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Assistant Professor, Department of Computer Science
Shyama Prasad Mukherji College for Women
University of Delhi
© Oxford University Press. All rights reserved.
Oxford University Press is a department of the University of Oxford.
It furthers the University's objective of excellence in research, scholarship,
and education by publishing worldwide. Oxford is a registered trade mark of
Oxford University Press in the UK and in certain other countries.
Published in India by
YMCA Library Building, 1 Jai Singh Road, New Delhi 110001, India
© Oxford University Press 2014
The moral rights of the author/s have been asserted.
First published in 2014
All rights reserved. No part of this publication may be reproduced, stored in
a retrieval system, or transmitted, in any form or by any means, without the
prior permission in writing of Oxford University Press, or as expressly permitted
by law, by licence, or under terms agreed with the appropriate reprographics
rights organization. Enquiries concerning reproduction outside the scope of the
above should be sent to the Rights Department, Oxford University Press, at the
address above.
You must not circulate this work in any other form
and you must impose this same condition on any acquirer.
Typeset in Times New Roman
by Cameo Corporate Services Limited, Chennai
Printed in India by Rajkamal Electric Press, Kundli, Haryana
I dedicate this book to my family
my uncle Mr B. L. Thareja
Features of
Boolean Algebra and
Introduction to
The book provides a comprehensive coverage of
topics ranging from fundamental concepts of
computers to emerging computer technologies.
Computer Memory and
These elements highlight the important terms
and concepts discussed in each chapter.
A minterm is a product term, but a product term may
or may not be a minterm.
A list of key topics at the end of each chapter
helps the readers to revise all the important
concepts explained in the chapter.
• When computers were first used for business
Input device A device used to feed data and instructions into the computer.
Optical character recognition The process of converting printed material into text or word processing
files that can be easily edited and stored.
Optical devices Devices that use light as a source
of input for detecting or recognizing different
Optical mark recognition The process of electronically extracting data from marked fields, such as
Fig. 8.7 Interpreter
As many as 380 illustrations are included to
support the explanations, which help clarify the
concepts in a clear manner.
Number Systems and
Computer Codes
checkboxes and fill-in fields, on printed forms.
Output device A device that is used to present information from the computer to the user.
Pointing device A device that enables the users to
easily control the movement of the pointer to select
items on a display screen, to select commands from
the command menu, to draw graphs, etc.
Printer A device that takes the text and graphics
information obtained from a computer and prints it on
applications, a group of related records was stored
in a file.
An effective database system comprises four main
components—data, hardware, software, and users.
The main objective of the DBMS is to help users to
efficiently retrieve data from the database.
The DBA enforces data abstraction in database systems by defining data views at three levels—external
view, logical view, and internal (or physical) view.
A database model describes three things—the data,
the relationships that exist between the data, and
the constraints on that data.
The hierarchical data model supports one-to-n
mapping, whereas the network model supports
many-to-many data mapping.
• The data definition module provides functions to
define the structure of the data, and the data
manipulation module provides functions to perform
operations such as inserting, searching, and
deleting data in the database.
• The query processor accepts users' queries and
transforms them into a series of low-level
instructions. The report writer utilizes the output of
query execution to display it in a format that is easy
to understand and interpret format.
• Database users can easily retrieve data from a
database using SQL. The SELECT statement of SQL
allows users to query or retrieve data from a table in
All chapters provide a list of key terms along with
their definitions for a quick recapitulation of
important terms.
Comprehensive exercises are provided at the end
of each chapter to facilitate revision. Answers to
these questions are provided in the Appendix at
the end of book.
1. ________ tells the hardware what to do and how
2. The hardware needs a ________ to instruct what
has to be done.
3. The process of writing a program is called
________.
4. ________ is used to write computer software.
5. ________ transforms the source code into binary
6. ________ allows a computer to interact with additional hardware devices such as printers, scanners, and video cards.
7. ________ helps in coordinating system resources
and allows other programs to execute.
8. ________ provides a platform for running application software.
9. ________ can be used to encrypt and decrypt
files.
10. ________ is a software package that enables its
users to create, edit, print, and save documents
for future retrieval and reference.
11. ________ is used by architects and engineers to
create architectural drawings.
1. BIOS is stored in ________.
(a) RAM
(b) ROM
(c) Hard disk
2. The symbolic language among the following is:
(a) Machine language
(b) C
(c) Assembly language (d) All of these
3. The language that does not need any translator is:
(b) 3GL
(c) Assembly language (d) 4GL
4. Choose the odd one out.
(a) Compiler
(c) Assembler
(b) Interpreter
(d) Linker
5. An example of utility software is:
(a) Word processor
(b) Anti-virus
(c) Desktop publishing tool
8. Give some examples of computer software.
9. Differentiate between the source code and the
object code.
10. Why are compilers and interpreters used?
11. Is there any difference between a compiler and an
interpreter?
12. What is application software? Give examples.
13. What is BIOS?
14. What do you understand by utility software? Is it
necessary to have it?
15. Differentiate between syntax errors and logic errors.
16. Can a program written in a high-level language
Numerous review questions at the end of every
chapter to test the readers' understanding of the
concepts learned.
1. What is Boolean algebra? Give its applications.
2. Explain Boolean laws using Venn diagrams.
3. Draw the Venn diagram for the Boolean expression (A U B)′ ∩ C.
4. Explain the utility of a truth table as a visualization
tool in Boolean algebra.
5. Draw the truth table for Z = A ∩ (B U C).
6. Prove the validity of the consensus and absorption
laws.
7. How are Boolean functions represented?
8. Differentiate between a minterm and a maxterm.
9. Give the minterms and maxterms for the Boolean
AND operation.
10. Explain the steps to convert an SOP expression
into its canonical SOP form with the help of an
11. Convert F(A, B, C) = A′B + B′C + A′C to the canonical SOP form.
12. Explain the steps to convert a POS expression
into the canonical POS form with the help of an
13. Convert F(A, B, C) = (A′ + B′)(B′ + C) to the canonical POS form.
14. What are logic diagrams? How are they useful?
15. Draw the logic diagram for the Boolean expression Y = (A·B + C′·D) + (A′ + D).
16. Implement the following expressions using logic
gates:
(a) Y = (A·B) + (C·D)·E
(b) Y = A + (C + D)·(A·B)
17. Implement the expressions given in Question 16
using NAND gates.
using NOR gates.
19. Write a short note on K-maps.
20. Draw a K-map and simplify the Boolean expression given by f(x, y, z) = Σm(0, 2, 3, 4, 6, 7).
21. What are adder circuits? Explain the different
types of adder circuits.
22. Explain the use of flip-flops in digital circuits.
23. Write a short note on the different types of flipflops.
24. Differentiate between simple and clocked flipflops.
7. In a K-map, groups of cells are formed such that
they do not include a cell with the value 1.
8. Usually, 64-bit ripple carry adders take 200–400
nanoseconds to generate the final sum.
9. The SR flip-flop is a refinement of the JK flip-flop.
10. When J = K = 1, the flip-flop switches to the complement state.
State True or False
1. Computer hardware is constituted by its physical
components.
2. Computer hardware cannot think and make decisions on its own.
3. Software is a set of instructions arranged in a
sequence to guide the computer to find a solution
for a given problem.
4. Word processor is an example of educational
5. Desktop publishing system is a type of system
21. In the ________ phase, a plane of actions is
22. Algorithms and flowcharts are designed in the
________ phase.
These step-by-step tutorials help the readers to
learn different applications such as Ms Word, Ms
PowerPoint, and Ms Excel, as well as to access
and use the Internet and to add different devices
to a computer.
3 Working with the
CREATING A NEW GMAIL ACCOUNT
Step 1: Open any web browser such as Internet Explorer,
Netscape Navigator, Google Chrome, or Mozilla
Step 2: In the address bar, type www.gmail.com. You will
get the page shown in Figure A3.1.
Step 3: Click on the Create an account button (indicated by
the arrow in the figure).
Step 4: Fill your details in the form (Figure A3.2) provided
and click on Next step.
Step 5: You will be asked to enter your phone number
for verification. Enter the number and click on
Step 6: Your Gmail account is now created. Click on
Show me my account. Your mailbox will be displayed as shown in Figure A3.3. Now you can send
emails, photographs, files, or any other document
to your friend To read an email simply click on
questions to enable students to check their understanding
of the concepts
• Includes a list of key terms at the end of each chapter that
facilitates revision of important topics learned
• Highlights important concepts in the form of Notes
• Includes a separate section on Lab Activities
ORGANIZATION OF THE BOOK
The book is organized into twelve chapters and seven lab
Chapter 1 provides an introduction to computers. The chapter explains the applications, classifications, and the basic
organization of the computer system.
Chapter 2 gives a detailed description of the different types
of input and output devices.
Chapter 3 explains the significance of memory hierarchy
and discusses the different types of primary, secondary, and
tertiary memory that are widely used to store data. It also
discusses the basic processor architecture (including RISC
and CISC) and the instruction set.
Today computers are used in almost every field, starting from
education, medical, banking, construction, communication;
to defence, transportation, sports, manufacturing, marketing, etc. The list is literally unending. In a world driven by
Information Technology (IT), it is difficult to fathom a field
that does not make use of computers!
The use of computers has become so widespread that
almost every electrical and electronic device (such as a
washing machine or an air conditioner) has a small embedded computer within it. In India, computers are now a part of
millions of households. Even the mobile phones that we use
are smartphones (phones with computing technology) that
are connected to the Internet.
Information technology has revolutionized our lifestyle.
Online banking and shopping are being preferred. Employees
can work from home to save time commuting to their offices.
Therefore, in today's scenario learning computers is not just
a prerogative of students pursuing a career in engineering
and technology; it is a must for everyone. Computing skills
help one to be more productive and efficient. Therefore,
a basic knowledge of computers and its technology will
definitely pay rich dividends in the future.
Fundamentals of Computers is an ideal textbook for learning computers on one's own. The book covers both the basic
concepts of computers such as organization, architecture,
input and output devices, and primary and secondary memory as well as advanced topics including operating systems,
computer networks, and databases. The book also offers
step-by-step tutorials to learn applications such as MS Word,
MS PowerPoint, and MS Excel.
Since the use of computer is no longer confined to engineers and scientists, the book can be used by a broad spectrum
of students, ranging from students enrolled in elementary
courses on Information Technology and Computer Sciences
to those in professional courses such as BTech, BBA, BCA,
and MCA. It would also be a valuable reference for diploma
courses and courses taught at the polytechnic level.
• Provides a comprehensive coverage of important topics
ranging from basics of computers to emerging technologies
• Supports numerous well-labelled diagrams in all
• Provides a wealth of solved examples and chapter-end
exercises in the form of objective type questions and review
Chapter 4 explains the binary number system representation and discusses the binary, octal, and hexadecimal number
systems. The chapter enables the reader to perform arithmetic operations such as addition, subtraction, multiplication,
and division on binary numbers. Important binary codes
such as ASCII, EBCDIC, Excess 3, and Gray Codes are also
discussed in the chapter.
Chapter 5 discusses the concepts of digital computing systems such as Boolean Algebra, Boolean functions, Boolean
expressions, logic gates, adder circuits, and flip flops.
Chapter 6 is about computer software. It brings out the
difference between application and system software. The
chapter discusses the different types of system software and
application software packages that are widely used.
Chapter 7 discusses operating systems and their evolution.
It also explains the different jobs that an operating system
performs and discusses some commonly used operating systems such as Windows, Unix, Linux, and DOS.
Chapter 8 explains algorithms, psuedocodes, and flowcharts which are considered to be the first step towards writing a computer program. The chapter introduces the concept
of programming languages and their evolution through years.
The chapter also discusses different paradigms of programming and discuses some popular programming languages
such as C, C++, Java, Pascal, BASIC, FORTRAN, and
LISP.
Lab Activities will prove very beneficial for getting a
hands-on experience while working with computer systems.
Chapter 9 gives a description of traditional fileoriented approach of data management and introduces
the concept of databases, their architecture, models, and
Appendix at the end of the book provides answers to objective questions given in each chapter.
Chapter 10 discusses computer networks, their applications, the connecting media, data transmission mode, network topologies, area networks, and the devices used to form
a network. It also details data switching and multiplexing
techniques.
The mammoth task of writing this book required the help
and support of many individuals. Fortunately, I have had the
wholehearted support of my family and friends.
I would like to specially thank my father Mr Janak Raj
Thareja and mother Mrs Usha Thareja, my brother Pallav,
and sisters Kimi and Rashi who are a source of abiding inspiration and divine blessings for me. I am especially thankful
to my son Goransh who has been very patient and cooperative in letting me realize my dreams. My sincere thanks go
to my uncle Mr B.L. Thareja for his inspiration and guidance
in writing this book.
Finally, I would like to thank the editorial team at Oxford
University Press India for their help and support.
Chapter 12 introduces new and emerging technologies
such as peer-to-peer computing, distributed computing,
cloud computing, grid computing, on-demand computing,
Bluetooth networks, and wireless networks.
Chapter 11 introduces the concept and evolution of the
Internet. It discusses different services provided by the Internet, threats to security, and counter measures to be adopted
for ensuring privacy and security over the Internet.
Reema Thareja
Brief Contents
Features of the Book iv
Preface vii
Detailed Contents xi
1. Introduction to Computers ...............................................................................................................................
2. Input and Output Devices .............................................................................................................................. 14
3. Computer Memory and Processors ................................................................................................................ 30
4. Number Systems and Computer Codes ......................................................................................................... 48
5. Boolean Algebra and Logic Gates ................................................................................................................. 62
6. Computer Software ........................................................................................................................................ 84
7. Operating Systems ......................................................................................................................................... 100
8. Introduction to Algorithms and Programming Languages ............................................................................ 127
9. Database Systems .......................................................................................................................................... 149
10. Computer Networks ....................................................................................................................................... 161
11. The Internet .................................................................................................................................................... 182
12. Emerging Computer Technologies ................................................................................................................. 195
1: Understanding Computer Hardware 217
2: Adding Devices to a Computer 223
3: Working with the Internet 227
4: Working with Microsoft Word 232
5: Working with Microsoft Excel 240
6: Working with Microsoft Access 249
7: Working with MS Office 262
Appendix: Answers to Objective Questions 266
Detailed Contents
4.3 Octal Number System
4.3.1 Converting an Octal Number into Decimal
4.3.2 Converting a Decimal Number into Octal Form 53
4.3.3 Converting an Octal Number into Binary Form 53
4.3.4 Converting a Binary Number into Octal Form 53
4.4 Hexadecimal Number System
4.4.1 Converting a Hexadecimal Number into
Decimal Form 54
4.4.2 Converting a Decimal Number into
Hexadecimal Form 54
Binary Form 54
4.4.4 Converting a Binary Number into
Octal Form 54
4.4.6 Converting an Octal Number into
5.9 Simplification of Boolean Expressions Using
5.10 Adder Circuits
Identity Law 64
Idempotency Law 64
Complement Law 64
Involution Law 64
Commutative Law 65
Associative Law 65
Distributive Law 65
Absorption Law 66
Consensus Law 66
De Morgan's Laws 66
6.1 Introduction to Computer Software
6.2 Classification of Computer Software
6.3 System Software
Basic Laws of Boolean Algebra
4.8.1 ASCII Code 58
4.8.2 Extended Binary Coded Decimal Interchange
4.8.3 Excess-3 Code 59
4.8.4 Other Weighted Codes 59
4.8.5 Gray Code 59
4.8.6 Unicode 59
SR Flip-flop 78
JK Flip-flop 78
T Flip-flop 79
D Flip-flop 79
5.12 Applications of Flip-Flops
Boolean Algebra and Logic Gates
5.10.1 Half Adder 75
5.10.2 Full Adder 76
5.10.3 Ripple Carry Adder 76
4.6.1 Sign-and-magnitude 56
4.6.2 One's Complement 57
4.6.3 Two's Complement 57
5.8.1 NAND Universal Gate 71
5.8.2 NOR Universal Gate 72
5.11 Flip-Flops
4.5 Working with Fractions
4.6 Signed Number Representation in Binary Form
4.7 BCD Code
4.8 Other Codes
5.8 Universal Gates
Computer BIOS and Device Drivers 85
Operating System 86
Utility Software 86
Compiler, Interpreter, Linker, and Loader 87
Acquiring Computer Software
Design and Implementation of Correct, Efficient,
and Maintainable Programs
7.2 Evolution of Operating Systems
7.3 Process Management
Process Control Block 105
Process Operations 106
Processes Scheduling 106
Process Synchronization 107
Interprocess Communication 107
Deadlock 107
7.4 Memory Management
7.4.1 Multiple Partition Allocation 108
7.4.2 Paging 109
7.4.3 Segmentation 109
7.5 File Management
5.5 Representations of Boolean Functions
5.5.1 Minterm 67
5.5.2 Maxterm 68
5.6 Logic Gates
5.7 Logic Diagrams and Boolean Expressions
Data Hierarchy 111
File Attributes 111
Basic File Operations 112
File Organization 112
7.6 Device Management
7.7 Security Management
7.8 Command Interpreter
7.9 Popular Operating Systems
Introduction to Algorithms and
8.1 Algorithm
8.2 Control Structures Used in Algorithms
8.2.1 Sequence 127
8.2.2 Decision 128
8.2.3 Repetition 128
8.5.1 Keywords Used while Writing Pseudocodes 131
8.6 Programming Languages
8.7 Generations of Programming Languages
First Generation: Machine Language 133
Second Generation: Assembly Language 134
Third Generation: High-level Language 135
Fourth Generation: Very High-level
Languages 137
8.7.5 Fifth-generation Programming Language 138
Twisted-pair Wires 162
Coaxial Cables 162
Fibre Optic Cables 162
Wireless Technologies 163
8.8 Categorization of High-level Languages
8.9 Some Popular High-level Languages
BASIC 142
FORTRAN 143
Pascal 143
C++ 143
Java 144
LISP 144
10.5 Data Switching
Database Systems
9.1 File-Oriented Approach
9.2 Database-oriented Approach
9.2.1 Components of Database System 151
9.2.2 Advantages of Database Approach 152
9.2.3 Disadvantages of Database Approach 152
10.5.1 Circuit Switching 168
10.5.2 Message Switching 168
10.5.3 Packet Switching 169
Local Area Network 172
Wide Area Network 172
Metropolitan Area Network 173
Campus/Corporate Area Network 173
Personal Area Network 174
10.9 Networking Devices
Bus Topology 170
Star Topology 170
Ring Topology 171
Mesh topology 171
Hybrid Topology 171
10.8 Types of Network
8.10 Factors Affecting Selection of Programming
10.4.1 Techniques of Multiplexing 166
10.6 Data Routing Techniques
10.7 Network Topologies
Unstructured Programming 138
Structured Programming Language 138
Logic-oriented Programming Language 139
Object-oriented Programming 140
10.3.1 Simplex, Half-duplex, and Full-duplex
Connections 163
10.3.2 Serial and Parallel Transmissions 164
10.3.3 Synchronous and Asynchronous Data
Transmission Modes 165
10.4 Data Multiplexing
10.3 Data Transmission Mode
8.5 Pseudocode
8.4.1 Significance of Flowcharts 129
8.4.2 Advantages 130
8.4.3 Limitations 131
9.6 Components of Database Management
9.7 Retrieving Data Through Queries
Hierarchical Model 154
Network Model 154
Relational Model 155
Object-oriented Data Model 156
10.1 Introduction to Computer Networks
10.2 Connecting Media
8.3 Some More Algorithms
8.4 Flowcharts
9.3 Database Views
9.4 Three-schema Architecture
9.5 Database Models
Microsoft DOS 119
Microsoft Windows 120
9.2.4 Applications of Database Systems 152
Hub 174
Repeater 174
Bridge 174
Router 175
Network Interface Card 175
10.10 Open System Interconnection Model
11.1 Internet
12.3 Grid Computing
11.1.1 History 182
11.2 Internet Services
Electronic Mail 183
File Transfer Protocol 183
Chatting 184
Internet Conferencing 184
Electronic Newspaper 184
World Wide Web 185
Online Shopping 185
Search Engine 186
12.4 Cloud Computing
Dial-up Connection 188
Integrated Services Digital Network 188
Leased Connection 188
Digital Subscriber Line Connection 188
Cable Modem Connection 188
Very Small Aperture Terminal 189
11.5 Internet Security
12.8.1 Bluetooth Piconets 208
12.8.2 Avoiding Interference in Bluetooth
Devices 209
12.8.3 Bluetooth Security 209
12.8.4 Differences between Bluetooth and Wireless
Networks 210
12.9 Artificial Intelligence
12.1 Distributed Networking
12.2 Peer-to-peer Computing
Wireless Network Operation 205
Types of Wireless Networks 206
Security in Wireless Networks 206
Limitations of Wireless Networks 207
12.8 Bluetooth
Emerging Computer Technologies
12.5 Utility Computing
12.6 On-demand Computing
12.7 Wireless Network
11.5.1 Threats to Internet Security 189
11.5.2 Preventive Measures 192
12.4.1 Characteristics of Cloud Computing
Systems 200
12.4.2 Cloud Computing Services 200
12.4.3 Cloud Computing Architecture 201
12.4.4 Cloud Computing Applications 202
12.4.5 Cloud Computing Concerns 202
11.3 Internet Glossary
11.4 Types of Internet Connections
12.3.1 Components of Grid Computing 199
12.3.2 Applications of Grid Computing 199
12.2.1 Categorization of Peer-to-peer Systems 196
12.2.2 Applications and Considerations of
Peer-to-peer Networks 197
WHAT IS A COMPUTER?
In this chapter, we will learn the definition and various characteristics of computers and see how they
have evolved from big machines used only for scientific purposes to small devices that can even be
used in a wristwatch. We will read about the different types of computing devices, the basic organization
of a computing device, and see how computers are used in different areas of our day-to-day lives.
A computer, in simple terms, can be defined as an electronic
device that is designed to accept data, perform the required mathematical and logical operations at high speed, and output the result.
We all have seen computers in our homes, schools, and
colleges. In fact, in today's scenario, we find computers in
most aspects of our daily lives. For some of us, it is hard to
even imagine a world without them.
In the past, computers were extremely large in size and often
required an entire room for installation. These computers consumed enormous amounts of power and were too expensive to
be used for commercial applications. Therefore, they were used
only for limited tasks, such as computing trajectories for astronomical or military applications. However, with technological
advancements, the size of computers became smaller and their
energy requirements reduced immensely. This opened the way
for adoption of computers for commercial purposes.
These days, computers have become so prevalent in the market that all interactive devices such as cellular phones, global
positioning system (GPS) units, portable organizers, automatic
teller machines (ATMs), and gas pumps, work with computers.
CHARACTERISTICS OF COMPUTERS
We have seen that a computer is an electronic device that performs a function based on a given set of instructions known
as a program. A computer accepts data, processes it, and produces information (see Figure 1.1). Here, data refers to some
raw facts or figures, and information implies the processed
data. For example, if 12-12-92 is the date of birth of a student, then it is data (a raw fact/figure). However, when we
process this data (subtract it from the present date) and say
that the age of the student is 18 years, then the outcome is
Fig. 1.1 Functions of computers
Today, computers have become a crucial part of our everyday
lives, and we need computers just like we need the television,
telephones, or other electronic devices at home. Computers
are basically meant to solve problems quickly and accurately.
The important characteristics of a computer (refer to Figure 1.2)
are discussed in the following text.
Fundamentals of Computers
Speed Computers can perform millions of operations per
second, which means that data that may otherwise take many
hours to process is output as information in the blink of an
eye. The speed of computers is usually given in nanoseconds
and picoseconds, where 1 nanosecond = 1 × 10−9 seconds and
1 picosecond = 1 × 10−12 seconds.
No IQ Although the trend today is to make computers intelligent by inducing artificial intelligence (AI) in them, they
still do not have any decision-making abilities of their own.
Thus, their IQ level is zero. They need guidance to perform
various tasks.
Economical Today, computers are considered as short-term
investments for achieving long-term gains. Using computers
also reduces manpower requirements and leads to an elegant
and efficient way of performing various tasks. Hence, computers save time, energy, and money. When compared to
other systems, computers can do more work in lesser time.
For example, using the conventional mail system to send an
important document takes at least two or more days, whereas
the same information when sent using the Internet (e-mail)
will be delivered instantaneously.
Accuracy A computer is a very fast, reliable, and robust
electronic device. It always gives accurate results, provided
the correct data and set of instructions are input to it. Hence,
in the event of an error, only the user who has fed the incorrect
data/program needs be held responsible. This clearly means
that the output generated by a computer depends on the given
instructions and input data. If the input data is wrong, then
the output will also be erroneous. In computer terminology,
this is known as garbage-in, garbage-out (GIGO).
Automation Besides being very fast and accurate, computers are automatable devices that can perform a task without
any user intervention. The user just needs to assign the task to
the computer, after which it automatically controls different
devices attached to it and executes the program instructions.
Diligence Unlike humans, computers never get tired of a
repetitive task. It can continually work for hours without creating errors. Even if a large number of executions are needed,
each and every execution requires the same duration, and is
executed with the same accuracy.
Versatile Versatility is the quality of being flexible. Today,
computers are used in our daily life in different fields. For
example, they are used as personal computers (PCs) for home
use, for business-oriented tasks, weather forecasting, space
exploration, teaching, railways, banking, medicine, and so
on, indicating that computers can perform different tasks
simultaneously. On the PC that you use at home, you may
play a game, compose and send e-mails, listen to music, etc.
Therefore, computers are versatile devices as they can perform multiple tasks of different nature at the same time.
Memory Similar to humans, computers also have memory.
Just the way we cannot store everything in our memory
Fig. 1.2 Characteristics of computers
and need secondary media, such as a notebook, to record
certain important things, computers also have internal or
primary memory (storage space) as well as external or secondary memory. While the internal memory of computers is
very expensive and limited in size, the secondary storage is
cheaper and of bigger capacity.
The computer stores a large amount of data and programs
in the secondary storage space. The stored data and programs
can be retrieved and used whenever required. Secondary
memory is the key for data storage. Some examples of secondary devices include floppy disks, optical disks (CDs and
DVDs), hard disk drives (HDDs), pen drives, etc.
When data and programs have to be used, they are copied
from the secondary memory into the internal memory, often
known as random access memory (RAM). The concept of
computer memory is discussed in detail in Chapter 4.
GENERATIONS OF COMPUTERS
The word generation, in general, indicates a state of improvement in the product development process. When applied to
computing, it refers to the different advancements of new
computer technology. With each new generation of computers, the circuitry becomes smaller and more advanced than
that used in the previous generation. The focus of every new
generation has been on miniaturization, speed, power, and
efficient computer memory.
Therefore, each generation of computers is characterized
by a major technological development that has drastically
changed the way in which computers operate. Consequently,
these computing devices have become smaller, cheaper, powerful, efficient, and more reliable. In this section, we will read
about the major developments in technology that have led to
the devices that we use today.
1.3.1 First Generation (1940–1956): Vacuum Tubes
First-generation computers used a very large number of vacuum tubes (as shown in Figure 1.3) for circuitry and magnetic
Introduction to Computers
Fig. 1.3 Vacuum tube
Fig. 1.4 Transistors
Input was fed to the second-generation computers using
punched cards and output was generated as printouts.
While the first-generation computers were programmed
using machine language, the second-generation computers moved towards symbolic or assembly languages, which
allowed programmers to specify instructions in words.
At this time, high-level programming languages such as
COBOL, FORTRAN, ALGOL, and SNOBOL were also
being developed. Second-generation computers were the
first to store instructions in memory, which moved from
magnetic drum to magnetic core technology. Secondgeneration computers were first developed for the atomic
energy industry.
drums for memory. These computers were so big in size that
they often required an entire room to be installed. The firstgeneration computers were very expensive and were hence
mainly used for scientific purposes. In addition to a large
amount of space, they also needed a lot of electricity, and
thus generated enormous heat, which was often the cause of
malfunctions.
First-generation computers could be programmed using
machine language, which is the lowest-level programming
language, consisting of only 1s and 0s. These computers
could solve only one problem at a time. While input to the
computer was fed using punched cards and paper tape, the
output was generated on printouts.
Universal automatic computer (UNIVAC) and electronic
numerical integrator and calculator (ENIAC) are prime
examples of first-generation computing devices. Moreover,
UNIVAC was the first commercial computer delivered to a
business client (US Census Bureau in 1951).
They were the fastest calculating devices of their time.
• They consumed less electricity and thus generated less
heat as compared to the first-generation computers.
• They were faster, cheaper, smaller, and more reliable than
• They generated a lot of heat.
their first-generation counterparts.
• They consumed a lot of electricity.
• They could be programmed using assembly language and
• They were very bulky in size.
high-level languages.
• Vacuum tubes used filaments that had limited life. Since • These computers had faster primary memory and a larger
every computer used thousands of vacuum tubes, these
computers were frequently down due to hardware failure.
• These computers needed constant maintenance because of
the low mean time between failures.
• These computers had limited commercial use because they
were difficult to program.
• They were very expensive.
secondary memory.
Second-generation computers were manufactured using
transistors, which had to be assembled manually. This
made commercial production of computers difficult and
1.3.3 Third Generation (1964–1971): Integrated
Second-generation computers were manufactured using tran1.3.2 Second Generation (1956–1963): Transistors
sistors (as shown in Figure 1.4), rather than vacuum tubes.
Transistors were invented in 1947 but were used for manufacturing computers only in the late 1950s. Transistors were far
superior to vacuum tubes. Computers manufactured using transistors were smaller, faster, cheaper, and more energy-efficient
and reliable than their first-generation predecessors. Although
transistors also generated enormous heat, which subjected the
computer to damage, they were far better than vacuum tubes.
The development of the integrated circuit (IC), shown in
Figure 1.5, was the hallmark of the third-generation computers. Several electronic components such as transistors, resistors, and capacitors were miniaturized and placed on silicon
chips, called integrated chips, which drastically increased the
speed and efficiency of computers.
Integrated chips were smaller, less expensive, more
reliable and faster in operation, consumed less power,
1.3.4 Fourth Generation (1971–1989):
and generated less heat than the components used earlier. The third-generation computers were also much more
powerful than their predecessors. These computers had a
few megabytes of main memory and magnetic disks that
could store a few tens of megabytes of data per disk drive.
On the software front, high-level programming languages
such as COBOL and FORTRAN were standardized by the
American National Standards Institute (ANSI), and were
known as ANSI FORTRAN and ANSI COBOL, respectively.
Standardization helped these languages to run on any computer that had their respective compiler. In addition to this,
some more high-level programming languages such as PL/I
PASCAL and BASIC were introduced at this time. Thirdgeneration computers were the first to implement time sharing operating systems. Input to these computers could now be
provided using the keyboard and the mouse.
In the 1960s, the trend was moving towards small minicomputers that could fit in the corner of a room and be used
for business applications. It was during this time that software houses emerged.
Fig. 1.5 Integrated circuits
The microprocessor launched the fourth generation of computers, with thousands of integrated circuits built onto a single silicon chip. While first-generation computers often filled
an entire room, fourth-generation computers, on the contrary,
could fit in the palm of the hand. For example, the Intel 4004
chip, developed in 1971, consisted of all the components
of the computer (such as the central processing unit, CPU;
memory; I/O controls, etc.) on a single chip.
During the fourth generation, semiconductor memories
that were very fast were used and HDDs also became cheaper,
smaller in size, and larger in capacity. For input, floppy disks (in
addition to magnetic tapes) were used to port data and programs
from one computer to another. During this period, many new
operating systems were developed, including MS-DOS, Microsoft Windows, UNIX, and Apple's proprietary operating system.
In 1981, IBM introduced the first PC that was specifically
meant for the home user, and in 1984 Apple introduced the Macintosh. As these small computers became more powerful, they
could be linked together to form networks, which eventually led
to the development of the Internet and other distributed systems.
Fourth-generation computers also saw the development of
graphical user interfaces (GUIs), the mouse, and handheld
devices. GUIs made computers more user-friendly, so that
even a non-computer professional could work easily on it.
In this period, several word processing packages (to allow
easy development of documents), spreadsheet packages (to
allow easy manipulation and analysis of data organized in
rows and columns), and graphics packages (to easily draw
and edit images) were introduced, thereby making computers
a powerful tool for everyone.
• These computers were smaller, cheaper, faster, and more
• They were faster than second-generation computers and
could perform one million transactions per second.
They were smaller, cheaper, and more reliable than their
predecessors.
These computers had faster and larger primary memory
and secondary storage.
Third-generation computers were widely used for scientific
as well as business applications.
During this generation of computers, standardization of
existing high-level languages and invention of new highlevel languages happened.
Third-generation computers could run time sharing operating systems, which allowed interactive use of a computer
by one or more users simultaneously, thereby improving
the productivity of the users.
• These computers were difficult to maintain.
• They got heated very quickly.
reliable than their predecessors.
• They consumed less electricity and generated less heat.
• They had faster and larger primary memory and secondary
• They could be used as general-purpose computers.
• GUIs enabled people to learn to work with computers very
easily. Hence, the use of computers both in offices and at
homes became widespread.
• Networks allowed sharing of resources, thereby enabling
efficient utilization of computer hardware and software.
They were not intelligent systems.
1.3.5 Fifth Generation (Present and Beyond):
Fifth-generation computers are completely based on the
new concept of artificial intelligence (AI). Although such
It is in the fifth generation of computing devices that
voice recognition systems that can convert spoken sounds
into written words have come into existence. Such systems
do not understand what they are writing; they simply take
dictation. Although there are certain expert systems available today, they have not lived up to the expectations. They
are too expensive to produce and are helpful only in special
situations.
Today, the hottest area of AI is neural networks. Neural
network systems are widely being used in different fields
such as voice recognition and natural language processing.
Fifth-generation languages, commonly known as AI languages, are almost exclusively used for AI applications. The
two most common are LISP and Prolog.
CLASSIFICATION OF COMPUTERS
Computers can be broadly classified into four categories
based on their speed, amount of data that they can hold,
and price (refer to Figure 1.6). These categories are as
Supercomputers
Mainframe computers
computers are still in development, there are certain applications such as voice recognition that are widely being used
today. Parallel processing and superconductor technology
have made AI a reality. Quantum computation and nanotechnology will radically change the face of computers in the
years to come. In the fifth-generation computers, the aim is
to develop devices that respond to natural language input and
are capable of learning and self-organization. AI touches the
following areas, among others:
Gaming Computers are programmed to play games such as
chess and checkers. More recent examples of such gaming
systems include PlayStation by Sony, Xbox 360 by Microsoft, and Wii by Nintendo, all of which use sensor technology
to detect players' movements.
Expert systems Computers are programmed to take decisions in real-world situations. For example, some expert
systems help doctors in diagnosing the disease, based on
patients' symptoms.
Natural languages Computers are programmed to understand and respond to natural human languages.
Neural networks Systems are programmed to simulate
intelligence by reproducing the physical connections that
take place in animal brains.
Robotics Computers are programmed to look, listen, and
react to other sensory stimuli.
The current status is that no computer is able to completely
simulate human behaviour. In other words, no computer
exhibits complete AI. However, one of the biggest achievements of these computers has been in the field of gaming. For
example, in 1997, a computer program defeated the world
champion Gary Kasparov in a game of chess.
In robotics, computers are widely used in manufacturing
and assembly plants for performing certain tasks. However,
the tasks that robots can perform are limited as they find it
difficult to identify objects based on appearance or feel, and
they still move and handle objects clumsily.
Natural language programs enable people to interact with
computers. Although programming computer systems to
understand natural languages has proved to be much more
difficult than originally planned for, there are some systems
that can translate one human language to another, though
they are not as good as human translators.
1.4.1 Supercomputers
Among the four categories, the supercomputer is the fastest, most powerful, and most expensive computer. Supercomputers were first developed in the 1980s to process
large amounts of data and to solve complex scientific problems. Supercomputers use parallel processing technology
and can perform more than one trillion calculations in a
second.
A single supercomputer can support thousands of users at
the same time. Such computers are mainly used for weather
forecasting, nuclear energy research, aircraft design, automotive design, online banking, controlling industrial units, etc.
Some examples of supercomputers are CRAY-1, CRAY-2,
Control Data CYBER 205, and ETA A-10.
Dumb terminals
Intelligent terminals
Fig. 1.6 Classification of computers
Handheld devices
1.4.4 Microcomputers
Mainframe computers are large-scale computers (but
smaller than supercomputers). These are very expensive and
need a very large clean room with air conditioning, thereby
making them very costly to deploy. As with supercomputers,
mainframes can also support multiple processors. For example, the IBM S/390 mainframe can support 50,000 users at
the same time. Users can access mainframes by either using
terminals or via PCs. There are basically two types of terminals that can be used with mainframe systems that are discussed as follows:
Dumb terminals consist of only a monitor and a keyboard (or
mouse). They do not have their own CPU and memory and
use the mainframe system's CPU and storage devices.
Microcomputers, commonly known as PCs, are very small
and cheap. The first microcomputer was designed by IBM
in 1981 and was named IBM-PC. Later on, many computer
hardware companies copied this design and termed their
microcomputers as PC-compatible, which refers to any PC
that is based on the original IBM PC design.
Another type of popular PC is designed by Apple. PCs
designed by IBM and other PC-compatible computers
have a different architecture from that of Apple computers.
Moreover, PCs and PC-compatible computers commonly
use the Windows operating system, while Apple computers use the Macintosh operating system (MacOS). However,
IBM and IBM-compatible PCs are more popular than their
Apple counterparts. PCs can be classified into the following
In contrast to dumb terminals, intelligent terminals have their
own processor and thus can perform some processing operations. However, just like the dumb terminals, they do not have
their own storage space. Usually, PCs can be used as intelligent terminals to facilitate data access and other services
from the mainframe system.
Mainframe computers are typically used as servers on
the world wide web. They are also used in large organizations such as banks, airline companies, and universities,
where a large number of users frequently access data stored
in their databases. IBM is the major manufacturer of mainframe computers. Some examples of mainframe computers include IBM S/390, Control Data CYBER 176, Amdahl
580, etc.
A desktop PC is the most popular model of PCs. The system
unit of the desktop PC can be placed flat on a desk or table. It
is widely used in homes and offices.
Laptops (Figure 1.7) are small microcomputers that can easily fit inside a briefcase. They are very handy and can easily
be carried from one place to another. They may also be placed
on the user's lap (thus the name). Hence, laptops are very useful, especially when going on long journeys. Laptops operate
on a special battery and do not always have to be plugged in
like desktop computers.
1.4.3 Minicomputers
1.4.2 Mainframe Computers
As the name suggests, minicomputers are smaller, cheaper,
and slower than mainframes. They are called minicomputers
because they were the smallest computer of their times. Also
known as midrange computers, the capabilities of minicomputers fall between mainframe and PCs.
Minicomputers are widely used in business, education,
hospitals, government organizations, etc. While some minicomputers can be used only by a single user, others are specifically designed to handle multiple users simultaneously.
Usually, single-user minicomputers are used for performing
complex design tasks.
As with mainframes, minicomputers can also be used as
servers in a networked environment, and hundreds of PCs can
be connected to it.
The first minicomputer was introduced by Digital Equipment Corporation (DEC) in the mid 1960s. Other manufacturers of minicomputers include IBM Corporation
(AS/400 computers), Data General Corporation, and Prime
Fig. 1.7 Laptop
The memory and storage capacity of a laptop is almost equivalent to that of a desktop computer. As with desktop computers, laptops also have HDDs, floppy disk drives, zip disk
drives, etc. For input, laptops have a built-in keyboard and a
trackball/touchpad, which is used as a pointing device (as a
mouse is used for a desktop PC).
Workstations are single-user computers that have the same
features as PCs, but their processing speed matches that of
a minicomputer or mainframe computer. Workstation computers have advanced processors, more RAM and storage
capacity than PCs. Therefore, they are more expensive and
powerful than a normal desktop computer.
Although workstation computers are widely used as powerful single-user computers by scientists, engineers, architects, and graphic designers, they can also be used as servers
in a networked environment.
Personal digital assistants (PDA) Today, the PDA (shown
in Figure 1.8) is among the most popular lightweight mobile
devices that are used. A number of PDAs available in the
market offer a collection of application software for word
processing, spreadsheets, games, etc. PDAs are used to take
notes, organize telephone numbers, and store addresses.
Some devices also include features that facilitate the users to
read e-books on the PDA's screen.
they have small-sized screens and keyboards. These computers are preferred by business travellers and mobile employees
such as meter readers and parcel delivery people, whose jobs
require them to move from place to place. Some examples of
handheld computers are
• Personal digital assistant (PDA)
• Cellular telephones
• H/PC Pro devices
Today, laptops have the same features and processing
speed as the most powerful PCs. However, a drawback is
that laptops are generally more expensive than desktop computers. These computers are very popular among business
travellers.
Network Computers
Network computers have less processing power, memory,
and storage than a desktop computer. These are specially
designed to be used as terminals in a networked environment. For example, some network computers are specifically
designed to access data stored on a network (including the
Internet and intranet).
Some network computers do not have any storage space
and merely rely on the network's server for data storage and
processing tasks. The concept of network computers had
become popular in the mid 1990s when several variations of
computers such as Windows terminals, NetPCs, and diskless
workstations were widely used.
Network computers that are specifically designed to access
only the Internet or intranet are often known as Internet PCs
or Internet boxes. Some network computers used in homes
do not even have a monitor. Such computers may be connected to a television, which serves as the output device. The
most common example of a home-based network computer is
Web TV, which enables the user to connect a television to the
Internet. The Web TV is equipped with a special set-top box
that is used to connect to the Internet. The set-top box also
provides controls to enable the user to navigate the Internet,
send and receive e-mails, and to perform other tasks on the
network while watching television. The other reason for the
popularity of network computers is that they are cheaper to
purchase and maintain than PCs.
The mid 1990s witnessed a range of small personal computing devices that are commonly known as handheld computers, Palmtop computers, or Mini-Notebook computers. These
computers are called handheld computers because they can
fit in one hand, while users can use the other hand to operate
them. Handheld computers are very small in size, and hence
Fig. 1.8 Personal digital assistant
Many PDAs are web-enabled, which means that such devices
enable the users to access the Internet and send/receive
e-mails. Similarly, some PDAs also provide telephone
capabilities.
The primary input device of a PDA is the stylus. A stylus
enables the user to interact with the touchscreen to write text
or draw figures. It can be used to write notes. Some PDAs
also support voice input.
Cellular phones These days, cellular phones are webenabled telephones that have features of both analogue and
digital devices. Such phones are also known as smart phones
because, in addition to basic phone capabilities, they also
facilitate the users to access the Internet and send e-mails
and faxes.
H/PC Pro devices The H/PC Pro device (see Figure 1.9) is
based on a new development in handheld technology. The
size and features of the H/PC Pro device is more than PDAs
but less than that of typical notebook PCs. The H/PC Pro
device includes a full-sized keyboard, RAM with very low
storage capacity, and a slow-speed processor. However, these
devices do not have a secondary storage disk.
BASIC COMPUTER ORGANIZATION
A computer is an electronic device that basically performs
five major operations:
Accepting data or instructions (input)
Displaying results (output)
Controlling and coordinating all operations inside a
In this section, we will discuss all these functions and see
how one unit of a computer interacts with another to perform
these operations. Refer to Figure 1.10, which shows the interaction between the different units of a computer system.
Data and
Fig. 1.9 H/PC Pro device
Storage It is the process of saving data and instructions
permanently in the computer so that they can be used for
processing. The computer storage space not only stores the
data and programs that operate on that data but also stores
the intermediate results and the final results of processing.
A computer has two types of storage areas:
Primary storage This, also known as the main memory, is
the storage area that is directly accessible by the CPU at very
high speeds. It is used to store the data and parts of programs,
the intermediate results of processing, and the recently generated results of jobs that are currently being worked on by the
computer. Primary storage space is very expensive and therefore limited in capacity. Another drawback of main memory is
that it is volatile in nature; that is, as soon as the computer is
switched off, the information stored gets erased. Hence, it cannot be used as a permanent storage of useful data and programs
for future use. An example of primary storage is the RAM.
Secondary storage Also known as the secondary memory or
auxiliary memory, this is just the opposite of primary memory. It basically overcomes all the drawbacks of the primary
storage area. It is cheaper, non-volatile, and used to permanently store data and programs of those jobs that are not being
currently executed by the CPU. Secondary memory supplements the limited storage capacity of the primary memory.
An example is the magnetic disk used to store data such as C
and D drives, for future use.
Processing The process of performing operations on the
data as per the instructions specified by the user (program)
is called processing. Data and instructions are taken from the
primary memory and transferred to the arithmetic and logical unit (ALU), which performs all sorts of calculations. The
intermediate results of processing may be stored in the main
memory, as they might be required again. When the processing completes, the final result is then transferred to the main memory. Hence, the data
may move from main memory to the ALU
multiple times before the processing is over.
Output Output is the process of giving
the result of data processing to the outside
world (external to the computer system). The
Flow of data and
results are given through output devices such
as monitor and printer. Since the computer
Control exercised accepts data only in the binary form and
by control unit
the result of processing is also in the binary
form, the result cannot be directly given to
the user. The output devices, therefore, convert the results available in binary codes into
a human-readable language before displaying it to the user.
Control The control unit (CU) is the central nervous system
of the entire computer system. It manages and controls all
the components of the computer system. The CU decides the
manner in which instructions will be executed and operations
performed. It takes care of the step-by-step processing of all
operations that are performed in the computer.
Arithmetic and
logical unit
Fig. 1.10 Block diagram of a computer
Input This is the process of entering data and instructions
(also known as programs) in to the computer system. The
data and instructions can be entered by using different input
devices such as keyboard, mouse, scanner, and trackball.
Note that computers understand binary language, which consists of only two symbols (0 and 1), so it is the responsibility of the input devices to convert the input data into binary
codes.
APPLICATIONS OF COMPUTERS
In the United States, computers are used by the government
for city planning and traffic control. For example, to eliminate the problem of gridlock (when traffic is at total standstill
in an area for 15 minutes), a new system has been designed
that includes induction loops of wire embedded in the asphalt
at many intersections across the city. As cars move over the
wires, electrical pulses are counted by a central computer,
which translates the pulses into the number of cars. It then
converts the number to the rate of flow, and instructs the traffic light when to change. All this information is also used
to predict potential gridlock locations and to send additional
traffic patrols to problem areas.
Computers are used by lawyers to shorten the time required to
conduct legal precedent and case research. Lawyers use computers to look through millions of individual cases and find
whether similar or parallel cases have been approved, denied,
criticized, or overruled in the past. This enables the lawyers to
formulate strategies based on past case decisions. Moreover,
computers are also used to keep track of appointments and
prepare legal documents and briefs in time for filing cases.
When the first computers were developed, they were used
only in the fields of mathematics and science. In fact, the first
effective utilization of computers was for decoding messages
in military applications. Later on, computers were used in
real-time control systems, such as for landing on the moon.
However, with the advancement of technology, the cost of
computers and their maintenance declined. This opened the
way for computers to be extensively used in the business and
commercial sector for information processing. Today, computers are widely used in fields such as engineering, health
care, banking, education, and so on. Let us discuss how computers are being effectively utilized to perform important
Word processing Word processing software enables users
to read and write documents. Users can also add images,
tables, and graphs for illustrating a concept. The software
automatically corrects spelling mistakes and includes copy–
paste features (which is very useful where the same text has
to be repeated several times).
Internet The Internet is a network of networks that connects
computers all over the world. It gives the user access to an
enormous amount of information, much more than available in any library. Using e-mail, the user can communicate
in seconds with a person who is located thousands of miles
away. Chat software enables users to chat with another person in real-time (irrespective of the physical location of that
person). Video-conferencing tools are becoming popular for
conducting meetings with people who are unable to be present at a particular place.
Digital video or audio composition Computers make
audio or video composition and editing very simple. This
has drastically reduced the cost of equipment to compose
music or make a film. Graphics engineers use computers for developing short or full-length films and creating
3D models and special effects in science fiction and action
Desktop publishing Desktop publishing software enables
you to create page layouts for entire books.
After discussing how computers are used in today's scenario, let us now have a look at the different areas where computers are being widely utilized.
ALU, CU, and CPU are the key functional units of a
computer system.
Computers are used in government organizations to keep records
on legislative actions, Internal Revenue Service records, etc.
Note that the CPU is a combination of the ALU and the
CU. The CPU is better known as the brain of the computer
system because the entire processing of data is done in the
ALU, and the CU activates and monitors the operations of
other units (such as input, output, and storage) of the computer system.
Computers are used in retail shops to enter orders, calculate
costs, and print receipts. They are also used to keep an inventory of the products available and their complete description.
In sports, computers are used to compile statistics, identify weak players and strong players by analysing statistics,
sell tickets, create training programmes and diets for athletes,
and suggest game plan strategies based on the competitor's
past performance. Computers are also used to generate most
of the graphic art displays flashed on scoreboards.
Television networks use computers in the control room to
display action replays and insert commercial breaks as per
schedule. Moreover, companies manufacturing sports shoes
such as Nike use computers for designing footwear. They
calculate stress points and then create the style and shape that
offer maximum support for the foot.
In addition, there are simulation software packages available that help a sportsperson to practice his or her skills as
well as identify flaws in the technique.
All computers today have musical instrument digital interface (MIDI) facility, which links musical instruments to a PC,
thereby enabling the computer to generate a variety of sounds.
Moreover, the background music in movies, TV shows, and
commercials are all generated electronically using computers.
proximity to the fault, soil type, size, shape, and construction
material.
Computers are used to create sets, special effects, animations,
cartoons, imaginary characters, videos, and commercials.
Spacecrafts are usually monitored using computers that not
only keep a continuous record of the voyage and of the speed,
direction, fuel, and temperature, but also suggest corrective
action if the vehicle makes a mistake. The remote stations on
the earth compare all these quantities with the desired values,
and in case these values need to be modified to enhance the performance of the spacecraft, signals are immediately sent that
set in motion the mechanics to rectify the situation. With the
help of computers, all this is done within a fraction of a second.
In business and industry, computers are used mainly for data
processing, which includes tasks such as word processing,
analysing data, entering records, payroll processing, personnel record keeping, and inventory management.
When computers are fed with mathematical equations along
with data about air pressure, temperature, humidity, and other
values, the solution of these equations gives an accurate prediction of the weather of a particular area. For example, a
Cray X-MP supercomputer installed at Mausam Bhavan in
New Delhi is used to predict weather and climatic changes in
the Indian subcontinent.
A computer is a powerful teaching aid and acts as another
teacher in the classroom. Teachers use computers to develop
instructional material. Teachers may use pictures, graphs, and
graphical presentations to easily illustrate an otherwise difficult concept. Moreover, teachers at all levels can use computers to administer assignments and keep track of grades.
Besides teachers, most students also prefer to learn from an
e-learning software rather than from a book. Students can
also give online exams and get instant results.
Hospitals use computers to record every information about
patients, from the time of their admission till their exit. For
example, the date, time, reason for being admitted, the doctor being consulted, all prescribed medications, doctor visits,
other hospital services, bills, etc., are all stored in computers. Moreover, computer-controlled devices are widely used
to monitor pulse rate, blood pressure, and other vital signs of
the patient, and in an emergency situation an alarm is used to
notify nurses and other attendants.
Moreover, computers are used as an aid to differently
abled people. For example, computers are used to develop
more effective artificial limbs for amputees.
Dentists also use computers to diagnose jaw misalignments by placing a magnetic square containing three sensors
between the front teeth and lip. The sensors are attached to
a computer; they follow the magnet's movement by tracing
the line on the screen as the patient's mouth opens. If the
jaw moves improperly, the line will bend; else if the line is
straight, the patient just needs to keep flossing.
Computers are used to prepare tickets, monitor the routes
of trains and aeroplanes, and guide planes to a safe landing.
They are also used to research about hotels in an area, reserve
rooms, or to rent a car.
Supercomputers that can process enormous amount of data
are widely used in simulation tests. Simulation of automobile
crashes or aeroplane emergency landings is done to identify
potential weaknesses in designs without risking human lives.
Supercomputers also enable engineers to design aircraft
models and simulate the effects that winds and other environmental forces will have on those designs. Even the astronauts
at NASA are trained using computer-simulated problems that
could be encountered during the launch, in space, or upon
re-entry in to the earth's atmosphere.
Civil engineers use computers to evaluate the effects of
an earthquake on the structure of buildings based on age,
The world today is moving towards a cashless society, where
you need not have money in your pocket to purchase anything. You can just have your credit card or debit card with
you. The ATMs provide a 24 × 7 service and allow you to
draw cash, check the balance in your account, and order a
Industry and Engineering
Computers are found in all kinds of industries, such as thermal power plants, oil refineries, and chemical industries, for
process control, computer aided designing (CAD), and computer aided manufacturing (CAM).
Computerized process control (with or without human
intervention) is used to enhance efficiency in applications
such as production of various chemical products, oil refining,
paper manufacture, and rolling and cutting steel to customer
In CAD, computers and graphics-oriented software are
integrated for automating the design and drafting process.
It helps an engineer to design a 3D machine part, analyse its
view the trends in the market, and predict the future of
their products. Managers also use decision support systems
to analyse market research data, to size up the competition, and to plan effective strategies for penetrating their
markets.
characteristics, and then subject it to simulated stresses. In case
a part fails the stress test, its specifications can be modified
on the computer and retested. The final design specifications
are released for production only when the engineer is satisfied
that the part meets strength and other quality considerations.
The CAM phase begins when the CAD phase is complete.
In this phase, the metal or other materials are manufactured
while complying with their specifications. For this computer
controlled manufacturing, tools are used to produce highquality products.
• First-generation computers used a very large
instructions and performs computations based on
those instructions.
Today, computers are used in all interactive devices,
such as cellular telephones, GPS units, portable
organizers, ATMs, and gas pumps, among
A computer accepts data, processes it, and
produces information. Here, data is some raw facts
or figures, and information is the processed
The speed of the computer is usually given in
nanoseconds and picoseconds.
The term computer generation refers to the different
advancements of new computer technology. With
each new generation of computers, the circuitry
became smaller and more advanced than that in its
previous generation.
number of vacuum tubes for circuitry and magnetic
drums for memory. Second-generation computers
were manufactured using transistors rather than
vacuum tubes.
• The development of the integrated circuit was the
hallmark of the third-generation computers. The
microprocessor started the fourth generation of
computers, with thousands of integrated circuits
built onto a single silicon chip. The fifth-generation
computers are completely based on the new
concept of AI.
• The CU is the central nervous system of the entire
computer system. It manages and controls all the
components of the computer system.
• The CPU is a combination of the ALU and the CU.
The CPU is better known as the brain of the
Computer An electronic machine that takes instructions and performs computations based on those
GUI A type of user interface that enables users to
interact with programs in more ways than typing. A
GUI offers graphical icons and visual indicators to
display the information and actions available to a user.
The actions are performed by direct manipulation of
the graphical elements.
Program A set of instructions executed by the
• A computer is an electronic machine that takes
Computers help managers to analyse their organization's
data to understand the present scenario of their business,
Expert systems are used to automate the decision-making
process in a specific area, such as analysing the credit histories for loan approval and diagnosing a patient's condition for
prescribing an appropriate treatment. Expert systems analyse
the available data in depth to recommend a course of action.
A medical expert system might provide the most likely diagnosis of a patient's condition.
To create an expert system, an extensive amount of human
expertise in a specific area is collected and stored in a database, also known as knowledge base. A software called an
interface engine analyses the data available in the knowledge
base and selects the most appropriate response.
Adding more to it, in today's scenario, computers are used
to find jobs on the Internet, find a suitable match for a boy or
girl, read news and articles online, find your batch mates, send
and receive greetings pertaining to different occasions, etc.
Robots are computer-controlled machines mainly used in the
manufacturing process in extreme conditions where humans
cannot work, for example, in high-temperature, high-pressure
conditions or in processes that demand very high levels of
accuracy. The main distinguishing feature between a robot
and other automated machines is that a robot can be programmed to carry out a complex task and then reprogrammed
to carry out other complex tasks.
Vacuum tube A device sometimes used to amplify
electronic signals.
Semiconductor devices Electronic components that
make use of the electronic properties of semiconductor materials (e.g., silicon, germanium). The
conductivity of such devices can be controlled by
introducing an electric field, by exposure to light, and
even pressure and heat, thereby making such devices
excellent sensors.
Transistor A semiconductor device that is used to
amplify and switch electronic signals. Although some
transistors are packaged individually, others are usually found embedded in ICs.
Integrated circuit Also called a chip or microchip,
an IC is a semiconductor wafer on which thousands
or millions of tiny resistors, capacitors, and transistors are fabricated. It can be used as an amplifier, oscillator, timer, counter, computer memory, or
microprocessor.
Garbage-in, garbage-out If input data is wrong, then
the output will also be erroneous.
Expert systems Custom-written computer programs
that are 'expert' in a particular problem area, and
embody a human expert's knowledge, experience,
and problem-solving strategies. They are being used
in many areas such as medicine, chemistry, geology,
meteorology, computer systems, and so on.
Neural networks Systems that simulate intelligence
by reproducing the physical connections that takes
place in animal brains.
Robotics Computers programmed to look, listen, and
Stylus An electronic pen that looks like a small ballpoint pen.
Internet A network of networks that connects computers all over the world.
Storage The process of saving data and instructions
permanently in the computer so that it can be used for
processing.
Input The process of entering data and instructions
into the computer system.
Memory shadow The process of copying data from
CMOS into RAM.
1. A program is the ________.
2. Computers operate on ________ based on
3. Computers can perform ________ calculations in
a second.
4. The speed of computers is expressed in ________
or ________.
5. Raw facts or figures are called ________.
6. ________ is an example of primary memory.
7. ________ and ________ are examples of first-generation computing devices.
8. Second-generation computers were first developed for the ________ industry.
9. ________ packages allow easy manipulation and
analysis of data organized in rows and columns.
10. CRAY-1, CRAY-2, Control Data CYBER 205, and
ETA A-10 are ________.
11. ________ enables the television to use a telephone line to communicate and connect to the
1. The first commercial computer delivered to a
business client is:
(a) UNIVAC
(b) ENIAC
(c) EDSAC
2. The technology used in the manufacture of secondgeneration computers is:
(a) Vacuum tubes
(b) Transistors
(c) ICs
3. The generation of computers in which time sharing operating systems were used is:
(a) First
(b) Second
(c) Third
(d) Fourth
4. The computer languages that are specially
designed for the fifth generation of computers are:
(a) ALGOL
(b) SNOBOL
(c) LISP
(d) Prolog
5. Web TV is an example of:
(a) Supercomputer
(b) Minicomputer
(c) Network computer
(d) Laptop
6. The brain of the computer is the:
(a) Control unit
(b) ALU
(c) CPU
1. Computers work on the GIGO concept.
2. 1 nanosecond = 1 × 10−12 seconds.
3. Floppy disk and hard disk are examples of primary
4. First-generation computers used a very large
number of transistors.
1. Define a computer.
2. Differentiate between data and information.
3. Differentiate between primary memory and secondary memory.
4. Write a short note on the characteristics of a
5. Computers work on the garbage-in, garbage-out
concept. Comment.
6. Explain the evolution of computers. Also, state
how computers in one generation are better than
their predecessors.
7. Broadly classify computers based on their speed,
the amount of data that they can hold, and price.
8. Discuss the variants of microcomputers that are
widely used today.
9. Explain the areas in which computers are being
applied to carry out routine and highly specialized
5. First-generation computers could be programmed
only in binary language.
6. ALGOL is used in the third-generation computers.
7. Fifth-generation computers are based on AI.
8. Network computers have more processing power,
memory, and storage than a desktop computer.
9. RAM stores the data and parts of program, the
intermediate results of processing, and the recently
generated results of jobs that are currently being
worked on by the computer.
10. Operating systems such as MS-DOS, Windows,
and UNIX were introduced during the fourth generation of computers.
In order to accomplish tasks, a computer must be able to interact with its users. For this purpose,
we need input and output devices, which are also known as peripheral devices. There are different types
of input/output devices, and each device has capabilities that differentiate it from the others. In this
chapter, we will read about some peripheral devices that are widely used these days.
devices. Figure 2.1 categorizes input devices into different
An input device is used to feed data and instructions
into the computer. In the absence of an input device, a
computer would have only been a display device. In this
section, we will read about some of the widely used input
2.1.1 Keyboard
The keyboard is the main input device for computers.
Computer keyboards look very similar to the keyboards of
Pointing devices
Audio/Visual devices
Fig. 2.1 Categories of input devices
Oxford Cancer Centre Well the new Cancer Centre is very special, it has brought together for the very first
1 The following is a selection of reading which represents different
TABLE S1: Population sizes and transmission coefficients (WAIFW
Operating Systems Draft
Exam Study Guide
Chapter_01
Mobile Communication – An overview Mobile System Networks
References - Marquette University


text:
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redpajama_set_name: RedPajamaCommonCrawl


Protecting our patients and visitors is our top priority. That's why public safety officers at Tufts Medical Center patrol the hospital 24 hours a day. Here's how we handle public safety and security.
From 8 pm Friday to 6 am Monday, all individuals coming to the Medical Center at street level should enter through the Emergency Department, 830 Washington Street.
The Atrium Lobby doors from Washington and Bennet streets will be locked.
Floating Hospital street-level access is open from 7 am–1 pm on Saturday only to allow access to Floating clinics and the MRI.
The Biewend Building Lobby and entrance to Biewend from the main hospital/3rd floor crossover will be open for access to Biewend clinics from 6 am–1 pm on Saturday only.
For those who use wheelchairs, strollers or are mobility-challenged they should take the garage elevator to Floating Plaza and use the phone next to the Floating Plaza Level entrance to call Public Safety who can buzz them in.
Others can follow the same instructions above or can take the elevators to the Plaza or Ground Level depending on the elevator bank they use, and then cross the street to enter through the Emergency Department, 830 Washington Street.
From 6 am–1 pm Saturday, patients and visitors can use the 3rd Floor crossover garage entrance (stairs) to allow access to clinics.
All pediatric units are locked at all times. To enter, please ring the doorbell at the entrance of the unit and let staff know who you are and whom you are visiting.
Patients are encouraged to leave all valuables at home. Patients wishing to secure valuables during their stay may do so by requesting that medical staff contact Public Safety. Public Safety has a property protocol in place and a facility for storage.
For non-urgent calls, call Public Safety at 617-636-7700. In an emergency only, you may reach Public Safety 24 hours a day by calling 617-636-5100.


I had fun telling the story of my latest creation--flannel pyjama bottoms through scary halloween photoboards! For a less ghoulish write-up of the construction, click here. Hope you enjoy!
One spooky bat, two spooky bats, three spooky bats! waaahaaahaaahhaaa!
Best. Post. Ever. LOL Those would be great pj's for snuggling in front of the tv with a classic horror flick playing!
What a hooot, so to speak!
Was waiting for this post on your blog, having seen it on Sew Weekly - but no way was I prepared for this! Big laughs all round! And your PJs do look the business too!
Hahah, the last one cracked me up!


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After further review I've decided to change course in my reading of the Great Books for two reasons. One, there are 474 books/works in the series, and at one per week that would take me about 9 years. I don't have the health or longevity at this point to commit to that, whole-hog. Two, my chronic fatigue gives me very little energy to do really heavy reading, and if I give an hour a day to the Great Books, I have little left for heavy theology and Biblical studies. I find it best to do that heavy reading in focused bursts, according to my energy levels and topical interests.
I think an exhaustive, slow reading of these great books is best left to future Adam. Once I am more widely read and more intellectually mature, I will be better prepared to make decisions to skip certain sections while focusing on those more important. I recognize my own inability and don't think I have the complete discernment to make those decisions yet, at the level required to get all I can from the set.
So my goal isn't to exhaust the set but to peruse it topically and learn organically as I discover new connections and ideas that inspire me. This leaves me free to explore and free to back totally off and just do light reading if I need to rest for a few days.
I will post at least once per week on some big idea from the books and will include a quote I found enlightening in my research. Each of these posts will still be tagged "The Great Books" so you can see them all aggregated there.
The point: you will be seeing much more randomness as I pull key concepts from across multiple disciplines as I find things that inspire me and educate me in some way. The model I'm shooting for is something like Maria Popova's incredible site, Brainpickings and Shane Parrish's FarnamStreetBlog. Instead of a few long-form treatments, you will get many single ideas, plus a few long-forms as I continue to produce essays and reviews.
Also, I have been recruited to review some books for a couple Christian publishing houses, so you will see more classic book reviews as I work through those. My goal, as always, is to put quality material in your face, and these changes are a necessary next-step as I grow into that effort.
Another change in blog content will be in a new focus: technology for Academics and students. I hope to post a whole series on that, so if you find it unhelpful, skip them. My hope is that as I build a base of posts on it I can spread that around and help many online who seriously need help doing research and staying above water. God has given me some time the past couple years for me to just sit still and hammer these things out, so I hope to communicate that as well.
I am beginning to focus on compiling the curriculum for my current Sunday School class into book form for potential publishing. I will probably post snippets of that from time to time. I covet your feedback and interaction, and your prayers.
I write lots of fiction, but post none online. I think as I continue to hone my skills, I will post some short stories to the blog as well. Again, feedback is encouraged!
I will post updates as they come, but for now, I'm still planning this project and hope to come to a conclusive mission statement and vision very soon.
Thank you for reading my little blog!


Naturally with Puggie and Missy being such wonderful and devoted pets, or should I say children, we wanted to expand the family to include the pitter patter of little Pug puppies. Missy was a good choice for a Mother as she was very loving. We went in search of a good stud to breed her to and found one in Pennsylvania, a champion show Pug, Ch. Sheffield's Fortune Teller. With the stud selected we made the trip to Pennsylvania to breed her and then waited and waited and waited some more. We were never really sure that the breeding was a success until the day she delivered, and that was a total surprise to us. We'd even seen our vet and she couldn't confirm for us that Missy was pregnant, but she was.
Then, on the afternoon of November 23, 1981, I returned home to pack for a short business trip to Chicago. When I entered the house and inquired of Anne where Missy was she informed me that she was sleeping in. I went upstairs to the bedroom to pack and Missy was indeed curled up on Anne's pillow sleeping. I took a quick shower and when I returned to the bedroom I almost fell over. Missy was cleaning her first born puppy. I quickly got on the phone to the vet to find out what we should do. She informed us to just sit back and wait for the others to arrive and to assist Missy with the cleaning after the puppies were born.
Within the hour the second puppy was born and some time later the third. Poor Missy was exhausted by the time the third puppy was born and it fell on me to clean the puppy and make sure it was breathing. These puppies were just a little larger than a good size mouse and totally helpless, but Missy kept a watchful eye out for them and immediately proved she would be a good Mother.
I have to admit, Missy did a lot better handling the birth than I did. I was a nervous wreck throughout the whole process and totally exhausted by the time the third one was born. I was also worried to death that the puppies wouldn't make it because they were so tiny and helpless. I quickly changed my travel plans to an early flight the next morning deciding to stay home and make sure they were being well taken care of by Missy. That was probably a mistake because I didn't get a wink of sleep the entire night and left at 5 a.m. for my flight to Chicago. Needless to say I was exhausted the entire day in Chicago, but I managed to make it home that evening to find Mother and puppies thriving. It was difficult, almost impossible, to resist the urge to pick them up and cuddle them, but I knew they shouldn't be handled to much and left them alone.
Missy was indeed a good Mother. Very doting and attentive to her puppies. As you can see by the picture (left) she even allowed one of the new kittens in the house to share the puppies box. It was a happy time then watching the little puppies grow, open their eyes and begin to explore the new world around them. It wasn't long before they were crawling out of the box and all over the house.
Just a few weeks after the puppies were born Christmas arrived and what a wonderful time they had discovering the tinsel hanging from the tree and the presents strewn beneath it. They use the presents to learn how to mountain climb, and the tinsel to play tug of war.
With Christmas came lots of opportunities to take some cute pictures of the puppies. I couldn't resist placing them in the basket and snapping away. They couldn't resist never looking in the same direction at the same time.
When the puppies where first born we weren't sure what we were going to do with all of them. We knew we'd keep one and another would go to my Mother and Father, but what about the third one.
With the uncertainty of who was going, who was staying, we didn't immediately name the puppies. Playing it safe, we simply called them names relating to their birth order. Number One, Two and Three. Number One and Three were the best looking Pug puppies with all the traditional markings. Number Two was not the best, but she quickly grew on our affections. She was actually the first to be named. We called her Tu Tu. She loved to run and play.
It was apparent after a short time that none of these puppies would ever leave the family. The only question that remained was which one would be give to my Mother and Father? For that answer we returned to the breeder to get their opinion as to which one was the best representation of the Pug breed. The answer was puppy Number One who was named Missy's Lady Beaujangles, or "Beau" for short. Number Three became Missy's Little Chrisy, or "Chrisy" for short.
With three puppies running wild under the Christmas tree it was always nice when they got tired and went to sleep. Here one, Chrisy (right), is just about asleep while Beau gnaws on an ear and Tu Tu looks for a nice place to rest her head and go to sleep. It looks like Chrisy's back is going to be the perfect place to take that nap. It was cute watching them cuddle up this little Koala bear stuffed toy as if it was Missy. They enjoyed every minute.
Missy truly was a good mother to the little puppies. She looked after their every need and at feeding time managed to accommodate three hungry Pug puppies. Anyone who knows anything about Pugs knows that food is top on their priority list and nothing will stop them from getting their fill. Missy eagerly accommodated them and watched them with a doting eye. Fed well they grew fast and were soon lapping up dog food.
As with children, puppies, too, are always playful and it takes a strong, loving hand to manage them. Missy offered that strong, loving hand when her puppies got a bit rambunctious.
Here Missy gives Chrisy a stern talking to, not that she really needed it.
Times were not always rowdy with the puppies. Quite often things would quiet down and one of the puppies, here it's Tu Tu, would cuddle up with Missy for a few moments of tender loving care.
Having the puppies was a wonderful experience. Anyone who loves Pugs would enjoy the experience. Watching them grow from totally helpless puppies into full grown Pugs brought much joy to our family and is something we will never forget.


Relying upon a qualified spiritual guide is the very heart of the Buddhist path to enlightenment, the root of all our spiritual attainments. In our daily life we rely upon many people's expertise and advice. Following the spiritual path is no different. We need to learn how to follow a spiritual guide sincerely and with strong faith, putting their instructions into practice correctly so that we can achieve the same results.
Everyone is welcome to join us at 2:30pm, for Offering to The Spiritual Guide Puja - an opportunity to experience this deeply meaningful and joyous practice.
Recordings of the morning teachings and guided meditations are available to pre-order (save 25%) or on the day.
Please note that if attending all day, lunch is not provided. There are many outlets nearby on Mutley Plain if you wish to obtain lunch. Please ask if you need advice about where to eat.