Hari Bahadur Khadka
Master of Science in Information System Engineering,
Purbanchal University
Ramesh Kunwar
Master in Computer Application (MCA) 2002,
India
Advance Saraswati Prakashan
Kathmandu, Nepal.
Published by : Advance Saraswati Prakashan Pvt. Ltd.
Kathmandu, Nepal
Phone: 01-4780359, +977-9851176247
E-mail: [email protected]
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Edition : 2020
Text © reserved by Authors: Design, Layout and Formatting reserved by Publishers.
Price : Rs. 665/-
ISBN : 978-9937-744-25-6
Distributed by : Advance Saraswati Prakashan Pvt. Ltd.
Kathmandu, Nepal
Phone: 01-4780359, 01-4241247, +977-9843262646
Printed in Kathmandu.
Q!S!F!G!B!D!F!
!
This book, Computer Science- XI, is written for the students of Grade XI of Secondary
Education Board of Nepal. Our aim in preparing this book has been two folds. First, we have
written a study course prescribed by the Secondary Education Board that students are preparing for
the exams can approach on their own. Second, we present a thorough presentation for future
computer users' people with alternative knowledge for every day to acquire the skill and information.
Every bit of the content area has been covered in detail, and the language has been kept as simple as
possible to make the idea clear.
The world has been transformed into a small global village, where everyone on any corner is within
the reach of every other. Information and Communication Technology (ICT) has emerged as the key
ingredient of every activity. Information is considered as a strategic resource in the same manner as
the capital, human resource, or the machine. Every second, a bunch of information is being
generated, processed, communicated, and stored. It has changed the world economy into a
knowledge based economy rather than agro or industrial. ICT has created limitless opportunities for
creativity and applications from home to space exploration; and the computer is on the driving seat
of all of these.
With a distinct focus to encompass the objectives of this book, contents have been presented in a
very simple, clear, and precise style. It is prepared with the consideration of student's knowledge
along with the following features:
Examples: Presented in every topic and chapter as far as possible will help readers to know
the subject matter to be very clear.
Tables, Pictures, and Figures: Presented in every topic and chapter as far as possible will help
readers to know the subject matter to be very clear.
Summary: Listed at the end of every chapter will help readers to understand easily about the
chapter in a very short form.
Exercise: Presented in the book with a related topic will give a clear vision about the
scenario.
Activities: Presented in the book with a related chapter will help the readers to provide a
clear vision about the scenario.
We would like to acknowledge all the known and unknown source of images incorporated in this
book. We are extremely grateful to our family, friends, colleagues, relation, and all the students who
have encouraged and inspired directly and indirectly to write this book. We would like to thank the
team of Advance Saraswati Prakashan for their support in publishing this book.
Finally, we would like to take responsibility for any remaining errors and welcome valuable
suggestions and criticisms for the improvement of the book.
Authors
2020
SYLLABUS
Secondary Education Curriculum 2076
Computer Science
Grades: 11 Subject code: Com. 231
Credit hrs: 5 Working hrs: 160
1. Introduction
The world has witnessed a radical change in the field of Information and Communication Technology (ICT) in recent and
this process is still going on. The relevance of computer education has been increasing day by day. Realizing the same the
curriculum of computer science for Grades 11 and 12 has been developed according to the National Curriculum
Framework, 2076. The study of this course will help the students to enter the job market. This will also provide basis for the
students to pursue their further study in the field.
This curriculum comprises of an introduction to basic computer system, the basic number system and Boolean logic,
computer software and operating system, application package, multimedia and network. It also includes contents of web
technology, programming, information security and cyber law, digital society and computer ethics and recent trends in ICT.
The course itself is of practical nature and the pedagogical approaches in delivering the course should consider the balance
between theory and practice. The same applies in case of student evaluation proceduretoo.
The curriculum has been divided to different sections: level-wise competences, grade-wise learning outcomes, scope and
sequence of contents with their elaboration, some indication to learning facilitation process and student assessment.
2. Level-wise competencies
1. Relate principles of computer system including input, process, output and storage devices, Boolean logic and number
system.
2. Use operating system, word processor, spread sheet and apply in real-life and educational contexts.
3. Design website using new web technologies.
4. Demonstrate the programming concept and logic into software development process.
5. Use Database concept in basic SQL level.
6. Apply networking concept into LAN and wireless network.
Define OOPs concept and trace the recent trends of technological enhancement in 21st century.
3. Scope and Sequence of Contents
S. N. Content Area Elaboration of Contents Working Hour
1. Computer system 1.1 Introduction of computer 20
1.1.1 Definition, characteristics and application of computer
1.1.2 Evolution of computer technology
1.1.3 Measurement unit of processing speed and storage unit
1.1.4 Super, Mainframe, Mini and Microcomputers
1.1.5 Mobile Computing and its Application
1.2 Computer system and I/O devices
1.2.1 Concept of computer architecture and organization
1.2.2 Components of computer system: input unit, output unit,
processing unit, memory unit and storage
1.2.3 Microprocessor: basic concepts, clock speed, word length,
components and functions
1.2.4 Bus System: data bus, address bus and control bus
1.2.5 Primary memory: Definition, RAM, ROM, Cache, Buffer, types
of RAM and ROM
1.2.6 Secondary Memory: Definition, Magnetic Disk, Flash Memory,
Optical Disk, External Storage Device and memo stick
1.2.7 Input Devices – Keyboard, Mouse, Scanner, Light Pen, OMR,
OCR, BCR, MICR, Scanner, Touch Screen, Microphone and
Digital Camera.
1.2.8 Output Devices: Monitor (LCD, LED), Printer (Dot Matrix,
Inkjet, Laser), Speaker
1.2.9 Hardware Interfaces: Parallel Port, Serial Port, USB Ports,
HDMI and Expansion Slots
2. Number system and 2.1 Number System and conversion 11
12
conservation 2.1.1 Decimal, Binary, Octal, Hexadecimal Number System &
Boolean Logic conversion
2.1.2 Calculation in binary addition, subtraction
2.1.3 One’s and Two’s complement methods of binary
subtraction
2.2 Logic Function and Boolean Algebra
2.2.1 Introduction to Boolean algebra
2.2.2 Introduction to Boolean values, truth table, Boolean
expression and Boolean function.
2.2.3 Logic Gates –AND, OR, NOT, NAND, NOR, XOR and
XNOR – its definition, truth table, logic symbol, logic
function
2.2.4 Laws of Boolean algebra – Boolean identities,
Complement Laws, Identity, Commutative, Associative
and Distributive
2.2.5 Statement and verification of Laws of Boolean algebra
using truth table
3. Computer Software 3.1 Concept of Software
and Operating 3.1.1 Definition of software
System 3.1.2 Categories of software: System, Utility, Application, Web
Based, Mobile Apps
3.2 Concept of Operating System
3.2.1 Introduction to Operating System
3.2.2 Role of Operating System
3.2.3 Functions of an Operating System
3.2.4 Operating system terminology: multiprogramming,
multitasking, multiprocessing and distributed
3.3 Windows Operating System
3.3.1 Introduction to GUI based Operating system and its features
3.3.2 Working in Desktop Application and Window Environment
3.3.3 Manage Files and Folders with File Explorer
3.3.4 Customize the start screen and desktop
3.3.5 Installing and removing devices
3.3.6 Manage passwords and privacy levels
3.3.7 Use of control panel, system tools and accessories
3.4 Open sources and Mobile Operating System
3.4.1 Concept of Open Sources Operating System
3.4.2 Introduction to Linux and UNIX
3.4.3 Linux Distributions
3.4.4 Concept of Mobile Operating System
3.4.5 Types of Mobile Operating System
4. Application Package 4.1 Introduction to Office Package - Word processor, Presentation 5
tool, spreadsheet package, database management system; 8
4.2 Introduction to domain-specific tools - school management system,
inventory management system, payroll system, financial
accounting, hotel management, weather forecasting system.
5. Programming 5.1 Programming Concept
Concepts & Logics 5.1.1 Introduction to programming languages
5.1.2 Low level, High level, 4 GL programming languages
5.1.3 Compiler, Interpreter and Assembler
5.1.4 Syntax, Semantic and Runtime errors
5.1.5 Control Structures: Sequence, Selection and Iteration
5.1.6 Program Design tools – Algorithm, Flowchart and
Pseudocode
5.1.7 Absolute binary, BCD, ASCII and Unicode
5.2 C Programming Languages
5.2.1 Introduction and features of C Language
5.2.2 Structure of C program
5.2.3 C Preprocessor and Header Files
5.2.4 Character Set used in C
5.2.5 Use of Comments
5.2.6 Identifiers, Keywords and Tokens
5.2.7 Basic Data Types in C
5.2.8 Constants and Variables
5.2.9 Type of Specifier
5.2.10 Simple and Compound Statements
5.2.11 Operators and Expressions: arithmetic, relational, logical,
assignment, unary and conditional operators
5.2.12 Input/output (I/O) Functions
5.2.13 Selection Control Statement: Decisions (if, if-else, if-else-if,
nested and, switch)
5.2.14 Iteration Control Statement: Looping (while, do while, for
nested)
5.2.15 Array: definition, types(1D and 2D), matrix addition and
subtraction
5.2.16 String: definition and string function
5.2.17 Strlen(), strcat(), strcmp(), strrev(), strcpy(), strlwr(), strupr()
6. Web Technology I 6.1 Introduction: Web development introduction 8
6.2 Web browsers and search Engines
6.3 Overview of various internet & web technologies
6.4 Content Management System (CMS)
6.4. HTML: The Language of the Web
6.4.1 Objectives
6.4.2 Structure of HTML
6.4.3 Published and Hosting
6.4.4 HTML Tags vs. Attributes
6.4.5. Basic Tags of HTML: HTML, HEAD, TITLE, BODY
(Setting the Fore color and Background color, Background
Image, Background Sound)
6.4.6 Heading tag (H1 to H6) and
attributes(ALIGN),
6.4.7 FONT tag and Attributes (Size: 1 to 7 Levels,
BASEFONT, SMALL, BIG,COLOR)
6.4.8 Paragraph Formatting (P)
6.4.9 Break Line BR
6.4.10. Comment in HTML (<! >)
6.4.11. Formatting Text (B, I, U, Mark, Sup, Sub, EM,
BLOCKQUOTE, PREFORMATTED)
6.4.12. Ordered List- OL (LI, Type- 1, I, A, a; START,VALUE)
6.4.13. Unordered List - UL (Bullet Type- Disc, Circle, Square,
DL, DT, DD)
6.4.14 ADDRESS Tag
• Creating Links: Link to other HTML documents or
data objects
• Links to other places in the same HTML documents
• Links to places in other HTML documents
• Anchor Tag and Hyperlink
6.4.15. Tables: Creating Tables using TH, TR and TD tags
6.4.16 Forms: Creating form using Textbox, radio,
checkbox, text area, button
6.4.17 Introduction to HTML 5 Elements including audio,
embed, source, track and video attributes
6.4.18 HTML 5 Graphics using canvas and svg tags
6.4.19 Concept of domain name and web hosting
6.5 Cascading Style Sheets
6.5.1 Introduction to Cascading Style Sheet (CSS)
6.5.2 Inline CSS
6.5.3 Embedded CSS
6.5.4 External CSS
7. Multimedia 7.1 Introduction to Multimedia 6
10
7.2 Component of Multimedia: Text, Graphics, Audio, Video and
Animation 80
7.3 Application of Multimedia
8. Information Security 8.1 Digital society and computer ethics
and Cyber Law 8.2 Concept of Information security
8.3 Concept of Cybercrime
8.4 Malicious software and Spam
8.5 Protection from cybercrime
8.6 Intellectual Property Right
8.7 Concept of Digital Signature
8.8 Concept of Cyber Law in Nepal
8.9 ICT Policy in Nepal
Total
a) Suggested project work
Grade-wise sample project works are suggested below.
1. Prepare basic computer system devices and peripheral specifications of your personal computer.
2. Write a report on "Major cyber bullying in Nepal" with real examples and suggest the preventing measures
3. Conduct a survey to identify the popular search engines (any 5) and its features.
4. Develop the real life project on Office Package or web technology
6. Learning Facilitation Method and Process
Students should be facilitated to learn rather than just helping them to accumulate information.. Student centered
teaching-learning process is highly emphasized in delivering this course. Students are supposed to adopt multiple
pathway of learning such as; online search, field visit, library work, laboratory work, individual and group work, research
work etc. with the support of teacher. Self-study is highly encouraged and learning should not be confined to the scope of
curriculum. Teacher should keep in mind intra and inter-disciplinary approach to teaching and learning, as opposed to
compartmentalization of knowledge. Supportive role of parents/guardians in creating conducive environment for
promoting the spirit of inquiry and creativity in students' learning is anticipated. The following methods and techniques will
be adopted in delivering this course.
• Practical/application/experimental methods
• Laboratory based practical works
• Project work methods (Research work i.e. survey and mini research, innovative work or experiential learning,
connection to theory and application)
• Lecture
• Interaction
• Question answer
• Demonstrations
• Online based instructions
• Cooperative learning
D!P!O!U!F!O!U!T!
! !!!!!!!!!!!!!Voju!2; !Dpnqvufs!Tztufn! !
Introduction.......................................................................................................................................................... 2
Characteristics of computer ............................................................................................................................... 3
Application of computers................................................................................................................................... 4
Education........................................................................................................................................................ 5
Entertainment ................................................................................................................................................ 5
E-Commerce................................................................................................................................................... 5
Health Care..................................................................................................................................................... 6
Science and Engineering............................................................................................................................... 7
Publishing....................................................................................................................................................... 7
Traveling......................................................................................................................................................... 8
Government and E-Governance.................................................................................................................. 8
Home ............................................................................................................................................................... 8
Agriculture ..................................................................................................................................................... 9
Energy ............................................................................................................................................................. 9
Industry........................................................................................................................................................... 9
Evolution of Computer....................................................................................................................................... 9
Pre- History Era or Pre- Mechanical Era (500BC-1642) ......................................................................... 10
Mechanical Era (1642-1890)........................................................................................................................ 11
Electro-mechanical era (1890 – 1945) ........................................................................................................ 13
Electronic era (1946-present)...................................................................................................................... 15
Generations of Computers ......................................................................................................................... 17
Computer Speed And Measurement Unit..................................................................................................... 23
Bit Width....................................................................................................................................................... 23
Clock Cycles ................................................................................................................................................. 23
Execution Cores ........................................................................................................................................... 23
CPU Speed Measurements......................................................................................................................... 24
Bandwidth .................................................................................................................................................... 24
Storage Unit.................................................................................................................................................. 24
Classification of Computer .............................................................................................................................. 25
Microcomputer ............................................................................................................................................ 25
Minicomputers............................................................................................................................................. 26
Mainframe Computers ............................................................................................................................... 27
Supercomputer ............................................................................................................................................ 27
Mobile Computing ............................................................................................................................................ 28
Computer Architecture and Organization .................................................................................................... 30
Computer Architecture............................................................................................................................... 30
Computer Organization ............................................................................................................................. 32
Components of Computer System.................................................................................................................. 32
Input Unit ..................................................................................................................................................... 33
Central Processing Unit (CPU).................................................................................................................. 33
Memory......................................................................................................................................................... 34
Output Unit .................................................................................................................................................. 35
Microprocessor .................................................................................................................................................. 35
Concepts of system buses................................................................................................................................. 37
Memory............................................................................................................................................................... 38
Primary Memory ......................................................................................................................................... 39
Buffer ............................................................................................................................................................. 42
Secondary Memory ..................................................................................................................................... 42
Blu-ray Disc .................................................................................................................................................. 48
External Storage Devices ............................................................................................................................ 49
Input and Output Devices ............................................................................................................................... 50
Input Devices ............................................................................................................................................... 50
Output Devices ............................................................................................................................................ 57
Computer Peripherals....................................................................................................................................... 65
Interfaces............................................................................................................................................................. 65
Serial port...................................................................................................................................................... 66
Parallel Port .................................................................................................................................................. 66
Universal Serial Bus (USB)......................................................................................................................... 67
IEEE 1394 ...................................................................................................................................................... 67
Network Interface Cards (NIC)................................................................................................................. 68
Personal System 2 (PS/2) ........................................................................................................................... 68
HDMI ............................................................................................................................................................ 68
Expansion slots ............................................................................................................................................ 69
SUMMARY ................................................................................................. 70
EXERCISE ................................................................................................... 71
WRITE SHORT NOTES ........................................................................... 72
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Number System ................................................................................................................................................. 74
Decimal (Denary) System........................................................................................................................... 74
Binary Numbering System......................................................................................................................... 75
Octal Numbering System ........................................................................................................................... 75
Hexadecimal Numbering System ............................................................................................................. 76
Binary Calculation....................................................................................................................................... 77
Radix (Base) Conversion ............................................................................................................................ 78
One’s and two’s Complement Methods for Binary Subtraction.............................................................. 84
Boolean logic ...................................................................................................................................................... 86
Introduction.................................................................................................................................................. 86
Boolean Algebra .......................................................................................................................................... 86
Truth Table and Boolean Expression........................................................................................................ 88
Boolean Values and Boolean Functions ................................................................................................... 89
Logic Gates ................................................................................................................................................... 91
Laws of Boolean Algebra ........................................................................................................................... 98
De Morgan's Theorem .............................................................................................................................. 100
SUMMARY .............................................................................................. 104
EXERCISE ................................................................................................ 105
ACTIVITIES ............................................................................................ 106
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Software and its Classification ...................................................................................................................... 108
Types of Software ...................................................................................................................................... 108
Operating System ............................................................................................................................................ 113
A Brief Operating System History (Etymology)................................................................................... 113
Introduction to Fundamental Concept of Operating System ............................................................. 114
Role of Operating System......................................................................................................................... 115
Functions of an Operating System.......................................................................................................... 116
Booting ........................................................................................................................................................ 121
Buffering ..................................................................................................................................................... 122
Spooling ...................................................................................................................................................... 122
Virtual Memory ......................................................................................................................................... 122
Windows (GUI) Based Operating System ................................................................................................... 123
Features of GUI.......................................................................................................................................... 123
Desktop Application and Windows Environment..................................................................................... 125
Working with a Windows Application Programs...................................................................................... 130
Adding and Removing Programs........................................................................................................... 130
Starting and Quitting a program............................................................................................................. 130
Working with Files and Folders.............................................................................................................. 130
Customizing the Taskbar and Desktop.................................................................................................. 131
Install and Remove the devices............................................................................................................... 133
Manage password and privacy ............................................................................................................... 135
Customizing Windows............................................................................................................................. 136
Use control panel, system tools and accessories................................................................................... 137
Concepts of Open Sources Software....................................................................................................... 140
Linux Distribution........................................................................................................................................... 147
Mobile Operating Systems (Mobile OS)................................................................................................. 149
SUMMARY .............................................................................................. 151
EXERCISE ................................................................................................ 153
ACTIVITIES ............................................................................................ 154
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Application Package ....................................................................................................................................... 156
Concept of Word Processor ..................................................................................................................... 156
Spread Sheet ............................................................................................................................................... 191
Data Filter and Sorting ............................................................................................................................. 228
Data Analysis and Pivot Tables............................................................................................................... 231
What If Analysis ........................................................................................................................................ 235
Presentation................................................................................................................................................ 243
Database Management System (DBMS) ................................................................................................ 271
Domain Specific Tools .............................................................................................................................. 272
SUMMARY .............................................................................................. 273
EXERCISE ................................................................................................ 273
ACTIVITIES ............................................................................................ 274
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Introduction...................................................................................................................................................... 276
Programming languages ................................................................................................................................ 276
Compiler, interpreter and assembler............................................................................................................ 280
Introduction................................................................................................................................................ 280
Concept of programming statements........................................................................................................... 283
Syntax and semantic errors............................................................................................................................ 284
Program control structures ............................................................................................................................ 286
Sequential Structure .................................................................................................................................. 287
Selection or Branching Structure............................................................................................................. 288
Iteration or Looping Structure................................................................................................................. 289
Program Design Tools .................................................................................................................................... 290
Algorithm ................................................................................................................................................... 291
Flow Chart .................................................................................................................................................. 292
Pseudo code or Structured English......................................................................................................... 297
Codes................................................................................................................................................................. 298
Binary Coded Decimal (BCD) Code ....................................................................................................... 299
Gray Code (Absolute Binary Code)........................................................................................................ 299
Alphanumeric Code.................................................................................................................................. 299
Unicode ....................................................................................................................................................... 301
Programming in C........................................................................................................................................... 301
Introduction................................................................................................................................................ 301
Brief History ............................................................................................................................................... 303
Characteristics (Features) ......................................................................................................................... 303
Advantages and Disadvantages of C-language.................................................................................... 304
Basic Structure of C Programs................................................................................................................. 305
The Compiling Process ............................................................................................................................. 306
C Preprocessor and Header Files ............................................................................................................ 306
Character Set used in C ............................................................................................................................ 309
Use of Comments ...................................................................................................................................... 310
Identifiers and Keywords and Token..................................................................................................... 310
Data Types in C ......................................................................................................................................... 311
Constants and Variables........................................................................................................................... 315
Type of Specifier ........................................................................................................................................ 317
Statements................................................................................................................................................... 318
Operators and Expressions ...................................................................................................................... 319
Type Casting and Conversions ............................................................................................................... 324
Introduction to Library Functions .......................................................................................................... 326
Control Structure (Statement).................................................................................................................. 337
Array and String ........................................................................................................................................ 357
SUMMARY .............................................................................................. 381
EXERCISE ................................................................................................ 383
ACTIVITIES ............................................................................................ 386
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Introduction to Web Development............................................................................................................... 388
Client-side Languages (Programming or Scripting) ............................................................................ 388
Web Browsers And Search Engines.............................................................................................................. 391
Web Browsers ............................................................................................................................................ 391
Search Engines ........................................................................................................................................... 392
Overview of Various Internet and Web Technologies............................................................................... 394
Introduction of Internet ............................................................................................................................ 394
Content Management System (CMS) ........................................................................................................... 400
HTML: Web Page Designing Language ...................................................................................................... 402
Introduction to html........................................................................................................................................ 402
Advantages of HTML ............................................................................................................................... 404
Disadvantages of HTML .......................................................................................................................... 404
Structure of HTML .......................................................................................................................................... 404
Published and Hosting ................................................................................................................................... 406
Web Publishing.......................................................................................................................................... 406
Web Hosting............................................................................................................................................... 406
Types of Tags ................................................................................................................................................... 407
Character Formatting...................................................................................................................................... 411
Formatting Heading.................................................................................................................................. 411
Paragraphs Formatting Tags ................................................................................................................... 412
Text Formatting Tags ................................................................................................................................ 413
Listing Tag .................................................................................................................................................. 420
Inserting Images and Objects......................................................................................................................... 422
The Attributes of Image Tag .................................................................................................................... 422
Hyperlinks........................................................................................................................................................ 423
Anchor Tag ................................................................................................................................................. 423
Tables ................................................................................................................................................................ 424
Designing Frames and Forms........................................................................................................................ 431
Introduction to HTML5 .................................................................................................................................. 443
HTML5 Elements....................................................................................................................................... 444
HTML5 Graphics ....................................................................................................................................... 453
Domain Name System (dns).......................................................................................................................... 471
Concept of Cascaded Style Sheet (css) and Script Language.................................................................... 471
Introduction................................................................................................................................................ 471
Inline Style Sheet ....................................................................................................................................... 473
Internal Style Sheet.................................................................................................................................... 473
External Style Sheet................................................................................................................................... 474
Webpage Design and Editing Tools ............................................................................................................. 475
SUMMARY .............................................................................................. 476
EXERCISE ................................................................................................ 476
ACTIVITIES ............................................................................................ 478
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Introduction to Multimedia ........................................................................................................................... 480
Components of Multimedia........................................................................................................................... 480
Multimedia Software Requirements....................................................................................................... 481
Content Components of Multimedia...................................................................................................... 482
Types of Multimedia................................................................................................................................. 483
Major Characteristics of Multimedia...................................................................................................... 483
Advantages of Multimedia ...................................................................................................................... 484
Disadvantages of Multimedia ................................................................................................................. 484
Importance and Use of Multimedia in Some of the Major Fields ............................................................ 484
SUMMARY .............................................................................................. 486
EXERCISE ................................................................................................ 487
ACTIVITIES ............................................................................................ 488
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Digital Society and Computer Ethics ........................................................................................................... 490
Digital Society ............................................................................................................................................ 490
Computer Ethics ........................................................................................................................................ 490
Digital Divide................................................................................................................................................... 491
The Three Aspects of The Digital Divide............................................................................................... 492
Information Security (INFOSEC) .................................................................................................................. 492
CIA Triad .................................................................................................................................................... 493
Confidentiality ........................................................................................................................................... 493
Integrity....................................................................................................................................................... 493
Availability ................................................................................................................................................. 493
Identity and Access Management........................................................................................................... 493
Identification .............................................................................................................................................. 493
Authentication ........................................................................................................................................... 493
Authorization............................................................................................................................................. 494
Accountability............................................................................................................................................ 494
Risk Management Concepts .................................................................................................................... 494
Vulnerability .............................................................................................................................................. 494
Risk .............................................................................................................................................................. 494
Computer (cyber) Crime ................................................................................................................................ 494
Malicious Software and Spam ....................................................................................................................... 496
Spam ............................................................................................................................................................ 496
Malicious Software.................................................................................................................................... 496
Types of Malicious Software.................................................................................................................... 497
Privacy and Anonymity ................................................................................................................................. 498
Intellectual Property Right (ipr) .................................................................................................................... 499
Digital Signature.............................................................................................................................................. 500
Advantages of digital signature .............................................................................................................. 501
Cyber Law ........................................................................................................................................................ 502
Information Communication Technology (ict) Policy in Nepal............................................................... 503
SUMMARY .............................................................................................. 507
EXERCISE ................................................................................................ 509
!BIBLOGRAPHY ................................................................................................................................ 510
Computer System
LEARNING OBJECTIVES
After studying this chapter, the students will be able to understand to:
Basic understand of study material and scope is most important. With this unit basic concept
........ of computer in terms of evolution, application, features, generation, hardware components and ..........
..
their architecture, organization, their interfaces and computer classification provides after
studying. We will have cleared fundamental knowledge over the computer at the end of unit.
.2 … Computer Science–I
INTRODUCTION
The term 'computer' originates from the word 'computare', which means 'to calculate'. We, human beings,
are always involved in some kind of calculations-simple or complex. Mathematical calculations like
addition, subtraction, multiplication, division etc can be solved easily with simple tools, mouth and finger
or sometimes we may need formulas, pen and paper or calculating machines. Such calculations can be
simple, consuming less time to calculate while some calculations can be complex and so difficult that the
simple tools, formulas or methods may not work. Even the calculation may take long time, and the result
can be wrong or inaccurate. Therefore, man was always in search of a machine which could perform all
kinds of calculations faster and accurately. This gave birth of a machine which is commonly known as
'computer'.
The computer we see today is quite different from the one made in the beginning. The number of
applications of a computer, the speed and accuracy of calculation has increased. We must appreciate the
impact of computers in our day to day life. Reservation of tickets in Air Lines and Railways, payment of
telephone and electricity bills, deposits and withdrawals of money from banks, business data processing,
medical diagnosis, weather forecasting, etc. are some of the areas where computer has become extremely
useful.
The computer we see today is quite different from the one made in the beginning. The number of
applications of a computer, the speed and accuracy of calculation has increased. We must appreciate the
impact of computers in our day to day life. Reservation of tickets in Air Lines and Railways, payment of
telephone and electricity bills, deposits and withdrawals of money from banks, business data processing,
medical diagnosis, weather forecasting, etc. are some of the areas where computer has become extremely
useful.
However, there is one limitation of the computer. Human beings do calculations on their own. But
computer is a dumb machine and it has to be given proper instructions to carry out its calculation. This is
why we should know how a computer works.
Some countries are called developed, some developing and others underdeveloped. In the past, many
countries which were able to catch up the opportunities brought about by industrial revolution became
industrialized. Now we are in the process of another industrial revolution. This second industrial
revolution is the result of invention of computer technology. It is one of the greatest inventions of human
mind. Computer technology has been playing important role in every sector of our daily life. Computer
has strengthened our capacity in numerical computations, information processing, storage, modeling and
simulation, concepts of globalization, increasing working capability and efficiency, converting online
approach, decreasing physical present etc.
A computer, independent of it's size, is an electronic device used for processing of data (numbers,
alphabets, any other symbols). It basically performs the following three functions in sequence;
● Receive raw data and instructions from input devices
● Process data according to the instruction, and
● Produce useful output and stored information for future used.
Figure: 1.1 Processing
Raw Data as Input Information as Output
Class, Processing Mina Sharma is a
Sharma Class 11 student of
Mina Valley school
School,
Valley, 11
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Computer is, in fact, a dumb machine in the absence of human intervention. That means, computer can't
do anything in its own, user must provide appropriate instruction to the computer in order to generate
useful result. But, once we provide instructions and data, computer can continue working continuously
with very high speed without any tiredness. If we provide wrong instruction and data, computer will
produce incorrect result. This is called Garbage in Garbage Out (GIGO).
Computer has become an indispensable machine to increase the effectiveness and efficiency of every
person, organization, country, students, teachers, scientist, researchers, and of every field including
education, business and industry, science, technology, astrology, mining, astronomy, and many more. The
computer can be better understood if we know the technology used in computer, and characteristics and
application of computers. Therefore, in this chapter we will discuss about characteristics and applications,
and evolution in terms of generations of computers, the measurement unit of speed of computer,
classification of computer in terms of size and speed (Micro, Mini, Mainframe and Super), mobile
computing and its applications, computer architecture and organization, components of computer system
(Input unit, Processing unit, Output unit, Memory unit), microprocessor and bus system, and hardware
interface.
CHARACTERISTICS OF COMPUTER
Now-a-days computer is playing an important role in every sector of daily life; it has become a basic need
of most of the people just like television, telephone or other electronic devices at home, and gaining
popularity among others as well. It can solve numerical, logical or other decision related human problems
very quickly as well as accurately. The important characteristics of a computer are described below:
1. Speed: The computer is a very high speed electronic device. The operations on the data inside the
computer are performed through electronic circuits according to the given instructions. The data and
instructions flow along these circuits with high speed that is close to the speed of light. Computer can
perform million of billion of operations on the data within a second. The computer generates signals
during the operation process therefore the speed of computer is usually measure in mega hertz
(MHz) or giga hertz (GHz). It means million cycles units of frequency is hertz per second. Different
computers have different speed.
2. Accuracy: In addition to being very fast, computer is a very accurate device. It gives accurate output
result provided that the correct input data and set of instructions are given to the computer. It means
that output is totally depended on the given instructions and input data. If input data is in-correct
then the resulting output will be in-correct. In computer terminology it is known as garbage-in
garbage-out.
3. Reliability: The electronic components in modern computer have very low failure rate. The modern
computer can perform very complicated calculations without creating any problem and produces
consistent (reliable) results. In general, computers are very reliable. Many personal computers have
never needed a service call. Communications are also very reliable and generally available whenever
needed.
4. Storage: A computer has internal storage (memory) as well as external or secondary storage. In
secondary storage, a large amount of data and programs (set of instructions) can be stored for future
use. The stored data and programs are available any time for processing. Similarly information
downloaded from the internet can be saved on the storage media.
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5. Retrieving data and programs: The data and program stored on the storage media can be retrieved
very quickly for further processing or use. It is also very important feature of a computer.
6. Automation: A computer can automatically perform operations without interfering to or the
intervention of the user during the operations. It controls automatically different devices attached
with the computer. It executes automatically the program instructions one by one.
7. Versatility: Versatile means flexible. Modern computer can perform different kind of tasks one by
one or simultaneously. It is the most important feature of computer. At one moment you are playing
game on computer, the next moment you are composing and sending emails etc. In colleges and
universities computers are use to deliver lectures to the students. The talent of computer is
dependent on the software. Computer can be used in every field like science and technology,
automation, education, medicine, e-governance etc.
8. Communications: Today computer is mostly used to exchange messages or data through computer
networks all over the world. For example the information can be received or send through the
internet with the help of computer. Similarly, telecommunication networks are controlled and
switched by computers. It is most important feature of the modern information technology.
9. Diligence: A computer can continually work for many hours without creating any error. It does not
get tired while working for many hours. It performs the operations with the same accuracy,
reliability as well as speed as the first one.
10. No Feelings: Computer is an electronic machine. It has no feelings. It detects objects on the basis of
instructions given to it. Based on our feelings, taste, knowledge and experience, we can make certain
decisions and judgments in our daily life. On the other hand, computers can not make such
judgments on their own. Their judgments are totally based on instructions given to them.
11. Consistency: People often have difficulty to repeat their instructions or work again and again. For
example, a lecturer feels difficulty to repeat a same lecture in a class room again and again. Computer
can repeat actions consistently (again and again) without losing its concentration:
● To run a spell checker (built into a word processor) for checking spellings in a document.
● To play multimedia animations for training purposes.
● To deliver a lecture through computer in a class room etc.
● A computer will carry out the activity with the same way every time. You can listen a lecture or
perform any action again and again.
12. Precision: Computers are not only fast and consistent but they also perform operations very
accurately and precisely. For example, in manual calculations and rounding fractional values (That is
value with decimal point can change the actual result). In computer however, you can keep the
accuracy and precision up to the desired level. The lengths of calculations or decimal places always
remain accurate.
APPLICATION OF COMPUTERS
Computer is playing very important role in every field of life. Computers are applied or used everywhere
such as at home, at school, at working place, at entertainment etc. In daily life a large number of activities
are dependent on computers and their technology. In most of the fields where computer is playing very
important role for different purpose. Some of them are:
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Education
Education is the process of developing knowledge through instructions. The instructions are received
from people such as parents, teachers etc. and from printed
material such as books, journals etc. Today, the modern
technique to get knowledge is by using computers. All
schools use computers in classrooms and labs to teach
students. Many educators prefer to deliver their lectures by
computer-based presentations or multimedia programs. In
schools, colleges and universities, students use software
packages to complete their assignments.
The computer assisted learning (CAL), computer-based
training (CBT) or presentation is also called computer aided
instruction (CAI). In this method, computer is used as an aid
to teach the students in the classroom. The instructions of particular subject are received from the
instructions that use a program presented by a computer as learning medium. The web-based training
(WBT) is another type of CBT that uses internet technology. It means that many websites provides online
education. A lot of materials on different topics are available on these websites. They also provide online
lectures and tutorials for the students. The CBT and WBT are used in business education centers to
educate people. People can get knowledge at very low cost as well as in very short period of time. Most of
the WBT is free of cost.
Entertainment
Computer has also played a very important role in
entertainment for different levels of people. Computer has
become need of humans for entertainment at their home, like
playing video games,. Similarly, software is available to see
movies and to listen music. Today the movie files and
famous songs are mostly available on CDs or on the web at
very low cost. We can listen music while work on the
computer. On the web, we can view fine art images in online
museums and galleries. Some artists sell their works online
and others display them for our viewing pleasure.
E-Commerce
E-commerce (electronic commerce) or e-trade or e-business is a financial business transaction conducted
electronically between business partners over computer
network (such as on Internet). With e-commerce,
transactions can occur instantaneously and globally. This
saves time for participants on both ends. The users can
buy, sell and exchange products or services via computer
network. Today, many mobile computers can also access
the internet on wireless.
There are many applications of e-commerce such as home
banking, buying stocks, collaborating electronically with
business partners around the globe, marketing and
advertising products, providing services to the customers
etc. There are several types of e-commerce like
collaborative commerce business-to-business, consumer-
to-consumer, mobile commerce etc.
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The following services are mostly used in e-commerce or e-business.
i. E-mail: It is the most popular service through which we can electronically send and receive messages
anywhere in the world. The spoken messages are sent and received through voice mail.
ii. Video Conferencing: Video conference is a meeting between two or more people residing at various
places. They can watch and talk with each other. They use a network to participate in a video
conference with the help of a video camera, a microphone, speaker and software (special video
conferencing software). Video conferencing also need a computer with a large memory and fast
processor. Video conferencing provides a complete simulation of a normal meeting environment,
enabling both parties to see, hear and present material, just as if they are in the same room.
iii. Electronic Shopping (E-Shopping): Many businesses now have websites that allow internet users to
buy goods or services electronically. Shopping can take place using a computer at home, or at a
cybercafé. The e-shop can be anywhere in the world and it remains open 24 hours a day. You can
purchase any good such as books, software, movies, computers, cars, airline tickets etc. on the web.
iv. Electronic Banking: One of the most popular uses of e-commerce is electronic banking. An electronic
banking is also known as cyber-banking. It includes various banking activities conducted from home,
a business, or on the road instead of a physical bank location. In all over the world, about 95 percent
banks are online.
Health Care
Nearly every area of the medical field uses computers, such as laboratories, researches, scanning,
monitoring, pharmacy, telemedicine etc., which are helping
the doctors to diagnose diseases and many other purposes.
The main uses of computer in medical field are described
below:
i. Maintaining Patient History and Other Records: The
complete bio-data as well as medical history of patient
is recorded into the computer before check up of
patient. The complete medical history (current and
previous) is delivered to the related doctor for the check
up of patient. In this way, much of the doctor's time is saved.
In addition to patient history, other information about doctors, medicines, chemicals and equipments
is also maintained. It is very easy and efficient way to organize records than paper-based records.
Any information about patients, doctors, equipments etc. can be retrieved very easily and quickly. In
hospitals, mostly all the medical wards are interconnected through network. So, if a patient is
allocated a specific ward but being examined by a consultant and receiving treatment in other areas
(wards) of the hospital, his detail can be viewed and updated at any terminal on the hospital's
LAN/WAN network.
ii. Patient Monitoring: The electronic scanning units (medical equipments) used in hospital can also be
attached to computers. These are very expensive and are used to monitor the patient continuously.
Thus computers are normally used in the following medical units of hospitals.
● ICU (Intensive Care Unit)
● Operation Theater
● Recovery Room
● Medical Ward
● ECG (Electrocardiograph)
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The medical equipment with sensors attached to the patient that detects changes of heart rate, pulse
rate, blood pressure, breathing and brain activity. If any unbalancing situation occurs, computer
activates the alarming device, which creates sound and alerts the medical staff. The data is also
logged and used to analyze the change in a patient's condition over a period of time.
iii. Diagnosis of Diseases: Computer is also used in hospital for diagnosis. For example, laboratory tests
on blood and tissue chemistry have become dependent on computer analysis.
One common use of computer in hospital is to scan the body of patient. A special scanner is used for
this purpose. A scanner sends electromagnetic rays through a patient body and sensors detect that
how much patient's body have affected to any type of cancer or disease. For example, the CAT
(Computerized Axial Topography) scanner passes rays over the patient. A CAT scanner takes many
X-rays around the body. It displays an image that enables physicians to look beneath the patient's
skin. As the scanner passes over the patient, it displays and image of bone and tissue structure of
patient on a computer screen.
iv. Telemedicine: Another improvement in the medical field is the telemedicine. In telemedicine, we can
access medical care centers and doctors located at distant places using computers videoconferencing.
v. Computer-Aided Surgery (CAS): Many surgeons also use computer aided surgery while they are in
training. It is used to learn surgical techniques. The physicians and dentists also use the computer
aided learning (CAL) program.
Many websites also provide up-to-date medical, and fitness related information. These websites also
maintain databases about various problems and their solutions. There are also medical chat rooms on
the internet.
Science and Engineering
Computer is used in all branches of science and engineering
to collect and analyze data. The scientists also use internet to
collect the latest information around the world. Today, it is
impossible to carry out scientific researches without use of
computers. In all branches of science, it is mainly used to get
accurate experimental results, for example to get accurate
forecasting of weather etc.
Publishing
In the field of publishing, computer is playing very important
role to publish the books, magazines and newspapers etc.
The publishers use computer and word processors and
graphics software to design pages of the books or magazines.
Many writers and publishers use Internet to collect
information that is used for compiling a new book of
magazine. Some websites allow you to download and entire
book, called an electronic book (e-book). The journalists also
use the notebook computers and digital cameras to capture
and record news.
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Traveling
Computer is also playing very important role in traveling by
car or airplane and to arrive easily and safely at your
destination. Today many vehicles manufactured use special
electronic equipments in the car that controls various
activities of the car. These cars have GPS (Global Positioning
System) receiver that reports your vehicle's location. These
cars also have "Onboard Navigation Systems" that have the
following features.
● Track the vehicle if it is stolen
● Provide emergency services
● Provide directions
● Provide roadside assistance
● Perform remote diagnostics if a warning light appears on the dashboard
● To make hotel and restaurant reservations
Today many vehicles also include options such as screens with e-mail and internet access, printers, fax
capability etc. Airlines also provide online access. The passengers can connect their notebook or hand held
computer to the web during their flights. Some airlines also provide web surfing devices to their passenger
during their flights. Computer is also used in cars to monitor fluid levels, temperatures, electrical systems
etc. It is also used to monitor the air traffic etc.
Government and E-Governance
A government runs the country by making policies, and
provides services and information to the citizens. Most of the
government departments have their own websites.
Governments use computers and networks to implement e-
governance. The computers are used in all government
offices to perform various activities, and for automation. The
government agencies use computers and networks to
implement e-governance as part of their daily routine.
Home
Like other electronic devices used in home such as T.V. set,
washing machine etc. computer has also become the need of
every person at home. It is used at home as an educational
tool for children. But it is also used at home to keep records,
write letters, prepare budgets, connect with others to send
and get information on the internet, to watch films and to
listen music or other entertainment etc.
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Agriculture
In agriculture field also, computer is playing very important
role. The agricultural scientists are using computer for
analyzing the agricultural data. The students of agriculture
also uses computer to get latest information about
agriculture on the internet. The farmers also use computer to
get information about crops and to calculate bills and cost
per acre, advertise their products and to get information
about crops market prices.
Energy
Energy companies use computers to locate or search oil, coal, natural
gas and uranium. Similarly electric power companies use computers
to monitor the power networks. In addition, meter readers use hand
held computers to record the units consumed in homes and business.
Industry
In industry, computers are used to control the manufacturing
system and continuous running of the machinery. These also
help in monitoring temperature, pressure, check the quality
and accuracy and measurement needed in the manufacturing
process.
In industry, robots are used to perform most of the activities
as mentioned above. A robot is an automatic programmable
machine that moves and performs mechanical tasks. It means
that a robot acts like human beings. Robot can work in
environment that is dangerous for human being such as
opening chemical packages and packages believed to contain bombs. It can perform repetitive tasks
continuously without any break, at very high accuracy than human. Robots can also be used in hundreds
of applications such as:
● Assembling & spray-painting cars
● Lifting of heavy equipments, power cables etc.
● Testing blood samples
● Performing experiments in artificial satellites and radioactive environment etc.
EVOLUTION OF COMPUTER
The development of computer was not spontaneous. Many scientists and many activities contributed to
the evolution of computers. Computer is a complex machine having many components interrelated with
each other. Each of these components was invented separately, and by different inventors. Peoples are
considered as the first computer, because the word computer was used to describe people who were
involved in repetitive computations. It is a natural phenomenon that any human being involved in same
type of computation for a long time may get bored, resulting in carelessness and finally committing
mistakes. Even the manual calculation can be slow and prone to errors. Therefore, scientists have been
involved for hundreds of years in inventing new technology to mechanize the computation.
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The earliest counting devices known to man were his own hands and fingers. If that wasn't enough, things
in nature were used like shells, stones (pebbles), sticks. Therefore, man was always in search of new
methods and technology. As a result, the first real computer, which was electro mechanical in nature, was
invented during 1940s, but the history of computer dates back to around 500 B.C. Electronic and
microelectronic is the dominant technology of present day computers. Therefore, in terms of technological
innovation, method of operation, and the historical perspective of phases of computer development, the
historical time period can be divided into different eras;
1. First Era: Pre-history era or Pre-mechanical era (500BC-1642)
2. Second Era: Mechanical era (1642-1890)
3. Third Era: Electro-mechanical era (1890-1945)
4. Fourth Era: Electronic era (1946-today)
The computer technology has a long development history. Since the pre-history period, many different
devices were invented and used, but no major conceptual changes were made until the end of 18th
century. During 19th century, major break through occurred and, the real computer was invented during
1940s and studies in terms of generations of computers.
Pre- History Era or Pre- Mechanical Era (500BC-1642)
This was the period between 500 BC to 1642 A. D. During the earlier days of pre-history, simple tools were
used for calculations. Counting was done using stones or sticks to count and keep records. Man was in
search of easier and faster tools to quantify, and to do mathematical calculations. Hence, around 500 BC, a
simple counting tool called Abacus was invented in China. It would perform all the arithmetic operations
like addition, subtraction, division and multiplication. It aided the memory of the human performing the
calculation. The abacus is considered as the first personal calculator. Abacus was the most significant and
earliest computing tool that marked the existence of modern computers. Therefore, it is considered that the
computer has its beginning back in pre-history, starting with the abacus. The major disadvantage was
losing truck while calculating resulting into wrong figures. Some other significant contributions during
this era are;
• A century after the invention of Abacus, the Arabs invented the decimal numbering system — the
basic language of mathematics.
• Introduction of Arabic numerals to Europe in the 8 and 9 centuries A.D. The Arabic system
introduced the concepts of the 0 and fixed places for tens, hundreds, thousand, etc., and greatly
simplified mathematical calculations.
• The model of the abacus integrated the knowledge of the decimal number system and
evolved into a mechanical calculator.
• Invention of logs in 1614 by John Napier. Logs allow multiplication and division to be
reduced to addition and subtraction, where the logarithm values were carved on ivory sticks which
are now called Na pier's Bones.
The details of different devices invented during this era are given below.
Abacus
The Abacus is the earliest and the simplest calculating device. The
Abacus is also known as "Soroban". It was developed and used in
China about 500 B.C. The Abacus was a very simple computing
device used for simple addition and subtraction. It consists of a
rectangular wooden frame having parallel wires (strings). Each wire
supports a number of beads.
The beads across the wires are free to move along the length of the
wires. Each bead down represents a digit. The position of wires and
their values are:
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• The beads in the first wire on right represent unit digit.
• The beads in the second wire on right represent the tens digit.
• The beads in the third wire on right represent the hundreds digit and so on.
Calculating Device of John Napier (1550-1617)
In the early 17th century, the famous logarithms idea was developed by John Napier, a Scottish
mathematician. He created logarithm tables for arithmetic
calculations. He also developed a new manual calculating device
using rods, also known as Napier's Bone to perform arithmetic
calculations. The Napier's Bone was also referred to as Cardboard
Multiplication Calculator. The Napier's calculating device remained
in use till 1890.
The commonly used calculating device known as "Slide Rule" was
also developed using the concept of Napier's idea of logarithms.
Slide Rule was first built in England in 1632. With the modem Slide
Rule, we can perform simple arithmetic calculations as well as calculate square roots, logs, sine, cosine and
tangent etc. The Slide Rule was used till the middle 1970s.
Figure: 1.2 Slide rule
Mechanical Era (1642-1890)
Notable other personalities who contributed to the current technology included: Napier John, Blaise
Pascal, Gottfried Wilheim Von Leibniz, and Jacquard Joseph Marie. This was the period between 1642 and
1890 which is considered as mechanical era in the history of computer. This period is called mechanical
because the machines were based on moving parts, operated by machines and they didn't have any logical
control in operation.
Mechanical era starts with the work of Wilhelm Schickard. He built the first mechanical calculator in 1642,
which was actually the calculating clock. It was able to work with six digits, and carried digits across
columns. The details of other different notable devices invented during this era are given below.
Calculating Device of Blaise Pascal (1642 - 1662)
In 1642, reputed mathematician Blaise Pascal of France, at the age of 19, invented the mechanical
calculating machine called Pascaline as an aid for his father
who was a tax collector It used arithmetic calculations like
addition, subtraction, multiplication and division and
displayed the numbers by rotation of different wheels or
gears. Each wheel rotated in steps and a wheel completed one
rotation in 10 steps. The Pascal's calculating machine could
perform the addition & subtraction operations directly but
the multiplication & division operations were performed by repeated additions and subtractions.
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Blaise Pascal's calculating machine was the first mechanical calculator. It had the capacity for eight digits
and used a series of wheels or gears each numbered from 0 to 9 (base ten), but had trouble carrying and its
gears tend to jam. Although this machine could perform addition and subtraction on whole numbers, it
was too expensive and only Pascal himself could repair it
Calculating Device of Gottfried Von Leibniz (1646 - 1716)
In 1671, a German mathematician Gottfried Von Leibniz
developed first calculator for multiplication as well as for
other simple arithmetic calculations. This calculating
machine was similar to Pascal's calculating machine but it
was more reliable and accurate. Actually the Leibniz
calculating machine was the modified form of the Pascal's
calculating machine.
Punched Board System of Joseph Marie Jacquard (1752 - 1834)
Joseph Marie Jacquard, an engineer of France, invented the machine called a Jacquard loom (1801) used in
weaving. It was a "Programmable" manufacturing device. It was the first machine that used punched cards
which stored information; for example- it had different weaving patterns such that the same patterns
would be utilized over and over again to get the same product. The ability of his machine to store
information contributed a lot to the computer evolution and the textile industry. This automated loom
machine (also called power loom) operated by dropping needles through holes punched in cards. When
the needle passed through the hole it lifted a weaving thread, if the needle did not drop through the hole
the weaving thread lowered. When the weaving shuttle passed through the threads it developed a pattern.
Since the needles were up or down like on or off switches used in computers today, the automated loom is
considered the “true digital computer”. The punched card system later applied to the U.S. census and then
to computers.
Calculating Device of Charles Xavier (1785 - 1870)
In 1820, a scientist of France, Charles Xavier invented a
calculating machine that could perform simple arithmetic
calculations such as addition, subtraction, multiplication
and division. This calculating machine was named as
Arithmometer.
Calculating Machines of Charles Babbage (1791 - 1871)
By 1822, the English mathematician Charles Babbage, at Cambridge University, U. K., proposed a steam
driven calculating machine having the size of a room, which he called the Difference Engine. This
machine was able to compute tables of numbers, such as logarithm tables. Ten years later the device was
still nowhere near complete, acrimony abounded between all involved, and funding dried up. The device
was never finished.
Babbage was not deterred, and by then he was on to his next brainstorm, which he called the Analytic
Engine. This device was large as a house and powered by six steam engines. Babbage who made an
important intellectual leap regarding the punched card, the presence or absence of each hole in the card
physically allowed a colored thread to pass or stop that thread card. In the Jacquard loom, Babbage also
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saw that the pattern of holes could be used to represent an abstract idea such as a problem statement or
the raw data required for that problem's solution. The Analytic Engine also had a key function
(conditional statement) that distinguished computers from calculators. Furthermore, Babbage realized that
punched paper could be employed as a storage mechanism, holding computed numbers for future
reference.
Figure: 1.3 Difference Engine Figure: 1.4 Analytical Engine
Analytical engine had several features including provisions for inputting data, storing information,
performing arithmetic calculations and printing out results which are also found in modern electronic
computers. Analytical engine provided the foundation for the modern computer. Therefore, Charles
Babbage is known as the father of modern computer.
Lady Augusta Ada (1816 - 1852)
A lady student Augusta Ada Byron, though she was only 19, heard a lecture about the difference engine
designed by Charles Babbage and was fascinated by Babbage's ideas. Therefore, through letters and
meetings with Babbage she learned enough about the design of the Analytic Engine to begin fashioning
programs for the still un-built machine. Ada wrote a series of "Notes" wherein she detailed sequences of
instructions she had prepared for the Analytic Engine. Babbage got impressed with the work of Ada, and
Babbage himself wrote, "…some complicated programs of her own, the most complex of these being one
to calculate the sequence of Bernoulli numbers." Therefore, Ada earned her spot in history as the first
computer programmer. The programming language Ada is named after her. Ada also invented the
subroutine and was the first to recognize the importance of looping .
Electro-mechanical era (1890 – 1945)
The end of the Mechanical Era occurred when physics paved the way for electrical innovation. Scientists
discovered electrical charge as a way to represent data. The beads of the abacus were replaced by bits in
the modern computer. Essentially a bit or ‘binary digit’ is a small electrical charge that represents a 1 or 0.
The creation of the bit marked a transition from the decimal system for humans to a binary system for
computers.
For the first time, electricity was used in the operation of computers, but computers still had many
mechanical components. Programming a computer did not involve software. Rather, the programmer
actually rewired the paths of electricity through the machine in order to change its mode of operation.
Since, both the electrical and mechanical components were used, this era is known as electro-mechanical
era. The details of different devices invented during this era are given below.
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Punched Cards by Herman Hollerith (1860 - 1929)
In 1890, an American scientist Herman Hollerith used the idea of punched board system and introduced
the punched cards as input media in computer. He developed the first electro-mechanical punched card
tabulator. This machine could read information that had been punched into cards. These cards were
maintained in stack form. Solutions to different problems could be stored on different stacks of cards and
accessed when needed.
Invention of punched cards opened a gate to modern data processing. IBM and other computer
manufacturers came in this field and started production of computers that could use punched cards as
input media. These computers could perform arithmetic calculations and sort numbers. Data were fed
through punched cards. As compared to today's computers, these computers were slow in data
processing. Usually, these computers could process 50 - 220 cards per minute and each card holding about
80 decimal numbers (or characters). The punched cards provided a means of input/output (I/O), and
memory storage.
Figure: 1.5 Hollerith Early Punched Figure: 1.6 Card Hollerith Census Machine
Atanasoff Berry Computer (ABC)
In 1939, Dr. John Atanasoff, a professor of Iowa State
University and his assistant, Clifford Berry designed an
electronic machine to solve mathematical problems. It was
called the Atanasoff Berry Computer, or ABC (Atanasoff and
Berry Computer). The Boolean algebra was applied for
designing the circuits of this computer. The development of
working model of ABC was completed in 1942. In this
computer, 45 vacuum tubes were used for performing
internal logic operations and capacitors were used for
internal data storage.
Boolean Algebra
Boolean algebra is the algebra of logic, it was introduced by English mathematician George Boole in 1847
for designing logic circuits inside the computer.
The Boolean algebra's rules or principles are used to design the circuits inside the chips. The design of a
particular circuit is based on a set of logical statements. These statements return either true (or 1) or false
(or 0). Boolean algebra uses two binary numbers 0 and 1.
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Mark-1 or ASCC
In 1944, an American Dr. Howard Aiken, a professor of Harvard University, designed first fully automatic
calculating machine. It was named as Mark-1. It is also
known as ASCC (Automatic Sequence Controlled
Calculator). This calculating machine operated under the
control of given instructions. The instructions were given
to this machine with the help of punched paper tape. The
Mark-1 remained in operation till 1959.
Although Mark-1 proved to be extremely reliable, but it
was very complex in design and huge in size. It was
approximately 50 feet long and 8 feet high. It was basically, an electro-mechanical device in which both
electronic and mechanical components were used.
Electronic era (1946-present)
Electronic era begins with the invention of the first real computers as a result of convergence of
technology, people, and motivation. The development of electronic era is often described to in reference to
the different generations of computing devices. Each generation of computer is characterized by a major
technological development that fundamentally changed the way computers operate, resulting in
increasingly smaller, cheaper, more powerful, and more efficient and reliable devices. This era is fully
driven by electronic devices as components of computer.
• 1946: ENIAC at University of Pennsylvania, by John Mauchly and J. Presper Eckert
• The "Baby" at Manchester University, England by Sir Freddy Williams - the first store program
computer
• 1948: EDSAC at Cambridge University, England by Sir Maurice Wilkes - the first true modern
computer
• 1949: EDVAC at University of Pennsylvania by Herman Goldstine and others, and designed by John
von Nuemann
• The first commercial machine in the US was the UNIVAC I, bought by the Census Bureau in 1951.
The first in the world was the LEO, built by Lyons Catering Corp., in London, England, 1950.
After 1950s the developments in computer organization are often organized into several "generations,"
distinguished by evolution in different aspects of electronics;
• Digital technology: Vacuum tubes; transistors; integrated circuits.
• Programming languages: machine and assembly language; high-level languages; very high-level and
problem-oriented languages; object-oriented languages, natural languages.
• User interface and I-O devices: switches and wires; paper and magnetic tape; keypunches and card-
readers; monitors and keyboards; batch computing and job control languages; interactive systems
and command-line interfaces; fixed and removable disks, optical disks; the mouse, point-and-click,
menus, windows; audio and video; virtual reality devices.
• Dominant applications: numerical simulation; data processing and database information retrieval
and exchange; entertainment; communication.
Many people describe the electronics era as the period between 1945 and 1958, when the vacuum tube was
the dominant electronic technology used in computers. After the development of transistors in 1958, and
integrated circuits during 1960s, the electronic components become miniaturized in size and seen
remarkable steady improvements in cost, speed and availability of computers. Therefore, the period after
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1958 is described as Microelectronic era [1958 - today], in which transistors, integrated circuits, and
microprocessors are dominant electronics components. In this era, networking and communication,
parallel and distributed computing, embedded systems, and many more technological integration and
innovations are possible.
The computers in electronic era are divided into different generations;
• Zero Generation -1920's: Electro-mechanical
• First Generation - 1940-1956: Vacuum Tubes
• Second Generation - 1956-1965: Transistors
• Third Generation - 1965-1973: Integrated Circuits
• Fourth Generation - 1973- 1991(Present): Microprocessors
• Fifth Generation - Present and Beyond: Artificial intelligence
The generations of computer will be discussed immediately after this section. Some of the machines
developed during this era are described here under.
ENIAC (1943 - 1946)
ENIAC stands for "Electronic Numerical Integrator And
Calculator". It was the first all electronic computer. It was
developed in 1943 by J.P. Eckert and John Mauchly at the Moore
School of Engineering, university of Pennsylvania in USA. It
contained about 18,000 vacuum tubes and occupied more than
1,500 square feet with weight of 30 tons.
The ENIAC was programmed by physically connecting electrical
wires in the proper order. It was very difficult to detect errors
and to change the program. Similarly, it could store and
manipulate limited amount of data. So, its use was limited.
EDVAC (1946 - 1952)
ENIAC was programmed by physically connecting electrical wires in the proper order. The operation of
ENIAC was very difficult due to its wiring boards. This problem
was overcome by a new concept of stored program presented by
John Von Neumann. John Von Neumann gave an idea that a
computer should have a very simple, fixed physical structure,
and yet be able to perform any kind of computation without the
need for any physical change in the unit. Von Neumann idea
usually referred to as the stored-program technique.
According to Von Neumann theory "data and program can be
stored in the memory of computer for automatically performing the operations. Thus the machine can
itself alter either its program or data". EDVAC, "Electronic Discrete Variable Automatic Computer" was
designed on stored program concept by Dr. John Von Neumann. It could store programs and perform
arithmetic and logical operations. The programs and data were fed in this computer through punched
paper tape. The machine was mainly served as a laboratory model to test many of the notions of
programming and coding used in modern computers.
Von Neumann also introduced the idea of storing both instructions and data in the binary form. The Von
Neumann theory was universally adopted. So the computing and programming became much faster and
efficient. The theory also became essential for future generation of high-speed digital computers.
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EDSAC (1947 - 1949)
EDSAC stands for "Electronic Delayed Storage Automatic
Computer". It was developed in 1949 at Cambridge University
by groups of scientists headed by Professor Maurice Wilkes.
UNIVAC-1 (1951)
UNIVAC stands for Universal Automatic Computer. It was also developed by J.P. Eckert & John Mauchly
(designers of ENIAC) in 1951. It was the first digital computer. The programs and data were fed in this
computer through magnetic tape.
In 1952, the International Business-Machines (IBM) Corporation introduced the 701 commercial
computers. After this, improved models of the UNIVAC and other 700-series machines were introduced.
In 1953, IBM produced the IBM-650 computer and sold over 1000 of these computers.
Figure: 1.7 UNIVAC01 Computer Figure: 1.8 UNIVAC02 Computer
Generations of Computers
The term generation indicates the stages of evolution or development of computers based on the type of
technology used in the computer construction over a period of time. As new technology was emerging, it
was being used in the making of computer. The new technology improved the speed, accuracy and
storage capacity of the computers. Different technologies have been used for computers in different times.
The computer system belonging to one particulars technological class or trade, that has certain common
characteristics is said to be of a particular generation. Each new generation has made the following
changes in computer characteristics:-
a. Increased speed
b. Increased storage capacity
c. Increased reliability
d. Reduced size of a computer
e. Reduced cost of a computer
Depending upon the device technology, system architecture, processing mode and language used,
computers are broadly categorized into Five Generation.
Therefore, computers can be divided into five generations depending upon the technologies used. These
are:
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a. First Generation (1946 - 1956)
b. Second Generation (1956 - 1965)
c. Third Generation (1965 - 1973)
d. Fourth Generation (1973 - 2020)
e. Fifth Generation (2020 and beyond)
First Generation Computers (1946 - 1956)
The computers developed between 1946-1956 was the first generation computer. In this generation
Vacuum tubes were used for electrical current flow between
electrodes and magnetic drums for memory. Entire machine is
dedicated to a particular job until the completion of work. In
this generation everything was handled manually by the
human operator. The technology Vacuum tube was invented
by John Ambrose Fleming in 1904.
Features
a. Vacuum Tubes for circuitry and magnetic drum for primary memory.
b. Punched card for input.
c. Printout display for output.
d. Magnetic Tape for storage memory (Secondary memory).
e. Limited storage capacity (1KB-4KB).
f. Large in size (Occupied more than one room).
g. Slow and expensive.
h. Generated large amount of heat.
i. Used machine language.
j. First generation computers were used only for Scientific and Research purpose.
Examples: - ENIAC, EDVAC, UNIVAC-I/II, IBM 650,702, 705 etc.
Advantages
The main advantages of first-generation computers were:
a. These computers were the fastest of their time.
b. They were programmed using machine language.
c. The electronic digital computers were introduced due to the vacuum tube technology.
Disadvantages
The main disadvantages of first-generation computers were:
a. Very big in size
b. Not reliable
c. Consumed large amount of energy (Electricity)
d. Constant maintenance required and short life
span
e. More heat generated and air-conditioning was required
f. More costly
g. Very slow in speed (data processing)
h. It was difficult to program, because they used only machine language
i. Non-portable and occupied large space
j. Limited commercial use
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Second Generation Computers (1956-1965)
The transistor technology was used in second-generation computers. The electronic component transistor
was invented in December 23, 1947 by William Shockley, John
Bardeen and Walter Brattain at Bell Laboratories in Murray Hill,
New Jersey, USA. The transistor is smaller in size, fast and more
reliable than vacuum tube. Therefore, the transistor technology
was used in computer in place of vacuum tube technology. The
assembly language was also introduced in second-generation of
computers. Multiple users were capable of using the machine
concurrently. Computers were used manually by the operator.
Features
a. Transistor used for electric circuitry.
b. Magnetic core memory for internal storage purpose.
c. Magnetic tape for external storage.
d. At beginning assembly language and at the end used High Level Language (COBOL, FORTRAN).
e. Reduced size and cost of a computer.
f. Larger storage capacity.
g. Heat generated by the computer.
h. Punched card for input.
i. Printout for output.
Examples: IBM 1401, 7030, 7050, GE 635, 200, 400 series etc.
Advantages
The main advantages of second-generation computers as compared to first-generation computers are:
a. Low cost
b. Smaller in size
c. Fast in speed
d. Less heat generated, more reliable and accurate in calculations
e. Consumed low power
f. Used for commercial purposes
g. Portable than first generation
h. Assembly language was introduced. This language is easy to write program than machine language
Disadvantages
The main disadvantages of this generation computers were:
a. Air-conditioning required
b. Commercial production was difficult and these were very costly
c. Constant (or frequent) maintenance required
d. Only used for special purposes
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Figure: 1.9 Transistors
Third Generation Computers (1965-1973)
The computers developed between 1965-1973 were the Third generation computers. In this generation
Integrated Circuits (IC) were used for
memory and processing units. Many
transistors are placed on Silicon chips,
which drastically change the speed and
efficiency of computers. Computers
included significant advances in
machine hardware along with heavy
emphasis on software. Computer
programs designed to make the
machine work. Operating System (OS)
developed which provided capabilities for automatic proceeding from one job to the next without human
intervention and for multiprogramming which made it possible for a machine to perform several jobs
concurrently. The concepts of computers “Families” were introduced. The IC was invented in September
12, 1958 by Jack Kilby.
Features
a. IC (SSI & MSI) is used for memory and processing units
b. Semiconductor memory for internal storage.
c. Keyboard for input
d. Monitor for Output.
e. Started to use operating System.
f. Processor speed in nanoseconds.
g. Reduced size, cost and more reliable.
h. Used high level language.
i. Magnetic disk for external storage.
j. Minicomputer introduced.
k. Intel 4004 chip developed in 1971.
Example, IBM 360 & 370 series, PDP-8 series, CDC-7000 & 7600 series
Advantages
The main advantages of third-generation as compared to previous generations of computers were:
a. Smaller in size
b. Production cost was low
c. Very fast in computational power
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d. More reliable
e. Low power consumption
f. Maintenance cost was low because failure rate of hardware was very low
g. Magnetic disk used for external storage
h. More storage capacity
i. Easily portable
j. Easy to operate
k. Easy to upgrade
l. Widely used for various commercial applications all over the world
m. Low amount of heat generated
n. High-level languages were commonly used
o. Many input/output devices were introduced such as mouse and keyboard etc.
Disadvantages
The main disadvantages of third-generation computers were:
a. Air-conditioning required
b. Highly sophisticated technology required for manufacturing chips
Figure: 1.10 Chip 01 Figure: 1.11 Chip 02
Fourth Generation Computers (1973-2020)
The computers developed between 1973-2020 were the fourth generation computers. The significant
distinction of the fourth generation is the development of LSI
and VLSI (thousands and hundred thousand transistors on
single chips). These developments were followed by creation of
microprocessors. Hundreds of circuits may be placed on a chip
of the size of a pinhead. Thus due to the use of microprocessor,
fourth-generation may be called Microcomputer generation. The
single chip Microprocessor invented in 1968 by Gilbert Hyatt.
IBM introduced its personal computer for use in 1981.
Features
a. Microprocessors having LSI and VLSI technology with multi-processor based system.
b. Semiconductor memory.
c. Storage capacity drastically increased (TBs).
d. Versatile input and output devices used.
e. Smaller in size, more reliable, and reduced cost.
f. Very user friendly.
g. High end speed microprocessors (Intel Core i9-9900KS, AMD's 16-core Ryzen 3950X and AMD Ryzen
7 1800X).
h. 4 GL languages.
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i. Used microcomputers (Laptop, Notebook, and PDA).
j. Decrease in used of Desktop.
Examples: IBM PCs, Remits II/III, Alpha, Intel PCs, Macintosh PCs, Portable hand held computer
etc.
Advantages
The advantages of fourth-generation as compared to previous generation computers are:
a. Smaller in size (Fully portable computer)
b. Production cost is very low
c. Very reliable
d. Hardware failure is negligible
e. Easily portable because of their small size
f. Totally general purpose
g. Air conditioning is not compulsory
h. Very high processing speed (8-cores chip)
i. Very large internal and external storage capacity (GBs and TBs)
j. Advanced memory, input & output devices such as portable hard disk, optical readers, laser printers,
CD-ROM/DVD-ROM drives, memory card, pen drive etc.
Disadvantages
The main disadvantages of fourth-generation computers is:
a. Highly sophisticated technology required for the manufacturer of
microprocessor chips
Fifth Generation Computers (2020 and beyond)
Computers based on Artificial Intelligence (AI) are known as fifth generation computers. This generation
computers are capable of billions of calculations per second and they can
“think” and “reason” with further specialization of computer hardware.
AI can be described as a branch of computer science that is involved with
using computers to solve problems that appear to require human
imagination or intelligence. The researchers have used concept from
disciplines such as Linguistics, Psychology and Computer science in an
attempt to learn, how to prepare programs or construct systems that do
tasks which no machine has ever automatically done before.
AI in action is the use of expert systems. AI expert system is software (S/W) package that attempts to
encode the knowledge and decision rules established by human specialists so that package users can call
on this expertise in making their own decisions.
Features
a. Use of ULSI (Millions of transistors in chip) technology.
b. AI programming (PROLOG and LISP).
c. Knowledge based problem solving technique.
d. High performance multiprocessor system.
e. Input and output in the form of speech and graphics images.
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f. Able to understand natural language like English, Japanese etc.
g. Future vision system in computer.
h. Having their own thinking power
i. Having capacity to make decisions itself
j. Having capabilities of learning
k. Having capabilities of reasoning
l. Having large capacity of internal storage
m. More powerful multi-processor based system
n. May be used biochips as a processing unit.
o. May used quantum computation, molecular and nanotechnology.
p. May be used of Neural Networks
This type of generation computers are still in research phase and, it could take a little more time to
become a reality.
COMPUTER SPEED AND MEASUREMENT UNIT
Computer speed and its measurement can be taken in different ways:
Bit Width
The first way of describing a processor is to say how many bits it processes in a single instruction or
transports across the processor's internal bus in a single cycle (not exactly correct, but close enough). The
number of bits used in the CPU's instructions and registers and how many bits the buses can transfer
simultaneously is usually expressed in multiples of 8 bits. It is possible for the registers and the bus to
have different sizes. Current chip designs are 64 bit chips (as of 2008). More bits usually mean more
processing capability and more speed.
Clock Cycles
The second way of describing a processor is to say how many cycles per second the chip operates at. This
is how many times per second a charge of electricity passes through the chip. The more cycles, the faster
the processor. Currently, chips operate in the billions of cycles per second range. When you're talking
about billions of anything in computer terms, you're talking about 'giga' something. When you're talking
about how many cycles per second, you’re talking about 'hertz'. Putting the two together, you get
gigahertz. More clock cycles usually means more processing capability and more speed.
Execution Cores
The third way of describing a processor is to say how many execution cores are in the chip. The most
advanced chips today have eight execution cores. More execution cores means you can get more work
done at the same time, but it doesn't necessarily mean a single program will run faster. To put it another
way, a processor with one execution core might be able to run your MP3 music, your web browser, a
graphics program and that's about where it starts to slow down enough, it's not worth it running more
programs. A system with a processor with 8 cores could run all that plus ten more applications without
even seeming to slow down (of course, this assumes you have enough RAM to load all of this software at
the same time). More execution cores mean more processing capability, but not necessarily more speed. As
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of 2020, the most advanced processors (Intel Core i9-9900KS) available are 64-bit processors with 8 cores,
running as fast as 5.0 gigahertz. Intel Core i9-9980XE has released 18-cores and 36-threads. It absolutely
destroys all its competitors on the market.
CPU Speed Measurements
The main measurement quoted by manufacturers as a supposed indication of processing speed, is the
clock speed of the chip measured in hertz. The theory goes that the higher the number of mega or
gigahertz, the faster the processor.
However comparing raw speeds is not always a good comparison between chips. Counting how many
instructions are processed per second (MIPS, BIPS, and TIPS for millions, billions and trillions of
instructions per second) is a better measurement. Still others use the number of mathematical calculations
per second to rate the speed of a processor.
Of course, what measurement is most important and most helpful to you depends on what you use a
computer for. If you primarily do intensive math calculations, measuring the number of calculations per
second is most important. If you are measuring how fast the computer runs an application, then
instructions per second are most important.
Bandwidth
Bandwidth is the capacity of any communications link to transmit the maximum amount of data from one
point to another over a computer network or internet connection in a given amount of time -- usually, one
second. Synonymous with capacity, bandwidth describes the data transfer rate. Bandwidth is not a
measure of network speed. It means the amount of information that can be sent each second over a
network connection. Bandwidth can be measured in terms of bps, Kbps, Mbps, or Gbps.
Storage Unit
In computer the information, data, software, or anything that are store in memory. Their storage capacity
is measured in terms of either:
Unit Abbreviation Storage
● Bit b 1or 0
● Nibble - 4 bits
● Byte B 8 bits
● Kilobyte KB 1024 B
● Megabyte MB 1024 KB
● Gigabyte GB 1024 MB
● Terabyte TB 1024 GB
● Petabyte PB 1024 TB
● Exabyte EB 1024 PB
● Zettabyte ZB 1024 EB
● Yottabyte YB 1024 ZB
● Bronobyte BB 1024YB(Unofficial)
● Geopbyte GpB/GeB 1024BB (Unofficial)
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CLASSIFICATION OF COMPUTER
Classification means a system of arranging something (devices) in different groups according to their
common characteristics, uses or operating principle. Computers, also, can be classified based on their
processing speed, amount of data that they can hold; purpose of the computer, and working principles.
Generally, a computer with high processing speed and large internal storage is called a large computer,
while the others are called small or medium sized computers. Due to rapidly improving technology, we
are always confused among the categories of computers. Categorization makes the simple and easy.
Although computers are classified into various ways. Here we are discussing only on the basis of size and
speed.
Size of computer indicates the processing speed and storage capacity. On the basis of size, computers are
classified into following four main groups.
1. Microcomputer.
2. Minicomputer.
3. Mainframe computer.
4. Supercomputer.
So, the selection of particular computer depends on the purpose or use, the volume of data to be handled
and the speed of operation required etc.
Microcomputer
A microcomputer is a smallest general purpose processing system. It is a self contained unit designed
specially for the use by one person at a time. The microcomputers are also known as personal computers
or simply PCs. Microprocessor is used in this type of computer. These are very small in size and cost. The
IBM’s first microcomputer was designed in 1981 and was named as IBM-PC. After this many computer
hardware companies copied the design of IBM-PC. The term “PC-compatible” refers to any personal
computer based on the original IBM personal computer design. Microcomputer means having
microprocessor as a processing unit.
The most popular types of personal computers are the PC and the Apple. PC and PC-compatible
computers have processors with different architectures than processors in Apple computers. These two
types of computers also use different operating systems. PC and PC-compatible computers use the
Windows operating system while Apple computers use the Macintosh operating system (MacOS). The
majority of microcomputers sold today are part of IBM-compatible. However the Apple computer is
neither an IBM nor a compatible. It is another family of computers made by Apple computer. Now IBM is
change into Lenovo.
Personal computers are available in two models. These are:
1. Desktop PCs
2. Tower PCs
Figure: 1.12 Desktop PC Figure: 1.13 Tower PC
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A desktop personal computer is most popular model of personal computer. The system unit of the
desktop personal computer can lies flat on the desk or table. In desktop personal computer, the monitor is
usually placed on the system unit.
Another model of the personal computer is known as tower personal computer. The system unit of the
tower PC is vertically placed on the desk or table. Usually the system unit of the tower model is placed on
the floor to make desk space free and user can place other devices such as printer, scanner etc. on the
desktop. The tower models are mostly used at homes and offices. Now both the personal desktop
computers are used in offices, rarely in individual personally.
Microcomputers are further divided into following categories.
1. Laptop computer
2. Note book
3. Palmtop (Handheld computer)
a. Personal Digital Assistance
b. Cellular telephones
Laptop Notebook Palmtop PDA Cellular Phone
Further classification of computer is on the basis of size. These computers are in the name of Laptop,
Notebook, and Palmtop. Their size is in decreasing order. They are portable- means easy to carry from
place to place. Their cost is expensive as compare to desktop. Other than desktop their differences are on
the basis of their use and specification of a particular type of microcomputer. Their cost is varies with the
company and specification.
Minicomputers
These are smaller in size, have lower processing speed and are cheaper than mainframe. These computers
are known as minicomputers because of their small size as compared to other
computers at that time. The capabilities of a minicomputer are between
mainframe and personal computer. It handles more than 100 workstations at a
time. So, it is a multi-user or multi-terminal time sharing system. These
computers are also known as midrange computers.
The minicomputer size prevents it from being portable, but it can be moved more
easily than mainframe computers. Mini computers integrate commercial and
technical operations better than the more powerful PCs and are easier to use. The
minicomputers are used in business, education and many other government
departments. Although some minicomputers are designed for a single user, but
most are designed to handle multiple terminals. Minicomputers are commonly used as servers in network
environment or a data processing system in a medium large organization, and hundreds of personal
computers can be connected to the network with a minicomputer acting as server. Like mainframes,
minicomputers can also be used as web servers. Single user minicomputers are used for sophisticated
design tasks.
The first minicomputer was introduced in the mid-1960s by Digital Equipment Corporation (DEC). After
this IBM Corporation (AS/400 computers) Data General Corporation and Prime Computer also designed
the mini computers.
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Mainframe Computers
Mainframe computers are large-scale computers, but supercomputers are larger than mainframe. The
mainframe computer specially requires a very large clean room with air-conditioner. This makes it very
expensive to buy and operate. It can support a large number of various equipments. It also has multiple
processors. They can process data at several million instructions per second (MIPS) and more than 1,000
remote workstation can be accommodated by a typical mainframe computer. Large mainframe systems
can handle the input and output requirements of several thousands of users. The users often access the
mainframe with terminals or personal computers. There are basically two types of terminals used with
mainframe systems. These are:
i. Dumb Terminal
Dumb terminal does not have its own CPU and storage devices. This type of terminal uses the CPU
and storage devices of mainframe system. Typically, a dumb terminal consists of monitor and a
keyboard (or mouse).
ii. Intelligent Terminal
Intelligent terminal has its own processor and can perform some processing operations. Usually, this
type of terminal does not have its own storage. Typically,
personal computers are used as intelligent terminals. A
personal computer as an intelligent terminal gives facility to
access data and other services from mainframe system. It
also enables to store and process data locally.
The mainframe computers are specially used as servers on
the World Wide Web. The mainframe computers are used in
large organizations such as Banks; Airlines and Universities
as a central host computer; where many people (users) need
frequent access to the same data, which is usually organized into one or more huge databases. IBM is
the major manufacturer of mainframe computers. The examples of mainframes are IBM S/390,
Control Data CYBER 176 and Amdahl 580, IBM 4381, UNIVAC 1100/60 etc.
Supercomputer
Supercomputer is the most powerful and fastest, and also very expensive. It was developed in 1980s. It is
used to process large amount of data and to solve the complicated scientific problems. It can perform more
than one trillion calculations per second. It has large number of processors connected in parallel. So,
parallel processing is done in this computer. In a single supercomputer 10 thousands of users can be
connected at the same time and the supercomputer handles the work of each user separately.
Supercomputers are mainly used for:
● Weather forecasting.
● Nuclear energy research.
● Aircraft design.
● Automotive design.
● Online banking.
● Industrial control units.
● Aerodynamic design and simulation.
● Processing of geological data and genetic coding,
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The supercomputers are used in large organizations,
research laboratories, aerospace centers, large industrial
units etc. Nuclear scientists use supercomputers to create
and analyze models of nuclear fission and fusions,
predicting the actions and reactions of millions of atoms as
they interact. Super computers can be used for server but
not used because of its costs. It is manufacture for specific
purpose and not develop by common manufacturing
companies. The examples of supercomputers are CRAY-1,
CRAY-2, CYBER 205, Nec Super, CDC-star 100, Param etc.
MOBILE COMPUTING
Mobile computing is a generic term describing one's ability to use technology while moving, as opposed to
portable computers, which are only practical for use while deployed in a stationary configuration. It is a
technology that allows transmission of data, via a computer, without having to be connected to a fixed
physical link. Mobile computing embraces a host of portable technologies that make Internet access on the
go not only possible, but integral to everyday life.
Mobile computingis "taking a computer and all necessary files and software out into the field. Many types
of mobile computers have been introduced since the 1990s.
Mobile computing refers to the use of small and portable computing devices in wireless enabled networks
that provide wireless connections to a central main server. These devices include laptops, notebook PCs,
tablet PCs, palmtops (personal digital assistant (PDAs) and other hand held devices). A radio-signaling
device is installed inside these devices for receiving and transmitting electronic data. Mobile computing
has become an indispensable part of life.
Mobile laptop, notebook and palmtop computers can use one of the types of wireless access services when
away from the home or office. The most commonly used and least expensive is Wi-Fi. Wi-Fi uses radio
waves to broadcast an Internet signal from a wireless router to the immediate surrounding area. If the
wireless network is not encrypted, anyone can jump on. Wi-Fi is commonly used in public places like
airport terminals, hotel lounges, and some specific government public places to create “hotspots.”
An alternative to Wi-Fi is cellular broadband. This type of mobile computing technology utilizes a cellular
modem or Air Card to connect to cell towers for Internet access. The Air Card fits into the PC Card or
Express Card slot of a notebook or laptop, delivering Internet access on the go. One needn’t remain
stationary to use cellular broadband as the signal will remain strong everywhere within the range.
Cellular broadband is also used for providing Internet access to cell phones and PDAs. Access is usually
considered a premium service that either increases the monthly cost of the plan associated with the device,
or incurs extra fees when used.
Another service associated with mobile computing is cloud computing, or the ability to use website
services from mobile computers. Cloud computing provides access to a network-like environment with
various applications and virtually unlimited resources so that field representatives, for instance, can utilize
website resources rather than being supplied with weighty, expensive machines packed with company
software and data. Mobile computing also provides access to a company’s virtual private network (VPN)
by tunneling through the Internet. Staying connected through mobile computing has become completely
integrated into the fabric of everyday life in developed countries. From email to Twitter, from Skype to
socializing sites, from cloud computing to VPNs, we could no longer do without mobile computing
anymore than we could do without electricity.
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Computer System Unit 1 … 29.
Wireless networks use Wi-Fi (wireless fidelity) technology for providing network coverage to offices,
public places, and other small workplaces. A wireless access point device is used to provide wire free
network coverage in the designated area.
WiMax (Wireless Interoperability for Microwave Access) technology represents the next generation of
wireless networking and can transmit data up to a distance of 50-90 km. It can provide a maximum
networking speed of 70 Mbps. It provides much better facilities than Wi-Fi such as long distance
microwave technology, higher bandwidth and high data security by using enhanced encryption schemes.
It can provide service in both Line Of Sight (LOS) and Non-Line of Sight (NLOS) locations, but range may
vary accordingly.
Mobile computing devices can use any of these networks to access the Internet or connect to a LAN (local
area network) or WAN(wide area network) server. They use networking software for adjusting device
settings to suit specific network requirements. Mobile computing has enabled users to remain connected
while on the move. High end users can opt for satellite based networking which provides wireless
connectivity anywhere in the world.
Features
● Easy to handle and carry these small devices.
● Data can be transferred easily between users.
● Collect simulated data to current zone or your time.
● Arbitrary network, easily connect to other environment and transmit data.
● Having fast processor speed.
● Good battery life.
● Huge memory capacity.
● No time constraints
● No place constraints
● Reduced costs and time etc
Applications
● Traffic control and information
● Emergencies Situation
● Use in Business
● Credit Card Verification
● Replacement of Fixed Networks
● Entertainment
● Construction
● Defense
● Airlines industry
● Banking
● Medical
● Rural area
● News reporting
● Health care
● Education etc
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Technical and other limitations of mobile computing
● Insufficient bandwidth
● Security threats
● Battery power
● Transmission interferences
● Potential health hazards
● Small interface devices
● Network stability.
COMPUTER ARCHITECTURE AND ORGANIZATION
Computer Architecture
Computer Architecture is about designing the internal organization of a computer system to meet a given
set of requirements as efficiently as possible within economic and technological limits. Simply adding
more resources to a computer system does not make it any faster. Organizing them in the right way so that
they can be used efficiently and in a collaborative manner is what makes a faster computer. Design
alternatives appear at all levels of a computer system, from the internal processor configuration, to the
integration board, to the whole system interconnection. Finding the right balance between all design
options, and proposing new design alternatives is the task of the computer architect.
In fact, computer architecture refers to those attributes of a system visible to a programmer. This means, it
includes those attributes that have a direct impact on the logical execution of a program. Computer
architecture emphasizes the engineering decisions and tradeoffs that must be made in order to produce a
"good" design. The computer architect answers questions like:
● How many registers should there be?
● What machine instructions should there be?
● How should the cache be organized?
● What hardware support should there be for virtual memory?
Computer scientists used three related terms to describe the general area of low-level machine
organization. Computer architecture is the study of the components that make up computer systems and
how they are interconnected. Computer organization is concerned with the implementation of computer
architecture. Computer engineering refers to the actual construction of a system: lengths of wires, sizes of
circuits, cooling and electrical requirements, etc. Programmers often use knowledge of a system's
architecture, and sometimes organization, to optimize performance of their programs, but rarely, if ever,
are they concerned with engineering aspects.
"Architecture" therefore typically refers to the fixed internal structure of the CPU (i.e. electronic switches
to represent logic gates) to perform logical operations, and may also include the built-in interface (i.e. op-
code) by which hardware resources (like CPU, memory, motherboard, and peripherals) may be used by
the software.
Levels within the computer architecture
a. The simplest distinction between levels that between hardware and software. The hardware, the
lowest and most basic level of computer onto which a layer of software is added. The software sits
above the hardware, using it and controlling it. The hardware supports the software sits above by
providing the operations the software requires.
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Computer System Unit 1 … 31.
b. Multi-Layered computer architecture consists of several layers and software on top of the hardware
level.
The computer architecture layer of H/W and S/W are further layer into first four denote as a H/W
layer and remaining three layer are S/W layer. These layers are briefly mentioned here:
● The Physical Device Layer (1st level) consists of electrical (power supply) and electronic
components such as transistors (acts as electronic switch that is either ON (1) or OFF (0)),
capacitors, and resistors, and these components rely on suitable power supplies and operating
environment. It is responsible for the actual physical connection between the devices. The
physical layer contains information in the form of bits and these bits are send to upper layer
digital logic layer.
● The Digital Logic Layer (2nd level) can store, manipulate and transmit data in the form of simple
binary representations forming frame and send towards the microprogramming layer. Digital
logic elements are called gates. A gate is normally constructed from a small number of transistors
and other electronic components.
● The Microprogramming Layer (3rd level) interprets the machine language instructions from the
machine layer and directly caused the digital logic elements to perform the required operations.
Likewise sends towards the machine layer as a packet for routing.
● The Machine Layer (4th level) is the level at which program can be written and indeed it is only
machine language instructions, which can be directly interpreted by the hardware.
● The Operating System Layer (5th level) controls the way in which all software uses the
underlying hardware. It also hides the complexities of the hardware from other software by
providing its own facilities, which enable software to use the hardware more simply. It also
prevents other software from bypassing these facilities so that the hardware can only be accessed
directly by the operating system.
● The Higher Order Software Layer (6th level) covers all programs in language other than machine
language, which require translation on to machine code before they can be executed. Such
programs when translated rely upon the underlying operating system facilities as well as their
own machine instructions.
● The Application Layer (7th level) is the language of the computer as seen by the end user. Here is
the layer where we used to communicate (interface) with the system. Although computer
applications sometimes require only desktop resources, applications may unite communicating
components from more than one network applications; for example, file transfer, e-mail, remote
access, network management activities, client/server process, etc.
7 Application layer
6 Software level Higher order software level
5 Operating System Layer
4 Machine Layer
3 Hardware level Microprogramming Layer
2 Digital Logic Layer
1 Physical Device Layer
The underlying computer as viewed from each layer is sometimes called a virtual machine design
according to the OSI model.
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Computer Organization
Computer Organization refers to the level of abstraction above the digital logic level, but below the
operating system level. At this level, the major components are functional units or subsystems that
correspond to specific pieces of hardware built from the lower level building blocks. Therefore, computer
organization refers to the operational units and their interconnections that realize the architectural
specification. Organizational attributes include those hardware details visible to the programmer, such as
control signals, interfaces between the computer and the peripherals, and the memory technology used.
Computer Organization is concerned with the way the hardware components operate and the way they
are connected together to form a computer system.
The classic description of a computer's organization is attributed to John von Neumann (1903-1957),
though his original description of a machine named the EDVAC was far more complex. The Von
Neumann model is characterized by five major subsystems:
1. Input
2. Arithmetic-logic unit (ALU)
3. Control unit
4. Memory
5. Output
According to Von Neuman model, a computer is organized in such a way that it should be able to perform
the following four functions;
1. Receive input information from outside world.
2. Process the information
3. Produce output to communicate with the outside world, and
4. Store information for future reference
COMPONENTS OF COMPUTER SYSTEM
The computer system is a complex system basically having two distinct components hardware and
software. Here we are talking only hardware components. It provides the physical structure of a computer
system. The internal architectural design of computers differs from one system model to another.
However the basic components and their functions are same for all computer systems. Each component
performs a specific function in the computer. As discussed earlier, the computer receives information,
processes it, produces output and stores it for future reference. Therefore, a computer should have at least
four major components to perform these four tasks. A typical digital computer capable of performing
these tasks can be illustrated with the help of the following block diagram;
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