Computer Science Textbook for Class XI PDF

COMPUTER SCIENCE Textbook for Class XI 2024-25 Prelims.indd 1 08-Apr-19 10:03:55 AM  11120 – Computer Science ISBN 978-93-5292-117-1...

COMPUTER SCIENCE Textbook for Class XI 2024-25 Prelims.indd 1 08-Apr-19 10:03:55 AM  11120 – Computer Science ISBN 978-93-5292-117-1 Textbook for Class XI First Edition ALL RIGHTS RESERVED May 2019 Vaishakha 1941  No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, Reprinted electronic, mechanical, photocopying, recording or otherwise without the prior permission of the publisher. June 2021 Jyeshtha 1943  This book is sold subject to the condition that it shall not, by November 2021 Agrahayana 1943 way of trade, be lent, re-sold, hired out or otherwise disposed of without the publisher’s consent, in any form of binding or October 2022 Kartika 1944 cover other than that in which it is published. March 2024 Chaitra 1946  The correct price of this publication is the price printed on this page, Any revised price indicated by a rubber stamp or by a sticker or by any other means is incorrect and should be unacceptable. OFFICES OF THE PUBLICATION Division, NCERT PD 30T SU NCERT Campus Sri Aurobindo Marg New Delhi 110 016 Phone : 011-26562708 © National Council of Educational 108, 100 Feet Road Research and Training, 2019 Hosdakere Halli Extension Banashankari III Stage Bengaluru 560 085 Phone : 080-26725740 Navjivan Trust Building P.O.Navjivan Ahmedabad 380 014 Phone : 079-27541446 CWC Campus Opp. Dhankal Bus Stop Panihati Kolkata 700 114 Phone : 033-25530454 CWC Complex Maligaon Guwahati 781 021 Phone : 0361-2674869 ` 290.00 Publication Team Head, Publication : Anup Kumar Rajput Division Chief Editor : Shveta Uppal Printed on 80 GSM paper Chief Production : Arun Chitkara Published at the Publication Officer Division by the Secretary, National Chief Business : Amitabh Kumar Council of Educational Research Manager (In charge) and Training, Sri Aurobindo Marg, Assistant Production : Om Prakash New Delhi 110 016 and printed at Officer Chaar Dishayen Printers (P) Ltd., G 40-41, Sector-3, Noida 201 301, Uttar Pradesh Cover and Layout DTP Cell 2024-25 Prelims.indd 2 29-03-2024 14:45:48  Foreword Computer science as a discipline has evolved over the years and has emerged as a driving force for socio-economic activities. It has made continuous inroads into diverse areas — be it business, commerce, science, technology, sports, health, transportation or education. With the advent of computer and communication technologies, there has been a paradigm shift in teaching learning at the school level. The role and relevance of this discipline is in focus because the expectations from the school pass-outs have grown to be able to meet the challenges of the twenty-first century. Today, we are living in an interconnected world where computer-based applications influence the way we learn, communicate, commute or even socialise! There is a demand for software engineers in various fields like manufacturing, services, etc. Today, there are a large number of successful startups delivering different services through software applications. All these have resulted in generating interest for this subject among students as well as parents. Development of logical thinking, reasoning and problem-solving skills are fundamental building blocks for knowledge acquisition at the higher level. Computer plays a key role in problem solving with focus on logical representation or reasoning and analysis. This book focuses on the fundamental concepts and problem-solving skills while opening a window to the emerging and advanced areas of computer science. The newly developed syllabus has dealt with the dual challenge of reducing curricular load as well as introducing this ever evolving discipline. As an organisation committed to systemic reforms and continuous improvement in the quality of its products, NCERT welcomes comments and suggestions which will enable us to revise the content of the textbook. Hrushikesh Senapaty Director New Delhi National Council of Educational 8 August 2018 Research and Training 2024-25 Prelims.indd 3 08-Apr-19 10:03:55 AM  2024-25 Prelims.indd 4 08-Apr-19 10:03:55 AM  Preface In the present education system of our country, specialised or discipline- based courses are introduced at the higher secondary stage. This stage is crucial as well as challenging because of the transition from general to discipline-based curriculum. The syllabus at this stage needs to have sufficient rigour and depth while remaining mindful of the comprehension level of the learners. Further, the textbook should not be heavily loaded with content. Computers have permeated in every facet of life. Study of basic concepts of computer science has been desirable in education. There are courses offered in the name of Computer Science, Information and Communication Technology (ICT), Information Technology (IT), etc., by various boards and schools up to secondary stage, as optional. These mainly focus on using computer for word processing, presentation tools and application software. Computer Science (CS) at the higher secondary stage of school education is also offered as an optional subject. At this stage, students usually opt for CS with an aim of pursuing a career in software development or related areas, after going through professional courses at higher levels. Therefore, at higher secondary stage, the curriculum of CS introduces basics of computing and sufficient conceptual background of Computer Science. The primary focus is on fostering the development of computational thinking and problem-solving skills. This book has 11 chapters covering the following broader themes: Fundamentals: basic understanding of computer system, hardware components and software, data representation, number system, encoding as well as awareness of emerging trends in computer science. Problem-solving: problem analysis, algorithm, flowchart, implementation, testing and maintenance. Programming: basic constructs of a program using Python programming language — program structure, identifiers, variables, flow of control, advanced data types, functions. Societal impact: awareness of digital footprints, data privacy and protection, cyber crime, etiquettes in a digital society and implications on security, privacy, piracy, ethics, values and health concerns. Chapters 1, 2, 3, 4 and 11 have two additional components — (i) activities and (ii) think and reflect for self assessment while learning as well as to generate further interest in the learner. Python programming language is introduced that is easy to learn in interactive and script mode. A number of hands-on examples are given to gradually explain methodology to solve different types of problems across the Chapters 5 to 10. The programming examples as well as the exercises in these chapters are required to be solved in a computer and verify with the given outputs. 2024-25 Prelims.indd 5 08-Apr-19 10:03:55 AM  vi Group projects through case studies are proposed to solve complex problems. Peer assessment of these projects will promote peer-learning, team spirit and responsiveness. Some exercises have been made in case- study format to promote problem-finding and problem-solving skills. Box items (light green background) are pinned inside the chapters either to explain related concepts or to provide additional information related to the topic covered in that section. However, these box items are not to be assessed through examinations. Unicode encoding scheme for Indic scripts have also been introduced to motivate students to solve problems in public services and the local micro or small businesses in India. These chapters have been written by involving practicing teachers as well as subject experts. These have been iteratively peer-reviewed. I would like to place on record appreciation for Professor Om Vikas for leading the review activities of the book as well as for his guidance and motivation to the development team throughout. Several iterations have resulted into this book. Thanks are due to the authors and reviewers for their valuable contribution. Comments and suggestions are welcome to make this endeavour of par excellence. New Delhi Rejaul Karim Barbhuiya 9 August 2018 Assistant Professor Department of Education in Science and Mathematics, NCERT 2024-25 Prelims.indd 6 08-Apr-19 10:03:55 AM  Textbook Development Committee Chief Advisor Om Vikas, Professor (Retd.), Former Director, ABV-IIITM, Gwalior, M.P. Members Anuradha Khattar, Assistant Professor, Miranda House, University of Delhi Ashish Dhalwankar, PGT (Computer Science), Centre Point School, Nagpur, Maharashtra Chetna Khanna, Freelance Educationist, Delhi Harita Ahuja, Assistant Professor, Acharya Narendra Dev College, University of Delhi Mudasir Wani, Assistant Professor, Government College for Women, Nawakadal, Srinagar Pratiksha Majumdar, PGT (Computer Science), School of Scholars, Nagpur, Maharashtra Priti Rai Jain, Assistant Professor, Miranda House, University of Delhi Rinku Kumari, PGT (Computer Science), Kendriya Vidyalaya, Sainik Vihar, Delhi Sajid Yousuf Bhat, Assistant Professor, University of Kashmir, J&K Sarnavi Mahesh, Research Scholar, Universita Del Salento, Italy Sharanjit Kaur, Associate Professor, Acharya Narendra Dev College, University of Delhi Sonali Gogate, Software Consultant, Pune, Maharashtra Tapasi Ray, Former Global IT Director, Huntsman Corporation, Singapore Vandana Tyagi, PGT (Computer Science), Kendriya Vidyalaya, JNU, Delhi Member-coordinator Rejaul Karim Barbhuiya, Assistant Professor, DESM, NCERT, Delhi 2024-25 Prelims.indd 7 08-Apr-19 10:03:55 AM  Acknowledgements The National Council of Educational Research and Training acknowledges the valuable contributions of the individuals and organisations involved in the development of Computer Science Textbook for Class XI. The Council expresses its gratitude to the syllabus development team including MPS Bhatia, Professor, Netaji Subhas Institute of Technology, Delhi; T. V. Vijay Kumar, Professor, School of Computer and Systems Sciences, Jawaharlal Nehru University, New Delhi; Zahid Raza, Associate Professor, School of Computer and Systems Sciences, Jawaharlal Nehru University, New Delhi; Vipul Shah, Principal Scientist, Tata Consultancy Services, and the CSpathshala team; Aasim Zafar, Associate Professor, Department of Computer Science, Aligarh Muslim University, Aligarh; Faisal Anwer, Assistant Professor, Department of Computer Science, Aligarh Muslim University, Aligarh; Smruti Ranjan Sarangi, Associate Professor, Department of Computer Science and Engineering, Indian Institute of Technology, Delhi; Vikram Goyal, Associate Professor, Indraprastha Institute of Information Technology (IIIT), Delhi; Tabrez Nafis, Assistant Professor, Jamia Hamdard, New Delhi and Mamur Ali, Assistant Professor, Central Institute of Educational Technology, NCERT, New Delhi. The Council is thankful to the following resource persons for editing, reviewing and refining the manuscript of this book — Mukesh Kumar, DPS RK Puram, Delhi; Gurpreet Kaur, G.D. Goenka Public School, Vasant Kunj, Delhi; Gautam Sarkar, Modern School, Barakhamba Road, Delhi; Aswin K. Dash, Mother’s International School, Delhi; Nancy Sehgal, Mata Jai Kaur Public School, Delhi; Ashish Kumar Srivastava, Assistant Professor, Department of Education in Science and Mathematics, NCERT, New Delhi; Neelima Gupta, Professor, Department of Computer Science, University of Delhi; Anamika Gupta, Assistant Professor, Shaheed Sukhdev College of Business Studies, University of Delhi. The Council further acknowledges the contributions of Anuja Krishn, Freelance Editor, for language editing. The Council also gratefully acknowledges the contributions of Meetu Sharma, Graphic Designer; Kanika Walecha, DTP Operator; and Pooja, Junior Project Fellow, in shaping this book. The contributions of the office of the APC, DESM and Publication division, NCERT, New Delhi, in bringing out this book are also duly acknowledged. The Council also acknowledges the contribution of Shilpa Mohan, Assistant Editor (Contractual) Publication Division, NCERT for copy editing this book. The efforts of Sadiq Saeed, DTP Operator (Contractual) and Sachin Tanwar, DTP Operator (Contractual), Publication Division, NCERT, are also acknowledged. 2024-25 Prelims.indd 8 08-Apr-19 10:03:56 AM  Contents Foreword iii Preface v Chapter 1 : Computer System 1 1.1 Introduction to Computer System 1 1.2 Evolution of Computer 3 1.3 Computer Memory 5 1.4 Data Transfer between Memory and CPU 7 1.5 Microprocessors 8 1.6 Data and Information 10 1.7 Software 14 1.8 Operating System 20 Chapter 2 : Encoding Schemes and Number System 27 2.1 Introduction 27 2.2 Number System 30 2.3 Conversion between Number Systems 34 Chapter 3 : Emerging Trends 45 3.1 Introduction 45 3.2 Artificial Intelligence (AI) 45 3.3 Big Data 49 3.4 Internet of Things (IoT) 51 3.5 Cloud Computing 53 3.6 Grid Computing 55 3.7 Blockchains 56 Chapter 4 : Introduction to Problem Solving 61 4.1 Introduction 61 4.2 Steps for Problem Solving 62 4.3 Algorithm 64 4.4 Representation of Algorithms 65 4.5 Flow of Control 70 4.6 Verifying Algorithms 77 4.7 Comparison of Algorithm 79 2024-25 Prelims.indd 9 08-Apr-19 10:03:56 AM  x 4.8 Coding 80 4.9 Decomposition 81 Chapter 5 : Getting Started with Python 87 5.1 Introduction to Python 87 5.2 Python Keywords 90 5.3 Identifiers 91 5.4 Variables 91 5.5 Comments 92 5.6 Everything is an Object 93 5.7 Data Types 94 5.8 Operators 99 5.9 Expressions 104 5.10 Statement 106 5.11 Input and Output 107 5.12 Type Conversion 108 5.13 Debugging 112 Chapter 6 : Flow of Control 121 6.1 Introduction 121 6.2 Selection 122 6.3 Indentation 126 6.4 Repetition 127 6.5 Break and Continue Statement 132 6.6 Nested Loops 136 Chapter 7 : Functions 143 7.1 Introduction 143 7.2 Functions 145 7.3 User Defined Functions 146 7.4 Scope of a Variable 158 7.5 Python Standard Library 160 Chapter 8 : Strings 175 8.1 Introduction 175 8.2 Strings 175 8.3 String Operations 177 8.4 Traversing a String 180 8.5 String Methods and Built-in Functions 180 8.6 Handling Strings 184 2024-25 Prelims.indd 10 08-Apr-19 10:03:56 AM  xi Chapter 9 : Lists 189 9.1 Introduction to List 189 9.2 List Operations 190 9.3 Traversing a List 192 9.4 List Methods and Built-in Functions 193 9.5 Nested Lists 195 9.6 Copying Lists 196 9.7 List as Arguments to Function 197 9.8 List Manipulation 199 Chapter 10 : Tuples and Dictionaries 207 10.1 Introduction to Tuples 207 10.2 Tuple Operations 209 10.3 Tuple Methods and Built-in Functions 211 10.4 Tuple Assignment 212 10.5 Nested Tuples 213 10.6 Tuple Handling 213 10.7 Introduction to Dictionaries 215 10.8 Dictionaries are Mutable 216 10.9 Dictionary Operations 217 10.10 Traversing a Dictionary 217 10.11 Dictionary Methods and Built-in functions 218 10.12 Manipulating Dictionaries 219 Chapter 11 : Societal Impact 229 11.1 Introduction 229 11.2 Digital Footprints 229 11.3 Digital Society and Netizen 231 11.4 Data Protection 235 11.5 Cyber Crime 239 11.6 Indian Information Technology Act (IT Act) 242 11.7 Impact on Health 242 2024-25 Prelims.indd 11 08-Apr-19 10:03:56 AM  2024-25 Prelims.indd 12 08-Apr-19 10:03:56 AM