An Overview of Information Technology and its Application in Business 8173815526, 9788173815522

Table of contents :
COVER
CONTENTS
PREFACE
ACKNOWLEDGEMENTS
Chapter 1 Information Revolution and Information Technology
Chapter 2 Fundamentals of Computers
Chapter 3 Numbering Systems and Digital Codes
Chapter 4 Computer Arithmetic and Boolean Algebra
Chapter 5 Computer Processing System
Chapter 6 Input-output Devices and Storage Devices
Chapter 7 Operating System-DOS AND WINDOWS
Chapter 8 Computer and Networks
Chapter 9 Word Processing
Chapter 10 Electronic Spreadsheet
Chapter 11 Database Management Systems (DBMS)
Chapter 12 Electronic Data Interchange (EDI)
Chapter 13 The Internet and Its Basic Concepts
Chapter 14 Information System Audit
APPENDIX A E-COMMERCE AND FLOW CHARTS
APPENDIX B SHORT QUESTIONS
APPENDIX C ABBREVIATIONS

Citation preview

An Overview of

Information Technology and Its Application in Business

"This page is Intentionally Left Blank"

An Overview of

Information Technology and Its Application in Business

Madan Mohan Jana MCom, AICWA Susi! Kar College, Champahati, South 24 Parganas

Nab in Kumar Samanta

MCom, MA (Eco), LLB, AICWA, DCA

Dinabandhu Andrews College, Garia, Kolkata

New Central Book Agency (P) Ltd LONDON HYDERABAD ERNAKULAM BHUBANESWAR DELHI KOLKATA PUNE GUWAHATI

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An Overview of Information Technology and Its Application in Business • Jana and Samanta

© Copyright reserved by Smt. Soma Samanta and Smt. Rekha Rani Jana Publication, Distribution, and Promotion Rights reserved by the Publisher All rights reserved. No part of the text in general, and the figures, diagrams, page layout, and cover design in particular, may be reproduced or transmitted in any form or by any means--electronic, mechanical, photocopying, recording, or by any information storage and retrieval system-without the prior written permission of the Publisher First Published: 2007 Reprinted: 2009, 2013 PUBLISHER

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Dedicated to Our Grand Parents Late Laxmipriya Samanta Late Iswar Chandra Samanta Late Rudranarayan Jana Late Bharati Jana

who taught us the first lesson of life

"This page is Intentionally Left Blank"

CONTENTS xix xxi

Preface Acknowledgements

1. Information Revolution and Information Technology 1.0 l.l 1.2 1.3

Introduction Definition of Information Technology Important Features of Information Technology Role/impact of Information Technology on Business Environment and Social Fabric 1.4 Invention of Writing 1.4.1 Invention of Books and Printing Press 1.4.2 Impact of Gutenberg's Contribution

1.5 Radio Communication 1.5.1 1.5.2 1.5.3 1.5.4

Elements of Radio Communication Featuers of Radio Communication Advantages of Radio Communication Limitations of Radio Communication

1.6 Telephone Communication 1.6.1 Basic Elements of Telephone Communication 1.6.2 Features of Telephone Communication 1.6.3 Advantages of Telephone Communication

1.7 Wireless Communication 1.7.1 1.7.2 1.7.3 1.7.4

Elements of Wireless Communication Basic Features of Wireless Communication Advantages of Wireless Communication Limitations of Wireless Communication

1.8 Satellite Communication 1.8.1 1.8.2 1.8.3 1.8.4

Basic Elements of Satellite Communication Features of Satellite Communication Advantages of Satellite Communication Limitations of Satellite Communication

1.9 Desktop Publishing (DTP) 1.9.1 Features of DTP 1.9.2 Advantages of DTP 1.9.3 Disadvantages of DTP

l.10 Wireless Application Protocol (WAP)

1-10 3 3 3 4 5

5 6 6 6 6 6 7 7 7 7 7 7 7 8 8 8 8 8

8 8 8 9 9 9 9 9 9 9 10 10

1.10.1 Basic Features of WAP 1.10.2 Advantages of WAP 1.10.3 Disadvantages of WAP

Exercises

[vii]

2. Fundamentals of Computers

11-24

2.0 Data, Information and Electronic Data Processing (EDP) 2.1 Data-Definition

13 13

2.1.1 Elements of Data Processing 2.1.2 Need of Data/Data Processing 2.1.3 Concept of Data 2.1.4 Logical Concept of Data 2.2 Data Processing

13 14 14 15 15

2.2.l Data Processing Cycle 2.2.2 Data Processing Operation 2.3 Methods of Data Processing

16 17 17

2.3.l Manual Data Processing System 2.3.2 Electromechanical System 2.3.3 Electronic Data Processing System 2.3.4 Computerised Management Information System (CMIS) 2.3.5 Decision Support System (DSS) 2.3.6 Expert System (ES) 2.4 Information

17 17 18 19 19

2.4.1 2.4.2 2.4.3 2.4.4 2.4.5 2.4.6 2.4.7

Concept of Information Need of Information Factors on which Requirements of Information Depend Features of Good Quality Information Levels of Information Value of Information Difference Between Data and Information

3. Numbering Systems and Digital Codes

24

25-60 27 27

Introduction Concepts of Number System Decimal Number System Binary Number System

3.3.1 Reasons for using Binary Number System 3.3.2 Conversion of Decimal Number into Binary Number 3.4 Octal Number Systems 3.4.l Conversion of Octal Numbers to Decimal Numbers 3.4.2 Conversion of Decimal Numbers to Octal Equivalence 3.5 Hexadecimal Number System 3.6 Conversion from one System to another System 3.6. l 3.6.2 3.6.3 3.6.4

20 21 21 22 22 23

24

Exercises

3.0 3.1 3.2 3.3

20 20

Octal-Binary Conversion Binary-Octal Conversion Octal-Hexadecimal Conversion and Vice Versa Hexadecimal-Binary Conversion and Vice Versa [ viii]

28 29 29 31 34

34 34 38

42 43 44 45

47

51

3.7 Data Representation 3.7.1 Data Types 3.7.2 Fixed Point Data Representation 3.7.3 Floating Point Data Representation

3.8 Digital Coding 3.8.1 Major Requirements for a Coding System 3.8.2 Features of a Good Coding System

3.9 3.10 3.11 3.12

Binary Coded Decimal (BCD) Extended Binary Coded Decimal Interchange Code (EBCDIC) American Standard Code for Information Interchange (ASCII) Gray Code 3.12.1 Typical Application of Gray Code 3.12.2 Adyantages of Gray Code

Exercises

4. Computer Arithmetic and Boolean Algebra Binary Binary Binary Binary Binary

Addition Subtraction Subtraction by Addition Method Multiplication Division

4.2 Octal Arithmetic 4.2. l Octal Addition 4.2.2 Octal Subtraction

54 55 58 58 59 59-60

61-88 63 64

65 67 68 69 69 69 70

4.3 Hexadecimal Arithmetic

70, 70 71

4.3.l Hexadecimal Addition 4.3.2 Hexadecimal Subtraction

4.4 Boolean Algebra 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5 4.4.6

53 53 53 53

63

4.1 Binary Arithmetic 4.1.1 4.1.2 4.1.3 4.1.4 4.1.5

51 52 52

Definition Fundamental Theorem of Boolean Algebra Principles. of Duality Boolean Functions Truth Table Canqnical or Standard Form of a Boolean Function 4.4.6.1 Disjunctive Normal Form (D.N.F.) 4.4.6.2 Procedure of Conversion of a Function in D.N.F. 4.4.6.3 Construction of a Boolean Function in D.N.F. from a Truth Table 4.4.6.4 Conjunctive Normal Form (C.N.F.) 4.4.6.5 Full Conjunctive Normal Form (F.C.N.F.) 4.4.6,6 Complete Conjunctive Normal Form (C.C.N.F.) 4.4.6.7 Construction of a Boolean Function in C.N.F. from a Truth Table

[ix]

71 71 72

74 74 75 75 75

76 77 77 77 77

4.4.7 Minterm and Max.term Form of a Boolean Function 4.4.8 Switching Circuits 4.4.8.1 NOT Gate 4.4.8.2 AND Gate 4.4.8.3 NAND Gate 4.4.8.4 OR Gate 4.4.8.5 NOR Gate 4.4.8.6 INCLUSIVE-OR Gate 4.4.8.7 EXCLUSIVE-OR Gate 4.4.9 Minimisation of Boqlean Function and Circuits 4.4.10 Kamaugh Map (K-M) Method

Exercise 1 Exercise 2

78

79 79 80 80 81 81

82 82 84 84 85-86 86-88

5. Computer Processing System

89-108

5.0 Introduction 5.1 Hardware

91 91

5.1.1 CPU (Central Processing Unit) 5.1.2 Three Components of CPU 5.1.2.1 Control Unit 5.1.2.2 Sequence of Control Unit 5.1.2.3 Important Functions of Control Unit 5.1.2.4 Arithmetic Logic Unit (ALU) 5.1.2.5 Important Functions of ALU 5.1.2.6 Primary Storage Unit or Main Memory 5.1.2.7 Important Features of the Main Memory

5.2 Software

92 92 92 92 93 93 93 93 94 95 95

5.2.1 System Software 5.2.2 Application Software 5.2.3 Peopleware

5.3 Program Language 5.3.1 Low Level Language 5.3.1.1 Machine Language 5.3.1.2 Assembly Language 5.3.2 High Level Language 5.3.2. l General Purpose Language 5.3.2.2 Special Purpose Language 5.3.3 Compiler 5.3.4 Interpreter

5.4 Comparison between Interpreter and Compiler 5.5 Comparison between High Level Language and Assembly Language 5.6 Some High Level Languages 5.7 Generation of Computers

99

99 99 100 100 101

'5. 7. I First Generation Computers [x

96 96 96 97 97 97 98 98 98 98

l

5.7.2 5.7.3 5.7.4 5.7.5

Second Generation Computers Third Generation Computers Fourth Generation Computers (1971-till date) Fifth Genaration Computers

5.8 Computer Generation-at a Glance 5.9 Types of Computers

5.9.1 5.9.2 5.9.3 5.9.4 5.9.5 5.9.6 5.9.7 5.9.8 5.9.9

Digital Computers Analog Computers Hybrid Computers Comparison between Analog and Digital Computers Mainframe Computers Minicomputers Microcomputers Personal Computers Portable Computers

5.10 Functions of Digital Computers Exercises

6. Input-output Devices and Storage Devices 6.1 Basic Concept of 1/0 Devices 6.2 What is Input Device? 6.2. l 6.2.2 6.2.3 6.2.4 6.2.5 6.2.6 6.2.7 6.2.8 6.2.9 6.2.10 6.2.11

Punched Card Keyboard Mouse Joystick Trackball Light Pen Touch Screen Magnetic Ink Character Recognition (MICR) Optical Character Recognition (OCR) Optical Mark Recognition (OMR) Point of Scale Devices

6.3 Output Concepts 6.3.1 Hard Copy 6.3.2 Soft Copy 6.3.3 Hard Copy Devices 6.3.3.1 Printer 6.3.3.1.1 Impact Printer 6.3.3.l.2 Non-Impact Printer 6.3.3. l .3 Comparison between Impact Printer and Non-Impact Printer 6.3.3.2 Plotter 6.3.4 Soft Copy Devices 6.3.4.f Visual Display Unit (VDU) or Monitor 6.3.4.2 Spooling (Simultaneous Peripheral Operation Online Processing) [xi]

101 101 102 103 103 104 104 104 104 105 105 106 106 106 106 106 107-108

109-122 111 111 111 111 112 113 113 113 113 113 113 114 114 114 114 114 114 114 115 115 116 116 116 116 116

116 117 117

6.3.4.3 Microphones

6.4 Storage Device 6.5 Types of Main Memory 6.5.1 6.5.2 6.5.3 6.5.4 6.5.5 6.5.6 6.5.7 6.5.8

Magnetic Core Memory Semiconductor Memory Random Access Memory (RAM) Read-Only Memory (ROM) Bubble Memory Cache Memory Comprarison between Core and Semiconductor Memories Comparison between Primary and Secondary Memories

6.6 Various Memory Devices 6.6.1 6.6.2 6.6.3 6.6.4 6.6.5

119 120 120 121 122 122

Magnetic Tape Magnetic Disk Hard Disc Floppy Disk (diskette) Optical Disk

Exercises

7. Operating System-DOS and WINDOWS 7.0 7.1 7.2 7.3 7.4

Introduction Definition of Operating System Types of Operating System Programs Some Microcomputer Operating System Features of Operating System 7.4. l 7 .4.2 7.4.3 7.4.4

123-142 125 125 126 127 127 127 127 127 128 128

Processor or Management Memory Management Device Management Information Management

7.5 Types of Operating System 7.5.1 7.5.2 7.5.3 7.5.4 7.5.5 7.5.6 7.5.7

117 117 117 118 118 118 118 119 119

Batch Processing System Interactive System Multiprogramming Virtual Storage Time-Sharing Multiprocessing Multi-user Operating System

7.6 Functions of Operating System 7.7 Advantages of Operating System 7.8 Popular Operating System 7.8.1 MS-DOS 7.8.2 Essential Jobs performed by DOS 7 .8.2.1 Standard Typing Keys 7.8.2.2 Function Keys 7.8.2.3 DOS Commands [xii]

128 128 128 129 129 129 130 130 131 131 131 131 132 132 133

7.8.2.4 DOS Program Summary 7.8.3 Windows 7.8.4 Important Features of Windows 95 and 98 Versions 7.8.4.l 7.8.4.2 7.8.4.3 7 .8.4.4 7.8.4.5 7 .8.4.6 7.8.4.7 7.8.4.8 7.8.4.9 7.8.4.10 7.8.4.11 7.8.4.12 7.8.4.13

My Computer Network Neighbourhood Recycle Bin To retrieve )deleted files Start Menu and Task Bar Start Menu Options Windows Explorer File and Folder Management To copy a file to a floppy disk Using drag and drop to copy move files or folder To rename a file or folder To delete a file or folder To create a new folder

Exercises

Introduction Data Transmission Factors to be considered Two Form of Data Transmission 8.3.1 Analog Data Transmission 8.3.2 Digital Data Transmission

8.4 Data Transmission Techniques 8.4.1 Acoustic Coupler 8.4.2 Modem 8.4.3 Multiplexor

8.5 Methods of Data Transmission 8.5.1 Asynchronous Transmission 8.5.2 Synchronous Transmission 8.5.3 Isochronous Transmission

8.6 8.7 8.8 8.9

137 138 138 138 138 138 140 140 141 141 142 142 142 142

143-164

8. Computer and Networks 8.0 8.1 8.2 8.3

133 136 136

Advantages of Data Transmission I Communication Goal of Network Network Architecture Types of Computer Network 8.9. l Local Area Network (LAN) 8.9.2 Metropolitan Area Network (MAN) 8.9.3 Wide Area Network (WAN)

8.10 Comparison of LAN and WAN 8.11 Various Network Topologies

145 145 145 146 146 146 146 147 147 148 148 148 149 149 149 149 149 150 150 151 151 152 152 152 153

8.11.1 Bus Network 8.11.2 Ring Network [xiii]

8.11.3 Star Network 8.11.4 Tree Network 8.11.5 Mesh Network

8.12 Communication Media/Channel 8.13 Data Transmission Modes 8.14 Network Concepts 8.14.1 Network Services 8.14.2 Transmission Media 8.14.3 Protocols

8.15 Network Softwares 8.15.1 File Services 8.15.2 Print Services 8.15.3 Message Services 8.15.3.1 Electronic Mail 8.15.3.2 Object Oriented Application 8.15.4 Database Services

8.16 Client Server Concepts 8.16. 1 Important Features 8.16.2 Merits of Client Server Concpets 8.16.3 Demerits of Client Server Concepts

Exercises

9. Word Processing 9.1 9.2 9.3 9.4 9.5

161 161 162 162 162 162 163 163 163 164 164

165-182

Meaning and Role of Word Processing Advantages of Using Word Processing Important Features of a Word Processing Software Microsoft Word (MS-Word) Practical Aspect for Using MS-Word 9.5.l 9.5.2 9.5.3 9.5.4 9.5.5 9.5.6 9.5.7 9.5.8 9.5.9 9.5.10 9.5.11 9 .5 .12 9.5.13 9.5.14 9.5.15 9.5.16 9.5.17

155 156 157 158 159 160 160 161 161 161

Creating a New Document Saving the File Formatting the Text Alignment of Text Applying Fonts Spellcheck Consulting Thesaurus Creating a Character Style Closing the File Open a File Editing Tools Auto-Correct Steps for adding auto-correct entries without formatting Steps for adding new auto-correct entries with formatting Auto-formatting text Find and Replace Page Numbering [xiv]

167 167 168 168 169 169 171 172

173 173 174 174 175 175 175 176 176 177 177 177 178

179

9.5.18 9.5.19 9.5.20 9.5.21

Header and Footer Create a Table of Contents Macro Application File, Insert

Exercises

10. Electronic Spreadsheet

183-204

10.1 Meaning and Role of Electronic Spreadsheet 10.2 Functions Available in Electronic Spreadsheet 10.3 Advantages of Using an Electronic Spreadsheet 10.4 MS-Excel 10.5 Applications of MS-Excel Package 10.5.l 10.5.2 10.5.3 10.5.4 10.5.5 10.5.6 10.5.7 10.5.8 10.5.9 10.5.10 10.5.11 10.5.12 10.5.13 10.5.14 10.5.15 10.5.16 10.5.17 10.5.18 10.5.19 10.5.20 10.5.21

Working with MS-Excel Copying the Formula Adjustment of Decimals Applications of Formulas Auditing a Workbook Comments Inserting Formulas that make Decisions Application of IF Functions Headers and Footers Merging Workbooks Protection of a Worksheet To Share a Worksheet Working with more than one Worksheet Copying Entries Between Workbooks Moving Sheets between Worksheets Deleting Sheets Creation of Graphs/Charts To modify Charts Creation of a Pivot Table Report Selection of another Chart Printing your Worksheet

Exercises

11. Database Management Systems (DBMS) 11.1 Concept of Database Management System 11.2 Characteristics of Database Approach 11.3 Important Components of Database Management Systems 11.3. l 11.3.2 11.3.3 11.3.4 11.3.5

180 181 181 182 182

Data Processing Manager Application Programmer Database Designer Database Administrator Tool Developer [xv]

185 186 186 186 188 188 190 192 192 195 195 195 195 197 198 198 198 199 199 199 199 200 200 202 202

203 204 205-224

207 208 208 208 209 209 209 209

11.3.6 11.3.7 11.3.8 11.3.9

11.4 11.5 11.6 11. 7 11.8 11.9 11.10 11.11 11.12 11.13 i 1.14 11.15 11.16

Operators and Maintenance Personnel Data Dictionary Data Independence End Users

Basic Principles of Database Management System Functions of Database Management System Important Role of DBMS DBMS : Logical Data Structunng Techniques Three-Schema Architecture of DBMS Database Management System Language Advantages and Limitations of using DBMS The Relational Data Model Fundamentals of Relational Database Management System (RDMS) The Relational Algebra Properties of Relational Database Structure of Relational Database Management System File Access Methods 11.16.. 1 Sequential Access File 11.16.2 Direct or Random Access File 11.16.3 Indexed Sequential Access File

11.17 Comparison between Sequential and Indexed Sequential Files Exercises

12. Electronic Data Interchange (EDI) 12.0 12.l 12.2 12.3 12.4 12.5

209 210 210 210 210 210 212 212 214 215 216 217 217 218 221 221 221 221 222 223 223 224

225-236

Introduction Concept of EDI EDI over Traditional Methods Installation of EDI : Most Important Issues Functional Environment of EDI Basics/Components of EDI System

227 227 228 229 229 231

12.5.1 EDI Standards 12.5.2 EDI Software 12.5.3 Third Party Network for Communications

231 231 232 233 233 234 235 235 236 236 236

12.6 Financial EDI-a Concept 12.7 FEDI for International Trade Transactions 12.8 ~iagramn;iatic Representation of FEDI 12.9 Applications of EDI 12.10 Benefits of EDI 12.11 Future of. EDI 12.12 Limitation of using EDI Exercises

[xvi]

13. The Internet and Its Basic Concepts 13.0 13.1 13.2 13.3

Introduction Definition and Concept. Brief History of Internet Technological Foundations of Internet 13.3.1 Internet Protocols 13.3.1.1 Transmission Control Protocol/Internet Protocol (TCP/IP) 13.3.1.2 Data Linked Layer Protocol (DLLP) 13.3.1.3 Internet Control Message Protocol (ICMP) 13.3.1.4 Hyper Text Transfer Protocol (HTTP) 13.3.1.5 File Transfer Protocol (FTP) 13.3.1.6 TELNET 13.3.2 Network Devices 13.3.3 Domain Naming Systems (DNS)

13.4 IP Address 13.4.1 Characteristics of the IP Address

13.5 Client/Server Computing 13.6 Working Tools of the Internet 13.7 World Wide Web-Its Evolution 13.7.1 Basic Components for Using WWW

13.8 Concept of Chatting & Internet Relay Chat (IRC) 13.9 Intranet 13.9.l Purpose of the Intranet 13.9.2 Advantages of the Intranet

13.10 13.11 13.12 13.13

Impact of Internet on the Society Various Applications of Internet Some Negative Aspects of Internet Internet Security 13.13. l Commmon Threats for Internet Security 13.13.2 How to avoid Virus?

Exercises

239 239 240 241 241 241 241 242 242 242 243 243 244 244 245 245 245 247 247 248 249 249 249 249 250 251 251 251 252

252

14. Information System Audit 14.0 14.1 14.2 14.3 14.4

237-252

253-268

Introduction Basic Idea of Information System Audit Definition Nature, Significance and Scope of System Audit Steps Involved in Conducting System Audit

255 255 256 256 256

14.4.1 14.4.2 14.4.3 14.4.4

257 258 258 260

Management Controls Operational Controls Organisational Controls Environmental Controls

14.5 Difference of Traditional Concepts of Audit with System Audit

260 260

14.5.l Traditional Audit [ xvii]

14.5.2 Object of a Traditional Concept of Audit 14.5.3 Types of Traditional Audit

14.6 Comparison between Traditional Audit and System Audit 14.7 Foundations of Information System Auditing 14.7.l 14.7.2 14.7.3 14.7.4

Information System Audit Plan Audit Techniques Documentation Testing

14.8 Audit Charter 14.9 Audit Methodology in a Computerised Environment 14.9.1 Audit around the Computer-the Black Box Approach 14.9.2 Audit through the Computer-the' White Box Approach

14.10 Advantages of Information System Audit 14.11 Information System Audit and Control Association (ISACA) 14.12 Practical Guidelines to Conduct Audit of Computerised Accounting System

14.13 Audit. Trial 14.14 Information System Audit in Internet Environment Exercises Appendix A : E-Commerce and Flow t::'.harts Appendix B : Short Questions Appendix C : Abbreviations Calcutta University Question Papers

[xviii]

261 261 262 263 263 263 263 264 264 265 265 265 266 266 266 267 267 268 269-274 275-282 283-290

1-

PREFACE Information Technology has revolutionised the process of education and development of a modern man. Educational and professional institutes have, accordingly, reorganised their curricula keeping pace with this changing scenario. Under the circumstances, this book has attained enormous significance. The text, covering the syllabi of all major Indian universities, has been written in a lucid language with logical sequence to help the students grasp the topics with confidence. We express our indebtedness to the renowned authors who have extended their generuus help in preparing the framework of the text. We are grateful to Dr. Shib Shankar Sana of the Department of Mathematics, Bhangar Mahavidyalaya, for his active support and cooperation. Our heartfelt thanks are due to Mr Amitabha Sen, Director, New Central Book Agency (P) Ltd, without whose inspiration this book would have never seen the light of the day. The preparation of the text has witnessed, what is called silent sacrifice, by our wives Mrs Rekha Rani Jana, Mrs Soma Samanta, and children Neha, Moumita, and Madhumita. We are looking forward to rece1vmg positive criticisms, comments and suggestions from the teachers and students alike, which would help us improve the quality of the text in the subsequent editions.

l\1adan l\1ohan Jana Nabin Kumar Samanta

Independence Day 15 August 2007 Kolkata

[xix]

"This page is Intentionally Left Blank"

ACKNOWLEDGEMENTS CA Dr. Prof.

CA Dr. Prof. Dr. Prof. Dr. Prof. Dr. Prof.

Anutam Paul Mrinal Chakraborty Debashis Poddar Ashim Manna Subir Chakraborty Abir Hossain Tarun Patra Manas Kr. Adhikary-Principal Amit Basak Pumendu Bikash Chatterjee Anil Ray Rabindranath Thander Rupa Chatterjee Durga Ray Subrata Goswami Umasankar Saha Mukti Ram Mitra Puma Chandra Maity Rajib Bose Suvendu Saha Dilip Barik Sandip Paul

Biswarup Kar CA Subhayan Basu Prof. Amal Krishna Roy Jayanta Ghosh Bhaskar Purakayasta Ramprasad Roy Sahidul Islam Sri Kumar Mitra Amitava Chakrabarty Pintu Sarkar Sanjeeb Kr. Pakhira Manisha Chowdhury Prasanta Guha Anupam Sengupta Siddhartha Chakraborty Mrinal Kanti Dutta Sreyasi Banerjee

Dinabandhu Andrews College

Dinabandhu Institution Susi! Kar College

Bhangar Mahavidyalaya Surendra Nath College

Mrinalini Dutta Mahavidyapith Sree Chaitanya Mahavidyalaya Lalbaba College City College of Commerce and Business Administration Ananda Mohan College Heramba Chandra College

Dinabandhu Mahavidyalaya Basirhat College · Dinabandhu Institution Manindra Chandra College Vijoygarh Jotish Ray College K. K. Das College Barasat College P. N. Das College S. A. Jaipuria College [ xxi]

Prof. Ipsita Goswami Arunima Rudra Arup Banki Parichita Basu Anupam Mitra Srabani Dey Madhab Ch. Samanta Arindam Mukherjee Basaba Dutta Paul Anindita Bhattachariya Madhu Agarwal Saradaprasad Dutta Soma Bhattachariya Subashis Banerjee Swapan Kr. Maity Madhumita Sengupta Partha Sarathi Dutta Avishek Das Sumana Chakraborty S. S. Mukherjee Amit Kr. Das Anupam Karmakar Avijit Santra Kingshuk Chaudhuri Krisnendu Ghosh Shambhunath Saha Sudipta Acharjee Samiran Sengupta Sri Adyita Jana, AICWA Prof. N. Biswas P. P. Pal Ram Prahlad Cho\¥dhury Soumitra Das Sri Sri Prakash Mondal Prof. Ranjit Kumar Paria Swadesh Kr. Monda! (Sm.) Sikha Banerjee Arunabha Sinha Dr. Pranab Sarkar Prof. Narayan Ghosh Ananta Lal Biswas Debashish Chakraborty

S. A. Jaipuria College

Raja Peary Mohan College Dr. Kanailal Bhattachariya College Acharya Girish Ch. Bose College Naba Ballygange Mahavidyalaya Umesh Ch. College S.S. M. Jalan Girls' College G. M. S. M. Mahavidyalaya Charuchandra College New Barrackpur Prafulla Chandra College Shibnath Sastri College P. C. Mohalanabis Mahavidyalaya Mrinalini Dutta Mahavidyapith Rabin Mukherjee College Vidyanag B, or A < B, or A = B, etc.). (c) Arithmetical assessment of data (For example, C and D are two data. In such cases, arithmetical assessment may be addition, subtraction, multiplication or division ; e.g., C + D, or C - D, or C x D, or C + D, etc.) (d) Entity-wise collection of data. (For example, Sundry creditor is an entity code for purchases system) (e) Record-key oriented Data Collection. (For example, cheque no. may be identified by Record-key in a bank's transaction).

2.2 Data Processing Data Processing is the manipulating, restructuring or recovering of data by people or machines to increase their usefulness and value for some particular purpose. Data processing activities are primarily dependent on three basic stages as follows. (i) Input (Raw Data) (ii) Processing (Manually /Electronically) (iii) Output (Information) Input (Raw Data)

____.

Processing [Manually/Electronically] f----+

Output (Information)

16

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

1. Input (Raw Data) : Input is the raw data duly collected for processing. Just as raw materials are transferred into finished goods through manufacturing (either mannual or machine-based) process, raw data are converted into information by processing functions. 2. Processing (Mannually/Electronically) : Data Processing covers all activities required for generating information from data. The data can be processed, organised and accessed. Thus processing is the manipulation of letters, numbers, symbols or graphics that constitute data. Processing steps are as follows : (i) Classification : Segregation of homogeneons and heterogeneous data in a group or division. (ii) Calculation : Addition, subtraction, multiplication and division, etc. (iii) Sorting : The sequence or flow of steps to be followed to get the desired result. (iv) Summarising: Similar group of data must be reduced to a meaningful and concise form. 3. Output (Information) : It is the next and final stage after data processing activities. In this stage results in the form of Information can be had after performing the following steps : (i) Reporting : It is the formal presentation and distribution of output. (ii) Documenting : It involves notification, recording, drafting and conveyancing. (iii) Retrieving·: It is a recovery process of information in a computer to .deliver another standpoint or to take further decision. (iv) Analysing : It involves reviewing and recommendation of information. 2.2.1 Data Processing Cycle These three s.tages of data processing shown in a chronological order are called data processing cycle which is shown in a flow-chart as follows Organisation of Data (Data originated on Source documents time-cards, sales orders, Purchase orders invoices, etc.) Input of Data (Date recorded in suitable medium for data processing system.) Processing of Data (Data entered into system and processed, stored, calculated, compared, analysed, etc.) Output information (Summaries, reports and documents prepared either as printed matter or type-writter form) Storage of Data/Information (Filing cabinet, microfilm, floppy-disk, C-disk, magnetic tapes, etc)

FUNDAMENTALS OF COMPUTERS

17

2.2.2 Data Processing operation The fundamental operations of a data processing activity may be printed out in order of sequence as follows : (i) Classification : The classification of data involves the identification of data on the basis of one or more facts/figures. (ii) Sorting : After the data is classified, it is usually necessary to. arrange or rearrange the data into some logical order to facilitate processing. (iii) Verification : It involves scrutiny, checking of accuracy of data for processing. (iv) Scanning : It involves searching of purposeful facts and unidirected viewing. (v) Comparison : It involves simultaneous examination of two or more items of data for their subsequent action. (vi) Calculation : It involves arithmetical manipulation of numerical data to create meaningful results, e.g., addition, subtraction, multiplication and division, etc. (vii) Recording : It involves intermediate results which may be recorded until their further proceesing. (viii) Summarisation : It involves similar group of data to be reduced to a meaningful and concise form. (ix) Filtration : It involves screening out of extraneous data for its final processing.

2.3 Methods of Data Processing Basically there are three methods of data processing. These are 1. Manual System. 2. Eletromechanical System 3. Electronic Data Processing System (EDP) Electronic data processing system has also innovated three enlarged, modified and logical systems of Data Processing. These are : (a) Computerised Management Information System (CMIS). (b) Decision Support System (DSS). (c) Expert System (ES).

2.3.1 Manual Data Processing System In manual system, all data processing is done by men. A man receives data from anywhere to store in the brain which also acts as a control and logic unit and then mind preforms many operations on data for valuable information in the form of reports, books, records, statements, etc. Advantages : Important advantages of Manual Data Processing System are : (i) It involves whole centralised processing. (ii) It provides information either verbally or in writing. (iii) It may create an innovation in the form of information. (iv) It does· not depend on machine, power supply or suitable environment. Disadvantages : The main disadvantages of a manual system are : (i) It is very slow. (ii) It may provide inaccurate information. (iii) Human brain has Iimitted storage capacity.

2.3.2 Electromechanical System In this system data are processed electromechanically or by unit record machines. Theses equipments process data through punch cards, on which data are coded by making punched holes. Among the electromechanical machines, Punch card, Keypunching Machine, Verifier, Sorter Machine, Collator, Calculator, etc, are the main devices. l.T. App. in Business-2

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

18

Advantages : Important advantages of Electromechanical System are (i) This system is less expensive. (ii) This system has effective controlling. (iii) This system maintains accuracy in data processing. (iv) This system may provide prompt data processing activities. Disadvantages : The main disadvantages of Electromechanical System are : (i) This system is relatively slow. (ii) This system requires manual intervention at different stages of data processing. (iii) This system finds difficulties to handle large volume of data. 2.3.3 Electronic Data Processing System Electronic data processing involves the use of computers. It has the capability of maintaining speed, accuracy and storing large amount of data for their processing activities. It is commonly known as EDP System. The function from Electronic Data Processing System may be presented in a flow-chart as follows : Processing ~

I

Input j (Data) 1

,. (a) Terminal Keyboard (b) Card Reader (c) MICR (d) OCR etc.

Permanent Store Central Processor (Arithmetic & Logic + Control) Temporary Storage (Main Memory)

Output •I (Information) ~I

I

I

i

(a) Terminal Display (b) Printer

,. (a) Cards (b) Tape (c) Disk etc.

I

(a) Magnetic Core (b) Semiconductor Memory

Electronic Data Processing System

Advantages : The main advantages of electronic data processing system are : (i) Speed & Accuracy : This systems has unimaginable speed and accuracy in data processing activities. (ii) Lower Cost : This system offers better method of data processing at a minimum cost. (iii) Versatility : This system ensures that data processing results can be recorded on one of the several media for input. (iv) Decision Making Capability : This system has an additional capability of choosing alternative course of action. (v) Timeliness : This system reduces delays in data processing. (vi) Super Human Memory : This system may store tremendous volume of data and a large set of instructions for data processing. Disadvantages : The main disadvantages of this system are : (i) This system cannot process all types of data due to the non-availability of suitable software.

FUNDAMENTALS OF COMPUTERS

19

(ii) Change options in the final inputs during electronic data processing cannot be brought about. (iii) This system mainly depends on power supply. (iv) This system is governed by the principles of electronics for processing data. Thus system error cannot be easily detected. 2.3.4 Computerised Management Information System (CMIS) The Computerised Management Information System refers to the formal system installed in an organisation for the purpose of collecting, organising, storing and processing data and presenting useful information to the management at various levels. Thus it is a system of men, machine, procedures, documents and communications that collects, validates, operates, stores, retrieves and presents data for use in planning, budgeting, accounting, controlling and other management process. Advantages : The most important advantages of CMIS are as follows : (i) Accuracy : Being highly computerised, CMIS gives accurate information regarding various data processing activities. (ii) Efficiency : This system is much important in increasing the efficiency of data processing function. (iii) Updated Results : This system helps the management in getting the updated results by processing data of various departments. (iv) Management Oriented : This system is always management oriented and keeps in view that every level of management gets the desired information through data processing. (v) Common Data Flows : This system ensures the use of common Input processing and Output procedures and media whenever desirable. (vi) Economy : This system is cost-effective. (vii) Reliability : This system ensures through checking and testing of each stage of data processing activities and thereby helps the management with reliable decision making. (viii) Feasibility : This system is able to adopt any dynamic changes at energy level of managerial data processing activities. Disadvantages : The main disadvantages of CMIS are as follows : (i) CMIS is not a substitute for effective management. (ii) CMIS cannot provide tailor-made information packages suitable for every type of decision-making. (iii) This system is inherently frangible, highly sensitive and requires continuous updating. 2.3.5 Decision Support System (DSS) It is a system which is primarily used with unstructured or semi-structured data processing to help and resolve uncertainties in the decision-making process of various levels of management. Thus DSS is a programme designed to aid the decision-making function of the management. An important component of DSS is simulation, that is to say, construction of mathematical/statistical models for evaluating the behaviour of real persons, processes or system when particular projects or strategies are adopted.

Advantages : The advantages of DSS are as follows : (i) It involves processing of transactions, keeping records and providing reports on routine activities of the business.

20

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

(ii) This system ensures the higher and middle level management to deal with the strategic and technical decision of a business. (iii) This system enhances the managerial capabilities in the area of predicting the outcome of the course of action or its alternatives. Disadvantages : The main disadvantages of this system are : (i) It is not a simple but a complex system. (ii) It is not helpful to low level management. (iii) Budgeting by DSS is extremely difficult. 2.3.6 Expert System (ES) An expert system is actually a software package developed to capture deep knowledge and long experience of human experts about a particular subject. Most of the earlier expert systems were designed to run on larger computers and there are projections for developing expert systems for the fifth generation super-computers. PC (Personal Computers) based expert systems are also becoming popular these days. For example, a PC based expert system called Alacrity, has some 3000 rules to provide expert advice on binomial analysis and projections on credit rating. These fields of computer applications have minic-traits of human intelligence and hence could be appropriately termed as computerised intelligence. It is also known as Artificial Intelligence (AI). Advantages : This system has the following merits : (i) This system has led to the development of knowledge-based systems. (ii) This system exploits human intelligence and gets itself Artificial Intelligence. (iii) This system intensively interrogates human experts to research in a particular field like medicine, law, finance, taxation etc. Disadvantages : The main disadvantages are stated below : (i) This system basically depends on human intelligence. (ii) This systems does not provide permanently -programmable software, because in such field, upgradation of the existing software is vigorously done through constant research.

2.4 Information Information refers to an output of data processing which is organised and meaningful to the person who receives it. For example, data concerning sale may indicate the names of the salesmen when a large number of such data elements is organised and analysed and it may provide important information to a marketing director who is attempting to evaluate his sales force. 2.4.1 Concept of information Basically Information can be prepared m three different stages (a) Collection of data. (b) Processing of data. (c) Preparation of information. These information can be prepared in the form of reports, statements, graphs and charts. Information is usually supplied through the following media (i) Information can be supplied through written statement. (ii) Information can be supplied through graphs and charts. (iii) Information can be supplied orally.

FUNDAMENTALS OF COMPUTERS

21

Generally information is communicated among the different levels of management of business. When information is communicated from lower level to upper level of management, it is called upward flow. Decision is taken on the basis of upward flow of information. When decision is communicated from the upper level of management to the lower level, it is called downward flow of information. Communication of information between persons of the same level is called horizontal level of information. 2.4.2 Need of information Information is essential for the development of mankind. Nowadays human beings are keen to obtain various information for their self-awareness and self-improvement through any media of information like daily newspapers, radio, T.V. and internet connection. In wider sense, information are basically required for decision-making purpose. Such decisions are often taken by the managers for the overall growth and development of a business enterprise. 2.4.3 Factors on which Requirements of Information Depend The need of information of different level executives depends on the following factors: (i) Operational Function. (ii) Level of Management Activities. (iii) Type of Decision Making. (i) Requirements of Information depend upon operational Function : The requirements of information of different operational functions vary not only in content but in characteristics as well. In fact, the content of information depends upon the activities performed under an operational function. For example, in the field of production the information required may include the production targets to be achieved, resources available and so on, when as in case of marketing the content of information may include the consumer behaviour, impact of new product in the market, etc. The characteristics which must be posses,, d by a particular information are influenced by an operational function. For example. the information required by accounts department for preparing pay-roll of the employees should be highly accurate. (ii) Requirement of information depends upon the level of activities : The level of management activities also influences the information requirement and its characteristics. For example, strategic planning requires more of external information. The information tends to more of qualitative and general in nature in many instances. Management control requires more accurate, precise, current and repetitive information. (iii) Requirement of information depends upon the type of decision-making : Organisational decision can be categorised as programmed and non-programmed decision.

Programmed decisions : Decisions which are of repetitive and routine nature, are known as programmed decisions. For example, preparation of pay-roll and disbursement of salary and wages through bank account. For taking such decisions, guidelines and rules required are provided in the form of a procedure manual.

22

!NfORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Non-programmed decisions : Decisions which are unstructured, complex, involve high consequence, or major commitment, are known as non-programmed decisions. For example, new product line, capital budgeting. Non-programmed decision-making is not pre-established decision procedure. It is also difficult to completely specify the requirements of information for taking these decisions. 2.4.4 Features of the Good Quality Information A good quality Information has the following important characteristics : (i) Brevity : The information must be concise and it should not be unnecessarily descriptive. (ii) Meaningful : The information must be meaningful and accurate at the time it is transmitted to a person or machine, otherwise it is simple data. (iii) Mode and format : The modes for communicating information to a person must be sensitive and in case of business organisation, they are either visr J or in written form. (iv) Redundancy : _It means the excess of information carried per unit of data. For example, 75% of letters used in a phrase are usually redundant. However, in business situations, redundancy may sometime be necessary to safeguard against errors in the communication process. . (v) Timeliness : The information should be available in proper time to understand a particular situation. (vi) Completeness : The information should be complete as far as possible. (vii) Action oriented : The information should be action oriented so that immediate action may be taken on such information. (viii) Reliability : The information must be reliable so that internal management of any organisation must have certain degree of confidence and they can take any vital decision on the basis of that information. (ix) Cost benefit analysis : The benefits that are derived from the information must justify the cost incurred for obtaining such information. (x) Conformity with previous knowledge : The information must confirm to previous knowledge so that it should not contradict with any well-known existing knowledge. (xi) Validity : It measures the closeness of the information to the purpose which it intends to serve.

2.4.5 Levels of Information Information can be categorised into different levels considering its importance and demand to various receipients. It may be data lo one receipient and the same after processing may be the information to another. For example, a person is awarded a Ph. D. degree from a state university-it is called Individual Information. Now suppose, University Grant Commission (UGC) require a list of Ph. D. degree holders from all universities affiliated to it. Then it is a data to all the state universities. After compiling and processi~g these data, UGC can produce a list comprising National Level of Information. In a similar way, it can be produced based on the data available internationally. Then it is called International Level of Information. Thus different levels of information may be named and discussed as follows : 1. International Information : The information which has got a significance, value and reputation at international level is called International Informations. Many

FUNDAMENTALS OF COMPUTERS

23

international agencies and institutions continuously produce through their magazines, bulletins, etc. valuable news for the utilisation of different purposes like population statistics, natural resources, invention of medicines, currency exchange rules, academic and professional news, and so on.

2. National Information : The information which has got a significance, value and reputation at nationa.1 level is called National Information. Gross domestic productions, net domestic productions, share market information, national B.O.P., domestic inflation rate, national sports news, etc. are the examples of National Information. 3. Corporate Information : The information which has got significance and value at corporate level is known as corporate information. Amalgamation, merger, reconstruction of corporate bodies, financial positions, profit margin, gross NPA of all Banks are the examples of Corporate Information. Corporate Information can be analysed into 3 Levels : (a) Strategic Information : The information which is used by top management to plan the objectives of their organisations and to assess whether the objectives are being met in practice is called strategic information. Such information include ove~all profitability, the profitability at each productivity level, future market prospects, need of fixed working capital, etc. (b) Tactical Information : The information which is used by middle level management to ensure that the resources of the business are employed effectively and efficiently to achieve strategic objections of the organisation called Tactical Information. Such information includes, productivity ratio, budgetory control, variance analysis, cash-flow forecast, etc. (c) Operational Information : The information which is used by front-linemanagers, e.g., foremen, heads-clerks, etc., to ensure that specific tasks are planned and carried out properly within a factory or office, etc. are called Operational Information. Such information includes Labour worked daily/weekly, rate per hour, idle time/capacity, overtime wages, or other incentives, etc.

4. Departmental Information : The information which is particularly related to a department, e.g., production department, personnel department, sales department etc., is called Departmental Information. Segregation of departmental heads, gross purchases and sales of a department, profit/loss of a departmental unit, etc. are the examples of Departmental Information. 5. Individual Information : The information which is generally related to an individual is called Individual Information. Bio-data of an individual, cost to company (CTC), performance appraisal, tax liability, pay package, etc. are the examples of Individual Information. 2.4.6 Value of Information It is defined as the value of the change in decision behaviour caused by the information less the cost of information. In other words, given a set of possible decisions, a decision-maker may select one on the basis of information at hand. If new information causes a different decision to be made, the value of the new information is the difference in value between the outcome of the old decision and that of the new decision, less the cost of obtaining the information.

24

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

2.4. 7 Difference between Data and Information The main differences between data and information may be pointed out in a tabular form :

Data

Information

1. Data is a collection of facts, figures, statistics or statements connected m the subject matter. 2. Data are Raw Materials for producing information. 3. Data is the cause. 4. Data may be singular or plural. 5. It does not help in decision-making. 6. It 1s not able to provide any correct meaning before processing. 7. A set of words may be treated as data. 8. It is fixed until processed.

1. Information is the organised, analysed or classified data.

2. Information are final product from data. 3. Information is the effect. 4. Information is always in plural form. 5. Decisions can be taken on the basis of information. 6. It provides a correct meaning. 7. A sentence may be considered as information. 8. It is semi-variable or variable.

EXERCISES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

11. 12. 13. 14. 15. 16. 17. 18.

Define data. What are the basic elements of data? Discuss the pre-requisites for the need of data. Discuss, in brief, the concept of data. What is data processing? Discuss the basic stages for data processing. Point out the various data procesing operations. Name the different types of data processing. What is electronic data processing? Discuss the advantages and disadvantages of electronic data processing. What is MIS? Discuss the advantages and disadvantages of Management Information System (MIS). What is Decision Support System (DSS)? Discuss its advantages and disadvantages. What is Expert System? What is Artificial Intelligence (Al)? Discuss the advangages and disadvantages of Expert System. What is information? Discuss the concept of information. What are the factors on which information requirements depend? Discuss the salient features of a good quality information. Discuss, in brief, the various levels of information. Distinguish between Data and Information. What is the value of information?

Chapter

Numbering Systems and Digital Codes Contents Introduction 3.0 3.1 Concept of Number System 3.2 m• Decimal Number System 3.3 Binary Number System 3.3.1 Reasons for using Binary Number System 3.3.2 Conversion of Decimal Number into Binary Number 3.4 Octal Number Systems 3.4.1 Conversion of Octal Numbers to Decimal Numbers 3.4.2 Conversion of Decimal Numbers to Octal Equivalence Hexadecimal Number System 3.5 Conversion from one System to another System 3.6 Octal-Binary Conversion 3.6.1 3.6.2 111• Binary-Octal Conversion 3.6.3 11• Octal-Hexadecimal Conversion and vice versa Hexadecimal-Binary Conversion and vice versa 3.6.4 3.7 Data Representation 3.7.1 Data types 3.7.2 Fixed Point Data Representation 3.7.3 Floating Point Data Representation Digital Coding 3.8 3.8.1 Major requirements for a Coding System 3.8.2 Features of a good Coding System 3.9 , Binary Coded Decimal (BCD) Extended Binary Coded Decimal Interchange Code (EBCDIC) 3.10 3.11 American Standard Code for Information Interchange (ASCII) Gray Code 3.12 3.12.1 Typical Application of Gray Code 3.12.2 Advantages of Gray Code II. . II. .

,. ,. II. .

II. .

II. .

II. .

II. .

II. . II. .

II. . II. .

II. . II. .

II. .

II. .

II. .

..

II. .

II. .

II. . II. .

II. . II. .

•

Exercises

25

3

"This page is Intentionally Left Blank"

...

Chapter

3

Number Systems and Digital Codes 3.0 Introduction The computers can handle data by different electrical components, e.g. transistors, semiconductors, integrated circuits (IC), wires or cables, etc. Thus a computer can understand only one language-the binary language-known as the language of a computer. This language consists of two symbols, e.g., 0 and 1. However, the most common way to represent data is the use of numerals, e.g., 0 to 9 and alphabet, e.g., A to Z along with some symbols, e.g., +, -,/, x, etc. In such complexity, the computer can understand the human languages (data) by changing them into binary form, known as coding of data. The responsibility of coding and decoding data in a computer system lies with the input-output device. The data which are essentially stored in computer memory can be of two types : (i) Numeric, (ii) Non-numeric. Numeric· data mean numbers used in· arithmetic operations, such as addition multiplication, subtraction and division. On the contrary, non-numeric data means the letters (A to Z) and discrete symbols (+,-,/,x, % ) used for specific purposes. Thus, whatever may be the form of data, it can be represented in binary-coded form.

3.1 Concepts of Number System A number systems of base or radix 'r' is a system that uses distinct symbols for 'r' digits. Numbers are represented by a string of digit symbols. To determine the quantity that the number represents, it is necessary to multiply each digit by an integer power of 'r' and then form the Sum of all weighted digits. It is very essential to be much knowledgeable about the number systems for the design and architechture of a computer system. Basically there are four Number Systems as follows : 1. Decimal Number System. 2. Binary Number System. 3. Octal Number System. 4. Hexa Decimal Number System. 27

28

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

3.2 Decimal Number System The decimal Number System consists of 10 digits, namely 0 to 9. Each digit has also a positional value determined by the decimal point of the digit. Digit Value and Positional Value for each number system depend on the base of number system. We can arrange this for decimal number system as follows Power Base 106 105 104 103 102 101 100

Position 7th 6th 5th 4th 3rd 2nd 1st

Value 1000000 100000 10000 1000 100 10 1

In Integer as well as Real Numbers Power Base 103 102 101 100

Position 4th 3rd 2nd 1st

Decimal~

~

10-1

1st

10-2

2nd

10-3

3rd

10-4

4th

Value 1000 100 10 1 Part l 10 l 100

1000 1000

Thus the value of each digit in a number depends upon the following (i) The face value of the digit. (ii) The base of the system. (iii) The position of the digit in the number. Let us consider the number 8888. All the digits represent the same value of eight absolutely. However, the positional values are the absolute values multiplied by 10 raised to positional power as follows : 8888 = 8 x 1000 + 8 x 100 + 8 x 10 + 8 x 1 = 8 x 103 + 8 x 102 + 8 x 10 1 + 8 x 10° Since the positional increment is a power of 10, the value 10 is known as the base of the number system. Therefore, BASE of a number system is the value whose positional power is used to represent another value. Let us take the code 'b' for the base of a number system. Thus in the decimal system b = 10. The number of digits being used in the system is (10 -1). The largest absolute value· of the largest digit used in the system is 9 = 10 - l = b - 1. Thus the number 5621 will be represented in the decimal system as follows : 5 x 103 + 6 x 102 + 2 x 101 + 1 x 10° Using the codes, we can represent the above expression as 5 x b3 + 6 x b2 + 2 x b 1 + 1 x b0

NUMBERING SYSTEMS AND DIGITAL CODES

29

Thus in the decimal system, the positional value of each digit in a number starting from the right-most digit increases ten-fold as one moves from right to left. Again in case of a fractional number it can be represented as follows : (say) F = (digit) 1 x b- 1 + (digit) 2 x b- 2 + (digit)3 x b-3 + ........ . + (digit)" X b-n Thus the fraction number (say) 0·839 cal} be represented as follows 8x

__L

10

I +3x __L +9x 1000= 0·839

100

3.3 Binary Number System Binary numbers may play a very significant role in harmonisation, architecture and understanding of computers. In binary number system, the base is 2 instead of 10. This code is used only for computer mathematical application and not used to handle alphabetic data. Since the binary system only uses two symbols (1, 0), it is called a radix-twosysem. The largest single digit is 1 which is one less than the base 2. Each position in a binary number represents a power of base 2. Thus binary number 1 in the unit position represents 20. The decimal equivalent of binary number 111 is 1 x 22 .+ 1 x 2 1 + 1 x 2° = 7. [as per laws of indices, a0 = l] Thus the string of digits 101101 is interpreted to represent the quantity as follows : 1 x 25 + O x 24 + 1 x 23 + 1 x 22 + O x 2 1 + 1 x 2° = 45 [ ·: 2° = I]

3.3.1 Reasons for using Binary Number System The reasons for which computers use the binary numbers are as follows : (i) Computer circuits have the capability of handling only two binary digits (1,0) rather than 10. (ii) Electronic components, by their very nature, operate in a binary mode. For example, the operation of switch may be either on (1) or off (0). (iii) Using the two symbols ( 1, 0) that can be reduced cost and improved reliability. ILLUSTRATIVE EXAMPLES 1. Determine the decimal equivalent of the following binary number : = ( )10 (11011)2 Solution : ( 11011 )2 = 1 x 24 + 1 x 23 + O x 22 + 1 x 2 1 + 1 x 2° = 27 [ as per laws of indices, a 0 = 1 ; 2° = l] = (27)10 2. Convert the following number into decimal Number : (110101)2 = ( )10 Solution : (110101 )2 = 1 x 25 + 1 x 24 + O x 23 + 1 x 22 + O x 2 1 + I x 2° = 53 = (53)10 3. Convert the following number into decimal form : (11011011)2 = ( )10 Solution : (11011011) 2 = I x 27 + 1 + 26 + O x 2s + 1 x 24 + 1 x 23 + 0 x 22 + 1 x 2 1 + 1 x 2° = 219 = (219)10 4. Convert the fbllowing number into decimal form (101010110110h = ( )10

30

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Solution : (101010110110)z = 1x211+Ox210 + 1 x 29 + O + 2s + 1 x 21 + O x 26 + 1 x 2s + 1 x 24 + o x 23 + 1 x 22 + 1 x 21 + O x 20 = 2742 = (2742)10 5. Convert the following binary number into decimal form : (O· llOl)z =( ) 10 Solution : (O·llOl)z =l x 2-r + 1 x 2-2 + O x 2-3 + 1 x 2-4

= 1x-1-+1x-1-+ox-1-+1 x-121 22 23 24 = 1x.l+11-+ox.l+ 1 x_!_ 2 4 8 16 = 0·5 + 0·25 + 0 + 0·0625 = 0·8125 = (0·8125)10 6. Convert the following binary number into decimal form (O·OOllh =( )10 Solution : (O·OOll)z = O x 2-1 + 0 x 2-2 + 1 x 2-3 + 1 x 2- 4 Ox-1-+ox-1- + 1x-1-+1 x-121 22 23 24 [as per Laws of Indices, a-n

=

_l_ ]

a" 1 1 =0+0+ -8 + 16 = 0· 125 + 0·0625 = 0· 1875 = (0· 1875)10 7.

Convert the following binary number into decimal form (101-lOl)z = ( )10 Solution : (101·10l)z =1 x 22 + O x 21 + x 20 + x 2-1 + O x 2-2 + 1 x 2-3 1 =lx4+0x2+1xl+lx +Ox-21 22 1 + 1 x 23 = 4 + 1 + 0·5 + 0 + 0· 125 = 5·625 = (5·625)10

8. Convert the following binary number into decimal forms : ( 1010· 1011 )z = ( )10 Solution : (1010·10ll)z = 1 x 23 + 0 x 22 + 1 x 21 + 0 x 20 + + 0 x 2-2 + 1 x 2-3 + =8+0+2+0+1-+o+ + 16 2 8 = 10 + 0·5 + 0· 125 + 0·0625 = 10·6875 = (10·6875)10

x 2-1 x 2-4

NUMBERING SYSTEMS AND DIGITAL CODES

31

9. Convert (1001010lh to its equivalent decimal number. [B.Com.(C.U.) 2005) Solution :

(10010101h = ( )10 (10010101h = 1 x 21 + 0 x 26 + 0 x 25 + 1 x 24 + 0 x 23 + 1 x 22 + 0 x 21 + 1 x 20

= 128

+ 0 + 0 + 16 + 0 + 4 + 0 + 1

= 149 = (149)10

3.3.2 Conversion of Decimal Number into Binary Number The method to be followed is the successive division of the decimal number by the base 2 till quotient number of successive division cannot be divided by 2. The procedure may be given stepwise as follows : Step--1 Divide the given number N by 2 and let the resultant quotient be Q 1 and the remainder be R1. Step-2 Again divide the resultant quotient Q1 by 2 and let the remainder be R2, and continue the same procedure till the quotient becomes 0.

ILLUSTRATIVE EXAMPLES 10. Convert the following decimal number into binary equivalent : (282)i 0

=(

h

Solution. 2 ~

282 141-0 (= R l ) - - - - - - - - - - - - - - - - - - - .

2 ~

70-1 (= R z ) - - - - - - - - - - - - - - - - - - - .

2 ~

35-0 (= R J ) - - - - - - - - - - - - - - - - .

2 ~

17-1

(= R4)----------~

8-1

(=Rs)-----------.

4-0

(=~)-----~

2 ~

2 ~

2 ~

2-0

2 ~

1-0

2 ~

0-1

Now collect the remainders and put the same in reverse order, i.e., from last to first. Thus from resultant remainders (R) after following step-2, we g~t, (282)10 = (10001 lOlOh

32

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

11. Find the binary equivalent of (5731) 10 Solution. (5731) 10

=(

h

2 5731 2 2865-1 2 1432-1 2 716-0 2 358-0 2 179-0 2 89-1 2 44-1 2 22-0 2 11-0 2 5-1 2 2-1 2 1-0 2 0-1 :. the binary equivalent of (5731) 10 = (101100!10001lh 12. Convert the following decimal Number into binary equivalent. (111)10 = ( h Solution.

2 2 2 2 2 2 2 2

111 55-1 27-1 13-1 6-1 3-0 1-1 0-1

Thus the binary equivalent of (111) 10 = (llOllllh 13. Convert 0·33 into its binary equivalent. Solution.

0·33 x 2 [ill ·66 x 2 DJ ·32

x 2 [ill ·64 x 2 []}28 x 2 1]}56

x 2

OJ· 12

and so on.

NUMBERING SYSTEMS AND DIGITAL CODES

33

Thus for the fractional part of the number collect the digit preceding the decimal point after multipling by 2 in normal and consecutive order, i.e., from first to last. Now we get, (0·010101). :. the binary equivalent of (0·33) 10 = (0·010101)z. Note : It may be noted that in the binary equivalent, figure up to six places after decimal point is considered correct unless the figure becomes zero after decimal point. 14. Covert 0·671875 into binary equivalent. Solution.

0·671875 x 2 []·343750

x 2 [QJ-687500

x 2 []·375000 x 2 [QJ-750000 x 2 []·500000 Thus (0·671875) 10 = (0· 1010ll)z 15. Convert the following decimal number into binary form. (41·6875)10 = ( )z Solution.

Integer part of the number is2 41 2

20-1

2 2

10--0 5-0

2

2-1

2 2

1-0 0-1

Fraction part of the number is 0·6875 . . 0·6875 x 2

DJ ·3750 x 2

illl·7500

x 2 []·5000 x 2 ITJ·OOOO Thus (41) 10 = (10100l)z and (0·6875) 10 = (O·lOll)z Therefore, (41 ·6875) 10 = (101001 · lOll)z l.T. App. in Business-3

34

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

16. Find the binary equivalent of (30·375) 10

[B.Com. (C.U.) 2005]

Solution. (30·375)10 = ( h . . integer part of the number is 30. 2 30 2 15---0 2 7-1 2 3-1 2 1-1 2 0-1 Thus (30) 10 = (111 lO)z Again, fractional part of the number is 0·375 .. 0·375 x 2 [QJ ·750 x 2 []}500 x 2

ITJ·ooo Thus (0·375) 10 = (O·Oll)z :. (30·375) 10 = (11110·011) 2

3.4 Octal Number Systems In Octal Number there are only eight possible digits (0 to 7). In a single position there can be eight symbols or digits, viz., 0,1,2,3,4,5,6,7. The largest single digit is 7 which is one less than the base 8. Therefore, in the Octal Number System the base or radix is 8. The postiion of a digit to the left of the octal point carries a weightage in ascendfog powers of eight. This system is more popular with microprocessors, because the number represented in Octal System can be used directly for input and output operations.

3.4.1 Conversion of Octal Numbers to Decimal Numbers The procedure for conversion of Octal Numbers to their decimal equivalent is similar as to conversion of binary numbers into their decimal equivalent, but with an exception that the base or radix used in this system is 8 instead of 2 as used in binary. Thus a number in radix 8 can be converted to the familiar decimal system by forming the sum of the weighted digits. For example, octal 736 is converted into decimal form as follows. )10 (736) = ( :. (736) 8 = 7 x gz + 3 x 8' + 6 x 8 = 7 x 64 + 3 x 8 + 6 x 1 = 448 + 24 +6

= 478 = (478)10

3.4.2 Conversion of Decimal Numbers to Octal Equivalence Integer part of the decimal number can be converted into its octal equivalent by progressively a repetitively dividing the decimal number by 8 and collecting the remainders till the quotient becomes 0. The remainders are taken in the reverse order and these

NUMBERING SYSTEMS AND DIGITAL CODES

35

constitute the octal number integer. Coversion of (44)i 0 to its octal equivalent may be worked out as follows

~

Thus (44) 10 = (54)g Fractional part of the decimal number can be converted into its octal equivalent by successively multiplying the decimal fraction by g and collecting the CARRY DIGITS till the result of multiplication becomes 0 with a certain carry digit or when the desired number of digit (up to six places) have obtained. For example, decimal number (0·54) 10 may be converted into its octal equivalent as follows 0·54 x g = 0·32 with a carry digit 4 0·32 x g = 0·56 with a carry digit 2 0·56 x g = O· lg with a carry digit 4 and so on. :. (0·54)10 = (0·424)g Note : The carry digits are collected in consecutive order, i.e., from first to last. ILLUSTRATIVE EXAMPLES 17. Convert the following octal number to their decimal equivalent (2g3) 8 = ( ho Solution. (2g3) 8

=2

x g2 + g x g 1 + 3 x go

= 12g + 64 + 3

= 195 . .. (2g3)g = (195)10 18. Convert the following octal number to their decimal form (1347)g = ( )10 Solution.

(1347) 8 = 1 x g3 + 3 x g2 + 4 x g1 + 7 x go = 1 x 512 + 3 x 64 + 4 x g + 7 x 1 = 512 + 192 + 32 + 7 = 743 .. (1347)g = (743)10 19. Convert the following octal number into decimal form (0·402) = ( )10 Solution. (0·402)g

= 4 x g-1 + 0 x g-2 + 2 x g-3 = 4 X1- + 0 X -1+ 2 X gl g2 g3

= 0·5

+ 0 + 0·0039·

= 0·5039

.. (0·402)g = (0·5039)10 20. Find the following octal number into decimal form (0·31020)g = ( )10

36

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Solution. (0·31020)g = 3 x g-1 + 1 x g-2 + 0 x g-3 + 2 x g--4 + 0 x g-5

= 3 x _l_ + 1 x - 1-+ 0 x _l_ + 2 x 1 + 0 x g1 g2 g3 g4 gS = 0·375 + 0·0156 + 0 + 0·0005 + 0 = 0·3911 = (0·31020)g = (0·3911)10 21. Convert the following octal number into decimal number : (339·55)g = ( )10 Solution. (339·55) 8 = 3 x g2 + 3 x g1 + 9 x go + 5 x g-1 + 5 x g-2

=3x64+3xg+9xl+5xl+5x g g2

..

= 192 + 24 + 9 + 0·625 + 0·07g = 225·703 (339·55)g = (225·703)10

22. Convert the following octal number into decimal equivalent. (7362·02345)g = ( )10 Solution. Integer part of the octal number is (7362) 8 = 7 x g3 + 3 x g2 + 6 x g1 + 2 x go = 7 x 512 + 3 x 64 + 4g + 2 = 35g4 + 192 + 4g + 2 = 3g26 . . . (7362)g = (3g26)10 Fraction part of the octal number· is (0·02345)8 = 0 x g- 1 + 2 x g-2 + 3 x g-3 + 4 x g--4 + 5 x g-5 1 =Ox _l_ +2x _l_ +3x - 1-+4x - - + s x gl g2 g3 g4 gS

= 0 + 0·0313 + 0·0059 + 0·0010 + 0·0002 = 0·03g4 . . . (0·02345)g = (0·03g4)10 Thus (7362·02345) = (3g26-03g) 10 23. Convert the following decimal number to their octal equivalent : (7g5)10 = ( )g Solution. g 7g5 g 9g_ 1 g 12-2 g 1-4 0-1 Thus the octal equivalent of (7g5)w = (1421) 8 24. Convert the following decimal number to their octal equivalent : (gl59)10 = ( )g

NUMBERING SYSTEMS AND DIGITAL CODES

37

Solution. 8 8 8 8 8

8159 1019-7 127-3 15-7 1-7 0-1 :. thus the octal equivalent of (8159) 10 = (17737) 8 25. Convert the decimal fraction to their equivalent octal fraction : (0·25)10 = ( )g

Solution. 0·25

x 8 [I)·OO Since the fractional part has become zero, there is no need to proceed further. Thus, (0·25) 10 = (0·2) 8 1 Check : (0·2) 8 = 2 x 8-1 = 2 x g = 2 x 0· 125 = (0·25) 10 26. Convert the following decimal number into the octal equivalent (0·21875)10 = ( )g Solution. 0·21875 x 8 []·75000 x 8

ffi]·OOOOO

Thus Octal equivalent of (0·21875) 10 = (0· 16)8

27. Find the octal equivalent of (635·78) 10

Solution. Integer Part : 8 635 8 79-3 8 9-7 8 1-1 0-1 Thus the remainders written in the reverse order give the equivalent octal number as (1173) 8 Now Fractional Part 0·78 x 8 [6]·24 x 8

OJ -92

x 8 [I] ·36 and so on.

38

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

.. writing the carry digits in the normal consecutive order, the octal equivalent of the decimal fraction (0·78~0 is (0·617) 8 Thus combining the two results, we get (635·78) 10 = (1173·617) 8 28. Find the octal equivalent of (28· 125)i 0 Solution. Fractional Part

0·125

x 8 []·000 Therefore, octal equivalent of (28· 125) 10 in (34· 1) 8

3.5 Hexadecimal Number

S~tem

The Hexadecimal Number System has a base of 16. There can be sixtecr symbols in a single position. The maximum decimal value will be one less than the radix (16), i.e., 15. The 16 symbols of the hexadecimal systems are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E & F. The last six symbols are unfortunately identical to the letters of the alphabet and can cause confusion at times. However, this is the convention that has been adopted, when used to represent hexadecimal digits, the symbols A, B, C, D, D, E and F correspond to the ~ecimal numbers 10, 11, 12, 13, 14, 15 respectively. Decimal equivalent of a hexadecimal number is equivalent to the sum of different digits multiplied by their respective place values or weights. A decimal number can be converted into an equivalent hexadecimal number by successively dividing the integer part of the decimal number by the radix 16 and noting the remainders till we reach 0 and arranging the remainders in reverse order (from last to the first). In case of fractional part of a decimal number by successively multiplying the decimal fraction by 16 and recording the CARRY DIGITS till the result of multiplication becomes 0 or desired number of digits have been obtained and then arranging these carry digits in the normal and consecutive order (i.e., from first to last). • Relative values between the four types of number system, viz., decimal, binary, octal and hexadecimal are given in the following table : Table 3.1 : Relative Values among Decimal, Binary, Octal and Hexadecimal Numbers Decimal

0 1 2 3 4 5 6 7 8 9

Binary

0 1 10 11 100 101 110 Ill 1000 1001

Octal

Hexadecimal

0

0

1

1

2 3 4 5 6 7 10 11

2 3 4 5 6 7 8 9 Contd.

39

NUMBERING SYSTEMS AND DIGITAL CODES

Decimal IO 11 12 13 14 15 16

Binary IOlO IOll 1100 lIOl llIO 1111 10000

Octal 12 13 14 15 16 17 20

Hexadecimal A B

c D E F IO

ILLUSTRATIVE EXAMPLES 29. Convert the following hexadecimal number into decimal equivalent : (121B)l6 = ( )10 Solution. (1218) 16 = 1 x 16 3 + 2 x 16 2 + 1 x 16 1 + 11 x 16 o [Here B = 11) [Since the hexadecimal digits of the symbols A, B, C, D, E & F corespond to decimal numbers IO, 11, 12, 13, 14 and 15 respectively] = 4096 + 512 + 16 + 11 = 4635 .. (121B)16 = (4635)10 30. Convert the following hexadecimal number into decimal equivalent : (125F)16 = ( )10 Solution. (125F) 16 = 1 x 16 3 + 2 x 16 2 + 5 x 16 1 + 15 x 16 o [Here F = 15) = 1 x 4096 + 2 x 256 + 5 x 16 + 15 x 1 = 4096 + 512 + 80 + 15 = 4703 .. 125 (F) 16 = (4703) 10 31. Convert the following hexadecimal number into decimal equivalent : ) 10 (ABCD) 16 = ( Solution. (ABCD)16 = IO x 16 3 + 11 x 16 2 + 12 x 16 1 + 13 x 160 = 10 x 4096 + 11 x 256 + 12 x 16 + 13 x 1 = 40960 + 2816 + 192 +13 = 43981. .. (ABCD) 16 = (43981) 10 32. Convert the following hexadecimal into decimal equiyalent : (O·All) 16 = ( )10

Solution. (O·Al1) 16 = IO x 16-1 + 1 x 16-2 + 1 x 16-3 1. 1 =IOx-+lx--+lx 1 16 16 2 16 3 = 0·625 + 0·0039 + 0·0002 = 0·6291 .. (O·All) 16 = (06291) 10

40

INFORMATION TECHNOLOGY AND. ITS APPLICATION IN BUSINESS

33. Convert the following hexadecimal into decimal equivalent : (0·1E2)16 = ( )10 Solution. (0·1E2)16 = 1 x 16- 1 + 14 x 16-2 + 2 x 16-3 1 = 1 x _!_ + 14 x _l_ + 2 x 16 162 163 = 0·6250 + 0·0547 + 0·0005 = 0·6802 .. (0· 1E2)16 = (0·6802)10 34. Convert the following hexadecimal into decimal equivalent : (A2F.D) = ( )10

Solution. (A2F.D) 16

= 10

x 162 + 2 x 161 + 15 x 160 + 13 x 16-1

= 10 x 256 + 2 x 16 + 15 x 1 + 13 x

1

16

= 2560 + 32 + 15 + 0·81 = 2607·81 .. (A2F.D) 16 = (2607·81) 10 35. Convert the following hexadecimal number into decimal number : (ABC.F) 16 = ( ) 10

Solution. (ABC.F) 16

= 10 x = 10 x = 2560

162 + 11 x 161 + 12 x 160 + 15 x 16-1

256 + 11 x 16 + 12 x 1 + 15 x _!_ 16 + 176 + 12 + 0·94 = 2748·94 . . (ABC.F) 16 = (2748·94) 10 [B.Com. (C.U.) 2005] 36. Convert (FACE) 16 to its equivalent decimal. Solution. (FACE) 16

= 10 x 163 + 10 x 162 + 12 x 161 + 14 x 160 = 15 x 4096 + 10 x 256 + 12 x 16 + 14 x 1 = 61440 + 2560 + 192 + 14 = 64206 . . (FACE) 16 = (64206) 10 Conversion of decimal to hexadecimal. 37. Convert the decimal number 745 to its equivalent hexadecimal (745)10 = ( )16

Solution. 16 745 16 46-9~R 1 16 2 -14 = E ~ R2 0 - 2 ~ R3 . . collecting the remainders in reverse order (i.e., from last to first), we get, R 3, R 2, R 1, equivalent to 2 E 9 respectively. Thus (745) 10 = (2E9) 16

NUMBERING SYSTEMS AND DIGITAL CODES

41

38. Convert the following decimal number to its equivalent hexadecimal (2163)10 = ( )16 Solution.

16 2163 16 135-3 ~ R1 16 8-7 ~ R1 0-8 ~ R3 .. (2163)10 = (873)16 39. Convert the following fractional decimal to its equivalent hexadecimal (0·39)10 = ( )16 Solution. 0·39 x 16 lliJ·24 x 16 []]·84

x 16 'D' ~ [Ll] · 44 and so on. Thus collecting the CARRY DIGITS in the normal and consecutive order, we get (0·39) 10 = (0·63D)16· Check : (0·63D) 16 = 6 x 16-1 + 3 x 16-2 + 13 x 16-3 1 =6x+ 3 x - -1+ 1 3 x 1 16 162 163

= 0·375 + 0·0117 + 0·0032 = 0·3899 = 0·39 (say) . . (0·63D) 10 = (0·39) 10 40. Convert the following fractional decimal to its equivalent hexadecimal number (0·75)10 = ( )16 Solution. 0·75 x 16 'C' ~ [!1J ·00 Thus (0·75)1 0 = (O·C)16 41. Convert the following decimal into its equivalent hexadecimal (627·35)10 Solution.

= (

Integer part is 627 16 627 16 39-3 16

..

2-7 0-2 (627)10 = (273)16

)16

42

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Again the fractional part is 0·35 0·35 x 16 (IJ·60 x 16 [[] ·60 and so on. Thus (0·35) 10 = (0·59) 10 Combining the results of the integer part and fractional part, we get, (627·35)10 = (273·59)10 42. Convert the founding decimal number into hexadecimal from (3465· 12)10 = ( )16 Solution. First, we have to solve the integer part, 3465. . . 16 3465 16 216-9 16 13-8

0-13 = D Thus (3465) 10 = (D89) 16 Again, the fractional part is 0· 125. .. 0·125 x 16 ~·00

.. (0· 125)10 = (0·2)16 Therefore, combining the results of integer and fractional part, we get, (3465·125) 10 = (D89·2)16·

3.6 Conversion from one System to another System The Conversion from and to binary, octal and hexadecimal representation plays an important part in digital computers. Since 23 = 8 and 24 = 16, each octal digit corresponds to three binary digits and each hexadecimal digit corresponds to four binary digits. The conversion from binary to octal is easily accomplished by partitioning the binary numbers into groups of three bits each. The corresponding octal digit is then assigned to each group of bits and the string of digits so obtained gives the octal equivalent of the binary numbers. Consider, for example, a 16-bit-register. Physically one may think of the register as composed of 16 binary storage cells, with each cell capable of holding either I or a 0 Ler the bit configuration stored in the register be shown as follows 1 2 7 5 4 3 ~ Octal 1 7 O 1 0 ' '1111 TOf 1001 'o"l7 ~ Binary A B 6 3 ~ Hexadecimal Fig. 3.1. Binary, Octal and Hexadecimal Conversion

Since a binary number consists of a string of 1's and O's, the 16-bit register can be used to store any binary number from 0 to (216_ 1). Each group of three bits is assigned its octal equivalent and placed on top of the register. The string of octal digits so obtained represents the octal equivalent of binary number.

..

43

NUMBERING SYS!-i..MS AND DIGITAL CODES

The following Table shows the binary-coded octal numbers relations. Table 3.2 Octal Number

Binary-coded Octal Number Binary Coded Octal

0 1 2 3 4 5 6 7

Decimal Equivalent

000 001 010 011 100 101 110 111

0 1 2 3 4 5 6 7

10 001 000 8 11 001 001 9 12 001 010 10 24 010 100 20 143 001 100 011 99 011 111 000 370 248 The above table lists a few octal numbers and their representation in registers in binary coded form. The binary code is obtained by the procedure explained above. Each octal digit is assigned a 3-bit code as specified by the entries of the first eight digits in the table. 3.6.1 Octal-Binary Conversion From octal number to binary number, conversion may be appropriately done by two alternative methods as follows : Method 1 : Suppose there is a conversiory of octal number (437·152) to the binary number. Then we can appropriately convert the said octal number to binary number as follows : (4 3 7 . 1 5 2 )g j,

j,

j,

j,

j,

j,

= (100

011 111 · 001 101 OlO)i Thus, (437·152)8 = (100011111·001 101010)i or; (10001llll ·001101)i [After decimal five or six digits are taken as appropriate] From Table Octal 0

Binary 000

001 010 011 100 101 110 111 Method 2 : We can convert the same by performing the following steps : Step 1 : Convert the said octal number into decimal equivalent. 1

2 3 4 5 6 7

44

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Step 2 : Again, perform the procedures taking this decimal equivalent (step-1) as the conversion from decimal to binary equivalent that we have learnt. Check : As per step-I, (437·152)g = ( )10 (437·152) 8 = 4 x g2 + 3 x g1 + 7 x go + I x g-1 + 5 x g-2 + 2 x g-3 = 256 + 24 + 7 + 0· 125 + 0·078 + 0·004 = (287·207)10 Then as per step-2, Integer Part = 287 2 2 2 2 2 2 2 2 2

287 143-1 71-1 35-1 17-1 8-1 4-0 2-0 1-1 - 0-1 Thus (287)i 0 = (lOOOlllll)z Again, we have the fractional part-2, (0·207)10 = ( h .. 0·207 x 2 [Q}414 x 2 [Q] ·828 x 2 ITJ·656 'X 2 ITJ·312 x 2 [Q] ·624 x 2 ITJ·248 and so on. Combining the two results, we get ( 100011111·001101) 2 :. (437· 152)g = (100011111 ·001101)z. 3.6.2 Binary-Octal Conversion Binary number can be converted into an equivalent octal number by splitting the INTEGER and FRACTIONAL PARTS in groups of three bits starting from the binary point on both sides. 'O's can be added to complete the outside groups, if necessary. Similarly, we can perform the appropriate coversion from binary to octal number by the following two alternative methods.

45

NUMBERING SYSTEMS AND DIGITAL CODES

Method 1: Let the conversion of binary number (101001110010ll)z to the equivalent octal Number. :. (10100111001011)z = ( )g Now we have to group all the digits into blocks of three, adding some zeros, if necessary, on the Left of the given numeral. Thus we have -t 010 100 111 001 011 Replace each block (Considering it as a binary numeral) by the corresponding Octal digit. We get, 010 100 111 001 011

.l.

.l.

.l.

.l.

.l.

2 4 7 1 3 Therefore, (10100111001011)z = (24713) 8. Method 2 : We can convert the same by performing the following steps Step 1 : Convert the said binary number into decimal equivalent. Step 2 : Again perform the procedures taking this decimal equivalent (step-1) as the conversion from decimal to octal equivalent that we have learnt. Check : As per step-1, (101001110010ll)z = ( h~ :. (10100111001011)z = 1 x 213 + 0 x 212 + 1 x 211 + 0 + 210 + 0 x 29 + 12 x 2s + 1 x 21 + 1 x 26 + 0 x 2s + 0 x 24 + 1 x 23 + 0 x 22 + 1 x 21 + 1 x 20 = 10699 = (10699)10 Then as per step-2, 8 10699 8 1337-3 8 167-1 8 20-7 8 2-4 0-2 Thus (10699) 10 = (24713) 8 • 3.6.3 Octal-Hexadecimal Conversion and vice versa For Octal-Hexadecimal conversion, we can go from octal numbers to its binary equivalent and then from binary equivalent to hexadecimal equivalent. For octalhexadecimal conversion, we can go from hexadecimal numbers to its binary equivalent and then from binary number to the octal number. The equivalence among hexadecimal numbers, binary numbers and decimal numbers are given below Table 3.3

Binary-Coded Hexadecimal Numbers

Hexadecimal Number

Binary Coded Hexadecimal

Decimal Equivalent

0

0000 0001 0010 0011 0100 0101 0110

0 1 2 3 4 5 6

1

2 3 4 5 6

Contd.

46

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Hexadecimal Number

Binary Coded Hexadecimal

Decimal Equivalent

0111 7 1000 8 1001 9 1010 10 B 1011 11 1100 12 c D 1101 13 1110 14 E 1111 15 F Comparing the binary coded octal and hexadecimal numbers with their binary number equivalent, we find that the bit combination in all three representations is exactly the same. For example, decimal 99, when converted to binary, becomes 1100011. The binary coded octal equivalent of decimal 99 is 001 100 011 and the binary coded hexadecimals of decimal 99 is 0110 0011. 7 8 9 A

ILLUSTRATIVE EXAMPLE 43. Convert the following Octal Number to hexadecimal number. h6 (1234)g = (

Solution. By our previous knowledge, we can successfully convert the above number by two alternating methods as follows : Method 1 : To convert the number 1234 from octal to hexadecimal, we will first represent 1234 in BCD (Binary-Coded Decimal) by using 3 binary bits for each character. Therefore, we will combine these bits in groups of four, starting from right to left and adding significant zeros (0) at the end of left digit as necessary. Thus (1234)8 may be written as (1 2 3 4 )g

t

=

001

= =

0010

2

t

t

t

011 100 010 [Now arrange 4 digits as a block] 1001 1100 -t [As per binary-coded hexadecimal] 9 C -t hexadecimal number

.. (1234)g = (29C)l6. Method 2 : We can convert the same by performing the following steps Step 1 : Convert the said Octal Number into decimal equivalent. Step 2 : Again perform the procedure taking this decimal equivalent (Step-1) for conversion from decimal number to hexadecimal equivalent. Check : As per Step-1 : (1234) 8 = 1 x 83 + 2 x g2 + 3 x g1 + 4 x go = 512 + 128 + 24 + 4 = 668. :. (1234)g = (668)10 Then on per step-2 : 16 668 16 41-12 = 'C' 16 2-9 0-2 Thus (1234) 8

= (29C)16·

NUMBERING SYSTEMS AND DIGITAL CODES

47

44. Convert the following hexadecimal number to octal number (A2C5) 16 = ( )8 Solution. As per Method 1 (A 2 c j, j, j, [As 0101 1010 0010 1100 [ Grouping a block of three digits each ] Adding 'O' as necessary. j, 011 001 010 001 000 j, j, j, j, j, 3 1 2 0 Thus (A2C5) 16 = (121305) 8

per Binary Coded Hexadecimal]

101 j, 5

+- From right to Left t- Octal numbers

As per Method 2 :

= 10 x 16 3 + 2 x 16 2 + 12 = 40960 + 512 + 192 + 5 = 41669. .. (A2C5) 16 = (41669) 10 •

(A2C5)16

Again we have(41669)10 Thus, 8

=(

x 16 I + 5 x 16 0

)g

41669

8

5208-5

8

651-0

8

81-3

8

10-1

8

1-2 0-1

Collecting the remainders in reverse order. We get, 121305. .. (A2C5) 16 = (121305)8 • 3.6.4 Hexadecimal-Binary Conversion and Vice versa For Hexadecimal-binary Conversion replace each Hex-digit by its 4-bit binary equivalent. Here 4-bit equivalent indicates hex-system radix is fourth power of the radix of the binary systems, i.e., 16 = 2. Again, for binary-hexadecimal conversion break the binary number in the groups of 4-bits starting from the binary point and, if necessary, complete the outside group by adding 'O's and then put the Hex-equivalents of these 4-bits groups. ILLUSTRATIVE EXAMPLES

45. Convert the following hexadecimal number to Binary Number : )2 (CDEF) 16 = ( Solution. We can successfully convert the above number by two alternative methods as follows : Method 1 : To convert the given number from hexadecimal system to binary system each digit of the number is represented by its binary equivalent using a groups of four bits.

48

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

So, ( C D E j, j, j, 1100 1101 1110 1111 f - Binary Coded Hexadecimal Number. = (1100 llO llllO llllh Note : It is a very short-cut method. Method 2 : We can convert the same by performing the following steps Step 1 : Convert the said hexadecimal number into decimal number. Step 2 : Again perform the procedures taking this decimal eq~ivalent (as per step-1) for the conversion from decimal to binary number. Check : As per Step- I : (CDEF) 16 = 12 x 163 + 13 x 162 + 14 x 161 + 15 x 160 = 49152 + 3328 + 224 + 15 = 52719 .. (CDEF)i 6 = (52719) 10 Then another Step-2 : 2 2 2 2 2 2 2 2 2

52719 26359-1 13179 - 1 6589 - 1 3294 - 1 1647 - 0 823 - 1 4ll - 1 205 - 1

2 2 2 2 2

102 -1 51 - 0 25 - 1 12 - 1 6-0

2 2

3 - 0 1-1 0-1 Collecting the remainders in reverse order, we get (1100 11011110 llllh 46. Convert the following binary number into hexadecimal number : (lOllOlllh = ( )16 Solution. We can appropriately convert the above number by applying two alternative methods as follows : Method 1 : Here the binary number is (lOll Olllh Now to convert hexadecimal number we have to make a group of four digits of such number as follows. 1011 0111----,l B Thus (lOll Olllh

7

= (B7)16

f-

Binary Coded Hexadecimal Number

NUMBERING SYSTEMS AND DIGITAL CODES

49

Method 2 : We can convert the same by perfonning the following steps Step 1 : Convert the said binary number into decimal equivalent. Step 2 : Again, perform the procedures taking this decimal equivalent (as per Step- I) for conversion from decimal to hexadecimal number. Check : As per step-1 : · (1011 01 ll)z = 1 x 21 + 0 x 26 + 1 x 2s + 1 x 24 + 0 x 23 + 1 x 22 + 1 x 21 + 1 x 20 = 128 + 0 + 32 + 16 + 0 + 4 + 2 + 1 = 183 . . (1011 Olll)z = (183) 10 . Then as per Step-2 16

183

16

11-7

= 'B' are = B7

0-11

The remainders Thus (1011 Olll)z

= (B7)i 6

MORE ILLUSTRATIVE EXAMPLES

47. Convert the following octal number into equivalent hexadecimal. (1357)g = ( )16 Solution. To convert the given Number from octal to hexadecimal, let us first represent each digit by a group of three binary bits. Thereafter, we combine these bits in groups of four starting from right to left and adding significant zero at the end of left side, if required. = 001 011 101 111 :. (1357)g [Regrouping on 4-digit] = 0010 1110 1111 E F f - Hexadecimal equivalent. = 2 :. (1357) 8 = (2EF)16· Note : This conversion may be done by the application of Method-2. 48. Write the BCD equivalent of the following binary numbers. [C.A. 1995] (i) 110101 ; (ii) 10111 ; (iii) 1010110 Solution. (i) (110101)2 = 1 x 2s + 1 x 24 + O x 23 + 1 x 22 + O x 21 + 1 x 20 = 32 + 16 + 0 + 4 + 0 + 1 = 53. Thus (110101)z = (53) 10 :. (5 3)10

.J,

.J,

0101

0011 (in BCD) 0011 in Binary Coded Decimal. (ii) (lOlll)z = 1 x 24 + 0 x 23 + 1 x 22 + 1 x 21 + 1 x 20 16 + 0 + 4 + 2 + 1 23. Thus (lOlll)z = (23) 10 . . (2 3)10

= 0101

=

.J,

=

.J,

0010 0011 ~ [as per BCD] .. (lOlll)z = 0010 0011 in BCD. I

l.T. App. in Business-4

50

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

1 x 26 +

ox

2s + 1 x 24 +

ox

23 +

(iii) (1010110h

=

Thus (1010110)i

= 64 + 0 + 16 + 0 + 4 + 2 + 0 = 86. = (86) 10

..

(8

.!.

x 22 + 1 x 21 + 0 x 20

6)10

.!.

1000 0110 [As per BCD, i.e., from Table] .. (1010110)i = 1000 OllO in BCD. 49. Convert the follwoing hexadecimal number into binary number : h (EF92)16 = ( Solution : By applying short-cut method (i.e., Method-I), we convert the given number from hexadecimal to binary, each digit of the number will be represented in binary form using a group of 4 bits. Hence, ( E 9 F

=

.!.

.!.

.!.

lllO

llll

1001

0010

f-

[As per binary coded hexadecimal]

= (lllO llll 1001 OOIO)i .. (EF92) 16 = (lllO 11111001 OOlO)i 50. Convert the following octal number into hexadecimal number (605)g = ( )16 Solution : To convert the number 605 from octal to hexadecimal system, we will represent 605 in BCD form using 3 binary bits for each digit. Thereafter, we will combine these bits in groups of four, starting from right to left and adding significant zero, if necessary.

..

= = =

(6

0

.!.

.!.

5)g

.!.

llO 00001 1

000

101 0101 5

10000 8

[As per binary coded hexadecimal equivalent]

f-

= (185)16 51. Convert the following binary number to octal number (10ll01.1l0lh = ( )g Solution : To convert into the octal number, we have to make using 3 binary bits each group from right to left in case of integer part and the procedure is same from right to left in Case of fractional part, except O's will be added at the right-end, if necessary.

:. (101101-llOlh

= 101

101 llO 100

1l l

.!..!.

(twy zeros added)

=

5

5

6

4

f- [

As per binary coded octal equivalent ]

:. (101101.1101) = (55·64)g Note : The above solution may be done by applying alternative Method-2.

NUMBERING SYSTEMS AND DIGITAL CODES

51

52. Convert (FACE) 16 to its equivalent octal numbers. [B.Com. (C.U.) 2005] Solution : )8 (FACE) 16 = ( By applying alternative Method-2 for the conversion, we have, (FACE) 16 = 15 x 163 + 10 x 162 + 12 x 161 + 14 x 160 = 15 x 4096 + 10 x 256 + 12 x 16 + 14 x 1 =·61440 + 2560 + 192 + 14 = 64206 . . . (FACE) 16 = (64206) 10. Again, we have8 64206 8 8025-6 8 1003 -1 8 125-3 8 15-5 8 1-7 0-1 By collecting the remainders in reverse order, we get, (175316) 8 :. (FACE)i 6 = (175316) 8 Note : This conv~rsion may be appropriately done by applying alternative Method-1.

3.7 Data Representation Binary information in digital computers is stored in memory or processor registers. Registers contain either data or control information. Control information basically is a bit or a group of bits used to specify the sequence of command signals required for manipulation of the data in other registers. Data are numbers (0 to 9) and other binary coded information (A-Z or special characters) that are operated on to achieve required computational results. The method of data representation in a form of suitable storing in the memory of a computer and for processing by the CPU (Central Processing Unit) is called internal data representation. Generally in a programming language the following categories of data are used : 10 ~ numerals (0 to 9) 26 ~ alphabets (A to Z) 16 ~Special characters (Such as, - ; + ; I ; * (asterisk) ; , (coma) ; : (colon); > (greater than) ; < (less than) " (quotation mark) ; $ (symbol of dollar) ; etc.

3.7.1 Data Types Therefore, data types formed in the registers of digital computers may be classified in the following categories : (i) Numbers used in arithmetic computation. (ii) Letters of the alphabet used in data processing. (iii) Other discrete symbols used for specific purposes. All types of data, except binary numbers, are represented in computer registers in binary coded form. This is because registers are made of flip-flops, and flip-flops are two state devices that can store only 1's and O's. The binary number sy&tem is the most natural system to use in a digital computer. But sometimes it is convenient to employ different number systems, especially the decimal number system, since it is used by people to perform arithmetic computations.

52

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

3.7.2 Fixed point Data Representation Fixed point data representation can be described as unsigned numbers like positive integers including zero. However, to represent negative integers we need a notation for negative values. In ordinary arithmetic, a negative number is indicated by a minus sign and a positive number by a plus sign. It is only for hardware limitation, computers must represent everything with l's and O's including the sign of a number. As a consequence, it is mandatory to represent the sign with a bit placed in the left-most position of the number. The convention is to make the sign bit equal to 'O' for positive and to 'l' for negative. Incidentally, 0 and 1 of the binary system are referred to as bits which are also called binary digits. On the contrary, a group of binary digits or bits (usually eight) operated on as a unit is known as a byte. A particular byte represents either any of the alphabet (a, b, c, ... ) or it is of numeric character (0 - 9). Fixed point data representations are of the following : 1. Fixed point integer data representation. 2. Fixed point decimal data representation. Fixed point integer data : When an integer binary number is positive the sign is represented by 0 and the magnitude by a positive binary number. Again, when the number is negative, the sign is represented by 1. and the number is represented in one of the three possible ways as follws : (i) Signed Magnitude representation. (ii) Signed-1 's complement representation. (iii) Signed-2's complement representation. The signed magnitude representation of a negative number consists of the magnitude and a negative sign. In other two representations, the negative number is represented in either the l's or 2's Complement of its positive values. Fixed point decimal data : The representation of decimal numbers in registers is a function of the binary code used to represent a decimal digit. A 4-bit decimal code requires four flip-flops for each decimal digit. A 4-bit word is also known as a Nibble. The representation of 4385 in BCD requires 16 flip-flops, four flip-flops for each digit. The number will be represented in a register, with 16 flip-flops as follows : 0100 0011 1000 0101 3.7.3 Floating Point Data Representation The floating point data representation of a number has two parts. The first part represents the significant digits of the number called mantissa. The second part designates the position of the decimal or binary point and is called the exponent. The fixed point mantissa may be a fraction or an integer. For example, the decimal number + 6132·789 is represented in floating point with a fraction and an exponent as follows : Exponent Fraction + 0·6132789 +04 Floating point is always interpreted to represent a number in the following form: m x re, where the mantissa m and the exponent e are physically represented in the register including their signs. A floating point binary number is represented in a similar manner except that it used radix 2 for the exponent. For example, the binary number + 1001 · ll is represented with an 8-bit fraction and 6-bit exponent as follows : Exponent Fraction 000100 01001110

NUMBERING SYSTEMS AND DIGITAL CODES

53

3.8 Digital Coding Digital computers are the binary number system which has two digits 0 and 1. A unit of inoformation expressed as either a 0 ·or 1 in binary notation is calkd a bit. Information is represented in digital computers in groups of bits. By using various coding techniques, groups of bits can be made to represent not only binary numbers but also other discrete symbols such as decimal digits letters of alphabet. This is precisely known as digital coding.

3.8.l Major requirements for a coding system Most important requirements for a practical coding system may be pointed out as follows : (i) The code should be designed to identify the characteristics of the item of data it represents. (ii) Each code should represent one and only one value of the data. (iii) The codes should be as similar as possible to minimise storage requirements. (iv) The codes should be so designed as secrecy could be maintained in case of sensitive data. (v) The codes should be so designed as errors be minimal while handling a computer. (vi) The codes must contain sufficient number of alphanumeric to represent all possible values of data: 3.8.2 Features of a good Coding System The most important feature of a good coding system may be outlined as follows : 1. Expansion : Each field of the code must be large enough to include all values of the attribute it represents. 2. Verification : Each total code for a number of a classification must contain a check digit for verification so that fields contain correct number and type of character. 3. Fixed Length : Fields of the code should be ideally of fixed length for the speed of processing. 4. Meaningfµlness : The codes should be meaningful, i.e., it should be commensurate to the value of the attribute and it must be clearly defined. 5. Objectives : The objectives of meaningful ccJes must be established precisely. 6. Feed back : All potential users of the coded information should be consulted and recommended before finalising the type and size of the code.

3.9 Binary Coded Decimal (BCD) The full form of BCD is Binary Coded Decimal. It is one of the early memory codes. Here each digit of a decimal number is converted into its binary form to facilitate the conversion process. A binary code is a group of n bits that assume upto 2" distinct combination of 1's and O's with each combination representing one element of the set that is being coded. Suppose a set of four elements can be coded by a 2-bit code with each element assigned one of the following bit-combinations; 00, 01, 10 or 11. A set of eight elements requires a 3-bit code, a set of 16 elements requires a 4-bit code, and so on. A binary code will have some unassigned bit-combinations if the number of elements in the set is not a multiple power of 2. A binary code that distinguishes among 10 elements must contain at least four bits, but six combinations will remain unassigned. Numerous different codes can be obtained by arranging four bits in 10 distinct combinations. The bit assignment, most commonly used for the decimal digits, is the straight binary assignment. This particular code is called Binary Coded Decimal (BCD).

54

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

The difference between, the conversion of decimal numbers into binary and the binary coding of decimal numbers is very significant to understand by a programmer. For example, when converted to a binary number, the decimal number 99 is represented by the string of bits 1100011 but when represented in BCD, it appears as 1001 1001. The only difference between a decimal number represented by the well known digit symbols 0, l, 2, ... ,9 and the BCD symbols 0001, 0010, ... ,1001 is in the symbols used to represent the digits. The number itself is exactly the same. A few decimal numbers and their representation in BCD are listed below : Table 3.4 : Binary Coded Decimal Numbers Binary Coded Decimals Decimal Number (BCD) Numbers

0 1 2

3 4 5 6 7 8 9 10 20

50 99 248

0001 0010 0101 1001 0010 0100

0000 0001 0011 1011 0100 0101 0110 0111 1000 1001 0000 0000 0000 1001 1000

Code for one decimal digit

3.10 Extended Binary Coded Decimal Interchange Code (EBCDIC) EBCDIC is an eight-bit code and is widely used. An 8-bit code permits 256 unique codes (28) which is more than enough for our twenty six (26) alphabetic characters, ten decimal digits and commonly used special symbols since this code can be used to handle all types of data (numeric, alphabetic and special symbols). Moreover, it is invariably used for business data processing by the types of computers-mainframe as well as minicomputers. Each EBCDIC character is represented by unique string of l's and O's consisting of eight bits. The four left-hand bits are referred to as zone bits and they identify the group classification of a character. The four right-hand bits are referred to as numeric bits. The EBCDIC representation can be summarised as follows : Characters

Zone Bits Numeric Bits 1111 0 from 9 0000 from 1001 A 1 1100 0001 1001 R 1101 J 0001 1001 1110 0010 1001 s z Therefore, in order to overcome the deficiency, 2 more zone bits are added to 6-bit BCD code to give birth to EBCDIC code (4-zone bits + 4-number bits). As a result, the number of character patterns increased from 64 (26) to 256 (28). The expansion is utilised to accommodate a large variety of printable characters and also several nonprintable control characters, e.g., printers spacing, cursor movement on the monitor screen,

55

NUMBERING SYSTEMS AND DIGITAL CODES

etc, with flexibility for fortune provisions. 8-bit EBCDIC code can be conveniently divided into two 4-bit groups to permit two hexadecimal characters for memory dump. The conversion process is listed an follows : Table 3.5 : EBCIDIC Code Character

Zone

Digit

Equivalent Hexadecimal No.

0 1 2 3 4 5 6 7 8

1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1100 1100 1100 1100 1100 1100 1100 1100 1100 1101 1101 1101 1101 1101 1101 1101 1101 1101

0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 0001 0010 0011 0100 0101 OllO 0111 1000 1001 0001 0010 0011 0100 0101 0110 0111 1000 1001

Fo F, F2 F3 F4 Fs F6 F7 Fg Fg C1 C2 C3 C4 Cs c6 C7 Cg C9 D, Dz D3 D4 Ds D6 D7 Dg D9

1110 1110 1110

0111 1000 1001

~ Es

9 A B

c D E

F G H I

J K L M N

0 p Q R

x y

z

E._i

3.11 American Standard Code for Information Interchange (ASCII) This code is available in two versions-the 7-bit and the 8-bit code. In the 7-bit version there are three-zone positions while in the 8-bit version there are four-zone position. This code is largely used by American Manufacturers as their Computers, internal codes and is also used in data communications. The 8-bit version of ASCII is primarily used by some brands of larger computers. On the other hand, the computer manufacturers together developed a 7-bit code and submitted it to the American National Standards Institute (ANSI) to make them issue a standard code. Thus ANSI issued the standard code and notified that every manufacturer shall have to conform to this code in its product. Therefore, a 7-bit code offered 128

56

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

(27 ) different combinations. It had 52 binary values for alphabet, both upper case and lower case 10 for numerals and 6 for special characters. It was a bit improvement over the BCD and is still being implemented in all the computer systems. As technology improved, the peripherals particularly printers offered more and more facilities. There was strong need to have more signals for controlling peripheral operations. Thus it was decided to revise the ASCII so that all the 8-bit versions could be used and the new characters incorporated. Therefore, a revised standard was issued by ANSI and was named ASCII-8 with the provision that the manufacturers will have an option to implement either ASCII-7 or ASCII-8 in their system according to their application hazards. The main difference in EBCDIC and ASCII codes is selection of bit patterns to be used in the zone portion. Another difference is that bits are serially numbered from right to left in the cases of ASCII and on the contrary, both the options are available, i.e., form left to right and from right to left for numbering of bits serially in case of EBCDIC. Moreover, data represented in ASCII format can be easily converted into EBCDIC format, and vice versa, to suit the requirements of a particular system. These systems have some drawbacks. (i) When numbers transmitted and used, their ASCII values for the same, are quite different from their numeric values. (ii) The process of conversion is quite slow when using these codes .. But to eliminate this problems IBM developed a code which assigned hexadecimal values and was very fast in arithmetic operations.

Computing Concept Table 3.6

Equivalent Hexadecimal Symbols of Numeric and Alphabetic Characters in ASCII 7 Code ASCII-7 Code

Character

0 I 2 3 4 5 6 7 8 9 A

B

c

D E F G H I

J

Zone

DIGIT

011 011 011 Oll 011 Oll Oll 011 011 Oll 100 100 100 100 100 100 JOO 100 100 100

0000 0001 0010 OOll 0100 0101 OllO Olli 1000 1001 0001 0010 OOll 0100 0101 0110 0111 1000 1001 1010

Equivalent Hexadecimal Symbols 30 31 32 33 34 35 36 37 38 39 41 42 43 44

45 46 47 48 49 4A Contd.

57

NUMBERING SYSTEMS AND DIGITAL CODES

Zone

DIGIT

Equivalent Hexadecimal Symbols

100 100 100 100 100 101 101 101 101 101 101 101 101 101 101 101

1011 1100 1101 1110 1111 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010

4B 4C 4D 4E 4F 50 51 52 53 54 55 56 57 58 59 5A

ASCII-7 Code

Character

K L M N 0 p

Q R

s T

u

v

w x y

z

Table 3.7 : Equivalent Hexadecimal Symbols of Numeric and Alphabetic Characters in ASCII 8 Code ZONE

DIGIT

Equivalent Hexadecimal Symbols

0101 0101 0101 0101 . 0101 0191 0101 0101 0101 0101 1010 1010 1010 1010 1010 1010 1010 1010 1010 1010 1010 1010 1010

0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 0001 0010 0011 0100 0101 0110 0111 . 1000 1001 1010 1011 1100 1101

50 51 52 53 54 55 56 57 58 59 Al A2 A3 A4 A6 A6 A7 A8 A9 AA AB AC AD

Character

0 1 2 3 4 5 6 7 8 9 A B

c D E F G H I J

K L M

ASCII-8 Code

Contd.

58

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Character

N

0

p Q R

s

T

u

v w x y

z

ASCII-8 Code ZONE

DIGIT

1010 1010 1011 1011 1011 1011 lOll lOll lOll 1011 lOll 1011 lOll

lllO llll 0000 0001 0010 0011 0100 0101 OllO 0111 1000 1001 1010

Equivalent Hexadecimal Symbols AE

AF BO Bl B2 B3 B4 BS B6 B7 B8 B9 BA

3.ti Gray Code (GC) Digital System can process data and discrete form only. Many physical systems supply continuous output data. The data must be connected into digital form before they can be used by a digital computer. Continuous or analog informations are converted into digital form by means· of an analog to digital converter. This concept is called reflected binary or Gray Code. Besically a Gray Code function is a function of the integers I. The idea of such Gray Code was first patented by Frank Gray for use in shaft encoders. The advantage of the Gray Code over straight binary number is that the Gray Code changes by only one bit as it sequences from one number to the next. In other words the changes from any number to the next sequencially is identified by a change of one bit from 0 to 1 or from 1 to 0.

3.12.1 Typical Application of Gray Code Gray Codes are applied in the following way (i) In case of analog data representation by the continuous change of a shaft position. (ii) In case of providing the timing sequences that control the operation in aditional computer. (iii) In case of classification of Venn diagrams. (iv) In case of architecture of communication codes. (v) In case of various types of bell ringing chips or integrated circuits. A Gray Code counter is a counter where flip-flops go through a sequence of states an specified in the following table :

R. Binary Code/ Gray Code ()()()()

0001 0011. 0010 0110 0111 0101 0100

Table 3.8 : 4-Bit Gray Code Decimal R. Binary Equivalent Code/Gray Code 0 1 2 3 4 5 6 7

llOO 1101 lll l lllO 1010 1011 1001 1000

Decimal Equivalent

8 9 10 ll 12 13 14 15

NUMBERING SYSTEMS AND DIGITAL CODES

59

3.12.2 Advantages of Gray Code (i) Gray Code counters remove the ambiguity during changeous from one state to · another state of counter. (ii) Gray Codes are significantly useful in one of the numerical operations with logic based calculation.

EXERCISES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

15.

16.

17.

18.

19.

20.

Define Decimal Number Systems. Define Binary Number Systems. What are the reasons for using Binary Number System. Define Octal Number System. What is Hexadecimal Number System. Define the concept of data representation. What is Fixed Point Data Representation and Floating Point Data Representation? Define Digital Coding System. Discuss the major requirements for a good coding system. Define the most salient features a good coding system. Define the concept of Binary Coded Decimal. What is Gray Code ? Discusss the application of Gray Code. What are the advantages of any Gray Code. Determine the decimal equivalent of the following binary numbers : )10 (i) (llOll)z = ( (ii) (110101)z = ( )10 (iii) (llOllll)z = ( )10 (iv) (lllOOOIOl)z = ( )10 (v) (1010101101 lO)z = ( ) 10 Convert the following binary numbers into decimal form : ) 10 (i) (0· llOl)z = ( (ii)(O·OOll)z = ( ho (iii) (0101011l)z = ( )10 Convert the following binary numbers into decimal form : )10 (i) (101 · lOl)z = ( (ii) (101-01 l)z = ( )10 (iii) (1010· 101l)z = ( )10 (iv) (111.lll)z = ( )10 Convert the following decimal numbers into binary numbers : )2 (i) (282) 10 = ( (ii) (111)10 = ( )z (iii) (5731)10 = ( )z Convert the following decimal numbers into. binary form : )z (i) (513·42)10 = ( (ii) (42·02)10 = ( h (iii) (26-73)10 = ( )z (iv) (10·375)10 = ( )z Convert the following octal numbers into decimal form : (i) (268)g = ( )10 (ii) (124)g = ( )10 (iii) (368)g = ( )10 (iv) (2039) 8 = ( )10 Convert the following octal numbers into decimal numbers : (i) (286-25)g = ( )10 (ii) (168·21) 8 = ( ho (iii) (2036-8235) 8 = ( ho (iv) (339·55)8 = ( )10

60

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

21. Convert the following decimal number into octal number : (i) (236)10 = ( )g (ii) (139)10 )g (iii) (750)10 = ( )g (iv) (145) 10 = ( )8 22. Convert the following decimal number into octal mumber : (i) (146·5)10 = ( )g (ii) (267 ·25)10 = ( )g (iii) (438·125)10 = ( )g (iv) (692·625) 10 = ( )g 23. Convert the following hexadecimal numbers into decimal form : )10 (i) (2CD3)16 = ( (ii) (14DA)i6 = ( )10 (iii) (39EB)16 = ( ho (iv) (ABCD)16 = ( )10 24. Convert the following hexadecimal numbers into decimal form : ho (i) (A2F.D)i6 = ( (ii) (ABC.2)16 = ( )10 (iii) (2AF.A)16 = ( )10 (iv) (20DB.lC)16 = ( )10 25. Convert the following decimal number into hexadecimal number : (i) (2310)10 = ( h6 (ii) (1234)10 = ( )16 (iii) (2468)10 = ( )16 (iv) (3521)10 = ( )16 26. Convert the following decimal numbers into hexadecimal numbers : (i) (465·5)10 = ( )16 (ii) (1046·25)10 = ( )16 (iii) (3465· 125)10 = ( )16 (iv) (4246·625)10 = ( )16 27. Convert the following binary numbers into octal form : (i) (110010l)i = ( )g (ii) (lllll)i = ( )g (iii) (1010l)i = ( )g (iv) (l01010l)i = ( )8 28. Convert the following octal numbers into binary numbers : (i) (432)g = ( h (ii) (1203)g = ( h (iii) (2405)8 = ( )z (iv) (1234) 8 = ( h 29. Convert the following hexadecimal numbers into binary form : (i) (2BCD)16 = ( h (ii) (A7DF)16 = ( h (iii) (ABCD)16 = ( )z (iv) (EIBF2) 16 = ( )z 30. Convert the following binary numbers in to hexadecimal numbers : )16 (i) (lll01100lll)z = ( (ii) (1101-llll)z = ( h6 (iii) (101011-lOl)z = ( )16 31. Convert the following octal numbers into hexadecimal numbers. (i) (143)8 = ( )16 (ii) (136)8 = ( )16 (iii) ( 112)s = ( h6 (iv) (58)s = ( )16

=· (

Chapter

Computer Arithmetic and Boolean Algebra Contents 4.1 4.1.1 4.1.2 4.1.3 4.1.4 4.1.5 4.2 4.2.1 4.2.2 4.3 4.3.1 4.3.2 4.4 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5 4.4.6 4.4.6.1 4.4.6.2 4.4.6.3 4.4.6.4 4.4.6.5 4.4.6.6 4.4.6.7 4.4.7 4.4.8 4.4.8.1 4.4.8.2 4.4.8.3 4.4.8.4

"'* Binary Arithmetic

,. ,.. 11• 11•

.

,

,

11• 11•

..

,

. .. ..... ,... . ....

11• ,

11•

, ,

11• , ,

, ,

11• ,

11• , ,

,... ,.,,.. 11• ,

..

,

Binary Addition Binary Subtraction Binary Subtraction by_ Addition Method Binary Multiplication Binary Division Octal Arithmetic Octal Addition Octal Subtraction Hexadecimal Arithmetic Hexadecimal Addition Hexadecimal Subtraction Boolean Algebra Definition Fundamental Theorem of Boolean Algebra Principles of Duality Boolean Functions Truth Table Canonical or Standard Form of a Boolean Function Disjunctive Normal Form (D.N.F.) Procedure of Conversion of a Function in D.N.F. Construction of a Boolean Function in D.N.F. from a Truth Table Conjunctive Normal Form Full Conjunctive Normal Form Complete Conjunctive Normal Form Construction of a Boolean Function in C.N.F. from a Truth Table Minterm and Maxterm Form of a Boolean Function Switching Circuits NOT Gate AND Gate NAND Gate OR Gate 61

4

62

4.4.8.S 4.4.8.6 4.4.8.7

4,4,9 4;4,10

-...

NOR Gate INCLUSIVE-OR Gate EXCLUSIVE-OR Gate Minimization of Boolean Function and Circuits Kamaugh Map (K-M) Method Exercises 1 Exercises 2

-• •

,,.

•

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Chapter

4

Computer Arithmetic and Boolean Algebra 4.1 Binary Arithmetic Binary arithmetic basically follows the same rules as the decimal system except that the binary system requires more frequent carry digits. Therefore, we can add, subtract, multiply and divide any two binary numbers by similar methods like that of decimal system. 4.1.1 Binary Addition In binary addition, the following rules apply Rule 1 ~ 0 + 0 = 0 Rule 2 ~ 0 + 1 = 1 Rule 3 ~ 1 + 0 = 1 Rule 4 ~ 1 + 1 = 0, with 1 carry over Example 1. Add 1001 2 and 0101 2 Solution. Binary 1001 + 0101

Decimal

910 510

1110

1410

Example 2. Add 110101 2 and 101111 2 Solution. 110101

+ 101111 1100100

Example 3. Add 0· 111 2 and 0· 102 Solution. 0·111

0·87510 0·510 l ·37510

+ 0·10 1·011 63

64

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Example 4. Add 11101.1101 2 and 10011.0011 2 Solution. 11111-111

Carry

+ . 11101·1101 10011·0011 110001 ·0000

~

Result

4.1.2 Binary Subtraction Binary subtraction is similar to decimal subtruction. In binary subtruction, the following rules are used : Rule 1 ~ 0 - 0 = 0 Rule 2 ~ 1 - 0 = 1 Rule 3 ~ 1 - 1 = 0 Rule 4 ~ 0 - 1 = 1, with 1 is borrowed from the previous coloum.

Example 1. Subtract (0110) 2 from (1101 2) to its left. Solution. Binary

Decimal

1001 0110

1310 610

1011

710

Example 2. Subtract 100102 from 110002 Solution. Binary

Decimal

11000 10010

2410 1810

110

610

Example 3. Subtract (100· 111)2 from (1001-101) 2 Solution. Binary

Decimal

1001-101 - 100·111

9·62510 4·87510

100·110

4·75010

Example 4. Subtract

101111 from 110101 2

Solution. 110101 - 101111 000110

COMPUTER ARITHMETIC AND BOOLEAN ALGEBRA

65

4.1.3 Binary Subtraction by Addition Method We can do binary subtraction by two additive methods, one is l's Complement method and the 2nd is 2's Complement Method. A. 1's Complement Method In this method, we have to convert the 2nd digit (which is subtracted) by l's complement. Then we add the converted digit with the first digit. If the carry number be 1, then the result will be positive (+) and is equal to the sum plus carry number. If the carry number is 0, then the result is negative (-) and is equal to l's complement of the sum.

Example 1. Subtract 11001 from llOlO using l's Complement Method. Solution. First Number : ll010 Keep as it is 2nd Number : 11001

Conver it , C as 1 s omp1ement

ll010 00110

+

UJ I00000 I .J,

.J,

Carry digit Sum Here carry digit is 1, so the required result will be the sum plus carry number. Hence the result is (sum + carry number) = 00000 + 1 = 00001 = 1

Example 2. Subtract 1101-11 from 10111·01 using l's Complement Method. Solution. First Number : 10111.01 Keep as it is 2nd Number : 1101.11 l'sComplement

0111.01

+

0010·00

[Q]

h1001 ·0ll

.J,

.J,

Carry digit

Sum

Here carry number is 0, so the required result will be the complement of the sum and also be a negative value. Hence the result is- OOlllO·lO, i.e., - 110·10

Example 3. Subtract 1000 from 1101 by l's Complement Method. Solution. First Number : 1101 Keep as it is 2nd Number : 1000 l's Complement

1101

+

011-1

Carry digit Sum l.T. App. in Business-5

66

INFORMATION TECHNOLOGY AND lfS APPLICATION IN BUSINESS

. . the result is Sum + Carry Number .. 0100 + I 0101 101

=

=

B. 2's Complement Method 2's Complement Method of a binary number is equal to the l's complement plus I, i.e., 2's Complement of 101 is (010+1) 011. In this method, we first find the sum of the first number with the 2's complement of 2nd number. If the carry number be I, then the sum part excluding the carry number, will be the result. If the carry number is 0, then the result will be 2's complement of the sum with a negative sign.

=

Example 1. Substract (11101-11) from (10111) by 2's Complement Method. Solution. First Number : 10111 Keep as it is

10111 ·0l

2nd Number : 11101-11 2's Complement [:. 00010·00 + I

+

00010·01

= 00010·01]

[Q]l11001·10 I j, j, Carry Digit Sum

Here carry number is 0, so the result will be 2's complement of the sum with a negative sign. Hence the result = - (00110·01 + 1) = - 00110· 10 = - 110· 10.

Example 2. Subtract (101100·001) from (110011-101), using 2's Complement Method. Solution. First Number: 110011-101 Keepasitis

110011 ·101

2nd Number : 101100·001 Z's Complement (010011-110+1)

+

= 010011-111

010011-111 []]1000111·1001

.1.

j,

Carry Digit Sum Here carry number is 1, so the result will be equal to the sum, excluding carry number, with positive sign. :. the result is 000111-100 111-100.

=

Example 3. Subtract (1010010) from (1110101) using 2's Complement Method. Solution. First Number : 11101 ·0l Keep as it is 2nd Number.: 10100100 2's Complement (0101101+1)

1110101 +

0101110

= 0101110

ill I 01000111 j,

j,

Carry digit Sum .. the result is 0100011

= 100011

COMPUTER ARITIIMETIC AND BOOLEAN ALGEBRA

67

4.1.4 Binary Multiplication

It is a form of repeated addition, and is carried out in the same manner as a regular multiplication with decimal numbers. The 0 x bx x 1 x

rules for binary multiplication are as follows 0 = 0 ~ rule 1 1 = 0 ~ rule 2 0 = 0 ~ rule 3 1 = 1 ~ rule 4

Example 1. Multiply (10110) 2 by (1001) 2 Solution.

10110 x 1001 10110 00000 x 00000 x 10110 x

~ ~

~ ~

Product Product Product Product

of of of of

1 x 10110

0 x 10110 0 x 10110 1 x 10110

11000110 ~ Sum of the Partial Product .. the result is (11000110) 2 Example 2. Multiply (11-10) 2 by (1·01) 2 Solution.

11·10 x 1·01

[ Similarly ]

1110 0000 x 1110 x 100·0110 .. the result is (100·0110) 2 Example 3. Multiply (ll ·001)2 by (11·1) 2 Solution.

11·001 x 11-1 11001 llOOlx llOOlx 1010·1111 .. the result is (1010·1111) 2

68

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

4.1.5 Binary Division It is a process of repeated subtraction. In binary it is carried out very much in the same manner as long division with decimals. The rules of binary division are as follows : 0 + l = 0 ~ rule 1 1 + 1 = 1 ~ rule 2 It is to note that 0 + 0 and 1 + 0 do not have any meaning.

Example 1. Divide (110011) 2 by (101) 2 Solution. 101 ) llOOll ( 1010 ~ Quotient 101 101 101 1 0 1 ~ Remainder. :. the quotient is 1010 and remainder is 1

Example 2. Divide (10001-11) 2 by (101-1) 2 Solution. (10001·111)2 (101·1)2

=

(10001111)2 (10110---'=--->~ Note that the input is indicated to the left of the diagram representing the logical circuit element and the output is indicated to the right.

80

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Input

Output

A

C =A'

0

1

1

0

Switching circuit is given below

4.4.8.2 AND Gate A circuit consisting of two or more switches connected in series known as AND switching circuit. It realises AND (·) function. The truth table is given below: Input

Output

a

b

0 0 1 1

0 1 0 1

c

= a-b 0 0 0 1

The truth table indicates that if a and b be the Boolean function representing the inputs, then the output c will be c = a.b. A logical symbol of AND gate is given below : a ______,,. b

D---c = a.b

AND gate may have two or more but finite number of inputs with only one output. The output signal is present iff all the input signals are present. Switching circuit of AND gate is given below I

4.4.8.3 NANO Gate

T

It is a combination of one NOT gate and one AND gate. A NAND gate gives an output 1, if any one of the inputs is 0 and an output 0, if all the inputs are 1. The truth table is given below : Input

Output

a

b

0 0 1 1

0 1 0 1

c

= (a.b) 1 1 1 0

This gate may have any finite number of inputs with only one output. A logical symbol is given below :

COMPUTER ARITHMETIC AND BOOLEAN ALGEBRA

81

The NANO gate is logically equivalent to the following combination a' b'

g' c

Here, c = (a.b . ... g)' = a' + b' + ... + g'.

4.4.8.4 OR Gate The circuit consisting of two or more switches connected in parallel is represented by OR gate. In a computer, an OR gate performs mixing functions where the output is present in all cases except when the input signals are all absent. An OR gate may have more than two inputs with only one output. If we have finite number of inputs, say a, b, c, ... d, then output x for an OR gate is given by x = a + b + c +... + l and the corresponding logical symbol is mentioned below :

_J __

D x = a + b + c + ... + I

l

>

::;.;

Switching circuit of OR gate is given below :

The truth table of two inputs is as follows :

a 0 0 1

Input

0 1 0

Output c 0 1 1

I

I

1

b

4.4.8.5 NOR Gate It performs the functions of an OR gate followed by an inverter. The output is absent except when all the inputs are absent. This gate may have any finite number of inputs with only one output. If we have finite number of inputs (say, a, b, c, ... ,l ), then output x for NOR gate is given by x = (a + b + c + ........ + l) = a~b~c~ .. l'. The truth table of two inputs is as follows :

Input

a 0 0 1 1 LT. App. in Business-6

Output b

c

0

1

1

0 0 0

0 I

82

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

The logical symbol of NOR gate is as follows :

---:--D

= a'b'c' ....

x

>

l'

The symbol is logically equivalent to the symbol mentioned below

___i _-D>----'C>>--x__ The switching circuit

i~ given below :

c:~~:-i 4.4.8.6 INCLUSIVE-OR Gate In this case, the output is present iff all the inputs are in the same state, i.e., either in 0 state or 1 state. The corresponding truth table of two inputs is given as under : Input

Output

a

b

0 0

0

l

l

1 1

0

0 0

1

1

c

Now, the function c in D.N.F. is c = ab + a'b' and in C.N.F. it is c = (a + b') (a'

+

b).

The logical symbol of Inclusive-OR Gate is c = ab + a'b'

>

The corresponding switching circuit is also given below

4.4.8.7 EXCLUSIVE-OR Gate This gate gives output I only when just one of the inputs is 1 and all other inputs are 0, and it gives no output, i.e., output 0 in all other combinations of the inputs. This gate may have a finite number of inputs with only one output. The truth table of two inputs is mentioned below : Input

Output

a

b

c

0 0

0

I

0 1 0

1

1

I

0 0

From the truth table, the Boolean function c in D.N.F. is c same in C.N.F. is c = (a + b) (a' + b'). The logical symbol of Exclusive-OR gate is a b

c = a'b + ab'

= a'b

+ ab' and the

83

COMPUTER ARITHMETIC AND BOOLEAN ALGEBRA

The following is the corresponding switching circuit :

~~~ L-2:~ Worked Out Problems : Prob. 1 : Realise AND gate by NAND gate. Sol. c = (ab) = {(ab)'}' The block diagram is

~

Prob. 2 : Realise OR by NAND gate. c

=a

+ b

b

Prob. 3

Prob. 4 Sol.

Realise AND by NOR. a

a'

b

b'

(a'+ b')' =ab

Realise (ac + bd) by only NAND gate. a

(ac)'

c

{(ac)'·(bd)'}

= ac

+ bd

(bd)'

b d

Prob. 5 : Realise the Exclusive OR gate due to inputs a and b by using basic logical gates. Sol. In D.N.F., c = a'b + ab'. c >

Prob. 6 : Design a switching circuit and block diagram that can function a lamp on or off from three different locations independently. Sol. If two switches are on and three switches are off simultaneously, then the lamp is off, otherwise the lamp is on. The truth table is as under :

Inputs a 0 0 0 0 1 1 1 I

. . the function

b 0 0 1 1 0 0 1 1

f in D.N.F. is f

Outputs c 0 1 0 1 0 1 0 1

= x)i'z

f 0 1 1 0 1 0 0 1

...

x'y'z. x'yz'

. ....

xy'z'

..

xyz

~

+ xyz' + xy'z' + xyz

... (1)

84

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

For expression (1), the block diagram is given below : x-~--~

f

Equivalent switching circuit is as under : ___/__/

~Lz /~_G z'

_0£ x

y

z'

z

4.4.9 Minimization of Boolean Function and Circuits In designing and switching a computer circuit an objective is to minimize the total number of elements or switches used in the circuits. The minimization of the Boolean function minimizes the switches used in circuits. For example, f = ab'c + a'c + abc can be reduced into f = ac (b' + b) + a'c = ac + a'c = (a + a') c = c. This method of reduction and minimization ·of a Boolean function may be called a method of algebraic simplification using the Joss of Boolean variables. However, this method is rather uncertain and may not be systematic method of minimization of Boolean function.

4.4.10 Karnaugh Map (K-M) Method The first method of minimization of Boolean function generally used in a graphical method is known as the method of Kamaugh Map Method. This map method was introduced by E.W. Veitch and was modified to its present form by M. Kamaugh. Kmap method is easy to apply usually for Boolean functions for four or Jess variable. The K-map is essentially a Venn diagram arranged in more useable form and it is made by numbers of squares within a rectangle. Each square represents a minterm of the corresponding truth table. Thus for fucntions of two variables, it will have four squares. The functions of three variables will have eight squares. The functions of four variables will have sixteen squares and so on. The K-map for three variables is non-trivial ;md we will consider it first as under

c c

ab

ab

ab

ab

mo ml

m2 m3

m6 m7

m4 ms

We shall use the basic principle to simplify Boolean expression using K-map of four variables consisting of 16 squares as below ab ab ab ab c-+-JV

>------~

[Ans.

f =

ab' (a + b) b]

(v)

[Ans.

f = x' (y' +

z') + xzy]

88

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

17. Write down the Boolean functions of the following circuits : (a)

xx2~~~ f =

[Ans.

{xz

+ x(y + z')).(x + z)]

(b)

[Ans. (c)

:,====: ~~~~~-z-

f =

(x

+

y).(x'

+ y)]

-----1-.h/

-_----

y'---

z -------~[Ans.

f

= xyz + x'z + y'z]

(d)

[Ans.

f

= (x + z)y + y(yw + w)]

[§3G3G3EBp [Ans. 18. 19. 20. 21.

f

= (x

+ y + z). (x + y + z'). (x + y' + z). (x + y' + z')]

Draw a block diagram to realise the two input OR function using only NOR gates. Draw a block diagram to realise the two input OR funciton using only NAND gates. Draw a block diagram to realise the two input AND function using only NAND gates. Minimize the following Boolean functions by K-map method (a) f (a, b, c) = L,(O, 3, 7) (b) f (a, b, c) = L,(3, 4, 5) (c) f (a, b) = L,(O, 2) (d) f (a, b) = L,(l, 2) (e) f (a, b) = L,(2, 3) (f) f (a, b, c) = L, ( 2, 4, 5, 7) (g) f (a, b, c, d) = L, (2, 3, 14, 15) (h) f (a, b, c, d) = L, (4, 5, 6, 7, 8) (i) f (a, b, c, d) = L, (0, 3, 8, 10)

Chapter

Computer Processing System

5.0

.... ,,,. ... ... ... ..... ...

Contents

,,

Introduction Hardware 5.1 5.1.1 ,,,,. CPU (Central Processing Unit) 5.1.2 Three Components of CPU 5.1.2.1 ,, Control Unit 5.1.2.2 ,, Sequence of Control Unit 5.1.2.3 ,, Important Function of Control Unit 5.1.2.4 ,, Arithmetic Logic Unit (ALU) 5.1.2.5 ,, Important Functions of ALU 5.1.2.6 ,, Primary Storage Unit or Main Memory 5.1.2.7 ,, Important Features of the Main Memory 5.2 ,, Software 5.2.1 ,, System Software 5.2.2 Ill. . Application Software 5.2.3 ,, Peopleware 5.3 ,, Program Language 5.3.1 ,, Low Level Language 5.3.1.1 ,, Machine Language 5.3.1.2 ,, Assembly Language 5.3.2 ,, High Level Language 5.3.2.1 !I. . General Purpose Language 5.3.2.2 ,, Special Purpose Language 5.3.3 ,, Compiler 5.3.4 Interpreter 5.4 Comparison between Interpreter and Compiler 5.5 ,,,. Comparison between High Level Language and Assembly Language 5.6 111• Some High Level Languages 5.7 Generation of Computers 5.7.1 First Generation of Computers 5. 7.2 Second Generation Computers 5.7.3 ,,,. Third. Generation Computers 5.7.4 · Fourth Generation Computers 1971-till date 5.7.5 Fifth Genaration Computers 5.8 Computer Generation-at a Glance ,,

.. ... ..

,,,. 11

11

11

•

•

•

11

•

1 •

11

11

•

•

89

5

90

.. ...

5.9 , 5.9.1 ,,.. 5.9.2 , 5.9.3 ,, 5.9.4 ,,.. 5.9.5 ,,.. 5.9.6 ,,.. 5.9.7 ,,.. 5.9.8 , 5.9.9 ,,.. 5.10 ,,..

..

•

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Types of Computers Digital Computers Analog Computers Hybrid Computers Comparison between Analog and Digital Computers Mainframe Computers Minicomputers Microcomputers Personal Computers Portable (:omputers Functions of Digital Computers Exercises

Chapter

5.

Computer Process·ing System 5.0 Introduction Computer is a term applied to a group of inter-related electronic devices that automatically. * accept and store data (input) * process the same (input) * output the processed results in the form of alpha numeric reports, statistics or graphics. The basic configuration of a computer system is given in the following figure

I

Input Unit

Processing Unit

Output Unit

Memory

Data processing activities are carried out by the computer through a sequence of pre-written instructions to provide the requisite output. The sequence of instructions is also referred to as program for resolving a particular type of data processing activities, both the data and the relevant sequence of processing instructions first need to be converted into electronic form and then stored in the computer's memory before they can start interacting with each other. Thus a computer output is the processing result of combined software and hardware systems.

5.1 Hardware Physical components of a computer system are known as the Computer Hardware. When we look at a computer system we are actually looking at the computer hardware. The Configuration of various computer hardwares may be designed as follows :

Hardware

+

CPU (Central Processing Unit)

•

Control Unit (CU)

i

+

ALU (Arithmetic & Logic Unit)

.

Main Memory (Primary Storage Devices) 91

•

Input Devices

Output Devices

•

Auxiliary Storage Devices

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INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

5.1.1 CPU (Central Processing Unit) The equipment that carries out the processing function is known as the Central Processing Unit (CPU) of the computer. The central processing unit which is also known as the processor, is the heart, soul and brain of a computer. In a Micro Computer, the entire CPU is contained in a tiny chip, called a microprocessor. It is the most important component on the system's monitor board. The rest (dcepting data communication devices) are collectively known as Computer peripherals. Data Communication devices, which sometimes are attached to and used with some computers, are called as special purpose peripherals. The peripherals are connected to the CPU and simultaneously function under the control of the CPU by means of a device known as data channel.

5.1.2 Three Components of CPU The three components of Central processing Unit (CPU) are (1) The Control Unit. (2) The Arithmetic and Logic Unit. (ALU). (3) The Primary Storage Unit. (or Main Memory Unit)

5.1.2.1 Control Unit It controls coordinates and supervices all the operations of a CPU (Central Processing Unit) and monitors the execution of any program processed. As human brain directs all the actions of the body, the control unit coordinates and controls the activities of the different components of a computer system. Its main function is to identify and interpret instructions and to send appropriate signals to other components in the computer for their sequence of executions. The control unit exists in the CPU as a nerve centre of a computer system. It directs the Arithmetic Logic Unit, Input and Output Devices and Storage Section sending proper instructions for sequence of execution of any program. When program starts an input operation, the control unit identifies the input devices and hence sets up electronic data path for the data instructions to enter the CPU. Thus the control unit executes the various operations in CPU in the desired manner. It is the logical hub of the computer.

5.1.2.2 Sequence of Control Unit Supervision, coordination and execution of all the operations are done by the control unit in a sequential manner a.s follows : (1) Execution for a particular instruction is restricted from main memory into the storage register. (2) The instruction is passed from storage register to instruction register. (3) Then the operation part of the instruction is decoded through arithmetic and logical section. (4) Then Instruction Register transfers the operation part of the data to Address Register for their proper exemption. The sequence of control unit operations may be arranged in the following diagram (Fig. 5:1): ALU

Main Memory

Storage Register

Instruction Register Memory Address Register

Decoder Fig. 5.1. Control Unit Operations

COMPUTER PROCESSING SYSTEM

93

The time required to move an instruction from the main memory to the control unit and its decoding is called the instruction time. When the instructions of a particular program are executed by the ALU (Arithmetic Logic Unit), at takes a few seconds, called execution time. 5.1.2.3 Important Function of Control Unit The most important function of a control umt m a CPU are* Coordination and control of various parts of the computer system. * Transfer of data to and from the working storage areas. * Retrieving and decoding program instructions from the internal storage. * Monitoring sequence of instructions for execution. * Connecting the appropriate ciruits to enable the Arithmetic Logic Unit for processing data. * Fast and Automatic repetition of each instruction cycle of operations. * Identification of the subsequent program instruction of the CPU memory. 5.1.2.4 Arithmetic Logic Unit (ALU) This unit of the CPU performs mathematical calculations, compares numeric and nonnumeric values and makes decisions. This unit contains a large number of electronic circuits which help to carry out a variety of arithmetic and logic function under the direction and command of the control unit. There are three main components of the ALU (Arithmatic Logic Unit) : (i) Mathematical gates (ii) Logic gates (iii) Registers (i) Mathematical gates : Math-gates performs basic calculations, i.e., addition, subtraction, multiplication and division of data item. (ii) Logic gates : Logic gates perform comparisons of two data items, say, A & B. The result of a comparison can only be three, i.e., * A is equal to B (A = B) * A is greater than B (A > B) * A is Jess than B (A < B) (iii) Registers : Registers are areas of high speed storage circuitry used as 'work area' for the temporary storage of instructions and data during the operation of the control and arithmetic logic units. The number, functions and capacity of the registers and other sub-units in CPU depends on the internal architecture of each computer. 5.1.2.5 Important functions of ALU Arithmetic logic unit of the CPU performs several important functions as follows : * Basic mathematical calculations. * Comparison of numeric and non-numeric values (data). * Determining the ascending or descending sequence of data. * Sorting and summarisation of data. * Logical transfer of data from one register to another. * Helping users indirectly to take decisions. 5.1.2.6 Primary Storage Unit or Main Memory Main or primary storage is usually a physical part of the CPU and is directly controlled by control unit of the computer. This memory is also referred to as Immediate Access

94

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

storage or core memory. A primary storage is basic to all computer systems. It consists of several storage areas, called locations or cells. Each location or cell holds of single data item. Each location or cell stores a fixed number of bits expressed as word length. Again each location has an address which is used to designate that location for the purpose of storing data in it or retrieving data from it. The volume of information that can be held in the main memory is known as Memory Capacity. The capacity of the memory is measured in kilobytes (Kb) or megabytes (Mb). One kilobyte stands for 2 10 bytes = 1024 bytes and a megabyte stands for 220 bytes, which is approximately one million bytes. Thus the storage capacity of a computer system is expressed in term of bytes or words, e.g., 64 Kb or 64 kilobytes which is equal to 64 x 1024 = 65536 bytes. However, the actual storage size can be determined only after knowing the word size in bits or bytes. For example, A 16k 16-bit memory wili mean a word size of 16 bits and 16 x 1024 = 16384 words. If the memory capacity is considered as, suppose, 64 K, it is generally implied that the word size is 8 bits (equal to l byte). Basically computers may be with 8-bit, 16-bit, 32-bit, etc. word size. More bits enable more rapid flow of electronic signals and faster computer speed. Where data are retrieved from a storage location, they are called non-destructive and while storing new data into a location, they are called destructive. The main memory of a computer may be designed as fixed word length storage and variable word length storage. When it is designed to store a fixed number of characters or bytes (equal to its word length) in each numbered address location, called fixed word length storage. For example, if the word length is of 4 characters or bytes, allocation of strong space will be done in multiple number of word-length or 4-character block. Thus the words POLICE, PUBLIC, KOLKATA and DELHI will require 2 words or 8 bytes each, although their sizes are 6, 6, 7 and 5 characters respectively. When the storage in memory is designed to store only a single character or byte in each numbered address, the computer is said to be character address length storage. For example, the words POLICE, PUBLIC, KOLKATA and DELHI will require exactly 6, 6, 7 and 5 bytes or characters of storage area. The fixed word length storage has the advantages of faster calculation as may be necessary for scientific applications, white variable word length storage may be necessary for small business applications with limited volume of data. 5.1.2.7 Important Features of the Main Memory

The following are the significant characteristics of the main memory : l. Fast access : The CPU can transfer a data item to or from main memory in less than a billionth of a second. A typical access time is one-sixth of a billionth of a second. 2. Random Access : Access to data stored in the main memory is instant and random. The storing is regardless of the order in which the items are stored in memory. 3. Moderate Capacity : Small computers have main memory capac1t1es ranging from 640 Kb to 8 Mb Large computers may have main memory capacities of megabyte or gigabyte. 4. Expensive : This type of memory is more expensive than secondary or auxiliary memory. 5. Volatility : This type of memory is volatile. The stored data in such memory is lost when electric power is turned off.

95

COMPUTER PROCESSING SYSTEM

5.2 Software It can be defined as a program which comprises of a set of operating information or instructions written in a computer language by professionals known as programmers. In other words, the associate rules, procedures and documentations are together referred to as software. Thus the automatic programming techniques and procedures for utilising the capabilities of the computer are called software. The computer machines are incapable of performing any job or function unless associated with its proper procedures and programs. The ability of the user is then dependent on software which is partly supplied by the manufactures and partly is written by the user as his own programs or modified by him according to his needs. The basic configuration of computer software may be designed as follows (Fig. 5.2) : SOFTWARE

i l i

Application

l

Systems

People-ware

Programi Languages

J

Low Level

J

i

Machine

Systemi Utilities

l i

High Level

l

Assembly

Genera~ porpose

J

Compiler

J

COBOL

Loader

l

Monitor

l

Debugger

l

Spelal purpose

l i

Interpreter

i Fortran

l

Operating System

Basic

l

Pascal

Fig. 5.2. Software Configuration for Computers

5.2.1 System Software It comprises of those programs that control and support the computer system and data processing activities. Thus system software refers to all the programs which make the computer workable and is commonly supplied by computer manufactures or computer vendor and comprises a large number of instructions which are specific to the hardware devise of a particular computer system. Workable system software includes the following:

96

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

(i) Assemblers and Compilers : These are for translating the programs from source codes to the object codes. (ii) Diagnostic Routines : These are supplied by the computer manufacturers and capable to assisting program debugging. (iii) Utility Programs : These are also supplied by the computer manufactures and capable of performing the following functions : (a) sorting (b) editing (c) dumping of data, etc. (iv) Supervisory Programs : It is also called operating system which optimises man machine capabilities. (v) Library Sub-routines : A sub-routine is a subject of instructions that appears repetitively in the same program or different programs.

5.2.2 Application Software It is a complete suite of application programs together with associated documentation. It covers business routines and is usually supplied by a computer manufacturer or software house on lease or purchase. The application software is usually constructed to cater the needs of different users. Typical application softwares are stock control, payroll, A/c receivable, production control, PERT (Program Evaluation Review Technique) linear programming, etc. Thus application software refers to the program of instructions suited for proper hardware functions in a desired way for processing an application, unique to a user. An application software is also called user software. It is a kind of packaged software. Like readymade garments such software can be used to fit the requirement. The main advantages of such software are ready availability and reasonable cost. However, this types of software are sometimes difficult to make to meet certain specific rquirements of the users upon modification. 5.2.3 Peopleware Peopleware includes all the people connected with the development of computers or its components, maintenance or operation of computers. Basically three types of personnel mentioned below are engaged in the computer installation and its operation. (a) System Analysts : They study data processing requirements, design the flow of operations and prepare specifications for the processing system. (b) Programmers : They develop computer programs in accordance with the specifications prepared by the system analysts. (c) Computer Operators : They operate the computer system and communicate with the computer by a device consisting of mouse, switches, keyboard and screen termed as Console.

5.3 Program Language A program is a list of instructions or statements for directing the computer to perform a required data processing task. There are various types of programming languages that one may write for a computer, but the computer can execute programs only when they are represented internally in binary form. Thus the computer can carry out only those instructions which are presented in the form of binary signals O's and ls. The application programs are written in an English-like languages such as COBOL, BASIC, etc. These need to be translated into machine-executable form, i.e., in binary signals. All computer languages can be classified in the following broad categories. (i) Low Level Language. (ii) High Level Language.

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5.3.1 Low Level Language A language in which instructions are directly translated into an individual machine coded form is called low level language. This language basically written as sources programe and later converted into object program. Low level languages are of two types : (a) Machine Languages. (b) Assembly Language. 5.3.1.1 Machine Language Strictly speaking, a machine language program is a binary program. The language whose design is implemented by the circuit and the structure of the machine is called machine language. It consists of a set of instruction codes in a tune format, viz., operation (code) and operand (Address). As the machine code is represented in binary digits the programmers first have to write in binary format which is a very complex and tedious task. Advantages of Machine Language : Advantages include1. Storage Capability : Machine languages make efficient use of storage language instructions. 2. Very Fast : Instructions of a Machine Language Program are quickly executed. 3. Manipulation : Machine Language instructions may be used to modify/adjust the bits in a byte of computer storage. 4. Translation : Machine language does not require translation. Disadvantages of Machine Language : Disadvantages include1. Machine oriented : Machine languages are machine dependent. 2. Skill dependent : This language needs a high level programming skill. 3. Complexity : If there is any error in programming under this language, it is quite difficult to justify. 4. Time-consuming : For development of a programs under this language, it takes much time. 5. Rigidity : Though easily used by the computer, this language is very difficult to implement a program. 5.3.1.2 Assembly Language The assembly language is an improvement over the Machine Language. A low level programming language which substitutes letters and symbols for the numbers in the machine language program is called an assembly language. This language lies between high level language and machine language. A symbolic program written by a programmer in assembly language is called a source program. Source program after being converted into machine language by an assemble is called an object program. Advantages of Assembly Language : (i) This language programs are easier to understand and use. (ii) This language programs are easier for the people to modify, alter and delete. (iii) Assembly language is not required to keep the track of memory location. (iv) Insertions and deletions are quite easy for such languages. (v) Revision of complete program is quite easy. Disadvantages of Assembly Language : (i) This language is machine language. (ii) Programs made in such languages cannot be executed on small sized computers. l.T. App. in Business-7

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(iii) Programming in such language is time-consuming and complicated. (iv) This language depends on a number of instructions unlike high level language. (v) This language is machine dependent.

5.3.2 High Level Language These are the special languages developed to represent the procedures used in the solution of a problem. It involves problem oriented symbols and formats. These languages are machine independent. High level languages are very similar to the languages normally used by us in other day-to-day life. programs written in high level languages are easier. to maintain. This languages are of two types. (a) General purpose language. (b) Special purpose language. 5.3.2.1 General Purpose Language These languages are designed to help problem formulation in a manner which is as similar to the basic problem formulation as possible with a computer translation into machine language. These are supposed to be independent of the machine. Two types of problem that can be formulated generally are business and scientific purposes oriented. 5.3.2.2 Special Purpose Language These are designed for a more narrow area than general purpose language. Basically this type of language is highly independent of the computer. Execution of a particular program upon such language is very complex. 5.3.3 Compiler The compiler is specific to each brand of computers. The compiler translates the source code to object code. The object code is then saved on a strorage device and run on the basis of need. It is a standard program written and supplied by the computer manufacturers for translating the program written in a high level language into the equivalent machine code of computer. Examples of the languages needing a compiler include COBOL and FORTRAN. The translation process of a compiler is as below (Fig. 5.3) : High Level Language :: Program

Input

Compiler

Output

--~~-____,~.

Machine Language program

Source C o d e - - - - - - - - - - - - - - - - - _ _ _ _ , • Object Code

Fig. 5.3. Translation Process of a Computer

Functions of Compiler : Most important functions of the Compiler are stated below : ( 1) Allocation of space in storage location for the program execution. (2) Reading each line of the source program and conversion into machine language. (3) Generation for appropriate sub-routines from library. (4) Identification of the sequence of processing. (5) Identification of various errors in a source program, e.g., illegal characters, illegal combination of charactares and improper sequence of instructions.

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5.3.4 Interpreter An Interpreter translates at a time one statement of the source code into object code just before it is executed. It is another type of translator used for translating high level languages into machine code. It takes one statement of a high level language and translates it into a machine language which is immediately executed. An example of a language often using an interpreter is BASIC and PASCAL, etc. The translation process of an interpreter is as below (Fig. 5.4) : High Level Language Program

Input

1 1------''-----.i~

Source code

1

I nterpreter

1 ~ 1-----=----~~

1

Output

One statement at a time

--------------------•~

Machine L anguage program

Object Code

Translation Fig. 5.4. Translation Process of Intepreter

Functions of Interpreter : Most important functions of interpreter may be pointed out as follows (1) They are easier to develop and useful for interactive programming. (2) It helps to translate a program line by line. (3) It takes more identification of errors in a source program. (4) Since its execution time is more, the process eliminates all errors finally.

5.4 Comparison between Interpreter and Compiler Interpreter 1. It requires less memory location. 2. It takes one statement in the program for translation. 3. The interpreter and the source program both together require for execution. 4. It takes more time for execution. 5. No security of source code is maintained. 6. It takes fast debugging process in the program.

Compiler I. It requires more memory location. 2. It takes entire program for translation. 3. Neither compiler nor the source program require for execution. 4. It takes less time for execution. 5. Security of source code is maintained. 6. It takes slow debugging process in the program.

5.5 Comparison between High Level Language and Assembly Language High Level Language

Assembly Language

1. It is very easy to realise. 2. This language is problem oriented. 3. This language takes less time to remove errors in program. 4. Execution of a program by this language is very slow. 5. This language is written using English language. 6. Writing programs in such language makes possibility of fewer errors.

I. It is very complex to realize. 2. This Language is machine oriented. 3. This language takes more time to remove errors in program. 4. Execution of a program by this language is very fast. 5. This language is written using symbolic codes. 6. Writing programs in such language makes possibility of much errors.

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5.6 Some High Level Languages Among hundred high level programming languages developed so for, the most commonly used of such languages are referred below : 1. BASIC (Beginners All-purpose Symbolic Instruction Code) : It is widely used in PCs and is suited to the programmers-both the beginner and the experienced. This language is interactive. 2. COBOL (Common Business Oriented Language) : It is most commonly used in business applications. It is a compiler language. The COBOL program is divided into four divisions-(i) identification division (ii) environment division (iii) data division (iv) procedure division. 3. PASCAL : It is widely used in PCs and is easy to learn. It is particularly popular in computer service educational programs. Its distinctive feature is structured coding, i.e., the sequence, selection and looping. 4. FORTRAN (Formula Translation) : This language is widely used for solving scientific, engineering and mathematical problems. 5. 'C'-Language : This is a general purpose language which is used both in larger and personal computers. It is also useful for writing operating system database programs and some scientific applications. 6. 'C++' Language : It is the extension of the C-programming and is known as object oriented language. 7. RPG (Report Program Generator) : It is a high-level commercial programming language. The language is suited to preparation of business reports. A user does not have to be concerned with solution procedure, rather he has to concern himself with inputs and outputs. User can learn it easily. 8. ALGOL (ALGOrithmic Language) : It is a high-level programming language. intended for use in scientific and mathematical programs. 9. PROLOG (Programming and Logic) : It is also a high-level computer programming language devised for artificial intelligence application by the Japanese as the standard language for their fifth generation Computer Project.

5.7 Generation of Computers Man has been in search of devices which could help him in reducing his physical efforts. A need was felt for such a device which could reduce the burden of performing the mathematical operations like addition, subtraction, multiplication and division. The lack of technological development prevented the early invention of computers. But after the development of electronic devices in the advanced countries, the first major step was taken by George Boole for the invention of the algebra of logic (called Boolean Algebra) in the United States. Depending on the logic of such algebra in 1937, Prof. H.G. Aiken of Harvard University designed a machine unit that would automatically perform a sequence of arithmetic operations. Thereafter, the first electronic computer ENIAC (Electronic Numeric Integrator and Calculator) was designed by Prof. J. P. Eckert and Prof. John W. Mauchly of the Moore School of Engineering of the University of Pennsylvania and was completed in 1945. Probably the commercial computer in United Kindom was completed in 1951 by Ferranti Ltd. in association with Manchester University. Therefore, the evolution of the modern computer can be viewed in specific 'generation' which starting from early forties cover up to 4 generations to date and we are in the middle of the 5th generation today. Each generation was an improvement over the former in terms of technology, speed, storage capacity, size, reliability and cost.

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5.7.1 First Generation Computers (1951-58) The first computers that came in the market namely EDVAC, UNIVAC, IBM 701, IBM 650, etc. are offen referred to as the first generation computers. The computers generally using vacuum tubes were large in size, required much air conditioning, had little internal storage capacity and were relatively slow. They used magnetic drum or tube, for secondary storage and purchased cards as input and output media. They could be programmed only in machine language. Most important features of fifth generation computers are described below : l. Use of vacuum tubes in electronic units as major components. 2. The memory capacity of such first generation computers and 10000 to 20000 characters. 3. Internal operating speed of such computers are expressed in milli seconds. 4. Central memory of such computers was built with mercury delay lines Cathode Ray Tube, magnetic drums and core memory. 5. The peripherals of such computers are punched card, paper tape, magnetic drum, Magnetic disks etc. 6. Operating system of such computers are mainly for batch processing. 7. Machine code and electric wired boards are used as program language. 8. First generation computers are of very large size and weight. 5.7.2 Second Generation Computers (1959-65) The second generation computers used transistors as main component instead of vacuum tube of earlier generation for the CPU, and used magnetic cores for memory. These computers were the first to be used for commercial data processing. A transistor performs the same functions as a vacuum tube does and is much smaller and less expensive, generates little heat and consumes less power. Thus the size of computers were reduced. Data were entered into these computers largely by means of purchased cards machines. The second generation computers did acquire interactive computational capability through a terminal and supported the earlier versions of high level language like COBOL, FORTRAN, etc. Computers like IBM-1401, IBM-1620 and IBM-7094 are the example of this generation. Most important features of second generations are stated below : 1. Use of transistors and diodes for internal operations as major components. 2. The memory capacity of such second generation computers are 4000 to 64000 characters. 3. Internal operating speed of such computers are expressed in micro seconds. 4. Central memory of such computers was built with magnetic core, paper/magnetic tape memory. 5. The peripherals of such computers are paper/magnetic tape and usual display units. 6. Operating system of such computers are mainly for multiprogramming, time sharing and real time processing. 7. Assembly language and high level languages are used as programming language like FORTRAN & COBOL. 8. Second generation computers are less in size than the first generation computers. 5.7.3 Third Generation Computers (1965-1970) In the third generation computers they improved on this and put the integrated circuits instead of transistors. The components were mounted on a printed circuit board and in case of failure of it, this board was removed and replaced by another PCB (Printed Circuit Board). These computers had main memory of several megabytes along with processing

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speeds of millions of instruction per second. The third generation computer functioned in a multi-programming environment. They supported high level programming languages like FORTARN-11, COBOL, BASIC, ALGOL-68, etc. Third generation computers had also the capability of using online development of computer application software and telecommunication facilities. Examples of such computers are IBM-350, UNIVAC-1108, CDC-6600; HONEYWELL-200, etc. Most important features of third generation computers are1. Use of Integrated Circuits (ICs) for internal operation as major components. 2. The memory capacity of such third generation computers are 32000 to million characters. 3. Internal operating speed of such computers are expressed in nano seconds 00-9 seconds). 4. Central memory of such computers was built with magnetic core and solid state main storage devices. 5. The peripherals of such computers are teletype writer terminals, Visual Display Units (VDU), Optical Character Recognition (OCR) devices, and Magnetic Character recognition (MCR) devices, etc. 6. Operating system of such computers are mainly for remote processing, time sharing, real time processing and multi programming, etc. 7. High-level languages are used as programming language, viz., FORTRAN-II to IV, COBOL, BASIC and ALGOL-68, etc. 8. Third generation computers are smaller and faster.

5.7.4 Fourth Generation Computers (1971-till date) The fourth generation computers, rendering further upgradation of the third generation computers, implemented Very Large Scale Integration (VLSI) of circuits by means of advanced microtechnology which made possible extremely large internal and external storage capacities together with virtual memory. Many new types of terminals, development of extensive computer network and means of computer access were also developed at that time. Distributed data processing evolved farther in the fourth generation with the development of system software. Example of 4th generation computers are IBM 370 series; ICL 2900 series; CDC Cyber 170 Range, etc. Most important features of the fourth generation computers are given as under : I. Use of large-scale Integrated Circuits for internal operation as major components. 2. The memory capacity of such fourth generation computers and 51200 to 32 million characters. 3. Internal operating speed of such computers are expressed in pico seconds (l0- 12 seconds). 4. Control Memory of such computers was built with magnetic core and solid state main storage device. 5. The peripherals of such computers are VDU, OCR, MICR, floppy & hard disk. 6. Operating system of such computers are mainly for time sharing, real time, network and distributed data processing. 7. All the highlevel languages, fourth generation language, DBASE, etc. (with concept of artificial intelligence) are used in programming language. 8. Fourth generation computers are small, inexpensive and greatly improved data communication system.

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5.7.5 Fifth Generation Computers The fifth generation computers will be employing two or more processors which compute in parallel. The architecture of the fifth generation computer conceptually differs from the architecture of the first four generations of computers. These computers will be used for computer and microelectronic designer to manufacture more powerful machines with Artificial Intelligence (Al). The architecture of the fifth generation computers is referred to as data flow architecture. The basic idea of data flow concept is direct communication between the processors and memories. The countries, presently in the forefront of the race for the fifth generation computers, are USA and Japan. The technology for fifth generation computers ·is basically advanced architecture, advanced software engineering, VLSI, artificial intelligence and expert system.

5.8 Computer Generations-at a Glance Four computer generations as defined above may be shown in the following table :

Table 5.1 : Computer Generations Generation

First Generation

Technology

Advantages

Used mainly for batch processing

Valves & 20000 vacmn tube characters

Second Generation Transistor

Third Generation

Max. Memory Capacity

64000 characters

Integrated 4 Million Circuits (IC) characters

Fourth Generation Large scale 32 million Integrated characters Circuits (LSIC)

(i) Higher level of accuracy (ii) Reliable (iii) Larger storage capacity (iv) Low rate of machine failure

Disadvantages

(i) Very large and expensive (ii) Relatively slow (iii) Generates lot of heat (iv) Not reliable (i) Relatively slow (ii) Expensive (iii) Generates heat

(i) (ii) (iii) (iv)

Smaller in size More reliable Much faster Less power consumption (v) Low machine failure rate (vi) Executes Multi programs (vii) Less mainteance cost.

(i) Requires air conditioning (ii) Expensive

(i) Portable & sophisticated (ii) Introduces microprocessors (iii) More reliable (iv) Using data communication system (v) Using secondary storage (vi) Small & inexpensive

(i) Complex software (ii) Requires sound operating knowledge (iii) Increases managerial egoes;

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INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

5.9 Types of Computers Computers can be classified in two ways (a) By functional criteria (b) By capacity and performance criteria. Functional Criteria : By functional criteria computers may be classified in categories as under : Computers

i Digital

Analog

i Hybrid

5.9.1 Digital Computers These computers carry out computations on data represented in the form of numbers, alphabetical characters and symbols. Digital computers have the capabilities of adding, subtracting, multiplying, dividing and comparing. These computers provide highly accurate results. Any degree of accuracy can be achieved by calculating additional decimal place to the right side of the decimal points. Such computers are ideally suited for business data processing. Most important features of digital computer are stated as under 1. It operates directly on decimal digits. 2. It has a capability of arithmetical and logical operations. 3. It is very accurate. 4. It is multipurpose oriented. 5. It is suited for scientific and commercial use.

5.9.2 Analog Computers Analog computers do not operate on digital data. Instead they operate on data presented to them in the form of continuously variable quantities like pressure, temperature, revolutions, water of law, etc. and react in a pre-determined way to changes in the specified quantities. They are so called, as they have the capability of drawing on analogy to the data being presented to them directly from the measuring instruments. Thus the capabilities enable them to immediately respond to influence the ongoing operations. This mode of working is referred to as real time in computer terminology. Most important features of Analog Computers are given below : 1. It operates on physical quantities. 2. It performs very complex arithmetical functions. 3. Storage capacity of such computers is relatively high. 4. Such computers are generally accurate up to 0· 1 percent of the correct value. 5. These computers are suitable for use as controlling devices. 5.9.3 Hybrid Computers Such computers are combination of the capabilities of both digital and analog computers. They are suitable where digital processing is necessary in respect of data collected in the analog form. For example, in the intensive careunit of a hospital a patient's heart function, temperature, etc. may be measured and other vital tests may be performed by analog devices. These measurements may then be converted into numbers and supplied to digital devices which may send an immediate signal to a healing process if there is any abnormal identification are detected.

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Most important features of Hybrid Computer are stated below I. It has a combined capability of both the digital and analog computer. 2. It is suitable for digital processing. 3. Such computers are highly sensitive and reliable. 5.9.4 Comparision between Analog and Digital Computers Analog Computers

Digital Computers

I. It operates on physical quantities. 2. It measures. 3. Its storage capacity is relatively high. 4. Its accuracy is low. 5. Such computers are suitable as a controlling device. 6. It is of low cost. 7. These computers are used for single purpose.

I. It operates on numbers. 2. It counts. 3. Its storage capacity is relatively low. 4. Its accuracy is high. 5. Such computers are suitable for scientific and commercial use. 6. It is of high cost. 7. These computers are used for multipurpose.

Capacity and Performance Criteria : On the basis of capacity and performance criteria, computers may be classified on under : Computers

i

Mainframe computers

i. Medium Scale computer

i

Minicomputers

i

Microcomputers

~

i Large Scale computer

Supercomputers

Personal computers

i Protable computer

5.9.5 Mainframe Computers It is large and costly computers characterised by large size words and large capacity. Such type of computers are used for scientific and business applications of large dimensions. The main disadvantage of such computers is these are highly expensive and affordable only to the big business hours, government and scientific bodies.

Generally mainframe computers are of three types as below. : (i) Medium Scale Mainframe Computers : These computers are useally used in large business environment. These are basically characterised by third generation computers. (ii) Large Scale Mainframe Computers : These computers are usually used in airline reservation system. Widespread banking networks and insurance companies, etc. (iii) Supercomputers : These are very large computers with multiple CPUs and parallel processing features. These computers are capable of executing mulpple instruction per second. Basically these computers are used for weather forecasting, space research programs, defence needs, research and development, etc .

...

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5.9.6 Minicomputers These are the computers of medium range with small size and lesser processing power as compared to mainframes but with versatile feature. It has multi-user, multi-tasking capability to support I 0 to 64 users. 5.9.7 Microcomputers The first ever microcomputer was produced in 1974. It is a small computer with a microprocessor (called chip) as its central processor. These computers are of multiple capacity, Basically, these are characterised by fourth generation computers. They are stable and reliable. They are easy for design, production and testing. Microcomputers workstations are also extensively used for computer graphics, computer aided design and computer aided manufacturing applications. Microcomputers are of two types (i) Personal Computer (ii) Portable Computers. 5.9.8 Personal Computers Personal Computer was first so named by IBM in early 1980 as this microcomputer was designed for use by one person at a time. And that name has become an industry standard ever since. After introduction of 8-bit processors, e.g., Intel 8080, MOS Technology 6502, Motorola MC 6800. Computer manufacturers started to develop different model of personal computer with multiple capabilities. These computers have also undergone several upgradations progressively. In the hierachy, PC-XT comes next. The expression XT stands for extended technology. Next come the PC-ATs, where AT stands for Advanced Technology. 5.9.9 Portable Computers Portable computers are the computers which are very small in size, handy and highly powerful. These computers are of popular varieties with the features of fourth generation computers. Like Personal Computers they have the same capability of performing multitask operations. They are now expensive than the Personal Computers. Various popular types of posibible computers are(i) Laptop Computers (ii) Pen Computers (iii) Note Book Computers (iv) Palmtop Computers (v) Personal Digital Assistants (PDA).

5.10 Functions of Digital Computers Digital Computers are used for many information processing functions by the end users. Most important functions of Digital Computers are as follows : (i) Word processing : Digital computers are used as word processor to prepare memos, letters, reports and other documents with the help of word processing and other writing support software. (ii) Decision Support : Generally Digital Computers are programmable. Through proper programming of an execution, decisions are taken by the managers with its alteration and modifications. (iii) Database Management : File and database management software allows end users to build and maintain files and databases of business records. End users

...

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can then display information they need electronically or produce a variety of analytical reports from the data in the database. (iv) Graphics : Generation of charts and other graphic images are prominently produced by Digital Computers. These visually enhance both the analysis and the presentation of reports vis-a-vis information. (v) Communication : Through telecommunication network and other software packages the digital computers allow end users to access the databases of their organisation and the databanks of external information services and communicate with other end users. (vi) Application Development : Digital Computer through a variety of programming languages and Computer Aided Software Engineering (CASE) tools, enhance and automate many parts of the development process for information system. (vii) Engineering : Digital computers are being used as powerful technical workstations for Computer Aided Design (CAD). This supports the analysis and design process of Computer Aided Engineering (CAE) and other applications. (viii) Personal and home use : Digital Computers use software packages for a veriety of video games educational programs and home management to entertain, educate and support personal and family managements problems. (ix) Special purpose : Several Digital Computers are made and used for execution of special functions. For instance, the computers installed in automobiles to control fuel, igniter and braking system.

EXERCISES 1. Define Hardware. Name the different Hardware Systems of a computer. 2. Define three components of CPU. 3. Point out various functions of control unit. 4. Discuss the important functions of ALU. 5. Define the concept of Main Memory. 6. Discuss the salient features of the Main Memory. 7. What is fixed word Length and variable word length storage? 8. Define software. Name the types of software generally loaded/installed in the computer. 9. What are the main elements of system software? 10. What is application software? 11. What is peopleware? Name the types of personnel generally engaged in the computer installation. 12. Discuss the advantages and disadvantages of Machine Language. 13. Define the advantages and disadvantages of Assembly Language. 14. What are General Pwpose Language and Special Purpose Language? 15. Define computer. Pointout the main functions of a Computer. 16. Define interpreter. What are the main functions of an Interpreter? 17. Distinguish between Interpreter or Compiler. 18. Distinguish software Assembly Language and High Level language. 19. Discuss in brief mentioning the most important features of the Generation of Compyters.

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28. 21. 22. 23.

Define Digital and Analog unts through ATM. Application of a Debit Card for each type of transaction is fully secured by the Personal Identification Number (PIN) of the user.

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2. Credit Card : A Credit Card is also a plastic card that gives the consumer right of purchasing money and goods within their predetermined limit. Application of Credit Card for each type of transaction is fully secured by personal identification number of the user. Basically some financial institutions issue such Credit Cards to the consumers for prodiving debt at higher interest. 3. ATM (Automated Teller Machine) : An ATM is a computerised telecommunication technology by which a finnacial institution performs their financial transactions of individual customer safely and without human interaction like cashier or clerk of a bank. A customer of a particular ATM bank can deposit or withdraw their financial provision easily and somoothly at any place and anywhere by using ATM Card of respective financial institution. The ATM Card is fully secured by a passward or personal identification Number (PIN) allotted to the customer. 4. Demat Account : A dematerialised or demat Account refers to Computerised Accounting System by which a cust~mer can hold their securities electronically. Dematerialisation of securities of a customer/investor is a process of transforming physical scrips used in the settlement of trade execution into computerised ledger accounts maintained by the depository. The depository keeps the account of each beneficial owner (customer/investor) in the same manner as the deposit account of a client is maintained by a bank. Dematerialised securities tend to give a new horizon for the smooth conduct of transaction in the security market by eliminating the risks of loss, theft, forgery in c;ase of securities transaction. 5. Internet Banking : The concept of Internet Banking is innovative and progressive recently in banking business. This banking facility is operated through network and telecommunication devices. Bank to bank transactions, Bank to individual customer transactions which include treasury or financial operations like buying and selling of foreign exchange, inter bank deposits, placement of funds, documentory credit advising and payments, payment on behalf of corporate and netrisk retail customers, traveller's cheques etc. have been conducted over state/private networks. It is a easy and smooth operation. Internet banking mostly reduces paperworks and theft. Moreover this banking facility saves time and energy avoiding· common human obstacles. This provision is also called E-Banking. INTRODUCTION TO FLOW CHARTS Definition : A flow chart is a diagrammatic or pictorial representation of algorithm or of the plan of solution of a problem. It indicates the methods of solution of a particular problem, the relevant operations and computations, the point of decision and other information which is a part of the solution. It consists of a sequence of steps involved in solving a problem. It is an essential tool for programming and it illustrates the strategy and application of logic followed in the program. Concept of ALGORITHMS : The word algorithm derived from the word al-Kwarizmi, 'the man of Kwarizm', the cognomen of a mathematician means recipe, method, technique or procedure to be followed in calculation or other problem-solving operations, especially by a computer. The essential ingredients of an algorithm are : (i) It should be clear. (ii) It should be simple. (iii) It should lead to a unique solution of the problem. (iv) It should involve a finite number. (v) It should have the capability to process some unexpected situations.

APPENDIX A

273

Types of Flow Charts : The Following types of flow chart are required to describe a system fully : Types of Flow Chart

~

System outl"me Chart

l

System Flow Chart

i

l

Run Flow Chart

l

Program Flow Chart

System outline Chart : These charts merely list the inputs, files processed and outputs without regard to any sequence. System Flow Chart : This flow chart presents an overview of the data flow through all parts of a data processing system. If represents flow of documents and operation. It also defines the relationship between inputs, processing and outputs. Run Flow Chart : These are prepared with the help of system flow chart. It is used for showing computer operations internally and frequency of each run. Program Flow Chart : There are most detailed flow charts and are connected with logical and arithmetical operations on data within the CPU. Flow of data between the CPU and between 1/0 devices is also depicted by Program Flow Chart. Symbols used in Flow Charts : A standard set of flow-charting symbols has been adopted internationally as follows : A group of program instructions which perform processing function of the program.

~

Start/End.

c=J

Output/Print

Decision (?/IS)

~

INPUT/OUTPUT

0

Connector

v

OFF Page Connector

~i.l-

Flow Direction.

Advantages of using Flow Charts : The benefits of flow charts are pointed out below : 1. Communication : Flow Chart is a good visual appearance for communicating the logic of system to all concerned. 2. Quicker grasp of relationships : The programe is able chart down lengthy procedures more easily with the help of flow chart for proper understanding of the application. 3. Effective Analysis : The flow chart becomes an analytical model that can be explored for realising the problems and thereby new approach may be suggested. 4. Effective Synthesis : Flow Chart may be used as working models in the design of a new programmer and system. 5. Proper Program Documentation : Flow chart serves as· a good documentation which may be greatly helpful for future reference. l.T. App. in Business-18

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6. Effecient Coding : While programming a flow chart, instruction coded in a programming language may be checked against the flow chart to ensure that no steps are omitted. 7.. Orderly Debugging and Testing of Programes : The flow chart helps in debugging process and removing mistakes. 8. Efficient Programe Maintenance : The maintenance of operating programe is facilitated by flow chart. Limitation of using Flow charts : The following are the limitations of using flow charts : 1. Complex Logic : In case of complex or difficult problem the flow chart also becomes complex and clumsy. 2. Alternations and Modifications : If alterations are required, the flow chart may require re-drawing completely. 3. Reproduction : As the flow chart symbols cannot be typed, reproduction of flow charts is often a problem. 4. Link between Conditions and Actions : Sometimes it becomes difficult to establish the linkage between various conditions and actions to be taken for a particular situation. 5. Standardisation : It is not unique in nature or in prescribed format. It is not easily translated into programming language.

APPENDIX B SHORT QUESTIONS 1. What is Information Technology? Ans. Information technology is a branch of technology relating to generation, collection, storing, processing and dissemination of information and other telecommunication devices. 2. What are the advantages of using wireless communication? Ans. The most inportant advantages of using wireless communication are(i) It enable to link portable computers to corporate distributed data processing systems and thereby helps the users at any place to access information from anywhere at any time. (ii) It provides an infrastructure of client/server Technology that enables users to receive and transmit data easily and smoothly. 3. Define DTP (Desk Top Publishing). Ans. Desk Top Publishing is a software package having the capability of combining and manipulating text with graphics. It also enables users to publish text with headings, charts and variety of pictures. 4. What is the difference between data and Information? Ans. Data are a collection of facts, figures, statistics which can be processed to produce meaningful information. In contrast, information are processed data with a fixed and definite meaning, and useful for direct utilisation of mankind. Data are raw materials and information are finished products. 5. What are the levels of information? Ans. Information can be classified into different levels, such as(i) International Information (ii) National Information (iii) Corporate Information (iv) Organisational Information (v) Individual Information. 6. Point out four qualities of information. Ans. (i) Brevity; (ii) Meaningfulness; (iii) Accuracy; (iv) Timeliness. 7. Define EDP (Electronic Data Processing) Ans. Electronic Data Processing involves the use of computers with fantastic speed, accuracy and the capability to store a large amount of data. It has made computers the most powerful tool for data processing. 8. What is DSS (Decision Support System)? Ans. A software tailored to management needs and designed to aid decision making process. It can make use of spreadsheets, artificial intelligence, computer graphics and online corporate data. 275

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9. What is Artificial Intelligence (AI)? Ans. The capability of a computer to perform functions that are normally associated with human intelligence, such as reasoning, learning and self-improvement. It is also called Expert System (ES). 10. Define Bit and Byte. Ans. The number 'O' or '1' in the representation of a value in binary notation, called as Bit. On the other hand, A fixed number of adjacent bits that are operated on as a unit, i.e., a group of 8 bits is referred to as Byte. 11. How many bytes equivalent to 1 kilobyte, 1 megabyte and 1 gigabyte ? Ans. 1 kilobyte = 2 10 bytes = 1024 bytes 1 megabyte = 220 bytes = 1024 x 1024 bytes 1 gigabyte = 230 bytes = 1024 x 1024 x 1024 bytes 12. How many bytes of data space are covered by 40 GB Hard Disk? Ans. 1 gigabyte = 1024 x 1024 x 1024 bytes; Therefore, 40 GB = 40 x 1024 x 1024 x 1024 bytes. 13. Define Digital Computer. Ans. A computer that solves problems by operating on discrete values of physical quantity representing variables by performing arithmetic and logical processes on the data and from a stored program, is called a Digital Computer. 14. Define MIS (Management Information Systems)? Ans. Management Information Systems is an integrated man/machine system for providing information to support the operations, management and decision making functions in an organisation. It is also called Computerised Management Information System. 15. Define Software. Ans. The programs and the associate rules, procedures and documentation for solving a particular data processing problem by a computer are together referred to as software. 16. What is Hardware? Ans. Physical components of a computer system constitute the computer hardware. When we look at a computer system we are actually looking at the computer hardware. 17. What is system Software? Ans. Systems software refers to all the programs which make the .computer work and is commonly supplied by the computer manufacturers and a large number of institutions which are specific to the hardware devices constituting a particular computer system. 18. What is Application Software? Ans. Applicaion software refers to programs which help the computer to work efficiently for specific application. It is basically a tailored made in-built program provided by the computer Vendors also. 19. What is CPU? What are its main constituents? Ans. CPU stands for Central Processing Unit and it is the heart of a computer system with circuitry to control the interpretation and execution of instructions. It includes theree constituents-(i) Primary Storage Unit (ii) ALU (Arithmetic & Logic Unit) and (iii) Control Unit.

APPENDIX B

277

20. Define Control Unit and point out its most important functions. Ans. It is a part of the Computer CPU that controls the sequence of actions by the program and input/output operations and also contains circuits which decode instructions and addresses. Main functions of Control Unit : (i) It retrieves instructions from main memory and determines the action to be executed. (ii) It then retrieves the data required to be processed from the main memory. (iii) It causes the CPU to actually carry out the required operations. (iv) It fetches the next instructions from the main memory. 21. What do you mean by 'Buffer'? Ans. A temporary or intermediate storage unit used when creating or editing text, or to hold data being transmitted between internal and storage units or between input-output devices and internal storage. 22. Define RAM and ROM. Ans. RAM stands for Random Access Memory. In RAM, it is possible .to select randomly and using any location for direct storage and retrieval of data and instructions. It takes the same amount of time to access any location inside the memory. It is also known as read/write memory. It is volatile in the sense that the stored information is lost when the power supply is failed. ROM stands for Read-Only Memory. In ROM, the information is permanently stored and can only be read. New information cannot be entered. It is non volatile in the sense that the stored information are not lost even in case of power failure. It is also known as permanent stores or static memory. 23. Define Cache Memory. Ans. Cache memory operates between CPU and main memory. Generally CPU speeds are very high compared to the access time of the main memory. To compensate this mis-match in operating speeds, this auxiliary memory from which highspeed retrieval is possible, is incorporated and its access time is close to the processing speed of CPU. It is also kno .. n as high-speed buffer memory. 24. Define primary storage and secondary storage. Ans. Primary storage is the basic means of storing data within the CPU itself. It holds source programs, data files and frequently used routines. It also provides a temporary work area for data produced by intermediate calculation and manipulation. Data from primary storage can be retrieved in millions of a second and access is random. Secondary storage, also called auxiliary storage, is supplementary to the primary storage associated with the CPU. It is used to hold programs and data files not in currently use. It often has much more total storage capacity in relation to the primary storage and is less expensive. 25. Define Compiler and Interpreter. Ans. Compiler is a program that accepts instruction in high-level language and converts each instruction into a lower-level form in which the program can be executed. Interpreter is another type of translator used for translating high-level languages into machine code. It takes one statement of a high-level language and translates it into a machine instruction which is immediately executed.

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26. What is Analog Computer? Ans. A computer in which data is represented in the fom1 of continuously variable physical quantities such as pressure, temperature, revolutions, voltage, etc. is called Analog Computer. 27. Define firmware. Ans. Firmware refers to a permanent software programmed into a read-only memory. The most basic operation such as addition, multiplication, etc. in a computer are carried out by hard-wired circuits. These fundamental tasks are then combined in the form of firmware to produce higher level operation, such as move data, make comparison, etc. 28. Define high level & low level. language. Ans. High Level Languages possess the following characteristics : they are easy to learn and understand, they have a standard language form, they are machine independent, they require the support of a compiler and are self-documenting. Low level language refers to any of the languages not possessing the characteristics of high level language. For example, machine language. 29. Define source program. Ans. It is computer program written in a language designed for ease of expression of a class of problems or procedures by human beings. 30. State the advantages of high level language. Ans. The following are the advantages of high level language (i) It has outstanding capability of handling mathematical calculations. (ii) It is highly standardised. (iii) It is relatively easy to learn and understand. (iv) It is available on most of the computer systems. 31. In what situation can a dot matrix printer be more appropriate than a laserjet? Ans. In the following way a dot matrix printer be more appropriate than a laserjet : (i) When the printing jobs are voluminous dot matrix printers are most suitable. (ii) When the cost factor is in judgement, dot matrix printer is inexpensive than the laserjet. 32. What are advantages of non-impact printers over the impact printers. Ans. ~i) They are most high-speed page printers (ii) They have a prominent print quality (iii) They have possessed black and coloured-both types of printing (iv) They are most suitable for pictorial form of printing. 33. Mention the most importance features of 3rd generation computers. Ans. (i) It uses IC (Integrated Circuits) (ii) Its memory capacity is 32000 to 4 million characters. (iii) Its internal operating speed measures in nanosecond. (iv) It is smaller, faster and more reliable. 34. Mention most important characteristics of 4th generation computers. Ans. (i) It uses LSIC (Large Scale Integrated Circuit). (ii) Its memory capacity is 51200 to 32 million characters. (iii) Its internal operating speed measures in nanosecond. (iv) It is sophisticated, made with microprocessors and very small and reliable.

APPENDIX B

279

35. What is Distributed Data Processing (DDP)? Ans. It is a system in which the computing and other resources are decentralised instead of being located at just one place. The points at which the resources are located are interconnected and autonomously acted with cooperatively by handling the common problem. 36. Point out the ba'iic components of a computer. Ans. The basic components of a computer are(i) Input device (mouse, keyboard, etc.) (ii) Central Processing Unit (CPU) (iii) Output Device. 37. Point out the main functions of an operating system. Ans. The main functions of an operating system are as follows (i) Processor Management. (ii) Memory Management. (iii) Input/output Management. (iv) File Management. 38. What is Debugging? Ans. Debugging is the process of removing errors from a computer program. There are two kinds of errors that a programmer has to deal within a program-syntax error and logical error. 39. Define a Floppy Disk. Ans. A floppy disk is a flexible removable magnetic disk used for storing data. The read-write operations are created out by a read-write head in the floppy drive. Data is recorded in the form of binary signals. The two most popular sizes of floppy disks are 5·25 inches and 3·5 inches diameters. The most important features of a floppy disk are(i) They can store between 150000 to 2 million character. (ii) They are inexpensive and are reusable. (iii) They are used for pooling data on magnetic tape. 40. What is CD-ROM? (Compact Disk-Read-only Memory) Ans. CD-ROM refers to a type of Disk in which data is stored in the form of microscopic pits. A laser scanner is used to read the data. Such disk are called read-only memory. They are not re-writable. 41. What is spooling? Ans. Spooling stands for simultaneous peripheral operation online. It is a technique used for dynamic ta!;> processing. It allows input and output operations to occur simultaneously with processing operation. Hence with the aid of spooling technique, the CPU does not have to wait for the slow input/output devices and therefore, it can work at its maximum speed. 42. What is lnterblock Gap? Ans. The distance on a magnetic tape between the end of one block and the beginning of the next is called Inter-record Gap or Interblock Gap. 43. What is Booting? Ans. A technique for loading a program into computer memory in which the program's, initial instructions direct the loading of the rest of the program.

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44. What is Bubble Memory? Ans. It is a solid state device using the presence or absence of electronic bubbles in the device to register binary patterns. These bubbles remain even after electric power is removed and so do not have the drawbacks of conventional memory. 45. Define Intelligent Terminal. Ans. It is terminal having local processing capability. It has a built-in CPU and can perform specific functions such as editing data, controlling other functions upon input or output, etc. 46. Point out the advantages of Magnetic Tape. Ans. (i) Unlimited length of records (ii) Compact storage (iii) Reduced cost (iv) Rapid transfer rate. 47. Point out the advantages of Magnetic Disk. Ans. (i) Random access capability (ii) Easier updation (iii) Faster data transfer rates (iv) Quick and direct identification. 48. What is Multiplexor? Ans. Multiplexor is a device that enables several devices to share communication line. The multiplexor scans each device to collect and transmit data on a single channel to the CPU. 49. Define Multi-programming. Ans. A technique for handling two or more independent programs simultaneously by overlapping or interleaving their execution or by loading them into primary storage and executing their instructions concurrently. 50. What is sequential file organisation? Ans. In this file organisation, records are written in the same sequence in which they are collected, but they are organised into certa~n order according to a specific data field, which is known as key field. 51. What is indexed sequential file organisation? Ans. This organisation is a combination of sequential and direct file organisation. Though the files are recorded serially, in a logical sequence indexing or reference techniques are used so that access can be on a random basis as well as sequentially. 52. What is database management system? Ans. The comprehensive software system that builds, maintains and provides access to a database. It is a combination of hardware and software that controls and processes all requests for data in database. 53. Define Database Administrator. Ans. A person who has overall responsibility for developing and maintaining the database, determining how the database contents are organised and interrelated. 54. What is database? Ans. A stored collection of inter-related data items with a common context that is needed by organisations and individuals to meet their information processing and retrieval requirements.

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281

55. Define word processing. Ans. Word processing is a system of storing, manipulating and formatting of textual data to produce reports, letters and other documents using a purpose-built computer. After the text is corrected to the users, satisfaction it can be printed and/or saved for later use. 56. Define Electronic Spreadsheet. Ans. This is a computer program used chiefly for accounting, in which figures arranged in a grid can be manipulated and used in calculations. A spreadsheet program package helps in the combination of tabular data involving hundreds of calculations with the aid of computer depending upon the various parameters specified by the user. The compiled information is displayed in the columns and rows of the table known as spreadsheet with suitable headings. 57. Defme LAN. Ans. A Local Area Network is that in which computers and peripheral devices are located in close proximity to each other, say, within a office, factory or building. These are linked by telephone lines as well as coaxial and fibre optic cables. It provides a very high-speed of data transfer. 58. Defme WAN. Ans. Wide Area Networks are country-wide or worldwide networks which are channels as microwaves and satellites. Thus wide area network includes all the networks that are involved in transporting information from one geographic location to another. In WAN Network, data transmission speed is lower and the cost of data transmission is high. 59. What is client/server concept? Ans. Client-server concept refers to a collection of computers (servers) holding shareable resoures and computers (clients) which access these resources from the servers. Servers are dedicated to store, process and distribute data and resources while clients access and use the data and resources managed by servers. 60. What is Network Topology? Ans. Network Topology refers to the cable pattern used to connect the clients with the servers. There may be multiple topologies combined within a single network. To ensure proper communication between different topologies special hardware may be required. 61. What is Network? Ans. A network may be defined as an interconnection of two or more computers, attached with communication media, for the purpose of sharing information and resources. 62. What are the basic components of a computer? Ans. The Basic components of a computer are(i) Input device (Mouse, Keyboard, etc.) (ii) Processing Unit (Memory, AIL & Control Unit.) (iii) Output device (e.g., Printer, Scanner etc.) 63. What is Internet? Ans. The Internet is a worldwide network of networks that provide access to people and information.

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64. Define Electronic Mail. Ans. A genetic term used to describe the transmission of messages by the use of personal computer systems and communication facilities. 65. Define Intranet. Ans. An Intranet may be defined as the application of internet technology to the internal business applications in the organisation. 66. What is Protocol? Ans. Protocol refers to computer software ensuring transmission between computers and a set of standards defining the procedure and the format for data transmission via communication links. 67. What is Firewall? Ans. Firewall is a combination of hardware and software to provide one of the most effective type of security on the Internet. It is a part of computer system or network which is designed to block unauthorised access while permitting outward communication. 68. What is E-commerce ? Ans. Electronic commerce refers to conducting business electronically with customers or consumers via e-mail, electronic bulletin board, electronic funds transfer etc. 69. Define Information System Audit. Ans. It refers to the process of collecting and evaluating evidence to determine whether a computer system safeguards assets, maintains data integrity, allows organisational goals to be achieved effectively and uses resources efficiently. 70. What is a computer virus? Ans. If refers to a destructive program that has the ability to regenerate itself and infect other programs or disks. Virus is a piece of code surreptitiously introduced into a system in order to corrupt it or destroy data. 71. Defme Eletronic Data Interchange (EDI). Ans. It refers to the exchange of structured business information between application among trading partners by agreed message standards through electronic devices. 72. What is FEDI (Financial Electronic Data Interchange? Ans. It refers to the exchange of payment and payment related information. It utilises the proprietary payment systems developed by the banking industry worldwide. 73. What are the main functions of any operating system? Ans. (i) Processor Management (ii) Memory Management (iii) Input/output Management. (iv) File Management. 74. What is'Master file? Ans. Master file is a file in which permanent, historical, statistical or identification type of data and certained and used as an authority/central file in a given data/transaction processing job.

APPENDIX C ABBREVIATIONS 3GL 4GL 5GL

Third Generation Language Fourth Generation Language Fifth Generation Language

AAL AI ALGOL ALU ANSI

ATM Adaptation Layer Artificial Intelligence Algorithmic Language Arithmetic and Logic Unit American National Standard Institute Advice of Charge Application Programming Interface A Programming Language Address Resolution Protocol American Standard Code for Information Interchange Application Specific Interchange Circuit Asynchronus Transfer Mode

A

AOC API APL ARP ASCII ASIC ATM

B BBS BCD BER BIOS B-ISDN BIT

BRI BRI BUS

Bulletin Board System Binary Coded Decimal Bit Error Rate Basic Input/Output System Broadband Integrated ServiCes Digital Network Binary Digit Basic Rate Interface (on ISDN) Basic Rate Interface Broadcast and Unknown Server (LAN Emulation on ATM)

c C/SA CAD CADD CAI CAM CASE CBIS CBR CBT CCD CD-ROM

Cll.ent/Server Architecture Computer Aided Design Computer Aided Design and Drafting Computer .Aided Instruction Computer Aided Manufacturing Computer Aided Software Engineering Computer Based Information System Constant Big Rate (on ISDN) Computer Based Training Charge-Coupled Device Compact Diskette Read-Only Memory 283

284

CGI CLIP" CMIP CMIS CBOL CODASYL CODEC COM CP/M CPU CRT CSTA CSU/DSU CTI CUG CVRAM

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Common Gateway lnterface/(ISDN) Caller Line Identification Presentation Common Management Information Protocol Common Management Information Service Common Business Oriented Language Conference On Data Systems Language Coder/Decoder Computer Output Microfilm Control Program/Microprocessor Central Processing Unit Cathode Ray Tube Computer Supported Telecommunication Appliances Channel Service Unit /Data Service Unit Computer Telephony Integration Closed User Groups Cached Video RAM

D DAA DAC DASO OBA DBMS DDL DDP DES DFD DHCP DL/I DME DMI DML DMP DNS

DOS DROO DSS

DTL DTP DTP DTVC

DVD

Distributed Application Architecture (HP) Digital to Audio Conversion Direct Access Storage Device Database Administrator Database Management System Data Definition Language (DBMS) Distributed Data Processing Data Encryption Standard Data Flow Diagram Dynamic Host Configuration Protocol Data Language/I Distributed Management Environment (OSF) Desktop Management Interface (DMTF) Data Manipulation Language (DBMS) Dot Matrix Printer Domain Name Service or System Disk Operating System Defence Research and Development Organisation (India) Decision Support System Diode-Transistor Logic ~esktop Publishing Distributed Transaction Processing Desktop Video Conference Digital Video Disk

E EAN EBCDIC E-Cash ECB

European Article Number (Bar Code Standard) Extended Binary Coded Decimal Interchange Code Electronic Cash Electronic Code Block (Encryption)

APPENDIX C

ECC ECO ECS EDI EDP EDVAC EFT EFTS EI EIS EISA e-Mail EMM EMS ENIAC EOT EPROM EPS ER ERP

Error Correction Code Enhanced Colour Display Electronic Clearance System Electronic Data Interchange Electronic Data Processing Electronic Discrete Variable Automatic Computer Electronic Fund Transfer Electronic Fund Transfer System Enterprise Integration Executive Information System Extended Industry Standard Architecture Electronic Mail Expanded Memory Manager (DOS) Expanded Memory Specification (DOS) Electronic Numerical Integrator and Calculator End-of-Tape Erasable and Programmable Read-Only Memory Electronic Payment System Entity Relationship Enterprise Resource Planning

F FAQ FAX FDDI FEP FIFO FORTRAN FPU FQDN FTP FUNI FEDI

Frequently Asked Questions Facimile Fibre Distributed Data Interface Front End Processor First-in First-out Formula Translation Floating Point Unit Fully Qualified Domain Name File Transfer Protocol Frame User-to-Network Interface Financial Electronic Data Interchange

G GB GIGO GPS GPSS GPSS GUI

Gigabyte Garbage-in Garbage-out Global Positioning System Gateway Packet Switching System General Purpose Simulation System Graphic User Interface

H HDX HIPO HLL HP HTML

Half Duplex Hierarchy plus Input-Porcess-Output High Level Language Hewlett Packard Hyper Text Markup Language (WWW)

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Hyper Text Transport Protocol (WWW) Hardware

I 1/0 IBG IBM IC ICAI ICMP IDEA IDMS IMSI INFLIBnet INGRES

IOCS IP IPG

IPI IPO

IRC IRG ISA ISAM ISDN ISO ISP ISR ITV

IVR

Input/Output Inter Block Gap International Business Machines Integrated Circuit Interactive Computer Aided Instruction Internet Control Message Protocol (TCP/IP) International Data Encryption Algorithm Integrated Data Management System International Mobile Subscriber Identity Information Library Network Interactive Graphic Relational System Input/Output Control System Internet Protocol Interactive Programme Generator Intelligent Peripheral Interface Input Processing Output Internet Relay Chat Inter Record Gap (on Magtape) Industry Standard Architecture Indexed Sequential Access Method Integrated Service Digital Network International Standards Organisation Internet Service Provider Interrupt Service Routine Interactive TV Interactive Voice Response

J JCL

Job Control Language

K kb

Kilobyte

L LAN LANE LAP LCD LED LIMD LISP LSI

LU LSD

Local Area Network LAN Emulation Link Access Protocol Liquid Crystal Display Light Emitting Diode Large Scale In-Memory Database List Processor Large Scale Integration Logical Unit Logical System Design

APPENDIX C

M MAC MAP MAR mb MB MDR MICR MIPS MIS MMU MODEM MPOA MRP MS DOS MSI

Media Access Control Manufacturing Automation Protocol Memory Address Register Million Bits Megabytes Memory Data Register Magnetic Ink Character Reader or Recognition Million Instruction Per Second Management Information System Memory Module Unit Modulator Demodulator Multi-protocol over ATM Material Requirement Planning Microsoft Disk Operating System Medium Scale Integration

N NAP NAU NetBIOS NIC NIC NNI NOS

Network Access Point Network Addressable· Unit Network Basic Input/Output System National Informatics Centre Network Interface Card Network-to-Network Interface Network Operating System

0 OCR OLTP OMR OODB OS OS/2 OSI OSPF OT-PROM

Optical Character Recognition or Reader On-line Transaction Processing Optical Mark Reader Object-Oriented Database Operating System Operating System/2 Open Systems Interconnect Open Shortest Path First One Time Programmable Read-Only Memory

p PAD PC PC PC/AT PC/XT PCB PCDOS PCI PCM PDA

Packet Assembler Dissembler Personal Computer Program Counter Personal Computer/Advanced Technology Personal Computer/Extended Technology Printed Circuit Board Personal Computer Disk Operating System Peripheral Component Interface or Interconnect (BUS) Pulse Code Modulator Personal Digital Assistants

287

288 PDL PERT PIM PL/1 PLA PLAN PM PNNI

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

POS POTS PPP PPTP PRI PROM PS/2 PSDN PSE PSPDN PSTN PVC

Program Design Language Program Evaluation and Review Technique Personal Information Manager Programming Language/I Programmable Logic Array Programmable Language Phase Modulation Private Network-to-Network Interface Post Office Protocol Point-of-Sale Plain Old Telephone Services Point-to-Point Protocol Point-to-Point Tunneling Protocol Primary Rate Interface Programmable Read -Only Memory Personal System/2 Packet Switched Data Network Packet Switching Exchange Packet Switched Public Data Network Public Switched Telephone Networks Permanent Virtual Circuit.

QoS

Quality of Service

POP

Q R RAD RAM RAP RARP RAS RCU RDBMS RIP RISC RJE RLOGIN RMON ROM RPC PRG

RZ

Rapid Application Development Random Access Memory Real-time Analytical Processing Reverse Address Resolution Protocol (TCP/IP) Remote Access Service Remote Control Unit Relational Database Management System Routing Information Protocol Reduced Instruction Set Computing Remote Job Entry Remote Log-In (UNIX) Remote Monitor Read-only Memory Remote Procedure Calls Report Program Generator Return to Zero (data transmission)

s SD RAM SDSL SEPP SGML

Synchronous Dynamic Random Access Memory Symmetric Digital Subscriber Line Secure Electronic Payment Protocol Standard Generalised Mark-up Language

APPENDIX C

S-HTIP SIM SIMD SIMM SISD SLIP SMTP SNA SOHO SONET SPX/IPX SQL SRAPI SRINIC SSI SSMP STDM STP SVC SVGA SVRAM SW

Secure Hyper Text Transport Protocol Subscriber Identity Module (Mobile Telephone) Single Instruction Multiple Data (Parallel Processing) Single In-line Memory Module Single Instruction Single Data (Parallel Processing) Serial Line Internet Protocol Simple Mail Transfer Protocol System Network Architecture Small Office Home Office Synchronus Optical Network Sequenced Packet Exchange/Internet Packet Exchange Structured Query Language Speech Recognition Application Programming Interface Stanford Research Institute Network Information Centre Small Scale Integration (IC) Scalable Shared Memory Processor Synchronous Time Division Multiplexing Shielded Twisted Pair Switched Virtual Circuit Super Video Graphic Array Synchronous Video Random Acess Memory Software

T TCP/IP TCU TDM TDMA TDU

TFf TP TPC TPU TSO TIL

Transmission Control Protocol/Internet Protocol Terminal Control Unit Time Division Multiplexing Time Division Multiplexed Access Terminal Drive Unit Thin Film Transistor (Flat Panel Display) Transaction Processing Transaction Processing Council (for benchmark) Terminal Processing Unit Time Sharing Option Transistor-Transistor Logic

u UART

ucc

UDF UDP USLI UMA UNI UNIVAC UNTDI UPC UPS

Universal Asynchronous Receiver /Transmitter Uniform Code Council (Bar Coding) Universal Data Format (HP/Philips) User Datagram Protocol Ultra Large Scale Integration (IC) Unified Memory Architecture User-to-Network Interface Universal Automatic Computer United Nations Trade Data Interchange Universal Product Code (Bar Code Standard) Uninterrupted Power Supply

l.T. App. in Business-19

289

290

URL USART USB USRT UTP UV-PROM

INFORMATION TECHNOLOGY AND ITS APPLICATION IN BUSINESS

Uniform Resource Locator Universal Synchronous/Asynchronous Receiver /Transmitter Universal Serial Bus Universal Synch:onous Receiver/Transmitter Unshielded Twisted Pair Ultra Violet Ray Erasable and Programmable Read-only Memory

v VAC VANs YAP VBR VDSL VDU VGA VIP VIVID VLAN VLSI VNN VPN VR VRAM YRC VRML VSAM VSAT VSNL VTOC

Value Added Carrier Value Added Networks Value Added Process Variable Bit Rate (ISDN) Very High Datarate Subscriber Line Visual Display Unit Video Graphic Array Visual Programming Video, Voice, Image and Data Virtual LAN Very Large Scale Integration (IC) Virtual Network Navigator Virtual Private Network Virtual Reality Video Random Access Memory Virtual Redundancy Check Virtual Reality Mark-up Language Virtual Sequential Access Method Very Small Aperture Terminal Videsh Sanchar Nigam Ltd. Virtual Table of Contents

w WAIS WAN WAVE WORM WRAM WWW WAP

Wide Area Information System Wide Area Network Wide Area Voice Exchange Write Once Read Many Window Random Access Memory World Wide Web Wireless Application Protocol

x XGA XMS XNS

Extended Graphic Array Extended Memory Specification Xerox Network System