a desk hence the name
desktop derived.
Desktop computer
 Laptop computers. They are small, easily transportable, lightweight micro computers
that can easily fit into a briefcase and good for mobile computing.
 Notebooks. They are smaller laptops convenient for mobile users.
 Thin client systems. These are desktop computer systems that do not offer full
functionality of a PC. Examples are Terminals and network computers.
 Mobile devices. These are handheld devices called Personal Digital Assistants (PDAs)
or handheld personal computers. Examples of PDAs include:
 Handheld companions. They are designed to access and manage data as
additions to notebooks or PCs.
 PC companions. Used for Personal Information Management (PIM), e-mail and
Light Data creation capabilities.
 Smart phones. They are phones with added PDAs, PIM, data, e-mail creation capabilities
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
Vertical Application Devices. Devices used for data access, management,
creation and collection. They are used for vertical markets.
 Pen Tablets. Devices with pen input and tablet form for gathering data in the
field or in mobile situation.
 Handheld Keypads. Devices with alphanumeric keypads used in specialized data
collection applications.
 Tablet PCs. Devices with touch sensitive displays that can be tapped with a pen
while foregoing a mouse or touchpad.
Although personal computers are designed as single-user systems, these systems are normally
linked together to form a network. In terms of power, now-a-days High-end models of the
Macintosh and PC offer the same computing power and graphics capability as low-end
workstations by Sun Microsystems, Hewlett-Packard, and Dell.
Workstation
A workstation is a single computer system which is similar to personal computers but has a more
powerful microprocessor. It is used for engineering applications (CAD/CAM), desktop
publishing, software development, and other such types of applications which require a moderate
amount of computing power and relatively high quality graphics capabilities.
11
Workstations generally come with a large, high-resolution graphics screen, large amount of
RAM, inbuilt network support, and a graphical user interface. Most workstations also have a
mass storage device such as a disk drive, but a special type of workstation, called a diskless
workstation, comes without a disk drive.
Common operating systems for workstations are UNIX and Windows NT. Like PC,
Workstations are also single-user computers like PC but are typically linked together to form a
local-area network, although they can also be used as stand-alone systems.
CLASSIFICATION BY PROCESS
Computers are classified by process according to how the data processed is represented. They include:
i. Digital computers. These are computers that process data represented in discrete values. Discrete
values are numbers that can be defined such as 1, 2, 3, 4, 5… E.g. Digital watches.
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ii.
Analog computers. These are computers that process data represented in a continuous
form or in measurable quantities usually of physical nature. These quantities are length,
voltage, pressure, speed, current, temperature, time, weight, etc. and the results are
estimated in the nearest unit. E.g. thermometer, speedometer, voltmeter, etc.
iii.
Hybrid computers. These computers have combined features of both the digital and
analog computers. They are used for specific applications. E.g. robots used in industrial
control processes.
CLASSIFICATION BY PURPOSE.
The hybrid computers are further classified according to the work they are designed for. They
are grouped into two classes:
i.
Special purpose computers. These computers are designed to handle only a specific
task. Their forms of operation are limited in nature. E.g. digital watches, pocket
calculators, lifts in buildings, computer guided missiles, etc.
ii.
General purpose computers. These are computers designed to perform a wide range of
tasks. They perform all activities as desired by the user such as word processing, games,
spreadsheets, keeping date and time, etc.
CLASSIFICATION BY PROCESSOR POWER.
Due to rapid changes in technology, processor power is also increasing as computers are getting
faster every time. The higher the processor power, the faster the computers become. Earlier
computers had a processor power of less than 0.4 MIPS (Millions of Instructions Per Second)
but today, computers have at least 15 MIPS which is the minimum.
The most common types of processor power are:
 80286
 Pentium III
 80386
 Pentium IV
 80486
 Pentium M
 Pentium I (80586)
 Celeron
 Pentium II (Pentium Pro)
 Duo Core
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Review questions
1. Define the term computer
2. State different physical parts that make up a computer.
3. Differentiate the following types of computers:
a) Supercomputers and mainframe computers
b) Minicomputer and a PC
4. Differentiate between digital and analog computer
5. Which of the following is not true about the system unit?
A. It houses the CPU
B. It houses the monitor
C. It connects to all peripheral devices using ports
D. It has the computer’s power switch
6. What is a mouse in relation to computing?
A. A small destructive rodent
B. A round plastic container with a tail
C. A device that controls a pointer on a screen
D. A device used for typing
7. Why is the screen also called a monitor?
A. It monitors the user
B. It helps the user to track computer operations
C. It monitors system performance
D. It is a television
8.
A.
B.
C.
D.
Pick the odd one out in the list below.
Calculator
Mobile phone
Robot
Laptop
9.
A.
B.
C.
D.
Pick the odd one out in the list below
Mainframe
Microcomputer
Minicomputer
Digital computer
10. Which of the following will be most suitable for travelers?
A. Supercomputer
B. Mainframe computer
C. Palmtop computer
D. Minicomputer
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11. Why is a mobile phone regarded as a computer?
A. It is electronic, has a screen, keypad, memory and is programmable
B. It looks like a palmtop
C. It is portable
D. It produces tones
12. What is meant by the term analog data?
A. Data never stops
B. Discrete data
C. Large data
D. Continuous data
13. Which of the following is called a microprocessor?
A. The CPU of a mainframe
B. The CPU of as microcomputer
C. The CPU of a minicomputer
D. The CPU of a supercomputer
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THE COMPUTER SYSTEM
A computer system refers to all the functional units required for a computer to perform its
tasks.
A computer system is into four (4) basic categories:
 Hardware
Physical components
 Software
Programs
 User/Liveware
Human beings using the computer
 Data/Information
Input/Output
COMPUTER HARDWARE
The term hardware refers to the physical and tangible components of a computer. They are
features that you can see, touch and feel. Computer hardware is categorized as follows:
 Input devices/hardware
 Output devices/hardware
 Processing devices/hardware
 Storage devices/hardware
INPUT DEVICES.
These are devices used to enter data and instructions into the computer. Data is fed into the
computer in order to be processed. Data can be in form of pictures (graphics), sound, or text
(characters). These input devices include:
1.
Keyboard. This is an input device used to enter text and other characters and to control
the operation of the computer.
It is made up of numbers, letters, symbols and special keys to control the sending of data
to the Central Processing Unit. A standard keyboard has about 103 keys. Most keyboards
use the QWERTY layout named for the first six keys on the top rows of the letters.
Most keyboards are divided into five main sections as shown below:
Function Keys
F1 – F12
Alphanumeric Keys
Numeric Keypad
A–Z
0 - 9, +, -, *, /
Arrow keys, Page Up, Page
Down, Home,
Insert, Delete, End
Cursor control & editing keys
Modifier/Special purpose
keys
Shift, Alt, Ctr````````l, Esc.
Allows a user to execute
commands mostly during
program installation or startup, just at the touch of a key.
This is the main typing area
of the keyboard used to enter
text and commands to the
computer.
To input figures
For moving the cursor
To delete & insert characters
Used mostly in combination
to execute a command
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Keyboard special keys:
a) Alt (Alternative) Key
The Alt key is used in combination with other keys to perform specific functions.
In most window programs, the main menu tabs have got underscored letters. E.g. File,
Edit, View, Format, Tools, Table, Window and Help.
Pressing Alt with the underlined letter will activate that menu. E.g. Alt + F4 is used to
exit a program.
b) Control Key (Ctrl)
It is used with other keys to perform specific operations. E.g. Ctrl + F2 – Print
preview, Ctrl + S – Save, Ctrl + U – Underline, Ctrl + P – Print, Ctrl + B – Bolds a
selection, Ctrl + Alt + Del – Restarts a computer (warm boot), Ctrl + Alt + F2 –
initiates the Open file dialog box, Ctrl + X – Cuts a selection, Ctrl + W – Exit, Ctrl
+ Esc – Activates the Start up menu, etc
c) Shift Key.
The Shift key switches between lowercase and uppercase characters during regular
typesetting. When the cursor is in the last bottom cell of a table, pressing tab adds
another row; Shift + Tab takes you back to the previous field.
It is also used for other shortcut operations. E.g. Shift + F3 alternates between
lowercase and uppercase characters, title case and sentence case characters; Shift +
Arrows – used to select text; Shift while inserting the CD-ROM deactivates Auto run.
d) Windows Key. It activates the startup menu for the computer user to run shutdown,
Run, Help, Search, Settings, Documents, Programs, Control panel, etc using arrow
keys. E.g. Ctrl + Esc.
e) Enter/Return key. Used to enter/confirm commands or move from field to field, and
to add a field/row in a table.
f) Del key. Erases characters to the right of the cursor position
g) Tab key. Moves the cursor five spaces to the right by default compared to the space
bar where the number of spaces are usually adjustable.
h) Backspace key. Erases characters to the left of the cursor position.
i) Esc (escape) key. Used to exit or close a dialog box
j) Cursor control keys. They are:
Home key
Moves the cursor to the beginning of a line
End
Moves the cursor to the end of a line
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Insert
Del
Page up
Page down
Num lock
Print screen
Scroll lock
Used for overtyping
Deletes characters to the right of the cursor position
Moves the cursor to the top of a page
Moves the cursor to the bottom of a page
Activates the numeric keypad
For printing what is on the computer’s screen
For scroll lock. Disabled in modern keyboards
Types of keying devices
Traditional keyboard. This is the most common type of keying device with a full
sized rigid keyboard.
Flexible keyboard. It is a more portable keyboard that can be folded and packed into
a bag
Ergonomic keyboard. It is a specially designed keyboard that provides comfort and
alleviate wrist strain.
Keypad. It is a miniature keyboard used on portable devices such as PDAs, laptops
and mobile phones.
Braille keyboard. A keyboard designed for use by the blind. It consists of keys
identified by raised dots.
Pointing devices. These are devices with which one can move or control a cursor
pointer on a Graphical User Interface. These are:
2. Mouse.
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This is a handheld input device used to position the cursor, point, select, move and
confirm operations. It can be used to give commands, draw and perform other types of
input task.
A mouse follows the basic techniques below:
 Pointing. Moving the mouse to move the on-screen pointer.
 Clicking. Pressing and releasing the left mouse button once more rapidly and consistently.
 Double clicking. Pressing and releasing the left mouse button twice more rapidly and
consistently.
 Dragging. Holding down the left mouse button while pointing on an icon as you move the
pointer to a desired location.
 Dropping. Releasing the left button in the process of dragging an icon, a file or a folder.
 Right clicking. Pressing and releasing the right mouse button to display a list of commands
from which a user can make a selection.
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Scrolling. Using the scroll wheel to move a page in a ny direction to allow the user to
navigate it well.
Moving a mouse on a flat surface makes the pointer on the screen to move in the same
direction as the mouse itself.
When using the mouse, follow these guidelines:
i)
Place the mouse on a flat smooth surface
ii)
Gently hold the mouse with your right hand, using the thumb and the two fingers
iii)
The index finger should rest on the left button while the middle finger rests on the right
button
Types of mice include:
(i) Desktop mouse
Desktop mouse include:
a. Mechanical/standard/traditional mouse. This is a type of mouse that has a rubber or metal
ball on its underside and it can roll in every direction. Sensors within the mouse, which are
mechanical, detect the direction in which the ball is moving and moves the pointer on the screen
in the same direction. A mouse pad is used to run the mouse on.
b. Opt-mechanical. This is a type of computer mouse that uses optical sensors to the motion of the
ball.
c. Optical. This type of mouse uses laser for detecting the mouse’s movement. Optical mice do
not have any mechanical moving parts. They respond more quickly and precisely than the
mechanical and opt-mechanical mice.
(ii) Trackball mouse.
This type of mouse is common on most laptop computers with a rolling ball and buttons fixed
within the keyboard.
(iii) Touch pad mouse. This type is common on modern laptop computers. It has a rectangular pad
with two push buttons. Once a finger is moved on a pad, the mouse pointer change positions
accordingly.
Advantages
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 It does not need as much desk space as a mouse
 Can readily be built into the keyboard
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 Has finer resolution, i.e. to achieve the same cursor movement onscreen takes less movement of
the finger on the glide pad than it does mouse movement.
 Can use either buttons or taps of the pad for clicking.
Disadvantages
 The hand tires faster than with a mouse since there is no support
 Some people don’t find the motion as natural as a mouse
Parts of a mouse
 Primary button
 Secondary button
 Wheel button
 Rubber ball (for track ball and opt-mechanical types of mouse)
 Housing – This can be held into a hand
 Cables connecting the mouse to the system unit
 Interface connector to attach the mouse piece to the mouse board
A mouse’s advantages include:
 Easy to use
 Not very expensive
 Moves the cursor faster than the arrow keys of keyboard.
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Types of mouse interface (Connection)
Serial interface. A serial port transmits one bit at a time. Used by old PCs with 9 – 25 pin male
connectors, most PCs have got two serial ports. I.e. COM 1 and COM 2. Once the device driver
is initialized, it searches for the connected port.
PS/2 Mouse interface. It is an on board mouse port interface or motherboard mouse interface
Bus – card interface. This works through Input/Output (I/0) card onto the system motherboard.
Cordless interface. A cordless mouse uses infrared technology to do away with the cord.
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Mice faults
Mouse pieces are usually disturbed by the following:
Accumulation of dirt on the mouse rollers and the whole mechanism as well.
Bending of the pins
Interruption conflicts. The mouse piece fails to be recognized.
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Advantages of using a mouse
A mouse is user friendly for computer beginners
A mouse is easy to and convenient to use with a Graphical User Interface
Using a mouse to select items or move to a particular location on the screen is faster than using a
keyboard.
33
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
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Disadvantages of using a mouse
It is not easy and convenient to input text with a mouse
Giving commands using a mouse is slower than using a keyboard
It needs some practice in order to control a mouse properly
A mouse is not accurate enough for drawings that require high precision
A mouse usually requires a flat surface to operate
A mouse needs more desk space to operate compared to a trackball or touchpad.
3. Track Ball
Track ball is an input device that is mostly used in notebook or laptop computer, instead
of a mouse. This is a ball which is half inserted and by moving fingers on ball, pointer can
be moved. Since the whole device is not moved, a track ball requires less space than a
mouse. A track ball comes in various shapes like a ball, a button and a square.
4. Stylus. A pointed instrument used as input device on a pressure-sensitive screen
5. Cyber glove. Is an input device for virtual reality environment. Various sensor technologies
are used to capture physical data such as bending of fingers.
Usually, a motion tracker such as a magnetic tracking device or inertia tracking device is
attached to capture the global position or rotation data of the glove.
These movements are then interpreted by the software that accompanies the glove, so any
one movement can mean any number of things. Gesture can be categorized into useful
information such as to recognize sign language or other symbolic functions.
NB: Virtual reality is an environment that can be interacted with in a seemingly real or
physical way by using special electronic equipment.
6. Eye tracking/eye gaze. Eye tracking follows the eye movements of a person looking at any graphic
such as printed advertisement. It is used to analyze the usability and effectiveness of the layout.
7. Scanner. This is an input device that reads images or texts and converts the data and transmits them
into the computer in form of digital signals.
Graphical scanners read photos or other images into the computer and digitize them.
Types of scanners
a) Magnetic Ink Character Recognition (MICR)
MICR input device is used to capture data written using magnetic ink or coded onto a
magnetic strip. It is generally used in banks because of a large number of cheques to be
processed every day.
The bank's code number and cheque number are printed on the cheques with a special
type of ink that contains particles of magnetic material that are machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main
advantage of MICR is that it is fast and less error prone.
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b)
Optical Character Recognition (OCR)
OCR is an input device used to read a printed text. OCR scans text optically character by
character, converts them into a machine readable code and stores the text on the system
memory. A more advanced OCR scanner called flat-bed scanner is used to capture
pictures and real objects.
c) Bar Code Readers
Bar Code Reader is a device used for reading bar coded data or Universal Product Code
(UPC) (data in form of light and dark lines). Bar coded data is generally used in labeling
goods, numbering the books etc. It may be a hand held scanner or may be embedded in a
stationary scanner. Bar Code Reader scans a bar code image, converts it into an
alphanumeric value which is then fed to the computer to which bar code reader is
connected.
d) Optical Mark Recognition (OMR)
OMR is a special type of optical scanner used to recognize the type of mark made by pen
or pencil and a piece of paper. It is used where one out of a few alternatives is to be
selected and marked. It is specially used for checking the answer sheets of examinations
having multiple choice questions.
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8. Digitizer. This device also known as a graphic tablet allows a user to draw images using a stylus. It
is used together with a digitizing tablet in making maps (cartography) and architectural drawings to
accurately trace out lines on a map.
9. Digital camera. This device can be used like a traditional camera except that its images are stored
digitally in memory housed within the camera and later imported or downloaded onto the computer
for further editing and printing.
10. Touch sensitive screens. These are screens that can sense when a particular part of their screen is
touched and they respond accordingly. They are mostly used in retail stores, airports, on smart
phones and PDAs.
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11. Web cam. It is a small digital cam mounted onto a PC monitor to allow two way communication
involving sound and video communication not only text communication.
12. Joystick and game pads. It is an input device used in modern computer games. E.g. flight
simulator. A joystick looks like a car gear lever; it works like a track ball mouse that can rotate in
360 degrees.
13. Light pen. It is a pen like input device which allows a person to point to areas on the
screen and it is often used to select menu choices. It consists of a photocell and an optical
system placed in a small tube. When the tip of a light pen is moved over the monitor
screen and pen button is pressed, its photocell sensing element detects the screen location
and sends the corresponding signal to the CPU. E.g. used in ware houses to input large
amount of data quickly by moving a light beam across a bar code.
14. Smart boards. This is a large interactive display that connects to a computer. The display
is projected onto the board’s surface where users control the computer and write using a
pen or finger. The board is typically mounted to a wall or on a floor stand.
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15. Voice recognition equipment. This device is used to enter data into as computer inform of sound
input. Recent systems allow you to talk to a PC and see text appear on the screen.
Revision Questions
1. a) What is the difference between function keys and Special PC keys/control keys?
b) Explain the various categories of keys found on a standard keyboard
2. i) Define the following terms:
a) Double clicking
b) Clicking
c) Drag and drop
d) Right clicking
e) Pointing
ii) What makes a mouse pointer move on the screen?
3. Classify the following keyboard characters:
a) A, B, C, D,…….Z
b) 0, 1, 2, ……..9
e) Home, End, Page UP, Arrow key
c) F1, F2,…….F12
d) Del, Insert
f) Ctrl, Shift, Alt
4. a) What is a computer system?
b) Differentiate between a computer and a computer system
5. a) A scanner used at points of sale terminals in supermarkets is an example of
a…………..scanner
b) The automated input technique where keying of input data is eliminated is sometimes referred
to as……
c) The type of scanner used to grade multiple choice examination is called……………..
d) Describe two situations in which speech recognition devices may be useful as a method of
data entry.
OUTPUT DEVICES
These are devices used to bring out information from the computer and present it in a suitable
form to the user. This unit is a link between computer and users. Output devices translate the
computer's output into the form understandable by users.
These devices can be classified into two categories namely: Hard copy and soft copy output
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Soft copy refers to the intangible output that can be seen or heard; such as screen display and
sound
Hard copy refers to the tangible output that can be felt such as paper. Examples include
printers, plotters and facsimile (fax)
The type of output depends on whether a computer is to produce a hard copy or a softcopy output.
E.g. output can be text, pictures or graphics, sound and computer usable output on the screen.
Examples of output devices include:
1.
Speakers. These are output devices that produce information in form of sound.
2.
Plotters. These are output devices that produce hardcopy output on paper and are used to print line
drawings. They have a series of moving parts that can accurately draw straight, thin and
meandering lines. Plotters are often used to produce architectural drawings, map making, charts
and other technical drawings.
3.
Monitor/screen/Visual Display Unit (VDU). This is a TV like device which produces
information in a visual output or soft copy. It forms images from tiny dots, called pixels
that are arranged in a rectangular form. The sharpness of the image depends upon the
number of pixels.
There are two kinds of viewing screen used for monitors.
 Cathode-Ray Tube (CRT) Monitor
The CRT display is made up of small picture elements called pixels. The smaller the
pixels, the better the image clarity, or resolution. It takes more than one illuminated pixel
to form a whole character, such as the letter in the word help.
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A finite number of characters can be displayed on a screen at once. The screen can be
divided into a series of character boxes - fixed location on the screen where a standard
character can be placed. Most screens are capable of displaying 80 characters of data
horizontally and 25 lines vertically.
Advantages
 Can produce fast color output
 Can be viewed from a very wide angle
 Cheaper in cost than LCD monitors
There are some disadvantages of CRT:
 Large in Size
 High power consumption
 Emit higher electromagnetic radiation (EMR) than LCDs
 Flat-Panel Display Monitor
The flat-panel display refers to a class of video devices that have reduced volume, weight
and power requirement in comparison to the CRT. You can hang them on walls or wear
them on your wrists. Current uses of flat-panel displays include calculators, video games,
monitors, laptop computer, graphics display.
The flat-panel display is divided into two categories:
 Emissive Displays - The emissive displays are devices that convert electrical energy
into light. Examples are plasma panel and LED (Light-Emitting Diodes).

Non-Emissive Displays - The Non-emissive displays use optical effects to convert
sunlight or light from some other source into graphics patterns. Example:
LCD (Liquid-Crystal Display) that is made up of special liquid crystals to create
images on the screen.






Advantages of LCDs
They are less bulky,
Consume less power
Have little strain effect on eyes
Have a higher resolution than CRTs
Have a higher refresh rate compared to CRTs
They have a narrow viewing angle compared to CRTs


Disadvantages
They are usually more expensive compared to CRTs
They can only be viewed from a very narrow angle
Gas plasma displays that uses gas instead of liquid crystals. They contain millions of
pixels that are illuminated by charged neon gas.
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Monitor display terminologies
Pixel. Stands for picture elements. Are tiny dots which are used to form the images
displayed on the screen.
Color depth. Refers to the number of colors which can be displayed by a pixel called
color depth. It is measured in bits.
Resolution. This is the number of pixels per inch on the screen usually given in dots
per inch (dpi) or bits. The higher the resolution, the more the number of pixels per
square inch, hence clearer images.
Refresh rate. Since CRTs cannot hold an image for a long time, image in the video
RAM is used to refresh the one on the screen as long as necessary. If a screen has a
low refresh rate, images tend to flicker hence causing eye strain.
Display size. Is measured in inches as the digital length of the screen measured from
the top right to bottom left.
i.
ii.
There are basically two categories of monitors. They include:
Monochrome monitors. These monitors display only one color especially white on a dark
background. They are not expensive and are used principally for word processing and other
applications where color is not applicable.
Color monitors. These are often called Graphics Monitors which display text and graphics in
color. Examples of these monitors are:
 CGA – Color Graphics Adapter. Displays 16 colors
 EGA – Enhanced Graphics Adapter. An improvement of CGA but also displays 16 bits
 VGA – Video Graphics Array. Displays text, graphics and video using 256 colors
 SVGA - Super Video Graphics Array. Displays text, graphics and video using more than
16 million colors, has a minimum resolution of 800 x 600 pixels.
 XGA - Extended Graphics Array. Has a resolution of up to 1024 x 768 pixels. It is
popular with 17 and 19 inch monitors
 SXGA – Super Extended Graphics Array. Has a resolution of upto 1280 x 1024 pixels
and is popular with 19 and 21 inch monitors.
 UXGA – Ultra Extended Graphics Array. It is the largest and highest standard type of
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NB: Portable monitors. These are monitors used on laptops, notebooks, digital diaries, mobile
phones, calculators, etc. they are flat panel monitors that consume little power and can also
display color. However, they can also be either monochrome or color monitors.
Advantages of display devices
 The time to display the image is fast
 Screen displays can include text, graphics and colors
 Display devices are usually quiet
 No paper is wasted for obtaining output
Disadvantages
 Information produced on the screen is only temporary and lost when power is turned off.
 Unsuitable for users with visual problems
 Needs a separate device to produce the hard copy
Factors to consider while monitoring the performance of a monitor
Luminance. This is measured in candelas per square meter. (cd/m2) also called a nit.++66
4. Data projectors. Are used to display output from a computer onto a plain white screen like wall
or whiteboard. It is a creative way of presenting computer output to an audience.
5. Printers. A printer is an output device which produces hard copies of computer processed data.
Printers are classified according to whether the output produced is by physical contact of the
print mechanism with the paper or not.
Categories of printers
Impact printers. These are printers that produce their hardcopy output by the print mechanism.
i.e. print heads physically touching the print media. The print media can be paper,
transparencies, cloth, some plastic, etc.
Examples of impact printers include:
i.
 Character printers. These are low speed printers that imitate the action of typewriters by
printing one character at a time.
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 Line printers. These printers print a whole line of characters at once. I.e. they print from one
end of paper to the other end, hence called line printers. E.g. Daisy wheel printers;, thimble
printers, etc.
Daisy wheel printers have letters on the ends of spokes to form a wheel. The letters
strike an inked ribbon onto paper.
Advantage
 It has good typewriter resolution
Disadvantages
 Very slow – ½ ppm
 Very noisy
 Can only print the characters provided on the wheel and no graphics (line drawings,
pictures, etc)
 It prints only in one color.
 Dot matrix printers. These printers form characters by the print heads forming a pattern of dots
on paper to make out a character. E.g. Epson LQ 1170 (24 pin), Epson FX880 (9 pin), etc




Advantages of using a dot matrix printer
It is quite fast – 2 ppm
Slightly noisy
Can print any shape of character (font) stored in the computer memory and any graphics, all on
the same page.
Some are capable of printing low quality colors on the same page using multiple ribbons
 Page printers. These are printers that use the method of printing page by page. They are much
faster than the above three printers.
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Advantages of impact printers
1. The cost of per page printing is lower and the printed characters last longer
2. Impact printers are cheaper to purchase
3. They do not require special paper to print on
4. They are easy to maintain as its print heads require fewer periodic cleaning
5. Dot matrix printers are very fast that they go over a speed of 160 characters per
minute thereby increasing their productivity.
6. They can print on multi-part forms (Carbon or Carbonless)
Disadvantages of impact printers
1. They are very noisy during operation
2. They have a lower print resolution compared to other types of printers
3. They print slowly compared to non-impact printers.
4. The ink ribbon has a short lifespan and has to be replaced frequently.
5. The resulting image is of low print quality and, if used to print barcodes, it might be
difficult to read them.
6. Their print heads get heated up during long printouts thereby reducing the entire
productivity.
ii.
Non impact printers.
These are printers that produce a hardcopy output without the print heads physically
touching the printing surface.
Examples include:
 Inkjet printers/DeskJet printers. These printers spray small droplets of ink to
create characters. They use either the drop-on-demand technique or the
intermittent jet technique. In the drop-on-demand technique, liquid ink is pushed
out of the nozzles in drops while in the intermittent jet technique, ink is fired out
of the nozzles in a continuous stream.
The ink pumps work by heating a coil around a particular ink channel, which
expands and constricts the ink in the channel causing a droplet if ink to pass
through the nozzle. Each pump channel works at a rate of approximately 5 KHz
(5,000 droplets per second). Examples include HP DeskJet 690C and Epson
Stylus 640.
Advantages
It is very quiet
Full black and color print on the same page
It has a very high resolution of between 300 – 600 dpi
Thousands of colors are created by mixing tiny dots of cyan, magenta and yellow
(CMY) ink on the paper
Disadvantage
It is very expensive in the long run to replace the cartridge after being used up
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
LaserJet printers. Laser printers are high quality printers with a greater Near
Letter Quality (NLQ) capability and a high speed output. Excellent graphics are
obtained with this type of printers.
In the print mechanism, a laser light source is used to transfer the image stored in
the printer’s memory onto a special drum. The drum attracts the toner (ink used
to print the characters) and the paper is pressed against the drum; the image is
then transferred to the paper and heated before the paper comes out of the printer.
Examples are HP LaserJet 1100 series printer, HP LaserJet 5M (Color printer)
HP LaserJet M1132 MFP, etc.
Advantages of laser printers
Very fast – 6-16 ppm for multiple choices
Almost silent
It prints many copies before the cartridge is used up
Disadvantage
Color laser printers are quite expensive but are cheaper to run than color inkjet
printers.

Bubble Jet printers. These printers are also called thermal Ink Jet printers. They
also work by the print head nozzles spraying tiny droplets of ink onto the print
surface. But here, the ink pumps heats ink in the ink channel until a bubble is
formed; this bubble grows larger and larger until it bursts forcing a droplet of ink
through the print head nozzle onto the print media. Since the droplets are heated
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

up, it dries faster on paper than the DeskJet printers. Canon BJC 200 is an
example of a Bubble Jet printer.
Photo printers. They are special purpose printers designed for printing photos
Thermal printers. These printers have the print heads containing dot heaters
(heating elements). During the printing process, the print head circuitry transfers
electrical energy to each desired dot heater which heats up rapidly. The heated up
dot heater then causes specific points on the special paper to discolor
accordingly. The thermal printing paper normally discolors to a black or blue
color in accordance to its make
.
1.
2.
3.
4.
Advantages of Thermal printers
They are nearly noiseless since they do not have any moving parts to generate
noise.
They also consume very little power as compared to other printers
Their print mechanisms are reliable because they do not experience
inconveniences like paper jams or blocked nozzles.
They produce clear and crisp images with very high resolutions.
Disadvantages of Thermal printers
1. They cannot print on any other paper because the heat generated will not cause
any discoloration without burning the entire paper.
2. The papers used for printing are also limited to a particular shelf life. I.e. the
longer they stay unused or used, the more they will be affected by age, sunlight,
humidity and chemical vapors which may cause it to discolor completely thereby
causing characters to disappear.
3. They are not ideal for commercial printing. The papers need to be specially
prepared before they can be used in printing and they can only be stored for a few
years before they go bad.
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4. They are expensive to maintain. The print heads cannot be serviced or repaired
even if a single dot heater fails. The whole print head has to be replaced.
5. The print speed is also very slow because the heads have to be allowed to cool
befor the next printing cycle.
6. Thermal print heads have a shorter life span than other print heads. They are
expected to print a maximum of 10 million characters accurately whereas other
printers like the dot matrix can print over 500 million characters in their life span.

Braille printer. This printer produces patterns of raised dots on paper for use by
the blind; this is done by converting text into Braille code.

Multifunction printer. This type of printer can perform more than one task.
They can operate as fax machine, copier and scanner in addition to their
traditional printing duties.
Methods of printing
 Characters Per Second (CPS). This is a method where the printer speed is rated
by the printed characters per second. They use dots to create characters and
graphics and are low speed printers.
 Lines Per Minute (LPM). This is where printers use the method of printing line
by line and the printing speed is measured in printed lines per minute.
 Pages Per Minute (PPM). This is where printers use the method of printing
page by page and the printing speed is measured by printed pages per minute.
Common terms in printing
Print spooler. This is a program that stores information selected to the printer.
Printer buffer. This is a section of the memory in the printer that stores
information that has been selected for printing. A spooler can store more
information that the buffer and lets you continue using your computer without
having to wait for a document to hurry printing.
Less common types of printers include:
Line printer, Daisywheel printer, Ball printer, Thermal printer, Plotter, Large
format printer, portable printer, photo printer, label printer, Braille printer.
Advantages of Non Impact Printers
1. They are much faster in printing
2. They have lower ink cost over time
3. It is easy to maintain them
4. Non impact printers are better for multi-use
5. It is easier to find their spare parts in case they need replacement
6. There is less time spent in refilling paper
7. They generate less noise compared to impact printers
8. They are much more reliable
9. They have a high quality print resolution
10. The printer cartridges and drums are recyclable, resulting in environmental benefits.
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Disadvantages if non - impact printers
1. More money is required to replace the toner/ink
2. They are expensive in terms of purchase
3. Their maintenance is more complicated
4. They are harder to use with old computer technologies.
5. A laser printer occupies a lot of space and emits dust particles that can cause
respiratory diseases.
6. They cannot be used to produce multiple copies of a document in a single
printing.
Factors to consider when purchasing a printer
i)
Initial cost. Though the prices of printers have come down, laser and thermal
printers are still expensive compared to inkjet printers
ii)
Print quality. Dot matrix are good for bulk printing of draft documents; laser
is good for printing official documents while thermal printer is good for
check-out counter receipts
iii)
Running cost. The cost of maintaining an inkjet printer is higher than that of
maintaining a LaserJet printer.
iv)
Speed. The speed of a printer is measured in Pages per minute
v)
Color printing. Most printers support black and color printing. However,
color printers, especially lasers are relatively more expensive
vi)
Printer buffer and spooler. To help holding back the information sent from
the computer and releasing it at a rate the printer can handle.
Review Questions
1.
2.
3.
4.
Differentiate between soft copy and hard copy
What is the difference between a CRT monitor and a flat-panel display?
Name four criteria used when selecting a printer
Distinguish between impact and non-impact printers and give two examples of
each.
5. State one advantage and one disadvantage of laser and inkjet printers.
6. Nile Construction Company Limited intends to buy an output device they can
used to produce road maps, which device would you advise the company to buy
and why?
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THE SYSTEMS UNIT
This is the metallic casing that houses the most important components. The major
integral components in a computer systems unit include:
PROCESSING DEVICES
The major integral components in a computer processing system are:
Central Processing Unit (CPU)
This is the main centre of activity in the computer which performs all the processing
of data.
Microprocessor. This is an integrated circuit containing all the functions of a central
processing unit of a computer.
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The CPU controls all the activities taking place within a computer.
The CPU consists of three sub units:
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a. Control Unit. This is the unit which controls and supervises the operations of a
computer.








Functions of the control unit.
It directs data from storage to memory
It sends data required for mathematical operations from the memory to the
Arithmetic Logic Unit (ALU).
It sends processed data to the printer or a storage device
It erases/deletes/rubs data from the memory when instructed to do so
It controls and times all tasks by the CPU (this is typical of multi-tasking where
processor time is shared amongst competing tasks)
It manages and coordinates all the units of the computer.
It obtains the instructions from the memory, interprets them, and directs the
operation of the computer.
It moves a program statement to the instruction register.
To coordinate all these activities, the control unit uses a system clock. The
system clock sends electric signals as its means of communication in the CPU.
The faster the clock pulses, the faster the CPU, hence the faster the computer
can process data.
b. Arithmetic Logic Unit (ALU).
This unit consists of two subsections, namely:
 Arithmetic section
 Logic Section
Arithmetic section
This section performs arithmetic operations like addition, subtraction,
multiplication and division. All complex operations are done by making
repetitive use of above operations.
Logic Section
The basic function of the logic section is to perform logic operations such as
 It also identifies whether a number entered is positive or negative.
 It also compares two or more numbers to determine which one is than, equal to
or lower than the other. This is performed due to the logic capability.
 It also merges data (combining two or more files a single file)
c. Memory/Registers
This refers to the area of the computer that stores data and programs during
operation.
Examples of registers include:
Accumulator. It temporarily holds the results of the last processing step of the
ALU.
Instruction register. It temporarily holds an instruction just before it is
interpreted into a form that the CPU can understand.
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Address register. This temporarily holds the next piece of data waiting to be
processed.
Storage register. This temporarily holds a piece of data that is on its way to
and from the CPU and the main memory

The systems motherboard.
The motherboard is contained within the systems unit and all the vital components
are plugged directly into the motherboard. The CPU is normally housed on the
system board along with all other components. Other items such as the hard disk are
attached to the system board either directly or via cables (buses)

Data buses. A bus is an electrical pathway through which data passes. It is a circuitry that
is responsible for transferring data to and from the processor. They consist of a set of
parallel wires.
Types of buses
Control bus. This is the pathway for all timing and controlling functions sent by the
control unit to other parts of the system
Data bus. This is an electrical pathway where the actual data transfer takes place. It
connects the CPU, memory and other hardware devices on the motherboard
Address bus. This is the pathway used to locate the storage position in the memory
where the next instruction data to be processed it held. It carries the memory
addresses


BIOS chip.
BIOS stands for Basic Input Output System. They are software instructions that
ensure that all the components on the motherboard work together. They are
contained in a BIOS chip attached to the motherboard. When a computer is
switched on, an electronic charge activates the BIOS instructions to execute the
Power On Self Test (POST) routine.
Device Interfacing Bays
These are the points of contact on a computer which are used for connecting
additional system components or peripherals to a computer
Revision Questions
1.
2.
3.
4.
Define the term Central Processing Unit
Describe three functions performed by the CPU
What is a microprocessor?
Explain the functions performed by:
a) Control Unit
b) Arithmetic and Logical Unit
c) Memory
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5. Name three special purpose memories found either inside or outside the
microprocessor and explain what each does.
6. Explain the purpose of the system clock
7. What is the meaning of BIOS, and what role does it play in a computer?
8. List three buses found in the CPU
UCE 2009 Paper 1
23. a) State any two functions of the Central Processing Unit (CPU)
b) Define the following memory storage terms:
i) Bit
ii) Byte
c) State two categories of computer memory giving an example in each case
d) Describe the major difference between the two categories of computer
memory in c)
24. a) What is a microprocessor?
STORAGE DEVICES/DISK DRIVES
A disk drive is a device which allows data to be read from or written to a disk, either
a hard disk or compact disk.
Storage devices are devices that store information for future use. They are called
secondary storage devices.
Secondary storage devices are classified according to:
 Portability as removable and fixed
 Technology used to store and retrieve data as magnetic, optical, magneto-optical and solid
state.
A. Removable Storage media. They are devices that are not housed inside the
computer. They include:
i.
Floppy diskette. This is a secondary storage device/medium onto which data is
stored randomly by means of magnetized spots on an inexpensive disk.









Care for floppy diskettes and other magnetic storage media
Do not bend the disk
Do not touch the exposed data parts with fingers
Do not apply paraffin
Do not expose the diskettes to magnetic fields like radios, mobile phones, etc
Always label diskettes for easy identification
Do not write on or label using sharp pens or objects
Store the disk in its jacket
Hold diskettes by their corners
Keep diskettes away from dust
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

Do not remove a media from the drive when it ias still being accessed by the
computer because it may result into data loss.
Do not drop magnetic media on the ground because the impact weakens magnetism.
Advantages of floppy disks
 they are cheaper compared to other storage media
 they are protected in plastic casing
 they facilitate data transfer
 They are in standard sizes. E.g. 3 ½, 5 ½, 5 ¼ and 8 ¼. This make them very usable by
different computer manufacturers.
 They can easily be edited and formatted
 They are flexible and easy to transfer
Disadvantages
 They provide less storage capacity compared to hard disks
 They operate at a slow speed
 If not handled properly, they can lead to data loss
 Data can easily be lost once the magnetic media is exposed to magnetic fields
 They can affect machines with viruses
ii. Zip disk. These are storage devices that were made to store medium amount of data.
Their capacity is bigger than that of floppy disks.
iii. Jaz disks. They resemble zip disks but they can hold as much as 2 GB. Data is read or
written using internal or external jaz drives
iv. High capacity floppy. High capacity disks simply known as HiFD disks are high
capacity diskettes that can store up to 200 MB of data. HiFD drive can also read the
magnetic 1.44 MB diskette.
v. Laser Servo 120 SuperDisks. (LS 120), is a diskette that resemble a 3.5 inch diskette
but uses optical technology. It has a greater storage capacity and speed of data retrieval
(It can store upto 240MB). The LS – 120 can read and write both the 3.5 inch floppy
disk and the 120 MB super disk.
vi. Magnetic tape. This is a plastic tape coated with a thin film of magnetic material. They
are mainly used with mini and mainframe computers. The main disadvantage is that they
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only allow “serial access”. I.e. to access data at the end of the tape, it is necessary to roll
past the rest of the tape first.
NB: The above storage devices are known as magnetic storage media. Data is written
using magnetic drives
vii. Compact Disc This is an optical storage medium that contains data accessible by a computer. It
is called compact disk because it is small with a diameter of 12cm and a thickness of a few
millimeters. Information on a CD is permanently stored.
Currently compact disks are available in three forms:
Compact Disk Read Only Memory (CD – ROM). This contains data that can only be read but not
written on
Compact Disc Recordable (CD – R). They are coated with special dye which changes color to
represent data when burned using a laser beam. Once data is burned on a CD-R, it becomes read
only.
NB: CD – ROM and CD – R are referred to as Write Once Read Many (WORM). Data is written
only once but can be read as many times.
Compact Disk Rewritable (CD-RW). These types allow a user to record, erase, and rewrite new
information onto it.
Advantages
 They hold a great deal of information in a very small area (Up to 700MBs of data).
 They are easy to store.
 They are portable because of their small size.
 Their data access speed is also very fast.
 They are convenient in distributing huge software programs because the data life of
information in nearly 100%.
Disadvantages
 They can attack computer systems with viruses
 Just a single scratch on a CD can make the whole CD useless
viii. Digital Versatile Disc Read Only Memory (DVD – ROM)
This is an advanced optical storage media format that can be used for data storage
including movies with high video and sound quality. DVD resembles CD – ROMs but
CD – ROM readers cannot read DVDs due to the fact that they are encoded in a different
format of a greater density. A DVD can store 4GB of data and more which is available in
recordable format which enable computer users to write and store data on it. For writing
data on a DVD, a special writer must be installed in your computer.
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ix. Flash disks. These are devices that contain the type of memory which can be erased and
are integrated with USB connectors. They are connected to the USB port; data can be
written to and erased from memory using the current of electricity.
NB: A flash disk is a solid state storage media. This is a type of media that employs
integ9rated circuits rather than mechanical, magnetic or optical technology.
x. Optical card. An optical card resembles a MICR card but data is read and written
optically on a stripe. They are mostly used in banking and other business organizations to
record customer details.
xi. Optical tape. This is similar to a magnetic tape only that data is stored on it by using
optical technology.
The above devices are known as optical storage media. This is so because data is
written to and read from them using a laser beam.
Optical storage media is used because:
 They store very large volumes of data
 Data stored in them is more stable and more permanent than the magnetic media.
B.
Fixed storage media. They are devices mounted inside the computer.
xii.
Hard Disk Drive (HDD)/fixed disk. This is a metallic magnetic media housed in a
rigid box inside the computer system.





Advantages
They provide a greater storage capacity
They are speedy that the time of data access is very fast and convenient
The data life of a hard disk is quite long once in use
Data is always secure since they reside inside the system and have fewer chances of
being stolen or misplaced.
They facilitate data backup as they supplement RAM
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




Disadvantages
They are relatively expensive
They are prone to viruses
They can crash leading to information losses
Since they are metallic, they can expand and contract depending on temperature
changes, thus, causing data loss
Information can be easily lost once they are malfunctioned
Most computer hard disks are connected to the motherboard via a channel called a
controller. Some of these controllers are Integrated Drive Electronic (IDE), Enhanced
IDE, or AT attachment (ATA)
The following table shows the various disk drive types and their corresponding letters.
However, in some cases, the drive letters may change
Disk drive
Drive letters
3.5 or 3 ½ inch floppy diskette
A:
5.25 inch
B:
Hard disk/fixed disk
C:
CD-ROM
D:
Zip Drive
E:
Network (system drives)
F: - Z:
Revision Questions
1.
2.
3.
4.
5.
6.
Differentiate between primary and secondary storage devices
Distinguish between removable and fixed storage
What are the advantages of a hard disk over a floppy diskette?
Why re CD-ROMs and CD-Rs referred to as WORM?
Describe the difference between magnetic and optical storage media
Jet Publishers is a company that specializes in production of newspapers. One of
the editors wanted to transfer a 50MB document from the hard disk of one
computer to another using a removable storage media. Give four examples of
the devices he/she could use.
7. Describe three precautions you would take to avoid damaging the hard disk.
UCE 2009
6. Which of the following can be written to only once?
A. Diskette
B. Hard disk
C. Flash disk
D. CD-ROM
UCE 2007
21. (c) i. Distinguish between primary and secondary storages
ii) Give an example of each type of storage in c)i above
iii) Identify one disadvantage of a hard disk over a floppy disk.
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UCE 2006
2. Which of these components is the brain of a computer system?
A. Main memory B. Secondary chip
C. Processor chip
D. Power supply
Other hardware devices

Power supply unit. This is a device which controls the supply of power in a computer
circuit as they need power in varying amounts. It is responsible for:
 Distributing power to different parts of a computer
 Converting Alternating Current (AC) to Direct Current (DC)

Expansion slots. These are empty spaces found on the system board (motherboard)
where control circuits or other separate devices can be attached later. E.g. modem,
network adapter, sound card, etc.

Device drivers or control circuits. These are devices that work as interface between the
computer and other devices attached to it. E.g. monitor, keyboard, mouse, etc.

Uninterruptible Power Supply (UPS). This is a device that controls the amount of
current entering the computer. It therefore;
 Acts as a backup power in case of power failure
 It converts AC (Alternating Current) to DC ( Direct Current) needed for the
computer

Computer memory. This refers to the storage area or space in the computer where
programs and data reside during computer operation.




Functions of memory unit are:
It stores all the data and the instructions required for processing.
It stores intermediate results of processing.
It stores final results of processing before these results are released to an output
device.
All inputs and outputs are transmitted through main memory.
There are two basic types of computer memory:
57
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 Random Access Memory (RAM) or Primary memory. This is the temporary type of
memory found on the computer. It is also known as Main memory or primary storage.
It is responsible for storing data, program and program result. It is a read/write
memory which stores data until the machine is working. As soon as the machine is
switched off, data is erased.
Characteristics of RAM
 Access time in RAM is independent of the address that is, each storage location inside
the memory is as easy to reach as other locations and takes the same amount of time.
 It is the temporary memory where the computer holds data for the current processing
task.
 The user can read from it and write to it.
 Data in the RAM can be accessed randomly but it is very expensive.
 RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if
there is a power failure. Hence a backup uninterruptible power system (UPS) is often
used with computers.
 RAM is small, both in terms of its physical size and in the amount of data it can hold.
There are two types of RAM
 Static RAM (SRAM)
The word static indicates that the memory retains its contents as long as power is being
supplied. However, data is lost when the power gets down due to volatile nature. SRAM
chips use a matrix of 6-transistors and no capacitors. Transistors do not require power to
prevent leakage, so SRAM need not have to be refreshed on a regular basis.
Because of the extra space in the matrix, SRAM uses more chips than DRAM for the
same amount of storage space, thus making the manufacturing costs higher. So SRAM is
used as cache memory and has very fast access.
Characteristic of the Static RAM
 It has long life
 There is no need to refresh
 It is faster
 It is used as cache memory
 It has a large size
 It is expensive
 It has high power consumption
 Dynamic RAM (DRAM)
DRAM, unlike SRAM, must be continually refreshed in order to maintain the data. This
is done by placing the memory on a refresh circuit that rewrites the data several hundred
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times per second. DRAM is used for most system memory because it is cheap and small.
All DRAMs are made up of memory cells which are composed of one capacitor and one
transistor.
Characteristics of the Dynamic RAM
 It has short data lifetime
 There is need for DRAM to be refreshed continuously
 It is slower as compared to SRAM
 It is used as RAM
 It is lesser in size
 It is less expensive
 It has less power consumption
 Read Only Memory (ROM). This is the permanent type of memory found in the
computer. The inbuilt permanent instructions which are put in at the time of
manufacture are called Firmware and are stored on ROM chips.





Characteristics of ROM
The user can only read the contents but cannot write on it.
This type of memory is non-volatile.
The information is stored permanently in such memories during manufacture.
It stores instructions that are required to start a computer. This operation is referred to
as bootstrap.
Types of ROM
MROM (Masked ROM)
These were hard-wired devices that contained a pre-programmed set of data or
instructions.

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. Inside the
PROM chip there are small fuses which are burnt open during programming. It can be
programmed only once and is not erasable.

EPROM(Erasable and Programmable Read Only Memory)
The EPROM is a read – only memory that can be erased by exposing it to ultra-violet
light for a duration of up to 40 minutes. During programming, an electrical charge is
trapped in an insulated gate region. The charge is retained for more than ten years
because it has no leakage path. For erasing this charge, ultra-violet light is passed
through a quartz crystal window (lid). This exposure to ultra-violet light dissipates the
charge. During normal use the quartz lid is sealed with a sticker.

EEPROM(Electrically Erasable and Programmable Read Only Memory)
The EEPROM is a ROM that 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 (millisecond). In EEPROM, any location can be selectively erased
and programmed. EEPROMs can be erased one byte at a time, rather than erasing the
entire chip. Hence, the process of re-programming is flexible but slow.
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






Advantages of ROM
They are non-volatile in nature. I.e. they do not lose their contents even when power
goes off.
These cannot be accidentally changed
They are cheaper than RAMs
They are easy to test
They are more reliable than RAMs
They are static and do not require refreshing
Its contents are always known and can be verified
Other memory options (Special purpose memories):

Virtual memory. This is the storage space in the hard disk used to extend or
expand the RAM. It enables the computer user to open more programs than the
available RAM capacity can actually handle.
Video Memory (VRAM). It is used to store display images for the monitor. Its
size determines how fast images can appear on the screen, and the number of
colors available for either monochrome or colored monitors.
Flash memory. This is a non-volatile RAM chip inserted into the USB port to
stimulate and supplement the hard disk. It is light and portable.
Buffers. These are special memories that are found in input/output devices.
Cache Memory. Cache memory is a very high speed semiconductor memory
which can speed up the CPU. It acts as a buffer between the CPU and main
memory. It is used to hold those parts of data and program which are most
frequently used by CPU. The parts of data and programs are transferred from
disk to cache memory by operating system, from where CPU can access them.




Advantages
 Cache memory is faster than main memory.
 It consumes less access time as compared to main memory.
 It stores the program that can be executed within a short period of time.
 It stores data for temporary use.
Disadvantages
 Cache memory has limited capacity.
 It is very expensive.
Differences between Primary memory and Secondary memory
Primary Memory
Secondary memory

These are semiconductor memories

It is known as main memory.

Usually volatile memory.

These are magnetic and optical
memories

It is known as backup memory.
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
Data is lost in case power is switched
off.

It is non-volatile memory.

Data is permanently stored even if
power is switched off.

It is working memory of the computer.

Computer may not run without primary
memory

It is used for storage of data in a
computer.

Faster than secondary memory

Computer may run without secondary
memory.

Slower than primary memory.
Measurement of Memory units
A memory unit is the amount of data that can be stored in the storage unit. It is a unit in
which storage capacity is expressed in terms of Bytes.
Below are the main memory storage units:
Bit (Binary Digit). A binary digit is logical 0 and 1 representing a passive or an active
state of a component in an electric circuit.
Nibble. A group of 4 bits is called nibble.
Byte. A group of 8 bits is called byte. A byte is the smallest unit which can represent a
data item or a character.
Word. A computer word, like a byte, is a group of fixed number of bits processed as a
unit which varies from computer to computer but is fixed for each computer.
The length of a computer word is called word-size or word length and it may be as small
as 8 bits or may be as long as 96 bits. A computer stores the information in the form of
computer words.
The table below summarizes the actual and equivalent measurement units of computer
memory:
1 Bit
1 Byte
1 Kilobyte (KB)
1 Megabyte (MB)
1 Gigabyte (GB)
1TeraByte (TB
=
=
=
=
=
=
1 binary digit (0 or 1)
20
/ 8 bits
10
2 bytes / 1024 Bytes
220 bytes / 1024 KB
230 bytes / 1024 MB
240 bytes / 1024 GB
OR
1 Byte
Approximately
=
8 bits
Actual Size
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1Kilobyte
1 Megabyte
1 Gigabyte
1 Terabyte
=
=
=
=
1,000 Bytes
1,000,000 Bytes
1,000,000,000 Bytes
1,000,000,000,000 Bytes
1,024 bytes
1,048,576 bytes
1,073,741,824 bytes
1,099,511,627,776 bytes
The following are among the standard binary codes that have been developed with each
standard having unique set:
ASCII code.
The ASCII code is a code that was suggested by the American Standard Code for
Information Interchange (ASCII) and it consists of 256 characters.
EBCDIC code.
The Extended Binary Coded Decimal Interchange (EBCDIC) code was mainly used
during the larger computers generation. I.e. Third generation machines. It is also referred
to as the 8-bit ASCII code because it has fewer characters than the ASCII.
BCD code
The Binary Coded Decimal (BCD) code is the least used code that uses the 6-bit
representation of characters. This 6-bit code is now outdated and almost extinct.
The table below summarizes the comparison across the three major codes for each of the
selected characters.
Character
Value
A
B
C
D
65
66
67
68
ASCII
code
0100 0001
0100 0010
0100 0011
0110 0100
EBCDIC
code
1100 0001
1100 0010
1100 0011
1100 0100
BCD
code
110 001
110 010
110 011
110 100
Review Questions
1. Define the terms: volatile memory and non-volatile memory
2. Define and explain the differences between RAM and ROM
3. How many characters (bytes) of data are held in each of the following
memories?
4KB, 640KB, 16MB, 20GB
UCE 2009
17. The text you type is directly stored in………..
A. RAM
B. A file
C. A directory
D. ROM
27. A computer system comprises hardware, software, user, data and
communication. Describe the importance of each component.
UCE 2008
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7. The device that stores programs and data when working with a computer and
is lost when power is switched off is……
A. CPU
B. ROM
C. GUI
D. RAM
28. a) Explain what is meant by volatile and non-volatile when referring to
primary memory
b) Explain the advantages and disadvantages of using primary and secondary
storage devices
UCE 2007
3. A device that interprets and executes instructions in the computer and also
called the brain of the computer is the
A. System Unit
B. Base Unit
C. CPU
D. ALU
CONNECTION TREMINALS (SLOTS, SOCKETS, PORTS) OF A
COMPUTER
Connection terminals are found both inside and outside the computer system. The
ones found inside the system are called Sockets or Slots while the ones found
outside the system are called ports. Slots, sockets and ports are always identified by
the data bus width or architecture that is designed for them. A data bus width is the
size of the paths that transfer data to and from the processor. These standards
include ISA, EISA, PCI, etc depending on the data transmission that they support.
Therefore, slots are classified as ISA, EISA, PCI slots or AGP slots as for those for
the video card.
Slots are long linear structures on the motherboard that have a series of connection
pins which act as contacts to a card that may be plugged into them.
Sockets are commonly processor sockets on the motherboard which are identified
depending on the processor architecture they support. E.g. Socket 7 for Pentium I
processors, socket 5 for 80486 processors.
Peripheral device interfacing
This refers to connecting a peripheral device to a computer through ports using
either cables or wireless connectivity.
A port is a physical connection point through which an external device can be
connected to the computer.
It can also be a programmatic connection point through which information flows
from a program to computer or over the internet.
A port has the following characteristics:
 External devices are connected to a computer using cables and ports.
 Ports are slots on the motherboard into which a cable of external device is plugged
in
Examples of external devices attached via ports are mouse, keyboard, monitor,
microphone, speakers etc.
Following are few important types of ports:
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Serial (COM) Port
 It is used for external modems and older computer mouse and printers
 It is a male port with two versions: 9 pin, 25 pin models
 Data travels at 115 kilobits (kbps) per second – 1 bit at a time
Small Computer System Interface (SCSI) Port
 It is a female 48 – pin port
 It transfers data at a higher rate than parallel ports
 They are for storage devices on the network





Parallel (LPT – Line Printer) Port
It is used for scanners and printers
It transmits data in parallel bits
It is also called printer port
It is a female 25 pin model
It is also known as IEEE 1284-compliant Centronics port that is commonly known
as the local port (LPT).




Personal System (PS/2) Port
It is used for old computer keyboards and mice
It is also called mouse port
Most of the old computers provide two PS/2 port, each for mouse and keyboard
It is also known as IEEE 1284-compliant Centronics port
Universal Serial Bus (or USB) Port
 It can connect all kinds of external USB devices such as external hard disk, printer,
scanner, mouse, keyboard etc.
 It was introduced in 1997.
 Most of the computers provide two USB ports as minimum.
 Data travels at 12 megabits per seconds
 USB compliant devices can get power from a USB port
VGA Port
 Connects monitor to a computer's video card.
 It has 15 holes.
 Similar to serial port connector but serial port connector has pins, it has holes.





Power Port
It is connected directly on a power unit that is responsible for administering power
There are two power ports: power input from the mains for the computer and power output
to the monitor
The input power port has three-pronged pins that plug into a female main power
cable
The output power port has three-pin plug in port.
These ports always input power rating of either 110 – 220V 0r 220 – 240V
depending on the power line rating in a particular area.
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 Connects to the computer's power cable that plugs into a power bar or wall socket





Firewire Port
It transfers large amount of data at very fast speed.
It connects camcorders and video equipments to the computer
Data travels at 400 to 800 megabits per seconds
It was invented by Apple
It has three variants : 4-Pin FireWire 400 connector, 6-Pin FireWire 400 connector
and 9-Pin FireWire 800 connector
Modem Port
 It connects a PC's modem to the telephone network. This connection offers the
capability of connecting (dialing in) to remote computers over the internet.




Ethernet Port/Network Port
It connects to a network and high speed Internet.
It connects network cable to a computer.
This port resides on an Ethernet Card.
Data travels at 10 megabits to 1000 megabits per seconds depending upon the
network bandwidth.
Game Port
 Connect a joystick to a PC
 Now replaced by USB.
Advanced Technology (AT) Port
 It is a female circular port with 5 holes arranged mainly in its lower circle
 It was developed in 1948 and widely used as the keyboard connector for IBM
compatibles and clone computers.
Apple Desktop Bus (ADB) port
 It is a female port consisting of 4 holes in pairs with a guiding square at the top
 It was used by earlier Apple computers as keyboard interface
i.link port
 It transfers very large volumes of data in a short time
 It can achieve up to 400Mbps of data transfer
 It is suitable for interface devices like digital cameras, camcorders and other
imaging devices
 A single link can connect up to 63 external devices
Digital Video Interface (DVI) port
 It connects Flat panel LCD monitors to the computer's high end video graphic cards.
 It is very popular among video card manufacturers.
Audio Port
 It is used to connect microphones and speakers to the sound card of the computer
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Infrared interface
Infrared, also referred to as Infrared Data Association (IrDA) is a wireless interface
that uses infrared to connect to infrared – enabled devices.
Bluetooth interface
Bluetooth is also a wireless interface that uses short range radio broadcast to
connect to any Bluetooth – enabled device.
Review Questions
1. Define the following terms:
a) Port
b) Interface cable
c) Power cable
2. What is the function of the power supply unit found in the system unit?
3. Differentiate between parallel serial interface cables
4. Give two advantages of a USB interface cable
5. What would happen if you bend the pins of a monitor port as you try to connect
the monitor interface cable to the system unit?





Computer hardware problems
Excessively low or high temperature causes circuit or bus cracks, connection
breaks and dislocation
Corrosion as a result of coming into contact with atmospheric chemicals, food,
human body and water, hence, causing rust.
Effects of dust that builds thick coatings in slots, ports, internal chips, etc ,
therefore causing unnecessary heat, data and electric insulation
Effect of electrical noise in form of electrostatic discharge causing short circuits,
electromagnetic interferences and electromagnetic reductions travelling in space
Electrical power variations causing blackouts, excessive low voltage, etc
COMPUTER SOFTWARE
 Software is a set of instructions, given to a computer to accomplish various tasks.
 It can also be defined as the programs that a computer system utilizes to perform various
tasks.
 Software also refers to the intangible components of a computer.
A program is a sequence of instructions written to solve a particular problem.
When a computer processes data, it follows a particular sequence of instructions. This
sequence of instructions is stored in memory with specific details of
 What is to be done
 The alternative paths that can be taken once decision are to be made
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

a)
b)
c)
d)
e)
f)
Locations where inputs can be collected from
Locations where outputs are to be written to
Such a sequence is called a Program and the preparation of such instructions is called
programming.
Forms of software
Packaged software. This is a commercial software which is copyright protected and is
designed to meet the needs of a wide variety of users
Custom software. This is a specially made software developed at a user’s request for a
specific function.
Freeware. This is a copyright software provided at no cost to the users but without
permission to modify it.
Shareware. This is a copyright software distributed for a trial period of time and payment
is required for continued use after the trial period.
Public Domain Software. It is a free software that is donated for public use and it has no
copyright restriction.
Firmware. These are programs built in the computer at factory level with special
instructions for basic computer operation
Types of computer software
Computer software is divided into two main types or categories. Namely:
1. SYSTEMS SOFTWARE.
This refers to a set of computer programs that control the way a computer operates.
These programs are written by computer manufacturers or professional system
programmers. Some of these programs reside in the ROM and are known as Firmware.
Systems software is comprised of the following:
a) Operating systems. This is a set of programs that contain instructions that manage and
coordinate all activities among computer hardware.
It manages resources such as Processors, Storage, Input & Output devices, Data and Programs.







Functions of the Operating system
It schedules and loads programs so as to provide a continuous sequence of processing
It manages the processor by carrying out all controlling processes
It enables the booting of a computer by accessing starter files called bootstrap loader
It controls hardware devices. E.g. control over the selection and operation of devices for input,
storage or output.
It protects the hardware, software and data from improper use. E.g. preventing illegal access to
system files
It calls into memory programs and instructions when required
It passes control from one program to another when more than one application program occupies
memory
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





It helps in provision of error correction routines. E.g. when data is lost during transfer, it should be
recovered
It provides a record of whatever is happening during processing. E.g. keeping record of hardware
use.
It communicates with the user. E.g. reporting suspended programs due to errors, request for
operation like “insert disk”, etc.
It manages the storage of various processes and data into the memory
It provides an interface for applications by acting as a translator for all application software in their
utilization of resources.
It sends interrupt requests to the CPU to be handled
An interrupt is a break from the normal sequential processing of instructions in a program
NB: Input/output control programs are the programs that control the input from various devices
and output to those devices as well.
Classifications of operating system
Previous Operating Systems were classified according to the platform they operated on. E.g. PDA
Operating System.
The operating systems below have been classified according to the number of users and tasks
they perform:
 Real Time Operating Systems (RTOS). These are types of operating systems designed to control
the system resources of a given computer in exactly the same manner that each time, a given set of
condition occurs. Computers that use RTOS have no interaction with humans and can only be used
for control purposes. E.g. industrial robotic for control of machines. It runs one application
program in the main memory at a time.
 Single User Single Task Operating Systems (SUST OS). These are operating systems designed
for use in those computing devices that are commonly used by one user at a time. Such computers
using SUST OS carry out limited tasks and operation but they use other bigger computers to
accomplish their bigger roles. E.g. PDA Operating Systems.
 Single User Multitask Operating Systems (SUMT OS). These are operating systems where a
single user can have access to all system resources when performing various tasks. A user can type
a document, download emails, and play audio files at the same time. E.g. Microsoft windows 98,
200, XP
 Multi User Multitask Operating Systems (MUM OS). These are operating systems capable of
running several processes and are designed to support many users at the same time. Here, each user
has a portion of the system resources sufficient for their operational requirements. E.g. VMS on the
mainframe computers, VME on the ICL mini computers.
 Single User Network Operating System (SUN OS). This is an operating system that is capable of
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supporting very many interconnected users on a network. E.g. Novell Netware, Microsoft
Windows 2000 server, Windows NT, etc.
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Examples of operating system software include:
Disk Operating System (DOS). This operating system uses Command Line Interface (CLI)
and it is the main system control program that enables the computer to operate. The user controls
by typing commands like DEL, RUN, and CHKDSK at a prompt. With DOS, you can load only a
single program into memory at a time. For instance, you can copy a file called Fruits.Dat from a
hard disk C to a floppy disk A as follows:
COPY C:\Fruits.DatA:\
NB: the user must press the enter key for each command to be executed.
Examples of those operating systems are PC-DOS, OS/2, UNIX and MS-DOS.
Command Line Interface





Functions of DOS are:
Controlling the flow of information between the user and the computer
It allows a user to store information in the computer
It allows a user to retrieve information stored in the computer
It interrupts and translates the software in the computer
It gives access to all its functions. I.e. saving, copying and printing files, etc



Advantages of Command Line Interface
It is very flexible and can alter the parameters to do different things
Commands are very fast with experienced users
The user can achieve a lot with just one command




Disadvantages of Command Line Interface
It is quite difficult to learners
It is less suitable for beginners or irregular users
It is prone to typographic mistakes
At times, use of obscure abbreviations or key words and syntax is very important
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Windows Operating System. This operating system uses window and icon based Graphical
User Interface (GUI). E.g. Microsoft Windows 95, Microsoft Windows 2000, Microsoft
Windows XP, Windows Vista, Windows 7, etc.
Graphical User - Interface
Networking Operating System. These are operating systems designed to be used on computers
that exist on a network. E.g. Windows NT, Novell Netware, Solaris, etc
UNIX. This is a multi-user and multitasking operating system. It can run multiple applications
and multiple tasks)
Linux. This is an “open source software”. Its code is made available to the public. E.g. Ubuntu,
SuZie, Red Hat Linux, etc
PDA Operating System. This is an operating system designed to be used by Personal Digital
Assistants. E.g. Pocket PC 2002, Palm OS, etc.
Factors to consider when choosing an operating system
a) The hardware configuration of the computer such as the memory capacity, processor speed
and hard disk capacity.
b) The type of computer in terms of size and make.
c) The application software intended for the computer
d) User-friendliness of the operating system
e) The documentation available
f) The cost of the operating system
g) Reliability and security provided by the operating system
h) The number of processors and hardware it can support
i) The number of users it can support.
b) Utility Programs. These are system programs that perform tasks usually related to managing a
computer and its devices or programs.
Utility programs are classified into two:
 System utility. This is a program that increases operation of the system software. For example;
device drivers.
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NB: A device driver is software designed to interpret instructions from the OS to the devices and
from the devices to the OS.
 Application utility. This is a program which boosts the performance of the application software.
Examples of utility programs.
(i) Debuggers. These are used during the testing of a program. They are able to trace the flow of a
program and display various values as requested. Therefore, errors are traced and removed
from the program
(ii) Sorting utility. This is used to rearrange data in any order as specified by the user. E.g. in
ascending or descending order.
(iii) Merging utility. This is a utility program used to combine two or more files to produce only
one file
(iv) Copying / Backup utility. This is used to duplicate/move contents of as file from one location
to a backing storage device.
(v) Antivirus utility. This is used to detect, remove and prevent viruses from the computer’s
memory or storage device.
(vi) File compression utility. It is used to reduce or compress the size of a file. E.g. PK ZIP and
WinZip
(vii) Diagnostic utility. It compiles technical information about a computer’s hardware and
certain system software programs and then prepares a report outlining any identified
problems.
(viii) Disk scanner. It detects and corrects both physical and logical problems on a disk
(ix) Disk defragmenter. It reorganizes the files and unused space on a hard disk
(x)
Uninstaller. it removes an application and its associated entries in from the system files
(xi) Screen saver. It causes the screen to display a moving image or a blank screen if no
keyboard or mouse activity occurs for a specified period. This protects the screen.
(xii) Data recovery utility. It is used to undelete a file or information that has been accidentally
deleted. E.g. recycle bin for windows, Norton un-erase wizard, etc
(xiii) Data processing utility. It removes redundant elements, gaps and unnecessary data from the
computer storage. E.g. Drive space to stacker, Double disk, super star pro, etc.
(xiv) File viewer. It displays the contents of a file.
(xv) Memory management utility. It determines how to efficiently control and allocate memory
resources (usually activated by software drivers.
(xvi) Disk repair utility. It checks your disk drive for defects and makes repairs on the spot. E.g.
Norton disk doctor.
Review Questions
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1.What is a system software?
2.Outline the importance of an operating system
3.Give four examples of operating systems and their respective uses
4.Why do computers need network software?
5.Define the term utility as used in computer software
6.Outline and explain the uses of at least six utility programs.
UCE 2009
9. Real time processing is a task of……..
A. Utility program
system
B. Tailor made application
C. Programming language
D. Operating
25. a) Explain the following terms:
i) Off-the-shelf software, example
ii) Custom software, example
c) i) What is a utility program?
ii) State any four functions of utility programs
7.Which of the following is necessary for running application software?
A. Operating system B. Network Interface Card
Interface
C. Utility program
D. Graphical User
26. a) i. Explain what is meant by the term Operating System
ii) Give any two features of a graphical interface.
UCE 2007
8.Computer programs used in tasks such as removal of viruses or data compression can be
categorized as
A. Word processors B. Desktop publishing
C. Utility programs D. Communication
programs
UCE 2006
8. An antivirus is an example of
A. A user interface
C. An application software
B. An operating system
D. A utility program
22. a) Explain the following terms as used in computer studies
i) System software ii) Application software
iii) Utility programs
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b) Outline four functions of an operating system software
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c) List any five operating systems that you know
UCE 2005
24. c) Define the following terms:
j) Software
ii) Hardware
iii) Application program
k)
d) Programming Languages. This refers to a set of instructions that tells the computer
what to do during the programming process.
It can also be defined as a set of symbols and usage rules employed to direct the
operation of a computer.
A program is a set of instructions that a computer must follow in order to process
data into information.
There are many programming languages. However, they can be placed in two basic
categories; namely, Low Level Languages and High Level Languages.
(i) Low Level Languages. They are called low level languages because they are used for
designing programs or instructions for the processors. They include:
 Machine Code Language. This is also referred to as first generation languages. It
consists of binary numbers. Information is stored in computer circuits as “On” and
“Off”; the “On” and “Off” can be represented in the binary system by the two values
1 and 0 also called Binary Digits (BITS). The example below shows the ASCII
(American Standard Code for Information Interchange), and EBCDIC (Extended
Binary Coded Decimal Interchange) coding systems:
Value
1
2
3
4
5
6
7
8
9
10
Binary code (EBCDIC)
1111 0001
1111 0010
1111 0011
1111 0100
1111 0101
1111 0110
1111 0111
1111 1000
1111 1001
1111 1010
ASCII
0011 0001
0011 0010
0011 0011
0011 0100
0011 0101
0011 0110
0011 0111
0011 1000
0011 1001
0011 1010
A
B
C
D
E
F
1100 0001
1100 0010
1100 0011
1100 0100
1100 0101
1100 0110
0100 0001
0100 0010
0100 0011
0100 0100
0100 0101
0100 0110
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G
H
I
J
1100 0111
1100 1000
1100 1001
1100 1010
0100 0111
0100 1000
0100 0101
0100 0110
Advantages of Machine Code Language
 It can be used directly by the computer without interpretation
 They are machine or computer reliant
 It is highly efficient and allows control of each operation.
 It allows the programmer to pay more attention to the problem
Disadvantages of Machine Code Language
 It is less user friendly. i.e. not very easy to learn, write and correct
 It is time consuming during programming
 It is more technical compared to others
 Each type of processor had its own set of codes, so that machine code programs
written for one processor could not be used on another
 Assembly Language. They are also referred to as Second Generation Languages. It
used English tags such as “ADD” or “SUB” for the codes to add and subtract values.
These tags were called mnemonics.
However, for the processor to understand these codes, they have to be translated first
to machine code by use of an assembler.
Advantages of Assembly Language
 Programs could be written more easily than with machine code language
 It had a closer control over the computer hardware and executes very efficiently
 It is useful for writing operating systems and game programs which require fast
and efficient use of the CPU
 It is more user friendly compared to machine code
 It is less technical compared to machine code
 It is less time consuming as compared to machine code
Disadvantages of Assembly Language
 They are designed for specific machines and specific processors
 Programming using assembly language is laborious
(ii) High Level Languages. These are third generation languages whose instructions
resemble human language or mathematical notations, hence, making it easy to
learn and understand.
 In a high level language, fewer instructions are written and therefore a lot is done in less
time
 It is less technical compared to first and second generation languages
 It is more user friendly
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Types of High Level Languages
Scientific languages. These are languages with the ability to handle mathematical
expressions and procedures. They have inbuilt mathematical functions and can handle
arrays. E.g. FORTRAN and Algorithmic Oriented Language (ALGOL)
Special purpose languages. They are languages designed to be tailor made for a
particular type of functions like wages, inventory management, machine control, etc.
e.g. Business or Commercial languages.
Command languages. These are programs used to control the operation of the
computer. E.g shell used with UNIX.
Multipurpose languages. These are languages intended to cope with a variety of
different types of application areas. E.g. business, science, health, etc. examples
include; BASIC, PASCAL, C, C++, PL/1 by IBM.
Translation of a high level program is done by Compilers and Interpreters.
Examples of high level languages are:
a. COBOL (Common Business Oriented Language). It was produced to enable
efficient software to be produced for business applications. Examples are: payrolls,
accounting and stock control.




Advantages
It is fairly easy to understand
It enables programmers to easily arrange records within a file
It enables programmers to produce reports
It can be used on different types of computers
Disadvantages
 Coding is lengthy and tiresome to make.
 It takes longer to learn
b. BASIC (Beginners All Purpose Symbolic Instruction Code). It was developed as a
means of introducing non-science students to the fundamentals of programming.
Advantages of BASIC
 It is the easiest of all the programs
 It is so popular
 Several books exist that are used as self teaching manuals
Disadvantages
 It is not a standard language
 There are many different versions of BASIC with so little compatibility between them
c. FORTRAN (Formula Translator). It was developed by IBM to write scientific,
mathematical and engineering applications because of its simplicity, conciseness,
consistency, effectiveness and numerical accuracy.
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Advantages of FORTRAN
It is widely accepted and understood
It is easy to write a simple FORTRAN program
Disadvantages of FORTRAN
Using it for other applications other than scientific and engineering applications is quite
difficult
Input and output operations cannot be accomplished easily
Creating easy to read reports or screen display is difficult
d. PASCAL. It was named after Blaise Pascal. The language was developed to teach the
concepts of structured programming.
Advantages of PASCAL
It reinforces the principles of structured programming
It cannot be used in business since is limited to scientific applications
e. C. this is the most portable general purpose language. It isa choice for many operating systems
and application packages. Other derivatives of C include C+ and C++
Other high level languages include:
 APL (A Programming Language)
 PL/1 (Programming Language 1)
 PROLOG (Programming in Logic)
 ALGOL (Algorithmic Language)
 LISP (List Processing)
 JAVA
 PHP (Hypertext Preprocessor)
 PERL (Practical Extraction and Report Language)
(iii) Application Generators (Fourth Generation languages). These are Very Very
High Level Languages (VVHLL) designed to allow a user to program by only
telling the computer what to do and the computer does the programming by itself. The
user defines certain tasks and then the application generators will create the program
code that will perform the tasks that have been defined. E.g. SQL (Structured Query
Language), NOMAD, Focus, Intellect for IBM, C++, etc.
(iv) Artificial Intelligence languages (Fifth Generation Languages).
These are programming tools that allow questions or commands to be in a more
conversational way. They are normally used in Intelligent Knowledge Based Systems
(IKBS) such as robots.
(v) HTML (Hyper Text Markup Language). This is one of the programming languages
used to create web pages for the internet.
(vi) Language Translators. These are programming tools which change high level
languages to machine code language.
They include:
 Compilers. A compiler is a language translator that converts the entire program of
a high level language into machine language before the computer executes the
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program - (Executes later). Examples of High Level languages using compiler are
Pascal, C, COBOL and FORTRAN.

Assembler. An assembler is a language translator that translates an assembly
language into machine code. It allows a programmer to use abbreviations or easily
remembers words instead of using numbers or binary codes. An assembler assigns
specific memory spaces with each symbol name such that even if the program
changes or is transferred to another processor, it will still function well.

Interpreter. An interpreter is a language translator that converts each high level
language statement into machine language and executes immediately, line by line.
Due to their way of operation, interpreters make the entire computing process very
slow and less productive.

Linker. A linker is a system software program that combines compiled programs
and determine where they will be located in memory.
2. APPLICATION SOFTWARE.
Definitions:
 This is a set of instructions that are designed to enable a computer to perform a
specific task.
 These are programs that are designed to solve users’ specific problems.
Application software is sometimes referred to as “application packages” or “packaged
software”.
They make the computer perform different activities of users like word processing,
spreadsheets, accounting, etc.
Application software is designed to run with one particular operating system.
However, cross-platform applications can run on multiple operating systems.
Application software is divided into two categories, namely:
1) Tailor made / custom / in-house developed software (Special Purpose)
2) Off-the-shelf / packaged software.(General Purpose)
1) Tailor made / custom / in-house developed software.
These are applications software developed at a user’s request and to perform a
specific purpose.
Advantages of tailor made software
 They are easy to manipulate.
 They increase productivity.
 They cater the needs of a firm by providing all the necessary details.
 They improve image
Disadvantages of tailor made software
 They are very expensive to design and develop
 They are very rigid since they can only be used by one customer
 They are time consuming to develop
 They need a lot of specialized skills which require expensive special training.
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2) Off-the-shelf / packaged software / commercially developed software.
These are applications software developed and sold out to users to solve different
problems of the users.
The above types of software can also be classified as:
 Special purpose application software. Software designed to be used by
specific industries or markets. E.g. medical practice management tools,
educational tools, legal software, etc.
 General purpose application software. Software designed to be used by a wide
range of organizations and home users for various purposes.
Examples include Microsoft Office Applications (Office suites) ranging from
Microsoft Office 97, Microsoft Office 2000, Microsoft Office 2003, Microsoft
Office 2007, Microsoft Office 2010, Microsoft Office 2013, etc. which includes
Word Processing using Microsoft Word, Spreadsheet using Microsoft Excel,
Database Management System using Microsoft Access, Presentation using Microsoft
PowerPoint, etc. besides Microsoft Office Applications, there are also Open Office
Applications with a combination of Linux and Unix Operating Systems. E.g. Internet
and e-mail applications, multimedia, graphics applications, communication software,
speech recognition software, workgroup software, middleware, enterprise software,
component software, schematic software, etc.






Advantages of off-the-shelf software
They are readily available in software shops.
They are cheap to obtain.
They are flexible since they can be used by and organization.
They are entertainment and leisure tools.
They do not need specialized skills.
They have educational value.
Disadvantages of off-the-shelf software
 They are very easy to manipulate since they are almost known by everyone
 They are not very secure
 They may not handle some problems with ease
(i)
Word Processing.
These programs are used to create, edit, format, save and print documents that contain
text, and graphics such as letters, newsletters, brochures, reports, advertisements, books,
etc. Examples include: Microsoft word, Lotus WordPro, Word Perfect, etc.
1)
Advantages of using Word Processing Software over the use of an ordinary
typewriter.
Easy and fast to make changes.
2)
Has many features to create documents that look professional and visually appealing.
3)
Documents can be reviewed before printing them.
4)
Documents can be saved for future use and editing.
5)
It is convenient to create formal letters and mailing labels.
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6)
It is possible to move blocks of text to different positions in the same document.
7)
Lines of text can be inserted and deleted.
8)
It is possible to alter the layout of the document before printing.
9)
Mistakes can be corrected.
10) Typed documents can be stored in the computer
11) Other text can be merged into a document without having to type it again.
12) The document can be printed many times.
(ii)
Spreadsheet.
They are general purpose programs used to perform calculations. Spreadsheets comprise
a grid of numbered rows (1, 2, 3 …) and lettered columns (A, B, C ...). The location
where a row intersects with a column is called a cell. The cell may contain text or
numeric values. Each cell in within a spreadsheet is given an address. For example, A4 is
Column A and Row 4. Examples include: Microsoft Excel, Lotus 123, Quattro Pro,
Pegasus, Ms Works and VisiCalc, SuperCalc, etc.
Facilities offered by spreadsheets include:
 Storing formulae enabling them to be recalled, amended and re-used.
 Copy formulae from one cell to other cells.
 Formatting numbers to the required number of decimal places, etc.
 Creating graphs from given data.
 Storing information
 Making use of special functions such as average, standard deviations, square roots, etc.
1)
Advantages of spreadsheet software over manual worksheet.
Easy to make changes and correction of data on the worksheet.
2)
When a formula is used, the result from the calculation will automatically be adjusted
whenever related data is changed.
3)
Operation is fast with the help of built-in functions
4)
Calculation is always accurate, provided that the data and formula entered is correct
5)
It is easy to create different kind of charts or change the chart types using a spreadsheet.
6)
Information on charts is updated automatically whenever related data on the worksheet
changes.
7)
Electronic spreadsheets are much larger than manual spreadsheets. This allows the user
to keep related information together and to produce large reports.
8)
Cells in electronic spreadsheets can use information from other cells such as formula or
values.
9)
Electronic spreadsheets can be stored and retrieved for repeated use, editing, updating
and printing.
Spreadsheets can be used in a number of applications such as in analyzing statistics,
creating business plans, creating business budgets, calculating profits and losses, sales
forecasting, etc.
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3. Data management software.
These are used to create, access and manage large amount of information related to a
particular subject. E.g. product details, telephone directory, phone book, etc.
There are two types of data management software:Simple Filling programs patterned after the traditional manual data filling techniques
Database Management Systems (DBMS). Is a collection of files serving as the data resource
for computer based information systems.
Examples of database software include: Microsoft Access, Lotus Approach, Dbase I, II,
III, IV, Paradox, Oracle, File Maker Pro, etc.
4. Presentation Software.
These are used to create computer-based slide show. They are mostly used to communicate
ideas and information to an audience. E.g. during meetings or seminars to enhance a
speaker’s or presenter’s ideas graphically. Examples of presentation software include:
Microsoft PowerPoint Lotus Freelance, Harvard Graphics, Macromedia Director, etc.
Functions of presentation software
 It helps users to organize and present information to an audience.
 It provides tools that help to outline your thoughts and build a presentation quickly using
professionally designed templates
 It is used to enhance your presentation with pictures, charts, sound and video
5. Desktop Publishing software.
These are used to combine text and graphics to create a professional publication. Examples
include: Adobe PageMaker, Aldus PageMaker, Microsoft Publisher, etc.
6. Graphics software.
These are programs used to create, edit and print graphics ranging from charts, paints,
drawings and images. Examples include: Adobe Photoshop, Adobe Illustrator, Paint
shop, etc.
7. Communication software.
These are programs that help to create a connection among computers on a network.
These connections can be through cables, telephone lines or satellite systems. They include
software browsers like Eudora, Netscape, Microsoft Navigator, etc.
8. Speech recognition software.
These are programs that translate voice patterns into text.
There are two types of speech recognition software:
Discrete speech recognition. This can interpret only one word at a time, so users must place
distinct pause between words.
Continuous speech recognition. This can interpret a continuing stream of words.
9. Workgroup software. These are programs that help groups and teams to work together by
sharing information and by controlling workflow within the group. Products are designed to
support tasks such as
 Project management
 Scheduling
 Workflow
 Retrieval of data from shared database, etc.
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10. Middleware. This is a software designed to link application modules developed in different
computer languages and running on various platforms.
Enterprise software. These are programs that manage the vital operations of an
organization such as
 Supply chain management
 Inventory renewal
 Ordering
 Human Resource Management
 Operation accounting and financial management
11. Component ware. These are application software in which programs manage one type of
operation.
12. Schematic software. These are programs that can create schematics, space plans, layouts,
etc.
Software suites. These are collections of application software packages bundled together.
Characteristics of application software
i.
They are menu driven. I.e. the user takes a choice out of a number of options.
ii.
They are user friendly. Many of them have Graphical User Interface which makes it easy to
learn and use.
iii.
They are targeted to a wide range of users
iv.
They are designed for power and flexibility so that their capabilities are addressed
irrespective of the hardware
v.
The packages are designed to work on a range of computer systems and data can be
transferred from one computer to another.
vi.
vii.
viii.
ix.
x.
xi.
xii.
xiii.
Close to user
Easy to design
More interactive
Slow in speed
Generally written in high-level language
Easy to understand
Easy to manipulate and use
Bigger in size and requires large storage space
Review Questions
1. Differentiate between system software and application software
2. What are the advantages of packaged software over the in-housed software?
3. Outline the advantages of a word processing program over the use of an ordinary
typewriter
4. What advantages do spreadsheet applications have over manual spreadsheets?
5. Describe four functions of the operating system
6. What is an interrupt?
7. What are the advantages of GUI based operating system over the command line?
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8. Differentiate between multitasking and multi-user operating systems
9. Outline the factors you would consider when buying an operating system.
Relationship between Hardware and Software
 Hardware and software are mutually dependent on each other. Both of them must
work together to make a computer produce a useful output.
 Software cannot be utilized without supporting hardware.
 Hardware without set of programs to operate upon cannot be utilized and is
useless.
 To get a particular job done on the computer, relevant software should be loaded
into the hardware
 Hardware is a one-time expense.
 Software development is very expensive and is a continuing expense.
 Different software applications can be loaded on hardware to run different jobs.
 A software acts as an interface between the user and the hardware
 If hardware is the 'heart' of a computer system, then software is its 'soul'. Both are
complimentary to each other.
SYSTEM START – UP AND CONFIGURATION
Starting a computer
The booting system.
Booting is the process of powering on a computer and starting the operating system.
Booting takes two forms:
Cold booting. The actual starting of a computer which has been initially off.
Procedures for booting up a computer
 When you turn on the computer, you may hear the sound of the cooler fan running.
After a few seconds, lines of text start scrolling up on the screen. This process is
known as Power-On-Self-Test (POST).
 POST checks on the existing drives, basic input and output devices such as
keyboard, monitor and mouse. If a problem is encountered, the POST is halted and
an error message is displayed on the screen.
POST is accomplished by a special firmware program called Basic Input Output
System (BIOS) which is held in a ROM chip mounted on the motherboard.
 After POST, the computer reads some instructions such as the current date and
time from a special memory known as the Complementary Metal Oxide
Semiconductor (CMOS). CMOS is powered by a dry cell that mostly resemble that
of a digital watch. If the cell is down, the computer requires the user to enter the
current date and time.
 Lastly, a special type of computer program used to manage computers called an
Operating System (OS) is loaded to the computer memory.
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Microsoft Windows
desktop
Warm booting. The process of restarting a working computer
To restart;
Click the start button
On the start menu, click the shutdown
Then click Restart
Or, Press Ctrl + Alt + Del
Reasons for restarting a computer
 To recover from errors that cannot be recovered
 When a computer freezes or locks
 After installing certain new software programs
 After uninstalling a hardware device
 After installing a new hardware device like a flash disk
 After uninstalling a software program
 When the computer slows down
 After changing CMOS or BIOS setup
 When a computer has a virus, it can constantly restart itself
Shutting down a computer
It is important that the user follows the correct procedure of shutting down a computer
at all times. If the procedure is not followed, then loss of data, damage of programs
and computer components may occur. To shut down, follow the procedures below:
Ensure that all the work has been properly saved. This process is called saving.
Close all programs that may be currently running
If your computer is running on Microsoft Windows XP or Vista,
a) Click on the Start button
b) On the start menu, click Shut Down
c) On the message box that appears, Click Turn Off
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The Basic Input Output System (BIOS)
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These are software instructions that ensure that all the components of a motherboard work
together.
When a computer is switched on, an electronic charge activates the BIOS instructions
to execute the Power-On-Self-Test instructions known as the POST routine. The
BIOS POST routine performs functions like:
 Interfacing between the hardware and the Operating System
 Interfacing between the processor and the Operating System
 Activating additional hardware BIOS
The Power-On-Self-Test (POST) routine
The POST routine is the sole responsibility of the BIOS in a computer. In this routine,
a set of activities is carried out such as;
 Loading custom settings. During POST routine, the BIOS checks the RAM
storage area known as the Complementary Metal Oxide Semiconductor (CMOS)
for custom system settings. Theses settings may include the type and size of the
various storage devices available on the system, the system data and time,
Input/Output (I/O) ports on the system, etc.

Loading interrupt handlers. The POST also loads the interrupt handlers and
special drivers into memory. Interrupt handlers are the software instructions that
interface between the processor and hardware components. For example, a key
press signal on a keyboard is passed onto the keyboard interrupt handler that
informs the processor the character it represents and eventually the processor
sends it to the Operating System

Loading special settings. For common special drivers like the display drivers, if
the display adapter has its own BIOS, then it is activated at this stage. Otherwise,
the default display driver is loaded.

Reboot checking. At this stage, the POST routine checks whether the current
process is a warm boot or cold boot. This is done by checking the memory address
0000 0472 for a specific value. If the value stored here is 1234h, then it is
considered as a warm boot and the rest of the POST routine is ignored; it instead
loads the Operating System. In case it is a cold boot, each memory address is
checked for consistency and size.

Checking for auxiliary devices. The POST routine the checks and records any
additional external devices attached to the computer through plug in slots. These
devices include the keyboard, printers and other devices

Displaying summary information. The BIOS then displays information on the
screen about what has been checked on the computer. This information includes
the BIOS manufacturer’s name and the interrupt handler, etc.

Passing control to the Operating System. At this stage, it checks for a drive that
contain the boot information as indicated in the CMOS. When the boot
information is found, it is executed and BIOS now passes control to the Operating
System otherwise it halts.
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The type of BIOS on a motherboard depends on the manufacturer and usually all
motherboards come with at least a BIOS chip installed. Among the common BIOS
manufacturers are American Megatrends Inc., IBM, Intel, Phoenix technologies, etc.
How an Operating System organizes information
Most operating systems organize information in a three-tree hierarchy as shown
below.
Information organization tree
Files.
A file is a collection of related data given in a unique name for ease of access,
manipulation and storage on a backing storage.
A file icon
Every file has the following:
1. A unique name and an optional extension. The name and extension are separated
by a period (.). E.g. June. Doc. In this case, the file name is June and the extension
is Doc.
Extensions are used to identify to the type of file, for example:
.doc is as word processor file
.txt is a plain text file
.sys is a system file.
2. The size, date, and time the file was created or modified
Types of files
There are three types of files, namely: system, application and data files.
System files contain information that is critical for the operation of the computer
Application files hold programs and are executable.
Data files contain user specific data
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The table below shows some file extensions and whether it is a system, application or
data file
Extension
File type
Description
.doc
Data
A Microsoft word document file
.txt
Data
A plain text file created using note pad or
DOS editor
.tif
Data
A graphic file created using applications such
as Adobe Photoshop
.exe
Application file
The file that launches a particular application.
E.g. Winword.exe, PM.70.exe, etc
.bat
System files
File containing a series of commands loaded
during boot up
.sys
System files
System files that perform fundamental
operations in a computer
Folders. This is also known as a directory in some operating systems. It is a named
storage location where related files can be stored.
All folders or directories originate from a special directory called root directory or
folder.
The root directory is represented by a back slash (\). A folder or directory may be
created inside another folder or directory. Such a folder is called a subfolder or a
subdirectory.
Factors that affect a computer’s performance
1. CPU clock speed. The CPU clock speed determines how fast a CPU operates. The
higher the CPU clock speed, the faster the computer. CPU clock speed is measured in
Hertz (1 MHz = 1million cycles per second) or Gigahertz (1 GHz = 1,000 Megahertz
= 1 billion cycles per second). Modern PC clocks already have CPU clock speed of
several GHz.
2. RAM size. The more RAM a computer has, the faster it can operate. The reason is
that if the RAM is not sufficient, the computer has to use the hard disk to store data
temporarily which when compared to RAM, has a slower access time.
3. Graphic cards. The quality of a graphic card is another key factor which affects a
computer’s performance. Graphic cards are essential hardware units fixed within a
PC. The role is to convert digital signals from the CPU to the signals that can be
displays on the monitor. The lower the quality, the slower the process.
4. Free hard disk space. The larger the free space on a hard disk, the faster the
computer’s speed; the smaller the free space, the slower he computer processes data.
The hard disk should have enough free space to store temporary data.
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CRITERIA FOR SELECTING A COMPUTER SYSTEM
a. Hardware considerations. There are a number of factors to be considered before
acquiring a computer or hardware accessories. These include:
2. Microprocessor type and speed. The user should consider the microprocessor and
an acceptable speed that meets the user requirements at a fair price.
The processing power, speed and cost of a computer mainly depends on the type of
processor and its clock speed. Some of the microprocessors available today include:
Pentium IV, Intel Celeron, etc.
3. Warranty. The user should consider whether the seller is ready to provide after sales
services. A warranty is an agreement between the buyer and the seller that spells out the
terms and conditions of repairing or replacing a sold product in case of failure or
malfunctions.
4. Cost. The cost of a computer depends on its processing capability, size, whether it is
branded or duplicate. Branded computer are more expensive than the duplicate ones.
5. Upgradability and compatibility. The hardware bought must be compatible and easy to
upgrade
6. Portability. Portable computers such as laptops are ideal for people who do not take most
of their time in office.
7. Special user needs. When selecting a computer hardware, consider the unique user needs.
E.g. if a user has a physical challenge, consider buying voice input devices.
8. Monitor. The choice of a monitor depends on the size, resolution and the technology used
on it. Currently, flat panel displays are replacing CRT monitors.
9. Multimedia capability. This refers to the ability of the computer to process and output
text, sound, video and pictures. A multimedia system consists of speakers, CD/DVD drive,
sound card and a SVGA monitor.
b. Software considerations:
1. Authenticity. This refers to the validity of an item. The user should make sure the
software is an original copy accompanied with the developer’s license and certificate of
authenticity.
2. Documentation. These are the manuals prepared by the developer having details on how
to install, use and maintain the software.
3. User needs. It should be able to meet the needs of the user. For example, if a user needs to
type only documents, then he/she would go for a word processor.
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4. Reliability and security. A good software should be reliable and have security that
protects data from illegal access.
5. User friendliness. A good software should be easy to be operated on computers by users.
6. Cost. The cost of software must be carefully considered before acquiring them against the
benefits they are likely to bring. Software tends to be more expensive than hardware. It is
not advisable to always go for freeware because some of them may contain malicious
programs.
7. Compatibility and system configuration. A software product should be compatible with
the existing hardware, operating system or application programs and should be upgradable.
8. Portability. The user should consider whether a given program can be copied or installed
in more than one computer.
Review Questions
1. Highlight hardware and software factors that you would consider when purchasing
a computer
2. Define the term booting a computer
3. Briefly explain the steps needed for a complete cold boot
4. Differentiate between cold booting and warm booting
5. Outline seven reasons for carrying out a warm boot.
Revision Questions
1. Write the following abbreviations in full:
a) CPU
b) ALU
c) CU
d) ROM
e) RAM
2. Give examples of special memories found in the CPU
3. What do the following abbreviations in relation to storage capacity stand for?
a) KB
b) MB
c) GB
d) TB
4. Differentiate between MICR and OCR
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COMPUTER SECURITY
Computer security refers to the safeguards required to control access to information and
protect computer-based systems against the hazards to which computer systems are exposed.
Security controls help to ensure high system standards and performance by protecting against
hardware, software and people failure.
Computer systems and data in storage are vulnerable to several hazards which include:
 Computer virus
 Fire
 Natural disasters
 Environmental problems
 Disruption
THREATS TO SECURITY
Computer Viruses:
A computer virus is a deviant program that attaches itself to the computer system and
destroys its operations or corrupts data.
NB: a virus burrows in the computer memory and keeps consuming or occupying
successively the idle parts of the memory until the system crashes.
How are viruses developed?
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

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Through infected diskettes from infected computer systems
Through sales demonstration applications
Through networks
Through software updates
Through free computer games on the net, etc
Through pirated software. These are software that have been copied without the
permission of the owner.
 From software laboratories. Programs can be infected without the manufacturer’s
knowledge
 Through the use of the network (internet)
 An employee of an organization can also introduce such viruses knowingly.
Symptoms of viruses
 Annoying messages
 Adding garbage to files
 A computer system switches on and off
 Unnecessary variations in computer processing speeds
 Deletion of saved files or destructive functioning of the computer system
 The computer system fails to start (boot failure)
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 Unprecedented screen color changes
 Crashing of the hard disk
 Reformatting of the hard disk
 Corrupted files and applications
Types of viruses
Virus classifications can be based on the following:
Environment
Operating system
Different algorithms of work
Destructive capabilities
1. Boot sector viruses (BSV)
These are viruses which attach themselves and reside in programs containing
instructions for booting or powering up the computer system. E.g. anti-CMOS virus,
Anti-EXE, etc.
2. File viruses
These are viruses which attach themselves to files which loads a program. I.e.
executable files. E.g. in DOS, files with extensions “com” or “exe”
3. Multipartite viruses
These viruses combine the traits of both the file and boot sector viruses. E.g. junkie
virus, parity boot viruses, etc.
4. Macro viruses
These viruses are found inside common data files such as those created by e-mails,
spreadsheets, and word documents. They are routine viruses or syntax viruses. E.g.
Concept virus in word documents.
5. Logic bomb.
These are viruses set to cause danger at a set date or time.
6. Trojan horse.
This is a virus that places an illegal and destructive instruction in the middle of a
genuine program or file. Once the program is run, the Trojan horse is also activated to
begin destruction. E.g. Format C virus.
Malware – Malware is a short form for malicious software. It refers to a software that
is intended to damage or disable computers and computer systems. It can appear in
the form of executable cod, scripts, active content and other software.
Malware is a general term used to refer to a variety of forms of hostile or intrusive
software. The term badware is sometimes used and applied to both malicious
malware and unintentionally harmful software
Malware includes the following:
Spyware/adware - refers to a category of software that, when installed on your
computer, may send you pop up ads, redirect your browser to certain websites that
you visit
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How to protect a computer system against viruses
1. Buy software from legal vendors
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2.
3.
4.
5.
Avoid running unchecked or scanned files.
Avoid running files with an attachment from an unknown source on the network.
Backup your files and folders regularly
Use Netware with strong validation checks and in-built firewalls. e.g. Linux (i.e.
Hardware and software which can limit unauthorized data through networks to reach
your workstation)
6. Disable auto micros functions for macro viruses
7. Use antivirus programs. These are utility programs used to scan files and programs in
order to detect, destroy or quarantine files infected with viruses. E.g. Avast antivirus,
MacAfee, Kaspersky, AVG, etc.
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Routines to enhance or boost computer security of a company or organization.
Computer users must recognize their role in security. If a high level priority is
assigned to security, employees must be made aware of it and the security measures
that must be taken.
A company must recognize the need for a well-trained security force maintain the
premises.
People who will have access to computer rooms, terminals and storage facilities
should be screened.
Safeguard computers with strong doors and padlocks or use security guards to
guarantee its safety
Employees who stay beyond legal and ethical boundaries must be discharged.
Whenever an incident occurs, people involved must be disciplined accordingly
There must be only one entrance into the building with a guard stationed there all the
time
Packaged good getting in and out of the building should be inspected
Access to computer facility should be limited to only those whose presence is needed.
Visitors must be kept out.
Record on visitors who enter the computer room must be kept.
Tapes and diskettes must be locked, if possible in fireproof safes.
Backup copies should be made and kept safely elsewhere under the control of a
responsible person like a librarian, chief programmer, etc.
Backup files are copies of important files that should be regularly saved on separate
disks or tapes and clearly labelled.
Uninterruptible Power Supply (UPS) units should be installed from power backup to
provide continuous processing in case of power blackout.
Operators must be rotated such that they do not handle the same work always.
Passwords must be used to gain entrance into computer programs.
All equipment should be covered with plastic covers when not in use.
The premises, personnel and computer systems must be insured. Note that this does
not replace information in case of damages.
Two similar computer systems can be run side by side in different geographical
locations to give cover to each other.
Strict control must be on every input and output to check whether the storage devices
are infected or free form viruses.
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
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


Establish an emergency procedure in case of fire outbreak.
Guards should be placed at strategic points of the computer facility. All visitors who
are given permission to tour the premise must be escorted by a security guard.
All persons entering the computer room must sign a register indicating time of entry and
departure respectively.
Sensitive reports must never be disposed of by simply throwing them in waste
containers.
The building should be constructed from concrete slab.
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COMPUTER/COMMUNICATION NETWORKS
A Computer network is the interconnection of two or more computers and other
devices for purposes of sharing information and resources
The computers on a network must be linked by a medium such as cables, a
wireless device or a telecommunications system in order to exchange data
The network may be limited to a group of users in a local area local area network,
or to a wide area network covering several cities or regions, or the entire world in
case of the Internet
Reasons for Computer networks instead of standalone computers?
To Allow users to share information,
To enable sharing of software,
To enable sharing of hardware
To enable communication between computer users through tools like e-mail
To enable data communication ie transmission of electronic content over a
given medium
 To ensure security of data by putting in place administrative controls over
the network
 To share databases
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Factors to consider for a network choice
Size of the organization. A peer-to-peer network is ideal for a small organization
Needs of the network. E.g. network administrator, hardware and software, etc.
Level of data security needed. A peer-to-peer network is not very secure
Amount of network traffic expected. (band width)
Network budget for the network system development and servicing. A linear bus
network may be the least expensive one to install. You do not need to buy
concentrators.
Level of administrative support available
Type of business or organization.
Length of cable needed. The linear bus network uses shorter length of cable
Cable type. The most common cable in schools is unshielded twisted pair, which is
most often used with star topology.
Future growth. With a star topology, expanding the network is easily done by
adding another concentrator.
Advantages of a computer network
 It Facilitates easy communications e.g. through Electronic mail
 It Reduces on cost by sharing hardware like printers and sharing software
among network users since one device is jointly used on the network instead
of installing devices to each computer
 it allows for tight control over who has access to data in the system
 It enables sharing of data and information stored on any other computer on
the network
 It enables online learning and collaborative research
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 It allows access to free common databases and databanks like free software
and ATM services
 Software is easily upgraded on the network since it is done at ago on the
server
 Computer networks enable centralized administration, control and
monitoring of individual users on the network
 Computer networks enable workgroup Computing Workgroup software
allows many users to work on a document or project concurrently
 Networks provide a very rapid method for sharing and transferring files
instead of using time consuming method of using movable disks to transfer
data from one computer to the other
 It enables flexible access Users can log on and access their work from any
workstation on the network
The disadvantages of Networks
 High Initial cost of installing a network on Cables, network cards, network
equipment and software, and the installation may require the services of a
technician
 High costs on network administration and maintenance of a network
 Time can be wasted on social networks instead of doing meaningful work
 The entire network fails if the server crashes, when this happens, the entire
organization loses access to necessary programs and files
 High risk of data corruption, since many users will be using the system to
access the same documents, some of whom may be careless or deliberately
tamper with it
 Increased exposure to hackers which puts private data at risk
 There is a greater risk from viruses, because they are easily spread between
the computers share a network
 A break in the communication channel can stop the entire network
 Information theft
 Change of file names by hackers and crackers
 Abuse of data e.g. malicious deletion of Data
The Components of a computer network
These are elements that make up a computer network:
 Network interface card
 Terminal nodes e.g. Computers and Printers
 Communication (Network) media/Channels e.g. Ethernet cables and access
point
 Network software e.g. network operating system
 Switches or hubs
The Network hardware devices include:
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Hubs/concentrators
MODEM
Switches
Repeaters
Bridges
Routers
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 Network Interface Cards (NICs).etc
Network Interface Cards (NICs)/network adaptor
A network interface card is an electronic communication device that connects a
computer to a local area network
Some NICs are built on the motherboard while others built on a circuit board fitting
into an expansion slot inside the computer
The Type of NIC determines the speed and performance of a network
There are three common NICs:
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Ethernet cards,
Local Talk connectors,
Token Ring cards
MAC address
A Media Access Control address (MAC address or physical address) is a unique
identifier assigned to network interfaces
Hubs/Concentrators
A hub is a device that connects multiple devices to the network and its function is
to send and receive signals along the network between the devices connected to it
by broadcasting the data to all the devices/computers
It serves as a central meeting place for cables from computers, servers and
peripherals on the network
The entire network shuts down if there is a problem on a hub
Repeaters
A repeater is a device that is used to regenerate and amplifies signals along a
communication channel to create long-distance networks by placing it between two
segments of the network channel to overcome distance limitations
Bridges
A bridge is a device that links two local area networks that use the same address
method or protocol
It accepts all packets from each network addressed to devices on the other, buffers
them, and retransmits them to the other network
Switches
A switch is a high-speed device that sends the data packets only to the destined
computer keeping track of which hardware addresses are located on which network
segment
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It maps the IP address with the MAC address of the LAN card
Switches are used in the LAN, MAN and WAN
Router
A router is a device that links one network to other physically and logically separate
networks
The main function of the router is to sort and send data packets to their
destinations based on their IP addresses
Gateway
A gateway is a device that connects the LAN with the internet
A gateway interconnects networks with different network protocol technologies by
performing the required protocol conversions
MODEM
A modem modulates outgoing digital signals from a computer or other digital device
to analog signals for a telephone line and demodulates the incoming analog signal
and converts it to a digital signal for the digital device
Fax modem
A fax modem is a device that enables a computer to transmit and receive
documents as faxes
Communication media/channels
Also known as communication links or Data links
A communication channel is a medium over which Data travels/is transmitted
from one computer (device) to another
Forms of Data communication
Data transmission, digital transmission, or digital communications is the physical
transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint
communication channel
Examples of such channels are copper wires, optical fibers, wireless
communication channels, and computer buses
The data is represented as an electromagnetic signal, such as an electrical voltage,
radio wave, microwave, or infrared signal
Data is transmitted over networks using signals, which are transformed, or
encoded, by computers into the voice, video, graphics, and/or the print we see on
our computer screens
The signals used by computers to transmit data are either digital or analog
Analog signals are continuous signals that vary in strength Sound is an example of
an analog signal
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Digital signals are discrete/discontinuous
Either there is a signal or there isn't a signal, therefore they are represented by on
(1) and off (0) pulses
Modulation and Demodulation of Signal
Modulation refers to the process of converting digital signals into analog form so
that data can be sent over the phone line
Demodulation is the process of converting the analog signals back into digital form
so that they can be processed by the receiving computer
The hardware that performs modulation and demodulation processes is called a
MODEM
Serial transmission
Serial transmission is the sequential transmission of one bit of signal at a time sent
over a single wire Low data transfer rates are possible, but can be used to transfer
data over longer distances
Parallel transmission
Parallel transmission is the simultaneous transmission of the signal elements of a
character or other entity of data over two or more separate paths
Multiple electrical wires are used which can transmit multiple bits simultaneously,
which allows for higher data transfer rates than can be achieved with serial
transmission
Asynchronous Data transmission
Transmission where each group of digital or analog signals making up the code for
one character is separated and individually wrapped with a start BIT and a stop
BIT and an error check BIT
Asynchronous transmission is relatively slow because of the extra bits that must be
sent with the data bits for each character
Synchronous Data transmission
This is the transmission where characters are sent as blocks of signals with header
and trailer bytes at the beginning and end of the block
Synchronous transmission is faster because characters are sent as blocks; it is
therefore used to transmit large volume of data at high speed
Duplex transmission
A duplex communication system is a point-to-point system composed of two
connected parties or devices that can communicate with one another in both
directions An example of a duplex device is a telephone
Full-Duplex (FDX) transmission
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A full-duplex (FDX) system, sometimes called double-duplex, allows
communication in both directions simultaneously e.g. Land-line and Cell telephone
networks are full-duplex, since they allow both callers to speak and be heard at the
same time
Half-Duplex (HDX) transmission
A half-duplex (HDX) system provides communication in both directions, but only
one direction at a time (not simultaneously)
An example of a half-duplex system is a two-party system such as a walkie-talkie
Simplex
Simplex is a communication that occurs in only one direction For example, Radio
and
Television broadcast, communication between a mouse and computer
Point to point transmission
A point-to-point connection refers to a communications connection between two
nodes or endpoints
Multi-Drop transmission
A transmission bus in which all components are connected to the electrical circuit
A process of arbitration determines which device sends information at any point
The other devices listen for the data they are intended to receive
There are both physical (cable or wired) media, and wireless media
Transmission media
Common transmission media include the following:
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Twisted pair cables
Coaxial cables
Fiber optic cables
Terrestrial Microwave
Radio
Satellite
Twisted pair cables
A twisted pair cable consists of eight insulated copper wires twisted in pairs and
arranged in a regular spiral pattern to minimize the electromagnetic interference
between adjacent pairs
There are two types of twisted pair cables;
 Shielded twisted pair (STP) and unshielded twisted pair (UTP)
Each pair is twisted to decrease interference
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Advantages of twisted pair cables
 They are relatively cheap to use because its cost per unit length is low
 They are convenient to use because they are small in size
 They are easy to install because of their flexibility it is easily strung around
the room or wall
 Shielded twisted pair has a foil shielding to help provide a more reliable data
communication
 Because UTP is small, it does not quickly fill up wiring ducts
 TP is easy to terminate
The Disadvantages of twisted pair cables
 Used over a short distance, usually less than 100 meters
 Twisted pair’s susceptibility (prone) to the electromagnetic interference
which leads to signal loss
 They are easily damaged Especial the UTP
 They are low frequency cables So they are not suitable for transmission of
very high frequency signals like cable TV, TV antenna and radio antenna
signals
Coaxial cables
A coaxial cable is one that consists of two conductors that share a common axis
hence the name “co-axial” The inner conductor is a straight wire, and the outer
conductor is a shield that might be braided or a foil.The two conductors are
separated by a nonconductive element
Features of coaxial cable (Advantages)
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Both conductors share a common center axial, hence the term "co-axial"
It has a high bandwidth
It is highly resistant to signal interference
It is used for long distance (300-600 meters)
Disadvantages of Coaxial cables
 It is quite bulky and sometimes difficult to install
 the most common type of connector used with coaxial cables is the BNC
connector
 It has higher installation costs
 Coaxial is prone to lightning strikes which damage the cables or equipment
on which it is connected
 It is more expensive than twisted pair cables
 It is not flexible
The Fiber Optic cables
Fiber Optic Cable is a transmission medium, which is made up of hundreds to
thousands of fine, light-conducting filaments made up of glass or plastic
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Data is changed into pulses of light, which are sent down these glass or plastic
fibers at very high speed over long distances. Fiber optic cable consists of a center
glass core surrounded by several layers of protective materials
Advantages
 It has protection against environmental interference
 It has high data carrying capacity (bandwidth of up to 2 Gbps)
 It can be used over greater distances due to the low loss, high bandwidth
properties
 It can be used for 2km without the use of a repeater
 Fiber optic networks operate at high speeds -up into the gigabits
 Greater resistance to electromagnetic noise such as radios, motors or other
nearby cables
 Fiber optic cables cost much less to maintain
 They are light weight and small in size, which makes them ideal for
applications where running copper wires would be impractical
 It is difficult to tap data over a fiber optic without being noticed due to
difficulty of connecting new nodes when others are switched on
 They are poor conductors of electricity which eliminates the possibility of
electrical shocks
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Disadvantges
Fiber optics are expensive compared to the other types of cables
They are difficult to install and modify, therefore require skilled installers
It is difficult to add additional nodes on the network
It is much more costly than other cables to install
Wireless media
Wireless communication technology, is one where the transfer of information over a
distance is done without the use of cables (wires) as a medium
Wireless technology is applied in Local area networks (WLANs), extended local area
network, and connecting a network to another network
Wireless technology overcomes the inconvenience of using too many wires for
communication
Wireless is appropriate to use in places where cabling is practically impossible
Wireless increases flexibility and mobility at the work place because workers can sit
anywhere with their computers without being limited by the extent of cable
connections
Types of wireless media
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Radio
Microwave
Infrared
Blue tooth
Microwave transmission
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Microwave transmission refers to the technology of conveying information or energy
by the use of radio waves whose wavelengths between one meter and one millimeter
Microwave transmission requires line of sight in order to work properly because it
is a point-to-point connection
This means microwave must be transmitted in a straight line (with no obstacles
such as buildings or hills in the line of sight between the microwave stations)
The distance covered by microwave signals is based upon the height of the antenna
Microwave communication can take two forms: terrestrial (ground) links and
satellite links
Terrestrial microwaves use Earth-based transmitters and receivers, sending data
from one microwave station to another
Earth-based transmitters
Microwave antennas are usually placed on top of buildings, towers, hills, and
mountain peaks to avoid obstructions
Microwave transmissions use parabolic antenna and dishes that produce a narrow,
highly directional signal
Limitations of Microwave
 Microwave signals are highly subjected to atmospheric interference
 Microwave can be exposed to electronic eavesdropping
Communications Satellites
Satellites are communication devices stationed in space and use microwave radio
as their telecommunications medium to communicate with the earth based
communication facilities
Satellites are capable of receiving and relaying voice, data, and TV signals to and
from earth based communication facilities (earth stations) that use parabolic
antennas (satellite dishes) to communicate with the satellites
Satellite microwave communication is flexible and possible with most remote sites
and with mobile devices, because no cables are required, which enables
transmission with ships at sea and motor vehicles
Radio transmission
Radio is the transmission of signals, by converting them into electromagnetic waves
The electromagnetic waves are transmitted in space towards the destination
Electromagnetic waves are intercepted by the receiving Antenna The signal power is
collected at the receiving antenna
Radio waves are not a line of sight transmission, therefore not affected by presence
of objects between the transmitter and receiver
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Infrared transmission
Infrared (IR) light is electromagnetic radiation with longer wavelengths than those
of visible light
Infrared signal is usually transmitted across relatively short distances to transmit
data between personal devices for example, between a computer and a cell phone
Infrared can be either beamed between two points or broadcast from one point to
many receivers
Bluetooth
Bluetooth is a short range wireless technology which Operates at approximately
1Mbps with range from 10 to 100 meters Bluetooth is an open wireless protocol for
data exchange over short distances
Wireless Local Area Network (WLAN)
A WLAN is a network that provides wireless network communication in a small
geographical area using high frequency radio signals or infrared light beams or
microwave or Bluetooth to communicate between the workstations and other
devices
Clients communicate with the access point using a wireless network adapter
similar in function to a traditional Ethernet adapter
A wireless local area network (WLAN) links two or more devices using a wireless
distribution method (spread-spectrum)
Most modern WLANs are based on IEEE 80211 standards, marketed under the WiFi brand name
The WAP usually connects to a wired network, and can relay data between wireless
devices and wired devices
Wireless LANs use spread spectrum technology to enable communication between
multiple devices in a limited area. An example of open-standards wireless radiowave technology is IEEE 80211b.
The wireless LAN network devices
Wireless network adaptors, wireless access points, wireless bridges, wireless
routers, and antennae
Wireless Access Point
A wireless access point (WAP or AP) is a device that connects wireless
communication devices together to form a wireless network
To be able to communicate with a wireless device, the computer must have a
wireless network adaptor
WLAN adaptor/card
This is a device that provides an interface between the network operating system
and an antenna to create a wireless connection to the network
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Access point (AP)
AP is the wireless equivalent of a LAN hub. It receives buffers, and transmits data
by means of a wireless antenna between WLAN and a wired network
An outdoor LAN bridge is a device used to connect LANS in different buildings
WLAN can be built with either of the following topologies:
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Peer-to –Peer (Ad hoc) topology
Access Point –based topology
Point –to–Multipoint bridge topology
Peer –to-Peer (ad hoc) topology
In the ad hoc topology devices are configured to communicate directly to each other
Access point –based topology
This is where access point(s) are used to enable a wireless device to communicate
with any other wired or wireless device on the network
Access points are used to bridge traffic onto a wired or wireless backbone, or where
network devices are interconnected using access points
Point –to –multipoint bridge topology
This is where a wireless bridge is configured to connect a LAN in one building to a
LAN in another building even if the buildings are not close together but within a
clear line of sight
Wireless Wide Area Network (WWAN)
This is a wireless network over a wide area in which separate areas of coverage are
connected wirelessly
Wireless Wide Area Networks equipment
Long distance wireless equipment include:
 Satellite
 Microwave dishes
 Microwave antennae
The Wireless Web
The wireless web refers to the use of the World Wide Web through equipment like
cellular phones, Pagers, PDAs, and other portable communications devices that
offer anytime/anywhere connection
Wireless Application Protocol (WAP)
The Wireless Application Protocol (WAP) refers to a group of related technologies
and protocols widely used as a standard protocol in providing Internet access to
mobile phones or other small mobile devices
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WAP protocol involves a website transmitting scaled-down versions of normal web
pages specifically optimized for use by wireless telecommunications devices such as
smart phones
Advantages of a wireless network
 Cost reduces because there is no need to buy and lay cables
 Work is reduced for setting up the network because there are no cables
involved
 It enables usage of a variety of devices on network such as personal digital
assistants (PDA), blackberry devices, and other cell phones
 It enhances mobility and flexibility of a network due to ability to move
devices without the restriction of cables for example, mobile phones and
laptops
 Fast data transfer rates are possible where there are no environmental
obstacles
 It also allows an organization to offer visitors
 Wireless technology makes it easy to set up temporary network installations
These situations include any temporary department set up for a specific
purpose that soon will be torn down or relocated
 Wireless technology is becoming cheaper and affordable over time
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Disadvantages of a wireless network
Poor security of data on a wireless network, outsiders can easily log on an
unsecured wireless network
They are slower than LANs using cabling
They are prone to electrical interference from lights and radios
They are Subject to obstructions such as walls
Wireless access points and WI-FI technology in general have a limited
spectrum/range Signal strength decreases as the range increases
Network software
Network software are Communication programs that are used in combination with
network devices to enable transmission of data between network terminals
They have features such as Dialing, file transfer, internet access and others
Categories of network software
 Network operating system (NOS)
 Network protocols
A network operating system is a supervisory software program that resides on the
server and controls a network by;
(i) Defining who can use the network
(ii) Determining how information is shared
(iii) Controlling access by multiple users to network resources such as files and hard
ware,
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(iv) Providing for certain administrative functions, including security
Examples of common NOS;
Novell Netware, Microsoft Windows NT, windows server*, AppleShare, UNIX, Linux
NOS carries out administration activities which include:
 Managing the Security of the network by providing Security features such as
authentication, authorization, logon restrictions and access control
 File management
 Providing basic operating system features such as support for processors,
protocols, and automatic hardware detection and supporting multi-processing
of applications
 Providing name and directory services
 Coordinates the activities of multiple computers across a network
 Providing file, print, web services, back-up and replication services
Network protocols
A protocol is a set of rules and procedure (standard) for connection and data
transfer between devices on a network Protocols control all aspects of data
exchange, which include the following:
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How
How
How
How
How
the physical network is built
devices connect to the network
the data is formatted for transmission
that data is sent/transmitted
to deal with errors in data transfer
The Protocols are created and maintained by a number of different organizations
and
Committees including:
 Institute of Electrical and Electronic Engineers (IEEE),
 American National Standards Institute (ANSI),
 Telecommunications Industry Association (TIA),
 Electronic Industries Alliance (EIA)
 International Telecommunications Union (ITU)
Commonly used protocols
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TCP/IP-transmission control protocol/Internet protocol
HTTP-Hypertext transfer protocol
FTP-file transfer protocol
POP-post office protocol
SMTP-Simple mail transfer protocol
IPX/SPX-stands for Internetwork Packet
Exchange/Sequenced
Packet Exchange IPX and SPX are networking protocols used primarily on
networks using the Novell NetWare operating systems
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 NETBEUI-(NetBIOS Extended User Interface) is a new, extended version of
NetBIOS, the program that lets computers communicate within a local area
network it does not support the routing of messages to other networks,
 Telnet (TELecommunication NETwork) for Remote access between computers
 IMAP; Internet Message Access Protocol
 The Point-to-Point Protocol (PPP) which is a data link protocol commonly
used in establishing a direct connection between two networking nodes
TCP/IP configuration
TCP/IP configuration is the setting involves assigning of IP addresses. This
Configuration is either Static or dynamic
Static IP configuration
Static networks are setup such that each node always has the same IP address
Static
IP addresses are fixed addresses that only change manually
Dynamic configuration
Dynamic networks are setup in such a way that the IP addresses for the computer
are controlled by the DHCP server
DHCP (or Dynamic Host Configuration Protocol), is a means by which an IP address
may be assigned to a computer on boot
When the DHCP client boots, it puts out a request on the Local Area Network for a
DHCP server to assign it an IP address
Domain Name system
The Domain Name System (DNS) translates the easily memorized domain names
(e.g.
www.google.com) to the numerical IP addresses needed for the purpose of locating
computer services and devices worldwide
The Domain Name System is an essential component of the functionality of the Internet
TYPES OF NETWORKS
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Local Area Networks (LANs)
Wide Area Networks (WANs)
Metropolitan Area Networks (MAN)
International network (Internet)
Local Area Network (LAN)
A LAN is a group of computers, printers and other devices interconnected within a
small geographical area such as a room or a building
The devices must be interconnected using a medium such as cables or a wireless
medium
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LANs allow individual users to locally share computer files and hardware such as
printers and disks
Metropolitan Area Networks (MAN)
A MAN is a computer network larger than a LAN but smaller than a WAN
connecting
Computers and LANs which are geographically separated but in same city
Wide Area Networks (WANs)
A WAN is a number of computers and peripherals connected together over a large
geographical distance such as across districts, cities or re.g.ions (10 km and more)
WANs make use of a wider variety of communication media compared to LANs
including Telephone lines, Microwave links (wireless), Satellite connections and fiber
optic cables
Components of a LAN
A LAN is made up of the following components:
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Workstations
Network interface cards
Peripheral devices
Networking media
Networking devices
Network server
Types of LANs
 Peer to Peer network
 Client-server
Peer to Peer
This is an interconnected group of equal computers where there is no hierarchy
among them, each computer acts as both a client and a server to others on the
network. Each computer has resources it shares with others on the network
Merits of Peer-to-Peer Network
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It’s very easy to set up
It’s appropriate in case of a small network (few computers)
Inexpensive to set up and maintain
Enables easy sharing of devices such as CDs and printer
It’s flexible
Demerits of Peer-to-peer Network
 It lacks security due to absence of a server
 There is no central administration
 It’s not appropriate for big networks (cannot be used for big networks)
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Client server network
A network that consists of a central computer (the server) on which other
computers (clients) are connected. The central computer providing services to client
computers
NETWORK SERVER
A server (Network server) is a computer on a network that controls and manages
the network resources, making them available to its clients (computers connected
to it)
Client Computer
Client computer is one that is connected to the Network server to receive services
from the server
Advantages of Client-server network
 It offers a reliable centralized storage and sharing of files
 It ensures high security of the network through access controls installed on the
server
 It is easy to monitor the network performance on the server
 It is easy to solve network problems
 It’s cheap to install software which can be done on the server alone instead of
all computers on the network
Disadvantages of client-server network
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It’s expensive to setup
Extra expenses on buying a server computer
Extra expenses on hiring a network administrator
The server is one point of failure In case the server fails to work, the whole
network comes to a standstill
Types of Network Servers
File server: One that stores various files and making them available to network
users
Application servers: stores application software packages run directly on it and
made for users on the network
Printer server: a central computer that manages a networked printer from a single
location
Web server: It allows users to access outside networks, also providing web
content/web pages to users
Mail server: Manages mail by receiving, moving and storing mail on the network
Proxy server: A computer placed between a LAN and an external server or
networks (Internet), to filter requests and restrict access to data
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A proxy server receives a request for an Internet service from a user If the request
passes filtering requirements, looks in its local cache of previously downloaded Web
pages If it finds the page, it returns it to the user without needing to forward the
request to the Internet
If the page is not in the cache, the proxy server, acting as a client on behalf of the
user, uses its own IP addresses to request the page from the server out on the
Internet When the page is returned, the proxy server forwards it on to the user
Network Topology
Topology is the physical and logical arrangement of a local area network, hence
physical topology and logical topology
The physical topology of a network refers to the physical arrangement of cables,
computers, and other peripheral devices in relation to each other on a network.
Logical topology is the method used to pass information between workstations on a
network
Types of physical Network topologies
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Bus network topology
Ring network topology
Star network topology
Hierarchical network topology
Mesh network topology
Hybrid topology
Tree topology
Point-to-Point
Bus topology or linear bus topology
 Bus network topology is one that consists of a main, central cable known
as the backbone with a terminator at each end of it, on cable all devices on
the network are connected to the main/central cable
Advantages of Bus topology
 It is less expensive than a star topology due to less footage of cabling, only
needs one main cable and no network hubs
 It is good for smaller networks not requiring higher speeds
 It has a high transmission speed if coaxial cable is used
 It is easy to add new workstations on the network
 Multiple servers can be used
 Easy to connect a computer or peripheral to a bus
 Requires less cable length than a star topology
Disadvantages of Bus network
 It is Limited in size and speed
 The Entire network shuts down if there is a break in the main cable
 Difficult to troubleshoot It is difficult to identify the problem if the entire
network shuts down
 It is less secure since all data is transmitted down one main cable
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 Transmission slows down as more work stations are added
 If the main cable fails, then all workstations are affected
 Ring topology
This is an arrangement where each device on the network is directly connected to
one another in the shape of a closed loop or ring
Each data packet is sent around the ring until it reaches its final destination
Advantages of ring topology
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It is Cheaper to install since there is less equipment required
High speed can be achieved as each workstation can boast the signal
Signal flow is one direction which avoids the danger of data collision
Where a double ring is involved data flow is continuous even in cases where
one ring brakes down
Disadvantages of a Ring network
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Moves, additions and changes of devices affect the entire network
High expense since it requires fixing two network cards on a single computer
If a connection in a single ring is broken the entire network stops working
Having no central server makes data very insecure
Fairly slow as data pass through a number of workstations before reaching its
destination
 Star topology
A star is a topology designed with each device on the network connected directly to
a central network hub or switch such that Data from a device passes through the
hub or switch before continuing to its destination
 Extended Star topology
This is a network where more than one star network topology are connected
together to form a big/extended local area network
At the center of the star is a hub or a switch
Advantages of Star topology
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It is suited for large networks
It is easy to expand the network without ne.g.atively affecting it
If one cable or station fails, the entire network is not affected
It is easy to install, maintain and troubleshoot because the problem usually
isolates itself That is, it’s easy to detect faults and to remove parts
Cabling types can be mixed to maximize efficiency
High speed transmission is possible since each station has a dedicated cable
Greater security as connection from one station to server is unique
No disruptions to the network when connecting or removing devices
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Disadvantages of Star topology
 Breakdown of the switch/Hub becomes a single point of network failure
 It’s expensive to set up due to increased cabling costs and the need for a
switch or hub
 Mass of cables around in case of a large network
 If the cable fails the workstation cannot receive data via any other route
 The server can get congested as all communication must pass through it
 Requires more cable length than a bus topology
 If the hub or switch fails, nodes attached are disabled
 Hierarchical topology
It is like the extended star topology, except a computer controls traffic instead of a
hub or a switch
 Hybrid Topology
Hybrid Topology is a network that has two or more different types of physical
topologies connected to each other to form a complete network. There are many
different combinations that can be created such as bus plus Star (tree)
 A hybrid topology is easier to connect to other computers than some other
topologies
 The hybrid topology has a faster connection
 Tree topology
This is a network that combines characteristics of bus and star topologies; It
consists of groups of star connected workstations connected to a bus backbone
cable Tree topologies allow for the expansion of an existing network, and enable
organizations configure a network to meet their needs
Advantages of Tree topology
 Allows for Point-to-point wiring for individual segments
 Supported by (compatible with) several hardware and software
Disadvantages Tree topology
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Overall length of each segment is limited by the type of cabling used
If the backbone line breaks, the entire segment goes down
More difficult to configure and wire than other topologies
Mesh topology
This is a network where each device has its own direct link to each of all the other
devices on the network
It provides each device with a point-to-point connection to every other device in the
network
A mesh topology is implemented to provide as much protection as possible from
interruption of service
 Damage of one or a few cables or computers may not have vital impact
except the involved
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 Computers Data can be routed through any other computer connected to the
network
 It is the most expensive and difficult to maintain topology because each
device has a Point-to-point connection to every other device
 Point-to-Point Topology
Point-to-point (PTP) topology connects two nodes directly together. The following
examples are pure point to point links:
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Two computers communicating via modems
A mainframe terminal communicating with a front end processor
A workstation communicating along a parallel cable to a printer
Considerations When Choosing a Topology/network to have:
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Cost of installation. A linear bus network may be the least expensive way to
install a network; you do not have to purchase concentrators
Number of computers and other devices to connect/size of the organization
The architecture of the building to be used
The purpose of the network
Distance of connectivity
Safety provisions of the network
Personnel provisions/technicalities involved
Ease in accessing the network
Length of cable needed. The linear bus network uses shorter lengths of cable
Future growth With a star topology, expanding a network is easily done by
adding another concentrator
Cable type to use. The most common cable in schools is unshielded twisted
pair, which is most often used with star topologies
 Logical topology (Media Access Method)
Logical topology is how computing devices access the network and send data over
the network. The logical topology of a network determines how the devices
communicate across the medium
There are four commonly used media access methods:
Ethernet, Token Ring, Local Talk, and FDDI
1. Ethernet (Physical/Data Link layers)
Ethernet is a type of local area network technology that uses coaxial cable or
special grades of twisted pair wires. Ethernet is also used in wireless LANs
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The most commonly installed Ethernet systems are called 10BASE-T; (Baseband
transmission)
Technology of speeds up to 10 Mbps and more using twisted pair cables
2. Token Ring
A network topology in which computers access the network through token-passing
A Token is a special packet that contains data and acts as a messenger/carrier
between each computer and device on a ring topology
Each computer must wait for the token to stop at its node before it can send data
over the network so as to avoid collision of data packets on the network
3. FDDI (Fiber Distributed Data Interface)
FDDI is a network topology that is used primarily to interconnect two or more local
area networks, often over large distances
It uses fiber optics for speeds of up to 100 Mbps
Packet switching
This is a data transmission technique which involves transmitting and routing of
messages by dividing the electronic message/data into packet segments and
sending them sequentially over a network channel which are then reassembled into
the original message at their destination
Circuit switching
A method of communicating in which a dedicated communications path referred to
as a circuit or channel is established between two devices through one or more
intermediate switching nodes before communication between the devices takes
place
Digital data is sent as a continuous stream of bits on a circuit
Each circuit that is dedicated cannot be used by others on the network until the
circuit is released and a new connection is set up
The telephone system uses circuit switching
NETWORK AND DATA SECURITY
Network and data security consists of the provisions made on computer network
and policies adopted by the network administrator to protect the network and the
network-accessible resources from unauthorized access to data, as well as
guarding against Data loss and the effectiveness (or lack) of these measures
combined together
Solutions to network security problems
 Backing up of all important data
 Lock and Key to ensure physical security
 Combination Locking Mechanisms
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 Card Readers and Proximity Readers They work by reading a magnetic
signature off an access card or token
 File encryption-Encryption involves converting data into a form that cannot be
easily understood by others
 Biometrics This is a form of identity access management and access control
which uses measurable physical and behavioral characteristics of individuals
as a way of identifying them as the authentic users
 Examples of biometrics that might be used to authenticate a user include
fingerprints, retinal patterns, or speech/voice
 Install a firewall-The key defense against Internet attackers is an Internet
firewall A firewall is specialized software, hardware, or a combination of the
two The purpose of an Internet firewall is to prevent unwanted or malicious IP
packets from reaching a secure network
 Install an Anti-virus and other malware software programs to detect, report
and (sometimes) disinfect viruses
 making backups of all software on a re.g.ular basis to avoid data loss And
create a recovery disk for the operating system
 Update the Anti-Virus Software on a Re.g.ular Basis -Keep your anti-virus
software up to date
 Do this at least weekly and more often if there are news reports of a new virus
threat
 Beware of E-Mail Attachments from Unknown Sources Do not open them
 Avoid booting computers from infected storage medium
 Avoid downloading programs from unknown/unlicensed sources
Common computer Network problems and troubleshooting
 IP address conflicts. Two computers are assigned the same IP address
erroneously
Solution: Change the IP address for one of the computers
 Absence of connectivity
Solution: checking the physical connections and connection devices And the
distance between devices in case of wireless network
Check the router or hub to see if some machine is disconnected, or if it a
case of is a faulty cable
In this case: a good connection is shown by a green light
o
o
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Ensure that TCP/IP is configured
Ensure all the computers on the network are within the same subnet
with individual IP addresses
Check if the file and printer sharing option is installed and functioning,
and also define network shares on each computer
 Slow connectivity
This can be due to:
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i) Collisions, which the network is incapable of handling
ii) Heavy file transfers bring down the speed tremendously
iii) The network card may also be overloaded
Solution: i) zip bulky files while transferring, which lowers the pressure on
the network
 Firewall settings can interfere with file sharing on connected computers. It is
true that disabling security features can make your system vulnerable to
attacks, but lowering security levels should not cause too much trouble
Solution: Rigid Firewall settings need to be adjusted to allow networked
computers to share data. You may consider disabling the security settings
temporarily, after having thoroughly considered all security related threats
INTERNET
Internet is an International/global interconnection of computer networks
It is described as a network of networks; it is a global network where all LANs (both
big and small) worldwide are connected together in many different ways to form the
Internet
History of the Internet
The Internet was originally developed in the late 1960’s by the US government
department of defense to improve secure communication between its military
computers and enhance the sharing of information and collaboration on military
and scientific projects in four locations; universities of California, Los Angeles,
Santa Barbara, Utah and Stanford research institute
This internet was known as ARPANET (Advanced Research Projects agency
Network)
Characteristics of the Internet
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It is made up of numerous networks worldwide
There is No organization that has a direct control over the Internet
It is dynamic; ever changing
It offers very many services
The Internet size and technology grow at a very fast rate
It is not owned by any single organization(has no central control)
Requirements/infrastructure for Internet connection
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Host computer
Communication hardware such as Modem and router
Communication Software such as a Web browser and internet protocols
Communication media such as VSAT, wireless antenna or telephone line
Internet Service provider (ISP)
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The Internet Service providers (ISP)
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ISP is a company which provides services for accessing and using the Internet at a
fee
Task:
Give some examples of ISPs in Uganda
There are many ISPs on the market in Uganda to choose from such as AFSAT, UTL,
MTN, etc.
Which services do ISPs offer?
The services offered by the ISP
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Offer connection to the Internet
They do system analysis and consultancy
Network servicing and maintenance
Provide network security
Domain name registration
Website hosting
Hiring storage space to small organizations
Electronic mail services
The Factors to consider when choosing an ISP
 Setup costs
 Experience for both ISP and client
 Auxiliary/additional services offered by the ISP e.g. E –Mail/telephone SMS
facility
 Availability of online help
 Compatibility of ISP software with yours e.g. windows Vs Linux Vs Wang
 Efficiency/Effectiveness of ISP devices e.g. speeds of ISP modem, Bandwidth
etc cabling architecture, Bit–Bus architecture for devices, etc
Available technology For example, In case you intend to hire a dial-up service,
you need to consider the availability of a local phone number or toll-free
number for access, This would help to reduce cost of acquiring totally new
technology or equipment the Technology offered by the ISP Some technologies
are older and less efficient than others The ISP should be able to offer the latest
and most efficient technology
 Technical support. What kinds of support services can the ISP provide?
Are there any additional charges for support?
 The terms of service. Whether they meet your expectations or not
 Other services offered by the ISP that you can have on top of internet
connection. E.g. web hosting and domain services
 The fee charged for the services
 The size of the ISP’s Client base ISP capacity is usually limited, the bigger
the client base the less reliable is the ISP
 Coverage. Does the ISP coverage reach your location or not?
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Internet connection technologies
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Dial-up (DUN)
This is a connection method where the client must request for a connection to the
ISP server each time he wishes to access the Internet This method requires the use
of a
MODEM and a telephone line and the fee depends on the amount of time spend online
Leased line
This is where there is a permanent connection between the user and the ISP at a
fixed fee
Bandwidth
Bandwidth is the amount of Data (bits) that can be transmitted along a
communication channel in a given time (per second) which is measured in bits per
second or bps e.g. 32 bps The larger the range of frequencies the greater the
amount of data that can be transmitted
Bit rate
Bit rate is the speed at which a particular transmission is taking place It is
measured in bits per second (bit/s or bps) and represents the actual speed of
transfer of data
Determinants of internet access speed
 The amount of bandwidth allocated by ones ISP
 Connection technology used; telephone lines are much slower than newer
technology such as ISDN and ADSL
 The volume of traffic the more the number of people logged on the internet
the slower the internet speed
 Adapter or modem speed used
 The processing speed and amount of RAM of the host computer
 Type of data/files being downloaded or uploaded
Internet services
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E-commerce
Provision of information e.g., on weather, and finance
E-banking
Research
On-line training
Downloading and uploading files
Sending or receiving messages
Real-time communication e.g. video conferencing and chat
On-line news
On-line booking/reservation
Virtual classes
Entertainment services such as online games
Advantages/benefits/positive implications of the Internet to society
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 The internet eases sharing and transfer of large amount of data using
different file transfer services
 Encourages collaborative work
 Easy access to databases on remote computers
 The internet promotes internet-based education via virtual classes and elearning
 Different skills such as typing, use of web browsers, problem solving, and email are developed through the use of the Internet
 Shopping for item such as books is made easy and less expensive
 Instant or timely communication is done over the internet using different
systems such as the E-mail system
 Companies are able to promote their businesses over the internet
 Social media such as face book is popularized over the Internet
 Eases publication of information to a very large audience at minimal cost
 The Internet is a rich source of information for researchers and students and
any one on all kinds of topics and subjects
 The internet provides a number of entertainment options
 It promotes medical care through online health care and medication
 It promotes and eases banking and finance through online banking
Advantages of the internet in schools
 A lot of information is obtained which is not available in a single textbook
 Updated or current information is obtained since internet is dynamic
 Learning is fun and easy as internet is exciting due to the multimedia
content used
 It offers different sources of information hence a variety of opinions on a
topic
 It is a quick way of getting information where internet connection is good
Disadvantages of the Internet
 No Information control over the Internet such that all sorts of bad
information is accessed
 There is no privacy of information and information piracy is common
 Indecent material is published on the Internet
 It’s not readily available to most people
 High costs due to costs on connectivity
 Time is lost where Internet speed is low due to poor links, hardware and
congestion.
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Time wasting occurs when workers easily stray into non-essential materials
Computer viruses are easily spread over the Internet
High possibility of hacking
Cybercrime is easily committed over the internet Examples of such crimes
include fraud, phishing, impersonation, child pornography and cyber
bullying
Possible solutions to Internet issues
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Use of firewalls against ille.g.al access to networks
Use of updated antivirus software against viruses
Use of anti-spyware against hackers
Carefully choosing an ISP who will provide the best service within your
means
Installing filters against pornographic and other undesirable content
Use of encryption software to protect sensitive information and prevent fraud
Use of complicated passwords to restrict access to
Use of digital certificates This is a means of authenticating that an
organization is genuine and that any transaction undertaken with it will be
honored The certificate contains the name of the organization and a serial
number registered with a Certification authority who issues the certificate
Use of the Internet as a learning tool
 Used to search for information using search engines and directories
 E-mail system is used in collaborative learning
 Enables distance learning for those who are unable to attend collage/school
physically
 Discussions over educational chat rooms
 Enables downloading of relevant documents
 Using computer assisted assessments (CAA) for online exams
 Use of electronic libraries and textbooks
 Development of skills of research and communication by the students
 Assignment are received, done and sent across the network by the students
 Video conferencing is used to share views and ideas among students and
teachers
The World Wide Web (WWW)
This is the global collection of web sites and web pages which are hyperlinked
containing text, and multimedia content There are virtually no regulations
regarding the content of the WWW, so any one with appropriate software and
hardware can create a web site on any topic
Consequently there are millions and millions of pages of information covering every
conceivable topic
Multimedia
The integration of text, graphics, animations, audio and video, normally using a
computer application
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A website (or Web site) is a collection of related hyperlinked web pages hosted on a
particular web Server on the World Wide Web
Web pages are HTML documents
Hyperlinks are built-in links to other related documents, allowing users to quickly
navigate from one document to another when clicked
Each Web site may contain one or more web pages Each site has a home page, this
is the first
Document/page users see when they enter a site
The site might also contain additional documents and files which must be
hyperlinked
Each site is owned and managed by an individual, company or organization
A Web page is a document, typically written in HTML, which is accessible via HTTP,
a protocol that transfers information from the Web server to display in the user's
Web browser
A Webpage contains hyperlinks to other pages or sites
A hyperlink, is a reference or navigation element in a document to another section
of the same document or to another document that may be on a different website
Web pages are written in HTML (Hypertext Markup Language)
The web server
This is a dedicated computer which accepts file uploads, downloads, distribution
and storage of these files over the Internet upon the requests of the World Wide
Web users
Characteristics of the web server
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Very high storage plus memory capabilities
Very strong multiprocessor e.g. Motorola G4, G3
High capacity RAM –DIMMs
Improved Network through-put (Enhanced NIC)
Expansion capabilities for upgrades to be effected
Website publishing
Web publishing is the process involved in making information available on the
World-Wide Web
Web publishing process
This involves;
 Web designing
 Web site hosting
 Web site content management
Web designing
This is the initial process of web publishing through which a web page is created
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It’s about organizing web content so that it can be easily found and easily read and
is attractive to visitors
Web authoring
Web authoring refers to designing and creation of a Web site, ranging from writing
the site's underlying code to writing the text to managing the site's upkeep This can
be done directly by writing the html code, or using html tools that operate in the
background to create the code while the author is using a WYSIWYG interface
Webmasters
A webmaster is a person who creates and manages the information content (words
and pictures) and organization of a website, or manages the computer server and
technical programming aspects of a website, or does both
Website hosting
Website hosting is a service that allows individuals and organizations to have their
own websites accommodated on a particular web server from which they are
accessed by others on the World Wide Web Website hosts are companies that
provide space (web hosting) on a server they own for use by their clients Some web
hosts provide free services while others charge a fee
Uses of web sites
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To Share of knowledge or information
To Present information of interest
To Enhance communication and collaborator
To provide Skills building e.g. writing, editing etcdesigning
For Trade purposes
It give the owner Pride/improved image
For storage of Data and information
To enable Research
For Entertainment and leisure in cases of E-Zoos plus E-museums, etc
Communication software requirements for WWW
 Web browser
 TCP/IP protocol
 HTTP
Hypertext Transfer Protocol (HTTP)
HTTP is the set of rules that govern how web pages and multimedia files are
transmitted over the Internet The content of the WWW contains text, sound, video
so HTTP ensures that they are all transmitted as a webpage in a common format
Examples of plug-ins include Shockwave and Quick time, Adobe acrobat reader,
flash player, Real time player and DirectX, must be installed and configured to run
on the computer
Web browsers/Web client
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A Web browser is communication software designed to allow the user to access and
view web pages on the Internet’s World Wide Web
The browser is designed to interpret hypertext Markup (HTML) language
HTML is a code in which web pages are written, therefore it requires a web browser
which is specialized software to able to retrieve and display text, and multi-media
in HTML .
Commonly used web browsers include; Internet Explorer, Opera, AOL Mozilla Fire
fox Google chrome, etc
Web browsers also use Plug-in applications to display other content, such as videos
and animations that the browser is unable to directly display;
A plug in is a small application that is installed to add special capability to a major
application such as a web browser
Modern Web browsers are also referred to as internet suites because of their ability
to display a variety of applications, multimedia, and files created with other
programming languages such as Java and ActiveX, scripting languages such as
JavaScript, and techniques such as AJAX, and the like which have other file
The Functions of a Web browser
 It is used to request for WebPages from a web server when the user types in
the uniform resource locator
 The web browser accesses information from the web server using the HTTP
protocol over a network to communicate with the web server
 It displays web pages on the screen The coding in the HTML files tells the
browser how to display the text, graphics, links, and multimedia files
 It is used for streaming video content over the internet
 Displays multimedia content
Features of a web browser (Web browser Interface)
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A menu bar that has items like file, edit, View, History, bookmarks or
favorites, tools, help and others depending on the browser type and version
A standard tool bar
An address bar to type in the desired Uniform Resource Locator (URL)
Navigation buttons to move forwards or backwards between pages and a
home button to go to a start-up page
A print button. This enables you to print a webpage or a section of it
A favourites section where you can bookmark (store) the URLs that you
wish to revisit
A history folder containing a list of previously visited sites
A built in search engine
A link to e-mail
A link to one or more search engines
Using a browser, you can do some or all of the following;
 View hundreds of millions of web pages
 Use mail clients to Send and receive e-mail
 Download games, music and computer software
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Chat
Shop on line
See and hear recorded broadcasts
Participate in virtual conferences
View channels, a channel is a website that automatically transmits
information to your computer at the time you specify
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Common web browser error messages (Study)
You may request the browser to fetch and display a web page, but instead of doing
that, it displays an error message or HTTP status code. Some of the browser error
messages are;
 Request Timeout (error 408)
The server was unable to process the browser request within the allotted
timeframe. This may necessitate refreshing the page
 File Not Found (error 400)
The browser may have failed to properly load the page file, or the page does not
exist anymore, or the server containing the page is currently down
 Internal Error (error 500)
This error comes about when the web form malfunctions
Unable to Connect to Remote Host This implies that the web browser is unable to
connect to a remote host on which the page is hosted
This may mean that the server is down, or there is no Internet connection, or the
web address was misspelt firstly,
 401 Unauthorized or 403 Forbidden
In case the browser displays either of these error messages, it implies that you are
attempting to access a website that allows only subscribed members who must use
usernames and passwords, and it site has blocked you from accessing it
Domain Name
A domain name is the representation an IP address of a computer on the network It
identifies the name of the organization or group that owns the site and type of web
site
An example; www.bbc.co.uk
The domain is separated into parts just like the IP address
A user normally finds it easier to use a domain name instead of an IP address to
access the a web page/web site
Task:
Write at least five domain names you know
Parts of the domain name
The hierarchy of domains descends from the right to the left label in the domain
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Each label specifies a sub domain of the domain to the right
For example, given the domain name .bbc.co.uk
bbc is the sub domain of co.uk, while co is the sub domain of uk
Top-level domain (TLD), is the last part of an Internet domain name, that is, the
group of letters that follow the final/last dot of a domain name
Examples of top level domains:
org, gov, com, net
Commonly used Top level domain names
.com indicates that the organization is a commercial one i.e. business
.gov indicates that it is for a government department
.ac is for an academic organization
.org is for a noncommercial or non-business organization
.sc is for a school organization
.net is for a company that provides internet services
Each country has been assigned a two letter code
Such as;
.au for Australia
.de for German(Deutschland)
.it for Italy
.es for Spain (espania)
.ug for Uganda
Second Level Domain (SLD)
The second-level domain is the label directly to the left of the top level domain
e.g. www.cnn.com
cnn is the second level domain
Third Level Domain (TLD)
This is the part of the domain name that is immediately to the left of the second
level
Domain For example;www.bbc.co.uk
bbc is the third level domain
Uniform Resource Locator (URL)
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A URL is the full address used to find particular files or web pages on the World
Wide Web For example
http://www.awebsite.co.uk/index.html
http://www.nypl.org/sitemap/index.html
Parts of a URL
i. The protocol being used, which could be http or ftp
ii. The domain name which is the location that contains the file of web page
iii. The path to a web page which may contain a folder name and document file
name both of these separated by forward slashes
iv. The query string, or parameters These are optional but show information
about the page/file
URLs don’t contain capital letters or spaces, but contains dots and forward slashes
The Forward slashes specify the path to the location of the file needed
Types of web sites
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Personal websites
Affiliate websites
Search websites
Portals
Blogs
Wikis
Commercial
Company websites
Etc
Search engines
A search engine is a software system that is designed to search for web pages on
the WWW
Using a search query provided by the user
A search query is a request for information in form of a word or phrase or sentence
For example, you might specify that you want to search for information about
"Polar Bears", in which case the search engine would return all the URL's where the
search query words appear
The search engine ranks the search results based on a computer algorithm
(specification) not by subject category
It ranks first those URLs that register most occurrence of the key word(s) in the
search query
Usually more accurate pages are listed before those that include unreliable and
erroneous material
How to evaluate search results
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Not all that is published over the internet is good or accurate So the need to
evaluate what one finds The following are the guidelines;
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The author’s authority on the subject
Accuracy of information
Objectivity or intention of the author
How current is the information presented
The extent of coverage of the topic
Who the publisher is
The publisher’s reputation
Do the authors properly list their sources, references or citations with dates,
page numbers or web addresses, etc?
The search content of result pages is not evaluated
The objective of the site
Whether the information up to date or valid
When was the site was last updated
The relevance of the information to the research topic
the intended audience of the site
Is the material presented at an appropriate level?
How to effectively use a search engine
Link more than one keyword and linking them with AND, OR or NOT (Boolean’s
logic) in case of complex searches
Use specific queries Avoid redundant words e.g. if one wants to search about
Ugandan wildlife, the search query should be “Ugandan wildlife” not just “wildlife”
Using the symbols + or -the plus symbol lets you find pages that have all the words
in the query e.g.to get pages that refer to both john and Tom on the same page, use
+john+Tom
Example 2 +computer +studies+schools gives pages on computer studies in
schools
Use the –symbol to eliminate characters from the search
Use parentheses to sequence operators and group words Example; always group
words joined by OR with parentheses
Narrow the search query to avoid irrelevant results
Subject Directories
A subject directory is a software that contains a lists of links to different subjects or
topics already sorted by subject or topic category
Examples include; dir.yahoo.com, info.mineucr.edu, academic.infonet, about.com’
lii.org, howstuffworks.com, etc
Characteristics of Subject Directories
 They are built by human selection not based on automated systems
 The sites/pages are organized into subject categories
 The sites/pages are evaluated Only most relevant web pages are availed
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Web Portals
A portal is a web site which brings information together from various sources in a
uniform way. Usually, each information source gets its dedicated area on the page
for displaying information, it also offers a variety of services like search, e-mail,
online shopping and others Examples Yahoo, MSN, AOL etc
File transfer
Internet enables transfer of files over the internet by use of FTP FTP sites contain
books, articles, software games images sound multimedia etc all of which can be
transferred with or without the use of special download software
Usenet
This is a service on the Internet on which one can post and read electronic
messages The messages are stored on usenet servers and organized by topic into
newsgroups
Electronic commerce sites
E-commerce is business that is done over a communication network where the
buying and selling of products or services is conducted over electronic systems
such as the Internet and other computer networks, involving the exchange of data
to facilitate the financing and payment of business transactions
An electronic commerce website is one that is managed by the business to display
what the business deals in to give an opportunity to potential buyers to make their
choices and makes orders
Example of e-commerce site addresses include;
http://www.shopsonthenet.co.uk
http://www.ukshops.co.uk/enters.html
http://bookshop.co.uk
http://www.amazon.com
Merits of e-commerce
 Reduced expenses since there is no need for retail premises and fewer
employees
 Customers/clients for the business are attracted through the Internet
 Customers have access to information all the time increasing the chances of
making sales
 Safety is increased since payment is done through electronic fund transfer
(EFT)
 Market research is easily done over the internet, because information about
potential buyers
 Ecommerce reduces travel time and costs for the customers since they do not
need to visit the shops
 Prices are reduced as the business can offer lower prices due to lower
overheads
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 The customer is able to sample the products on-line, for example view movie
clips or listen to music before buying
Disadvantages of on-line businesses
 Businesses incur costs of Internet operation
 Sales may be reduced if customers are unable to try products before they can
buy
 The e-commerce may be hacked leading to loss of money fraudulently
 Conmen can easily trick unsuspecting customers leading to loss of money
when they get access to customer’s credit card numbers
WIKIS
A Wiki is a collaborative work website that allows individuals to add, modify, or
delete content in collaboration with others
Blogs (web log)
A blog is a web site maintained by an individual who makes regular posts such as
descriptions of events, or other material such as graphics or video on an ongoing
basis, allowing visitors to the site to make their comments or link to it or email you
or not
Podcasts (Net casts)
Podcasts are digital media files consisting of an episodic series of audio, video, PDF,
or e-Pub files subscribed to and downloaded or streamed online onto a computer or
mobile device
Podcasting means making digital audio or video files available on the internet in
such a way that others can set their computers to automatically download new
episodes in a series as you post them
Webcasts
A Webcast is the delivery of live or delayed sound or video broadcasts over the
internet using streaming media technology The sound or video is captured by the
conventional video or audio systems, then digitized and streamed E.g. News
broadcast, Radio and TV programs
Webinars (Web conferencing/online workshops)
A Webinars is short for web based seminar It refers to conducting a seminar or
lecture via the internet using graphics, text and live sound, unlike web casting, the
audience is able to interact with the presenter such as asking questions by sending
an instant message
A webinar allows real-time point-to-point communications as well as multicast
communications from one sender to many receivers
It offers data streams of text-based messages, voice and video chat to be shared
simultaneously, across geographically dispersed locations
Applications for web conferencing include meetings, training events, lectures, or
short presentations from any computer
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Cloud computing
This is Internet-based computing that relies on sharing computing resources over
the Internet where remote servers are networked to allow centralized data storage
rather than having local servers or personal devices to handle applications
The word cloud is used in reference to internet
Cloud computing allocate individual users a specific storage capacity on the virtual
server
It provides all needed Application programs interfaces for users that enable users
to migrate their work to the virtual server
Intranets
An Intranet is a private internal network of an organization using internet protocols
and accessible using a web browser.
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It contains information specific to that organization and only accessible to
authorized users within the organization or members of the organization
It is therefore closed to outsiders
It is hosted on the server of the organization
Intranet is used to avail information to members of an organization
Intranet may have an e-mail system with a mail server to route the mail to the
members’ mail boxes
It only contains relevant information to the users so they don’t suffer with or
waste time on irrelevant information
Access to information is faster than an internet connection
Information is much more secure than on the Internet because outsiders don’t
have access to it
However the scale of information is limited as compared to the internet
It is costly to build and maintain and keep up-to-date
Extranets
An extranet is a private network that uses internet protocols to share data of a
particular organization with selected outside users such as the clients of the
company or subsidiaries of a company
Differences between an Intranet and Internet
 Intranet is private while Internet is public
 Intranet has geographical boundaries while internet has no boundaries
 Intranet only shares company information while Internet has all sorts of
information
 Intranet is a single source information while Internet is a multisource
information
 Intranet is controlled by an organization while there is no control over the
Internet
Terminal emulation
This is an Internet resource/service that allows remote access to computers
connected on the internet using a virtual terminal connection.
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This means that using one computer, one can access another computer on the LAN
or Internet and all the information and resources on that computer as if one was
sitting at that other computer
E-mail
E-mail or electronic mail is primarily text-based electronic message that is sent
from one computer or other ICT devices to others In order to send or receive an email, one must have a computer connected to the Internet, E-mail software, and an
e-mail account
When mail is received on a computer system, it is usually stored in an electronic
mailbox for the recipient to read later
Messages can be replied to or forwarded with speed and ease
E-mail software (e-mail client)
E-mail software is an application software which allows individuals to create an email accounts and be able create, send and receive, store, and forward e-mail using
SMTP and POP
Examples Microsoft outlook express, Yahoo, Eudora light, Gmail, Opera mail, etc
Mail servers
A mail server is a dedicated computer on the Internet that receives incoming
messages, stores them and delivers outgoing messages
It allocates a certain amount of storage space referred to as mail box to hold mail to
registered users. The user can receive mail by supplying the username and
password through the mail client
The Features of an E-mail software
Email address All email software require the user to have an email address,
username and Password which are unique to ensure security of the users emails
An email address has two parts separated with the @ sign for example
yourname@yahoo.co.uk
The first part of the of the address is the e-mail name made up of the username of
the email account while the second/last part indicates domain name of the
company that provides the email facility.
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From: Indicates the address of the one sending the message
To: This is where the address of the mail recipient is typed
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Cc: (carbon copy). This is where other addresses to receive copies of the
same message are indicated in addition to the main recipient
Bcc: (blind carbon copy) this enables copies of the e-mail message to be sent
to a third party without acknowledging/showing any other recipients (if any)
Subject: refers to the theme/topic of the email It is where the theme of the
message is indicated
Compose: This is where one types the actual message
Attachments: an attachment is the added file or files that are sent with the
message Such files are usually too large to be sent as a simple message
Such files are known as MIME (Multimedia Internet Mail Extension)
attachments
One advantage of this is that large files are conveniently sent
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Address book: is an area that stores email addresses for future use or
mailing lists
Inbox: this where all incoming messages are stored and can be viewed, it
shows the name of the sender of the message, the date it was sent and the
subject of the message
Outbox/sent messages: Stores copies of any messages that have been sent
at stated dates. This is useful for future reference
Handling one’s mails
 Creating document folders in which to store mails
 Checking and reading mail in the inbox
 Transfer messages from the inbox to a specific folder or storage file either by
the drag and drop facility or right click and move
 Deleting a message. This can be done by right click then delete or delete on
the tool bar
 Sorting messages
 Drafting or composing a new message
 Inserting an attachment/file to your message To insert and attachment,
click on insert file attachment or attach file, then browse the hard disk or
any other disks to find the file you want Repeat the operation as many times
as you need
 Adding new contacts in your address book
 Filtering messages received to avoid spam in your mail box
 Sending messages
Sending an Email to Multiple
Use Cc and Bcc to send an email to more than one person easily and fast
"Cc" is short for "carbon copy” Enables one to send the same e-mail to two (or
more) people without the task of having to write it more than once
The message you compose is sent to the person in the To: field, but a copy of
exactly the same message is also sent to all the addresses listed in the Cc: field
To enter more than one address in the Cc: field, separate them with commas
The Shortcomings of Cc:
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All recipient of the message get to know the email addresses of all the
persons that received your message. This is usually not desirable Nobody
likes their email address exposed in public
Full Cc: fields also don't look all that good
They can become quite long and grow big on the screen There will be lots of
email addresses and little message text
BCC
Bcc is stands for "blind carbon copy"
The Bcc: field helps you deal with the problems created by Cc: a copy of the
message goes to every single email address appearing in the Bcc: field The
difference is that neither the Bcc: field itself nor the email addresses in it appear in
any of the copies
The only recipient address that will be visible to all recipients is the one in the To:
field
What to consider when using email
 Email can be junk mail So avoid unnecessary proliferation of messages
 Email takes up computer space, so delete messages you no longer need
 The integrity of an email message cannot be guaranteed If a received
message seems out of
 character for the sender, double-check before taking it seriously
 Take care opening attachments Treat any attachment you receive with
suspicion unless you expect
Benefits/advantages of using email
 It’s quick; e mail takes seconds to send compared to snail mail
 It’s cheap Compared to posting or faxing messages
 The same message can easily be sent to many recipients at once by use of a
mailing list
 Messages can be replied to or forwarded with speed and ease because the
software automatically inputs the address of the sender
 Other files can be sent as attachments which has increased the popularity of
email in business
 it is convenient because a message can be sent anywhere in the world without
having to leave
 one’s desk
 E-mail can be used by businessmen to send advertisements to potential
customers
 It is possible to send multimedia content as e-mail
 The sender is informed in case the email is not send so that is able to find
other ways of delivering the message
 A copy of the message is kept
Disadvantages of e-mail
 The sender and receiver both need internet access and e-mail accounts-most
people in Uganda do not have access to e-mail
 The hardware needed is expensive
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 Email will not be delivered if there is a small error in the address
 Some people are not keen on checking their mail boxes So an urgent message
may not be read in time
 There is a large volume of unsolicited e-mail known as ‘spam’ that tends to fill
up mailboxes
 E-mail tends to take peoples valuable time at the expense of work or study
 Parcels cannot be delivered via e-mail which limits its usability
 Most viruses are spread via email
 The privacy of an email message cannot be guaranteed So confidential
messages ought not sent via e-mail
Mailing lists
This is an e-mailing facility which distributes the same messages to the electronic
mailboxes of all subscribers to the mailing list The automated list manager
assembles all the messages and sends them to the subscribers which enables email
discussion among the subscribers of a particular mailing list One can subscribe to
or unsubscribe from a mailing list
An example of a mailing list are list servers
To find mailing lists, use your web browser to visit;
http://www.liszt.com
http://www.paml.net
Internet Relay Chat (IRC)
IRC is a text based communication system that allows the user to “enter” virtual
chat rooms in which there many participants at the same time. Within these rooms
one sends and receives instant messages to and from anyone else in the same chat
room
Instant Messaging (IM service)
This is a one-to-one chat service that requires an instant messaging software
(messenger) which must be installed on the computer that allows the user to build
a list of internet-connected friends from which one selects who to chat with at a
particular time in case they are on-line
Video conferencing
Videoconferencing is the conduct of a session/discussion using a set of
telecommunication technologies which allow two or more locations to communicate
by simultaneous two-way real time video and audio transmissions
Videoconferencing is mostly used in business, education, medicine and media
It reduces the need to travel to bring people together
Netiquette
This is the etiquette guidelines that govern behavior when communicating over the
Internet i.e.The do’s and don'ts of online communication
The Netiquette rules
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Identify your self
Include a subject line
Avoid sarcasm so that you are not misinterpreted
Respect other user’s privacy
Acknowledge and return messages promptly
Copy with caution
No spam/junk mail
Be concise
Use appropriate language
Avoid flaming (online screaming)
Only use common acronym E.g. LOL for laugh
Use words in brackets, such as (grin) to express your mind
Use asterisks surrounding words to indicate italics used for emphasis (*at
last*)
Web designing
This is the initial process of web publishing through which a web page is created
It’s about organizing web content so that it can be easily found and easily read and
is attractive to visitors
Web authoring
Web authoring refers to designing and creation of a Web site, ranging from writing
the site's underlying code to writing the text to managing the site's upkeep This can
be done directly by writing the html code, or using html tools that operate in the
background to create the code while the author is using a WYSIWYG interface
Web authoring software
A category of software that is used to design web pages, it may not require one to
have any knowledge of HTML coding because it offers Web page design wizards and
different web page design templates for the user to pick from and simply insert
content The software will generate the required HTML coding for the layout of the
Web pages in the background based on what the user designs Examples of
commonly used authoring software include Dreamweaver, and Microsoft desktop
publisher
Content management system
A content management system (CMS) is a system that provides a WYSIWYG
interface to manage the content of a website Which involves adding new content,
editing, or modifying existing content and removal of unwanted or expired content
It allows the content manager or author, who may not know Hypertext Markup
Language (HTML), to manage the creation, modification or removal of content from
a website without needing the expertise of a webmaster Examples of CMS include
Joomla, Drupal and Wordpress
HTML codes, also referred to as HTML tags, are enclosed by the lesser than (<) and
greater than (>) brackets and may be written in capital or lower case letters
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The opening bracket is followed by an element, which is a browser command, and
ends with the closing bracket<font size=2>
An element may also be followed by attributes, which are words describing the
properties of the element, and further instruct the browser<font size=2>
Attributes are only contained in the opening HTML tags to the right of the element
and are separated by a space and followed by an equal (=) sign
The value follows the equal sign and is enclosed in quotes<font size=2>
Examples of Basic HTML tags
For each attribute, there is an opening and a closing tag;
Example of basic document structure:
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<HTML>
<HEAD>
<TITLE>your document title goes here</TITLE>
</HEAD>
<BODY>
Your document text goes here
</BODY>
</HTML>
The very first tag in your document: <HTML>and the very last: </HTML>
HEAD
The second tag in your document Enclosed within the be.g.inning tag: <HEAD> and
the ending tag: </HEAD> is information about the document that will not display
in the body of the document
TITLE
The document title, which is enclosed with a be.g.in title tag: <TITLE> and an end
title tag: </TITLE>, all of which is enclosed with the HEAD tags above
The title does not display as part of the document itself, but appears in the browser
window title. It is also what is used to name your document in a bookmark list
BODY
The complete text of your document is wrapped by a be.g.in body tag: <BODY> and
an end body tag:
</BODY>
HTML EDITORS
There are many HTML Editors for purchase or download Recent versions of Word
and
WordPerfect have HTML Editors, or you can choose to use a dedicated HTML editor
such as FrontPage or Dreamweaver
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When using a word processing application to create an HTML file, open the word
processed document, then select the menu option FILE :
Save As HTML or choose to use the Ms Word webpage wizard
What to consider when designing a web page
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The target or primary audience of the web site
The impression you wish the site to create to your visitors
The purpose of the website. Whether personal, commercial or educational This
helps to determine the design for it
The browser types or version likely to be used by your primary audience to
determine the nature of materials to use in the website
How to organize the site links and web pages to enable easy navigation
through the site by visitors
To obtain the relevant content to include in your page
Obtaining permission to use other people’s copyrighted content or to link to
other people’s sites this protects you from any possible le.g.al problems
concerning copyright violation
Characteristics of a good web site
 It should be easy to navigate with well arranged, easy to see navigation
buttons
 Simple and clear layout of sections and content which makes it user friendly ie
find content easily
 It must be pleasing to the eye to encourage visitors to the site
 It should load quickly to avoid disappointing potential visitors to the site
 It should have readable font web safe eye pleasing colours so that visitors can
read the content easily
 It should be interactive with contact information, possibility of e-mail, online
communication forum and chats Message boards etc
 Should have active links which enable visitors to access other references
 Should be frequently updated and must have a dated of last update
 The web pages must have web page titles and brief summaries about the
page or site
Uses/functions of a Web site
 It Enables Publicity or exposure to the public of a business or school
Businesses consider their website to be their most important face to the public
 It is a Communication tool for information exchange between an organization
and the public or a group of people
 Provides a convenient and cheap base of operation for individuals and
businesses
 Useful in Marketing of products explaining the products and services offered,
providing background and general contact information and online transactions
 They are a source of income to advertisers and web site developers Space can
also be hired for advertisements
Relevance of websites to schools in Uganda
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 It is used for communication purposes. The school can reach out to a wider
audience worldwide, for example, in school recruitment
 Used for mobilization of resources. The website can be used for resource
mobilization as it can reach out to a wide supporting audience
 For advertising purposes. The website can provide general information about
the school
 The website can provide a forum for discussion of issues concerning the school
using blogs
 It can be used for teaching and learning in the following ways:
 The website can provide subject content notes to students
 The website can present an opportunity for developing web designing
technology skills for students directly involved
 The school community can collaborate with other students worldwide for
project based learning
 The website can provide a forum for students and teachers to collaborate with
others elsewhere
 The site can provide a forum for parents and alumni feedback
 It can work as a depository (store) where students’ achievement data is
posted for easy access by the stakeholders
 It can help teachers to collaborate with other teachers worldwide
 The site can be used to publish students and teachers work
Web site hosting
Web hosting is a service of storing a website on a particular server that is
connected to the WWW such that the site is accessible on the World Wide Web
Web hosting is necessary to enable individual access the website at any time
Web hosts are companies that provide space (web hosting) on a server they own for
use by their clients
Some webhosts provide free services while others charge a fee Free web hosting is
advertisement-supported web hosting, and is often limited when compared to paid
hosting
A web site can also be hosted on a home or private server in a home or local area
network
HTML EDITORS
An HTML editor is a software application for creating web pages Although the
HTML markup
of a web page can be written with any text editor such as word pad, specialized
HTML editors can offer convenience and added functionality For example, many
HTML editors work not only with HTML, but also with related technologies such as
CSS, XML and JavaScript or ECMA Script In some cases they also manage
communication with remote web servers via FTP and WebDAV, and version
management systems such as CVS or Subversion
Project work on web designing
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You are required to design five web pages (use any web publishing software) for your
school taking into considerations the properties of a good web site
Page one is the Home page which must include
(i) A welcome note and information on the schools location and motto
(ii) The schools email address
(iii) The web links to the other pages
(iv) The navigation bars
(v) Company logo
Page two should show bullet list of departments available in the school Add a link to
the school website for further information
Page three should contain other facilities offered in the school e.g.swimming, school
bus, internet services
Page four should have a brief information on your dormitory/house and a simple
definitions list stating the chorus of your house
A table indicating 5 names of your dormmates showing their Biodata(age, sex, home
town/district
Insert a relevant form control
Page five should have photo gallery of at least five images
Network Security concerns
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Hacking/trespassing-secretly finding a way of looking or changing information
of someone else’s computer without their permission a hacker may break into
a system in order to explore it and expand their knowledge
Data loss through malice or human error
Information theft
Illegal access to the network ie computer intrusion where someone or program
gains unauthorized access to a computer system
Virus and worm attack
A worm is a code that uses computer networks and security weakness to
repeatedly copy itself into a computer memory until no more space is left
While a computer virus is a malicious and destructive program written to
activate itself (executable) the moment it is introduced to a computer system
and cause the system to malfunction.
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Phishing. This is an attempt to steal Passwords and other private account
information
Phishers can set up fake web sites that look like those of trusted companies
like Yahoo! to trick individuals into disclosing their user name and password
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Cracking. This is breaking into computer systems or networks by bypassing
passwords or licenses
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Hardware malfunction
Solutions to network security problems
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Install an up to date antivirus software
Separate the networks
Use network password
Putting in place a code of conduct.
This is an acceptable use policy which tells the users what is acceptable and
allowed on the company network.
This can include things like acceptable websites to visit as well as what times
are acceptable for browsing the Internet
Computer malware risks
Malware is software designed to infiltrate or damage a computer system without
the owner's informed consent It is a portmanteau/combination of the words
malicious and software Malware is a general term used by computer professionals
to mean a variety of forms of hostile, intrusive, or annoying software/code
Malware includes computer viruses, worms, Trojan horses, most root kits, spyware,
dishonest Adware, and other malicious and unwanted software
A computer virus is a computer program that can copy itself and infect a computer
without permission or knowledge of the user Viruses attach themselves to
executable files that may be part of legitimate programs If a user tries to start an
infected program, the virus' code is executed first
How computer viruses spread
In order to infect a computer, a virus has to have the chance to execute its code.
This occurs in any of the following ways;
(i) Booting a PC from an infected medium such as a floppy
(ii) Executing an infected program
(iii) Opening an infected file
A virus can only spread from one computer to another when its host is taken to the
uninfected computer, for instance by a user sending it over a network or the
Internet, or by carrying it on a removable medium such as a floppy disk, CD, or
USB drive
Viruses can spread to other computers over a network by infecting files on a
network file system or a file system that is accessed by other computers
Viruses often travel via e-mail attachments
E-mail messages by themselves do not carry viruses. Only exe, com or other types
of executable files can carry a virus
In summary, viruses are spread in the following ways:
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 Through infected diskettes from infected computer systems
 Through sales demonstration applications
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Through networks
Through software updates
Through free computer games on the net, etc
Through pirated software. These are software that have been copied without
the permission of the owner.
From software laboratories. Programs can be infected without the
manufacturer’s knowledge
Through the use of the network (internet)
An employee of an organization can also introduce such viruses knowingly.
Through executing an infected program
Through opening an infected file
Effects of computer viruses
 Some viruses are programmed to damage the computer by damaging
programs, deleting files, or Reformatting the hard disk.
 Others simply replicate themselves and perhaps make their presence known
by presenting text, video, or audio messages
 They take up computer memory used by legitimate programs
 They can result in system crashes and data loss
 They can prevent a computer from booting
Symptoms of a computer virus attack
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The computer runs slower than usual
The computer stops responding, or it locks up frequently
The computer restarts on its own
Applications on the computer do not work correctly
Disks or disk drives are inaccessible
You see unusual or strange error messages
There is a double extension on an attachment that you recently opened, such
as a jpg, vbs, gif, or exe extension
An antivirus program is disabled for no reason Additionally, the antivirus
program cannot be restarted
An antivirus program cannot be installed on the computer, or the antivirus
program will not run
New icons appear on the desktop that you did not put there, or the icons are
not associated with any recently installed programs
Strange sounds or music plays from the speakers unexpectedly
A program disappears from the computer even though you did not intentionally
uninstall it
It shuts down unexpectedly or crashes frequently
It experiences memory problems or runs out of disc space
Unusual files or directories appear on your system
Virus types
Viruses can be divided into two types, on the basis of their behavior when they are
executed;
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The Nonresident viruses which immediately search for other hosts that can be
infected, infect these targets, non-memory-resident viruses only are activated when
an infected application runs
The Resident viruses which do not search for hosts when they are started. Instead,
a resident virus loads itself into memory on execution
It stays in memory after it executes and after its host program is terminated
The Resident virus stays active in the background and infects new hosts when
those files are accessed by other programs or the operating system itself
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Boot Virus
This type of virus affects the boot sector of a floppy or hard disk This is a crucial
part of a disk, in which information on the disk itself is stored together with a
program that makes it possible to boot (start) the computer from the disk
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Macro Virus. Macro viruses infect files that are created using certain
applications or programs that contain macros
These mini-programs make it possible to automate series of operations so that
they are performed as a single action, thereby saving the user from having to
carry them out one by one
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FAT Virus
The file allocation table or FAT is the part of a disk used to connect information
and is a vital part of the normal functioning of the computer
This type of virus attack can be especially dangerous; by preventing access to
certain sections of the disk where important files are stored Damage caused can
result in information losses from individual files or even entire directories
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Logic Bombs
They are not considered viruses because they do not replicate They are not even
programs in their own right but rather camouflaged segments of other programs
Their objective is to destroy data on the computer once certain condition(s) is
met
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File Infectors
This type of virus infects programs or executable files (files with an EXE or COM
extension) When one of these programs is run, directly or indirectly, the virus is
activated, producing the damaging effects it is programmed to carry out.
The majority of existing viruses belong to this category, and can be classified
depending on the actions that they carry out
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Companion Viruses
Companion viruses can be considered file infector viruses like resident or direct
action types They are known as companion viruses because once they get into
the system they "accompany" the other files that already exist In other words, in
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order to carry out their infection routines, companion viruses can wait in
memory until a program is run (resident viruses) or act immediately by making
copies of themselves (direct action viruses)
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Directory Virus
Directory viruses change the paths that indicate the location of a file. By
executing a program (file with the extension EXE or COM) which has been
infected by a virus, you are unknowingly running the virus program, while the
original file and program have been previously moved by the virus
Once infected it becomes impossible to locate the original files
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Polymorphic Virus
Polymorphic viruses encrypt or encode themselves in a different way (using
different algorithms and encryption keys) every time they infect a system
This makes it impossible for anti-viruses to find them using string or signature
searches (because they are different in each encryption) and also enables them
to create a large number of copies of themselves
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Resident Viruses
This type of virus is a permanent which dwells in the RAM memory From
there it can overcome and interrupt all of the operations executed by the
system: corrupting files and programs that are opened, closed, copied,
renamed etc
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Direct Action Viruses
The main purpose of this virus is to replicate and take action when it is
executed When a specific condition is met, the virus will go into action and
infect files in the directory or folder that it is in and in directories that are
specified in the AUTOEXECBAT file PATH
This batch file is always located in the root directory of the hard disk and
carries out certain operations when the computer is booted
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Computer worms
A computer worm is a self-replicating computer program It uses a network to
send copies of itself to other nodes (computer terminals on the network) without
any user intervention Unlike a virus, it does not need to attach itself to an
existing program Worms always cause harm to the network by consuming
bandwidth and memory
A root kit is a program (or combination of several programs) designed to take
fundamental control (in Unix terms "root" access, in Windows terms
"Administrator" access) of a computer system, without authorization by the
system's owners and legitimate managers
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Trojan horses
A Trojan horse, or simply Trojan, is a piece of software which appears to
perform a certain legitimate action but in fact performs a malicious act
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Spyware
Spyware is computer software that is installed stealthily on a personal computer
to intercept or take partial control over the user's interaction with the computer,
without the user's informed consent.
Spyware programs can collect various types of a user’s personal information,
such as Internet surfing habit, sites that have been visited, but can also
interfere with user control of the computer in other ways, such as installing
additional software, redirecting Web browser activity, accessing websites blindly
that will cause more harmful
viruses, or diverting advertising revenue to a third party Spyware can even
change computer settings, resulting in slow connection speeds, different home
pages, and loss of Internet or other programs
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Adware
Adware or advertising-supported software is any software package which
automatically plays, displays, or downloads advertising material to a computer
after the software is installed on it or while the application is being used Some
types of adware are also spyware and can be classified as privacy-invasive
software
How to protect a computer system against viruses
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Buy software from legal vendors
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Avoid running unchecked or scanned files.
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Avoid running files with an attachment from an unknown source on the
network.
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Backup your files and folders regularly
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Use Netware with strong validation checks and in-built firewalls. e.g. Linux
(i.e. Hardware and software which can limit unauthorized data through
networks to reach your workstation)
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Disable auto micros functions for macro viruses
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Use antivirus programs. These are utility programs used to scan files and
programs in order to detect, destroy or
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