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Bassu Stationery and Computer Services
KKK – Tukuyu, Mbeya Tanzania

AN INTRODUCTION TO COMPUTER STUDIES

Prepared By:
Bassu, J
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1 Definition of computer
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(a) Classification according to size and processing power
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(c) Classifications according to functionality
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3 Historical development of computers
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2 Napier’s bones
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4 La Pascaline machine
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6 The Analytical engine
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1 Computer Laboratory
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1 Booting up a computer
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3 Mouse
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1 Input devices
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3 Output devices
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5 Basic Computer Setup
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2 Computer Software
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2 Application Software
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3 Relationship between Hardware and Software
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4 Criteria for selecting computer system
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2 Software considerations
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1 Operating System is a program with following features:
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3 Characteristics of Operating System
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2 Role, structure, resources and functions of an operating system
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2 Structure of an operating system
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4 Functions of an operating system
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3 Types of operating systems
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2 Classification according to tasks
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4 Classification according to user-interface
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1 Folders
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3 Files
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5 Managing files and folders using windows
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2 Creating folders
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4 Renaming files and folders
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7 Searching for files and folders
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6 Managing storage devices using Windows
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2 Scanning a drive for problems
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4 Scanning for malware
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6 Backing up data
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8 Partitioning a disk
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7 Installation and configuration of an operating system
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8 Troubleshooting and fixing problems
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2 Missing operating system
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4 Failure to load the GUI desktop
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6 Runtime problems
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1 Decimal Number System
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3 Octal Number System
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1 Decimal to Other Base System
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3 Other Base System to Non-Decimal System
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5 Shortcut method - Octal to Binary
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7 Shortcut method - Hexadecimal to Binary
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1 What is Information?
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3 Why do we need information?
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REFERENCES
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Introduction
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Computer laboratory and computers uses
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0 Introduction
The 20th century saw the birth of one of the most important tool widely in use today called a computer
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Data are the raw facts that may include alphabets, numbers and symbols which may not make much
meaning to the user
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Information is the processed data which makes meaning to user and which can form a basis for decision
making
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Before processing a specific job, the computer program corresponding to that job must be stored in
memory
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Why do we need computers?
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Storage: It can store vast amount of data in its main memory and auxiliary memory systems and
retrieve amount that the user wants in few seconds
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Versatility: They are flexible, multipurpose, multi-programmed machines hence capable of
performing activities ranging from simple to complex calculations
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Reliability (low failure rate): Failures are usually due to human error, one way or another
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A microcomputer can execute millions
instruction per second over and over again without mistakes
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This is possible via network connections
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 System unit: The part that houses the brain of the computer (the central processing unit),
motherboard, main memory and drives
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g
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Figure 1
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Fig
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1: Desktop Personal Computers

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However, the three most common methods of classification
are by:
 Physical size and processing power
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Supercomputers
Supercomputers (fig
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 The largest in physical size
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 Fastest processor speed
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Fig
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2: Supercomputers
2 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Supercomputers are mainly found in large research stations and are used to control complex operations
and perform complex calculations
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Mainframe computers
Mainframe computers (fig
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3) have the following characteristics:
 Smaller than supercomputers
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 Smaller memory capacity than supercomputer
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Fig
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3: A Mainframe computer
Mainframe computers are mostly used in large businesses as network servers
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However, their high cost and inability to upgrade has made them unpopular
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Minicomputers have the following characteristics:
 Smaller than mainframe computers
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 Low memory capacity than mainframe computer
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Fig
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4: A Minicomputer
Minicomputers are used as cheaper alternatives to mainframe
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Minicomputers are also used as autopilots in airplanes
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They are called microcomputers because their processor is very tiny
(size of a thumbnail)
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3 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Fig
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5: Microprocessor of a Microcomputer
Microcomputers are further classified into three categories namely:
(i) Desktop computers
Desktop computers are the most common because they are relatively cheaper than other
microcomputers
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(See Fig
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They are more expensive compared to
desktop PCs
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Fig
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6: Notebook PCs
(iii) Palmnote and pocket computers
Palmnote and pocket computers are the smallest PCs
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Examples of Palmnote or pocket PCs include personal digital assistants (PDAs) and modern smart
phones
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Special purpose computers
Special purpose computers are designed to perform a single task only or a few related tasks
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General purpose computers
General purpose computers can be programmed by the user to perform many tasks such as word
processing, desktop publishing, multimedia applications, accounting, etc
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The three types of
computers according to functionality are:
Analog computers
Analog computers process data that is continuous in nature
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Examples of analog data include speed, temperature, volume and weight
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This type of data is called digital data
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It is usually represented using two
states, on represented by 1 and off represented by 0
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A good example is
a modem
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3 Historical development of computers
Historical development of computers can be traced back to the time when humans were struggling to
invent tools that could simplify mathematical calculation
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1 Abacus
An abacus was a Chinese counting instrument which dates back to 3000 BC
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Fig
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8 shows an illustration of an abacus
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It is made up of marked strips of wood or bone, placed side by side to each other
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Fig
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9 Napier’s bones
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3 Slide rule
A slide rule, inverted by William Oughtred in 17th century, is a tool that can be used to perform
arithmetic operations
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Fig
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10 Slide Rule
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4 La Pascaline machine
La Pascaline counting machine (Fig
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11) was made by Blaise Pascal in the 17th century
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Fig
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11 Pascaline machine
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5 Weaving loom
In early 19thcentury, Joseph Jacquard built a weaving loom which could be programmed using punched
cards to pick out threads and weave them into patterns
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Fig
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12 shows an illustration of a weaving loom
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He called it the difference engine
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He called the
machine analytical engine
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The analytical engine
6 \\ An Introduction to Computer Studies, By Instructor Bassu\\

is recognized as the first real computer and Babbage as the father of computing
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Fig
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13 The design of the analytical engine
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7 Electronic computers
 Early computers have been around since the late 1800s
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 The forerunner of today’s computers appeared in the 1960s, and one of the first users was in the
business sector
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Lyons used a computer for the ordering of food for the many tearooms that
he operated
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 The development of the integrated circuit (IC) where millions of circuits could be held in a single
chip, the size of your finger nail, has finally led to computers becoming widespread in business and
in the homes (for study, for communication or for entertainment)
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The age of modern electronic computers can be traced back to 1951
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 Were very large in size
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 Were difficult to program, use and maintain
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Electronic numeric integrator and calculator (ENIAC) and Electronic discrete variable automatic
computer (EDVAC) are examples of first generation computers
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Fig
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5 The ENIAC computer
(b) Second generation computers (1958 – 1963)
Second generation computers used transistors
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Characteristics of the second generation computers:
 Emitted less heat compared to the first generation computers
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 Were difficult to program, use and maintain
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Examples of second generation computers include IBM 1401, 1BM 7070, and UNIVAC 1107
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Fig
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16 The UNIVAC 1107 computer
(c) Third generation computers (1964 – 1969)
Third generation computers used integrated circuits (ICs)
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Characteristics of third generation computers:
 Emitted less heat
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 Were easier to program, use and maintain
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(d) Fourth generation computers (1970 – 1990)
Fourth generation computers used very large scale integrated circuits (VLSI) or the microprocessor
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It is used on digital
devices such as watches, calculators and microcomputers
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 Are very smaller in size
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Examples of fourth generation computers include IBM 370, IBM 4300 and Burroughs 7700
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Characteristics of fifth generation computers:
 Use artificial intelligence
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 Superior hardware and software products that is small in size
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Examples of fifth generation computers include portable computers, artificial intelligence and natural
language processing systems
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4 Computer Laboratory and Computer Uses
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1 Computer Laboratory
A computer laboratory, simply referred to as a computer lab, is a special room set aside and prepared
specifically for safe installation and use of computers
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Measures should be put in place to protect the machines from theft or destruction and the
users from accidents
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Computer laboratory safety measures can be dived into two:
 Those that are meant to protect computers
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(a) Measures that protect computers
Burglar proofing the room: This involves fitting grills on doors, windows and the roof to deter forceful entry
into the computer room
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Installing fire prevention and control equipment such as smoke detectors and fire extinguishers: The
recommended extinguishers are gaseous type and should be non-liquid/non-powder based
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On the other hand, powder
particles may increase friction and wear off moving parts
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Providing stable power supply by installing surge protectors, power extension cables, uninterruptible power
supply (UPS) for each computers and power backup generator
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The room should be well laid out with enough space for movement
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Cables should be laid out in trunks away
from user paths to avoid stumbling on them
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Dust can be controlled by fitting good window curtains and an air
conditioning system that filters dust particles from the air entering the room
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On the other hand, dampness or humidity in the laboratory can be controlled by using dehumidifiers
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Cables and power sockets should be well insulated and of the correct power rating to avoid short circuits that
can damage computer components
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Food particle may fall in moving computer parts
like the keyboard and clog them while liquids may pour into electrical circuits and cause short circuits
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Cables should be laid away from user paths to avoid tripping on them
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The table should be of the right height relative to the seat to provide comfortable hand positioning
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Providing antiglare screens (light filters) and adjustable screen to avoid eye strain and fatigue caused by
over bright cathode ray tube (CRT) monitors
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The room should be properly ventilated to avoid dizziness caused by lack of adequate oxygen and to allow the
computers to cool
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Overcrowding in the computer room is not allowed
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Running and playing in the computer room is not allowed
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Some of the areas where
computers are used include:Retail stores to perform stock management and control
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Hospitals to keep patient records and control functionality of highly specialized machine life support
systems
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Communication to facilitate sending and receiving of messages on the internet
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Law enforcement agencies to perform biometric mapping activities like fingerprint matching and store
forensic information
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Home to prepare domestic documents like budgets and in communication
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Libraries to keep electronic catalogues and track book circulation
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Research institution to process and analyse data
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5 Basic Computer Hands-on Skills
In order to appreciate what a computer can do, it is important that you learn how to safely turn it on
and off as well as use the keyboard and mouse more effectively
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After a few seconds,
lines of text start to scroll on the screen
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POST checks on
the existing storage, basic input and output devices
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POST is accomplished by a special firmware program called the basic input output system (BIOS) which is
held in a ROM chip mounted on the motherboard
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CMOS is powered by a dry
cell that mostly resembles that of a digital watch
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Lastly, the operating system is read from the hard disk and loaded to the memory in a process called
booting
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Fig
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17 Windows Desktop
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2 The computer Keyboard
The keyboard such as the one shown in Fig
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enter data into the computer
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They are mainly used as shortcut to specialized operations in
application programs
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Typing keys: Their layout resembles that of a typewriter
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Numeric keyboard: They consists of mainly numeric characters 0 – 9, Num lock, arithmetic operators (/, - ,
+) and Enter
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Navigation and editing keys: They are used to control the cursor or pointer and edit text
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The include delete (Del), Insert (Ins), Home, page
up/ page down, End and arrow keys
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Special PC keys are Ctrl, Alt, Shift and Esc
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Typing skills
When using the keyboard, place your fingers on the home keys which are A, S, D, F and space bar for the
left hand and semi- colon (;), L,K,J, and spacebar for the right hand
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Fig
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19 shows hands resting on the home keys
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However, this similarity is vanishing out because of wireless technology which is doing away
with the cable
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At the
top are two buttons and an optional scroll wheel
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Fig
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20 A Mechanical Mouse
Mouse skills
The following are some mouse use techniques that can be performed with a standard mouse:Clicking: Clicking simply means pressing the default button (left) once
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Double clicking: Double clicking is to press the default button twice in rapid succession
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Drag and drop: Drag and drop involves holding down the default mouse button and then moving the
selected item to a new location on the screen then releasing the button
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This action displays the shortcut
menu
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13 \\ An Introduction to Computer Studies, By Instructor Bassu\\

COMPUTER SYSTEMS
Chapter 2
Outline

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0 Introduction
Basically, a computer is made up of two main components, namely hardware and software
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A computer system is a collection of three components namely hardware, software and liveware that
work together to receive, process, manage and present information in a meaningful format
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Software: Refers to sets of instructions that direct a computer on what to do
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Liveware: Refers to the human being
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However, in this chapter, emphasis is on the hardware and software
components
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1 Computer hardware
Computer hardware is classified into four categories namely input devices, central processing unit,
output device and storage devices
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Input devices can be classified according to the methods they use to enter data
namely: keying, pointing, scanning devices and other technologies used to capture data
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A keying device converts typed numbers, letters
and special characters into machine readable form before processing takes place
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Fig
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1: Flexible Keyboard
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(iii) Ergonomic keyboard
An ergonomic keyboard (Fig
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Fig
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It consists of keys identified by raised
dots
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They are mostly used on computers running
graphical user interface (GUI) operating systems such as Microsoft Windows
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(i) Mouse
Generally, there are three types of mice available in the market namely mechanical, optical and
cordless
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The optical mouse
The optical mouse has a pointing device (Fig
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and digital signal processing (DSP) in place of the traditional mouse ball and electromechanical
transducer
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It lets you quickly position the cursor on the screen without
using a cursor-movement key
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Create graphics such as freehand drawing
Fig
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5: An optical mouse
Cordless mouse
Cordless or wireless mouse (Fig
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instead of being physically connected to the system unit
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7) works just like a mouse only that its ball is located at the top
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Some computer keyboards come
with an integrated trackball hence no need for a mouse
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The user controls game
actions by varying the pressure, speed and direction of the joystick
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Fig
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8: Joysticks
(iv) Light pen and stylus
A light pen is a light-sensitive pointing device
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A stylus on the other hands is used on touch sensitive device such as
PDA screens that recognize a handwritten text
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Fig
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9: A Light pen and a stylus (in use on PDA)
(c) Scanning devices
Scanning means capturing data from an object and converting it into digital format
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(i) Optical scanners
Optical scanners capture data using optical or light technology
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Some examples of optical scanners include:
Optical mark recognition
Optical mark recognition (OMR) devices such as the one shown in Fig 2
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The position of the
mark relative to a fixed point of reference is analysed to determine whether it is in the required place
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Optical bar recognition
The optical bar code recognition (OBR) scanners are used to capture data coded as lines of varying
thickness known as bar codes or Universal Product Code (UPC)
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Bar codes do not have the price details because prices vary from one place to another
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Fig
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11 shows an illustration of a wand bar code reader and bar codes
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It is used to read typewritten, computer printed, or handwritten
characters and transform the images into a soft copy that can be manipulated using a word processor
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Flat bed
scanners are used to capture pictures and real objects
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The two common types of magnetic scanners are:
Magnetic ink character recognition
Magnetic ink character recognition (MICR) devices are used to read characters written using magnetic
ink
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Fig
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13: Cheque readers
Magnetic card reader
A magnetic card reader is used to read data coded on a magnetic strip on a plastic card such as the one
used on an automated teller machine (ATM) shown in fig
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14 and credit card reader
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A
microphone is attached to a sound card which has an analog-digital converter
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Fig
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15 shows a desktop
microphone
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(e) Touch screen
Touch screen (Fig
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16) works by allowing the user to touch the screen in order to select an item
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When the user touches a location on the screen,
the finger interrupts the infrared light and the command touched is executed
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The image drawn does not appear on the tablet but on the computer screen
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19 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Fig
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17: A graphic tablet
(g) Digital cameras
Digital cameras capture data the same way as other cameras do but the images are stored in digital
form
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The digital image taken can be streamed directly into a computer, uploaded to internet using a webcam
or directly printed using a special photo printer
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18 (a) shows as a still digital camera and Fig
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18 (b) a video digital camera
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2
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Or
A modem is a device that allows computer information to be transmitted and received over a telephone
line
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The receiving modem translates the analog signals back to digital form
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The transmitting modem compresses the data and the receiving computer or
modem decompresses the data back to its original state
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2 Central processing unit (CPU)
Central processing unit (CPU) also referred to as the processor is the central part of the computer where
data processing takes place
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As mentioned earlier, the CPU of a microcomputer also referred to as microprocessor, is a tiny chip
etched into a silicon chip
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20 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Fig
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19: A motherboard (and other parts)
Regardless of size, a processor consists of three functional elements namely control unit, arithmetic and
logic unit and main memory (primary storage)
(a) Control unit
The control unit is responsible for controlling all the activities in a computer
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Fig
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20 is a block diagram showing the
role of the control unit in the CPU
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Functions of this unit are: It is responsible for controlling the transfer of data and instructions among other units of a computer
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 It obtains the instructions from the memory, interprets them and directs the operation of the
computer
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 It does not process or store data
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Data to be executed by the ALU is temporarily held in special purpose memories located
inside the processor called registers
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All complex operations are done by making repetitive use of the above
operations
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(c) Main memory
The main memory stores data and instructions that are directly accessible to the processor
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Its size affects the speed, power and
capability of the computer
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 It stores intermediate results of processing
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 All inputs and outputs are transmitted through main memory
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(i) Random Access Memory (RAM)
Random access memory (RAM) mostly referred to as working storage is a volatile, temporary storage
that holds data entered into the computer for processing
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Hence a backup uninterruptible power
system (UPS) is often used with computers
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We can reach into
the memory at random & extremely fast but can also be quite expensive
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There are two types of RAM namely static RAM (SRAM) and dynamic RAM (DRAM)
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Due to its efficiency
SRAM is used on special purpose memories known as cache memory (discussed later)
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However, data is lost when the power gets down due to volatile nature
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Transistors do not require power to prevent leakage, so SRAM need not
have to be refreshed on a regular basis
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Characteristics of Static RAM:
 Faster access by the CPU
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 It has long data lifetime
 Used as cache memory
 Large in size
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 High power consumption
22 \\ An Introduction to Computer Studies, By Instructor Bassu\\

(2) Dynamic RAM
DRAM (shown in Fig
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21) is a relatively slower type of RAM compared to SRAM
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For this
reason, DRAM requires periodic recharging referred to as refreshment to maintain its data storage
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DRAM is used for most system memory because it is cheap and small
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These cells are composed of one capacitor and one transistor
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 Offers slower access time compared to SRAM (Slower as compared to SRAM)
 It has short data lifetime
 Used as RAM
 Lesser in size
 Less expensive
 Cheaper compared to SRAM
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Some commonly
available DRAMs include:
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It operates at a lower speed of between 60 ns
and 70 ns
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Extended data out (EDO) is an improvement on FPM
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When one piece of data is being sent to the processor, another is being retrieved from the RAM
module
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III
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IV
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V
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The memory uses a special Rambus channel that has a data transfer rate of 800MHz
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Double-data rate (DDR) RAM is a faster DRAM with double the rate of speed at which SDRAM can
transfer data to the processor
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Video RAM (VRAM) is a specialized type of memory that is used only with video adapters
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VIII
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The term ‘’window’’ refers to its ability
to retrieve large blocks (Windows) of data at one time
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Depending on the type of a PC you are using, if you open its system unit or
memory chamber of the laptop, you may find any of the following DRAM packages:

Dual-inline Packages (DIP) is attached directly into sockets on the system board
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These cards fit upright into
slots on the system board and are held in place by clips that prevent loosening
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Older Pentium computers included slots for both SIMM types
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Dual Inline memory module (DIMM) is new than the SIMM and is typically used in Pentium,
Pentium II and Pentium III computers
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RIMMs look just like DIMMs but have 184 connectors
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The
physical size is much smaller than DIMMs
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MicroDIMM is half the size of a SoDIMM and allows for higher density of storage
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(ii) Read Only Memory (ROM)
ROM stands for Read Only Memory, the memory from which we can only read but cannot write on it
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The information is stored permanently in such memories during
manufacture
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ROM chip (such as the one shown in Fig
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22) are
not only used in the computers but also in other electronic items like washing machines and microwave
ovens
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Firmware is a chip with
instructions in it
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 It is non-volatile hence permanent
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There are several types of ROM
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Mask ROM: This kind of ROM is written once at the time of manufacture and cannot be changed
afterwards
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Programmable ROM (PROM): This can be written only once by the user after which it cannot be
changed again
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The user buys a
blank PROM and enters the desired contents using a PROM programmer
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It can be programmed only once
and is not erasable
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Erasable Programmable ROM (EPROM): This is a special type of ROM that can be erased and
reprogrammed again by exposing it to ultra – violet light
...
Electrically erasable programmable ROM (EEPROM): This is programmed and erased electrically
under software control and can support selective modification of its contents
...
Both erasing and programming takes about 4 to 10 ms
(milliseconds)
...
EEPROMs can be erased one byte at a time, rather than erasing the entire chip
...
A BIOS chip found on a microcomputer’s
motherboard is an example of EEPROM
...
These memories include buffers, registers and cache memory
...
There are three types of cache memory
namely:
I
...
Level 2 also known as external cache that may be inside the microprocessor or mounted on the
motherboard
...
Level 3 is the latest type of cache that works with level 2 caches to optimise system performance
...
Input data is held in the input
buffer while processed data is held in output buffer
...

Registers
Registers are high speed memory location capable of holding only one piece of data item at time
...
They hold data and instructions just before or after processing in
the ALU
...
Program counter (PC) holds the memory address of the instruction to be fetched next
...
Instruction register (IR) holds the instruction that is currently being processed
...
Accumulator (AC) holds the results of the last processing step of the ALU
...
Address register (AR) holds the address of the next piece of data to be fetched for processing
...
Storage resister (SR) holds a piece of data that is on its way to and from the CPU
...
These are complex instruction set
computers (CISC) and reduced instruction set computers (RISC)
...


Complex instruction set computers (CISC) design is made up of complex instructions microcode into
the processor
...
Other manufactures such as AMD and Cyrix who produce Intel compatible chips use the
same technology
...


II
...
Motorola and Sun Microsystems companies are the main
manufacturers of RISC processors
...

MICROPROCESSORS AND THEIR CLOCK SPEEDS
Today, the microprocessor market is dominated by Intel Corporation
...


25 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Over time, these manufacturers have released a number of processor models
...
Table 2
...

Processor
Intel 8086
Intel 8088
Intel 80186
Intel 80286
Intel 80386
Intel 80486
Pentium

Year
1978
1979
1980
1982
1985 – 1990
1990
1993

Manufacturer
Intel
Intel
Intel
Intel
Intel
Intel
Intel

Pentium Pro

1995

AMD K5
Pentium MMX
Pentium II
AMD K6
Cyrix 6x86
Pentium III
AMD Athron
AMD Duron
Pentium 4
Intel Core 2
Duo
AMD Athron
Dual Core

1995
1997
1997
1997
1997
1999
1999
2000
Nov
...
5MHz
16 – 33MHz
Upgradable
60, 66, 75, 90, 100, 120, 133, 150, 166 and
200MHz
150, 166, 180 and 200MHz
75, 90, 100 and 116MHz
166, 200 and 233MHz with MMX technology
...
13GHz
500MHz to 2
...
8GHz
1
...
2GHz
> 1
...
0GHz x 2

Table 2
...
1
...
The most
common types of output data include text, pictures, sound and video
...

(a) Softcopy output devices
Softcopy can be defined as output that can be seen or heard but cannot be touched
...

(i) Monitors
A monitor, also known as visual display unit (VDU) or the screen, is used to display information in the
form of text, pictures and video, enabling the user to monitor what is going on in the computer
...
The
sharpness of the image depends upon the number of the pixels
...
LDCs and gas plasma displays are generally referred to as flat-panel
display
...
2
...

The flat-panel display refers to a class of video devices that have reduced volume, weight and power
requirement compare to the CRT
...
Current
uses for flat-panel displays include calculators, videogames, monitors, laptop computer, graphics
display
...
2
...
In a
colour monitor, a pixel has the three primary colours namely red, green and blue
...
It is measured in bits
...

The higher the resolution, the more the number of pixels per inch, hence the clearer the images
...

The video adapter determines the resolution and clarity of the monitor
...


Colour graphics adapter (CGA) displays text and images up to 16 colours
...
Enhanced graphics adapter (EGA) was an improvement of CGA but also displays in 16 colours
...
Video graphics array (VGA) displays text and graphics and video using 256 colours
...
Super video graphics array (SVGA) displays text and graphics using more than 16 million colours
...

V
...
It is popular with 17 and
19 inch monitors
...
Super extended graphics array (SXGA) has a resolution of 1280 × 1024 pixels and is popular with 19
and 21 inch monitors
...
Ultra extended graphics array (UXGA) is the latest and has the highest standard
...
If a screen has a low refresh rate, images tend to flicker
hence causing eyestrain
...

Cathode ray tube monitors
A cathode ray tube (CRT) monitor consists of a long glass tube with an electron gun on one end and a
screen on the other end
...

The smaller the pixels, the better the image clarity, or resolution
...
A finite number of characters can
be displayed on a screen at once
...
Most screens are capable of displaying
80 characters of data horizontally and 25 lines vertically
...

In the invar type, pixels are placed horizontally while in the Trinitron type, pixels are placed in a vertical
grid
...
Unlike CRTs, LCDs are less
bulky, consume less power and have little effect on eyes
...

There are two types of LCD monitors namely passive matrix and active matrix
...
This type of LCD requires little
power but has poor clarity
...
These displays consume more power than passive matrix but offer better clarity
...
They contain millions of pixels that are
illuminated by charged neon gas
...
For this reason this technology is becoming more popular
...

(ii) Sound output devices
Examples of sound output devices include speakers (Fig
...
25) and headphones
...
An external speaker should be
connected to sound card through the jacks on the system unit or on a multimedia monitor
...
2
...
2
...
It is a creative way of presenting computer output to an audience
...


Fig
...
26: An LCD projector
(b) Hardcopy output devices
Hardcopy can be defined as tangible output that can be seen and touched
...
Three commonly used hardcopy output devices are printers, plotters and facsimile (fax)
...

Impact printers
Impact printers print using striking mechanism
...
Impact printers are cheaper to run and print for long periods without breaking down
...

Characteristics of Impact Printers:





Very low consumable costs
Impact printers are very noisy
Useful for bulk printing due to low cost
There is physical contact with the paper to produce an image

Two examples of impact printers are dot matrix and daisywheel printers
...
2
...

A daisywheel printer (Fig
...
27b) has a removable flower-like wheel consisting of spokes with embossed
characters
...
However these printers are no longer in the market
...
2
...
They print using ink, thermal or
laser mechanisms
...

 They are not noisy
...

 Support many fonts and different character size
...

I
...
2
...
They
make less noise because no hammering is done and these have many styles of printing modes
available
...
The cartridge has nozzles that do the actual
spraying of ink on the paper
...
They are, however, slow as
compare to laser printers and more expensive to run due to the high cost of replacing the cartridges
...


29 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Fig
...
28: An Inkjet Printer
II
...
2
...
Thermal printers are mostly
used in point of sale terminals to print receipts and bar codes
...
They are, however, more expensive to purchase and run
...
2
...
Laser printers (Fig
...
30) operate by shining a laser beam to create an image on a rotating drum
...
The toner is then
fused onto a piece of paper
...
They are also
cheaper to run and produce printouts of high quality
...


Fig
...
30: Laser printer
IV
...
2
...


Fig
...
31 Photo printers
30 \\ An Introduction to Computer Studies, By Instructor Bassu\\

(ii) Plotters
A plotter (Fig
...
32) is used for printing wide format printouts mainly photographs, maps and
architectural designs
...
2
...
1
...
However, it offers long term storage for data and
information
...
)
(a) Removable magnetic storage
Magnetic storage media use magnetic technology to store data
...
Data is read and written into the
media using a device known as drive
...

Magnetic tapes
A Magnetic tape is made using a thin ribbon of Mylar (plastic) coated with a thin layer of magnetic
material composed of iron oxide
...
2
...


Fig
...
33: Magnetic tape
Floppy disks
A floppy disk is so called because of its flexible disk platter
...
The floppy disk is inserted inside a floppy drive which has a read/write
that runs over the magnetized sports
...
2
...
A floppy disk has
concentric circles called tracks in which data is written
...
2
...


31 \\ An Introduction to Computer Studies, By Instructor Bassu\\

(a) Front and rear of a floppy disk
(b) Imaginary tracks and sectors
Fig
...
34: Structure of a floppy disk
Caring for magnetic media
To avoid accidental loss of data or information held on magnetic media, the following rules must be
observed:
1
...
This would disorient the magnetic dipoles
causing erasure of the recorded data
...
Do not expose magnetic media to excessive heat
...

3
...

4
...

5
...

6
...

(b) Removable magneto-optical storage
Magneto-optical media stores data both magnetically and optically
...

Heating disorients the magnetic dipoles in the area and enables the magnetic head to rearrange them in
a new pattern that represents the data being written
...
Some examples of magneto-optical media
are the Zip and Jaz disks, HiFD and LS-120 superdisk
...
It is stable, inexpensive and
easy to work with
...
Fig
...
35 shows a zip disk in
an external drive
...
2
...
2
...
They are also read using an internal or external drive
...
2
...
HiFD drive can also
read the 1
...

(iv) Laser servo 120 super disks
Laser servo 120 super disks simply known as LS-120 superdisk can store up to 240 MB
...
44MB floppy disk
...
Fig
...
37 shows an example of an optical disk
...
2
...
The most common
include:
(i) Compact disks (CD): This is made of a small plastic disk with a reflective aluminum coating on one
side
...
There are three common types of CDs namely
read only, recordable and rewritable CDs
...


Compact disk read only memory (CD-ROM): As the name suggests contains data that can only
be read but cannot be written on
...
Compact disk recordable (CD-R): They are coated with special dye which changes colour to
represent data when burned using a laser beam
...
Both the CD-ROM and the CD-R are generally known as write once read many
(WORM) disks
...
Compact disk rewritable (CD-RW): Unlike a CD-R, the CD-RW disk can be erased and rewritten
more than once
...
It is also coated
with special dye which allows rewriting
...
For example, a typical DVD can store approximately 17 GB
...


33 \\ An Introduction to Computer Studies, By Instructor Bassu\\

(d) Solid state storage devices
Solid state storage is a kind of nonvolatile storage media that employs integrated circuits rather than
mechanical, magnetic or optical technology
...
Some examples of solid
state devices include flash disks and memory cards shown in Fig
...
38
...
2
...

(e) Fixed magnetic storage
A hard disk, also known as hard drive, is an example of fixed storage
...
It is called a hard disk because it is made up of metallic
disk platters (Fig
...
39) housed in a protective metal case
...

Most computers’ hard disks are connected to motherboard via channel called controller
...


Fig
...
39: Hard disk
Structure of a hard disk
Just like the floppy disk, a hard disk is made up of tracks and sectors
...
2
...

Some of the advantages of the hard disk over the other storage media is that they store very large
volumes of data and offer faster data access
...
2
...

 Keep the hard disk away from smoke and dust
...

2
...
5 Basic Computer Setup
Basic computer setup involves connecting the basic parts such as monitor, keyboard, mouse and
speakers to the system unit
...

Power supply unit and adapter
Though computers are connected to AC power outlet, internal components require DC power
...
Fig
...
41 (a)
shows a power supply unit while Fig
...
41 (b) shows an AC/DC adapter
...
2
...

A port is a connection point on your computer where you can connect devices that pass data into and
out of a computer
...
Fig
...
42 shows some
ports in a computer
...
2
...
These include serial, parallel connection, universal serial bus, PS/2,
video, firewire, infrared and Bluetooth ports
...


Serial ports: Also known as COM (communication) port or RS232 port, support transmission of data
one bit at a time
...
A serial port that enables data transfer rates of 12 Mbps is called USB
port
...
Parallel connection ports: Unlike a serial port, a parallel port, commonly referred to as LPT,
transmits more than one bit at a time
...

III
...
It can be used to connect as many as 127 peripheral devices to a
computer
...
Using USB,
you can connect and disconnect devices without shutting down or restarting your computer
...
A
USB port is usually located on the back of your computer near the serial port or parallel port
...
1) and a relatively faster high speed USB
(2
...

Plug and Play is a set of specifications developed by Intel that allows a computer to automatically
detect and configure a device (a plug and play device) and installs the appropriate device drivers
...
Non-Plug and Play
devices are becoming increasingly rare as manufacturers stop producing them in favour of Plug and
Play devices
...

IV
...
An example of PS/2 port is where PS/2 mouse and
keyboard are connected
...
Video port: A video port is where monitor is connected to LCD projectors
...

VI
...
It is mostly used for streaming video from a digital video camera
...
Infrared and Bluetooth: These are both wireless connectivity
...
Infrared (IR) is light that is beyond
red in the colour spectrum
...

Infrared-enabled devices must be at a line of sight of infrared rays in order to transmit data
...
Any Bluetoothenabled device when turned on will be detected
...
2 Computer Software
As mentioned earlier, the term computer software refers to a set of instructions that direct a computer
on what to do
...

2
...
1 System software
System software performs the fundamental operations that avail the computers resources to user
applications
...

(a) Operating systems
An operating system is a program that manages the computer hardware resources and controls the
execution of application programs
...

(b) Utility programs
Utility software, also called service programs, are special programs used to enhance performance of the
system
...
For example, the zebugger program automatically launches to
try and help an application to recover from an exception
...

2
...
2 Application Software
These are programs that are designed to meet user-specific needs
...

(a) Classification according to purpose
Classified according to purpose, an application software can be either a general purpose or specialpurpose software
...

On the other hand, special – purpose applications such as desktop publishing, video editing and photo
editing software are used to carry out specialized tasks
...
In-house developed software are tailored to meet specific needs within the
organization
...
Off-the-shelf
packages are widely used because:
 It takes less time to assess company needs, buy and install them
...

 They are readily available for almost any task
...

However, there are some drawbacks of off-the-shelf packages such as:
 They may have some features not need by the user which may take extra storage
...


2
...
Both of them must work together to make computer produce a useful output
...

Hardware without set of programs to operate upon cannot be utilized and is useless
...

Software development is very expensive and is a continuing expense
...

A software acts as an interface between the user and the hardware
...
Both are complimentary to
each other
...
4 Criteria for selecting computer system
Before acquiring computer hardware and software there is need to consider a number of factors
...
4
...
Fig 2
...


Desktop PC

Notebook PC
Apple iMac
Fig
...
43: Types of microcomputers

Some important factors you need to put into consideration include:
38 \\ An Introduction to Computer Studies, By Instructor Bassu\\

(a) Processor (CPU) types and speed
The price of a computer is dictated by the type of microprocessor installed and its clock speed
...
Consider:
 Frequency (GHz) - This determines speed of the processor
...

 Cores - Today's CPUs come with more than one core, which is like having more than one CPU in the
computer
...

 Brand - Intel or AMD
...
Intel is in lead
...
30 GHz Processor
(b) Memory capacity
Memory capacity dictates the operating system and the application that can run efficiently on the
computer
...

 Today's software and operating system requires high memory
...

Recommended - 4 GB
(c) Hard Drive




Hard disk is used for storage purpose
...

Now-a-day's computer are equipped with 500GB which can be extended to 2TB
...

Recommended - 500GB

(d) Optical Drive (CD / DVD / Blu-ray)






Optical drive is the drive on a computer which is responsible
to CD, DVD and Blu-ray disks
...

DVD Burner can burn CD, DVD and play them
...

Blu-ray drives can play HD movies but are costlier
component
...


(e) Display
Flat-panel display monitors are becoming more popular and are gradually replacing the traditional CRT
monitors
...
The larger the area, the bigger the picture screen
...
It will increase productivity as well
...
For example, 24-inch display is 1920x1200
(width by length) and 22-inch display which is 1680x1050
...

 Inputs - Now-a-days monitors can accept inputs from cable as well as apart from computer
...

 Stand - Some monitors provides adjustable stands but some may not
...

In most cases, the longer the warranty, the better the hardware
...
A good market survey would enable purchase of
genuine components at a reasonable cost
...

(i) Special needs
The hardware must be able to take care of the special need of the user
...

(j) Portability
Portable computers are ideal for people who do not take most of their time in an office
...

(k) Other considerations
Other considerations include available ports, wireless connectivity, multimedia and the system unit
form factor (whether tower type or desktop)
...
4
...
(Fig 2
...

Some important factors need to be put into consideration
...
Authenticity is
established by having the manufacture’s certificate of authenticity
...
A good software product must be accompanied with this documentation
...

(d) Reliability
Good software must be reliable and secure
...
However, GUIbased software may be difficult to use
...
The cost of acquiring a software product must be
carefully considered before acquiring it against the benefits that it is likely to bring
...

However, you may go for Free and Open Source Software (FOSS), which are now-a-days increasing in
their importance since most of them are not attached by malwares (like viruses, Trojan and worms)
...

For example:
Operating System
 Operating System is the main software of the computer as everything will run on it in one form or
other
...

 Linux is free but people generally do not use it for home purpose
...

 Windows 7 is very popular among desktop users
...

 Windows 8 is recently introduced and is available in market
...

 As edition version increases, their features list and price increases
...


41 \\ An Introduction to Computer Studies, By Instructor Bassu\\

OPERATING SYSTEMS
Chapter 3
Outline

3
...
1
3
...
3
3
...
5
3
...
7
3
...
0 Introduction
As mentioned earlier, an operating system is the main program that controls and manages the
computer’s hardware and software resources
...


3
...
1
...

It is an integration set of specialised programs that are used to manage overall resources and
operations of the computer
...


3
...
2 Objectives of Operating System:








Making a computer system convenient to use in an efficient manner
To hide the details of the hardware resources from the users
To provide users a convenient interface to use the computer system
...

Manage the resources of a computer system
...

The efficient and fair sharing of resources among users and programs

3
...
3 Characteristics of Operating System







Memory Management -- It keeps tracks of primary memory i
...
what part of it are in use by whom,
what part are not in use etc
...

Processor Management -- Allocate the processor (CPU) to a process
...

Device Management -- Keep tracks of all devices
...
Decides which
process gets the device when and for how much time
...
De-allocates the resource
...

Security -- By means of passwords & similar other techniques, preventing unauthorized access to
programs & data
...

42 \\ An Introduction to Computer Studies, By Instructor Bassu\\






Control over system performance -- Recording delays between request for a service & from the
system
...
Operating System acknowledges the same, do the corresponding action and
inform the operation by a display screen
...

Coordination between other software and users -- Coordination and assignment of compilers,
interpreters, assemblers and other software to the various users of the computer systems
...
2 Role, structure, resources and functions of an operating system
3
...
1 Role of an operating system
An operating system acts as the interface between the user applications and the computer hardware as
illustrated in Fig
...
1

Fig
...
1: The role of an operating system
3
...
2 Structure of an operating system
In order to control the interactions between various system resources, an operating system may consist
of a complicated set of layers with the lowest being the hardware and the highest being the user
application as shown in Fig
...
2
...
It is responsible for
managing the communication between hardware and software resources
...


Fig
...
2: Layered structure
43 \\ An Introduction to Computer Studies, By Instructor Bassu\\

3
...
3 Resources managed by an operating system
Processor: It is the operating system which determines which task (process) will be executed first
...

Input/output devices and ports: The operating system allocates requests from applications to
input/output devices
...

Secondary storage devices: The operating system manages the storage and retrieval of data from
backing storage
...
Protocol refers to the rules that govern
communication between devices on a network
...
2
...
Some tasks will be given priority over others due to the nature of request
...




Interrupt handling: An interrupt is a break from the sequential processing of a task or program by
transferring control to a new process that requests to be executed
...
Using the round robin technique, each process on the
queue is given access to a resource in turn
...




Memory management: The operating system divides the main memory into partitions
...

At any one time, not all the pages of a process may be held in the virtual memory
...




Error handling: The operating system performs error checking on hardware, software and data
...




Job sequencing: The operating system arranges tasks to be processed in a particular order and
clocks them in and out of the processor
...


3
...
These operating systems can be classified according to:
 Size of a computer
...

 Number of users
...

3
...
1 Classification according to size of computer
(a) Embedded operating systems
Embedded operating systems are those used on hand held devices such as mobile phones and PDAs
...
Fig 3
...

44 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Fig
...
3: Pocket PC running on Windows CE
(b) Desktop and network operating system
Some operating systems are meant for home users and are cheaper and easier to use
...
Examples are Windows
XP, Windows 7 and Windows 8
...

Examples of NOS include Windows 2000, XP and Vista, Novell Netware, UNIX and Linux etc
...
4
shows seven clients connected to a server
...
3
...
For example,
IBM VSE/ESA and zOS are used on mainframe computers
...
5 shows IBM zSeries 900 computer that
runs on VSE/ESA and zOS
...
3
...
3
...
Examples of such operating systems are
the early version of Microsoft disk operating system (MS DOS) and PC DOS
...
The CPU switches between various running
applications, making it appear as if they are running at the same time
...

3
...
3 Classification according to number of users
(a) Single-user operating systems
Single – user operating systems are designed to be used by one person at a time
...

(b) Multi-user operating systems
Multi-user operating systems allow more than one user to access system resources apparently at the
same time
...
Examples are Microsoft
NT/2000/2003 Server, Linux, Solaris, zOS and VSE/ESA
...
3
...
The three types of operating systems according to
user-interface are command-line, menu driven and graphical user-interface (GUI) operating systems
...

The computer reads the typed command from the command line and executes it
...
Fig 3
...


Fig
...
6: Command-line interface
Command-line operating systems have become unpopular because it is difficult to remember the
commands, they cannot process complex graphics and they hardly make use of emerging hardware and
software technologies
...
The user simply chooses commands from a list of menu options
...
7)
46 \\ An Introduction to Computer Studies, By Instructor Bassu\\

use menu driven interface
...
8) that
came with later versions of MS DOS
...
3
...
3
...
Beside
menus, GUI makes use of rectangular frames called windows, graphical objects called icons and most
commands are executed using a point device
...
Some examples of GUI operating systems include Microsoft
windows, MacOS and Linux
...
9 shows the MacOS desktop
...
3
...
3
...
These include:
 The hardware configuration of the computer such as the memory capacity, processor speed and hard
disk capacity
...
For example, some earlier Apple computers would
not run on Microsoft operating system
...

 User-friendliness of the operating system
...

 The cost of the operating system
...

 The number of processors and hardware it can support
...


47 \\ An Introduction to Computer Studies, By Instructor Bassu\\

3
...
The factors that dictate how information is to be organized are:
1
...

2
...

3
...

4
...

5
...

Most operating systems organize information in a three-tier hierarchy:
 Drive
 Folders and subfolders,
 Files
...
3
...
3
...
4
...
All folders or
directories originate from a special directory called the root directory or folder
...
A folder may be subdivided into smaller units called subfolders
...
4
...
The user can access either a physical or
logical drive to store their data
...
Table 3
...

Storage location
Floppy drive

A and B

Drive

Hard disk
Optical drives

C, D, E, F
D, E, F, G

Other removable

D, E, …, Z

Network drive

Logical drives D – Z

Remarks
If a computer has two floppy drives, one will be assigned letter A
and the other B
If a computer has 4 hard drives, they will be assigned letters C – F
If a computer has one hard disk and three or more CD/DVD drives,
they will take up any letters between D and Z
If a computer does not have an optical drive, any removable drive
attached to the computer can take any letter between D and Z
In a networked environment, network drives can take up letters D
to Z depending on the number of physical drives installed or
attached

Table 3
...
4
...
Every file has the following details:
1
...
The name and extension are separated by a period (
...
g
...
doc
...
Extensions are used to identify
the type of file, for example:
 Doc is a word processor file,
 Txt is a plain text file,
 Sys is a system file
...
The size, date and time the file was created or modified
...
System files contain information
that is critical for the operation of the computer
...

Data files contain user specific data
...
2 shows some files extension and whether it is a system,
application or data file
...
doc
Data
A Microsoft Word document file (Word 97-2003 document)

...
txt
Data
A plain text file created using notepad or any text editor

...
exe
Application file
The file that launches a particular application, e
...
Winword
...
exe, etc

...
sys
System file
System files that perform fundamental operations in a computer
Table 3
...
5 Managing files and folders using windows
Although there are different types of operating systems, most of them have common features
...
In this tutorial, we shall look at how to
manage files and folders using Microsoft windows
...
5
...

To display the explorer using the start menu:
1
...
In the search bar, type windows explorer (Fig
...
11)

Fig
...
11: Windows explorer command

Fig
...
12: Windows explorer window

49 \\ An Introduction to Computer Studies, By Instructor Bassu\\

3
...
2 Creating folders
Creating folders in the explorer window:
1
...

2
...
3
...
Replace the temporary New folder name with your choice
...
Press Enter

Click this button

Fig
...
13: Creating a folder
3
...
3 Creating files
To create a file in the explorer window:
1
...

2
...

3
...
3
...
Replace the temporary file name with your choice
...
Press Enter
...
3
...
Double click the file icon to start the application
...

7
...

50 \\ An Introduction to Computer Studies, By Instructor Bassu\\

3
...
4 Renaming files and folders
In the explorer window:
1
...

2
...

3
...

4
...

5
...

3
...
5 Deleting files and folders
In the explorer window:
1
...

2
...

3
...

4
...

5
...

6
...

Note: Files and folders deleted from removable drives such as diskettes and flash disks are not held in the
recycle bin but are completely lost
...
5
...

To copy a file or folder:
1
...

2
...

3
...

4
...

To move a file or folder:
1
...

2
...

3
...

4
...

3
...
7 Searching for files and folders
In case you are not sure where you stored a file or folder, use the search menu
...
Click start
2
...

3
...

Note: This applies to Windows 7, 8 and some versions of Linux

3
...

Since Windows do not come with Antivirus software, you need to install third party antivirus software
...
6
...
Other storage
devices which are not disks can also be formatted to create a file system on them
...
Double click My computer icon
...
Right click the drive to format
...
On the Shortcut menu, click Format
...
In the Format dialog box (Fig
...
16), specify the capacity, file system and label
...
Click Start
...
3
...
6
...

To scan a drive:
1
...

2
...
3
...

3
...

4
...


Fig
...
16: Scandisk dialog box
52 \\ An Introduction to Computer Studies, By Instructor Bassu\\

3
...
3 Defragmenting a disk
A single file may have several pieces (fragments) scattered in several non – contiguous sectors on a disk
...
To avoid this, the file should be defragmented
...

To defragment a disk:
1
...

2
...

3
...

4
...
Disk defragmenter of Fig
...
17 window is displayed
...
Select the volume to defragment
...
3
...
6
...
Three common types of malicious programs are viruses, Trojan horses
and worms
...

To scan for malware
1
...

2
...
The scan process is initialized
...
Heal, delete or quarantine the infected files
...
6
...
However, this result
in reduced performance and therefore it is not recommended unless your computer cannot
accommodate a large capacity disk:
To compress a disk:
1
...

2
...

3
...

4
...
Another dialog box is displayed
...
Click OK to apply changes
...
6
...
This prevents
complete loss of data in case the current storage location fails, gets lost or is destroyed
...
In My computer Window, right click the hard drive
...
From the Shortcut menu, click properties
...
In the properties dialog box, click Tools tab
...
Click Backup Now
...
The backup wizard guides you through the process
...
6
...
Windows 98 and Me have one startup disk while Windows 2000 and XP have 4
startup disks
...

3
...
8 Partitioning a disk
Partitioning a disk means dividing it into several volumes called logical drives
...
Each partition is treated as a
separate drive and will be assigned a drive letter
...

Choosing a file system
Before partitioning a disk, you need to decide how files are stored on each partition
...

 File Allocation Table 32 bit (FAT32) is primarily used in Windows 98 and Me
...


3
...
The documentation contains details of the minimum hardware requirements
a computer must meet
...
3 gives a summary of minimum or recommended system requirements
...
We shall look at how to
install Windows XP (only slight differences occur in the new version of windows)
...

 Clean installation
...


54 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Clean installation
To perform clean installation, the computer BIOS should be setup so that the computer boots from a
CD/DVD
...
In the BIOS setup, change the boot
sequence so that the computer boots from CD/DVD first
...
Insert the CD/DVD ROM into the CD/DVD drive
...
Turn on the computer
...

3
...

4
...

5
...
Accept the end user license agreement (EULA) then product key
...

7
...
Windows XP will successfully be
installed and you may be required to setup user accounts and connect to the Internet for updates
...
8 Troubleshooting and fixing problems
Windows operating systems may fail to boot or function properly due to hardware, malware, improper
installation or missing system files
...
8
...
Make sure the active partitions are
selected as the startup drive or reinstall the operating system
...
8
...
SYS, HIMEM
...
bat may result in boot failure
...

3
...
3 Corrupted system registry
Registry is the Windows database that keeps details about all system and application programs installed
in the computer
...
Repair the registry using
emergency repair disk or restore the registry backup if you created one
...

3
...
4 Failure to load the GUI desktop
Failure to load the GUI may be due to infection by malware, missing or corrupted display drivers
...

3
...
5 Windows protection error
Windows protection error is displayed during startup before the GUI is loaded
...
Restart the computer in safe mode
...

3
...
6 Runtime problems
Run-time problems may be characterized by the system’s failure to respond to commands
...
’’ Use the restart keys Ctrl + Alt + Delete to display the
Task Manager and try to close the non-responding applications
...

Note: For more information on troubleshooting and fixing an operating system related problems, read
the online help and support utility
...
0
Introduction
4
...
2
Number system
4
...
0 Introduction
A bit (binary digit) is the smallest unit of information handled by a computer
...
A group of 8 bits makes up a byte, which can
represent many types of information, such as a letter of the alphabet, a decimal digit, or other
character
...
Some single characters can take up more than one byte
...

Some languages, such as Japanese, Chinese, and Korean, require double-byte character sets
...
1 Memory Units
Memory unit is the amount of data that can be stored in the storage unit
...

Following are the main memory storage units:

Few higher storage units are following:

56 \\ An Introduction to Computer Studies, By Instructor Bassu\\

4
...
A computer can understand positional number system where there are only a
few symbols called digits and these symbols represent different values depending on the position they
occupy in the number
...

4
...
1 Decimal Number System
The number system that we use in our day-to-day life is the decimal number system
...
In decimal number system, the successive positions
to the left of the decimal point represent units, tens, hundreds, thousands and so on
...
For example, the decimal number 1234 consists of the digit
4 in the units position, 3 in the tens position, 2 in the hundreds position, and 1 in the thousands position,
and its value can be written as:
(1 x 1000) + (2 x 100) + (3 x 10) + (4 x 1)
(1 x 103) + (2 x 102) + (3 x 101) + (4 x 100)
1000 + 200 + 30 + 4
1234
As a computer programmer or an IT professional, you should understand the following number systems
which are frequently used in computers:

4
...
2 Binary Number System
Characteristics
 Uses two digits, 0 and 1
...
Example 20
 Last position in a binary number represents an x power of the base (2)
...

EXAMPLE:
Binary Number: 101012
Calculating Decimal Equivalent:

Note: 101012 is normally written as 10101
...
2
...

 Also called base 8 number system
 Each position in an octal number represents a 0 power of the base (8)
...
Example 8x where x
represents the last position - 1
...

4
...
4 Hexadecimal Number System
Characteristics
 Uses 10 digits and 6 letters; 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
...
A = 10, B = 11, C = 12, D = 13, E = 14, F = 15
...
Example 160
 Last position in a hexadecimal number represents an x power of the base (16)
...

EXAMPLE:
Hexadecimal Number: 19FDE16
Calculating Decimal Equivalent:

Note: 19FDE16 is normally written as 19FDE
...
3 Number Conversion
There are many methods or techniques which can be used to convert numbers from one base to
another
...
3
...

 Step 2 - Get the remainder from Step 1 as the rightmost digit (least significant digit) of new base
number
...

 Step 4 - Record the remainder from Step 3 as the next digit (to the left) of the new base number
...

The last remainder thus obtained will be the most significant digit (MSD) of the new base number
...

Decimal Number: 2910 = Binary Number: 111012
...
3
...

 Step 2 - Multiply the obtained column values (in Step 1) by the digits in the corresponding columns
...
The total is the equivalent value in decimal
...
3
...

 Step 2 - Convert the decimal number so obtained to the new base number
...
3
...

 Step 2 - Convert each group of three binary digits to one octal digit
...
3
...

 Step 2 - Combine all the resulting binary groups (of 3 digits each) into a single binary number
...
3
...

 Step 2 - Convert each group of four binary digits to one hexadecimal symbol
...
3
...

 Step 2 - Combine all the resulting binary groups (of 4 digits each) into a single binary number
...
1
What is data?
5
...
3
Data Processing Cycle
_____________________________________________________________________________________

5
...

Data is represented with the help of characters like alphabets (A-Z, a-z), digits (0-9) or special characters
(+,-, /, *, <, >, = etc)
...
5
...
Data
comes in many forms such as numbers, words and symbols
...

For example:
What could these numbers stand for?
20, 30, 45, 36, 23, 50, 26, 48, 63, 75
These are raw facts since they have no meaning attached to them
...
The processing could be having a calculation, sorting, interpretation, conversion or
grouping the data in a certain way
...
But if the numbers were 20 boys, 30 girls and a
45 years old man in a certain village then they are information that can be understood
...
2 Information
5
...
1 What is Information?
Information is organised or classified data so that it has some meaningful values to the receiver
...
For the decision to be
meaningful, the processed data must qualify for the following characteristics:
 Timely - Information should be available when required
...

 Completeness - Information should be complete
...
5
...
2
...
All confidential information which needs a kind of restriction from accessing is called
authentic information
...
Something you know: Examples, PIN number, Password or examination number, etc
2
...
Something you are: Examples, Palm prints, Finger prints, Retina (eye) scan, etc
5
...
3 Why do we need information?






For making budgets and financial control: You need to have information on requirements, plans,
costs and income in order to make budget
...

Information helps for condensing decision making process
...
You can know weakness
areas for resetting the planning, goals, objectives, policy and rules
...

A method of making things better and a means to achieving goals: Information can give us detailed
analysis on various current events, public opinions and immediate coverage of an event

5
...
4 Relationship between Data, Information and Knowledge
Data is the lowest level of abstraction/construct to be followed by information and lastly knowledge as
the highest stage
...
A body of information which is well organised within a
particular subject/ discipline constitutes knowledge
...


5
...
Data processing consists of basic steps input,
processing and output
...


63 \\ An Introduction to Computer Studies, By Instructor Bassu\\

Fig
...
3: Data Processing Cycle





Input - In this step the input data are prepared in some convenient form for processing
...
For example, when electronic computers are used, the input data
could be recorded on any one of several types of input medium, such as magnetic disks, tapes and so
on
...
For example,
pay-checks may be calculated from the time cards, or a summary of sales for the month may be
calculated from the sales orders
...
The particular form of the
output data depends on the use of the data
...


Fig
...
4: Data Processing Station

64 \\ An Introduction to Computer Studies, By Instructor Bassu\\

REFERENCES
Bill Ball, B and Smoogen, S (1998)
...
Indiana: Sams Publishing
and Red Hat Press
Computer Driving Certificate-SAUT Iringa
...
CDC Module 2: Using the Computer and Managing Files
Training Manual
Computer Hope
...
Retrieved on 4th
http://www
...
com/jargon
...
Computer sciences: Software and Hardware VOLUME2
...
Computer Basics
...
gcflearnfree
...
Computer Tutorials for Beginners
...
homeandlearn
...
uk/BC/BeginnersComputing
...
A complete illustrated Guide to the PC Hardware
...
mkdata
...
Gateway Secondary Revision: Computer Studies
...

Computer
Fundamentals
...
tutorialspoint
...
htm

Tutorials

Point
...

Retrieved
on
1st
http://www
...
com/cgibin/printversion
...
htm

May

2014

from

Varley, D (2004)
...
Cape Town: ICDL Foundation

65 \\ An Introduction to Computer Studies, By Instructor Bassu\\



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