JBD Computer Studies Book 8

Approved by the Government of Nepal, Ministry of Education, Curriculum Development
Centre (CDC), Sanothimi, Bhaktapur, Nepal as an additional material for schools.

JCBD omputer

Studies

8

Author
Sushma Pradhan

JBD Publication Pvt. Ltd.
Bhotahity, Kathmandu, Nepal

Published By

JBD Publication Pvt. Ltd.

Bhotahity, Kathmandu, Nepal
Tel: 01 - 4252371, 4313294
Email: [email protected]
Web : www.jbdbooks.com

© Reserved with publishers

First Edition : 2010 (2068 BS)
Second Edition (Revised and Updated) : 2015 (2072 BS)

Edition : Revised, 2019 (2076 BS)

ISBN: 978-9937-544-33-7

Author: Mrs. Sushma Pradhan

Mahabir Offset Press, Tel: 025-521634

Preface

Progress in information technology is affecting our lives more than ever.
Computers have played a key role in this, and they too have evolved at a
fast pace. Today, they are used in almost every sphere of life. It has become
imperative for us to know the usage of computers. Computer education
makes a child understand computer and its basic functions.
The ‘Computer Studies’ series is a set of computer books meant for students
of Primary and Middle School levels. The books have closely followed the
guidelines prepared by CDC, Government of Nepal. The book 8 of this series
is recommended for use in the eighth standard.
The series ‘Computer Studies’ has been written to impart computer skills
to students at different school stages. It is well focused on building a strong
foundation and achieving age-appropriate competency. Each chapter in the
book has a separate overview with plenty of illustrations and text supported
by screenshots on a Windows 7 platform. It is written in a very simple
language and chapters are presented in a user-friendly format.
Suggestions for further improvement from the users of the series will be
whole-heartedly appreciated and gratefully acknowledged.

Author

Contents 5
17
1. History of Computing 24
2. Generations of Computers 32
3. Types of Computers 41
4. Computer Software 51
5. Number System 64
6. Computer Network 71
7. Computer Viruses 80
8. ICT, Computer Ethics, Cyber Law 99
9. Operating System Software 117
10. More Features in Word 2010 131
11. More Features in PowerPoint 2010 146
12. More features in Excel 2010 163
13. Computer Graphics 180
14. HTML Programming 189
15. Algorithm and Flowchart 196
16. Basics of QBASIC 204
17. QBASIC Statements
18. Control Statements

Chapter 1

HISTORY
OF

COMPUTING

Objectives

After completing this chapter, you will be able to:

y List the features of an abacus.
y Name the inventor of Napier’s bones and list the features of Napier’s bones.
y List the features of difference engine and analytical engine.
y List the features of Harvard Mark - I
y List the features of Universal Automatic Computer-I

C Ooncept verview

Thousands of years ago, early men lived
nomadic and unorganized life. He felt no
need of keeping records. But gradually as
he began to settle down, he started keeping
animals, got involved in agriculture and
started to carry on barter trade with other
people. So, the early men felt the need of
a system to keep tracks of numbers. At
the early age people used pebbles, stones,
sticks, scratches, symbols and finger tips
to count, which were later replaced by
numbers. Later on, when man became
more civilized, abacus came into use. In
this chapter, you will learn the names of
a number of inventions and discoveries to
the development of modern computers.

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Computer Studies-8 5

Abacus

Abacus is one of the first mechanical calculating devices created by the Chinese.
It consists of a rectangular frame carrying a number of rods or wires. A horizontal
beam or mid bar separates the frame into two sections, known as the upper deck
and the lower deck. On the upper deck of each
rod are two beads and on the lower deck five
beads. The beads below the midbar represent
one of that rod’s units (that is, a one, a ten,
a hundred, and so forth), and those above
represent five. Beads are moved from the outer
position toward the cross beam when used to
represent a number. The abacus is still used by millions of people throughout Asia
and many children in the United States are introduced to this tool in kindergarten
or elementary school.

Napier’s Bone

John Napier, a Scottish mathematician, developed
the system of logarithms in 1614 which greatly
assisted in arithmetic calculations.He also invented
a small instrument called Napier’s Bones in 1617.
These bones were made up of rectangular strips of
wood or bones with figures marked on one side.
Each rod was divided into ten squares and in the top
square was a digit from 0 to 9. This simple device
enabled to carry out multiplication faster, provided
one of the numbers was a single digit number.

Slide Rule

William Oughtred, an English mathematician invented Slide Rule in 1620.
He wrote the “Circles of Proportion and Horizontal Instrument” in 1632. He
invented both the standard rectilinear slide rule and the less commonly used
slide rule. He used the principle of bones and logarithms. It is a device consisting
of two logarithmically scaled rules mounted to slide along each other so that
multiplication, division, and other more complex computations are reduced to
the mechanical equivalent of addition or subtraction. It is considered as the first
analog computing device.

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Pascal’s Calculator
Blaise Pascal, a French philosopher, mathematician, and physicist, invented the
first mechanical calculator called Pascalina in 1642. The calculator had spoked
metal wheel dials, with the digits 0 through 9 displayed around the circumference
of each wheel. The numbers were entered by dialing a series of numbered wheels,
where the movement of the wheels started at 9 and moved to 0. An automatic
carry over system was accomplished by rotating the adjacent wheel by one
digit. This machine was capable of performing addition and subtraction only
supporting as many as 8 digits while multiplication and division operations were
done by repeated addition and subtraction respectively.

Stepped Reckoner
Gottfried Wilhem Von Leibniz, a German mathematician and philosopher,
invented a digital mechanical calculator called Stepped Reckoner in 1694. It
consisted of additional sets of wheels that could perform all four arithmetic
operations: addition, subtraction, multiplication and division. The machine was
about 67 cm (26 inches) long, made of polished brass and steel, mounted in an
oak case. Pascal’s and Leibniz’s devices were the forebears of today’s desktop
computers.

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Jacquard Loom
In 1801, French silk weaver Joseph Marie Jacquard
invented the Jacquard Loom that weaved complex designs.
Jacquard invented a way of automatically controlling
the warp and weft threads on a silk loom by recording
patterns of holes in a string of cards. The Jacquard cards
were later modified and evolved into computing punch
cards by Charles Babbage and later Herman Hollerith.
The Jacquard loom started a technological revolution in
the textile industry, and the system of punched cards
used in its operation became a prototype for the first
mechanical computers.

Difference Engine and Analytical Engine
Charles Babbage, an English Mathematician, designed an automatic mechanical
calculating machine, called a Difference Engine in 1823 that could solve equations
by calculating the differences between them. Babbage improved on the Difference
Engine and designed a more sophisticated machine called Analytical Engine in
1833. This machine had the following four units:
• Input and output unit to read data and display the result.
• Store to hold data and results of processing.
• Mill a mechanical unit for calculations.
• A system of gears and levers to transfer the data between the store

and the mill.
The analytical engine was designed but was never built by Babbage because
the technology of manufacturing exact technical parts was not well developed.
Thus the unavailability of the technical parts constrained the machine from
working. However, he was honoured as the father of computers as a result of his
contributions to the basic design of the computer.

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Lady Augusta Ada Lovelace
Augusta Ada King, Countess of Lovelace is mainly known for having written
a description of Charles Babbage’s early mechanical general-purpose computer,
the analytical engine. This was the first time that the concept of computer
programming was suggested and historians have credited Lady Ada as the
first computer programmer. In 1979, the US Defence Department named a
programming language ADA in her honour.

Tabulating Machine
Herman Hollerith, American inventor, invented a Tabulating Machine in 1887.
The purpose of the tabulating machine was to speed up the process of assimilating
census data into a usable form that would meet the needs of a country that was
experiencing a significant growth in population from one decade to the next.
In 1896, Hollerith founded the Tabulating Machine Company. Within twenty
years, this company merged with three others to form the Computing Tabulating
Recording Corporation. As the organization grew and diversified, another name
change occurred in 1924, when the company became known as IBM.

Harvard Mark I
Howard Aiken, an electrical engineer and physicist, designed the first automatic
electromechanical computer called Harvard Mark-I in 1937. The Mark-I was
completed in 1944. It was used by the US Navy for gunnery and ballistic
calculations. It was built using 7,65,000 components and hundreds of miles of
wire, amounting to a size of 51 feet in length, 8 feet in height, and 2 feet deep. It
had a weight of about 4500 kg. It was also known as the IBM Automatic Sequence
Controlled Calculator (ASCC). It is considered to be “the beginning of the era of
the modern computer” and “the real dawn of the computer age”.

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Atanasoff Berry Computer
John Vincent Atanasoff and Clifford Berry at Iowa State University, built the
world’s first electronic digital computer, Atanasoff Berry Computer in 1937-38.
The vacuum tubes were used in this computer for storing and for arithmetic logic
functions. It was designed for solving systems of simultaneous linear equations.
It was used by military to compute ballistic data.

Electronic Numerical Integrator and Calculator
J. Presper Eckert and John Mauchly at the University of Pennsylvania in
Philadelphia developed the first operational electronic digital computer, ENIAC
in 1946 for the U.S. Army. It used 18,000 vacuum tubes, weighed 30 tons and took
up 1,800 square feet. It was used to prepare artillery-shell trajectory tables and
perform other military and scientific calculations.

Electronic Discrete Variable Automatic Computer
John Mauchly and J.P. Eckert designed
one of the earliest electronic computer
called Electronic Discrete Variable
Automatic Computer (EDVAC) in
1946 and started operating only
in 1951. The EDVAC was a binary
serial computer with automatic
addition, subtraction, multiplication,
programmed division and automatic
checking with an ultrasonic serial
memory, It included a magnetic
tape, a control unit, a dispatcher unit
to receive instructions and direct them to other units, a computational unit to
perform arithmetic operations, a dual memory unit and three temporary tanks.
The computer had almost 6,000 vacuum tubes and consumed 56 kW of power.

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10 Computer Studies-8

Electronic Delay Storage Automatic Calculator

Maurice V. Wilkes and his team at the university of Cambridge constructed
the first practical stored-program
electronic computer called EDSAC in
1949. It had 3,000 vacuum tubes and
used 30 kilowatts of electric power.
The computer contained 32 mercury
delay lines for memory with an access
time of one millisecond. Addition
was done in 1500 microseconds and
multiplication in 4000 microsecond.
Standing six feet tall and in three long
racks were the control and arithmetic
units. Programs were input using
paper tape and output results were printed on a teletype page printer.

Universal Automatic Computer-I

Universal Automatic Computer-I (UNIVAC-I) was the first commercial computer
produced in the United States. It was designed principally by John Mauchly and
J.P. Eckert. The UNIVAC-I was started in 1946 and completed in 1951. It was
used in Census Bureau in early 1951 for taking census. It was also based on the
EDVAC design. UNIVAC I used 5,200 vacuum tubes, weighed 29,000 pounds (13
metric tons), consumed 125 kW, and could perform about 1,905 operations per
second running on a 2.25 MHz clock. It was 8 ft high and 15 feet long.

Apple I

The original Apple Computer, also
known retroactively as the Apple I,
or Apple-1, is a personal computer
released by the Apple Computer
Company (now Apple Inc.) in 1976.
They were designed and hand-built
by Steve Wozniak. Wozniak’s friend
Steve Jobs had the idea of selling the
computer. It was demonstrated in July
1976 at the Homebrew Computer Club
in Palo Alto, California. It required
a keyboard and an inexpensive
television set.

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IBM Personal Computer

The IBM Personal Computer, commonly known
as the IBM PC was introduced on August 12,
1981. It was created by a team of engineers and
designers under the direction of Don Estridge of
the IBM Entry Systems Division in Baco Raton,
Florida. It was a complete computer system
programmable in BASIC or APL, with a small
built-in CRT monitor, keyboard, and tape drive
for data storage.

Macintosh

Macintosh, or Mac, is a series of several lines
of personal computers designed, developed,
and marketed by Apple Inc. The Macintosh
was introduced on January 24, 1984; it was
the first commercially successful personal
computer to feature a mouse and a graphical
user interface rather than a command-line
interface. The Macintosh runs on its own
operating system, Mac OS (currently Mac
OS X). The Mac originally ran on Motorola’s
68000 series microprocessors and then
moved to the PowerPC processor. Current
models use Intel x86 processors.

Pentium Processor

Pentium Processor is a family of 32-bit CPU
chips from Intel. Pentium chips have been the
most widely used in the world for general-
purpose computing. It was introduced on
March 22, 1993. The last of the series were the
dual-core Pentium 4 models, and the Pentium
was superseded by the Core in 2006. Pentium
4 (P4) is the Intel processor (codenamed
Willamette) that was released in November
2000. The P4 processor has a viable clock
speed that now exceeds 2 gigahertz (GHz) - as
compared to the 1 GHz of the Pentium 3.

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Different stages of development are as follows:

1994 Netscape Communications Corporation is founded

January 1994 Yahoo founded January 1994

24th August 1995 Microsoft launches Windows 95

1996 eBay is founded by Jeff Skoll and Pierre Omidyar

1996 Apple Computer buys NeXT

3rd May 1997 IBM’s Deep Blue Beats Gary Kasparov at Chess

2nd September 1997 IBM announces RS/6000 SP Deep Blue

May 1998 Introduction of Apple iMac

25th June 1998 Microsoft launches Windows 98

August 1998 Apple Release the iMac

September 1998 Foundation of Google by Larry Page and Sergey Brin

1999 Napster the first file sharing program introduced

11th October 1999 Nvidia releases GeForce 256

17th February 2000 Microsoft launches Windows 2000

1st June 2000 Intel ES7000 server from Unisys introduced

17th October 2001 Apple Launches a New Music Device - The iPod

25th October 2001 Microsoft Releases Windows XP

7th November 2002 Microsoft and partners launch Tablet PC

24th April 2003 Microsoft launches Windows Server 2003

9th November 2004 Firefox 1.0 Introduced

2007 iPhone introduced

30th January 2007 Microsoft launches Windows Vista and Office 2007

2008 The HD player war comes to an end

26th August 2008 Virus Found On Computer In Space Station

22nd October 2008 Android operating system released

15th November 2013 PlayStation 4 released

22nd November 2013 Xbox One released

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C Dompu- ictionary

Abacus : The first mechanical calculating device invented by
Slide Rule the Chinese 3000 years ago.
Punched card
Processor : A mechanical analog computer. The slide rule is used
Vacuum tube primarily for multiplication and division, and also for
functions such as roots, logarithms and trigonometry.

: A piece of stiff paper that contains digital information
represented by the presence or absence of holes in
predefined positions.

: An electronic circuit which executes computer
programs, containing a processing unit and a control
unit

: A device used to amplify, switch, otherwise modify, or
create an electronic signal by controlling the movement
of electrons in a low-pressure space.

Recap

• Abacus consists of a rectangular frame carrying a number of rods or wires. A
horizontal beam or mid bar separates the frame into two sections, known as
the upper deck and the lower deck.

• John Napier, a Scottish mathematician, developed the system of logarithms in
1614 which greatly assisted in arithmetic calculations.

• William Oughtred, an English mathematician invented Slide Rule in 1620.

• Blaise Pascal, a French philosopher, mathematician, and physicist, invented
the first mechanical calculator called Pascalina in 1642.

• Gottfried Wilhem Von Leibniz, a German mathematician and philosopher,
invented a digital mechanical calculator called Stepped Reckoner in 1694.

• Charles Babbage, an English Mathematician, designed an automatic
mechanical calculating machine, called a Difference Engine in 1823 that could
solve equations by calculating the differences between them.

• Herman Hollerith, American inventor, invented a Tabulating Machine in 1887.

• Howard Aiken, an electrical engineer and physicist, designed the first
automatic electromechanical computer called Harvard Mark-I in 1937.

• John Vincent Atanasoff and Clifford Berry at Iowa State University, built the
world’s first electronic digital computer, Atanasoff Berry Computer in 1937-
38.

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Review Yourself

1. State whether the following statements are true or false.
a. William Oughtred, a Scottish mathematician, developed the system of
logarithms in 1614 which greatly assisted in arithmetic calculations.
b. Blaise Pascal, a French philosopher, mathematician, and physicist,
invented the first mechanical calculator called Pascalina in 1642.
c. John Mauchly, a German mathematician and philosopher, invented a
digital mechanical calculator called Stepped Reckoner in 1694.
d. In 1979, the US Defence Department named a programming language
ADA in her honour.
e. The IBM Personal Computer, commonly known as the IBM PC was
introduced on August 12, 1981.

2. Fill in the blanks.
a. __________ a Scottish mathematician, developed the system of logarithms
in 1614 which greatly assisted in arithmetic calculations.
b. ___________ Von Leibniz, a German mathematician and philosopher,
invented a digital mechanical calculator called Stepped Reckoner in
1694.
c. ___________ American inventor, invented a Tabulating Machine in 1887.
d. ____________ and John Mauchly at the University of Pennsylvania in
Philadelphia developed the first operational electronic digital computer,
ENIAC in 1946 for the U.S. Army.
e. ___________Automatic Computer-I (UNIVAC-I) was the first commercial
computer produced in the United States. It was designed principally by
John Mauchly and J.P. Eckert.

3. Match the following.

John Napier Jacquard’s Loom

Joseph-Marie Jacquard Tabulating Machine

Charles Babbage Napier’s Bones

Herman Hollerith Harvard Mark-I

Howard Aiken Difference Engine

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Computer Studies-8 15

4. Give the full form of the following abbreviations.

a. ABC b. ENIAC c. EDSAC

d. UNIVAC e. EDVAC f. IBM

5. Give one word answer for the following.

a. The first mechanical calculating device invented by the Chinese 3000
years ago.

b. A mechanical analog computer. The slide rule is used primarily for
multiplication and division, and also for functions such as roots,
logarithms and trigonometry.

c. A piece of stiff paper that contains digital information represented by
the presence or absence of holes in predefined positions.

d. An electronic circuit which executes computer programs, containing a
processing unit and a control unit

e. A device used to amplify, switch, otherwise modify, or create an
electronic signal by controlling the movement of electrons in a low-
pressure space.

6. Answer the following questions.
a. What is an abacus? What are the features of an abacus?
b. What is slide rule? Who invented slide rule?
c. What are features of pascal’s calculator?
d. What is the use of Jacquard’s Loom? Who invented it?
e. Why is Charles Babbage called “Father of Modern Computers”?
f. What did Herman Hollerith invent? What is the use of this machine?
g. Who invented Atanasoff Berry Computer? What are its features?
h. What is the full form of ENIAC and what are its features?
i. Name the first general-purpose electronic digital computer designed
for commercial use. Who invented it?
j. Who developed the personal computer and when?
k. Who invented IBM Personal Computer?
l. What is pentium processor? When was it invented?

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16 Computer Studies-8

Chapter 2

Generations of
Computers

Objectives

After completing this chapter, you will be able to:

y List the major features of the first generation of computers.

y List the major features of the second generation of computers.

y List the major features of the third generation of computers.

y List the major features of the fourth generation of computers.

y List the special features of fifth generation of computers.

C Ooncept verview 17

The evolution of modern digital computing is often
divided into generations. The development of
computers took place in five distinct phases known
as computer generations. This term is also used
in the different advancements of new computer
technology. With each new generation, the circuitry
has gotten smaller and more advanced than the
previous generation before it. As a result of the
miniaturization, speed, power, and computer memory
has proportionally increased. New discoveries are
constantly being developed that affect the way we
live, work and play.

Each generation of computers is characterized by
major technological development that fundamentally
changed the way computers operate, resulting in
increasingly smaller, cheaper, more powerful and
more efficient and reliable devices.

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First Generations of Computers(1946 - 1958)

First generation of electronic computers began with the
development of vacuum tubes as the internal electronic
components. The vacuum tubes required great amounts of
energy and generated much heat. They also burned out easily
and were hard to maintain. Vacuum tube was developed by
Lee DeForest in 1908.

The features of first generation computers are:

• The electronic circuitry was based on thermionic valves and vacuum
tubes.

• They were restricted to commercial and scientific applications.
• The system cost and working cost were very high.
• They were relatively unreliable due to the failure of vacuum tubes and

heating problem.
• They were extremely large and occupied a very large space.
• The operating speed was limited to the milliseconds range.
The examples of first generation computers are Universal Automatic Computer
(UNIVAC), Electronic Numerical Integrator and Calculator (ENIAC), Electronic
Delay Storage Automatic Computer (EDSAC), BURROUGHS 220 and Electronic
Discrete Variable Automatic Computer (EDVAC).

The Second Generation(1959-1964)

The second generation computers were developed
during the second decade of the electronic computer
era (approximately 1959-1964). The second generation
of electronic computers began with the development of
the transistor (electronic switching device). The three
Bell Lab scientists’, John Burdeen, Walter Brattain, and
William Shockley, working for Bell Labs invented the
transistor in 1947 which won the Nobel Prize in 1956.

The features of second generation computers are:

• Vacuum tubes were replaced by transistors in their electronic circuitry.

• They were less expensive, smaller in size due to miniaturization of electronic
device.

• There was an overall reduction in system and operating costs.
• They required less electricity and emitted less heat than vacuum tubes.
• They were more reliable and accurate than the first generation computers.

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18 Computer Studies-8

• An increase in operating speed up to the microseconds range.

• Machine-independent “high level” programming languages such ALGOL,
COBOL, FORTRAN were introduced to simplify programming.

The examples of the second generations are IBM 1620, IBM 1401, Control Data
Corporation 3600, 400 series, LEO Mark III and IBM 7094.

The Third Generation(1965-1974)

The development of the integrated circuit was the
hallmark of the third generation of computers. The third
generation computers were developed during 1965 to
1974. The development of Integrated Circuit (IC) signalled
the beginning of the third generation computers. The first
integrated circuit was developed in 1958 by Jack Kilby
of Texas Instruments and Robert Noyce of Fairchild
Semiconductor.

The features of third generation computers are:

• Transistors were replaced by Integrated Circuits in their electronic circuitry.

• Magnetic disks were used for auxiliary memory.

• The size of the computer became much smaller.

• Monitors and keyboards were introduced for data input and output
respectively.

• The reliability and accuracy of these systems improved and their MTBF went
up to several hundreds of hours.

• The speed of operation was improved to nanoseconds.

• They had a larger storage capacity.

• They were reliable and better in performance.

• A further development of high level language, including RPG (Report
Program Generator) and Pascal were introduced.

The examples of third generation computers are IBM system/360, National Cash
Register Century Series, ICL 1900 series, DATA GENERAL range and IBM 370
series.

The Fourth Generation(1975-1990) 19

The fourth generation of computer system saw the use of
Large Scale Integration (LSI) that could fit hundreds of
components onto one chip and Very Large Scale Integration
(VLSI) squeezed hundreds of thousands of components
onto a chip in the construction of computing elements.

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Computer Studies-8

These developments were followed by the creation of microprocessors. The first
microprocessor called Intel 4004 was developed by American Intel Corporation
in 1971.
The features of fourth generation computers are:
• Large Scale Integration (LSI), and later Very Large Scale Integration (VLSI),

are the advances that occurred in this generation.
• The computers were highly reliable and accurate.
• The operating speed was excellent, measured in picoseconds.
• A further refinement of input/output devices took place.
• Micro computers were introduced.
• Magnetic disk became the common source of external storage.
• Fourth Generation Language and application software for microcomputers

became popular.
The examples of this generation are IBM PC, Apple/Macintosh, HP3000 and the
SUPERBRAIN.

The Fifth Generation

The ‘Fifth Generation Computer Systems project (FGCS)
was an initiative by Japan’s Ministry of International
Trade and Industry, begun in 1982, to create a “fifth
generation computer” which was supposed to perform
much calculation using massive parallel processing. It
was to be the result of a massive government/industry
research project in Japan during the 1980s. It aimed to
createan“epoch-makingcomputer”withsupercomputer-
like performance and to provide a platform for future
developments in artificial intelligence.
The features of fifth generation computers are:
• In fifth-generation computers, the program instructions will be divided

among multiple processors of the computers, so that each processor will have
fewer tasks to perform, and thus, the program will run in less time. Although
the parallel processing system has been applied to some fourth-generation
computers, they cannot be called fifth-generation computers because they do
not run full artificial intelligence operations.
• These computers will use super conductor technology. The two future devices
are Gallium Arsenide (GaAs) chips and Biochips.
• These computers will have artificial intelligence.

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C Dompu- ictionary

Artificial Intelligence: A branch of computer science that refers to the use of
computer in such a way that they are able to reason and
draw, recognize voice and have language processing
ability.

Integrated circuit : A small electronic device made out of a semiconductor
material.

Vacuum tubes : The valves that permit the flow of electrons in one
direction and the flow can be controlled by adjusting
the electric potential on metal plates.

VLSI : A term describing semiconductor Integrated Circuits
composed of hundreds of thousands of circuits.

Transistor : A small electronic device containing a semiconductor
and having at least three electrical contacts, used in a
circuit as an amplifier, detector, or switch.

Recap

• The development of the computer took place in five distinct phases known as
generations of computers.

• First generation of electronic computers began with the development of
vacuum tubes as the internal electronic components.

• The second generation computers were developed during the second decade
of the electronic computer era (approximately 1959-1964).

• The second generation of electronic computers began with the development of
the transistor (electronic switching device).

• The three Bell Lab scientists’, John Burdeen, Walter Brattain, and William
Shockley, working for Bell Labs invented the transistor in 1947 which won the
Nobel Prize in 1956.

• The development of the integrated circuit was the hallmark of the third
generation of computers.

• The first integrated circuit was developed in 1958 by Jack Kilby of Texas
Instruments and Robert Noyce of Fairchild Semiconductor.

• The first microprocessor called Intel 4004 was developed by American Intel
Corporation in 1971.

• The examples of this generation are IBM PC, Apple/Macintosh, HP3000 and
the SUPERBRAIN.

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Computer Studies-8 21

Review Yourself

1. State whether the following statements are true or false.

a. The development of the computer took place in five distinct phases
known as generations of computers.

b. Vacuum tube was developed by William Shockley in 1908.

c. The second generation computers were developed during the second
decade of the electronic computer era (approximately 1959-1964).

d. The examples of fourth generation computers are IBM system/360,
National Cash Register Century Series, ICL 1900 series, DATA GENERAL
range and IBM 370 series.

e. The fifth generation of computers will have artificial intelligence.

2. Fill in the blanks.

a. First generation of electronic computers began with the development of
______________ as the internal electronic components.

b. The first integrated circuit was developed in 1958 by ________________
of Texas Instruments and Robert Noyce of Fairchild Semiconductor.

c. The first microprocessor called _______________ was developed by
American Intel Corporation in 1971.

d. The examples of __________________ generation are IBM PC, Apple/
Macintosh, HP3000 and the SUPERBRAIN.

e. The fifth generation computers will have _____________________.

3. Match the following. Column B
Column A Artificial Intelligence
First generation Vacuum Tubes
Second generation Transistors
Third generation Integrated Circuits
Fourth generation Microprocessors
Fifth generation

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22 Computer Studies-8

4. Select the best answer from the list of choices.

a. First generation of electronic computers began with the development
of ______________________ as the internal electronic components.

i. vacuum tubes ii. transistors

iii. microprocessor iv. none of the above

b. Vacuum tube was developed by ______________________ in 1908.

i. John Burdeen ii. Lee DeForest

iii. Walter Brattain iv. none of the above

c. The examples of third generation computers are ______________,
___________________ and _________________________.

i. IBM system/360 ii. ICL 1900 serie

iii. IBM 370 series. iv. all of the above

d. The first microprocessor called Intel 4004 was developed by American
Intel Corporation in _________________________.

i. 1971 ii. 1972

iii. 1973 iv. none of the above

e. ________________________ computers will have artificial intelligence.

i. first generation ii. second generation

iii. fourth generation iv. none of the above

5. Answer the following h.
a. What is meant by generations of computers? How many generations
of computers are there?
b. State the limitations of the first generation of computers.
c. List any three major features of the following generations:
i. Second generation of computers
ii. Fourth generation of computers
iii. Fifth generation of computers
d. What is an IC? Who invented it?
e. Name the inventors of transistors.
f. What is artificial intelligence?

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Computer Studies-8 23

Chapter 3

Types of
Computers

Objectives

After completing this chapter, you will be able to:

y Compare and contrast the different types of computers.
y Explain the difference between analog, digital and hybrid computers.
y Describe the classification of computers based on their size, cost, application areas

and computing power.
y Describe the features of different types of microcomputers.

C Ooncept verview

Computers have revolutionized all types of
industries. They have proved to be a boon to
mankind. The different types of computers are
in use today due to the continuing advances
in computing technology. Computers are
available in different shapes, sizes and
weights, due to these different shapes and
sizes they perform different sorts of jobs from
one another. All the computers are designed
by the qualified computer architectures that
design these machines as their requirements.
A computer that is used in a home differs in
size and shape from the computer being used
in a hospital. Computers are broadly divided
into three groups on the basis of computing
techniques used. These are analog, digital and
hybrid computers.

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24 Computer Studies-8

Analog Computer
Analog computer is a machine or electronic circuit designed to work on numerical
data represented by some physical quantity (e.g. rotation or displacement) or
electrical quantity (e.g. voltage or charge) which varies continuously. It is a
single problem oriented machine. It is widely used in simulating the operation of
aircraft, nuclear power plants, and industrial chemical processes. Speedometers,
thermometers and wrist watches are different kinds of analog computers.

Digital Computer
Digital computer is a computer that stores data in terms of digits (numbers)
and proceeds in discrete steps from one state to the next. The states of a
digital computer typically involve binary digits which may take the form
of the presence or absence of magnetic markers in a storage medium, on-off
switches or relays. In digital computers, even letters, words and whole texts
are represented digitally. It is used in business applications, scientific and
military areas. Personal computers are commonly used digital computers.
It can be further classified according to their difference in size, cost,
application areas and computing power. They are as follows:
• Supercomputers
• Mainframe computers
• Minicomputers
• Microcomputers

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Supercomputer
Supercomputer is extremely powerful computer capable of manipulating
massive amounts of data in a relatively short time. It has a highest computation
rate and largest memory. It has more than one CPU, often functioning in parallel
(simultaneously). It handles many thousands of operations simultaneously. It
is very expensive and are employed for specialized scientific and engineering
applications that must handle very large databases or do a great amount of
computation. Supercomputer is used to design automobiles, aircrafts and
spacecrafts; to forecast the weather and global climate; to design new drugs and
chemical compounds; and to make calculations that help scientists understand the
properties of particles that make up atoms as well as the behaviour and evolution
of stars and galaxies. The examples of supercomputer are CRAY-XMP-14, CRAY-
1 and CYBER 170/730.

Mainframe computer
Mainframe computer is a high-speed performance computer with heavy use of
input/output units such as large-capacity disks and printers. It requires a strict
environmental condition of air, dust and temperature control. It can support
hundreds or thousands of connected users and can execute many programs
simultaneously. It acts as the central host computer in distributed data processing
systems. It is used for applications such as payroll computations, accounting,
business transactions, information retrieval, airline seat reservations, and
scientific and engineering computations. The examples of mainframe computer
are IBM 4300 series, ICL 39 series and IBM 1401.

Minicomputer
Minicomputer is a medium-sized computer. It is designed to meet the computing
needs for several people simultaneously in a small to medium size business

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26 Computer Studies-8

environment. It supports lesser connected users than a mainframe computer. It
has slower operation speed and lesser memory capacity than mainframe. Mini
computers are used in medium sized organization for the processing of payrolls
and financial accounts, cost handling, sales analysis and production planning.
They are commonly used as servers in network environments that handle
the data-sharing needs of other computers on the network. The examples of
minicomputer are VAX 7500, Digital PDP-11 and HP 300.

Microcomputer
Microcomputer is a small digital computer based on a microprocessor and
designed to be used by one person at a time. It is connected with a few hardware
devices. It has limited memory capacity and it works at a slower speed. It is
capable of processing small volumes of data. It is more popularly known as
Personal Computer or PCs. It is used as home computers or in small businesses
where volumes of data processing and speed requirements are small. The two
popular series of microcomputer are IBM PC and Apple Macintosh.
Microcomputers include the following types: desktop computer, workstation,
laptop computer and palmtop.

Desktop and Tower Models
Desktop model is a computer that fits conveniently on the surface of a business
desk. A desktop computer’s main case (called the system unit) is horizontally
oriented, which means that it can lie flat on a desk or table. It is broad and low. It
is designed to be very small and are sometimes referred to slimline model.
Tower model is a computer in which the power supply, motherboard, and mass
storage devices are stacked on top of each other in a cabinet. It sits vertically and
is often placed on the floor to preserve desk space, allowing more room to place
external components, such as scanners or printers, on the desk.

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Laptop

Laptop computer is a personal computer
for mobile use. A laptop utilizes most
of the same components as a desktop
computer, including a display, a keyboard,
a pointing device such as a touchpad (also
known as a trackpad) and/or a pointing
stick, and speakers into a single unit. A
laptop is powered by mains electricity
via an AC adapter, and can be used away
from an outlet using a rechargeable
battery. Laptops are also sometimes
called notebook computers, notebooks or
netbooks.

Palmtop

Palmtop computer is an ultra portable
computer that literally fits in your palm.
It uses a pen to enter information. It uses
small cards to store programs and data. It
has to be plugged into a main computer
for other uses. It is generally used for
simple applications such as personal
organizations and note taking. Examples
of Handheld PC devices are the NEC
MobilePro 900c and HP 320LX.

Hybrid Computer

Hybrid computer is a digital computer that accepts analog signals, converts
them to digital and processes them in digital form. This integration is obtained
by digital to analog and analog to digital converter. A hybrid computer may use
or produce analog data or digital data. It accepts a continuously varying input,
which is then converted into a set of discrete values for digital processing. A
hybrid computer system setup offers a cost-effective method of performing
complex simulations. A hybrid computer capable of real-time solution has been
less expensive than any equivalent digital computer. Hybrid computers have been
necessary for successful system development. An example of a hybrid computer
is the computer used in hospitals to measure the heartbeat of the patient. Hybrid
Machines are generally used in scientific applications or in controlling industrial
processes.

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C Dompu- ictionary

Analog computer : A computer that operates on data by measuring
changes in continuous physical variables such as
voltage, resistance and rotation.

Digital computer : A computer capable of solving problems by processing
information in discrete form.

Hybrid computer : A computer which combines the best features of both
analog and digital computers.

Supercomputer : A powerful computer capable of manipulating massive
amounts of data in a relatively short time.

Mainframe computer : A high-speed performance computer with heavy use
of input/output units such as large-capacity disks and
printers.

Mini computer : A medium-sized computer basically developed for
use in process control systems.

Recap

• Analog computer is a machine or electronic circuit designed to work on
numerical data represented by some physical quantity (e.g. rotation or
displacement) or electrical quantity (e.g. voltage or charge) which varies
continuously.

• Digital computer is a computer that stores data in terms of digits
(numbers) and proceeds in discrete steps from one state to the next.

• Supercomputer is extremely powerful computer capable of manipulating
massive amounts of data in a relatively short time.

• Mainframe computer is a high-speed performance computer with heavy use
of input/output units such as large-capacity disks and printers.

• Minicomputer is a medium-sized computer. It is designed to meet the
computing needs for several people simultaneously in a small to medium size
business environment.

• Microcomputer is a small digital computer based on a microprocessor and
designed to be used by one person at a time.

• Laptop computer is a personal computer for mobile use.

• Palmtop computer is an ultra portable computer that literally fits in your palm.

• Hybrid computer is a digital computer that accepts analog signals, converts
them to digital and processes them in digital form.

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Review Yourself

1. State whether the following statements are true or false.

a. Speedometers, thermometers and wrist watches are different kinds of
analog computers.

b. Analog computer is a computer that stores data in terms of digits
(numbers) and proceeds in discrete steps from one state to the next.

c. Microcomputer is a small digital computer based on a microprocessor
and designed to be used by one person at a time.

d. Super computer is a personal computer for mobile use.

e. Hybrid computer is a digital computer that accepts analog signals,
converts them to digital and processes them in digital form.

2. Give one word for each of the following.

a. A computer that operates on data by measuring changes in continuous
physical variables such as voltage, resistance and rotation.

b. A computer capable of solving problems by processing information in
discrete form.

c. A computer which combines the best features of both analog and digital
computers.

d. A powerful computer capable of manipulating massive amounts of data
in a relatively short time.

e. A high-speed performance computer with heavy use of input/output
units such as large-capacity disks and printers.

3. Match the following. Description
Types of computer A computer capable of solving problems by
Supercomputer processing information in discrete form.
Mini computer A computer which combines the best features
Digital computer of both analog and digital computers.
A powerful computer capable of manipulating
Hybrid computer massive amounts of data in a relatively short
time.
Mainframe computer A high-speed performance computer with
heavy use of input/output units such as large-
capacity disks and printers.
A medium-sized computer basically developed
for use in process control systems.

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30 Computer Studies-8

4. Answer the following questions.
a. Explain analog computers with examples.
b. Explain digital computers with examples.
c. What are the types of digital computer
d. Arrange the following computers in terms of size and performance.
e. Minicomputers, Mainframe, Microcomputer, Supercomputers.
f. What are super computers and for what purposes are they used?
g. What is a mainframe and what are its typical applications?
h. What is a minicomputer? Where is it used?
i. What is a microcomputer? List the different types of microcomputer.
j. What is a laptop computer?
k. What is a palmtop computer?
l. What is a hybrid computer?

5. Identify and name the following computers.

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Chapter 4

Computer
Software

Objectives

After completing this chapter, you will be able to:

y Define the term computer software and list the major types of computer software.
y Define system software and explain the different types of system software.
y List the important functions of an operating system.
y Define application software and explain the two major types of application

software.

C Ooncept verview

A computer cannot do anything on its own.
It consists of hardware components which
needs instructions to solve a problem
or execute a task. Hence, it is necessary
to specify a sequence of instructions to
carry out a specific task. Such sequence of
instructions is called a program. Software
is a generic term for organized collections
of computer data and instructions, often
broken into two major categories: system
software that provides the basic non-task-
specific functions of the computer, and
application software which is used by
users to accomplish specific tasks. It is the
‘heart’ of the computer system. It enables
the hardware to operate; without them, a
computer can not do anything at all.

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Computer Software
Software is the basic component of a computer system. It is defined as instructions
and associated data stored in electronic format that directs the computer to
accomplish a task. There are different types of software to perform a variety of
tasks. These software are broadly classified into two categories. They are:
• System software
• Application software

System Software
System software is a program that manages and supports the computer resources
and operations of a computer system while it executes various tasks such
as processing data and information, controlling hardware components, and
allowing users to use application software. That is, systems software functions
as a bridge between computer system hardware and the application software.
System software is made up of many control programs, including the operating
system, communications software and database manager. It helps the hardware
components work together and provides support for the development and
execution of application software. Without the system software, the computer
cannot operate as a single unit. It includes combination of the following:
• Operating system
• Device driver
• Language processor
• Utility program

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operating System

Operating system software is a master
control program that controls and
supervises the hardware of a computer
system and provides services to
computer users. It controls the flow
of signals from CPU to various parts
of the computer. It acts as a medium
between the hardware and the user or
application software. All the computer
systems run under OS control ranging
from the small personal computers
to the largest supercomputers and
mainframes. The most popular
operating systems include:

Microsoft-Disk Operating System

Windows 98

Windows NT

Microsoft Windows

Mac OS

Linux

An operating system performs the following functions:

• Controls and coordinates peripheral devices

• Monitors the use of the machine’s resources

• Helps the application programs execute its instructions

• Helps user to develop programs

• Deals with any faults that may occur in the computer and informs the operator

Device Driver

Device driver is a program that allows a hardware peripheral, such as a printer, to
communicate with a computer. Drivers are hardware-dependent and operating-
system-specific. Device driver essentially converts the more general input/
output instructions of the operating system to messages that the device type can
understand. There are device drivers for printers, displays, CD-ROM readers,
disk drives and so on.

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Translator Programs

Translator programs are part of the system software of the computer. It translates
the instructions written in human convenient form to machine language codes
understood by the computer. The translator programs are loaded into the Random
Access Memory at the time of translation process. There is one translating
program for each programming language.

There are three types of translator programs. They are:

Assembler Assembler is a computer program which
translates the assembly language programming
into machine language program.

Compiler Compiler is a computer program that translates
a high level language program into a machine
language program instantly. It reports all
the errors of the program along with the line
numbers. Some of the programming languages
such as C, and C++ use compilers.

Interpreter Interpreter is a program that translates and
executes a program written in a high level
language, line by line. If an error is found on any
line, it is immediately reported to the user and
the execution of the program is stopped. The
programming language BASIC normally uses
an interpreter.

The major differences between compiler and interpreter are:

• Error correction is much simpler in the case of the interpreter because it is
done in stages. The compiler produces an error list for the entire program at
the end.

• Interpreters take more time for the execution of a program compared to
compilers because a statement has to be translated every time it is read.

Assembly Language Code High Level Language Code

Assembler Compiler/Interpreter

Machine Language Code

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Utility Program

Utility program is a program that ensures the smooth
functioning of the computer. It performs routine tasks,
such as formatting disks, copying files from disk,
sorting files and editing files, as well as other important
housekeeping functions. Many operating systems have
utility programs built directly into the operating system
itself. Other utility programs are sold separately as
software packages that the user must install. A number
of different kinds of utility programs are available. In
addition to disk utility routines already built into most
operating systems, many users add disk toolkits, data
compression utilities, backup utility programs, virus
protectors and screen savers to their systems.

Application Software

Application software is a computer program
designed to handle a particular task required by
the end-user. Application software can manipulate
text, numbers, graphics or a combination of
these depending on the work for which it was
designed. Application software thus includes word
processors, spreadsheets, database management,
inventory and payroll programs and many other
“applications”. Application software may be
written by a large software house which distributes
its products widely and addresses a general class
of problems, or may be written by an individual
and addresses a particular problem.

There are two types of application software:

• Customized or Tailored software

• Packaged software

Customized or Tailored software

Customized or tailored software is the software designed to meet the specific
requirements of an organization or individual. Tailored software is written on
the demand of individual’s need and serve only single organization. Some of the
examples of tailored software are payroll package, inventory package and library
information system.

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Packaged software

Packaged software is a generalized set of programs that allow the computer
to perform a specific data processing job for the user. These programs are user
friendly and designed for use in more than one environment. Packaged software
may be purchased from software vendors. Some of the most popular packaged
software are:

• Word Processing

• Database Management System

• Graphics packages

• Communication software

Database Management System Database management system is a complex
set of programs that control the organization,
storage and retrieval of data for many users.
Examples of Database Management Systems
are Oracle, Sybase, dBASE IV and MS-SQL
Server.

Graphics packages Graphics packages provide powerful design
tools that make it easy for anyone to outline,
create, edit, arrange and display complex
slide presentations. Some of the popular
presentation graphics packages are Microsoft
PowerPoint and Harvard Presentation
Graphics.

Communications software Communications software allows to
communicate to any location in the world
using either fax or electronic mail. A fax
transmits whatever copy is on an original
sheet of paper (text, graphics, or handwriting)
to another computer or fax machine. Electronic
mail (e-mail) is a text message. It remains in
the receiver’s computer until retrieved.

Word Processing Word processing package is a packaged
software that provides extensive tools for
creating, editing, storing and printing all
kinds of text-based documents. Some of the
com monly used word processing packages
are Microsoft Word, PageMaker and AmiPro.

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C Dompu- ictionary

Program : A set of instructions written in computer language
which instructs a computer to perform a specified

task.

Assembler : A built-in computer program which translates the
assembly language programming into machine

language program.

Compiler : A special program that translates a high level language

program into a machine code in a single operation.

Interpreter : A program that translates one statement of a high-level
language program into machine codes and executes

it.

System software : The collection of programs design to operate, control
and manage the actual operation of the computer

equipment.

Device driver : A program that allows a hardware peripheral, such as
a printer, to communicate with a computer.

Recap

• Software is a computer program, a series of instructions that tells the computer
what to do to make it work.

• There are two types of software which are required to use a computer: system
software and application software.

• System software is a set of one or more programs that are basically designed
to control and manage the operation of a computer system.

• Operating system is a master control program that controls and supervises a
computer system’s hardware and provides services to computer users.

• Device driver is a program that allows a hardware peripheral, such as a printer,
to communicate with a computer.

• Translating programs transform instructions prepared by people using
convenient languages into the machine language codes required by the
computers.

• Utility program is a program that ensure the smooth functioning of the
computer.

• Application software is a computer program designed to handle a particular
task required by the end-user.

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Review Yourself

1. State whether the following statements are true or false.
a. Software is the entire set of programs, procedures, and routines associated
with the operation of a computer system, including the operating system.
b. Without the system software, the computer cannot operate as a single unit.
c. Compiler is a program that translates and executes a program written in
a high level language, line by line.
d. Tailored software is written on the demand of individual’s need and
serve only single organization.
e. Word processing software allows to communicate to any location in the
world using either fax or electronic mail.

2. Fill in the blanks.
a. _____________ software is a master control program that controls and
supervises the hardware of a computer system and provides services to
computer users.
b. _________________ translates the instructions written in human
convenient form to machine language codes understood by the
computer.
c. ___________ is a computer program that translates a high level language
program into a machine language program instantly.
d. _________________ is the software designed to meet the specific
requirements of an organization or individual.
e. A ________________ software is a generalized set of programs that allow
the computer to perform a specific data processing job for the user.

3. Give the answer in one word.
a. The entire set of programs, procedures and routines associated with the
operation of a computer system, including the operating system.
b. A master control program that controls and supervises the hardware of
a computer system, and provides services to computer users.
c. A program that allows a hardware peripheral, such as a printer, to
communicate with a computer.
d. A program that ensures the smooth functioning of the computer.
e. A packaged software that provides extensive tools for creating, editing,
storing and printing all kinds of text-based documents.

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4. Match the following. A program that allows a hardware peripheral,
Utility program such as a printer, to communicate with a
computer.
Compiler
A computer program which translates the
Device driver assembly language programming into
machine language program
Assembler
A computer program that translates a high
Interpreter level language program into a machine
language program at once.

A program that translates and executes a
program written in a high level language, line
by line.

A program that ensure the smooth functioning
of the computer.

5. Answer the following questions.
a. What do you understand by the term “computer software”?
b. What is a system software? Give an example of system software.
c. What is an operating system? State the functions of operating system.
d. What is device driver?
e. What is a translating program? Name the three translating programs.
f. What is an assembler?
g. What is a compiler? What are the differences between an interpreter
and a compiler?
h. What is utility program? Name any two utility programs.
i. What is an application software? What are the two types of application
software?
j. What is a tailored software? Give few examples of such software.
k. What is a packaged software? Give examples of a packaged software.

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40 Computer Studies-8

Chapter 5

Number
System

Objectives

After completing this chapter, you will be able to:

y Explain the most commonly used computer numbering system.

y Explain how to convert from one number system to another.

y Explain how the arithmetic operations are performed.

C Ooncept verview

The number system plays an important role
in computer calculations. The arithmetic
calculations are performed with decimal number
system in our daily life but the decimal number
system is not suitable for digital computers as the
manipulation of decimal switches could become
quite complex. In the base 10 (decimal) number
system, one of the 10 values: 0,1, 2, 3, 4, 5, 6, 7,
8, 9 is used for each digit of a number. The most
natural system for representing numbers in a
computer is base 2, in which data is represented
as a collection of 1s and 0s where ‘1’ marks
the state of presence and ‘0’ marks the state of
absence. There are other number systems, which
are useful in the study of computers such as octal
number system has base 8 which is the third
power of two (23 = 8) and hexadecimal number
system has base 16 which is the fourth power of
two (24 = 16). Let us have a brief idea of the most
commonly used numbering system.

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Binary number system
A system of numbers consisting of only two digits, 0 and 1 is called binary number
system. This is ideal for representing patterns of bits, with 0 expressing a bit that
is turned off and 1 expressing a bit that is turned on. It has base 2. The 0s and 1s
can be arranged in various combinations to represent all the numbers, letters, and
symbols that can be entered into the computer.

Decimal number system
A system of numbers having base 10 is called decimal number system. It utilizes
the symbols of the numbers from 0 to 9. It is also called denary number system.
The value that the digits represent depends on the “weight” or position they
hold.

Octal number system
A system of numbers having base 8 is called octal number system. Octal number
system utilizes the digits from 0 to 7. The positional weight is based on the power
of 8. The octal system is used in computing as a simple means of expressing
binary quantities.

Hexadecimal number system
A system of numbers having base 16 is called hexadecimal number system. The
symbols used in this system are the decimal digits 0 through 9 and six additional
digits which are generally represented as A, B, C, D, E and F. The positional
weight is based on the power of 16.

Binary to Decimal Conversion
A binary number can be converted to its decimal equivalent by the following
method.
• Multiply each digit of binary number by base of the number (i.e. 2) raised to

the power of the positional notation taken from the extreme right.
• All the products of multiplication are added to get the decimal equivalent of

the number.
• Multiply each digit of binary number by base of the number (i.e. 2) raised to

the power of the positional notation taken from the extreme right.
• All the products of multiplication are added to get the decimal equivalent of

the number.

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Example

Convert the binary number (101010)2 to it decimal equivalent.
Solution:

Binary number = 1 0 1 0 1 0

Positional notation = 5 4 3 2 1 0

Now, apply the method of converting binary to decimal system.

Binary number = 1 0 1 0 1 0

= (1x25)+( 0x24) + (1x23) + (0x22)+(1x21) + (0x20)

= (1x32)+(0x16) + (1x8) +(0x4)+(1x2) + (0x1)

= 32 + 0 + 8 + 0 + 2 + 0

= 4210

Thus, (101010)2 = (42)10

Decimal to Binary Conversion
A decimal number can be converted to its binary equivalent by the following
method.
• Divide the decimal number by 2 successively.
• Keep a note of the remainders in one column.
• Repeat the process until the quotient is zero.
• The answer is obtained by writing the remainder in the reverse order.

Example

Convert the decimal number 10410 into binary equivalent.
Solution:

Remainder

2 104 0

2 52 0

2 26 0

2 13 1

2 6 0

2 3 1

2 1 1

0

Thus, (104)10 = (1101000)2

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Decimal to Octal Conversion

Divide the given number by the base of octal number (i.e.8) successively. The
division is continued till the quotient itself is less than 8. The answer is obtained
by writing the remainders in the reverse order.

Example

Convert 16010 into octal.
Solution:

Remainder

8 160 0

8 20 4

2 2

Thus, 16010 = 2408

Octal to Decimal Conversion

Multiply each octal digits by 8 raised to the power of the positional notation
taken from the extreme right.

Example

Convert 4178 into decimal equivalent.

Solution:

Octal number = 4 1 7

Positional notation = 2 1 0

Now, apply the method of converting octal to decimal system.

Procedure = (4x82) + (1x81) + (7x80)

= (4x64) + (1x8) + (7x1)

= 256 + 8 + 7

Answer = 27110
Thus, 4178 = 27110

Decimal to Hexadecimal Conversion
Divide the given number by the base of hexadecimal number(i.e.16) successively.
The division is continued till the quotient itself is less than 16. The answer is
obtained by writing the remainders in the reverse order.

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Example

Convert 95210 into hexadecimal equivalent.
Solution:

Remainder

16 952 8

16 59 11 = B

3 3



Thus, 95210 = 3B816

Hexadecimal to Decimal Conversion

Multiply each hexadecimal digits by 16 raised to the power of the positional
notation taken from the extreme right.

Example

Convert 31D16 into decimal number.
Solution:

Hexadecimal number = 3 1 D

Positional notation = 2 1 0

Procedure = (3x162) + (1x161) + (Dx160)

= (3x162) + (1x161) + (13x160)

= (3x256) + (1x16) + (13x1) i.e. D=13 from the table

= 768 + 16 + 13

= 79710
Thus, 31D16 = 79710

Binary Arithmetic
Arithmetic operations (i.e. addition, subtraction, multiplication and division) in
binary number system are simple.
The binary addition rules are shown in the table below:

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A B A+B
000
011
101
1 1 0 with 1 carry over

Example

Add 101110 with 100101.
Solution:

1 0 1 1 1 0 (Addend)

1 0 0 1 0 1 (Augend)

1 0 1 0 0 1 1 (Sum)

The binary subtraction rules are shown in the table below:

A B A-B
000
110
101
0 1 1 with 1 borrow

Example

Subtract 10110 from 11011.

Solution:

1 1 0 1 1 (Minuend)
1 0 1 1 0 (Subtrahend)

0 0 1 0 1 (Difference)

The binary multiplication rules are shown in the table below:

A B AxB
0 0 0
1 1 1
1 0 0
0 1 0

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46 Computer Studies-8

Example

Multiply 1011 with 10001.

Solution:
1 0 1 1
x 1 0 0 0 1
1 0 1 1
0 0 0 0 x
0 0 0 0 x x
0 0 0 0 x x x
1 0 1 1 x x x x
1 0 1 1 1 0 1 1

The binary division rules are shown in the table below:

A B AxB
0 1 0
1 1 1
1 0
0 0 Not Defined
0
Example

Divide 11110 by 101.

Solution:

1 0 1) 1 1 1 1 0 ( 1 1 0

1 0 1

1010

1010

x

Quotient = 110

Remainder = 0

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Computer Studies-8 47

C Dompu- ictionary

Number system : An organized and systematic way of representing
numbers.

Decimal number system : A number system having base 10.

Binary number system : A number system consisting of only two digits, 0
and 1.

Octal number system : A number system having the base 8.

Hexadecimal number : A number system having the base 16.

Recap

• The most used natural system for representing numbers in a computer is base
2, in which data is represented as a collection of 1’s and 0’s where ‘1’ marks the
state of presence and ‘0’ marks the state of absence.

• A number system having base 10 is called decimal number system.
• Decimal number system consists of the numbers from 0 to 9.
• A number system consisting of only two digits, 0 and 1 is called binary number

system. It has base 2.
• A number system having the base 8 is called octal number system.
• Octal number system utilizes the digits from 0 to 7.
• A number system having the base 16 is called hexadecimal number system.
• Hexadecimal number system contains the digits 0 to 9 and the letters A to F.
• BIT is the smallest unit of information handled by a computer.
• Nibble is a group of 4 bits.
• Byte is a combination of 8 bits.
• Kilobyte (KB) is a unit of computer memory or data storage capacity equal to

1,024 bytes.
• Megabyte (MB) is a unit of computer memory or data storage capacity equal

to 1,024 KB.
• Gigabyte (GB) is a unit of computer memory or data storage capacity equal to

1,024 MB.
• Terabyte (TB) is a unit of computer memory or data storage capacity equal to

1,024 GB.
• Petabyte (PB) is a unit of computer memory or data storage capacity equal to

1,024 TB.

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48 Computer Studies-8

Review Yourself

1. State whether the following statements are true or false.

a. The most natural system for representing numbers in a computer is base 2.

b. A system of numbers consisting of only two digits, 0 and 1 is called
decimal number system.

c. The symbols used in hexadecimal system are the decimal digits 0 through
9 and six additional digits which are generally represented as A, B, C, D,
E and F.

d. BIT is a combination of 8 bytes.

e. Kilobyte (KB) is a unit of computer memory or data storage capacity
equal to 1,024 bytes.

2. Fill in the blanks.

a. ____________ is a combination of 8 bits.

b. ____________ is a unit of computer memory or data storage capacity
equal to 1,024 KB.

c. ____________ is a unit of computer memory or data storage capacity
equal to 1,024 MB.

d. ____________ is a unit of computer memory or data storage capacity
equal to 1,024 GB.

e. ____________ is a unit of computer memory or data storage capacity
equal to 1,024 TB.

3. Match the following.

Gigabyte A group of 4 bits.

Megabyte A combination of 8 bits.

Byte A unit of computer memory or data storage capacity equal to
1,024 bytes.

Nibble A unit of computer memory or data storage capacity equal to
1,024 KB.

Kilobyte A unit of computer memory or data storage capacity equal to
1,024 MB.

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Computer Studies-8 49

4. Answer the following questions.
a. What is a computer number system? List the most commonly used
computer numbering system.
b. What is a binary number system?
c. What is a decimal number system?
d. What is byte?
e. What is bit?
f. What is nibble?
g. What is exabyte?

5. Convert the following as indicated.

a. 11100012 = (?)10
b. 1001112 = (?)10
c 356210 = (?)2
d. 876410 = (?)2
e. 85710 = (?)8
f. 46010 = (?)8
g. 4178 = (?)10
h. 3118 = (?)10
i. 100710 = (?)16
j. 23010 = (?)16
k. 27B16 = (?)10
l. ABC16 = (?)10

6. Solve the following binary arithmetic. b. 100100 + 11101
a. 11011 + 10000 d. 111011 - 11011
c. 111111 - 1101 f. 110111 x 1001
e. 10101 x 11001 h. 111011 ÷ 11
g. 101101 ÷ 101

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50 Computer Studies-8