PREETI ARORA
                         DOEACC ‘A’ level, M.Sc–IT, M.Tech–IT
                           Sr. Computer Science Teacher
                         Educational Publishers
          SULTAN CHAND & SONS (P) LTD
          Educational Publishers
          4859/24, Darya Ganj, New Delhi-110 002
          Phones      :  4354 6000 (100 Lines), 2324 3939
          Fax         :  (011) 4354 6004, 2325 4295
          E-mail      : scs@sultanchandebooks.com
          Buy books online at :  www.sultan-chand.com
          ISBN: 978-93-89174-77-9
          First Edition 2019
          Second Thoroughly Revised Edition 2020
            All rights reserved.
          No part of this book may be reproduced or copied in any form or by any means (graphic, electronic or mechanical, including 
          photocopying, recording, taping, or information retrieval system) or reproduced on any disc, tape, perforated media or any other 
          information storage device, etc., without the prior written permission of the publishers. Breach of this condition is liable for legal 
          action. Anyone who brings information regarding any such reproduction will be handsomely rewarded.
          Publication of Key to this book is strictly prohibited.
          Every effort has been made to avoid errors or omissions in this publication. In spite of this, some errors might have crept in. Any 
          mistake, error or discrepancy noted may be brought to our notice which shall be taken care of in the next edition. It is notified that 
          neither the publishers nor the author or seller will be responsible for any damage or loss of action to anyone, of any kind, in any 
          manner, therefrom.
          For faulty binding, misprints or for missing pages, etc., the publishers’ liability is limited to replacement within one month of the 
          purchase by a similar edition. All expenses in this connection are to be borne by the purchaser.
          All disputes are subject to Delhi jurisdiction only.
          Printed at: Rajiv Binding House, Delhi
                             PREFACE
          This thoroughly revised edition of Computer Science with Python for Class XI 
          students aims at providing an in-depth understanding of the CBSE curriculum. It 
          focuses on teaching Python language to help students learn programming concepts 
          and develop problem-solving skills. With easy-to-understand examples, flow charts 
          and other such tools in the book, the student will learn to design the logic of a 
          program and then implement that program using Python. The book contains ample 
          concise and practical example programs along with diagrams and instances from 
          real-life situations. Each chapter contains tested, debugged and error-free codes 
          with screenshots.
          Based on the CBSE curriculum, this book has been divided into four units:
          •  Unit 1: Computer Systems and Organization—Chapters 1 & 2
          •  Unit 2: Computational Thinking and Programming—Chapters 3 to 10
          •  Unit 3: Data Management (DM–1)—Chapters 11 & 12
          •  Unit 4: Society, Law and Ethics (SLE–1)—Chapter 13
          The book also includes ample Viva Voce Questions. Installation Guide to MongoDB 
          and Python in QR Code, CTM (Commit To Memory) and Points To Remember  
          for easy recall of important terms and concepts are other notable features of  
          the book.
          Besides, Presentation on Python, Chapter-wise Program Codes, Practical  
          File, Sample Papers, Model Test Papers for practice and Python and 
          MongoDB Software Dump are available online and can be easily accessed at  
          sultan-chand.com/ws/python11
          We are sure this book will prove to be of immense help to the students and teachers 
          alike. Constructive feedback for the improvement of the book will be highly 
          appreciated and gratefully acknowledged.
          My special thanks are due to Mrs Rinku Kumari for her value additions to the 
          book.
          Last but not the least, I take this opportunity to thank my esteemed publishers, 
          Sultan Chand & Sons (P) Ltd, for their patience, encouragement and assistance 
          in bringing out this book. 
                                                 AUTHOR
                                                   Syllabus
                                             COMPUTER SCIENCE (NEW)
                                          CLASS XI Code No. 083 (2020–2021)
              Distribution of Marks and Periods:
                  Unit No.                 Unit Name                    Marks          Periods
                                                                                 Theory     Practical
                    1.    COMPUTER SYSTEMS AND ORGANIZATION              10        10          2
                    2.    COMPUTATIONAL THINKING AND PROGRAMMING         35        60         45
                    3.    DATA MANAGEMENT - 1                            15        30         23
                    4.    SOCIETY, LAW AND ETHICS - 1                    10        10          --
                          Total                                          70        110        70
              Unit 1:  COMPUTER SYSTEMS AND ORGANIZATION
                     •  Basic computer organization: Description of a computer system and mobile system, CPU, memory, hard 
                       disk, I/O, battery.
                     •  Types of software: Application, system, utility.
                     •  Memory units: bit, byte, MB, GB, TB and PB.
                     •  Boolean logic: OR, AND, NAND, NOR, XOR, NOT, Truth tables, De Morgan’s laws
                     •  Information representation: Numbers in base 2, 8, 16, binary addition
                     •  Strings: ASCII, UTF8, UTF32, ISCII (Indian Script Code), Unicode
                     •  Basic concepts of flow chart
                     •  Concept of Compiler & Interpreter
                     •  Running a program: Notion of an operating system, how an operating system runs a program, idea of 
                       loading, operating system as a resource manager.
                     •  Concept of cloud computing, cloud (public/private), introduction to parallel computing.
              Unit 2:  COMPUTATIONAL THINKING AND PROGRAMMING
                      Basics of Computational Thinking: Decomposition, Pattern Recognition/Data Representation, Generalization/ 
                      Data Abstraction and algorithm.
                      Familiarization with the basics of Python programming: a simple “hello world” program, process of writing a 
                      program (Interactive & Script mode), running it, and print statements; simple data types: integer, float, string.
                     •  Features of Python, Python Character Set, Token & Identifiers, Keywords, Literals, Delimiters, Operators.
                     •  Comments: (Single line & Multiline/Continuation statements), Clarity & Simplification of expression.
                     •  Introduce the notion of a variable and methods to manipulate it (concept of L-value and R-value even if 
                       not taught explicitly).
                     •  Knowledge of data types and operators: accepting input from the console, assignment statement, 
                       expressions, operators and their precedence.
                     •  Operators & types: Binary operators—Arithmetic operators, Relational operators, Logical operators, 
                       Augmented Assignment operators.
                     •  Conditional statements: if, if-else, if-elif-else; simple programs: e.g.: absolute value, sort 3 numbers and 
                       divisibility.
                     •  Notion of iterative computation and control flow: for(range(), len()), while, flow charts, suggested programs: 
                       interest calculation and factorials, etc.
                     •  Idea of debugging: errors and exceptions; debugging: pdb, break points.
                     •  Lists, tuples and dictionary: finding the maximum, minimum, mean; linear search on list/tuple of numbers 
                       and counting the frequency of elements in a list using a dictionary. Introduce the notion of accessing 
                       elements in a collection using numbers and names.
                     •  Sorting algorithm: bubble and insertion sort; count the number of operations while sorting.
                     •  Strings: Traversing, compare, concat, substring.
                     •  Introduction to Python modules: Importing math [sqrt, cell, floor, pow, fabs, sin, cos, tan, random (random, 
                       randint, randrange), statistics (mean, median, mode)] modules.