NEW GATEWAY
TO
COMPUTER SCIENCE
9
Approved by Government of Nepal, Ministry of Education, Curriculum Development
Centre, Sanothimi, Bhaktapur as an Additional Learning Material.
NEW GATEWAY
TO
COMPUTER SCIENCE
9
Authors
Dinesh Adhikari
Dilendra Prasad Bhatta
Shekhar Poudel
Laxman Adhikari
Shubharambha Publication Pvt. Ltd.
Kathmandu, Nepal
Published by:
Shubharambha Publication Pvt. Ltd.
Kathmandu, Nepal
URL: www.shubharambhapublication.com
E-mail: [email protected]
www.facebook.com/shubharambhapublication
New Gateway to Computer Science Book-9
Authors : Dinesh Adhikari, Dilendra Prasad Bhatt,
Shekhar Poudel, Laxman Adhikari
Layout Design : Ram Malakar
Video Content : Dinesh Adhikari
Language Editor : Krishna Prasad Regmi
Copyright © : Dinesh Adhikari
Edition : 2077
ISBN : 9789937579315
© : Publisher
No part of this book may be reproduced or transmitted by means (electronic, photocopying,
recording or otherwise) without prior written permission from the publisher. Any breach of this
condition will entail legal action and prosecution.
Printed in Nepal
Preface
It has become a fundamental right of children to get computer education. It is
very essential to get basic to advance knowledge about computer education to
compete the future. Nepal government has prescribed the syllabus and course
outline for the computer education from primary to secondary level. But
students are not able to get quality education due to the lack of systematic course
book and the computer system in the school. So we have developed the complete
series of computer science.
Along with the evolution of human beings new thoughts, area of knowledge and
technology also developed together. Among the eruptions, ICT (Information and
Communication Technology) is one which has unquestionably become important
part of human beings. A person is not better than a caged pigeon if s/he is far
from computer technology in this century. New Gateway to Computer Science is
a complete package which obviously supports a lot to the students as this is one
of the most useful textbook, so far available in the market.
This book is completely prepared considering the level of the students. This text has
various salient features like it focuses on child psychology, pictorial descriptions,
practical sections, let’s Review, sufficient exercise, etc.
It is impossible to acknowledge all who have directly or indirectly encouraged
me to prepare this book on this single page. My special thanks go to the students
and teachers of different schools for their regular interactions during the
preparation of this book.
Comments and constructive suggestions are highly welcomed from the readers
and professionals to update this text book.
Dinesh Adhikari
[email protected]
Content
Unit 1 FundamentalAspect ofcomputer..............................5-70
Lesson 1: Introduction to Computer and Its Applications areas.................6
Lesson 2: Types of Computer....................................................................15
Lesson 3: Computer System.....................................................................27
Lesson 4: Introduction to Computer Hardware........................................33
Lesson 5: Introduction to Computer Software.........................................56
Unit 2 Working with Graphics........................................73-101
Lesson 6: Introduction to Computer Graphics............................................74
Unit 3 Internet and Web Technologyi...........................102-177
Lesson 7: An introduction to Internet Technology....................................103
Lesson 8: Working with HTML................................................................112
Lesson 9: Working with CSS....................................................................149
Unit 4 Computer Programming....................................178-298
Lesson 10: General Concept of Programming.......................................179
Lesson 11: Programming Techiniques......................................................192
Lesson 12: Programming in QBASIC.....................................................209
Lesson 13: QBASIC Statements.............................................................223
Lesson 14: Program flow and Control Structures......................................235
Lesson 15: Library Functions in QBASIC................................................261
Lesson 16: Arrays in QBASIC..................................................................281
Program Writing Project ..................................................298
Specific Grid.....................................................................299
Practical Assessment........................................................300
Fundamental Aspects
of
Computer
Unit
1
This unit covers the following topics:
Lesson 1: Introduction to Computer and Its Applications areas
Lesson 2: Types of Computer
Lesson 3: Computer System
Lesson 4 Introduction to Computer Hardware
Lesson 5: Introduction to Computer software
Lesson Introduction to Computer and its
Applications Areas
1
Inside the Lesson
Introduction to computer
Defination of computer
Characteristics of computer
Advantages and disadvantages of computer
Working principles of computer
Applications area of computer
The word ‘computer’ comes from the word ‘compute’, which means, “to calculate”.
Hence, people usually consider a computer to be a calculation device that can perform
arithmetic and logical calculations at a very high speed.
Nowadays computers have become an integral part of our lives. They play a vital role in
everyone’s life; their importance is so amazing that without it we will not be able to live
the way we do. They are basic tool of human beings these days. Computers have changed
the way that people work. Computers can handle many tasks in business, education,
manufacturing and other so many fields. Computer is an electronic machine/device which
can input data, process them according to the instruction given and then give out the
meaningful information.
The data consists of numbers, text, sound, images, animations, and video.
The process converts numbers, text, sound, images, animations, and video (data) into
usable data, which is called information.
The information consists of numbers, text, sound, images, animations, and video that
has been converted by the process.
The data can be given using an input device.
The Central Processing Unit (CPU) converts data into information.
The information can be displayed by an output device.
A storage device is a device for storing data and information. A basic computer
consists of four components: an input device, a CPU, output devices, and memory.
6 New Gateway to Computer Science Book -9
What is a computer?
A computer is a programmable machine. It allows the user to store information and then
‘process’ that information, or data, with the help of instructions provided by the user. It is
also an electronic device that receives data from the input devices and processes the data,
to display the correct output which is always meaningful.
The computer is also called a data processor because it can store, process, and retrieve
data whenever needed. The activity of processing data using a computer is called data
processing. Data processing consists of capturing input data, manipulating the data, and
managing output results.
Characteristics of Computer
Speed
A computer can work very fast. It takes only few seconds for calculations but humans
take hours to complete their work. It can execute millions of instructions within Nano or
Pico second or even more than that. The speed that a CPU works at is measured in hertz
(Hz). Modern processors run so fast in term of gigahertz (GHz). One gigahertz is one
billion cycle per second. The following are the speed measurement units of computer.
Unit of Speed Parts of Second
1HZ (Hertz or 1×10O Hz) 1 Second (1×10O sec)
1KHZ (Kilo Hertz or 1×103 Hz) 1 Millisecond (1×10-3 sec)
1MHZ (Mega Hertz or 1×106 Hz) 1 Microsecond (1×10-6 sec)
1GHZ (Giga Hertz or 1×109 Hz) 1 Nanosecond (1×10-9 sec)
1THZ (Tera Hertz or 1×1012 Hz) 1 Picosecond (1×10-12 sec)
1PHZ (Peta Hertz or 1×1015 Hz) 1 Femtosecond (1×10-15 sec)
1EHZ (Exa Hertz or 1×1018 Hz) 1 Attosecond (1×10-18 sec)
1ZHZ (Zetta Hertz or 1×1021 Hz) 1 Zeptosecond (1×10-21 sec)
1YHZ (Yotta Hertz or 1×1024 Hz) 1 Yoctosecond (1×10-24 sec)
Accuracy
The accuracy of results computed by a computer is very high. Due to digital
techniques the error is very less. The errors in computing may be due to logical mistakes
by a programmer or due to inaccurate data. The degree of accuracy of computer is very
high and every calculation is performed with the same accuracy but the degree of its
accuracy depends upon its design. If the input data is incorrect, the output will be incorrect
which is called GIGO (Garbage in Garbage Out).
New Gateway to Computer Science Book -9 7
Diligence Let’s Review
A computer is always free from tiredness, lack of Characteristics of computer
concentration, weakness, etc. It can work for hours Speed
without creating any error. If millions of calculations Accuracy
are to be performed, a computer will perform every Diligence
calculation with the same accuracy. Versatility
Storage
Versatility No Intelligence
Computers are very versatile machine. They can
perform various activities like simple to complex. A
computer can perform completely different types of tasks. Computers are applicable in
each and every field like banking, business, education, entertainment, research and so on.
Storage
A computer has the power of storing more amounts of information or data. Any
information can be stored and recalled as per our requirement. A computer has a main
memory and auxiliary memory system. They can store large amount of data. With more
and more auxiliary storage devices, which are capable of storing huge amounts of data,
the storage capacity of a computer is virtually unlimited. The memory power of computer
depends fully upon how much data you want to store and when to lose or retrieve them
in a computer.
The following are the storage measure units of computer
Storage Unit Short Cut Bytes
1 Bytes 8 Bits
1 Kilobyte Bytes 1024 Bytes
1 Megabyte KB 1024 Kilobytes
1 Gigabyte MB 1024 Megabytes
1 Terabyte GB 1024 Gigabytes
1 Petabyte TB 1024 Terabytes
1 Exabyte PB 1024 Petabytes
1 Zetabyte EB 1024 Exabyte
1 Yottabyte ZB 1024 Zetabyte
1 Brontobyte YB 1024 Yottabyte
BB
No Intelligence
Computers do not have their own intelligence. They follow a set of instructions fed into
them by manufacturer. The user knows what to do and when to perform a specific task.
8 New Gateway to Computer Science Book -9
Advantages and Disadvantages of Computer
Advantages
The computers are always accurate and reliable with high storage capacity.
Computers are able to perform thousands of tasks within a short period of time.
Computers can be used to solve complex mathematical and logical operations.
Computers are versatile device, so that we can use it everywhere.
Computers are useful in communication among various users.
Computer never feels tired and boring but a human being does.
Disadvantages
A computer is a machine that has no intelligence to perform any task.
Commuter works according to the program and instructions given to it.
It is very risky to store data and information on the computer independently because
some electrical and electronic damages may damage the data.
Back up is so expensive that all the people are not able to purchase the computer.
We need dustless and temperature maintained environment to use the computer for
the best performance.
Skilled computer users are required to operate and maintain the computer system.
Working Principles of Computers
Let’s Review
Input: Inputs are the raw data given to the
computer for processing. The computer accepts The basic working principles of the
data from the user with the help of input devices computer are:
like keyboard, mouse, light pen, microphone, Receive input through various
etc. input devices.
Process: The computer processes the data Process information to perform
when it gets input from the user. The processing arithmetic or logical operations.
activity of computer is done by the Central Produce output with the help of
output devices.
Processing Unit (CPU) of the computer. Store information on the storage
devices.
Output: The output is always meaningful. The
output devices of the computer like monitor,
printer, speaker, etc. can display meaningful
information. The output devices can display the output only after processing.
Storage: This is done after displaying the information. When the result is final, we can use
storage devices for data storage. There are some primary and secondary memories with
the computer system. Generally, we use secondary memories to store data permanently.
New Gateway to Computer Science Book -9 9
ApplicationAreas of Computer
Computer in Education
Computers are commonly used in school and college for teaching and learning activities. A
teacher can make his teaching techniques easier and interactive with the help of computer
tools. Students can also use computer as their learning tools. They can search various
topics on the internet. Teachers also can take help of the internet to do research work so
that they can collect lots of ideas and information about learning process. A teacher can
prepare a slide and demonstrate it in the class. Students also can do research work in their
various subjects that they require. Computer Based Learning (CBL) and Internet Based
Learning (IBL) are more popular these days. Because of the use of computer online and
distance learning is also possible and has been implemented in our education system.
Computer in Bank
Computers are massively used in bank these days. With
the help of computers, we can keep records of customers;
we can calculate the money; check the balance, verify the
signature, deposit and withdraw money. Online banking,
mobile banking, ATM card, Electronic Fund Transfer
system are also available because of the use of computer
at bank.
Computer for Entertainment
Entertainment is also an important part of human life.
Computers are used for listening to music, watching videos
and films, play games, online booking of film tickets,
downloading music and videos, etc. So computers play a
major role in the sector of entertainment.
Computer at Hospital
Hospitals use computers to keep the records of patients,
doctors and staff. These days, computers are used to
keep and display the duty roster of doctors. Computers
are used to check the various internal organs of human
so that it is easy to find out the health problems. X-Ray
, CT-Scan, test of heart, test of kidney, endoscopy,
ultrasound, etc. are possible to do within a second with the
10 New Gateway to Computer Science Book -9
help of computer. Computers are used in different medical units of hospital such as
ECG (Electro Cardiograph), ICU ( Intensive Care Unit), OT (Operation Theater), CAS
( Computer Aided Surgery), diagnosis of diseses, etc. So there is a great role of computer
in the medical science.
Computer in Science and Technology
Science and technology is responsible for many changes in
our lives, how we live, how we communicate and what we
can learn about the world. But some of the most profound
effects of technology are hard to articulate, or even notice.
Computers are used in all branches of science and technology.
It is almost impossible to conduct research in science and
technology without the use of computer.
Computer in Communication
Whether communication is to be internal or external, it is
important in the life of every individual. Computers can play
a significant role in communication with the use of email, fax,
videoconferencing and many more. The information cannot
be delivered to any other without the use of computer and
computing tools these days. The following are the major areas
of communication where computers are used.
Social Networking
Social networking sites like Facebook, Twitter and LinkedIn allow users to rapidly
generate content for people in their network to view. Rather than sending individual notes,
social networking provides us with a constant stream of updates and information. These
tools have taken communication a step further than email due to their ability to instantly
communicate life and status updates to an entire network of people who can respond and
comment in real time.
VOIP and Video Chat
Voice-Over-Internet-Protocol has replaced the need for
landline telephones. These lines can provide us with instant
phone communication over the Internet, and are cheaper than
fixed phone lines. They also provide us with the ability to
conduct video chats to see whom you are speaking with. VOIP
platforms also store contact details for easy accessibility and
dialling.
New Gateway to Computer Science Book -9 11
Internet and Email
The World Wide Web, Internet and Email have revolutionized the way individuals
communicate with each other. Rather than waiting days or weeks to see information,
we can now view all information at the speed of light. Email has fundamentally
transformed how people share information based on the speed and flexibility it offers.
Computers can process data at approximately 20 million bytes per second so it is easy to
download and display the text email.
Routers
Routers are the types of computers used to direct communication traffic. They are crucial
to the efficient and correct distribution of calls, emails or other internet traffic. Routers take
“packets” of electronic data and send them in the direction to connect with the intended
person. They can be used at home but are also held in central data warehouses where hubs
of traffic are routed in the same place.
Let’s Review
The following are the modern application areas of computer.
computer in education
computer in bank
computer for entertainment
computer at hospital
computer in science and technology
computer in communication such as social networking, video chat, internet and
email.
Expand your knowledge
What is a smart card?
A smart card looks like an ATM card or credit card in size and shape, but instead of a
magnetic strip it contains an embedded microprocessor and memory.
What can internet banking do?
transfer money from one account to another.
pay bills now or schedule for future payments.
check account balance and transaction history.
access previous account statements.
request cheque books.
change personal identification number.
view currency exchange and interest rates.
apply for credit cards and various types of loans
12 New Gateway to Computer Science Book -9
Assignment
1. Select the correct answer from the given options.
a. What is the unit of time for one trillionth of a second?
i. Picosecond ii. Nanosecond iii. Millisecond iv. Femtosecond
b. If a computer can store data of 1024 gigabytes, what is the storage unit for this?
i. 1 Petabyte ii. 1 Terabyte iii. 1 Gigabyte iv. 1 Megabyte
c. What is the act of entering raw data to the computer?
i. Process ii. Output iii. Storage iv. Input
d. Which of the following is the best example of social networking?
i. Facebook ii. Gmail iii. Web site iv. Search
e. In which application area does CBL, IBL lie?
i. Science ii. Communication iii. Education iv. Entertainment
2. Fill in the blanks with suitable words.
a. The word ‘computer’ comes from the word which means, “to …………………”.
b. Computer is an electronic machine which can input data, process them and then
give out the …………………
c. The speed that a CPU works at is measured in ………………………
d. The errors in computing may be due to ……………. mistakes by a programmer
or due to inaccurate data.
e. A computer has a main memory and ……………………. memory system to store
large amount of data.
f. The ………………. produced by the computer is always meaningful.
g. Hospitals use computers to keep the records of ………… , ……………. and staff.
h. ………………….has replaced the need for landline telephones in many instances.
3. State whether the given statements are true or false.
a. The computer is called a data processor because it can store, process, and retrieve
data whenever needed.
b. Modern processors run so fast in term of megahertz (MHz).
c. If millions of calculations are to be performed, a computer will perform every
calculation with the same accuracy.
d. It is very safe to store data and information on the computer independently.
e. If some electrical or electronic damages occur, there are no any chances of data loss
or damage.
f. The output devices of the computer like monitor, printer, speaker, etc. can store
meaningful information.
g. The input devices can display the output after processing.
h. Students can also use computer as their learning tools.
New Gateway to Computer Science Book -9 13
i. A teacher can prepare a slide and demonstrate it in the class with the help of
computer.
j. Computers are used to check various internal organs of human to find out the
health problems.
4. Write appropriate technical terms for the followings.
a. An electronic device which can input data, process them according to the
instruction given and then give out meaningful information.
b. The computer unit that converts the data into information.
c. A collection of four bits or half byte.
d. The result obtained after the data processing.
e. It takes "packets" of electronic data and sends them in the direction to connect
with the intended person.
f. It is the raw facts used in computers.
g. A speed measurement unit which is ten trillionth of a second.
h. A storage unit that is equal to 1024 terabytes.
5. Write the full form of the followings.
CPU, GHz, CBL, IBL, GIGO, ECG, OT, CAS, ICU, VOIP
6. Match the following:
One terabyte One millionth of a second
Microsecond 1024 Gigabyte
CBL, IBL Social Networking
Facebook, Twitter can be used everywhere
Versatile computer in education
7. Answer the following questions.
a. Why are computers important these days? Write in short.
b. Define computer with its two advantages and disadvantages.
c. What are the characteristics of a computer? List out them.
d. What are the various speed measurement units of the computer?
e. List out the storage measurement units of a computer.
f. Why is the computer called a versatile machine?
g. Write down the working principals of the computer.
h. What are the major application areas of the computer? List out them.
i. What is the role of the computer in education sector?
j. What is the role of the computer in health and communication sector?
Project Work
• Conduct a speech competition on the topic ‘Role of computer in education and
communication'.
• Divide a class in various groups and conduct a presentation on the following topics.
i. Characteristics of a computer
ii. Major application areas of a computer
iii. The communication mechanism of the 21st century.
14 New Gateway to Computer Science Book -9
Lesson
2 Types of Computer
Inside the Lesson
Introduction to computers types
Types of computer on the basis of work/ function
Types of computer on the basis of size
Types of computer on the basis of brand
Types of computer on the basis of model
There are different types of computers available these days. The function of each type of
computer is to process the data and provide the users with output. However, the methods
used by these computers to process and handle the data may be different. Generally,
there are two types of computer they are general purpose computer and special purpose
computer. A general purpose computer can perform any kind of jobs with equal efficiency
simply by changing the application program stored in its main memory. A special purpose
computer is designed to perform only one special task. The program or instructions set is
permanently stored in special purpose computers.
Computers are broadly classified into the following four groups such as; on the basis of
work/function, size, brand, and model. Let’s discuss them in detail.
Types of Computer on the Basis of Work/ Function
Analog Computer
An analog computer is that computer, which is used to process
continuous data.These computers are very fast in their operation and
allow several other operations to be carried out at the same time.
However, the results produced by these computers are not accurate.
Analog computers can be used in scientific and industrial applications
such as measure the electrical current, frequency and resistance of
capacitor, etc. They perform arithmetical operation by measurable
quantities, such as mechanical movement, the rotation of gears rather
than by number. In analog computers, data are transmitted for their operation in the form
New Gateway to Computer Science Book -9 15
of continuous signals, while in digital computers in the form discrete signals. Examples
of analog computers are Thermometer, Pressure measurement device, speedometer,
frequency of signal and voltage.
Some features of analog computers are listed below.
It is specific to particular task so we cannot use it for multiple applications.
It works on continuous data and gives continuous output.
It works on real time and has no storage capacity.
It gives output in the form of graph, signals, table, etc.
Digital Computer
The digital computer is also known as the digital
information processing system. It is a type of computer that stores
and processes data in the digital form. Therefore, each type of
data are usually stored in these computers in the terms of 0 and
1. The output produced by these computers is also in the digital
form. The digital computers are also capable of processing the
analog data. However, the analog data should be first converted
to the digital form, before being processed by these computers.
Similarly, if we want the output in the analog form, the digital information produced
by these computers should be first converted to an analog form. These conversations
are generally carried out by the in-built components of digital computers. The different
hardware components of a digital computer are an Arithmetic- Logic Unit, a Control Unit
(CU), a memory unit and I/O units. IBM PC, Apple/Macintosh, etc. are the examples of
digital computers.
Some features of digital computers are listed below.
It works on discontinuous or discrete data.
It is applicable for general purpose.
It is based on the digits 0 and 1.
It is faster and it has storage section.
It is highly accurate and reliable than analog system.
Hybrid Computer
A hybrid computer combines features of both analog and digital
computers. In this computer, some calculations are done in the analog
portion and some are done in the digital portion of the computer. The
hardware components of hybrid computers are usually the mixture
16 New Gateway to Computer Science Book -9
of analog and digital components. These features make the hybrid computers very fast,
efficient and reliable. In these computers, data are generally measured and processed
in the form of electrical signals and are stored with the help of digital components. For
example in hospital, analog devices measure patient’s heart function, temperature and
other vital signs. These measurements are converted into numbers and supplied to a digital
component in the system. This component is used to monitor the patient’s vital signs and
to send an immediate signal to the nursing station if any abnormal readings are detected.
Some features of digital computers are listed below.
It is expensive system
It is designed for special purpose so it is not so versatile.
It works on discrete and continuous value.
It has limited storage.
It is more complex than other computer system.
Let’s Review
Generally there are two types of computer they are general purpose computer and
special purpose computer.
An analog computer is that computer, which is used to process continuous data.
The digital computer is also known as the digital information processing system.
The hardware components of hybrid computers are usually the mixture of analog
and digital components.
Types of Computer on the Basis of Size
Supercomputer
A super computer is the fastest type of computer that can
perform complex operations at a very high speed. It is the
most powerful computer in terms of performance and data
processing. It is specialized and task specific computer
used by large organizations. The super computers were first
presented in the year 1960AD by Seymour Cray at Control
Data Corporation (CDC). These computers are used in
research and for exploration purposes. The supercomputers
are very expensive and very large in size. It can be accommodated in large air-conditioned
rooms; some super computers can span an entire building. Some popular supercomputers
are IBM’s Sequoia, Fujitsu’s K, IBM’s Mira, IBM’s Super MUC, NUDT Tianhe-1A,
CRAY-3, Cyber 205, NEX SX-3, PARAM, etc.
New Gateway to Computer Science Book -9 17
The uses of supercomputers are listed below.
Space exploration
Earthquake studies
Animated graphics
Weather forecasting
Nuclear weapons testing and energy research
Petroleum exploration
Minicomputer
A minicomputer was first introduced in the year 1960 AD by
Digital Equipment Corporation (DEC). They were called mini
computers because they were smaller than the other computers
of those times. Minicomputers are used by small businesses and
firms. Minicomputers are also called “Midrange Computers”.
These computers are not designed for a single user. Individual
departments of a large company or organizations use mincomputers for specific purposes.
Mini computers can also be used as the web servers that can handle thousands of
transactions in a day. These computers are less expensive than mainframe computers. The
popular minicomputers are K-202, Texas Instrument TI-990, SDS-92, IBM 8000 Series,
PDP 11, VAX-7500, etc.
Mainframe Computer
A mainframe computer is a very large computer that is employed
by large business organizations for handling major applications
such as financial transactions, Enterprise Resource Planning
(ERP), industry and consumer statistics, census, etc. Mainframe
computers are not as powerful as supercomputers, but they are quite
expensive. Many large firms and government organizations use
mainframe computers to run their business operations. The Mainframe computers can be
accommodated in large air-conditioned rooms because of their size. As super-computers
are the fastest computers with large data storage capacity, Mainframe computers can also
process and store large amount of data. Banks, educational institutions and insurance
companies use mainframe computers to store data. Example of mainframe computers are
IBM 3000, VAX 8000 and CDC 66000, Fujitsu’s ICL VME, Hitachi’s Z800, etc.
Some of the special features of mainframe computers are as follows:
The capacity of RAM of these computers lies between 128 MB and 8 GB.
They can handle huge amount of I/O operations at the same time.
18 New Gateway to Computer Science Book -9
They have different cabinets for primary storage, secondary storage and input
/ output units.
A typical mainframe computer has a maximum 16 microprocessors. However,
some modern mainframe computers can have more than this.
They are able to run multiple operating systems, so it is also called ‘virtual machines’.
Let’s Review
A supercomputer is the most powerful computer in terms of performance and
data processing.
Minicomputers are also called “Midrange Computers”.
A mainframe computer is a very large computer that is used by the large
business organizations.
Many large firms and government organizations use mainframe computers to
run their business operations.
Microcomputer
A microcomputer is a small and cheap digital computer that is
designed to be used by individuals. Desktop computers, laptops,
personal digital assistant (PDA), tablets and smartphones are
the types of microcomputers. The micro-computers are widely
used and the fastest growing computers. These computers
are the cheapest among the other types of computers. The
micro-computers are specially designed for general use. Microcomputers also include
several software programs such as operating system, system software and utility software.
The popular microcomputer manufacturing companies are IBM, Dell, Apple, Samsung,
Son, Toshiba, etc.
Types of Microcomputers
Desktop Computer
The desktop computer systems are designed to be used by
an individual at a single place. The desktop computer uses
keyboard, mouse, monitor, hard disk, peripheral devices and
system unit. These computers are very cheap and an individual
can easily purchase them for home or business use. The different
manufactures of desktop computers are Apple, IBM, Hewlett-
Packard(HP), etc.
New Gateway to Computer Science Book -9 19
Laptop Computer
Laptop computer is a portable computer that can be taken
from one place to another at any time very easily. It is also
known as notebook, notepad or mobile computer. The
laptop computer is a small size computer that incorporates
all the features of a desktop computer. These computers are
provided with a rechargeable battery that removes the need of continuous external power
supply. However, these computer systems are more expensive than desktop computers.
Different manufactures of laptop computers are Acer, Apple, Sony, HP, DEL, TOSHIBA, etc.
Hand-Held Computer
Hand-held computer is also known as Personal Digital Assistant (PDA), converged
device, palmtop or mobile device. It is a very small sized computer that can be kept in
pocket. It has a small display screen and it uses input device like an electronic stylus or
finger. The storage capacity of hand-held computers is not very large. They generally use
small cards to store data and programs instead of disk drives. Therefore, they are less
powerful as compared to the desktop and laptop computers. Different examples of hand-
held computers are Apple Newton, Casio Cassiopeia, Franklin eBook Man, Samsung, etc.
Let’s Review
A microcomputer is a small and cheap digital computer that is designed to be
used by individuals.
The desktop computer systems are designed to be used by an individual at a
single place.
Laptop computer is also known as notebook, notepad or mobile computer.
The hand-held computer is a very small sized computer that can be kept in pocket.
Types of Computer on the Basis of Brand
There are three types of computers on the basis of brand which are explained below.
IBM PC
The computers that are manufactured by IBM (International
Business Machine) are IBM PC. It is one of the leading companies
of the world manufacturing computers. IBM was established in 1924
and started manufacturing mainframe, mini and microcomputer
from 1945 onwards. IBM PC is the brand name of the first popular
20 New Gateway to Computer Science Book -9
commercial PC that was developed by the IBM corporation. In 1981, the IBM PC was
launched with the model number IBM 5150. These computers are more reliable, durable
and have better quality. IBM PC was one of the fastest desktop computers of its time. It
directly competed with the Commodore Personal Electronic Transistor (PET), Apple II
and Control Program/Monitor (CP/M). The IBM PC was equipped with an Intel 8088
processor at a speed of 4.77 MHz, 16 KB of memory extendable to 256 KB, a 160 K
floppy drive and an optional CRT colour monitor.
IBM Compatibles
The computers that are manufactured by the other computer
manufacturing companies but have the same technology and
features are known as IBM Compatibles computers. The term
compatible means “Able to exist together and work successfully”.
IBM compatible computer system is assembled form of different components developed
by different companies. It is based on IBM principle that can use standard hardware and
software designed for the IBM PC and its own additional features. Some IBM compatible
computers are AST, ALR, Sherry, etc.
Differences between IBM PC and IBM Compatible
IBM PC IBM Compatible
The computers designed as well as The computers which are designed by IBM
developed by IBM corporation are called but manufactured by companies other than
IBM PC. IBM are called IBM compatibles.
It is known as original or branded IBM. It is called assembled or duplicate IBM.
It is expensive but more reliable than It is cheaper but less reliable than IBM PC.
IBM Compatible.
It is usually used by large organization It is usually used by small organization and
which requires high security. higher security is not required.
Examples:- IBM Desktop, IBM 1401, Examples:- HP laptop, Dell notebooks, etc.
IBM laptop, etc.
Apple Macintosh
The computers that are manufactured by Apple Company
but have different architecture and configuration than
IBM Compatibles are known as Apple Macintosh. Apple
Macintosh computers were introduced by Steve Jobs and
Steve Wozniak of Apple Inc. on January 24, 1984. The first
computer was called Mac 128K. This computer has its own operating system which is
called Mac OS.
New Gateway to Computer Science Book -9 21
Types of Computer on the Basis of Model
There are three types of computers on the basis of model which we are going to discuss
below.
XT Computers (Extended Technology)
The computers having 8086 or 8088 microprocessor and processing speed of 4.77 MHz
are known as XT Computers. These computers are out-dated now because they cannot run
on latest software versions.
AT Computers (Advanced Technology)
The computers having 80286 or later versions of microprocessors are known as AT
computers. Their storage capacity as well as speed is much higher than XT computers.
Besides that they have math co-processor to support main processors to perform complex
mathematical calculations.
PS/2 Computers (Personal System 2)
IBM developed another model of computer in 1990 that have more advanced architecture
design than AT computers. They are known as PS/2 computers. They are more faster than
AT computers. Most of the laptop computers based on PS/2 model use OS/2 or UNIX
operating system and 1.44 MB floppy diskette.
Let’s Review
The computers that are manufactured by IBM are IBM PC.
The term compatible means “Able to exist together and work successfully”.
Apple Macintosh computers were introduced by Steve Jobs and Steve Wozniak of
Apple Inc. on January 24, 1984.
The three types of computer on the basis of model are XT, AT and PS/2.
Expand your knowledge
Kathmandu University has installed the first supercomputer at IT Park, Banepa.
The supercomputer which consists of high performance computing (HPC) servers
was donated by CERN based in Switzerland.
There are so many Super Computers spread in almost every country in the World.
The maximum numbers of Super Computers are owned by the United States and
China.
The first desktop hybrid computing system was the Hycomp 250, released by
Packard Bell in 1961 AD.
22 New Gateway to Computer Science Book -9
Assignment
1. Select the correct answer from the given options.
a. A computer that is used to process continuous data.
i. Analog computer ii. Digital computer iii. Super computer iv. Hybrid computer
b. Which computer is also called a digital information processing system?
i. Digital computer ii. Analog computer iii. Hybrid computer iv. None of them
c. Which of the following computer has the features of both analog and digital
computer?
i. Micro Computer ii. Mainframe computer
iii. Hybrid Computer iv. Super computer
d. Which of the following computer has complex system?
i. Hybrid computer ii. IBM computer
iii. Mainframe computer iv. Analog computer
e. Which of the following is mainframe computer?
i. IBM 3000 ii. Cyber 205 iii. IBM PC iv. All of them
f. In which computer does the capacity of RAM lie between 128 MB and 8 GB?
i. Micro computer ii. Mainframe Computer
iii. Super Computer iv. None of them
g. Which of the following is micro computer?
i. Apple and IBM ii. CDC 66000 iii. PDP 11 iv. VAX-7500
h. Which of the following is extended technology computer?
i. Having 8086 or 8088 Processor ii. Later version having 80286
iii. With windows 8 OS iv. None of them
2. Fill in the blanks with suitable words.
a. …………computer is that computer, which is used to process continuous data.
b. In …………….. computers, data are transmitted for their operation in the form of
continuous signals.
New Gateway to Computer Science Book -9 23
c. Digital computers transmitt data and operation in the form of ………………
signals.
d. The hardware components of ………… computers are usually the mixture of
analog and digital components.
e. ……………… are also called “Midrange Computers”.
f. The…………… computer systems are designed to be used by an individual at a
single place.
g. The term compatible means “……………………….”.
h. The three types of computer on the basis of model are XT, …………… and PS/2.
i. The computers having …………. or later versions of microprocessors are known
as AT Computers.
3. State whether the given statements are true or false.
a. Generally there are two types of computer. They are general purpose computer and
special purpose computer.
b. Digital computer performs arithmetical operation by measurable quantities, such
as mechanical movement, the rotation of gears rather than by number.
c. The hybrid computer is also known as the digital information processing system.
d. Supercomputers are the most powerful computers in terms of performance and
data processing.
e. A mainframe computer is a very large computer that is employed by large business
organizations.
f. A supercomputer is a small and cheap digital computer that is designed to be used
by the individuals.
g. Desktop computer is also known as notebook, notepad or mobile computer.
h. The supercomputer is a very small sized computer that can be kept in pocket.
i. The computers that are manufactured by IBM (International Business Machine)
are IBM PC.
j. The computers having 8086 or 8088 microprocessor are known as XT Computers.
24 New Gateway to Computer Science Book -9
4. Write appropriate technical terms for the followings.
a. A program that is designed to perform only one special task.
b. A computer which is used to process the continuous data.
c. The computer that can process analog data but the analog data should be first
converted to the digital form.
d. The computer that has the features of both analog and digital computer.
e. The computer which is also called a digital information processing system.
f. The computers that are able to run multiple OS and called virtual machines.
g. It is a computer which is known as PDA.
h. The computer systems that are designed to be used by an individual at a single
place.
i. The computers that are manufactured by other computer manufacturing companies
having same technology and features.
j. The computers having 80286 or later version of microprocessors.
5. Write the full form of the followings.
IBM-PC, CDC, DEC , ERP, PDA, CP/M, PET, XT, AT, PS/2
6. Match the following:
Apple / Macintosh Computer IBM compatibles
CRAY- 3 Hand-held computer
VAX 8000 Digital computer
Apple Newton Supercomputer
AST, ALR Minicomputer
PDP 11 Mainframe computer
7. Answer the following questions.
a. What are general purpose and special purpose computers?
b. What are the types of computer on the basis of work?
c. Define analog and digital computer.
d. What are the features of hybrid computer?
New Gateway to Computer Science Book -9 25
e. Write any two features of analog and digital computer.
f. What are the types of computer on the basis of size?
g. What are the uses of supercomputers? List out them.
h. What is minicomputer and mainframe computer?
i. Mention any two features of mainframe computer.
j. What are the various types of microcomputer? List out them.
k. What is microcomputer? Name some popular microcomputer manufacturing
companies.
l. Write at least two examples of super, mainframe, and minicomputer.
m. Write down the differences between IBM PC and IBM compatible computers.
n. List out the types of computers on the basis of model.
Project Work
• Divide a class in various groups and conduct a presentation on the following topics.
i. Types of computer on the basis of work
ii. Types of computer on the basis of size
iii. Types of computer on the basis of model and brand
26 New Gateway to Computer Science Book -9
Lesson
3 Computer System
Inside the Lesson
Introduction to computer system
Understanding computer hardware
Understanding computer software
Introduction to data and information
Understanding users
A computer is the collection of parts, which are categorized on the basis of work that they
do. A computer is a system, an interrelated combination of components that performs the
basic system functions of input, processing, output, storage, and control, with a powerful
information processing tool. Computer systems include any software and peripheral
devices that are necessary to make the computer function. A computer system allows
users to input, manipulate and store data. Computer systems typically include a computer,
monitor, keyboard, mouse and other components. Without the programs, the computer
would not know how to process data that enters the system, and the data might be
discarded. It is very flexible, as it can process any task by loading a program from storage.
Computer systems can work by themselves or access other devices that are external or
connected with other computer systems.The major components of computer system are
explained below.
Understanding Computer Hardware
Computer hardware consists of the components that can be physically handled.
It refers to the physical units or machine of functional units, which makes up
the computer configuration. The function of these components is typically
divided into three main categories: input, output, and storage. Hardware may be classified
into Central Processing Units (CPU) and the peripherals. The CPU has Control Unit (CU),
Arithmetic and Logic Unit (ALU) and the Internal Memory Unit (IMU) or main memory.
The peripherals consist of the input, output and auxiliary storage units. Computer is made
up of five distinct elements which are explained below.
New Gateway to Computer Science Book -9 27
Central Processing Unit Let’s Review
This is the brain of the computer that A computer system allows users to input,
accepts data, performs operations manipulate and store data.
on the data and sends out the result.
Information from an input device Computer hardware refers to the physical
or from the computer’s memory is units or machine of functional units, which
communicated through the bus to makes up the computer configuration.
the Central Processing Unit (CPU),
which is the part of the computer that CPU is also known as the brain of the any
translates commands and runs computer system.
programs. It consists of ALU
(Arithmetic Logic Unit), CU (Control The arithmetic operation can be addition,
Unit) and MU (Memory Unit). The subtraction, multiplication and division.
CPU makes the use of the following
memory sub systems for carrying Control unit maintains the sequence of
operations being performed by the CPU.
out its processing operations.
The main memory is also responsible for
holding instructions between CPU and
theI/O devices.
Arithmetic Logic Unit (ALU)
The ALU is the part of the CPU that performs arithmetic operations on the data. The
arithmetic operation can be addition, subtraction, multiplication and division. The
multiplication and division operations are usually implemented by the arithmetic unit as
the repetitive process of addition and subtraction operation respectively.
Control Unit (CU)
The control unit is an important component of CPU that controls the flow of data
and information. It maintains the sequence of operations being performed by the CPU.
It fetches an instruction from the storage area, decodes the instruction and transmits the
corresponding signals to the ALU and the storage registers. Control unit guides ALU
about the operations that are to be performed and also suggests the input and output
devices to which data are to be communicated.
Memory Unit (MU)
The memory unit is referred to as the internal memory of primary memory of the computer.
It is also known as Random Access Memory (RAM). It is a temporary storage location
that holds the data only for a short period of time. Once the computer is switched off, the
data stored in the RAM gets erased. The memory space of RAM is limited and therefore
all the files cannot be stored in it. The memory space available in RAM also affects the
speed of a computer system. If the memory space is more, more number of instructions
can be copied and executed at the same time. The main memory is also responsible for
holding instructions between CPU and the I/O devices.
28 New Gateway to Computer Science Book -9
Input Unit
Input unit consists of external devices that are; components outside the
computer system. It provides information and instructions to the computer.
The devices like keyboard, mouse, light pen, joystick, scanner, microphones, Optical
Character Reader (OCR), Magnetic Ink Character Reader Recognition (MICR), bar code
reader, digitizer, touch screen and optical mark reader (OMR) are mostly used input units
of computer.
Output Unit
An output unit consists of hardware that transfers information from the
computer’s CPU to the computer user. This includes the monitor, printer, plotter
or speaker. The output unit is used to present soft and hard copy of information.
The VDU (Visual Display Unit) or monitor and printer are common output units.
There are many categories of display units available for computer. The LED
(Light Emitting Diode), LCD (Liquid Crystal Display), DVST (Direct View Storage
Tube), etc. are text and graphics display output units.
Storage Unit
Storage units provide permanent storage of information and programs for retrieval to
the computer. Storage units are one of the core components of any computing device.
They store virtually all the data and applications on a computer.The two main types of
storage units are disk drives and memory. There are several types of disk drives like hard
disk drive, floppy disk, magneto-optical, and compact disk for data storage.
Understanding Computer Software
Software is a set of instructions that tells the computer what to do and when to do it.
The computer uses this instruction to manipulate data, and enhance the proper
functioning of the hardware components. It is designed to provide the potential capabilities
of the hardware to the user. It converts data into information and allows users to use
the computer in different ways. Computer programs are written by human beings.
The person who writes a program also decides on its functionality and behaviour. Software
also governs how the hardware is utilized; for example, how information is retrieved
from a storage device. The interaction between the input and output devices is controlled
by software which is called the Basic Input Output System (BIOS) software. Software
as a whole can be divided into a number of categories based on the types of work done
by programs. The two primary software categories are system software, and application
software.
New Gateway to Computer Science Book -9 29
Data and Information
Data are the facts or details from which information is derived. Data are raw, unorganized
facts that need to be processed. When data are processed, organized, structured or
presented in a given context so as to make them useful, it is called information. Some
differences between data and information are presented in the given table.
Data Information
Data are used as input for the computer Information is the output of data.
system.
Data are unprocessed facts figures. Information is processed data.
Data don’t depend on Information. Information depends on data.
Data are not specific. Information is specific.
Data don’t carry a meaning. Information must carry a logical meaning.
Data are the raw material. Information is the product.
Understanding Users
People who are the computer operators are also known as users. A user is a person
who uses a computer or computing devices. The most majority of computer users are
application oriented. They have traing and experence with some computer basis sofware.
They understand the general concept of computer such as files and folder management,
storing, saving and editing the documents and so on. The person who uses the software
or hardware after it has been fully developed, marketed and installed are called the End
user. The term 'user' and 'end user' is the same thing. End users are seprate group from the
installer or administrators of the product. End users are usually support staff, management
professionals, data processing staff and end-user support personnel. We can say that end
users are not trained programming professionals.
Let’s Review
Input unit provides or fetches information and instructions to the computer.
An output unit consists of hardware that transfers information from the computer’s
CPU to the computer user.
Storage units provide permanent storage of information and programs for
retrieval to the computer.
Computer programs are written by human beings.
The interaction between the input and output devices is controlled by software
called the Basic Input Output System (BIOS) Software.
Data are the facts or details from which information is derived.
Information is processed data.
30 New Gateway to Computer Science Book -9
Expand your knowledge
In 1936, the Russians made a computer that ran on water.
ENIAC was the first electronic computer, which weighed around 27 tons and has
taken up about 1800 square feet of space.
The first microprocessor 4004 which literally set the path for the modern
computing era was developed by Intel.
The world’s first commercial water-cooled PC was Apple’s Power Mac G5.
Intel 4004 was the first commercially available microprocessor with a maximum
clock rate of 740 kHz.
Assignment
1. Select the correct answer from the given options.
a. Which of the following is related to computer hardware?
i. Windows OS ii. Output devices iii. Software programs iv. Device driver
b. Which of the following is memory unit?
i. RAM ii. Motherboard iii. Power supply iv. Input devices
c. Which of the following is input unit?
i. OCR ii. MICR iii. OMR iv. All of them
d. Which of the following section is used to perform arithmetic and logical
calculations?
i. CU ii. MU iii. ALU iv. None of them
e. Which of the following is a permanent storage unit?
i. RAM ii. Hard drive iii. Input units iv. Output unit
2. Fill in the blanks with suitable words.
a. A ……………….. allows users to input, manipulate and store data.
b. CPU is also known as the ………………. of the any computer system.
c. ……… unit maintains the sequence of operations being performed by the CPU.
d. An ……………… unit consists of hardware that transfers information from the
computer’s CPU to the computer user.
e. ……………… are the facts or details from which information is derived.
f. ………………… is processed data.
3. State whether the given statements are true or false.
a. Computer software refers to the physical units or machine of functional units,
which makes up the computer configuration.
New Gateway to Computer Science Book -9 31
b. The logical operation can be addition, subtraction, multiplication and division.
c. The main memory is also responsible for holding instructions between CPU and
the I/O devices.
d. Output unit provides or fetches information and instructions to the computer.
e. Computer programs are written by human beings.
f. The interaction between the input and output devices is controlled by software
called BIOS Software.
4. Write appropriate technical terms for the followings:
a. It consists of the components that can be physically handled.
b. It consists of the input, output and auxiliary storage units.
c. It is the part of the CPU that performs arithmetic operations on the data.
d. It fetches an instruction from the storage area, decodes the instruction and
transmits the corresponding signals to the ALU and the storage registers.
e. It is a temporary storage location that holds the data only for a short period
of time.
f. The computer unit that consists of hardware that transfers information from the
computer’s CPU to the computer user.
g. It is a set of instructions that tells the computer what to do and when to do it.
h. It is a raw, unorganized facts that need to be processed.
5. Write the full form of the followings.
ALU, IMU, RAM , OCR, MICR, OMR, DVST, VDU, LCD, LED, BIOS
6. Match the following.
MICR Section of CPU
BIOS RAM
ALU Input Unit
LED Related to software
7. Answer the following questions.
a. Define computer system with its few components.
b. Define computer hardware with some examples.
c. What are the sections of CPU that are used in processing operations?
d. Define ALU and control unit.
e. What do you mean by 'input' and 'output' unit?
f. What is the function of storage unit?
g. Write any four differences between data and information.
Project Work
• Prepare a report about computer system and explain its units.
32 New Gateway to Computer Science Book -9
Lesson
4 Introduction to Computer Hardware
Inside the Lesson
Introduction to computer hardware
Understanding about motherboard with its components
Understanding about microprocessor with its function
Understanding about memory
Primary memory
Cache memory
Secondary memory
Types of secondary memory
Magnetic storage devices and their types
Optical storage devices and their types
Units of memory measurement
Input devices and their types
Output devices and their types
Computer hardware is the collection of physical components that make a
computer system. A computer has mainly two types of hardware they are internal hardware
and external hardware. Computer hardware is the component of a computer, such as the
monitor, mouse, keyboard, computer data storage, hard disk drive (HDD), graphic cards,
sound cards, memory, motherboard, and so on. All of them are physical objects that are
tangible. Here we are going to discuss various types of internal and external hardware.
Understanding Motherboard
The motherboard is an internal computer hardware. It is a body of the computer, through
which all other components interface. The motherboard is essential to the computer as
it provides the computer with main computing capability. It is the printed circuit board
making up a complex electronic system. It provides electrical connections through
which other components of the system communicate. The mother board includes
many components such as CPU, RAM, firmware, and internal and external buses.The
New Gateway to Computer Science Book -9 33
motherboard connects other components through the
use of traces, or electrical pathways such as video cards,
sound cards,disk controller, etc. Personal computers
normally have one CPU on the motherboard. Let’s discuss
some of the components of the motherboard.
CPU Socket
CPU socket helps to install the processor into the motherboard. That means the CPU
connects the socket for connecting motherboard. On the bottom of the motherboard, the
socket carries hundreds of metalconnectors for the metal pins or balls. It helps to supply
power to the processor.
Input and Output Ports
Input and output ports are placed at the back side of computer chassis. In particular, the
I/O ports are built to connect the monitor, speakers, a microphone, an ethernet networking
cable and multiple USB devices.
Expansion Card Slots
When you need to add new components to the motherboard or if you want to update any
parts of the motherboard, a motherboard’s expansion card can be used. An expansion card
slots helps to add external devices to display.
RAM (Memory) Slots
To install the RAM a motherboard has more than one slots and it is positioned near
the CPU socket. In general, RAM is the most needed part of the motherboard. It is the
temporary memory of the computer, but it helps to run the applications and opening
the files. Particularly, if the processors have a large amount of RAM, it can operate the
computer more smoothly and it helps to increase the performance of the computer.
Power Connectors
A Motherboard needs power to keep running and it gets the power from SMPS (Switch
Mode Power Supply). There are various types of connectors which we are going to discuss
below.
AT Connector: It is one of the connectors which are found on the oldest motherboard and
it has 2 numbers of 6 pin male connectors to make the supplying process.
ATX Connector: These types of the connector are found on the latest form of the
motherboard. It consists of 20 or 24 pin female connectors and it is considered as the
latest power connector.
SATA Connector: It stands for Serial Advanced Technology Attachment. It is the latest
connector with 7-pin interface. It is used to connect the SATA hard disks or optical drives.
It is faster and better than the IDE connector.
34 New Gateway to Computer Science Book -9
IDE Connector: It stands for Let’s Review
Integrated Drive Electronics.
It is used to connect Computer hardware is the collection
the disk drives including FDD of physical components that makes a
(Floppy Disk Drives) and HDD computer system.
(Hard Disk Drives). It has 40- A motherboard provides the electrical
pin male connector that is used connections through which the other
to connect HDD and 34-pin male components of the system communicate.
connector that is used to connect the CPU socket helps to install the processor
FDD. into the Motherboard.
RAM is the temporary memory of the
Cabinet Connections: It is the place computer, but it helps to run the application
where the motherboard is installed. and open the files.
It contains many buttons to connect A Motherboard needs power to keep
the cabinet with the motherboard. running and it gets the power from the
Mostly used cabinet connectors are SMPS.
Power Switch, Reset Switch, Front
USB, Front Audio, Power indicator
(LED) and HDD LED.
Understanding Microprocessor
Microprocessor is an internal computer hardware which is a controlling section of
a computer. It is made-up on a small chip capable of performing ALU operations and
communicating with the other devices connected to it. It is also called the CPU which is
the brain of the computer system. The first microprocessor was the Intel 4004, introduced
in 1971. It was not very powerful; it was primarily used to perform simple mathematical
operations in a calculator. Microprocessor consists of an ALU, register array, and a
control unit. Nowadays, modern microprocessors can perform extremely sophisticated
operations in areas such as meteorology, aviation, nuclear physics and engineering, and
take up much less space with much better performance than the previous one.
Functional Sections of Microprocessor
ALU: The ALU section calculates the ability of the microprocessor to perform
either arithmetical or logical operations.
Registers: This section is a temporary storage area that holds data, keep tracks
of instruction, and holds the location and results of these operations.
Control Section: This section regulates the operation of the entire computer system,
by using its instruction decoder to read patterns of data in a designated register and
translate the patterns into activities, such as addition or comparison. It also uses
New Gateway to Computer Science Book -9 35
its interrupt input to indicate the order Let’s Review
in which individual operations use the The first microprocessor was the Intel
CPU and regulate the amount of CPU 4004, introduced in 1971 AD.
time allotted to each operation. Microprocessor consists of an ALU,
Internal Bus: Inernal bus is data register array, and a control unit.
connection between two or more than
two devices connected to the computer. ALU, registers, internal bus and control
sections are the functional sections of
It operates only within the internal microprocessor.
circuitry of the CPU, communicating
among the internal caches of memory that are the parts of the CPU chip's design.
Functions of the Microprocessor
It controls the use of the main storage in storing data and instructions.
Control the sequence of operations.
Give commands to all the parts of the computer system.
Carry out the processing activities.
Understanding Memory
Memory is one or more sets of chips that store data and program instructions, either
temporarily or permanently. Memory is a critical processing component in any computer
system. Personal computer uses several types of memory, but they use two most
important memory they are RAM and ROM which are included in primary memory.
These two types of memory work in very different ways and perform distinct function.
Primary memory is only not sufficient Let’s Review
in computer system but also we must
have secondary memory for storage. Characteristics of Main Memory
Here, we are going to discuss the types These are semiconductor memories.
computer memory.
It is known as the main memory.
Primary Memory Usually volatile memory.
Primary memories are called the Data are lost in case power is switched
main memory that is used to store off.
data and instructions currently
required for processing. These It is the working memory of the
memories are manufactured by computer.
using integrated electronic circuits
or semiconductor device. It has They are faster than secondary
limited capacity and data are lost memories.
A computer cannot run without the
primary memory.
36 New Gateway to Computer Science Book -9
when power is switched off. A memory is just like a human brain. It is used to
store data and instructions. Computer memory is the storage space in the computer, where
data are to be processed and instructions required for processing are stored. Some types
of computer memory are explained below.
RAM (Random Access Memory)
RAM is the most common type of temporary memory which is
made up of a set of chips mounted on a small circuit board. The
information stored in this memory is lost as the power supply to
the computer is turned off. That’s why it is also called volatile
memory. RAM needs a constant supply of power to hold its data.
It stores the data and instruction given by the user and also the results
produced by the computer temporarily. RAM has a tremendous
impact on the speed and power of a computer. Generally, the more RAM a computer
has, the more it can do and the faster it can perform certain tasks. The most common
measurement unit for describing a computer’s memory is the byte. Some common types of
RAM are Dynamic Random Access Memory (DRAM), Synchronous Dynamic Random
Access Memory (SDRAM), Static RAM, Video RAM, Flash RAM, etc.
ROM (Read Only Memory)
ROM is built-in permanent primary memory that stores
data, even when the computer is switched off. ROM is called
non-volatile memory because it never loses its contents. ROM
holds instructions that the computer needs to operate. Whenever
the computers power is turned on, it checks ROM for directions that helps it to start up
for information about its hardware devices. There are various types of ROMs such as
Programmable Read Only Memory (PROM), Erasable Programmable Read Only Memory
(EPROM), Electrically Erasable Programmable Read Only Memory (EEPROM).
Cache Memory
It is a small, fast and expensive semiconductor memory that stores the copies of data that
needs to be accessed frequently from the main memory. It acts as a buffer between the
CPU and the main memory. It is used to hold those parts of data and program which are
most frequently used by the CPU. The cache memory is always placed between CPU and
the main memory of the computer system. The transfer of data between the processor and
the cache memory is bidirectional. The availability of data in the cache is known as cache
hit. The capability of a cache memory is measured on the basis of cache hit.
New Gateway to Computer Science Book -9 37
The advantages of cache memory are as follows:
Cache memory is faster than main memory.
It consumes less access time as compared to main memory.
It stores the program that can be executed within a short period of time.
It stores data for temporary use.
Secondary Memory
This type of memory is also known as external memory or non-volatile memory. It is
slower than the main memory. This memory is permanent in nature. It is used for storing
data and information permanently. It is used to store different programs and the information
permanently. It holds the information till we erase it.CPU directly does not access these
memories; instead they are accessed via input-output routines. The contents of secondary
memories are first transferred to the main memory, and then the CPU can access it. Disk,
CD-ROM, DVD, etc. are the popular Let’s Review
secondary memories. The following are
the characteristics of secondary memory. Primary memories are called the
main memory that are used to store data
These are magnetic and optical and instructions currently required for
memories. processing.
RAM is a volatile memory of the
It is known as the backup memory. computer system.
ROM is called non-volatile memory
It is a non-volatile memory. because it never loses its contents.
The contents of secondary memories
Data is permanently stored even if are first transferred to the main
power is switched off. memory, and then the CPU can access
It is used for storage of data in a
computer.
These are slower than primary
memories. it.
Types of Secondary Memory Cache memory acts as a buffer between
the CPU and the main memory.
Magnetic Storage Device
Magnetic storage can be defined as the storage system that stores the data on a magnetised
medium with the help of magnetised particles. This type of memory is also known as
external memory. It is used for storing data and information permanently. There are many
types of computer storage, but the most common is the magnetic storage device. Magnetic
tapes, magnetic disks, hard disk, floppy disks, etc. are the examples of magnetic storage
system. The magnetic storage systems are non-volatile. Let’s discuss some magnetic
storage devices.
38 New Gateway to Computer Science Book -9
Magnetic Tape
Magnetic tape is one of the oldest technologies for electronic data storage. These are
plastic tapes with magnetic coating. They are used for storing the data, such as text, audio
or video. Magnetic tapes are similar to normal recording tapes. It is a linear recording
system that is not good for random access. A magnetic tape usually consists of a tape of ½
or ¼ inch wide, 600 to 3000 feet long and has wound on a spool in the form of a cartridge
or a reel. In magnetic tapes, the data are stored in the form of records. Let’s discuss some
advantages and disadvantages of using magnetic tape.
Advantages
It has low cost.
It has large storage capacity.
It is easily transportable.
It is very easy to handle and store.
Disadvantages
It has low data transmission speed due to sequential access.
It is not suitable for random access.
It requires protected environment for storage.
It is very difficult for updating, editing and deleting data.
Hard Disk
Hard disk is the main storage device of the computer which is fixed inside the CPU box.
Its storage capacity is very high that varies from 10 GB to 3 TB or even more than that.
As it is fixed inside the CPU box, it is not easy to move the hard disk from one computer
to another. A hard disk contains a number of metallic disks which are called platters.
Information is recorded on the surface of the platters in a series of concentric circles.These
circles are called Tracks. The hard disk platters spin at a high rate of speed, typically 5400
to 7200 revolutions per minute (RPM). The following are the basic components of hard
disk.
Disk platters
Read/ Write head
Head actuator mechanism
Logic board
Cable and connectors
Jumper/switches
Spindle motor
New Gateway to Computer Science Book -9 39
Flash Memory
Flash memory is an electronic memory device popularly known as pen drive in which
data can be stored permanently and erased when it is not necessary. It is a portable storage
device that can be easily connected and removed from the CPU to store data in it. Its
capacity can vary from GB to TB.
Optical Storage Devices
The optical storage systems use the laser light as the optical medium to retrieve as well as
record data. They have more higher area density and longer data life than magnetic storage.
They are also standardized and relatively inexpensive. Like other storage devices, the
optical storage are non-volatile in nature. The optical storage systems are more reliable as
compared to magnetic storage system because they are less prone to mechanical damage.
Types of Optical Disks
Compact Disk (CD): It is a thin plastic disc coated with metal. Computer can read and
write data stored on it.This is an optical storage device with a storage capacity of up to
700 MB and it can store varieties of data like pictures, sounds, movies, texts, etc.
CD-ROM: CD-ROM refers to Compact Disc-Read Only Memory. Data or information
is recorded at the time of manufacturing and it can only be read. A CD-ROM cannot be
used to record fresh data by the computer.
CD-R: CD-R is the short form of Compact Disc-Recordable. Data can be written on it
once and can be read whenever required.The data written once cannot be erased.
CD-RW: CD-RW stands for Compact Disc Re-writable. CD-RW can be used to write
information over and over again and again. Previous information can be erased and new
information can be written on it using a CD writer. CDs are slow in comparison to hard
discs to read or write the information on them.They are portable storage devices.
DVD: DVD stands for Digital Versatile Disc. It is an optical storage device which reads
data faster than a CD. A single layer, single sided DVD can store data up to 4.7 GB, around
6 times more than that of CD and a double layer DVD can store data up to 17.08 GB,
around 25 times more than that of CD. DVDs look just like CDs but they can hold more
data,such as full length movie.
Blu-ray Disc: This is a newly invented optical data storage device whose storage
capacity can be form 25 GB up to 200 GB. It is mainly used to store high quality sound
and movie data.They are the scratch resistant discs, so storing data on them is much safer
than a CD OR DVD.
40 New Gateway to Computer Science Book -9
Let’s Review
Magnetic storage can be defined as the storage system that stores the data
on a magnetised medium with the help of magnetised particles.
In magnetic tapes, the data are stored in the form of records.
Hard disk is the main storage device of the computer which is fixed inside the CPU
box.
Flash memory is a portable storage device that can be easily connected and
removed from the CPU to store the data.
The optical storage systems use the laser light as the optical medium to retrieve as
well as record data.
CD, CD-ROM, CD-R, CD-RW, DVD, etc. are the types of optical storage media.
Units of Memory Management
Data in the computer’s memory are represented by two digits 0 and 1.These two digits are
called Binary Digits or Bits. A bit is the smallest unit of computer’s memory. To represent
each character in memory, a set of 8 binary digits is used. This set of 8 bit is called a Byte.
So, one Byte is used to represent one character of data.
To represent a large amount of data in memory, higher data storage units are used
like KB (Kilobyte), MB(megabyte), GB(Gigabyte), TB(Terabyte), PB(Petabyte), etc.
Let’s discuss the memory units in detail.
Bit (Binary Digit): A binary digit is logical 0 and 1 representing a passive or an active
state of a component in an electric circuit.
Nibble: A group of 4 bits is called nibble.
Byte: A group of 8 bits is called byte. A byte is the smallest unit, which can represent a
data item or a character.
Word: A computer word, like a byte, is a group of fixed number of bits processed as a unit,
which varies from computer to computer but is fixed for each computer. The length of a
computer word is called word-size or word length. It may be as small as 8 bits or may be
as long as 96 bits. A computer stores the information in the form of computer words.
Below are the lists of all the standard units of measurement used for data storage, from
the smallest to the largest.
New Gateway to Computer Science Book -9 41
bit (b) 0 or 1 1/8 of a byte
byte (B) 8 bits 1 byte
kilobyte (KB) 1024 bytes
megabyte (MB) 1024 KB 1,000 bytes
gigabyte (GB) 1024 MB 1,000,000 bytes
terabyte (TB) 1024 GB 1,000,000,000 bytes
petabyte (PB) 1024 TB 1,000,000,000,000 bytes
exabyte (EB) 1024 PB 1,000,000,000,000,000 bytes
zettabyte (ZB) 1024 EB 1,000,000,000,000,000,000 bytes
yottabyte (YB) 1024 ZB 1,000,000,000,000,000,000,000 bytes
brontobyte(BB) 1024 YB 1,000,000,000,000,000,000,000,000 bytes
1,000,000,000,000,000,000,000,000, 000 bytes
Input Devices
All computer peripheral devices which are used to input data and instructions to the
computer are called input devices. They are electromechanical devices that are used
to provide data to a computer for further processing. Input devices accept data and
instructions from the user and convert instructions or data in to a form which can be
understood by the computer. The basic task of an input device is to take the input from the
user and translate it into the machine readable from and then present it to the processing
unit of the computer for execution. A good input device should provide accurate, timely
and useful data to the main memory of the computer for processing.
Types of Input Devices
Keyboard
Keyboard is the most popular input device for direct entry of data
and instructions into computer. The standard QWERTYkeyboard
is used for computer. The computer keyboard is like the electronic
typewriter keyboard. But it has additional keys. The keyboard is
linked to the CPU and it is also linked to the computer screen
so that the data entered into the memory can be seen by the user
as he types in the data. Keyboards are of two sizes 84 keys or 101/102 keys, but now
keyboards with 104 keys or 108 keys are also available. The Computer keyboard has the
following types of keys .
Typing Keys: These keys include digit keys (0-9) and letter keys (A-Z). Which generally
give same layout as that of typewriters.
42 New Gateway to Computer Science Book -9
Numeric Keypad: It is located in the right side of the keyboard. This looks like a
calculator’s keypad with its 10 digits and some mathematical operators.
Function Keys: There are twelve function keys from F1 to F12 that are present on the
keyboard which are arranged in a row at the top of the keyboard. Each function key has
unique meaning and is used for some specific purpose.
Control Keys: These keys provide cursor and screen control. It includes four directional
arrow keys. Control keys also include Home, End, Insert, Delete, Page Up, Page Down,
Control(Ctrl), Alternate(Alt), Escape (Esc), etc.
Special Purpose Keys: The special purpose keys helps to perform certain kind of
operations, like exiting a program or deleting some characters in a document. Keyboard
has also some special purpose keys like Escape, Insert, Pause, Enter, Shift, Caps Lock,
Num Lock, Space bar, Tab, and Print Screen.
Mouse
A mouse is a small hand-held ‘point and click’ device that basically
controls the two-dimensional movement of the cursor on the
displayed screen. It is connected to the CPU through a cable. It
was developed by Douglas Engelbart in 1963 AD. It is generally
used with personal computer. It rolls on a small ball and has two or
three buttons on the top. There are mainly two types of mouse they
are mechanical mouse, and optical mouse.
Mechanical mouse: A mechanical mouse consists of three buttons: left button, right button
and scroll button. Inside the plastic coating of the mouse, there is a ball, which is rolled
over a flat surface corresponding to which the cursor moves on the display screen.
Optical mouse : An optical mouse is a pointing input device in which the reflected light
determines the movement of the cursor on the displayed screen. The upper portion of the
optical mouse is similar to that of the mechanical mouse. The lower portion of the optical
mouse consists of a ball having Light Emitting Diodes (LEDs), an optical sensor and a
Digital Signal Processor (DSP).
Light Pen
It is an electro-optical pointing device that is used for selecting objects
on the display screen with the help of light sensitive pen. Light pen
consists of a stylus connected by a cable to the computer terminal. When
the stylus is brought into contact with the screen, a dot appears there on
the screen. By moving the stylus lines and curves can be drawn on the
screen. A light pen is similar to a mouse. With a this, you can move the pointer and select
objects on the display screen by directly pointing to the objects.
New Gateway to Computer Science Book -9 43
Trackball
It is a pointing device that basically consists of a socket containing the
ball, which can be rolled manually to move the cursor on the screen. It was
originally built into the keyboard. The cursor is used to make selection from
a menu displayed on the computer screen.The trackball is stationary so it
does not require much space to use it. You can place a trackball on any type
of surface. It can be used as a game controller in games like Centipede, Golden Tee and
Marble Madness.
Joystick
Joystick is a pointing device that usually consists of one or more buttons and
a stick which controls the movement of the cursor. The first joystick was
invented in the U.S. by C. B. Mirick and patented in 1926. It is a small vertical
stick attached to a trackball for easier mechanical movements. It is used mainly in game
programs.Today, most computer joysticks connect to the computer using a USB port.
Scanners
Scanner is an input device that optically “reads” an image and
converts it into a digital signal. These are direct-entry input devices.
As the data entry is automatic, the scanners ensure more accurate
data entry. These scanners include optical scanners and magnetic
ink character readers. The optical scanners use light for sensing
input and they include OCR, OMR, Barcode reader, etc.
Touch pad
A touchpad is also called trackpad. It is a flat control surface used
to move the cursor and perform other functions on a computer.
Touchpads are commonly found on laptops and replace the
functionality of a mouse. A touchpad is designed to be controlled
with your finger. Similar to a mouse, touchpads can detect
acceleration as well as linear motion. This allows you to have refined control with slow
movements and quickly move the cursor across the screen using a fast motion.
Optical Mark Reader
Optical Mark Reader (OMR) reads the presence or absence of a
mark on a paper optically. Light is directed on to the paper and the
reflected light is analysed for the detection of a mark. If a mark is
44 New Gateway to Computer Science Book -9
there on the surface of the paper, that area sends back lesser light to the OMR. It is used
to read multiple choice answers in a test and the data are transferred to a computer for
processing.
Optical Character Reader
Optical Character Reader (OCR) detects shape, and can identify
characters. It can examine each character as if it were made up of
a collection of minute spots. Once the whole character has been
scanned, the pattern detected is matched against a set of patterns
stored in the computer. The pattern that matches or nearly matches is taken to be the
character read. Patterns that cannot be identified are rejected. It is used in mail sorting and
credit card billing.
Bar Code Reader
Barcode is a set of small bars of varying thickness and spacing printed
on the packages of products, on the back cover pages of books, tags
etc. The barcode reader uses an optical scanner to read product code
and converts it into electrical pulses. The device is connected to a
computer and the information read is passed to the computer in digital
form for automatic bill generation and updating of files. It is also
called a direct data entry device.
Digital Camera
A digital camera is a handheld electronic device that is used to capture
the image of an object electronically. The digital camera consists of a
built in computer, which helps in recording the images electronically.
Whenever a user initiates the process of capturing an image by pressing
the button available on the camera, the image light enters the camera through the lens.
Microphone
It is an input device that basically converts the sound waves into
electrical signals with the help of sensors. The sound wave pattern
is converted into electrical pattern, which is either in the form of voltage or current. The
microphones are also called transducers as they transform one from of signal into another.
Digitizer Tablet
A digitizer tablet is a peripheral device that allows users to draw on
a computer screen. Tablets are typically used by artists working with
New Gateway to Computer Science Book -9 45
graphics software such as Adobe Photoshop or Illustrator. Tablets allow for much more
precise control than a mouse or trackball. A digitizer tablet is also known as a graphics
tablet.
Touch Screen
A touch screen is an input device of an information processing system.
A user can give input or control the information processing system
through simple or multi-touch. Some touch screens use ordinary or
specially coated gloves to work while others may only work using a
special stylus or pen. It is very popular on laptops and other handled devices. We can use
finger to point the command displayed on the screen.
QR Code Scanner
The QR code stands for Quick Response Code. This system was
invented in 1994 AD by the Japanese company Denso Wave. It was
used to track the vehicles during manufacturing. It was designed to
allow high-speed component scanning. A QR code consists of black
squares arranged in a square grid on a white background, which can be
read by an imaging device such as a camera.
Let’s Review
A bit is the smallest unit of computer’s memory.
Input devices accept data and instructions from the user and convert information
or data in to a form which can be understood by the computer.
A mechanical mouse consists of three buttons: left button, right button and scroll
button.
Keyboard is the most popular input device for direct entry of data and instructions
into the computer.
Light pen consists of a stylus connected by a cable to the computer terminal.
The first joystick was invented in the U.S. by C. B. Mirick and patented in 1926.
Scanner is an input device that optically “reads” an image and converts it into a
digital signal.
OMR reads the presence or absence of a mark on a paper optically.
The barcode reader uses an optical scanner to read product code and converts it into
electrical pulses.
A digitizer tablet is a peripheral device that allows users to draw on a computer
screen.
A touch screen is an input device of an information processing system.
A QR code consists of black squares arranged in a square grid on a white
background.
46 New Gateway to Computer Science Book -9
Output Devices
Output devices are used to display the result for the user. They receive the processed data
from the CPU and present it to the user in desired format. Output devices are pieces of
computer hardware used to communicate the results of data processing performed by a
computer. Output hardware is responsible to convert the machine readable information
into human readable format that may be in the form of text, audio, graphics or video.
Types of Output Devices
There are two types of outputs which are explained below.
Softcopy Output
Soft copy is an electronic display of digital information. The soft copy devices allow the
viewing of information that can be rearranged, modified or corrected as the requirement
of the user. Some types of softcopy output devices are explained below.
Monitors / Display Units
These are the most commonly used softcopy output devices. They display character and
graphics on the screen. Different types of display monitors use different technology for
displaying the data. Let’s discuss different types of monitors.
Cathode Ray Tube (CRT)
Common monitors that use large vacuum tube called Cathode Ray
Tube (CRT) are CRT monitors. They look like a common television
screen. A CRT is the old type of monitor and big in size but it is
cheaper in price. It has high contrast ratio colour depth because of
which it displays the actual colour. CRT monitors are bulky and occupy a lot of space on
the desk. It also consumes a lot of power and produces a large amount of heat.
Liquid Crystal Display (LCD)
LCD monitors use liquid crystals technology to display the output.
The liquid crystals are actually the molecules of the liquid filled
in the LCD. This technology has replaced the traditional Cathode
Ray Tube (CRT) monitors. It is also used in the screens for mobile
devices, such as laptops, tablets, and smartphones. An LCD monitor is small in size and
light in weight so it occupies less space on the desk. The power consumption by an
LCD monitor is very less as liquid molecules need less power to bend light. It has a fix
resolution due to which the images on LCD monitors become blurred when the resolution
is changed.
New Gateway to Computer Science Book -9 47
Light-Emitting Diode (LED)
An LED is an electronic device that emits light when an electrical current is
passed through it. Early LEDs produced only red light, but modern LEDs
can produce several different colours, including red, green, and blue (RGB)
light. Recent advances in LED technology have made it possible for LEDs
to produce white light as well. LEDs are commonly used for indicator lights
(such as power on/off lights) on electronic devices. Traditional flat screen LCD displays
have been started to be replaced by LED displays, which use LEDs for the backlight.
LED TVs and computer monitors are typically brighter and thinner than their LCD.
Let’s Review
Output devices are computer hardwares used to communicate the results of
data processing performed by a computer.
The soft copy devices allow the viewing of information that can be rearranged,
modified or corrected as per the requirement of the user.
An LCD monitor is small in size and light in weight so it occupies less space on the
desk.
ACRT monitor has high contrast ratio colour depth because of which it displays the
actual colour.
An LED is an electronic device that emits light when an electrical current is
passed through it.
Hardcopy Output
A hard copy is a printed copy of information from a computer. The output that we get
from a printer or a plotter on a paper is also known as hardcopy output. Hardcopy output
are permanent outputs which we cannot edit, modify and change easily. We can use
hardcopy output for a long time as well. Let’s discuss some types of hardcopy output.
Printer
A printer is an external output device that takes data from a computer
and generates output in the form of graphics and text on the paper.
There are two types of printers which we are going to discuss below.
Impact Printers
Impact printers are those printers in which mechanical contact
between print head and paper exists. It usually forms the print image
by pressing an inked ribbon against the paper using a hammer or pins.
48 New Gateway to Computer Science Book -9
The following are some popular of impact printers.
Dot-Matrix Printers
The dot-matrix printer uses print heads containing 9 to 24 pins.
These pins produce patterns of dots on the paper to form individual
characters. The 24 pin dot-matrix printer produces more dots that
a 9 pin dot-matrix printer, which results in much better quality and
clearer characters. The pins strike the ribbon individually as the print mechanism moves
across the entire print line in both directions. Dot-matrix printers are inexpensive and
typically print at the speed of 100-600 characters per second.
Daisy-wheel Printer
A daisy wheel printer is an impact printer that produces printout of
good quality character. It contains a metal or a plastic disk on which
the character reside on the outer edge of the petals. These printers are
capable of printing text only and not graphics. They are noisy as well
as very slow and can print approximately 10 to 75 characters per second.
Chain Printer
A chain printer uses a chain of print characters wrapped around two pulleys. Like the
drum printer, there is one hammer for each print position. The hammer then strikes the
page, pressing the paper against a ribbon and the character located at the desired print
position. The chain keeps rotating until all the required print positions on the line have
filled. Speeds of chain printers range from 400 to 2500 characters per minute.
Drum Printer
A drum printer consists of a solid, cylindrical drum that has
raised characters in bands on its surface. The number of print
positions across the drum equals the number available on the
page. This number typically ranges from 80-132 print positions.
Typical speeds of drum printers are in the range of 300 to 2000 lines per minute.
Non-Impact Printers
Non-impact printers are the printers in which mechanical contact between the print head
and paper does not exist. These printers spray ink on the paper with the help of nozzle.
Non-impact printers do not produce much noise than the impact printers. These printers
are faster than the impact printers. Some of the popular non-impact printers are explained
below.
New Gateway to Computer Science Book -9 49
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