ComputerScience(083)-XI

 

3. Unit wise Syllabus 

Unit 1: Computer Systems and Organisation 

● Basic computer organisation: Introduction to Computer System, hardware, software, input device, output device, CPU, memory (primary, cache and secondary), units of memory (bit, byte, KB, MB, GB, TB, PB) 

● Types of software: System software (Operating systems, system utilities, device drivers), programming tools and language translators (assembler, compiler, and interpreter), application software 

● Operating System(OS): functions of the operating system, OS user interface 

● Boolean logic: NOT, AND, OR, NAND, NOR, XOR, NOT, truth tables and De Morgan’s laws, Logic circuits 

● Number System: Binary, Octal, Decimal and Hexadecimal number system; conversion between number systems 

● Encoding Schemes: ASCII, ISCII, and Unicode (UTF8, UTF32) 

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Detailed Notes on Basic Computer Organisation

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1. Introduction to Computer System

A computer system is composed of two essential components:

• Hardware: The physical, tangible elements of the computer system.
• Software: The intangible instructions and programs that tell the hardware how to function.

The computer system takes input, processes it using its hardware and software, and provides output. The system also involves memory for temporary and permanent data storage.

Example:

• Input: You type a message on your keyboard (input device).
• Processing: The CPU processes the input using the operating system and other software.
• Output: The message is displayed on the monitor (output device).

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2. Hardware Components

The hardware refers to all the physical components of a computer. Key categories of hardware include:

Major Categories of Hardware:

• Input Devices: Hardware that allows users to enter data into the system.

  • Keyboard: Types text, numbers, and commands.
  • Mouse: Allows interaction with the computer's graphical interface (clicking, dragging).
  • Scanner: Converts physical images and text into digital data for processing.
  • Microphone: Captures sound (e.g., voice) to input into the system.

• Output Devices: Hardware that displays or presents data from the computer.

  • Monitor: Displays visual information (text, images, videos).
  • Printer: Converts digital information into printed format (physical).
  • Speakers: Output sound, such as music or speech.

• Central Processing Unit (CPU): The “brain” of the computer, which performs operations based on the instructions received.

  • Control Unit (CU): Manages the flow of instructions and data within the CPU and between other components of the computer.
  • Arithmetic Logic Unit (ALU): Performs mathematical calculations (e.g., addition, subtraction) and logic operations (e.g., AND, OR).
  • Registers: Small, high-speed memory areas within the CPU used to store data temporarily during processing.

• Storage Devices: Permanent storage for data.

  • Hard Disk Drive (HDD): A traditional, magnetic storage device used to store data permanently.
  • Solid-State Drive (SSD): A faster, more reliable storage device with no moving parts compared to an HDD.
  • USB Flash Drive: A portable, external storage device often used for transferring data between computers.

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3. Software

Software is a set of programs and instructions that direct the hardware on what actions to take. Software can be categorized into two main types:

Categories of Software:

• System Software: These are essential programs that help the computer run. The operating system (OS) is a prime example.

  • Operating System (OS): Manages the computer's hardware and software resources, such as memory, CPU, and input/output devices.
    • Example: Windows, macOS, Linux.
  • Device Drivers: Small programs that allow the OS to communicate with hardware components like printers, graphics cards, and network adapters.

• Application Software: Programs designed to perform specific tasks for users.

  • Example: Microsoft Word for word processing, Google Chrome for web browsing, Adobe Photoshop for image editing.

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4. Input Devices

Input devices are hardware components that allow the user to interact with the computer and provide data for processing.

Examples of Input Devices:

• Keyboard: Used to input text and commands into the computer.
  • Example: Typing a document or entering commands into a terminal.
• Mouse: Used to point, click, and interact with on-screen elements.
  • Example: Clicking an icon to open an application.
• Scanner: Digitizes physical documents and images into digital format for use by the computer.
  • Example: Scanning a photo to send it via email.
• Microphone: Captures audio input, converting sound to digital form.
  • Example: Recording a voice memo or a podcast.

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5. Output Devices

Output devices display or provide the results of computer processing. They convert the processed data into forms understandable by the user.

Examples of Output Devices:

• Monitor: Displays visual output, including text, images, and videos.
  • Example: Watching a movie on the screen or reviewing a document.
• Printer: Produces hard copies of digital documents or images on paper.
  • Example: Printing a document to submit in class or at work.
• Speakers: Provide audio output.
  • Example: Listening to music or hearing a notification sound.

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6. Central Processing Unit (CPU)

The CPU is the main unit of the computer that performs all processing and manages the execution of instructions.

Components of the CPU:

• Control Unit (CU): Directs the flow of data and instructions between the CPU and other components of the system.
• Arithmetic Logic Unit (ALU): Performs mathematical and logical operations.
  • Example: Calculating 5 + 3 using the ALU’s arithmetic capabilities.
• Registers: Small storage locations within the CPU to hold data during processing.

Example:

When you open a software program, the CPU is responsible for processing the instructions required to launch the program, loading it into memory, and managing its execution.

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7. Memory

Memory is used to store data temporarily or permanently, and can be categorized based on its speed and volatility.

Types of Memory:

• Primary Memory (RAM): Temporary, volatile storage used to store data that the CPU is actively processing.
  • Example: Opening a web browser loads the browser into RAM for quick access by the CPU.
• Cache Memory: A small, high-speed memory located close to the CPU that stores frequently accessed data and instructions for faster processing.
  • Example: Storing recently accessed web pages for faster loading when revisited.
• Secondary Memory: Permanent storage for data, such as hard drives, SSDs, and USB drives.
  • Example: Saving a document on your hard drive for future use.

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8. Units of Memory

Memory and storage are measured in units that represent different quantities of data. These units help us understand the size and capacity of storage devices and memory.

Units of Memory:

• Bit (b): The smallest unit of data, either 0 or 1 (binary).
  • Example: A bit could represent a binary choice (on/off, true/false).
• Byte (B): 8 bits, typically representing one character of data.
  • Example: A single letter, such as "A," is stored in 1 byte.
• Kilobyte (KB): 1,024 bytes.
  • Example: A small text file might be around 10 KB.
• Megabyte (MB): 1,024 KB (1,048,576 bytes).
  • Example: A high-resolution image might take up about 3 MB.
• Gigabyte (GB): 1,024 MB (1,073,741,824 bytes).
  • Example: A full-length HD movie can be around 2-5 GB.
• Terabyte (TB): 1,024 GB (1,099,511,627,776 bytes).
  • Example: A modern hard drive might have a storage capacity of 1 TB.
• Petabyte (PB): 1,024 TB (1,125,899,906,842,624 bytes).
  • Example: Large data centers may store information in the PB range.

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Summary Example:

When you browse the web:

1. Input: You use the mouse and keyboard to type a website URL.
2. CPU: The CPU processes the URL and retrieves the website's data from storage.
3. Primary Memory: The website is loaded into RAM for quick access.
4. Cache: Frequently used data from the website may be stored in cache memory for faster future access.
5. Output: The monitor displays the website content, and the speakers output any audio from the site.
   

 

Types of Software

Software is a collection of instructions or programs that tell the hardware how to perform specific tasks. There are three main categories of software: System Software, Programming Tools and Language Translators, and Application Software.

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1. System Software

System software is the set of programs that control and manage the hardware components of the computer. It helps the computer to function and provides a platform for running other software (applications).

Key Types of System Software:

1. Operating Systems (OS):

   • An Operating System (OS) is the primary software that manages computer hardware and software resources. It acts as an intermediary between users and the computer hardware.

   Examples of Operating Systems:

   • Windows: A popular OS for personal computers that allows users to perform tasks like browsing the internet, playing games, and managing files.
   • macOS: The OS used by Apple’s computers, known for its sleek interface and integration with Apple’s ecosystem.
   • Linux: A free, open-source OS widely used for servers and by developers. Examples of Linux distributions include Ubuntu, Fedora, and Debian.
   • Android: The OS used by most smartphones and tablets, which is based on the Linux kernel.
   • iOS: The OS for iPhones and iPads developed by Apple.

   Functions of the OS:

   • Manages memory and storage.
   • Manages input/output devices (e.g., keyboard, mouse, printer).
   • Provides a user interface for interaction (e.g., graphical interface like Windows or command-line interface like Linux).

2. System Utilities:

   • System utilities are programs that help maintain, manage, and optimize the system. They often perform tasks that the OS does not handle directly.

   Examples of System Utilities:

   • Antivirus software: Protects the computer from viruses and malware. Example: Norton, McAfee.
   • Disk cleanup tools: Help remove unnecessary files and optimize system storage. Example: Disk Cleanup in Windows.
   • Backup utilities: Backup and restore important data. Example: Windows Backup, Time Machine for macOS.

3. Device Drivers:

   • A device driver is a software that allows the operating system to communicate with hardware devices, such as printers, graphics cards, and network adapters.

   Examples of Device Drivers:

   • Printer Driver: Lets your computer communicate with and send print jobs to the printer.
   • Graphics Driver: Allows the computer to communicate with the graphics card, ensuring images and videos are rendered correctly on the screen.
   • Network Driver: Allows your computer to connect to a network, such as Wi-Fi or Ethernet.

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2. Programming Tools and Language Translators

Programming tools and language translators are types of system software that help developers write, compile, and execute programs.

Types of Programming Tools:

1. Assembler:

   • An assembler is a tool that converts assembly language (a low-level programming language) into machine code (binary instructions that the computer’s CPU can execute directly).

   Example:

   • If a programmer writes code in Assembly language (such as MOV AL, 30), the assembler will translate this into machine code that the CPU can understand.

2. Compiler:

   • A compiler is a program that translates high-level programming languages (like C, Java, or Python) into machine code that the computer can execute.
   • The entire code is translated at once, and the output is a separate machine code file.

   Example:

   • A programmer writes code in C programming language (e.g., printf("Hello World");), and the compiler translates it into machine code that can run on the computer. The program can then be executed directly.

3. Interpreter:

   • An interpreter also translates high-level programming languages into machine code, but it does this line-by-line, executing the program as it translates.
   • Unlike a compiler, which creates a separate machine code file, an interpreter runs the program immediately.

   Example:

   • Python is an interpreted language. If you write print("Hello World") in Python, the interpreter will immediately translate and run that line without creating a separate machine code file.
   • JavaScript, used in web development, is also interpreted by the browser’s JavaScript engine.

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3. Application Software

Application software refers to programs designed to perform specific tasks for the user. These programs run on top of the system software (like the operating system) and help the user complete a variety of tasks.

Key Types of Application Software:

1. Productivity Software:

   • Productivity software includes programs used to create, edit, and manage documents, spreadsheets, presentations, and more.

   Examples:

   • Microsoft Word: A word processing program used for creating documents.
   • Microsoft Excel: A spreadsheet program used for organizing data, performing calculations, and creating graphs.
   • Google Docs: A cloud-based word processor, similar to Microsoft Word, used for creating and editing documents online.
   • PowerPoint: A presentation software used to create slideshows, often for business or educational presentations.

2. Media Software:

   • Media software includes programs used for creating, editing, and playing media files, such as music, videos, and images.

   Examples:

   • Adobe Photoshop: Used for editing and manipulating images and photos.
   • Windows Media Player: A program used for playing audio and video files.
   • VLC Media Player: A versatile media player that can play various audio and video formats.

3. Web Browsers:

   • Web browsers are programs that allow users to access and interact with websites on the internet.

   Examples:

   • Google Chrome: A popular web browser known for its speed and simplicity.
   • Mozilla Firefox: An open-source web browser focused on privacy and security.
   • Microsoft Edge: A web browser from Microsoft that comes pre-installed on Windows computers.

4. Gaming Software:

   • Gaming software includes programs designed for entertainment, usually involving video games.

   Examples:

   • Minecraft: A popular sandbox game where players can build and explore virtual worlds.
   • FIFA: A football/soccer simulation video game series developed by EA Sports.

5. Database Software:

   • Database software helps users store, manage, and retrieve large amounts of data in an organized manner.

   Examples:

   • Microsoft Access: A database management system used to create databases and run queries.
   • Oracle Database: A powerful database management system used by businesses to manage large volumes of data.

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Summary of Software Types with Examples

Software Type	Description	Examples
System Software	Software that manages hardware and provides a platform for running applications.	Operating Systems (Windows, macOS, Linux), Device Drivers, System Utilities (Antivirus, Backup tools)
Programming Tools	Tools that help programmers write, compile, and execute programs.	Assembler, Compiler, Interpreter
Application Software	Programs designed for specific tasks that users want to perform.	Microsoft Word, Google Chrome, VLC Player, Photoshop, Minecraft

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Conclusion

In summary given by Rajesh Upadhyay, software is vital to make hardware functional and allow users to perform tasks on a computer. System software ensures the hardware works correctly, programming tools and language translators help developers write programs, and application software allows users to do things like create documents, browse the web, or play games.

 

Operating System (OS)

An Operating System (OS) is essential software that acts as an intermediary between the computer's hardware and the user. It manages all hardware and software resources and enables users to interact with the computer in a meaningful way. The OS ensures that everything runs smoothly, providing essential functions like managing files, memory, and hardware devices.

Functions of the Operating System

The operating system performs several critical functions to ensure that a computer works efficiently. Here are the main functions:

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1. Process Management

The OS manages processes running on the computer. A process is a program that is being executed, and the OS makes sure these processes are scheduled and run efficiently.

• Task Scheduling: The OS decides which process gets to use the CPU and for how long. This is called scheduling.

• Multitasking: The OS enables the computer to run multiple applications at once by rapidly switching between them, so it seems like they are running simultaneously.

  Example: While you're writing an email, the OS ensures that your web browser and music player also run in the background without interruptions.

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2. Memory Management

The OS is responsible for managing the computer's memory (RAM). It keeps track of memory allocation to different programs, making sure that each program gets enough memory to function properly and that memory is freed up when no longer needed.

• Allocating Memory: The OS assigns memory to different running processes, ensuring that no process uses more memory than it should.

• Virtual Memory: If the physical memory (RAM) is full, the OS uses a part of the hard drive as virtual memory to extend the available memory space.

  Example: If you're running several programs at once and your computer's RAM is full, the OS may use part of your hard drive as virtual memory, so the programs don't crash.

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3. File System Management

The OS organizes and manages files on the computer. It creates and maintains a structure for storing and retrieving data in an efficient way. This is done through the file system.

• File Creation, Deletion, and Modification: The OS allows users and programs to create, delete, or modify files.

• File Organization: The OS stores files in directories (folders), allowing users to organize and access their data easily.

  Example: When you save a document in Microsoft Word, the OS handles storing that file in the correct location on your hard drive or SSD.

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4. Device Management

The OS manages all the hardware devices connected to the computer, such as printers, monitors, keyboards, and storage devices. It makes sure the devices function properly and efficiently.

• Device Drivers: The OS uses device drivers (special software programs) to communicate with the hardware.

• Input/Output Management: The OS controls the input (keyboard, mouse) and output (monitor, printer) devices, ensuring that data is sent and received correctly.

  Example: When you print a document, the OS sends the document data to the printer using the appropriate driver to ensure the printer works as expected.

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5. Security and Access Control

The OS ensures the security of the system by protecting it from unauthorized access and malicious software. It manages user accounts and permissions to ensure that only authorized users can access certain files and system resources.

• User Authentication: The OS verifies users by asking for usernames and passwords before granting access to the system.

• Permissions: The OS controls which users can access, modify, or delete files and settings.

  Example: When you log in to your computer, the OS checks your username and password to verify your identity and allow you to access your desktop and files.

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6. Communication Between Software

The OS provides the necessary functions for different software applications to communicate with each other and with the hardware. This ensures that multiple programs can run together and share resources without interfering with one another.

• Inter-Process Communication (IPC): The OS allows programs to communicate and share data in a safe and controlled way.

  Example: If you're using a video editing program and a music player, the OS ensures they can share resources like memory and CPU without causing crashes.

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7. User Interface (UI) Management

The OS provides the User Interface (UI), which is the way users interact with the computer. The user interface could be either Command-Line Interface (CLI) or Graphical User Interface (GUI), depending on the OS.

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OS User Interface (UI)

The User Interface (UI) is how users interact with the operating system. It provides the means to input commands or interact with programs and files.

Types of User Interfaces

1. Command-Line Interface (CLI)

   • The Command-Line Interface (CLI) is a text-based interface where users type commands to execute actions.
   • It is powerful and efficient, but requires knowledge of specific commands.

   Example:

   • In Linux, you might use a CLI to list files with the command: ls.
   • Windows also has Command Prompt, where you type commands like dir to display a directory of files.

2. Graphical User Interface (GUI)

   • A Graphical User Interface (GUI) uses visuals like icons, buttons, and windows, making it much easier for users to interact with the computer.
   • Most modern operating systems like Windows, macOS, and Linux (with desktop environments like GNOME or KDE) offer GUIs.

   Example:

   • On Windows, you can click on icons like File Explorer, Recycle Bin, or the Start menu to open programs or manage files.
   • On macOS, the Dock allows you to access apps with a click, and the Finder window lets you organize files through drag-and-drop.

3. Touch User Interface (TUI)

   • A Touch User Interface (TUI) is designed for touchscreen devices. It allows users to interact with the system by tapping or swiping on the screen.
   • This is common in smartphones and tablets running Android or iOS.

   Example:

   • On a smartphone, you tap an app icon to open it or swipe to switch between apps.

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Examples of Operating Systems with Different UIs

1. Windows:
   • GUI-based OS with a Start Menu, taskbar, and windowed applications. Users can interact with icons, windows, and menus using a mouse and keyboard.
2. macOS:
   • A GUI-based OS with a Dock and Finder, designed to be simple and user-friendly. Common features include Spotlight Search and Mission Control.
3. Linux (Ubuntu):
   • A GUI-based OS that also provides a CLI option for more advanced users. The GNOME desktop environment is widely used.
4. Android:
   • A touch-based UI designed for smartphones and tablets. Users interact with touch gestures and access apps through a home screen.

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Conclusion

In summary, the Operating System (OS) is the backbone of any computer system. It manages everything from hardware resources to user interactions, ensuring that the computer operates efficiently and securely. The OS enables multitasking, handles memory and file systems, manages devices, and provides an interface for users to interact with the computer.

The User Interface (UI) allows users to interact with the OS through visual elements or text commands. Whether it’s a graphical interface (GUI), command-line interface (CLI), or touch interface, the OS provides the necessary tools for users to perform tasks with ease.

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Boolean Logic

Boolean logic is a branch of mathematics and algebra that deals with true and false values. It’s fundamental in computer science, digital circuits, and programming because it forms the basis for all decision-making in computing systems. Boolean logic uses binary values (0 and 1), where:

• 0 represents false
• 1 represents true

Basic Boolean Operations (Gates)

In Boolean logic, there are several basic operations, called gates, that combine or modify binary values. Each gate performs a logical operation based on one or more inputs and produces a single output.

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1. NOT Gate (Inverter)

• The NOT gate takes a single input and inverts it, meaning it changes true (1) to false (0) and false (0) to true (1).

Symbol: ¬A or A'

Input (A)	Output (NOT A)
0	1
1	0

Example:
If the input A is 1, the output will be 0.
If the input A is 0, the output will be 1.

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2. AND Gate

• The AND gate gives a true (1) output only if both inputs are true (1). If any input is false (0), the output will be false (0).

Symbol: A ⋅ B

Input A	Input B	Output (A AND B)
0	0	0
0	1	0
1	0	0
1	1	1

Example:
If input A = 1 and input B = 1, the output will be 1.
If input A = 0 and input B = 1, the output will be 0.

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3. OR Gate

• The OR gate gives a true (1) output if at least one input is true (1). If both inputs are false (0), the output will be false (0).

Symbol: A + B

Input A	Input B	Output (A OR B)
0	0	0
0	1	1
1	0	1
1	1	1

Example:
If input A = 0 and input B = 1, the output will be 1.
If input A = 0 and input B = 0, the output will be 0.

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4. NAND Gate (NOT AND)

• The NAND gate is the opposite of the AND gate. It gives a false (0) output only when both inputs are true (1). In all other cases, the output will be true (1).

Symbol: A ↑ B

Input A	Input B	Output (A NAND B)
0	0	1
0	1	1
1	0	1
1	1	0

Example:
If input A = 1 and input B = 1, the output will be 0.
If input A = 0 and input B = 1, the output will be 1.

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5. NOR Gate (NOT OR)

• The NOR gate is the opposite of the OR gate. It gives a true (1) output only when both inputs are false (0). If any input is true (1), the output will be false (0).

Symbol: A ↓ B

Input A	Input B	Output (A NOR B)
0	0	1
0	1	0
1	0	0
1	1	0

Example:
If input A = 0 and input B = 0, the output will be 1.
If input A = 1 and input B = 0, the output will be 0.

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6. XOR Gate (Exclusive OR)

• The XOR (Exclusive OR) gate gives a true (1) output when one and only one input is true (1). If both inputs are the same (either both 0 or both 1), the output will be false (0).

Symbol: A ⊕ B

Input A	Input B	Output (A XOR B)
0	0	0
0	1	1
1	0	1
1	1	0

Example:
If input A = 1 and input B = 0, the output will be 1.
If input A = 1 and input B = 1, the output will be 0.

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Truth Tables

Truth tables are a way of showing how each possible combination of inputs affects the output of a logic gate. Each gate has its own truth table, as demonstrated above.

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7. De Morgan's Laws

De Morgan's laws are two important rules in Boolean algebra that help simplify logical expressions. These laws describe how NOT operations interact with AND and OR operations.

1. First De Morgan's Law:

   • The negation of an AND operation is equivalent to the OR operation between the negated inputs.
   • NOT (A AND B) = (NOT A) OR (NOT B)

   Example:

   • If A = 1 and B = 0, NOT (A AND B) = NOT (1 AND 0) = NOT 0 = 1.
   • (NOT A) OR (NOT B) = (NOT 1) OR (NOT 0) = 0 OR 1 = 1.

   Both sides are equal, which confirms the law.

2. Second De Morgan's Law:

   • The negation of an OR operation is equivalent to the AND operation between the negated inputs.
   • NOT (A OR B) = (NOT A) AND (NOT B)

   Example:

   • If A = 0 and B = 1, NOT (A OR B) = NOT (0 OR 1) = NOT 1 = 0.
   • (NOT A) AND (NOT B) = (NOT 0) AND (NOT 1) = 1 AND 0 = 0.

   Both sides are equal, which confirms the law.

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Logic Circuits

A logic circuit is a network of gates that are connected together to perform specific tasks based on Boolean logic. These circuits are the building blocks of digital systems like computers, calculators, and smartphones.

• Basic Circuits: A basic logic circuit might involve one or more gates combined to perform a specific operation.

  • Example: A circuit might use an AND gate followed by a NOT gate to create a NAND gate.

• Complex Circuits: In more complex systems, logic circuits are used to perform calculations, store data, and control operations in processors.

  • Example: A half adder is a simple logic circuit used to add two binary digits (bits), consisting of an XOR gate for the sum and an AND gate for the carry bit.

Example of a Half Adder:

Input A	Input B	Sum	Carry
0	0	0	0
0	1	1	0
1	0	1	0
1	1	0	1

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Conclusion

In summary, Boolean logic and logic gates form the foundation of digital electronics and computer systems. By using logical operations like AND, OR, NOT, XOR, NAND, and NOR, computers can perform complex calculations, make decisions, and process information. De Morgan's laws provide a way to simplify and manipulate Boolean expressions. These logic gates and laws are key components in building logic circuits, which are used in everything from basic devices like calculators to complex systems like computers and processors.

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Number System

A number system is a way of expressing numbers using a consistent set of symbols or digits. There are several number systems, but the most common ones in computing are binary, octal, decimal, and hexadecimal. Let’s go over each of them.

1. Binary Number System

The binary number system uses only two digits: 0 and 1. It’s the foundation of all computer systems because computers operate using electrical signals that are either on or off (represented as 1 and 0).

• Base: 2 (because it uses two digits)
• Example: 1011 (binary)

How it works:
Each digit in a binary number represents an increasing power of 2, starting from the right (least significant bit). So, the binary number 1011 is calculated as:

$1 \times 2^3 + 0 \times 2^2 + 1 \times 2^1 + 1 \times 2^0$ $1 \times 8 + 0 \times 4 + 1 \times 2 + 1 \times 1 = 8 + 0 + 2 + 1 = 11$ (in decimal)

So, 1011 in binary equals 11 in decimal.

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2. Octal Number System

The octal number system uses eight digits: 0, 1, 2, 3, 4, 5, 6, 7.

• Base: 8 (because it uses eight digits)
• Example: 257 (octal)

How it works:
Each digit in an octal number represents an increasing power of 8. For example, the octal number 257 can be converted to decimal as follows:

$2 \times 8^2 + 5 \times 8^1 + 7 \times 8^0$ $2 \times 64 + 5 \times 8 + 7 \times 1 = 128 + 40 + 7 = 175$ (in decimal)

So, 257 in octal equals 175 in decimal.

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3. Decimal Number System

The decimal number system is the number system we use in everyday life. It uses ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

• Base: 10 (because it uses ten digits)
• Example: 345 (decimal)

This is the most familiar system and is based on powers of 10.

How it works:
Each digit in a decimal number represents an increasing power of 10. For example, the decimal number 345 can be broken down as:

$3 \times 10^2 + 4 \times 10^1 + 5 \times 10^0$ $3 \times 100 + 4 \times 10 + 5 \times 1 = 300 + 40 + 5 = 345$

So, 345 in decimal is just 345.

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4. Hexadecimal Number System

The hexadecimal number system uses sixteen digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F. In hexadecimal, A represents 10, B represents 11, C represents 12, D represents 13, E represents 14, and F represents 15.

• Base: 16 (because it uses sixteen digits)
• Example: 3F (hexadecimal)

How it works:
Each digit in a hexadecimal number represents an increasing power of 16. The hexadecimal number 3F can be converted to decimal as follows:

$3 \times 16^1 + F \times 16^0$ $3 \times 16 + 15 \times 1 = 48 + 15 = 63$ (in decimal)

So, 3F in hexadecimal equals 63 in decimal.

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Conversion Between Number Systems

Now let’s look at how to convert between different number systems. We’ll focus on binary, decimal, octal, and hexadecimal conversions.

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1. Decimal to Binary Conversion

To convert a decimal number to binary, divide the decimal number by 2 and write down the remainder for each division. Continue dividing until the quotient is 0, then read the remainders from bottom to top.

Example: Convert 13 (decimal) to binary.

1. 13 ÷ 2 = 6 remainder 1
2. 6 ÷ 2 = 3 remainder 0
3. 3 ÷ 2 = 1 remainder 1
4. 1 ÷ 2 = 0 remainder 1

Reading the remainders from bottom to top, we get 1101 (binary).

So, 13 in decimal is 1101 in binary.

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2. Binary to Decimal Conversion

To convert a binary number to decimal, multiply each digit of the binary number by the corresponding power of 2 and add up the results.

Example: Convert 1101 (binary) to decimal.

$1 \times 2^3 + 1 \times 2^2 + 0 \times 2^1 + 1 \times 2^0$ $1 \times 8 + 1 \times 4 + 0 \times 2 + 1 \times 1 = 8 + 4 + 0 + 1 = 13$ (decimal)

So, 1101 in binary is 13 in decimal.

---

3. Decimal to Hexadecimal Conversion

To convert a decimal number to hexadecimal, divide the decimal number by 16 and write down the remainder. Continue dividing until the quotient is 0, then read the remainders from bottom to top. If a remainder is greater than 9, use the corresponding letter (A, B, C, etc.).

Example: Convert 255 (decimal) to hexadecimal.

1. 255 ÷ 16 = 15 remainder 15 → F
2. 15 ÷ 16 = 0 remainder 15 → F

Reading the remainders from bottom to top, we get FF (hexadecimal).

So, 255 in decimal is FF in hexadecimal.

---

4. Hexadecimal to Decimal Conversion

To convert a hexadecimal number to decimal, multiply each digit of the hexadecimal number by the corresponding power of 16 and add up the results.

Example: Convert FF (hexadecimal) to decimal.

$F \times 16^1 + F \times 16^0$
Where F = 15.

$15 \times 16 + 15 \times 1 = 240 + 15 = 255$ (decimal)

So, FF in hexadecimal is 255 in decimal.

---

5. Binary to Octal Conversion

To convert from binary to octal, group the binary digits in sets of three (from right to left), then convert each group to its octal equivalent.

Example: Convert 101101 (binary) to octal.

Group the binary digits:
101 101.

Now convert each group:
101 = 5
101 = 5

So, 101101 in binary is 55 in octal.

---

6. Octal to Binary Conversion

To convert from octal to binary, convert each octal digit into a 3-bit binary number.

Example: Convert 55 (octal) to binary.

5 in octal = 101 in binary
5 in octal = 101 in binary

So, 55 in octal is 101101 in binary.

---

Conclusion

In summary, different number systems (binary, octal, decimal, and hexadecimal) are used in different contexts in computing. Binary is used at the most fundamental level (since computers work with binary data), decimal is the most familiar for everyday use, octal and hexadecimal are used in computing for more compact and easier representation of binary data.

Understanding how to convert between these number systems is essential in areas such as programming, computer science, and electronics.

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Encoding Schemes: ASCII, ISCII, and Unicode (UTF-8, UTF-32)

What is Encoding?

Encoding is the process of converting characters into a specific format so they can be easily stored or transmitted by computers. Different encoding schemes allow computers to represent text in various languages and scripts.

---

1. ASCII (American Standard Code for Information Interchange)

ASCII is one of the earliest encoding schemes and is still widely used today. It represents English characters and some control characters as numbers, ranging from 0 to 127.

• Bit-length: 7 bits (extended ASCII uses 8 bits)
• Character Set: Includes English alphabets (uppercase and lowercase), digits, punctuation marks, and special characters (like space, newline, etc.).
• Range: 0 to 127 (0–31 are control characters, and 32–127 are printable characters).

Example:

• 'A' in ASCII is represented as 65 in decimal or 01000001 in binary.
• 'a' in ASCII is represented as 97 in decimal or 01100001 in binary.
• '1' in ASCII is 49 in decimal or 00110001 in binary.
• The space character ' ' is represented by 32 in decimal or 00100000 in binary.

ASCII Table (Partial):

Character	ASCII Decimal	ASCII Binary
A	65	01000001
a	97	01100001
1	49	00110001
Space	32	00100000

---

2. ISCII (Indian Script Code for Information Interchange)

ISCII is an encoding scheme developed in India to represent different Indian languages and scripts, such as Hindi, Tamil, Bengali, etc., using a standard computer format. ISCII was designed to work with 8-bit encoding (one byte per character).

• Bit-length: 8 bits (1 byte)
• Character Set: It includes characters for languages like Hindi, Bengali, Gujarati, Tamil, etc. It also includes some special characters, numerals, and punctuation marks.

How ISCII Works: ISCII uses a base character set for common characters across languages (such as vowels and consonants), and then different combination schemes for the various scripts of different Indian languages.

Example:

• The character अ in Hindi is represented by a unique byte value in ISCII, such as 0x90.
• The character ि (diacritic) in Hindi might be represented as 0xB2.

While ISCII is now largely replaced by Unicode, it was an essential encoding scheme for representing Indian languages in computing in the past.

---

3. Unicode (UTF-8 and UTF-32)

Unicode is a modern character encoding scheme that aims to represent every character in every language used in the world. Unlike ASCII, which is limited to 128 characters, Unicode includes tens of thousands of characters, supporting almost every script in existence today.

Unicode can be implemented using different encoding forms, the most common being UTF-8 and UTF-32.

---

UTF-8 (Unicode Transformation Format - 8 bits)

UTF-8 is a variable-length encoding system used to encode characters in Unicode. It is the most commonly used Unicode encoding format for the web, as it is both space-efficient and compatible with ASCII.

• Bit-length: Variable (from 8 bits to 32 bits per character, depending on the character).
• Compatible with ASCII: Characters from the ASCII set (0–127) are encoded using just one byte in UTF-8, making it backward compatible with ASCII.
• Multi-byte Encoding: Characters outside the ASCII range are represented using 2 to 4 bytes.

How it works:

• Characters from 0 to 127 are encoded in 1 byte (same as ASCII).
• Characters from 128 to 2047 are encoded in 2 bytes.
• Characters from 2048 to 65535 are encoded in 3 bytes.
• Characters from 65536 onwards (i.e., characters in supplementary planes) are encoded in 4 bytes.

Example:

• The character 'A' (ASCII) has the same value in UTF-8: 65 (1 byte).
• The character 'न' (Hindi) in UTF-8 is represented as 0xE0 0xA8 0xA8 (3 bytes).
• The character '😊' (Emoji) in UTF-8 is represented as 0xF0 0x9F 0x98 0x8A (4 bytes).

UTF-8 Table (Partial):

Character	UTF-8 (Decimal)	UTF-8 (Hex)	UTF-8 (Bytes)
A	65	41	41
न	234, 168, 168	E0 A8 A8	E0 A8 A8
😊	240, 159, 152, 138	F0 9F 98 8A	F0 9F 98 8A

---

UTF-32 (Unicode Transformation Format - 32 bits)

UTF-32 is another encoding form of Unicode that uses a fixed 4 bytes (32 bits) for each character, regardless of the character's value. It is not space-efficient but can be useful when you need to quickly access any character without having to decode multiple bytes.

• Bit-length: 32 bits (4 bytes) per character.
• Fixed-length Encoding: Every character is represented by 4 bytes.
• Unicode Compatibility: Since it represents all characters in 4 bytes, UTF-32 can easily encode any Unicode character, including those from supplementary planes.

How it works:

• Each character, regardless of whether it's a basic or supplementary character, is always encoded in 4 bytes.

Example:

• The character 'A' in UTF-32 is represented as 0x00000041 (4 bytes).
• The character 'न' in UTF-32 is represented as 0x00000190 (4 bytes).
• The character '😊' in UTF-32 is represented as 0x0001F60A (4 bytes).

UTF-32 Table (Partial):

Character	UTF-32 (Hex)	UTF-32 (Bytes)
A	0x00000041	00 00 00 41
न	0x00000190	00 00 01 90
😊	0x0001F60A	00 00 1F 60 0A

---

Comparison of ASCII, ISCII, and Unicode

Feature	ASCII	ISCII	Unicode (UTF-8, UTF-32)
Bit-Length	7 bits (or 8 bits in extended ASCII)	8 bits (1 byte)	8 bits (UTF-8) or 32 bits (UTF-32)
Character Set	Limited to English alphabets and symbols	Indian languages and scripts	All languages and scripts
Compatibility	Compatible with English texts	Focuses on Indian languages	Supports all scripts worldwide
Storage	Compact for English text	Compact for Indian languages	UTF-8: Compact for ASCII, UTF-32: Large but fast
Usage	General text encoding	Indian language encoding	Global standard for multi-language text encoding

---

Conclusion

• ASCII is simple and efficient for representing English characters but is very limited in scope.
• ISCII was specifically designed to handle Indian scripts, but it’s now less widely used as Unicode has taken over.
• Unicode (including UTF-8 and UTF-32) is the universal encoding standard, allowing representation of every character in any language, including emojis and symbols. UTF-8 is more compact and commonly used, especially on the web, while UTF-32 is useful when fixed-length encoding is needed for fast character access.

These encoding schemes help computers represent, store, and transmit textual data across different systems, ensuring global compatibility for digital text.

___________________________________________________________________ 

Unit 2: Computational Thinking and Programming - I 

● Introduction to Problem-solving: Steps for Problem-solving (Analyzing the problem, developing an algorithm, coding, testing, and debugging), representation of algorithms using flowchart and pseudocode, decomposition 

● Familiarization with the basics of Python programming: Introduction to Python, Features of Python, executing a simple “hello world" program, execution modes: interactive mode and script mode, Python character set, Python tokens( keyword, identifier, literal, operator, punctuator), variables, concept of l-value and r-value, use of comments 

● Knowledge of data types: Number(integer, floating point,complex), boolean, sequence(string, list, tuple), None, Mapping(dictionary), mutable and immutable data types. 

● Operators: arithmetic operators, relational operators, logical operators, assignment operators, augmented assignment operators, identity operators (is, is not), membership operators (in not in) 

● Expressions, statement, type conversion, and input/output: precedence of operators, expression, evaluation of an expression, type-conversion (explicit and implicit conversion), accepting data as input from the console and displaying output. 

● Errors- syntax errors, logical errors, and run-time errors 

● Flow of Control: introduction, use of indentation, sequential flow, conditional and iterative flow 

● Conditional statements: if, if-else, if-elif-else, flowcharts, simple programs: e.g.: absolute value, sort 3 numbers and divisibility of a number. 

● Iterative Statement: for loop, range(), while loop, flowcharts, break and continue statements, nested loops, suggested programs: generating pattern, summation of series, finding the factorial of a positive number, etc. 

● Strings: introduction, string operations (concatenation, repetition, membership and slicing), traversing a string using loops, built-in functions/methods–len(), capitalize(), title(), lower(), upper(), count(), find(), index(), endswith(), startswith(), isalnum(), isalpha(), isdigit(), islower(), isupper(), isspace(),lstrip(), rstrip(), strip(), replace(), join(), partition(), split() 

● Lists: introduction, indexing, list operations (concatenation, repetition, membership and slicing), traversing a list using loops, built-in functions/methods–len(), list(), append(), extend(), insert(), count(), index(), remove(), pop(), reverse(), sort(), sorted(), min(), max(), sum(); nested lists, suggested programs: finding the maximum, minimum, mean of numeric values stored in a list; linear search on list of numbers and counting the frequency of elements in a list. 

● Tuples: introduction, indexing, tuple operations (concatenation, repetition, membership and slicing); built-in functions/methods – len(), tuple(), count(), index(), sorted(), min(), max(), sum(); tuple assignment, nested tuple; suggested programs: finding the minimum, maximum, mean of values stored in a tuple; linear search on a tuple of numbers, counting the frequency of elements in a tuple. 

● Dictionary: introduction, accessing items in a dictionary using keys, mutability of a dictionary (adding a new term, modifying an existing item), traversing a dictionary, built-in functions/methods – len(), dict(), keys(), values(), items(), get(), update(), del, clear(), fromkeys(), copy(), pop(), popitem(), setdefault(), max(), min(), sorted(); Suggested programs: count the number of times a character appears in a given string using a dictionary, create a dictionary with names of employees, their salary and access them. 

● Introduction to Python modules: Importing module using ‘import ’ and using from statement, importing math module (pi, e, sqrt(), ceil(), floor(), pow(), fabs(), sin(), cos(), tan()); random module (random(), randint(), randrange()), statistics module (mean(), median(), mode()). 

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Unit 2: Computational Thinking and Programming - I

This unit focuses on the fundamentals of problem-solving and introduces Python programming, including basic concepts, data types, control flow, and essential Python operations.

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Computational Thinking and Programming – I

Introduction to Problem-Solving

Easy English · Detailed explanations · Original examples · Exam-oriented notes

Syllabus Covered

1. Introduction to Problem-Solving

2. Steps for Problem-Solving

3. Analyzing the Problem

4. Developing an Algorithm

5. Coding

6. Testing and Debugging

7. Representation of Algorithms using Flowcharts and Pseudocode

8. Decomposition

1. Introduction to Problem-Solving

1.1 What is a Problem?

A problem is a situation in which we need to find an answer, solution, or way to achieve a particular goal.

Examples

• Finding the sum of two numbers.

• Calculating the average marks of a student.

• Checking whether a number is even or odd.

• Finding the largest number among three numbers.

• Preparing a school timetable.

1.2 What is Problem-Solving?

Problem-solving is a systematic process of understanding a problem, planning a solution, implementing it, and checking whether the solution works correctly.

In computer science, problem-solving means developing a logical and step-by-step solution that can be implemented using a computer.

Example: Finding the Sum of Two Numbers

Suppose we want to calculate the sum of 15 and 25.

PROBLEM

15 + 25 = ?

SOLUTION

40

To solve this problem using a computer, we need to provide clear instructions for adding the two numbers and displaying the result.

2. Steps for Problem-Solving

Problem-solving in programming generally involves five important steps.

1. Analyzing the Problem

Understand the problem and its requirements.

2. Developing an Algorithm

Prepare a step-by-step solution.

3. Coding

Convert the solution into program code.

4. Testing

Check whether the program works correctly.

5. Debugging

Find and correct errors in the program.

If an error is found during testing, the programmer corrects it and tests the program again.

3. Analyzing the Problem

3.1 Definition

Problem analysis is the process of understanding what a problem requires, what information is available, and what result is expected.

Before writing a program, we should identify three important components:

Input

The data given to the computer.

Example: Two numbers, 15 and 25.

Process

The operation performed on the input.

Example: Adding the two numbers.

Output

The result produced by the computer.

Example: The sum, 40.

3.2 Example: Calculate the Average of Three Marks

Suppose a student scores 70, 80 and 90 marks in three subjects.

Component	Description
Input	70, 80, 90
Process	Add the marks and divide the total by 3
Output	80

Formula:

$$\text{Average}=\frac{A+B+C}{3}$$

3.3 Importance of Problem Analysis

• Helps us understand the actual problem.

• Identifies the required inputs and expected outputs.

• Prevents unnecessary coding.

• Helps us plan the correct solution.

• Makes the program easier to develop and test.

4. Developing an Algorithm

4.1 What is an Algorithm?

An algorithm is a finite sequence of clear, ordered steps used to solve a problem or perform a task.

In simple words, an algorithm is a step-by-step plan for solving a problem.

4.2 Real-Life Example: Making a Cup of Tea

Algorithm:

1. Start.

2. Take water in a pan.

3. Heat the water.

4. Add tea leaves and sugar.

5. Add milk.

6. Boil the mixture.

7. Strain the tea into a cup.

8. Stop.

This is an example of an algorithm because it contains ordered steps to complete a task.

4.3 Algorithm to Add Two Numbers

Problem: Write an algorithm to input two numbers and display their sum.

Algorithm:

1. Start.

2. Input two numbers A and B.

3. Calculate SUM = A + B.

4. Display SUM.

5. Stop.

4.4 Characteristics of a Good Algorithm

Characteristic	Explanation
Input	An algorithm may accept zero or more inputs.
Output	It should produce at least one result.
Definiteness	Every step should be clear and unambiguous.
Finiteness	It must finish after a finite number of steps.
Effectiveness	Every step should be practical and executable.

Important Points

• An algorithm is a plan, not necessarily a computer program.

• It can be written in simple English or another understandable language.

• The same algorithm can be implemented in different programming languages.

5. Coding

5.1 Definition

Coding is the process of converting an algorithm or solution into instructions written in a programming language that a computer can execute.

A programmer writes code using programming languages such as Python, C++, Java or JavaScript.

5.2 Example: Python Program to Add Two Numbers

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))

total = a + b

print("Sum =", total)

Explanation of the Program

Code	Meaning
input()	Takes input from the user.
int()	Converts the input into an integer.
a + b	Adds the two numbers.
total	Stores the calculated sum.
print()	Displays the result.

Sample Output

Enter first number: 15
Enter second number: 25
Sum = 40

5.3 Important Terms

Programming Language: A language used to write instructions for a computer.

Program: A set of instructions written in a programming language to perform a task.

Programmer: A person who writes, tests and maintains computer programs.

6. Testing

6.1 Definition

Testing is the process of running a program with different inputs to check whether it produces the expected results.

Testing helps us identify errors and check whether a program satisfies its requirements.

6.2 Example: Testing a Sum Program

Suppose a program calculates the sum of two numbers.

We should test it with different input values.

Input A	Input B	Expected Output
10	20	30
5	7	12
0	8	8
-4	6	2

If the program gives the expected output for these test cases, it passes those particular tests.

However, passing a few tests does not guarantee that the program is completely error-free.

6.3 Types of Test Cases

1. Normal Test Case

Uses ordinary and expected input values.

Example: Adding 10 and 20.

2. Boundary Test Case

Checks values at the limits of the allowed input range.

Example: If marks must be between 0 and 100, test the values 0 and 100.

3. Invalid Input Test Case

Checks how a program handles input that is not allowed.

Example: Entering a negative number when only positive numbers are permitted.

6.4 Importance of Testing

• Helps identify errors.

• Checks whether the program meets its requirements.

• Verifies the correctness of output.

• Improves the reliability of software.

7. Debugging

7.1 Definition

Debugging is the process of identifying, locating and correcting errors in a computer program.

An error in a program is commonly called a bug.

7.2 Example 1: Syntax Error

Incorrect code:

print("Hello"

The closing parenthesis is missing.

Correct code:

print("Hello")

7.3 Example 2: Logical Error

Suppose we want to calculate the average of three numbers.

Incorrect code:

average = (a + b + c) / 2

The program may run, but the result will be incorrect because the total is divided by 2 instead of 3.

Correct code:

average = (a + b + c) / 3

7.4 Types of Errors

1. Syntax Error

An error caused by breaking the grammar or rules of a programming language.

Example: Missing a bracket or colon.

2. Runtime Error

An error that occurs while a program is running.

Example: Dividing a number by zero.

3. Logical Error

An error in the program's logic that causes it to produce an incorrect result.

Example: Dividing the sum of three numbers by 2 instead of 3.

7.5 Testing vs Debugging

Testing	Debugging
Checks whether the program works correctly.	Finds and corrects errors.
May reveal a bug.	Investigates the cause of a bug.
Focuses on checking program behaviour.	Focuses on correcting faulty code or logic.

Remember: Testing detects failures; debugging investigates and fixes their causes.

8. Representation of Algorithms

An algorithm can be represented in different ways. Two common methods are:

1. Flowchart

2. Pseudocode

These methods help programmers understand and plan a solution before writing the actual program.

9. Flowchart

9.1 Definition

A flowchart is a graphical representation of an algorithm using standard symbols connected by arrows to show the sequence of steps.

It helps us understand the logic of a program visually.

9.2 Common Flowchart Symbols

Oval / Ellipse

Indicates the beginning or end of an algorithm.

Rectangle

Represents a calculation or processing step.

Parallelogram

Represents taking input or displaying output.

Diamond

Represents a condition with possible branches such as Yes/No.

Arrow / Flow Line

Shows the direction and sequence of execution.

9.3 Example: Flowchart to Add Two Numbers

Flowchart for adding two numbers

Explanation

1. Start the process.

2. Take two numbers as input.

3. Add the numbers and store the result in SUM.

4. Display the value of SUM.

5. Stop the process.

10. Pseudocode

10.1 Definition

Pseudocode is an informal, structured way of describing the steps of an algorithm using simple English-like statements and programming-style instructions.

Pseudocode is not a programming language. It does not follow the exact syntax rules of Python, C++ or Java.

10.2 Example: Pseudocode to Add Two Numbers

BEGIN
    INPUT A, B
    SUM ← A + B
    PRINT SUM
END

Explanation

Statement	Meaning
BEGIN	Starts the algorithm.
INPUT A, B	Takes two numbers as input.
SUM ← A + B	Calculates and stores the sum.
PRINT SUM	Displays the result.
END	Finishes the algorithm.

Note: The symbol ← means assignment, that is, storing a value in a variable.

10.3 Pseudocode to Calculate Average

BEGIN
    INPUT A, B, C
    TOTAL ← A + B + C
    AVERAGE ← TOTAL / 3
    PRINT AVERAGE
END

If the inputs are 70, 80 and 90, the output will be 80.

10.4 Pseudocode to Check Even or Odd

BEGIN
    INPUT N

    IF N MOD 2 = 0 THEN
        PRINT "Even"
    ELSE
        PRINT "Odd"
    END IF

END

Explanation: MOD gives the remainder after division. If a number divided by 2 leaves remainder 0, it is even; otherwise, it is odd.

11. Flowchart vs Pseudocode

Flowchart	Pseudocode
Graphical representation of an algorithm.	Text-based representation of an algorithm.
Uses standard shapes and arrows.	Uses structured statements.
Shows the flow visually.	Explains the steps in written form.
Can become complex for large problems.	Usually easier to edit for large problems.
Helps visualize the sequence and decisions.	Helps plan program logic before coding.

12. Decomposition

12.1 Definition

Decomposition is the process of breaking a large or complex problem into smaller, manageable subproblems that are easier to understand, solve and test.

In simple words, instead of solving one big problem at once, we divide it into smaller tasks.

12.2 Real-Life Example: Organising a School Annual Function

Suppose a school wants to organise an annual function.

Instead of handling the entire event as one big task, we can divide it into smaller tasks.

Main Problem

Organise School Annual Function

1. Planning

Prepare the schedule.

2. Arrangements

Arrange the venue and equipment.

3. Performances

Prepare activities and performances.

4. Management

Manage participants and guests.

Completed Annual Function

Each smaller task can be divided further if needed.

12.3 Decomposition in Computer Programming

Suppose we need to create a student result program that calculates total marks, percentage and result status.

We can divide the problem into the following subproblems:

1. Input student details and marks.

2. Calculate total marks.

3. Calculate percentage.

4. Check whether the student has passed or failed.

5. Display the result.

Each part can be designed and tested separately.

Example: Student Result Program

MAIN PROBLEM

Create a Student Result Program

Subproblem 1: Input marks

Enter the student's marks.

Subproblem 2: Calculate total

Add the marks of all subjects.

Subproblem 3: Calculate percentage

Calculate the percentage obtained.

Subproblem 4: Determine result

Check the pass/fail condition.

Subproblem 5: Display result

Show the final result.

12.4 Advantages of Decomposition

• Makes complex problems easier to understand.

• Reduces the difficulty of problem-solving.

• Allows programmers to work on separate parts.

• Makes testing and debugging easier.

• Makes programs easier to maintain and improve.

13. Complete Worked Example

Problem: Find the Greater of Two Different Numbers

Write an algorithm to input two different numbers and display the greater number.

Step 1: Analyze the Problem

Component	Details
Input	Two numbers A and B
Process	Compare A and B
Output	The greater number

Assumption: A and B are different numbers.

Step 2: Algorithm

1. Start.

2. Input A and B.

3. If A is greater than B, display A.

4. Otherwise, display B.

5. Stop.

Step 3: Pseudocode

BEGIN
    INPUT A, B

    IF A > B THEN
        PRINT A
    ELSE
        PRINT B
    END IF

END

Step 4: Python Code

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))

if a > b:
    print("Greater number =", a)
else:
    print("Greater number =", b)

Step 5: Testing

A	B	Expected Output
10	20	20
50	30	50
-5	-2	-2

Step 6: Debugging

If the program displays the smaller number, check the comparison condition and correct the logic.

14. Important Exam Questions

Very Short Answer Questions

1. What is problem-solving?

2. Define problem analysis.

3. What is an algorithm?

4. What is coding?

5. Define testing.

6. What is debugging?

7. What is a flowchart?

8. What is pseudocode?

9. What is decomposition?

10. What is a bug?

Short Answer Questions

1. Write the five steps of problem-solving in programming.

2. Explain input, process and output with an example.

3. Write any four characteristics of a good algorithm.

4. Differentiate between testing and debugging.

5. Explain the common symbols used in a flowchart.

6. Write pseudocode to calculate the average of three numbers.

7. Explain the three common types of programming errors.

8. What is decomposition? Give an example.

9. Differentiate between flowchart and pseudocode.

Long Answer Questions

1. Explain the steps involved in problem-solving with suitable examples.

2. Define an algorithm and explain its characteristics.

3. Explain flowcharts and their common symbols with examples.

4. Explain pseudocode and write pseudocode to find the greater of two numbers.

5. Explain decomposition and discuss its advantages in programming.

6. Explain testing and debugging, including syntax, runtime and logical errors.

15. Quick Revision Table

Term	Easy Meaning
Problem-Solving	Solving a problem systematically
Problem Analysis	Understanding the problem, inputs and outputs
Algorithm	A step-by-step solution
Coding	Writing instructions in a programming language
Testing	Checking whether a program works correctly
Debugging	Finding and correcting program errors
Flowchart	Graphical representation of an algorithm
Pseudocode	Text-based representation of an algorithm
Decomposition	Dividing a complex problem into smaller parts

Memory Trick

A → A → C → T → D

• A – Analyze the problem.

• A – Develop an algorithm.

• C – Write the code.

• T – Test the program.

• D – Debug the errors.

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CBSE Class 11 – Computer Science (083)

Unit 2: Computational Thinking and Programming – I

Topic: Familiarization with the Basics of Python Programming

Easy, student-friendly notes in English

1. Introduction to Python

Python is a high-level, general-purpose programming language used to develop software, websites, games, automation scripts, and many other applications.

It was created by Guido van Rossum and first released in 1991.

Python is popular because its syntax is simple and easy to understand. It allows programmers to write programs using fewer lines of code compared to many other programming languages.

Example

print("Hello, World!")

Output:

Hello, World!

The print() function displays information on the screen.

2. Features of Python

Python has several important features.

Feature	Description
Simple and easy to learn	Python has a clear and readable syntax.
High-level language	Programmers do not need to manage low-level computer operations directly.
Interpreted language	Python programs are executed by the Python interpreter.
General-purpose	Python can be used for many types of applications.
Portable	Python programs can run on different operating systems with suitable Python support.
Open-source	Python is freely available to use, modify, and distribute under its licence.
Dynamically typed	The type of a variable is determined at runtime.
Large standard library	Python provides many built-in modules for common tasks.
Object-oriented	Python supports classes and objects.
Case-sensitive	Uppercase and lowercase letters are treated differently.

Example of case sensitivity

name = "Raj"
Name = "Amit"

print(name)
print(Name)

Output:

Raj
Amit

Here, name and Name are two different identifiers.

3. Executing a Simple “Hello, World!” Program

A Python program is a set of instructions written in Python language.

Program

print("Hello, World!")

Output

Hello, World!

Explanation

• print() is a built-in Python function.

• Text written inside quotation marks is called a string literal.

• The function displays the string on the screen.

• The program does not require a semicolon at the end.

Another example

print("Welcome to Python")
print("Computer Science - Class 11")

Output:

Welcome to Python
Computer Science - Class 11

Each print() statement displays its output on a separate line.

4. Execution Modes in Python

Python programs can be executed in two main modes:

1. Interactive Mode

2. Script Mode

4.1 Interactive Mode

In interactive mode, Python executes one statement at a time as the user enters it.

It is useful for testing small instructions and performing quick calculations.

Example

>>> 5 + 3
8
>>> print("Hello")
Hello

The symbol >>> is the Python prompt. It indicates that Python is ready to accept a command.

Advantages

• Immediate output.

• Useful for learning and testing small statements.

• No need to save a program file.

Limitation

A series of statements is not automatically saved as a program file.

4.2 Script Mode

In script mode, Python statements are written in a file and saved with the .py extension.

The file is then executed as a complete program.

Example

Create a file named hello.py.

print("Hello, World!")
print("Welcome to Python")

Output:

Hello, World!
Welcome to Python

Advantages

• Programs can be saved and reused.

• Suitable for writing long programs.

• Programs can be edited and executed again.

Difference between Interactive Mode and Script Mode

Interactive Mode	Script Mode
Executes statements one at a time.	Executes statements from a saved file.
Output is usually displayed immediately.	Output appears when the script is run.
Useful for quick testing.	Useful for complete programs.
Usually does not save the entered commands automatically.	Program is saved in a .py file.

5. Python Character Set

A character set is a collection of valid characters that can be used in a programming language.

Python supports Unicode, which allows it to work with characters from many languages and writing systems.

The Python character set includes:

Character Type	Examples
Alphabets	A-Z, a-z
Digits	0-9
White spaces	Space, tab, newline
Special symbols	+, -, *, /, =, #, @
Unicode characters	Characters from many world languages

Examples

name = "Rajesh"
age = 16
print(name, age)

Output:

Rajesh 16

Python uses characters to form keywords, identifiers, literals, operators, and other program elements.

6. Python Tokens

A token is the smallest meaningful unit of a Python program.

The main types of Python tokens are:

1. Keywords

2. Identifiers

3. Literals

4. Operators

5. Punctuators

Consider this statement:

total = price + 10

Its tokens include:

• total – identifier

• = – operator

• price – identifier

• + – operator

• 10 – literal

6.1 Keywords

Keywords are reserved words in Python that have special meanings. They cannot be used as ordinary variable names.

Examples

if, else, elif, for, while, break, continue, def, return, class, True, False, None, and, or, not, import

Example

if age >= 18:
    print("Eligible")

Here, if is a keyword.

Invalid use of a keyword

if = 10

This causes a syntax error because if is a reserved keyword.

6.2 Identifiers

An identifier is the name given to a variable, function, class, or other program element.

Examples

name = "Aman"
age = 17
total_marks = 450

Here, name, age, and total_marks are identifiers.

Rules for naming identifiers

1. An identifier can contain letters, digits, and underscores.

2. It must not begin with a digit.

3. It cannot contain spaces.

4. It cannot be a Python keyword.

5. Identifiers are case-sensitive.

6. Special symbols such as @, $, and % are not allowed in ordinary identifiers.

Valid and invalid identifiers

Identifier	Valid / Invalid	Reason
name	Valid	Contains letters.
student1	Valid	Does not begin with a digit.
total_marks	Valid	Underscore is allowed.
_value	Valid	Can begin with an underscore.
1student	Invalid	Begins with a digit.
total marks	Invalid	Contains a space.
class	Invalid	It is a keyword.
first-name	Invalid	Hyphen is not allowed in an identifier.

6.3 Literals

A literal is a fixed value written directly in a program.

Types of literals

Type	Examples
Integer	10, -5, 250
Floating-point	3.14, -2.5, 0.0
String	"Hello", 'Python'
Boolean	True, False
Special value	None

Example

age = 16
height = 5.6
name = "Ravi"
is_student = True

Here:

• 16 is an integer literal.

• 5.6 is a floating-point literal.

• "Ravi" is a string literal.

• True is a Boolean literal.

String literals

Strings are sequences of characters enclosed in quotes.

city = "Lucknow"
message = 'Welcome'

Both single and double quotation marks can be used for strings.

6.4 Operators

An operator is a symbol or word used to perform an operation on values or variables.

Common types of operators

Operator Type	Operators	Purpose
Arithmetic	+, -, *, /, //, %, **	Mathematical operations
Relational / Comparison	==, !=, >, <, >=, <=	Compare values
Logical	and, or, not	Combine or reverse conditions
Assignment	=, +=, -=, *=, /=	Assign or update values
Membership	in, not in	Check membership
Identity	is, is not	Check object identity

Example: Arithmetic operators

a = 10
b = 3

print(a + b)
print(a - b)
print(a * b)
print(a / b)

Output:

13
7
30
3.3333333333333335

Example: Comparison operator

print(10 > 5)

Output:

True

6.5 Punctuators

Punctuators are symbols used to organise Python code and define its structure.

Common punctuators

Punctuator	Use
()	Function calls and grouping expressions
[]	Lists and indexing
{}	Dictionaries and sets
:	Starts an indented block
,	Separates items
.	Accesses attributes or methods
;	Can separate simple statements on the same line
#	Begins a comment

Example

marks = [80, 90, 75]
print(marks)

Here:

• [ and ] enclose a list.

• , separates list elements.

• () are used in the function call.

Example of colon

if marks >= 33:
    print("Pass")

The colon : introduces the indented block following the if statement.

7. Variables in Python

A variable is a name that refers to a value stored in memory.

In Python, a variable is created when a value is assigned to it.

Example

age = 16
name = "Aman"
marks = 85.5

Here:

• age refers to the integer 16.

• name refers to the string "Aman".

• marks refers to the floating-point value 85.5.

Displaying variable values

name = "Aman"
age = 16

print(name)
print(age)

Output:

Aman
16

Updating a variable

x = 10
x = 20

print(x)

Output:

20

The second assignment makes x refer to the value 20.

Dynamic typing

Python is dynamically typed. A variable can refer to values of different types at different times.

x = 10
print(x)

x = "Python"
print(x)

Output:

10
Python

8. Concept of L-value and R-value

In an assignment statement, the terms L-value and R-value help explain the roles of the left and right sides.

Example

x = 10

• x is the L-value: the variable name on the left side that receives the assignment.

• 10 is the R-value: the value or expression on the right side that is assigned.

Example with an expression

a = 5
b = 3
c = a + b

In the statement:

c = a + b

• c is the L-value.

• a + b is the R-value expression.

• The expression evaluates to 8, which is assigned to c.

Another example

x = 10
y = x

In y = x:

• y is the L-value.

• x is the R-value expression, whose current value is 10.

Important point

In ordinary Python assignment, the left side must be an assignable target, such as a variable name or an item in a mutable container. A literal or arithmetic expression cannot be used as the assignment target.

Valid:

x = 5

Invalid:

5 = x

The second statement causes a syntax error.

9. Use of Comments in Python

A comment is text written in a program to explain the code. Comments are ignored by Python during normal program execution.

Comments help programmers understand, maintain, and debug programs.

9.1 Single-line comments

A single-line comment begins with the # symbol.

Example

# This program displays a message
print("Hello, World!")

Output:

Hello, World!

The comment is not displayed as output.

9.2 Inline comments

An inline comment appears on the same line as a statement, after the code.

age = 16  # Store the student's age
print(age)

Output:

16

9.3 Multi-line explanations

Python does not have a special multi-line comment symbol. A common approach is to use # at the beginning of each line.

# This program calculates
# the sum of two numbers
a = 10
b = 20
print(a + b)

Output:

30

Triple-quoted strings ('''...''' or """...""") are sometimes used for multi-line explanations, but they are string literals, not true comment syntax. When placed as the first statement in a module, function, or class, they can serve as a docstring.

Example of a docstring

def greet():
    """Display a greeting message."""
    print("Hello!")

10. Complete Example Program

The following program demonstrates variables, literals, operators, comments, and output.

# Program to calculate total marks

name = "Ravi"
english = 80
computer = 95

total = english + computer

print("Student Name:", name)
print("Total Marks:", total)

Output:

Student Name: Ravi
Total Marks: 175

Concepts used

Concept	Example
Comment	# Program to calculate total marks
Variable	name, english, computer, total
String literal	"Ravi"
Integer literal	80, 95
Operator	+
Function	print()

11. Quick Revision

• Python is a high-level, general-purpose programming language.

• Python is case-sensitive.

• Python programs can be executed in interactive mode or script mode.

• A token is the smallest meaningful unit of a program.

• Keywords are reserved words.

• Identifiers are names used for variables and other program elements.

• Literals are fixed values written directly in a program.

• Operators perform operations on values.

• Punctuators help organise code.

• Variables are names that refer to values.

• In an assignment, the L-value is the assignment target and the R-value is the value or expression being assigned.

• Comments begin with # and are ignored during normal execution.

12. Important Exam Questions

1. What is Python? Write any five features of Python.

2. Write a Python program to display Hello, World!.

3. Differentiate between interactive mode and script mode.

4. What is a character set?

5. Define Python tokens and list their types.

6. What are keywords? Give five examples.

7. Define identifiers and write the rules for naming them.

8. What is a literal? Give examples of different types of literals.

9. What are operators? Name any four types of operators.

10. What are punctuators? Give four examples.

11. What is a variable? Explain dynamic typing with an example.

12. Explain L-value and R-value with an assignment statement.

13. What is a comment? Explain single-line and inline comments.

14. Identify the tokens in the following statement:

    total = marks + 10 

____________________________________________________________________

 

1. Introduction to Data Types

A data type specifies the kind of value that a variable can refer to and the operations that can be performed on that value.

Python provides several built-in data types, such as:

• Number: int, float, complex

• Boolean: bool

• Sequence: str, list, tuple

• None type: NoneType

• Mapping: dict

Example

age = 16
price = 99.5
name = "Ravi"

Here:

• age refers to an integer.

• price refers to a floating-point number.

• name refers to a string.

The type() function is used to identify the data type of a value or variable.

print(type(age))
print(type(price))
print(type(name))

Output:

<class 'int'>
<class 'float'>
<class 'str'>

2. Number Data Types

Python has three main numeric data types:

1. Integer (int)

2. Floating-point (float)

3. Complex (complex)

2.1 Integer (int)

An integer is a whole number without a decimal point. It can be positive, negative, or zero.

Examples

a = 10
b = -25
c = 0

print(a)
print(b)
print(c)

Output:

10
-25
0

Important points

• Integers do not contain a decimal point.

• Python integers can represent very large whole numbers, limited by available memory.

• Arithmetic operations such as addition, subtraction, and multiplication can be performed on integers.

Example

a = 15
b = 5

print(a + b)
print(a * b)

Output:

20
75

2.2 Floating-point (float)

A floating-point number represents a number that contains a fractional part or is written using scientific notation.

Examples

x = 3.14
y = -2.5
z = 10.0

print(x)
print(y)
print(z)

Output:

3.14
-2.5
10.0

Scientific notation

Python supports scientific notation using e or E.

a = 2.5e3
b = 4.2e-2

print(a)
print(b)

Output:

2500.0
0.042

Important points

• A floating-point number usually contains a decimal point or exponent.

• 10 is an integer, while 10.0 is a floating-point number.

• Floating-point values are stored approximately, so some decimal calculations may have small precision differences.

Example

print(0.1 + 0.2)

Output:

0.30000000000000004

This happens because many decimal fractions cannot be represented exactly in binary floating-point format.

2.3 Complex (complex)

A complex number contains a real part and an imaginary part.

A complex number is written in Python using the form:

a + bj

Here:

• a is the real part.

• b is the imaginary part.

• j represents the imaginary unit.

Examples

x = 3 + 4j
y = 2 - 5j

print(x)
print(y)

Output:

(3+4j)
(2-5j)

Accessing real and imaginary parts

z = 3 + 4j

print(z.real)
print(z.imag)

Output:

3.0
4.0

Important points

• Python uses j or J for the imaginary part.

• The real and imaginary parts are accessed using .real and .imag.

• Complex numbers are useful in scientific and mathematical calculations.

3. Boolean Data Type (bool)

The Boolean data type represents one of two values:

• True

• False

Boolean values are commonly used in conditions and decision-making statements.

Example

is_student = True
is_absent = False

print(is_student)
print(is_absent)

Output:

True
False

Boolean expressions

Comparison operations produce Boolean results.

print(10 > 5)
print(10 == 5)
print(7 != 3)

Output:

True
False
True

Important points

• True and False are Python keywords.

• Their first letters must be capitalised.

• True and False are different from the strings "True" and "False".

print(type(True))
print(type("True"))

Output:

<class 'bool'>
<class 'str'>

4. Sequence Data Types

A sequence is an ordered collection of items. Each item has a position, called an index.

Python's commonly used sequence types include:

1. String (str)

2. List (list)

3. Tuple (tuple)

Sequence indexing starts from 0.

4.1 String (str)

A string is an ordered sequence of characters enclosed in single, double, or triple quotation marks.

Examples

name = "Rajesh"
city = 'Lucknow'
message = """Welcome to Python"""

Accessing characters

word = "PYTHON"

print(word[0])
print(word[1])
print(word[-1])

Output:

P
Y
N

Positive indexing starts from the left at 0. Negative indexing starts from the right at -1.

String slicing

Slicing is used to access a part of a sequence.

word = "PYTHON"

print(word[0:3])
print(word[2:5])

Output:

PYT
THO

The ending index is excluded from the result.

Important points

• Strings are ordered.

• Strings can contain letters, digits, spaces, and special characters.

• Strings are immutable, which means their characters cannot be changed directly after the string is created.

Example of immutability

word = "PYTHON"
word[0] = "J"

This causes a TypeError because individual characters of a string cannot be reassigned.

4.2 List (list)

A list is an ordered collection of items enclosed in square brackets [].

A list can contain values of the same or different data types.

Examples

marks = [80, 90, 75, 85]
names = ["Aman", "Ravi", "Neha"]
mixed = [10, "Python", 3.5, True]

Accessing list elements

marks = [80, 90, 75, 85]

print(marks[0])
print(marks[2])
print(marks[-1])

Output:

80
75
85

Updating a list

Lists are mutable, which means their elements can be changed after creation.

marks = [80, 90, 75]
marks[1] = 95

print(marks)

Output:

[80, 95, 75]

Adding an element

numbers = [10, 20, 30]
numbers.append(40)

print(numbers)

Output:

[10, 20, 30, 40]

Important points

• Lists preserve order.

• Lists allow duplicate values.

• Lists can contain different data types.

• Lists are mutable.

4.3 Tuple (tuple)

A tuple is an ordered collection of items enclosed in parentheses ().

Example

days = ("Monday", "Tuesday", "Wednesday")
numbers = (10, 20, 30)

Accessing tuple elements

days = ("Monday", "Tuesday", "Wednesday")

print(days[0])
print(days[2])

Output:

Monday
Wednesday

Single-element tuple

A single-element tuple must include a comma.

x = (10,)
print(type(x))

Output:

<class 'tuple'>

Without the comma, (10) is simply an integer expression inside parentheses.

Important points

• Tuples preserve order.

• Tuples allow duplicate values.

• Tuples can contain different data types.

• Tuples are immutable.

Example of immutability

numbers = (10, 20, 30)
numbers[0] = 100

This causes a TypeError because tuple elements cannot be reassigned.

5. None Data Type (NoneType)

None is a special value in Python that represents the absence of a value.

Its data type is NoneType.

Example

result = None

print(result)
print(type(result))

Output:

None
<class 'NoneType'>

Common uses of None

• To indicate that a variable has no value assigned yet.

• To represent the absence of a result.

• As the default return value of a function that does not explicitly return another value.

Example

def greet():
    print("Hello")

result = greet()
print(result)

Output:

Hello
None

The function displays Hello but does not explicitly return a value, so its return value is None.

Important point

None is not the same as 0, False, or an empty string "".

6. Mapping Data Type – Dictionary (dict)

A dictionary is a collection of key-value pairs.

It is written using curly braces {}. Each key is associated with a value.

Syntax

dictionary_name = {
    key1: value1,
    key2: value2
}

Example

student = {
    "name": "Ravi",
    "age": 16,
    "marks": 88
}

print(student)

Output:

{'name': 'Ravi', 'age': 16, 'marks': 88}

Accessing dictionary values

Values are accessed using their keys.

student = {
    "name": "Ravi",
    "age": 16,
    "marks": 88
}

print(student["name"])
print(student["marks"])

Output:

Ravi
88

Updating a dictionary

Dictionaries are mutable, so their values can be changed.

student = {"name": "Ravi", "marks": 88}

student["marks"] = 95

print(student)

Output:

{'name': 'Ravi', 'marks': 95}

Adding a new key-value pair

student = {"name": "Ravi"}

student["age"] = 16

print(student)

Output:

{'name': 'Ravi', 'age': 16}

Important points

• A dictionary stores data as key-value pairs.

• Keys must be unique.

• Keys must be hashable, such as strings, numbers, or tuples containing only hashable items.

• Values can be of different data types.

• Dictionaries are mutable.

• Dictionaries preserve insertion order in modern Python.

7. Mutable and Immutable Data Types

Python data types can be classified as mutable or immutable.

7.1 Mutable Data Types

A mutable object can be changed after it has been created.

Examples:

• list

• dict

• set

Example

numbers = [10, 20, 30]
numbers[0] = 100

print(numbers)

Output:

[100, 20, 30]

The original list is modified.

7.2 Immutable Data Types

An immutable object cannot be changed after it has been created.

Examples:

• int

• float

• complex

• bool

• str

• tuple

• NoneType

Example

x = 10
x = x + 5

print(x)

Output:

15

This does not change the integer object 10. Instead, the expression creates or refers to the value 15, and the variable x is reassigned to it.

String example

name = "Ravi"
name = name + " Kumar"

print(name)

Output:

Ravi Kumar

A new string is created and assigned to name; the original string is not modified.

8. Difference Between Mutable and Immutable Data Types

Mutable	Immutable
Can be changed after creation.	Cannot be changed after creation.
Existing object can be modified.	Changes require creating or referring to another object.
Examples: list, dict, set.	Examples: int, float, bool, str, tuple.
Example: items[0] = 50 for a list.	Example: assigning to word[0] in a string causes an error.

9. Summary Table of Python Data Types

Data Type	Python Type	Example	Mutable / Immutable
Integer	int	25	Immutable
Floating-point	float	3.14	Immutable
Complex	complex	2 + 3j	Immutable
Boolean	bool	True	Immutable
String	str	"Python"	Immutable
List	list	[10, 20, 30]	Mutable
Tuple	tuple	(10, 20, 30)	Immutable
None	NoneType	None	Immutable
Dictionary	dict	{"name": "Ravi"}	Mutable

10. Complete Example Program

# Demonstration of Python data types

age = 16
height = 5.7
number = 2 + 3j
is_student = True
name = "Ravi"
marks = [80, 90, 85]
subjects = ("English", "Maths", "Computer")
student = {"name": "Ravi", "age": 16}
result = None

print(type(age))
print(type(height))
print(type(number))
print(type(is_student))
print(type(name))
print(type(marks))
print(type(subjects))
print(type(student))
print(type(result))

Output:

<class 'int'>
<class 'float'>
<class 'complex'>
<class 'bool'>
<class 'str'>
<class 'list'>
<class 'tuple'>
<class 'dict'>
<class 'NoneType'>

11. Quick Revision

• A data type defines the kind of value represented by an object.

• int, float, and complex are numeric data types.

• bool stores True or False.

• str, list, and tuple are commonly used sequence types.

• None represents the absence of a value.

• dict stores key-value pairs.

• Lists and dictionaries are mutable.

• Integers, floats, complex numbers, Booleans, strings, tuples, and None are immutable.

• The type() function identifies the type of an object.

• Sequence indexing starts from 0.

12. Important Exam Questions

1. What is a data type? Name the main built-in data types in Python.

2. Explain integer, floating-point, and complex data types with examples.

3. What is a Boolean data type? Give an example.

4. Define a sequence. Explain string, list, and tuple.

5. Differentiate between a list and a tuple.

6. What is None in Python? Give an example.

   ____________________________________________________________________

   1. Operators in Python

   An operator is a symbol or keyword used to perform an operation on values or variables.

   The values on which an operator works are called operands.

   Example:

   a = 10
   b = 5
   print(a + b)

   Here, + is the operator, while a and b are operands.

   1.1 Arithmetic Operators

   Arithmetic operators are used to perform mathematical calculations.

   Operator	Name	Example	Result
   +	Addition	10 + 3	13
   -	Subtraction	10 - 3	7
   *	Multiplication	10 * 3	30
   /	Division	10 / 3	3.333...
   //	Floor division	10 // 3	3
   %	Modulus	10 % 3	1
   **	Exponentiation	2 ** 3	8

   Important points

   • / performs division and returns a floating-point result.

   • // performs floor division, rounding the quotient down to the nearest integer value.

   • % returns the remainder.

   • ** calculates a power.

   Example

   a = 17
   b = 5
   
   print(a / b)
   print(a // b)
   print(a % b)
   print(a ** 2)

   Output:

   3.4
   3
   2
   289

   1.2 Relational (Comparison) Operators

   Relational operators compare two values. The result is always a Boolean value: True or False.

   Operator	Meaning	Example	Result
   ==	Equal to	5 == 5	True
   !=	Not equal to	5 != 3	True
   >	Greater than	8 > 4	True
   <	Less than	2 < 7	True
   >=	Greater than or equal to	5 >= 5	True
   <=	Less than or equal to	3 <= 2	False

   Example

   a = 10
   b = 20
   
   print(a < b)
   print(a == b)
   print(a != b)

   Output:

   True
   False
   True

   Remember: = is an assignment operator, whereas == is a comparison operator.

   1.3 Logical Operators

   Logical operators are used to combine or reverse conditions.

   Operator	Meaning
   and	True only when both conditions are True
   or	True when at least one condition is True
   not	Reverses the Boolean result

   Truth table

   A	B	A and B	A or B
   True	True	True	True
   True	False	False	True
   False	True	False	True
   False	False	False	False

   A	not A
   True	False
   False	True

   Example

   age = 20
   
   print(age >= 18 and age <= 60)
   print(age < 18 or age > 60)
   print(not age >= 18)

   Output:

   True
   False
   False

   1.4 Assignment Operators

   The assignment operator = assigns a value to a variable.

   x = 10

   Here, the value 10 is assigned to x.

   Other assignment operators can also be used to assign values.

   Operator	Example	Equivalent statement
   =	x = 10	Assign 10 to x
   +=	x += 5	x = x + 5
   -=	x -= 5	x = x - 5
   *=	x *= 5	x = x * 5
   /=	x /= 5	x = x / 5
   //=	x //= 5	x = x // 5
   %=	x %= 5	x = x % 5
   **=	x **= 2	x = x ** 2

   Example

   x = 10
   x += 5
   print(x)

   Output:

   15

   1.5 Augmented Assignment Operators

   An augmented assignment operator performs an operation and assigns the result back to the same variable.

   For example:

   x = 10
   x += 3

   This is equivalent to:

   x = 10
   x = x + 3

   Output:

   13

   Other examples include -=, *=, /=, //=, %=, and **=.

   1.6 Identity Operators (is, is not)

   Identity operators check whether two references point to the same object in memory.

   Operator	Meaning
   is	True if both references point to the same object
   is not	True if they point to different objects

   Example

   a = None
   
   print(a is None)
   print(a is not None)

   Output:

   True
   False

   Important difference: == and is

   • == checks whether two values are equal.

   • is checks whether two references identify the same object.

   a = [1, 2, 3]
   b = [1, 2, 3]
   
   print(a == b)
   print(a is b)

   Output:

   True
   False

   The lists contain equal values, but they are separate list objects.

   1.7 Membership Operators (in, not in)

   Membership operators check whether a value is present in a sequence or collection.

   Operator	Meaning
   in	True if the value is present
   not in	True if the value is absent

   Example

   name = "Python"
   
   print("P" in name)
   print("z" in name)
   print("z" not in name)

   Output:

   True
   False
   True

   Example with a list

   numbers = [10, 20, 30]
   
   print(20 in numbers)
   print(50 not in numbers)

   Output:

   True
   True

   2. Expressions, Statements, Type Conversion and Input/Output

   2.1 Expression

   An expression is a combination of values, variables, operators, and function calls that produces a result when evaluated.

   Examples

   5 + 3
   a * b
   (10 + 5) / 3

   Example program

   a = 10
   b = 5
   
   result = a + b * 2
   print(result)

   Output:

   20

   The expression a + b * 2 evaluates to 20 because multiplication is performed before addition.

   2.2 Statement

   A statement is an instruction that Python executes.

   Examples:

   x = 10
   print(x)

   • x = 10 is an assignment statement.

   • print(x) is a function-call statement.

   Difference between expression and statement

   Expression	Statement
   Produces a value when evaluated.	Performs an instruction or action.
   Example: 5 + 3	Example: x = 5 + 3
   Can be part of a statement.	May contain one or more expressions.

   2.3 Precedence of Operators

   Operator precedence determines the order in which operators are evaluated in an expression.

   Common precedence order

   From higher precedence to lower precedence:

   Priority	Operators
   1	Parentheses: ()
   2	Exponentiation: **
   3	Unary operators: +x, -x, ~x
   4	Multiplication, division, floor division, modulus: *, /, //, %
   5	Addition and subtraction: +, -
   6	Comparisons: <, <=, >, >=, ==, !=, in, is
   7	Logical not
   8	Logical and
   9	Logical or

   Note: Operators at the same precedence level generally follow associativity rules. Exponentiation is evaluated from right to left.

   Example 1

   print(5 + 3 * 2)

   Output:

   11

   Multiplication is performed first: 3 * 2 = 6, then 5 + 6 = 11.

   Example 2

   print((5 + 3) * 2)

   Output:

   16

   Parentheses are evaluated first.

   Example 3

   print(2 ** 3 ** 2)

   Output:

   512

   Exponentiation is evaluated from right to left:

   2 ** (3 ** 2)

   2.4 Evaluation of an Expression

   Evaluation means calculating the value of an expression by applying the operators according to their precedence and associativity.

   Example

   a = 8
   b = 4
   c = 2
   
   result = a + b * c
   print(result)

   Evaluation:

   1. b * c → 4 * 2 → 8

   2. a + 8 → 8 + 8 → 16

   Output:

   16

   3. Type Conversion

   Type conversion means converting a value from one data type to another.

   There are two main types:

   1. Implicit type conversion

   2. Explicit type conversion

   3.1 Implicit Type Conversion

   Implicit conversion is performed automatically by Python.

   Example

   a = 10
   b = 2.5
   
   result = a + b
   print(result)
   print(type(result))

   Output:

   12.5
   <class 'float'>

   Python converts the integer 10 to a floating-point value during the calculation.

   3.2 Explicit Type Conversion

   Explicit conversion is performed by the programmer using conversion functions.

   Function	Converts to	Example
   int()	Integer	int("25") → 25
   float()	Float	float("3.5") → 3.5
   str()	String	str(100) → "100"
   bool()	Boolean	bool(1) → True
   list()	List	list("ABC") → ['A', 'B', 'C']
   tuple()	Tuple	tuple([1, 2]) → (1, 2)

   Example

   x = "25"
   y = int(x)
   
   print(y + 5)

   Output:

   30

   Without int(x), "25" is a string, and adding the integer 5 to it would cause a TypeError.

   Important points

   • int(3.9) produces 3, not 4.

   • float(5) produces 5.0.

   • str(25) produces "25".

   • int("hello") causes a ValueError because "hello" cannot be converted to an integer.

   4. Input and Output in Python

   4.1 Accepting Input Using input()

   The input() function accepts data from the keyboard through the console.

   Syntax

   variable = input("Message")

   Important: input() returns the entered data as a string.

   Example

   name = input("Enter your name: ")
   print("Welcome", name)

   If the user enters Aman, the output is:

   Enter your name: Aman
   Welcome Aman

   4.2 Accepting Numeric Input

   Convert the input string to the required numeric type.

   Integer input

   age = int(input("Enter your age: "))
   print(age)

   Floating-point input

   price = float(input("Enter price: "))
   print(price)

   Example: Adding two numbers

   a = int(input("Enter first number: "))
   b = int(input("Enter second number: "))
   
   total = a + b
   print("Sum =", total)

   If the user enters 10 and 20:

   Enter first number: 10
   Enter second number: 20
   Sum = 30

   4.3 Displaying Output Using print()

   The print() function displays data on the screen.

   Example

   print("Hello, Python!")
   print(10 + 5)

   Output:

   Hello, Python!
   15

   Using commas in print()

   name = "Ravi"
   age = 16
   
   print("Name:", name, "Age:", age)

   Output:

   Name: Ravi Age: 16

   Using f-strings

   An f-string allows variables and expressions to be included inside a string.

   name = "Ravi"
   marks = 90
   
   print(f"{name} scored {marks} marks.")

   Output:

   Ravi scored 90 marks.

   5. Errors in Python

   An error is a problem in a program that prevents it from working as intended.

   The three common categories are:

   1. Syntax errors

   2. Runtime errors

   3. Logical errors

   5.1 Syntax Errors

   A syntax error occurs when Python code does not follow the rules of Python grammar.

   Example

   if age >= 18
       print("Eligible")

   Problem: The colon : is missing after the condition.

   Correct code:

   if age >= 18:
       print("Eligible")

   Other common causes include missing brackets, missing quotation marks, and incorrect indentation in places where indentation is required.

   5.2 Runtime Errors

   A runtime error occurs while a program is running.

   Example: Division by zero

   a = 10
   b = 0
   
   print(a / b)

   This causes a ZeroDivisionError.

   Example: Invalid type operation

   age = "16"
   print(age + 5)

   This causes a TypeError because Python cannot add a string and an integer.

   5.3 Logical Errors

   A logical error occurs when a program runs without crashing but produces an incorrect result because its logic is wrong.

   Example

   length = 10
   width = 5
   
   area = length + width
   print(area)

   Output:

   15

   The program runs, but the area of a rectangle should be calculated using multiplication.

   Correct code:

   area = length * width
   print(area)

   Correct output:

   50

   Difference between error types

   Error Type	When it occurs	Example
   Syntax error	Code is grammatically incorrect.	Missing :
   Runtime error	While the program is executing.	Division by zero
   Logical error	Program runs but gives a wrong answer.	Using + instead of * for area

   6. Flow of Control

   Flow of control refers to the order in which statements of a program are executed.

   Python programs commonly use three types of flow:

   1. Sequential flow

   2. Conditional flow

   3. Iterative flow

   6.1 Sequential Flow

   In sequential flow, statements are executed one after another in the order in which they appear.

   Example

   a = 10
   b = 20
   total = a + b
   
   print(total)

   Output:

   30

   The statements execute in this order:

   Start

   Assign a = 10

   Assign b = 20

   Calculate total = a + b

   Display total

   End

   6.2 Conditional Flow

   Conditional flow allows a program to make decisions and execute different statements depending on whether a condition is true or false.

   Python uses conditional statements such as:

   • if

   • if-else

   • if-elif-else

   6.3 Iterative Flow

   Iterative flow means repeating a set of statements multiple times.

   Python provides two main loops:

   • for loop

   • while loop

   Example: for loop

   for i in range(1, 4):
       print(i)

   Output:

   1
   2
   3

   The loop executes three times.

   Example: while loop

   i = 1
   
   while i <= 3:
       print(i)
       i += 1

   Output:

   1
   2
   3

   The loop continues while the condition i <= 3 is true.

   7. Use of Indentation in Python

   Indentation means leaving spaces at the beginning of a line of code.

   Python uses indentation to define blocks of code. Unlike some other programming languages, Python does not use braces {} to define the body of an if statement or loop.

   Correct indentation

   age = 20
   
   if age >= 18:
       print("You are an adult")

   Output:

   You are an adult

   The print() statement is indented, so it belongs to the if block.

   Incorrect indentation

   age = 20
   
   if age >= 18:
   print("You are an adult")

   This causes an IndentationError.

   Important points

   • Use consistent indentation.

   • Four spaces are the standard indentation level in Python.

   • Statements belonging to the same block should have the same indentation.

   • Indentation is important in conditional statements, loops, functions, and classes.

   8. Conditional Statements

   Conditional statements are used to make decisions in a program.

   8.1 The if Statement

   The if statement executes a block of code only when its condition is true.

   Syntax

   if condition:
       statement

   Example

   age = 20
   
   if age >= 18:
       print("Eligible to vote")

   Output:

   Eligible to vote

   If the condition is false, the indented statement is skipped.

   Flowchart of if

   Start

   Check condition

   True

   Execute block

   False

   Skip block

   End

   8.2 The if-else Statement

   The if-else statement selects one of two blocks.

   • If the condition is true, the if block executes.

   • If the condition is false, the else block executes.

   Syntax

   if condition:
       statement1
   else:
       statement2

   Example: Even or odd number

   num = int(input("Enter a number: "))
   
   if num % 2 == 0:
       print("Even number")
   else:
       print("Odd number")

   If the user enters 8:

   Enter a number: 8
   Even number

   If the user enters 7:

   Enter a number: 7
   Odd number

   Flowchart of if-else

   Start

   Check condition

   True

   Execute if block

   False

   Execute else block

   End

   8.3 The if-elif-else Statement

   The if-elif-else statement is used when there are multiple conditions to check.

   Python checks conditions from top to bottom. The first true condition's block is executed, and the remaining conditions are skipped.

   Syntax

   if condition1:
       statement1
   elif condition2:
       statement2
   elif condition3:
       statement3
   else:
       statement4

   Example: Checking marks

   marks = int(input("Enter marks: "))
   
   if marks >= 90:
       print("Grade A")
   elif marks >= 75:
       print("Grade B")
   elif marks >= 50:
       print("Grade C")
   else:
       print("Needs improvement")

   If the user enters 82:

   Enter marks: 82
   Grade B

   Flowchart of if-elif-else

   Start

   Check condition 1

   True

   Block 1

   False

   Check condition 2

   True → Block 2

   False → else block

   End

   9. Simple Python Programs Using Conditional Statements

   Program 1: Find the Absolute Value of a Number

   The absolute value of a number is its distance from zero. It is never negative.

   For example:

   • Absolute value of 5 is 5.

   • Absolute value of -5 is 5.

   • Absolute value of 0 is 0.

   Loading

   Program

   num = int(input("Enter a number: "))
   
   if num < 0:
       absolute = -num
   else:
       absolute = num
   
   print("Absolute value =", absolute)

   Sample output

   Enter a number: -8
   Absolute value = 8

   Program 2: Sort Three Numbers in Ascending Order

   This program arranges three numbers from smallest to largest.

   Program

   a = int(input("Enter first number: "))
   b = int(input("Enter second number: "))
   c = int(input("Enter third number: "))
   
   if a <= b and a <= c:
       if b <= c:
           print(a, b, c)
       else:
           print(a, c, b)
   
   elif b <= a and b <= c:
       if a <= c:
           print(b, a, c)
       else:
           print(b, c, a)
   
   else:
       if a <= b:
           print(c, a, b)
       else:
           print(c, b, a)

   Sample output

   Enter first number: 30
   Enter second number: 10
   Enter third number: 20
   10 20 30

   Explanation: The program compares the three numbers and uses nested if statements to display them in ascending order. The <= operator also allows equal numbers.

   Program 3: Check Divisibility of a Number

   A number is divisible by another number if the remainder is zero.

   For example:

   • 12 is divisible by 3 because 12 % 3 is 0.

   • 13 is not divisible by 3 because 13 % 3 is 1.

   Program: Check divisibility by 5

   num = int(input("Enter a number: "))
   
   if num % 5 == 0:
       print("Divisible by 5")
   else:
       print("Not divisible by 5")

   Sample output

   Enter a number: 25
   Divisible by 5

   Program: Check divisibility by another number

   num = int(input("Enter the number: "))
   divisor = int(input("Enter the divisor: "))
   
   if divisor == 0:
       print("Division by zero is not allowed")
   elif num % divisor == 0:
       print("The number is divisible")
   else:
       print("The number is not divisible")

   10. Quick Revision

   • Operators perform operations on values and variables.

   • Arithmetic operators perform mathematical calculations.

   • Relational operators compare values and return Boolean results.

   • Logical operators combine or reverse conditions.

   • Assignment operators assign values to variables.

   • Augmented assignment operators update a variable using an operation.

   • is and is not check object identity.

   • in and not in check membership.

   • An expression produces a value; a statement is an instruction.

   • Operator precedence determines the order of evaluation.

   • input() accepts console input as a string.

   • print() displays output.

   • Type conversion changes a value from one type to another.

   • Syntax errors involve invalid Python syntax.

   • Runtime errors occur during program execution.

   • Logical errors produce incorrect results despite successful execution.

   • Sequential flow executes statements in order.

   • Conditional flow selects blocks based on conditions.

   • Iterative flow repeats statements.

   • Indentation defines code blocks in Python.

   • if, if-else, and if-elif-else are conditional statements.

   11. Important Exam Questions

   1. Define an operator. Explain arithmetic operators with examples.

   2. Differentiate between = and ==.

   3. Explain logical operators with a truth table.

   4. What are augmented assignment operators? Give examples.

   5. Differentiate between == and is.

   6. Explain membership operators with examples.

   7. Define expression and statement with examples.

   8. What is operator precedence? Evaluate 5 + 3 * 2.

   9. Differentiate between implicit and explicit type conversion.

   10. Explain the use of input() and print().

   11. Differentiate between syntax, runtime, and logical errors.

   12. What is flow of control? Explain sequential, conditional, and iterative flow.

   13. Why is indentation important in Python?

   14. Explain if, if-else, and if-elif-else with examples.

   15. Write a Python program to find the absolute value of a number.

   16. Write a Python program to arrange three numbers in ascending order.

   17. Write a Python program to check whether a number is divisible by 5.

   18. Write a Python program to check whether a number is even or odd.

       _________________RUonTop________________

       PART A: ITERATIVE STATEMENTS

       1. Introduction to Iteration

       Iteration means repeating a set of statements again and again until a particular condition is satisfied.

       Python provides two main iterative statements:

       1. for loop
       2. while loop

       Example

       Suppose we want to print numbers from 1 to 5.

       Instead of writing:

       print(1)
       print(2)
       print(3)
       print(4)
       print(5)
       

       we can use a loop:

       for i in range(1, 6):
           print(i)
       

       Output:

       1
       2
       3
       4
       5
       

       Loops make programs shorter, easier to understand, and easier to maintain.

       ---

       2. for Loop

       The for loop is used to repeat a block of statements for each item in a sequence or iterable.

       Syntax

       for variable in sequence:
           statement1
           statement2
       

       Example

       for i in range(1, 6):
           print(i)
       

       Output:

       1
       2
       3
       4
       5
       

       Working

       The loop works as follows:

       • i gets the value 1 → print 1
       • i gets the value 2 → print 2
       • i gets the value 3 → print 3
       • i gets the value 4 → print 4
       • i gets the value 5 → print 5
       • Loop ends.

       ---

       3. range() Function

       The range() function generates a sequence of numbers and is commonly used with for loops.

       There are three common forms.

       3.1 range(stop)

       range(stop)
       

       It generates numbers from 0 up to, but not including, stop.

       Example

       for i in range(5):
           print(i)
       

       Output:

       0
       1
       2
       3
       4
       

       ---

       3.2 range(start, stop)

       range(start, stop)
       

       It starts from start and stops before stop.

       Example

       for i in range(2, 7):
           print(i)
       

       Output:

       2
       3
       4
       5
       6
       

       ---

       3.3 range(start, stop, step)

       The third argument specifies the difference between consecutive values.

       Example

       for i in range(2, 11, 2):
           print(i)
       

       Output:

       2
       4
       6
       8
       10
       

       Example: Reverse counting

       A negative step can be used to count backwards.

       for i in range(5, 0, -1):
           print(i)
       

       Output:

       5
       4
       3
       2
       1
       

       Important rule

       The stop value is not included.

       For example:

       range(1, 5)
       

       produces:

       1 2 3 4
       

       ---

       4. Flowchart of a for Loop

       The basic flow of a loop can be represented as:

                    START
                      |
               Initialize / Get
                 next value
                      |
               Is another value
                  available?
                 /          \
              YES            NO
               |              |
          Execute loop       END
             body
               |
               └───────────────
       

       ---

       5. while Loop

       A while loop repeatedly executes a block of statements as long as its condition is true.

       Syntax

       while condition:
           statement
       

       Example

       i = 1
       
       while i <= 5:
           print(i)
           i += 1
       

       Output:

       1
       2
       3
       4
       5
       

       Working

       Initially:

       i = 1
       

       Python checks:

       i <= 5
       

       If it is True, the loop body executes.

       Then:

       i += 1
       

       increases i.

       This continues until the condition becomes False.

       ---

       6. Flowchart of a while Loop

                    START
                      |
               Initialize variable
                      |
               Check condition
                 /          \
              TRUE          FALSE
               |              |
           Execute body       END
               |
            Update variable
               |
               └──────────────
                 back to
              condition
       

       Important point

       A while loop must normally change something that affects its condition. Otherwise, the loop may become an infinite loop.

       Example of an infinite loop

       i = 1
       
       while i <= 5:
           print(i)
       

       Here i never changes, so the condition remains true.

       ---

       7. Difference Between for and while Loop

       for Loop	while Loop
       Commonly used when iterating over a sequence or a known range of values.	Commonly used when repetition depends on a condition.
       Usually uses range() or another iterable.	Uses a Boolean condition.
       Loop variable is commonly updated automatically by iteration.	Programmer usually updates the control variable.
       Suitable for definite iteration.	Suitable for condition-controlled iteration.

       ---

       8. break Statement

       The break statement immediately terminates the nearest enclosing loop.

       Example

       for i in range(1, 10):
           if i == 5:
               break
           print(i)
       

       Output:

       1
       2
       3
       4
       

       When i becomes 5, break terminates the loop.

       Flow

       1 → 2 → 3 → 4 → 5
                         |
                       break
                         |
                        END
       

       ---

       9. continue Statement

       The continue statement skips the remaining statements in the current iteration and moves to the next iteration of the loop.

       Example

       for i in range(1, 6):
           if i == 3:
               continue
           print(i)
       

       Output:

       1
       2
       4
       5
       

       When i is 3, print(i) is skipped.

       Difference Between break and continue

       break	continue
       Terminates the loop completely.	Skips only the current iteration.
       Control moves outside the loop.	Control moves to the next iteration.

       ---

       10. Nested Loops

       A nested loop is a loop placed inside another loop.

       The inner loop executes completely for each iteration of the outer loop.

       Example

       for i in range(1, 4):
           for j in range(1, 4):
               print(i, j)
       

       Output:

       1 1
       1 2
       1 3
       2 1
       2 2
       2 3
       3 1
       3 2
       3 3
       

       Here:

       • i is controlled by the outer loop.
       • j is controlled by the inner loop.
       • The inner loop runs three times for every one iteration of the outer loop.

       ---

       11. Generating Patterns

       Nested loops are commonly used to generate patterns.

       Program 1: Square Pattern

       for i in range(1, 5):
           for j in range(1, 5):
               print("*", end=" ")
           print()
       

       Output:

       * * * *
       * * * *
       * * * *
       * * * *
       

       Explanation

       • Outer loop controls the rows.
       • Inner loop controls the columns.
       • end=" " keeps the stars on the same line.
       • print() moves to the next line.

       ---

       Program 2: Increasing Star Pattern

       for i in range(1, 6):
           for j in range(i):
               print("*", end=" ")
           print()
       

       Output:

       *
       * *
       * * *
       * * * *
       * * * * *
       

       ---

       Program 3: Number Pattern

       for i in range(1, 6):
           for j in range(1, i + 1):
               print(j, end=" ")
           print()
       

       Output:

       1
       1 2
       1 2 3
       1 2 3 4
       1 2 3 4 5
       

       ---

       12. Summation of a Series

       A loop can be used to calculate the sum of a series.

       Program: Sum of Numbers from 1 to N

       n = int(input("Enter a number: "))
       
       total = 0
       
       for i in range(1, n + 1):
           total += i
       
       print("Sum =", total)
       

       If the user enters 5:

       Enter a number: 5
       Sum = 15
       

       Calculation

       1 + 2 + 3 + 4 + 5 = 15
       

       ---

       Program: Sum of Even Numbers

       n = int(input("Enter a number: "))
       
       total = 0
       
       for i in range(2, n + 1, 2):
           total += i
       
       print("Sum of even numbers =", total)
       

       For n = 10:

       Sum of even numbers = 30
       

       because:

       2 + 4 + 6 + 8 + 10 = 30
       

       ---

       13. Factorial of a Positive Number

       The factorial of a positive integer n is the product of all positive integers from 1 to n.

       It is represented by n!.

       Examples

       5! = 5 × 4 × 3 × 2 × 1 = 120
       

       3! = 3 × 2 × 1 = 6
       

       By definition:

       0! = 1
       

       Program Using for Loop

       n = int(input("Enter a positive number: "))
       
       factorial = 1
       
       if n < 0:
           print("Please enter a positive number.")
       else:
           for i in range(1, n + 1):
               factorial *= i
       
           print("Factorial =", factorial)
       

       Sample output

       Enter a positive number: 5
       Factorial = 120
       

       ---

       PART B: STRINGS

       14. Introduction to Strings

       A string is a sequence of characters enclosed within quotation marks.

       Python supports:

       • Single quotes: 'Python'
       • Double quotes: "Python"
       • Triple single quotes: '''Python'''
       • Triple double quotes: """Python"""

       Example

       name = "Rajesh"
       message = 'Welcome to Python'
       
       print(name)
       print(message)
       

       Output:

       Rajesh
       Welcome to Python
       

       Strings can contain letters, numbers, spaces, and special characters.

       text = "Computer Science 083!"
       

       ---

       15. String Indexing

       Each character in a string has an index.

       Python uses zero-based indexing.

       Consider:

       word = "PYTHON"
       

       Character	P	Y	T	H	O	N
       Positive index	0	1	2	3	4	5
       Negative index	-6	-5	-4	-3	-2	-1

       Example

       word = "PYTHON"
       
       print(word[0])
       print(word[3])
       print(word[-1])
       

       Output:

       P
       H
       N
       

       ---

       16. String Operations

       Important string operations include:

       1. Concatenation
       2. Repetition
       3. Membership
       4. Slicing

       ---

       16.1 String Concatenation

       Concatenation means joining two or more strings.

       The + operator is used for concatenation.

       first = "Hello"
       second = "Python"
       
       result = first + " " + second
       
       print(result)
       

       Output:

       Hello Python
       

       Important

       The + operator joins strings; it does not automatically convert numbers to strings.

       age = 16
       
       print("Age: " + str(age))
       

       ---

       17. String Repetition

       The * operator can repeat a string multiple times.

       word = "Hi "
       
       print(word * 3)
       

       Output:

       Hi Hi Hi
       

       Example

       print("*" * 5)
       

       Output:

       *****
       

       ---

       18. String Membership

       The in and not in operators check whether a substring or character exists in a string.

       Example

       text = "Python Programming"
       
       print("Python" in text)
       print("Java" in text)
       print("Java" not in text)
       

       Output:

       True
       False
       True
       

       ---

       19. String Slicing

       Slicing is used to extract a part of a string.

       Syntax

       string[start:stop:step]
       

       The stop index is excluded.

       Example

       word = "COMPUTER"
       
       print(word[0:4])
       

       Output:

       COMP
       

       More examples

       word = "PYTHON"
       
       print(word[1:4])
       print(word[:3])
       print(word[3:])
       print(word[::-1])
       

       Output:

       YTH
       PYT
       HON
       NOHTYP
       

       ---

       20. Traversing a String Using a Loop

       Traversing a string means accessing its characters one by one.

       Using a for loop

       word = "PYTHON"
       
       for ch in word:
           print(ch)
       

       Output:

       P
       Y
       T
       H
       O
       N
       

       Using indexing

       word = "PYTHON"
       
       for i in range(len(word)):
           print(word[i])
       

       Output:

       P
       Y
       T
       H
       O
       N
       

       ---

       21. len() Function

       len() returns the number of characters in a string.

       Example

       name = "Python"
       
       print(len(name))
       

       Output:

       6
       

       Spaces are also counted.

       text = "Hello World"
       print(len(text))
       

       Output:

       11
       

       ---

       22. String Methods

       Python provides many built-in string methods for processing text.

       ---

       22.1 capitalize()

       Converts the first character to uppercase and the remaining characters to lowercase.

       text = "python PROGRAMMING"
       
       print(text.capitalize())
       

       Output:

       Python programming
       

       ---

       22.2 title()

       Converts the first character of each word to uppercase.

       text = "computer science"
       
       print(text.title())
       

       Output:

       Computer Science
       

       ---

       22.3 lower()

       Converts letters to lowercase.

       text = "PYTHON"
       
       print(text.lower())
       

       Output:

       python
       

       ---

       22.4 upper()

       Converts letters to uppercase.

       text = "python"
       
       print(text.upper())
       

       Output:

       PYTHON
       

       ---

       22.5 count()

       Counts the number of occurrences of a substring.

       text = "banana"
       
       print(text.count("a"))
       

       Output:

       3
       

       Example

       text = "Python is easy. Python is popular."
       
       print(text.count("Python"))
       

       Output:

       2
       

       ---

       23. find()

       find() returns the index of the first occurrence of a substring.

       If the substring is not found, it returns -1.

       text = "Computer Science"
       
       print(text.find("Science"))
       print(text.find("Python"))
       

       Output:

       9
       -1
       

       ---

       24. index()

       index() returns the index of the first occurrence of a substring.

       text = "Computer Science"
       
       print(text.index("Science"))
       

       Output:

       9
       

       Difference between find() and index()

       find()	index()
       Returns the position if found.	Returns the position if found.
       Returns -1 if not found.	Raises ValueError if not found.

       Example:

       print("Python".find("Java"))
       

       Output:

       -1
       

       But:

       print("Python".index("Java"))
       

       causes a ValueError.

       ---

       25. endswith()

       Checks whether a string ends with a specified substring.

       filename = "notes.txt"
       
       print(filename.endswith(".txt"))
       

       Output:

       True
       

       ---

       26. startswith()

       Checks whether a string starts with a specified substring.

       website = "https://example.com"
       
       print(website.startswith("https"))
       

       Output:

       True
       

       ---

       27. isalnum()

       Returns True if all characters are alphanumeric — letters or digits — and the string is not empty.

       text = "Python123"
       
       print(text.isalnum())
       

       Output:

       True
       

       Example:

       print("Python 123".isalnum())
       

       Output:

       False
       

       The space is not alphanumeric.

       ---

       28. isalpha()

       Returns True if all characters are alphabetic and the string is not empty.

       text = "Python"
       
       print(text.isalpha())
       

       Output:

       True
       

       print("Python123".isalpha())
       

       Output:

       False
       

       ---

       29. isdigit()

       Returns True if all characters in the string are digits and the string is not empty.

       number = "12345"
       
       print(number.isdigit())
       

       Output:

       True
       

       print("123A".isdigit())
       

       Output:

       False
       

       ---

       30. islower()

       Returns True if the string has at least one cased character and all cased characters are lowercase.

       text = "python"
       
       print(text.islower())
       

       Output:

       True
       

       ---

       31. isupper()

       Returns True if the string has at least one cased character and all cased characters are uppercase.

       text = "PYTHON"
       
       print(text.isupper())
       

       Output:

       True
       

       ---

       32. isspace()

       Returns True if all characters in the string are whitespace characters and the string is not empty.

       text = "   "
       
       print(text.isspace())
       

       Output:

       True
       

       Example

       text = "Hello"
       
       print(text.isspace())
       

       Output:

       False
       

       ---

       33. lstrip()

       Removes leading whitespace from the left side of a string.

       text = "   Python"
       
       print(text.lstrip())
       

       Output:

       Python
       

       It can also remove specified characters from the left.

       text = "###Python"
       print(text.lstrip("#"))
       

       Output:

       Python
       

       ---

       34. rstrip()

       Removes trailing whitespace from the right side.

       text = "Python   "
       
       print(text.rstrip())
       

       Output:

       Python
       

       It can also remove specified characters from the right.

       text = "Python###"
       
       print(text.rstrip("#"))
       

       Output:

       Python
       

       ---

       35. strip()

       Removes leading and trailing whitespace.

       text = "   Python   "
       
       print(text.strip())
       

       Output:

       Python
       

       It can also remove specified characters from both ends.

       text = "###Python###"
       
       print(text.strip("#"))
       

       Output:

       Python
       

       Difference

       Method	Removes from
       lstrip()	Left side
       rstrip()	Right side
       strip()	Both sides

       ---

       36. replace()

       replace() replaces occurrences of one substring with another.

       Syntax

       string.replace(old, new)
       

       Example

       text = "I like Java"
       
       new_text = text.replace("Java", "Python")
       
       print(new_text)
       

       Output:

       I like Python
       

       Example

       text = "banana"
       
       print(text.replace("a", "o"))
       

       Output:

       bonono
       

       ---

       37. join()

       join() joins the elements of an iterable using a specified separator.

       Example

       words = ["Python", "is", "easy"]
       
       sentence = " ".join(words)
       
       print(sentence)
       

       Output:

       Python is easy
       

       Another example

       words = ["2026", "09", "20"]
       
       date = "-".join(words)
       
       print(date)
       

       Output:

       2026-09-20
       

       ---

       38. partition()

       partition() divides a string into three parts based on the first occurrence of a specified separator:

       1. Part before the separator
       2. Separator itself
       3. Part after the separator

       Example

       text = "name:Rajesh"
       
       result = text.partition(":")
       
       print(result)
       

       Output:

       ('name', ':', 'Rajesh')
       

       If the separator is not found, the original string is returned as the first element, followed by two empty strings.

       ---

       39. split()

       split() divides a string into a list of substrings.

       Example

       text = "Python is easy"
       
       words = text.split()
       
       print(words)
       

       Output:

       ['Python', 'is', 'easy']
       

       By default, whitespace is used as the separator.

       Example with a separator

       data = "A,B,C,D"
       
       items = data.split(",")
       
       print(items)
       

       Output:

       ['A', 'B', 'C', 'D']
       

       ---

       40. Important String Functions and Methods – Quick Table

       Function / Method	Purpose	Example
       len()	Returns length	len("Python")
       capitalize()	Capitalises first character	"python".capitalize()
       title()	Capitalises each word	"hello world".title()
       lower()	Converts to lowercase	"PYTHON".lower()
       upper()	Converts to uppercase	"python".upper()
       count()	Counts occurrences	"banana".count("a")
       find()	Finds position; returns -1 if absent	"Python".find("th")
       index()	Finds position; raises error if absent	"Python".index("th")
       endswith()	Checks ending	"file.txt".endswith(".txt")
       startswith()	Checks beginning	"Python".startswith("Py")
       isalnum()	Checks letters/digits only	"abc123".isalnum()
       isalpha()	Checks alphabetic characters	"Python".isalpha()
       isdigit()	Checks digits	"123".isdigit()
       islower()	Checks lowercase	"python".islower()
       isupper()	Checks uppercase	"PYTHON".isupper()
       isspace()	Checks whitespace only	" ".isspace()
       lstrip()	Removes leading whitespace/characters	" Python".lstrip()
       rstrip()	Removes trailing whitespace/characters	"Python ".rstrip()
       strip()	Removes both leading/trailing whitespace	" Python ".strip()
       replace()	Replaces substring	"Java".replace("Java","Python")
       join()	Joins strings	"-".join(["A","B"])
       partition()	Splits into 3 parts around first separator	"A:B".partition(":")
       split()	Splits into a list	"A,B".split(",")

       ---

       41. Complete String Example

       text = "  Python Programming  "
       
       print("Original:", text)
       print("Length:", len(text))
       print("Upper:", text.upper())
       print("Lower:", text.lower())
       print("Title:", text.title())
       print("Stripped:", text.strip())
       print("Starts with Python:", text.strip().startswith("Python"))
       print("Ends with ing:", text.strip().endswith("ing"))
       print("Count of m:", text.count("m"))
       print("Find Python:", text.find("Python"))
       

       Output:

       Original:   Python Programming
       Length: 21
       Upper:   PYTHON PROGRAMMING
       Lower:   python programming
       Title:   Python Programming
       Stripped: Python Programming
       Starts with Python: True
       Ends with ing: True
       Count of m: 2
       Find Python: 2
       

       ---

       42. Important Points About Strings

       1. A string is a sequence of characters.
       2. String indexing starts from 0.
       3. Negative indexing starts from -1.
       4. Strings support concatenation using +.
       5. Strings support repetition using *.
       6. in and not in are used for membership testing.
       7. Slicing is used to extract a part of a string.
       8. Strings are immutable.
       9. String methods generally return a new string rather than modifying the original string.
       10. len() returns the number of characters.
       11. find() returns -1 when the substring is not found.
       12. index() raises ValueError when the substring is not found.
       13. split() returns a list.
       14. join() combines elements of an iterable into a string.

       ---

       43. Important Exam Programs

       Program 1: Count Vowels in a String

       text = input("Enter a string: ")
       
       count = 0
       
       for ch in text:
           if ch.lower() in "aeiou":
               count += 1
       
       print("Number of vowels =", count)
       

       Sample Output

       Enter a string: Computer Science
       Number of vowels = 6
       

       ---

       Program 2: Reverse a String Using a Loop

       text = input("Enter a string: ")
       
       reverse = ""
       
       for ch in text:
           reverse = ch + reverse
       
       print("Reverse =", reverse)
       

       Sample Output

       Enter a string: Python
       Reverse = nohtyP
       

       ---

       Program 3: Check Palindrome

       A palindrome is a word or string that reads the same forwards and backwards.

       Examples:

       MADAM
       LEVEL
       RADAR
       

       Program

       text = input("Enter a string: ")
       
       if text == text[::-1]:
           print("Palindrome")
       else:
           print("Not a palindrome")
       

       Sample Output

       Enter a string: MADAM
       Palindrome
       

       ---

       Program 4: Count Digits in a String

       text = input("Enter a string: ")
       
       count = 0
       
       for ch in text:
           if ch.isdigit():
               count += 1
       
       print("Number of digits =", count)
       

       ---

       Program 5: Print Multiplication Table

       n = int(input("Enter a number: "))
       
       for i in range(1, 11):
           print(n, "x", i, "=", n * i)
       

       For input 5:

       5 x 1 = 5
       5 x 2 = 10
       5 x 3 = 15
       5 x 4 = 20
       5 x 5 = 25
       5 x 6 = 30
       5 x 7 = 35
       5 x 8 = 40
       5 x 9 = 45
       5 x 10 = 50
       

       ---

       44. Quick Revision

       Iterative Statements

       • Iteration means repeating statements.
       • Python provides for and while loops.
       • range() generates a sequence of numbers.
       • break terminates the nearest enclosing loop.
       • continue skips the current iteration.
       • A loop inside another loop is called a nested loop.
       • Nested loops are useful for generating patterns.
       • Loops can be used to calculate sums and factorials.

       Strings

       • A string is a sequence of characters.
       • Strings are immutable.
       • Indexing starts from 0.
       • Negative indexing starts from -1.
       • + performs concatenation.
       • * performs repetition.
       • in and not in perform membership testing.
       • Slicing extracts a part of a string.
       • len() returns string length.
       • String methods provide useful text-processing operations.
       • split() converts a string into a list.
       • join() combines strings.
       • replace() replaces specified text.
       • partition() divides a string into three parts.
       • find() returns -1 if text is not found.
       • index() raises an error if text is not found.

       ---

       45. Important CBSE Exam Questions

       Short Answer Questions

       1. What is iteration?
       2. Name the two iterative statements in Python.
       3. What is the purpose of the range() function?
       4. Differentiate between break and continue.
       5. What is a nested loop?
       6. What is an infinite loop?
       7. What is a string?
       8. What is string indexing?
       9. What is string slicing?
       10. Why are strings called immutable?
       11. What is the purpose of len()?
       12. Differentiate between find() and index().
       13. What is the use of split()?
       14. What is the use of join()?
       15. Differentiate between strip(), lstrip() and rstrip().

       Programming Questions

       1. Write a Python program to print numbers from 1 to 10 using a for loop.
       2. Write a Python program to print even numbers from 1 to 50.
       3. Write a Python program to calculate the sum of numbers from 1 to n.
       4. Write a Python program to calculate the factorial of a positive number.
       5. Write a Python program to generate a triangular star pattern.
       6. Write a Python program to generate a multiplication table.
       7. Write a Python program to count vowels in a string.
       8. Write a Python program to reverse a string.
       9. Write a Python program to check whether a string is a palindrome.
       10. Write a Python program to count the number of digits in a string.
       11. Write a Python program to count occurrences of a particular character in a string.
       12. Write a Python program to check whether a string contains only alphabets.
       13. Write a Python program to replace one word with another in a string.
       14. Write a Python program to split a sentence into words.
       15. Write a Python program to join a list of words into a sentence.

       ______________________RUonTop________________________

       1. LISTS

       1.1 Introduction to Lists

       A list is an ordered collection of items in Python.

       A list can contain:

       • Numbers
       • Strings
       • Characters
       • Boolean values
       • Other lists
       • Mixed data types

       Lists are written using square brackets [ ].

       Example

       marks = [75, 82, 91, 68, 88]
       names = ["Amit", "Riya", "Neha"]
       mixed = [10, "Python", 3.5, True]

       Important Features of Lists

       1. Lists are ordered.
       2. Lists are mutable, which means their elements can be changed.
       3. Lists allow duplicate values.
       4. Lists support indexing and slicing.
       5. Lists can contain different data types.
       6. A list can contain another list.

       ---

       2. List Indexing

       Each item in a list has a position called an index.

       Python uses zero-based indexing.

       List:       [10, 20, 30, 40, 50]
       Index:        0   1   2   3   4
       Negative:    -5  -4  -3  -2  -1

       Example

       numbers = [10, 20, 30, 40, 50]
       
       print(numbers[0])
       print(numbers[2])
       print(numbers[-1])

       Output

       10
       30
       50

       Changing an Item

       Because lists are mutable:

       numbers = [10, 20, 30]
       numbers[1] = 99
       
       print(numbers)

       Output:

       [10, 99, 30]

       ---

       3. List Operations

       3.1 Concatenation

       The + operator joins two lists.

       a = [1, 2, 3]
       b = [4, 5, 6]
       
       c = a + b
       print(c)

       Output:

       [1, 2, 3, 4, 5, 6]

       ---

       3.2 Repetition

       The * operator repeats a list.

       a = [1, 2]
       
       print(a * 3)

       Output:

       [1, 2, 1, 2, 1, 2]

       ---

       3.3 Membership

       The operators in and not in check whether an item exists in a list.

       numbers = [10, 20, 30, 40]
       
       print(20 in numbers)
       print(50 in numbers)
       print(50 not in numbers)

       Output:

       True
       False
       True

       ---

       3.4 Slicing

       Slicing is used to extract a portion of a list.

       Syntax

       list[start:stop]

       The stop index is not included.

       numbers = [10, 20, 30, 40, 50]
       
       print(numbers[1:4])

       Output:

       [20, 30, 40]

       Other Examples

       numbers[:3]      # First three elements
       numbers[2:]      # From index 2 to end
       numbers[:]       # Complete list
       numbers[::2]     # Every second element
       numbers[::-1]    # Reverse order

       ---

       4. Traversing a List Using Loops

       Traversing means visiting each element of a list one by one.

       Using for Loop

       numbers = [10, 20, 30, 40, 50]
       
       for x in numbers:
           print(x)

       Output:

       10
       20
       30
       40
       50

       Traversing Using Index

       numbers = [10, 20, 30, 40]
       
       for i in range(len(numbers)):
           print(numbers[i])

       ---

       5. List Built-in Functions and Methods

       5.1 len()

       Returns the number of elements.

       numbers = [10, 20, 30, 40]
       
       print(len(numbers))

       Output:

       4

       ---

       5.2 list()

       Converts an iterable into a list.

       text = "PYTHON"
       
       x = list(text)
       
       print(x)

       Output:

       ['P', 'Y', 'T', 'H', 'O', 'N']

       ---

       5.3 append()

       Adds one item at the end of a list.

       numbers = [10, 20, 30]
       
       numbers.append(40)
       
       print(numbers)

       Output:

       [10, 20, 30, 40]

       Important

       append() adds its argument as a single element.

       a = [1, 2]
       a.append([3, 4])
       
       print(a)

       Output:

       [1, 2, [3, 4]]

       ---

       5.4 extend()

       Adds multiple elements from another iterable.

       a = [1, 2]
       a.extend([3, 4, 5])
       
       print(a)

       Output:

       [1, 2, 3, 4, 5]

       Difference

       append([3,4])  → [1,2,[3,4]]
       extend([3,4])  → [1,2,3,4]

       ---

       5.5 insert()

       Adds an element at a specified position.

       Syntax

       list.insert(index, value)

       Example:

       numbers = [10, 20, 40]
       
       numbers.insert(2, 30)
       
       print(numbers)

       Output:

       [10, 20, 30, 40]

       ---

       5.6 count()

       Returns the number of times an element occurs.

       numbers = [10, 20, 10, 30, 10]
       
       print(numbers.count(10))

       Output:

       3

       ---

       5.7 index()

       Returns the index of the first occurrence of an item.

       numbers = [10, 20, 30, 20]
       
       print(numbers.index(20))

       Output:

       1

       If the value is not present, index() raises a ValueError.

       ---

       5.8 remove()

       Removes the first occurrence of a specified value.

       numbers = [10, 20, 30, 20]
       
       numbers.remove(20)
       
       print(numbers)

       Output:

       [10, 30, 20]

       ---

       5.9 pop()

       Removes and returns an element.

       numbers = [10, 20, 30, 40]
       
       x = numbers.pop()
       
       print(x)
       print(numbers)

       Output:

       40
       [10, 20, 30]

       With Index

       numbers.pop(1)

       This removes the element at index 1.

       ---

       5.10 reverse()

       Reverses the list in place.

       numbers = [10, 20, 30, 40]
       
       numbers.reverse()
       
       print(numbers)

       Output:

       [40, 30, 20, 10]

       ---

       5.11 sort()

       Sorts the list in ascending order by default.

       numbers = [50, 10, 40, 20, 30]
       
       numbers.sort()
       
       print(numbers)

       Output:

       [10, 20, 30, 40, 50]

       Descending Order

       numbers.sort(reverse=True)

       ---

       5.12 sorted()

       sorted() returns a new sorted list and does not change the original list.

       numbers = [40, 10, 30, 20]
       
       new_list = sorted(numbers)
       
       print(new_list)
       print(numbers)

       Output:

       [10, 20, 30, 40]
       [40, 10, 30, 20]

       sort() vs sorted()

       sort()	sorted()
       List method	Built-in function
       Changes original list	Returns a new sorted list
       Used with lists	Can work with many iterables

       ---

       6. min(), max() and sum()

       min()

       Finds the smallest value.

       numbers = [10, 30, 5, 20]
       
       print(min(numbers))

       Output:

       5

       max()

       Finds the largest value.

       print(max(numbers))

       Output:

       30

       sum()

       Calculates the total of numeric elements.

       print(sum(numbers))

       Output:

       65

       ---

       7. Nested Lists

       A list containing another list is called a nested list.

       data = [[10, 20], [30, 40], [50, 60]]

       It can be visualised as:

       data
        ├── [10, 20]
        ├── [30, 40]
        └── [50, 60]

       Accessing Elements

       print(data[0])
       print(data[1][0])

       Output:

       [10, 20]
       30

       Nested Loop

       data = [[1, 2], [3, 4], [5, 6]]
       
       for row in data:
           for value in row:
               print(value)

       ---

       8. Suggested List Programs

       Program 1: Find Maximum and Minimum

       numbers = [25, 10, 45, 5, 30]
       
       print("Maximum =", max(numbers))
       print("Minimum =", min(numbers))

       Output:

       Maximum = 45
       Minimum = 5

       ---

       Program 2: Find Mean of Values in a List

       Mean is:

       Mean = Sum of values / Number of values

       Program:

       numbers = [10, 20, 30, 40, 50]
       
       mean = sum(numbers) / len(numbers)
       
       print("Mean =", mean)

       Output:

       Mean = 30.0

       ---

       Program 3: Linear Search in a List

       Linear search checks elements one by one until the required element is found.

       numbers = [10, 25, 30, 45, 50]
       
       key = int(input("Enter number to search: "))
       
       found = False
       
       for x in numbers:
           if x == key:
               found = True
               break
       
       if found:
           print("Element found")
       else:
           print("Element not found")

       ---

       Program 4: Linear Search Using Index

       numbers = [10, 20, 30, 40, 50]
       
       key = int(input("Enter number: "))
       
       found = False
       
       for i in range(len(numbers)):
           if numbers[i] == key:
               print("Element found at index", i)
               found = True
               break
       
       if not found:
           print("Element not found")

       ---

       Program 5: Count Frequency of an Element

       numbers = [10, 20, 10, 30, 10, 40]
       
       key = int(input("Enter number: "))
       
       count = 0
       
       for x in numbers:
           if x == key:
               count += 1
       
       print("Frequency =", count)

       ---

       9. TUPLES

       9.1 Introduction to Tuples

       A tuple is an ordered collection of elements.

       Tuples are generally written using parentheses ( ).

       numbers = (10, 20, 30, 40)
       names = ("Amit", "Riya", "Neha")

       A tuple can also contain mixed data types:

       data = (10, "Python", 3.5, True)

       Important Features

       1. Tuples are ordered.
       2. Tuples support indexing.
       3. Tuples support slicing.
       4. Tuples allow duplicate values.
       5. Tuples can contain different data types.
       6. Tuples are immutable.
       7. Tuples can be nested.

       ---

       10. Tuple Indexing

       Tuple indexing is similar to list indexing.

       t = (10, 20, 30, 40, 50)
       
       print(t[0])
       print(t[2])
       print(t[-1])

       Output:

       10
       30
       50

       Because tuples are immutable, this is not allowed:

       t[1] = 100

       It produces a TypeError.

       ---

       11. Tuple Operations

       11.1 Concatenation

       a = (1, 2, 3)
       b = (4, 5)
       
       print(a + b)

       Output:

       (1, 2, 3, 4, 5)

       ---

       11.2 Repetition

       a = (1, 2)
       
       print(a * 3)

       Output:

       (1, 2, 1, 2, 1, 2)

       ---

       11.3 Membership

       t = (10, 20, 30)
       
       print(20 in t)
       print(50 not in t)

       Output:

       True
       True

       ---

       11.4 Slicing

       t = (10, 20, 30, 40, 50)
       
       print(t[1:4])

       Output:

       (20, 30, 40)

       Other examples:

       t[:3]
       t[2:]
       t[::-1]

       ---

       12. Tuple Built-in Functions and Methods

       12.1 len()

       t = (10, 20, 30, 40)
       
       print(len(t))

       Output:

       4

       ---

       12.2 tuple()

       Converts an iterable into a tuple.

       x = tuple([10, 20, 30])
       
       print(x)

       Output:

       (10, 20, 30)

       ---

       12.3 count()

       Counts occurrences of an element.

       t = (10, 20, 10, 30, 10)
       
       print(t.count(10))

       Output:

       3

       ---

       12.4 index()

       Returns the index of the first occurrence.

       t = (10, 20, 30, 20)
       
       print(t.index(20))

       Output:

       1

       ---

       12.5 sorted()

       Returns a new list containing the sorted elements.

       t = (30, 10, 20)
       
       print(sorted(t))

       Output:

       [10, 20, 30]

       Important

       Although the original object is a tuple, sorted() returns a list.

       ---

       12.6 min(), max() and sum()

       t = (10, 20, 30, 40)
       
       print(min(t))
       print(max(t))
       print(sum(t))

       Output:

       10
       40
       100

       ---

       13. Tuple Assignment

       Python allows multiple variables to be assigned values at the same time.

       a, b, c = 10, 20, 30
       
       print(a)
       print(b)
       print(c)

       This is called multiple assignment or tuple assignment.

       Example: Swapping Values

       a = 10
       b = 20
       
       a, b = b, a
       
       print(a)
       print(b)

       Output:

       20
       10

       ---

       14. Nested Tuples

       A tuple can contain another tuple.

       t = ((10, 20), (30, 40), (50, 60))

       Accessing elements:

       print(t[0])
       print(t[1][1])

       Output:

       (10, 20)
       40

       ---

       15. Suggested Tuple Programs

       Program 1: Maximum, Minimum and Mean

       numbers = (10, 20, 30, 40, 50)
       
       print("Maximum =", max(numbers))
       print("Minimum =", min(numbers))
       
       mean = sum(numbers) / len(numbers)
       
       print("Mean =", mean)

       Output:

       Maximum = 50
       Minimum = 10
       Mean = 30.0

       ---

       Program 2: Linear Search in Tuple

       numbers = (10, 20, 30, 40, 50)
       
       key = int(input("Enter number: "))
       
       found = False
       
       for x in numbers:
           if x == key:
               found = True
               break
       
       if found:
           print("Element found")
       else:
           print("Element not found")

       ---

       Program 3: Frequency of an Element

       numbers = (10, 20, 10, 30, 10, 40)
       
       key = int(input("Enter number: "))
       
       count = 0
       
       for x in numbers:
           if x == key:
               count += 1
       
       print("Frequency =", count)

       ---

       16. LIST vs TUPLE

       Feature	List	Tuple
       Brackets	[ ]	( )
       Ordered	Yes	Yes
       Mutable	Yes	No
       Indexing	Yes	Yes
       Slicing	Yes	Yes
       Duplicates	Allowed	Allowed
       append()	Available	Not available
       remove()	Available	Not available
       sort()	Available	Not available
       count()	Available	Available
       index()	Available	Available

       Easy Memory Trick

       LIST  → Mutable
       TUPLE → Immutable

       ---

       17. DICTIONARY

       17.1 Introduction

       A dictionary is a collection of key-value pairs.

       It is written using curly brackets { }.

       Example

       student = {
           "name": "Amit",
           "age": 16,
           "marks": 85
       }

       Here:

       "name"  → key
       "Amit"  → value
       
       "age"   → key
       16      → value
       
       "marks" → key
       85      → value

       A dictionary is useful when data needs to be stored with meaningful keys.

       ---

       18. Accessing Items Using Keys

       Dictionary values are accessed using their keys.

       student = {
           "name": "Amit",
           "age": 16,
           "marks": 85
       }
       
       print(student["name"])
       print(student["marks"])

       Output:

       Amit
       85

       Important

       If a key does not exist, using:

       student["city"]

       causes a KeyError.

       The get() method can be used when you want to avoid this behaviour.

       ---

       19. Mutability of Dictionary

       Dictionaries are mutable.

       This means we can:

       • Add a new item
       • Modify an existing item
       • Delete an item

       ---

       19.1 Adding a New Item

       student = {
           "name": "Amit",
           "marks": 85
       }
       
       student["age"] = 16
       
       print(student)

       ---

       19.2 Modifying an Existing Item

       student["marks"] = 90
       
       print(student)

       The value associated with the key "marks" is changed.

       ---

       20. Traversing a Dictionary

       Traversing Keys

       student = {
           "name": "Amit",
           "age": 16,
           "marks": 85
       }
       
       for key in student:
           print(key)

       ---

       Traversing Values

       for value in student.values():
           print(value)

       ---

       Traversing Keys and Values

       for key, value in student.items():
           print(key, value)

       Output:

       name Amit
       age 16
       marks 85

       ---

       21. Dictionary Functions and Methods

       21.1 len()

       Returns the number of key-value pairs.

       student = {"name": "Amit", "age": 16, "marks": 85}
       
       print(len(student))

       Output:

       3

       ---

       21.2 dict()

       Creates a dictionary.

       student = dict(name="Amit", age=16)
       
       print(student)

       Output:

       {'name': 'Amit', 'age': 16}

       ---

       21.3 keys()

       Returns a view containing dictionary keys.

       student = {"name": "Amit", "age": 16}
       
       print(student.keys())

       To traverse:

       for key in student.keys():
           print(key)

       ---

       21.4 values()

       Returns the dictionary values.

       for value in student.values():
           print(value)

       ---

       21.5 items()

       Returns key-value pairs.

       for key, value in student.items():
           print(key, value)

       ---

       21.6 get()

       Returns the value associated with a key.

       student = {"name": "Amit", "marks": 85}
       
       print(student.get("name"))

       Output:

       Amit

       If the key is absent:

       print(student.get("city"))

       returns:

       None

       A default value can also be supplied:

       print(student.get("city", "Not Available"))

       Output:

       Not Available

       ---

       21.7 update()

       Adds or modifies multiple key-value pairs.

       student = {"name": "Amit", "marks": 80}
       
       student.update({"marks": 90, "age": 16})
       
       print(student)

       ---

       21.8 del

       del is a Python statement used to delete a dictionary item.

       student = {
           "name": "Amit",
           "age": 16,
           "marks": 85
       }
       
       del student["age"]
       
       print(student)

       ---

       21.9 clear()

       Removes all items.

       student.clear()
       
       print(student)

       Output:

       {}

       ---

       21.10 fromkeys()

       Creates a dictionary from a sequence of keys.

       keys = ["Name", "Age", "City"]
       
       student = dict.fromkeys(keys)
       
       print(student)

       Output:

       {'Name': None, 'Age': None, 'City': None}

       A common value can also be provided:

       student = dict.fromkeys(keys, "Unknown")

       ---

       21.11 copy()

       Creates a shallow copy of a dictionary.

       student = {"name": "Amit", "marks": 85}
       
       new_student = student.copy()
       
       print(new_student)

       ---

       21.12 pop()

       Removes the specified key and returns its value.

       student = {
           "name": "Amit",
           "age": 16,
           "marks": 85
       }
       
       x = student.pop("age")
       
       print(x)
       print(student)

       Output:

       16
       {'name': 'Amit', 'marks': 85}

       ---

       21.13 popitem()

       Removes and returns the last inserted key-value pair.

       student = {
           "name": "Amit",
           "age": 16,
           "marks": 85
       }
       
       x = student.popitem()
       
       print(x)
       print(student)

       ---

       21.14 setdefault()

       Returns the value of a key.

       If the key does not exist, it inserts the key with the specified default value.

       student = {"name": "Amit"}
       
       student.setdefault("age", 16)
       
       print(student)

       Output:

       {'name': 'Amit', 'age': 16}

       If "name" already exists:

       student.setdefault("name", "Riya")

       the existing value is not replaced.

       ---

       22. max(), min() and sorted() with Dictionary

       max()

       By default, max() operates on dictionary keys.

       d = {"b": 20, "a": 10, "c": 30}
       
       print(max(d))

       Output:

       c

       min()

       print(min(d))

       Output:

       a

       sorted()

       sorted() returns a list of sorted keys by default.

       d = {"b": 20, "a": 10, "c": 30}
       
       print(sorted(d))

       Output:

       ['a', 'b', 'c']

       Important

       For dictionaries, max(), min() and sorted() normally work with keys, unless another iterable such as values() or items() is explicitly supplied.

       ---

       23. Suggested Dictionary Program: Character Frequency

       Problem

       Write a program to count how many times each character appears in a string using a dictionary.

       Program

       text = input("Enter a string: ")
       
       frequency = {}
       
       for ch in text:
           if ch in frequency:
               frequency[ch] += 1
           else:
               frequency[ch] = 1
       
       print(frequency)

       Example Input

       banana

       Output

       {'b': 1, 'a': 3, 'n': 2}

       Explanation

       For every character:

       • If it already exists as a key, increase its value.
       • Otherwise, create the key with value 1.

       ---

       24. Character Frequency Using get()

       The same program can be written more compactly:

       text = input("Enter a string: ")
       
       frequency = {}
       
       for ch in text:
           frequency[ch] = frequency.get(ch, 0) + 1
       
       print(frequency)

       For:

       apple

       Output:

       {'a': 1, 'p': 2, 'l': 1, 'e': 1}

       ---

       25. Employee Dictionary Program

       Problem

       Create a dictionary containing employee names and their salaries and access the information.

       Program

       employees = {
           "Amit": 35000,
           "Riya": 42000,
           "Neha": 38000
       }
       
       for name, salary in employees.items():
           print("Employee:", name)
           print("Salary:", salary)

       Output:

       Employee: Amit
       Salary: 35000
       Employee: Riya
       Salary: 42000
       Employee: Neha
       Salary: 38000

       ---

       26. Employee Details Using Nested Dictionary

       For storing multiple details for each employee:

       employees = {
           "E101": {
               "name": "Amit",
               "salary": 35000
           },
           "E102": {
               "name": "Riya",
               "salary": 42000
           }
       }
       
       print(employees["E101"]["name"])
       print(employees["E101"]["salary"])

       Output:

       Amit
       35000

       This is an example of a nested dictionary.

       ---

       27. LIST, TUPLE AND DICTIONARY – Quick Comparison

       Feature	List	Tuple	Dictionary
       Syntax	[ ]	( )	{key:value}
       Ordered	Yes	Yes	Yes*
       Mutable	Yes	No	Yes
       Access	Index	Index	Key
       Duplicate elements	Yes	Yes	Keys must be unique
       Slicing	Yes	Yes	No
       Main purpose	Collection of items	Fixed collection	Key-value data

       * Modern Python dictionaries preserve insertion order.

       ---

       28. INTRODUCTION TO PYTHON MODULES

       28.1 What is a Module?

       A module is a Python file containing functions, variables, classes or other Python code that can be reused in another program.

       Python provides many built-in modules.

       Examples:

       math
       random
       statistics

       Modules help programmers:

       • Reuse code
       • Organise programs
       • Avoid writing common functions again
       • Access ready-made functionality

       ---

       29. Importing a Module Using import

       Syntax

       import module_name

       Example:

       import math
       
       print(math.sqrt(25))

       Output:

       5.0

       Here:

       math → module
       sqrt → function

       The dot . is used to access members of the module.

       ---

       30. Importing Using from

       A particular function can be imported from a module.

       Syntax

       from module_name import function_name

       Example:

       from math import sqrt
       
       print(sqrt(25))

       Now we can use sqrt() directly.

       Importing Multiple Functions

       from math import sqrt, ceil, floor

       ---

       31. import vs from ... import

       import	from ... import
       Imports the module	Imports selected members
       Use module name with dot	Can use imported member directly
       math.sqrt(25)	sqrt(25)

       ---

       32. MATH MODULE

       The math module provides mathematical functions and constants.

       First import it:

       import math

       ---

       32.1 math.pi

       Represents the mathematical constant π.

       import math
       
       print(math.pi)

       ---

       32.2 math.e

       Represents Euler's number.

       print(math.e)

       ---

       32.3 math.sqrt()

       Returns the square root.

       print(math.sqrt(49))

       Output:

       7.0

       ---

       32.4 math.ceil()

       Returns the smallest integer greater than or equal to a number.

       print(math.ceil(4.2))

       Output:

       5

       ---

       32.5 math.floor()

       Returns the largest integer less than or equal to a number.

       print(math.floor(4.8))

       Output:

       4

       ceil() vs floor()

       ceil(4.2)  → 5
       floor(4.8) → 4

       ---

       32.6 math.pow()

       Returns a number raised to a power.

       print(math.pow(2, 3))

       Output:

       8.0

       ---

       32.7 math.fabs()

       Returns the absolute value of a number as a floating-point value.

       print(math.fabs(-15))

       Output:

       15.0

       ---

       33. Trigonometric Functions

       The math module provides:

       sin()
       cos()
       tan()

       Example

       import math
       
       print(math.sin(0))
       print(math.cos(0))
       print(math.tan(0))

       Output:

       0.0
       1.0
       0.0

       Important

       The trigonometric functions in Python's math module use radians, not degrees.

       For example:

       print(math.sin(math.pi / 2))

       Output:

       1.0

       ---

       34. MATH MODULE QUICK TABLE

       Function/Constant	Purpose	Example
       math.pi	Value of π	math.pi
       math.e	Euler's number	math.e
       math.sqrt(x)	Square root	math.sqrt(25)
       math.ceil(x)	Round upward	math.ceil(4.2)
       math.floor(x)	Round downward	math.floor(4.8)
       math.pow(x,y)	x raised to y	math.pow(2,3)
       math.fabs(x)	Absolute float value	math.fabs(-5)
       math.sin(x)	Sine	math.sin(x)
       math.cos(x)	Cosine	math.cos(x)
       math.tan(x)	Tangent	math.tan(x)

       ---

       35. RANDOM MODULE

       The random module is used to generate pseudo-random values.

       Import it using:

       import random

       ---

       35.1 random.random()

       Returns a random floating-point number from:

       0.0 ≤ number < 1.0

       Example:

       import random
       
       print(random.random())

       A possible output could be:

       0.638421

       The output can be different each time.

       ---

       35.2 random.randint()

       Returns a random integer between two specified values, including both endpoints.

       import random
       
       print(random.randint(1, 10))

       Possible output:

       7

       It can produce any integer from 1 through 10.

       ---

       35.3 random.randrange()

       Returns a randomly selected value from a range.

       print(random.randrange(1, 10))

       Possible values:

       1, 2, 3, ..., 9

       The stop value 10 is excluded.

       It can also use start and step:

       random.randrange(2, 20, 2)

       Possible values:

       2, 4, 6, 8, ..., 18

       ---

       36. randint() vs randrange()

       randint(a,b)	randrange(a,b)
       Includes b	Excludes b
       randint(1,10) → 1 to 10	randrange(1,10) → 1 to 9
       Returns integer	Returns integer

       ---

       37. STATISTICS MODULE

       The statistics module provides functions for basic statistical calculations.

       Import:

       import statistics

       ---

       37.1 mean()

       The mean is the arithmetic average.

       import statistics
       
       numbers = [10, 20, 30, 40, 50]
       
       print(statistics.mean(numbers))

       Output:

       30

       ---

       37.2 median()

       The median is the middle value when the data is arranged in sorted order.

       numbers = [10, 20, 30, 40, 50]
       
       print(statistics.median(numbers))

       Output:

       30

       For an even number of values:

       numbers = [10, 20, 30, 40]
       
       print(statistics.median(numbers))

       Output:

       25.0

       ---

       37.3 mode()

       The mode is the most frequently occurring value.

       numbers = [10, 20, 20, 30, 20, 40]
       
       print(statistics.mode(numbers))

       Output:

       20

       ---

       38. Importing Statistics Functions Directly

       Instead of:

       import statistics
       
       print(statistics.mean([10, 20, 30]))

       we can write:

       from statistics import mean
       
       print(mean([10, 20, 30]))

       Multiple functions:

       from statistics import mean, median, mode

       Then:

       numbers = [10, 20, 20, 30]
       
       print(mean(numbers))
       print(median(numbers))
       print(mode(numbers))

       ---

       39. Complete Module Example

       import math
       import random
       import statistics
       
       numbers = [10, 20, 20, 30, 40]
       
       print("Square Root:", math.sqrt(25))
       print("Random Number:", random.randint(1, 10))
       print("Mean:", statistics.mean(numbers))
       print("Median:", statistics.median(numbers))
       print("Mode:", statistics.mode(numbers))

       Possible output:

       Square Root: 5.0
       Random Number: 7
       Mean: 24
       Median: 20
       Mode: 20

       The random number may be different each time.

       ---

       40. IMPORTANT DIFFERENCES

       append() vs extend()

       a = [1, 2]
       
       a.append([3, 4])

       Result:

       [1, 2, [3, 4]]

       Whereas:

       a = [1, 2]
       
       a.extend([3, 4])

       Result:

       [1, 2, 3, 4]

       ---

       remove() vs pop()

       remove()	pop()
       Removes by value	Removes by index
       Does not return removed item	Returns removed item
       a.remove(20)	a.pop(1)

       ---

       sort() vs sorted()

       sort()    → changes original list
       sorted()  → returns a new sorted list

       ---

       List vs Tuple

       List  → [10, 20, 30]
       Tuple → (10, 20, 30)

       List  → Mutable
       Tuple → Immutable

       ---

       Dictionary Access

       student["name"]

       accesses a value directly using its key.

       Whereas:

       student.get("name")

       also accesses the value but provides a safer way to handle a missing key.

       ---

       41. QUICK REVISION

       Lists

       • List is an ordered and mutable collection.
       • Uses [ ].
       • Supports indexing and slicing.
       • Important methods: append(), extend(), insert(), remove(), pop(), reverse(), sort().
       • Important functions: len(), list(), min(), max(), sum(), sorted().

       Tuples

       • Tuple is ordered and immutable.
       • Usually uses ( ).
       • Supports indexing, slicing and membership.
       • Important methods: count(), index().
       • Important functions: len(), tuple(), sorted(), min(), max(), sum().

       Dictionary

       • Stores data as key-value pairs.
       • Uses { }.
       • Accessed using keys.
       • Mutable.
       • Important methods: keys(), values(), items(), get(), update(), clear(), copy(), pop(), popitem(), setdefault().

       Modules

       • A module is reusable Python code.
       • import imports a module.
       • from ... import imports selected members.
       • math provides mathematical functions.
       • random provides random-number functions.
       • statistics provides statistical functions.

       ---

       42. IMPORTANT EXAM QUESTIONS

       Very Short Answer Questions

       1. What is a list?
       2. What is the difference between a list and a tuple?
       3. What is indexing?
       4. What is slicing?
       5. What is the purpose of append()?
       6. What is the difference between append() and extend()?
       7. What is the use of pop()?
       8. What does sort() do?
       9. What is the difference between sort() and sorted()?
       10. What is a nested list?
       11. What is a tuple?
       12. Why is a tuple called immutable?
       13. What is tuple assignment?
       14. What is a dictionary?
       15. What is a key-value pair?
       16. How can an item be accessed from a dictionary?
       17. What is the purpose of keys()?
       18. What is the purpose of items()?
       19. What is the difference between get() and direct key access?
       20. What is a module?
       21. How do you import the math module?
       22. What is the use of math.sqrt()?
       23. What is the difference between randint() and randrange()?
       24. What is the use of statistics.mean()?

       ---

       43. Important Programming Questions

       Students should practise the following programs:

       Lists

       1. Create a list and display all its elements.
       2. Find the maximum value in a list.
       3. Find the minimum value in a list.
       4. Calculate the mean of numbers stored in a list.
       5. Search for an element using linear search.
       6. Count the frequency of a given element.
       7. Sort a list in ascending order.
       8. Sort a list in descending order.
       9. Reverse a list.
       10. Count even and odd numbers in a list.

       Tuples

       1. Create a tuple and display its elements.
       2. Find maximum and minimum values.
       3. Find the mean of tuple elements.
       4. Perform linear search.
       5. Count the frequency of an element.
       6. Demonstrate tuple assignment.
       7. Demonstrate nested tuples.

       Dictionaries

       1. Create a student dictionary.
       2. Add a new key-value pair.
       3. Modify an existing value.
       4. Display all keys.
       5. Display all values.
       6. Display all key-value pairs.
       7. Create a character-frequency dictionary.
       8. Create an employee-salary dictionary.
       9. Search for an employee's salary.
       10. Delete an item from a dictionary.

       Modules

       1. Find the square root using math.
       2. Find ceiling and floor values.
       3. Generate a random integer.
       4. Generate a random number using randrange().
       5. Find mean, median and mode using statistics.

       ---

       44. CBSE EXAM TIPS

       Remember these points carefully:

       List       → Mutable
       Tuple      → Immutable
       Dictionary → Key-Value pairs

       append() → Adds one item
       extend() → Adds multiple items
       insert() → Adds at a particular index
       remove() → Removes by value
       pop()    → Removes by index and returns item

       sort()   → Changes the list
       sorted() → Returns a new sorted list

       randint(a,b)  → b is included
       randrange(a,b) → b is excluded

       find() is associated with strings.
       index() is available for lists, tuples and strings.

       For dictionaries:

       d.keys()    → Keys
       d.values()  → Values
       d.items()   → Key-value pairs
       d.get()     → Safely access a value
       d.update()  → Add/modify items
       d.pop()     → Remove specified key
       d.popitem() → Remove last inserted pair
       d.clear()   → Remove all items

       For modules:

       import math
       math.sqrt(25)

       or:

       from math import sqrt
       sqrt(25)

       _______U3__________________RUonTop_____________U3__________

       Unit 3: Society, Law and Ethics

       Introduction

       Computers, the Internet and digital technologies have become an important part of modern society. We use technology for:

       • Education
       • Communication
       • Banking
       • Shopping
       • Entertainment
       • Healthcare
       • Government services
       • Business and employment

       Technology provides many benefits, but its improper use can create problems such as cyber crime, privacy violations, plagiarism, cyber bullying and electronic waste.

       Therefore, every computer user should understand digital responsibility, cyber safety, law and ethics.

       ---

       1. DIGITAL FOOTPRINTS

       1.1 What is a Digital Footprint?

       A digital footprint is the trail or record of information that a person leaves behind while using the Internet and digital devices.

       Whenever we use websites, social media, apps or online services, we may leave information behind.

       Examples

       A digital footprint may include:

       • Websites we visit
       • Online searches
       • Social media posts
       • Comments and likes
       • Photos and videos uploaded
       • Emails sent
       • Online purchases
       • Online registrations
       • Reviews posted on websites
       • Location information shared by apps
       • Online accounts created

       Example

       Suppose a student:

       1. Creates an Instagram account.
       2. Posts a photograph.
       3. Comments on a friend's post.
       4. Searches for a product.
       5. Buys the product online.

       These activities can create a digital footprint.

       ---

       1.2 Types of Digital Footprints

       Digital footprints are commonly divided into two types:

       A. Active Digital Footprint

       An active digital footprint is information that a user deliberately provides or shares online.

       Examples

       • Posting a photograph
       • Writing a comment
       • Sending an email
       • Filling an online form
       • Creating a social media post
       • Uploading a video

       B. Passive Digital Footprint

       A passive digital footprint is information collected about a user without the user actively posting it.

       Examples

       • Websites recording IP addresses
       • Cookies storing browsing information
       • Location information collected by an application
       • Websites recording visit statistics

       ---

       1.3 Why Digital Footprints Matter

       Digital footprints can affect:

       • Privacy
       • Reputation
       • Security
       • Education
       • Employment
       • Personal relationships

       Important Rule

       Think before you post.

       Information shared online can be copied, saved, forwarded or redistributed.

       ---

       1.4 How to Manage Your Digital Footprint

       1. Think carefully before posting.
       2. Avoid sharing unnecessary personal information.
       3. Use strong passwords.
       4. Review privacy settings.
       5. Delete unused accounts.
       6. Avoid suspicious websites.
       7. Do not accept unknown friend/follow requests blindly.
       8. Check information before sharing it.
       9. Avoid posting sensitive documents.
       10. Remember that deleting a post does not guarantee that all copies have disappeared.

       ---

       2. DIGITAL SOCIETY AND NETIZEN

       2.1 What is a Digital Society?

       A digital society is a society in which digital technologies are widely used for communication, education, business, government services and everyday activities.

       Examples

       • Online classes
       • Digital payments
       • Online banking
       • E-commerce
       • Video conferencing
       • Online government services
       • Social networking

       ---

       3. NETIZEN

       3.1 Meaning of Netizen

       The word Netizen is formed from:

       Internet + Citizen = Netizen

       A netizen is a person who actively uses the Internet and participates in the online community.

       A responsible netizen should:

       • Respect other users.
       • Follow laws.
       • Protect personal information.
       • Communicate politely.
       • Avoid spreading false information.
       • Respect intellectual property.
       • Report harmful or illegal activities.

       ---

       4. NET ETIQUETTES

       4.1 What is Netiquette?

       Netiquette means Internet etiquette.

       It refers to the rules and good manners that should be followed while communicating and behaving online.

       Important Netiquette Rules

       1. Be polite and respectful.
       2. Do not use offensive language.
       3. Do not intentionally hurt others.
       4. Do not type everything in CAPITAL LETTERS unnecessarily.
       5. Do not spread rumours.
       6. Respect other people's privacy.
       7. Do not share someone else's photograph without permission.
       8. Do not send spam.
       9. Give credit to original creators.
       10. Verify information before forwarding it.
       11. Do not participate in cyber bullying.
       12. Use appropriate language in online discussions.

       ---

       5. COMMUNICATION ETIQUETTES

       Communication etiquette means following appropriate manners while communicating using digital technologies.

       Examples include:

       • Email
       • Chat
       • Video calls
       • Online meetings
       • Discussion forums
       • Messaging applications

       Good Communication Practices

       1. Use a meaningful subject in an email

       Bad:

       Subject: Hi

       Better:

       Subject: Class 11 Computer Science Assignment

       2. Be clear and brief

       Write information in a clear manner.

       3. Avoid unnecessary messages

       Do not send repeated messages or spam.

       4. Respect others

       Do not use abusive or insulting language.

       5. Check before sending

       Check:

       • Recipient
       • Message
       • Attachments
       • Links

       before sending.

       6. Do not forward private messages

       Private communication should not be shared publicly without appropriate permission.

       ---

       6. SOCIAL MEDIA ETIQUETTES

       Social media etiquette means using social networking platforms responsibly.

       Important Rules

       1. Think before posting.
       2. Do not post private information publicly.
       3. Respect other people's opinions.
       4. Do not upload someone else's photograph without permission.
       5. Do not spread fake news.
       6. Do not post offensive content.
       7. Do not share passwords or OTPs.
       8. Avoid arguments and abusive comments.
       9. Report inappropriate or harmful content.
       10. Use privacy settings carefully.

       Remember

       POST → THINK → CHECK → SHARE

       ---

       7. DATA PROTECTION

       7.1 What is Data Protection?

       Data protection means protecting data from:

       • Unauthorised access
       • Unauthorised modification
       • Loss
       • Theft
       • Misuse
       • Unauthorised disclosure

       Examples of Sensitive Data

       • Passwords
       • Bank details
       • Credit/debit card information
       • Aadhaar-related information
       • Personal photographs
       • Medical records
       • Educational records
       • Personal identification information

       ---

       8. INTELLECTUAL PROPERTY RIGHTS (IPR)

       8.1 What is Intellectual Property?

       Intellectual Property (IP) refers to creations of the human mind, such as:

       • Inventions
       • Literary works
       • Software
       • Music
       • Artistic works
       • Designs
       • Brand names
       • Logos

       Intellectual Property Rights (IPR) are legal rights that protect such creations.

       ---

       9. COPYRIGHT

       9.1 Meaning of Copyright

       Copyright is a legal protection given to the creators of original works.

       It can apply to:

       • Books
       • Articles
       • Music
       • Films
       • Photographs
       • Videos
       • Computer programs
       • Artwork
       • Educational content

       Example

       If a person creates an original educational video, another person should not simply copy and publish it as their own work.

       ---

       10. PATENT

       10.1 Meaning of Patent

       A patent is a legal right granted for an invention that satisfies applicable legal requirements.

       It can protect inventions such as:

       • New machines
       • New technical processes
       • New products
       • Certain technological innovations

       Example

       A company develops a new technological device. It may seek patent protection for the invention if it meets the applicable requirements.

       ---

       11. TRADEMARK

       11.1 Meaning of Trademark

       A trademark is a sign that identifies and distinguishes the goods or services of one business from those of others.

       It may include:

       • Brand names
       • Logos
       • Symbols
       • Certain words or phrases

       Example

       A company's distinctive brand name or logo may be protected as a trademark.

       ---

       12. COPYRIGHT vs PATENT vs TRADEMARK

       Copyright	Patent	Trademark
       Protects original creative works	Protects qualifying inventions	Identifies/distinguishes goods or services
       Books, music, software, videos	Machines, processes, technical inventions	Brand names, logos, marks
       Concerned mainly with creative expression	Concerned with inventions	Concerned with commercial identity

       ---

       13. VIOLATION OF IPR

       Violation of Intellectual Property Rights means using protected intellectual property in a way that infringes the owner's legal rights.

       Important examples include:

       • Plagiarism
       • Copyright infringement
       • Trademark infringement

       ---

       14. PLAGIARISM

       Meaning

       Plagiarism means presenting someone else's work, ideas or words as your own without appropriate acknowledgement.

       Examples

       • Copying an assignment from the Internet.
       • Submitting another student's project as your own.
       • Copying an article without credit.
       • Using another person's ideas without acknowledgement.

       How to Avoid Plagiarism

       1. Write in your own words.
       2. Give credit to sources.
       3. Use quotation marks for direct quotations.
       4. Mention references where required.
       5. Do not submit copied work as your own.

       ---

       15. COPYRIGHT INFRINGEMENT

       Copyright infringement occurs when someone uses copyrighted material in a way that violates the copyright owner's rights.

       Examples

       • Copying and distributing a copyrighted book without permission.
       • Re-uploading copyrighted videos without appropriate rights.
       • Using copyrighted software illegally.
       • Copying copyrighted images and claiming them as your own.

       Important

       Not every use of copyrighted material is automatically infringement; applicable copyright law may provide exceptions or limitations in particular situations.

       ---

       16. TRADEMARK INFRINGEMENT

       Trademark infringement generally involves unauthorised use of a trademark in a way that may cause confusion or otherwise violates the rights associated with the mark.

       Example

       A business uses another company's brand name or logo in a misleading manner to make customers believe that the products or services are associated with the original company.

       ---

       17. OPEN SOURCE SOFTWARE

       17.1 Meaning

       Open source software is software whose source code is made available under a licence that permits users to use, inspect, modify and redistribute it, subject to the licence terms.

       Examples

       • Linux
       • Mozilla Firefox
       • LibreOffice
       • Python

       Important

       Open source does not simply mean "software that is free of cost."

       It refers primarily to the availability of source code and the rights granted by the applicable licence.

       ---

       18. SOFTWARE LICENSING

       A software licence is a legal agreement that specifies how software can be used, modified and distributed.

       Different licences provide different permissions and conditions.

       Examples:

       • Creative Commons licences
       • GNU General Public License (GPL)
       • Apache License

       ---

       19. CREATIVE COMMONS

       Creative Commons (CC) provides a set of standard licences that creators can use to specify how others may use their creative works.

       Different Creative Commons licences impose different conditions.

       Common conditions include:

       • BY – Attribution required
       • SA – ShareAlike
       • NC – NonCommercial
       • ND – NoDerivatives

       Important

       Always check the exact Creative Commons licence attached to a work before using it.

       ---

       20. GNU GENERAL PUBLIC LICENSE (GPL)

       The GNU General Public License (GPL) is a widely used free and open-source software licence.

       It allows users to use, study, modify and redistribute covered software subject to its licence conditions.

       A key feature of the GPL is its copyleft approach: under the applicable terms, modified/distributed versions must preserve the required freedoms and licensing conditions.

       ---

       21. APACHE LICENSE

       The Apache License is a permissive open-source software licence.

       It allows users to:

       • Use the software
       • Modify the software
       • Distribute the software
       • Use it in many types of projects

       subject to the licence conditions.

       The Apache License also contains provisions relating to copyright and patents.

       ---

       22. CYBER CRIME

       22.1 Definition

       Cyber crime refers to illegal activities involving computers, computer networks, digital devices or the Internet.

       Examples include:

       • Hacking
       • Phishing
       • Online fraud
       • Identity theft
       • Malware attacks
       • Ransomware
       • Cyber bullying

       ---

       23. HACKING

       Meaning

       Hacking generally refers to gaining access to a computer system, network or account by exploiting weaknesses or bypassing security controls.

       In the context of cyber crime, unauthorised hacking can be illegal.

       Example

       An attacker obtains another person's password and accesses their email account without permission.

       Protection

       • Use strong passwords.
       • Enable multi-factor authentication where available.
       • Keep software updated.
       • Do not share passwords.
       • Avoid suspicious links.

       ---

       24. EAVESDROPPING

       Meaning

       Eavesdropping means secretly listening to or monitoring private communications without proper authorisation.

       Example

       An attacker secretly intercepts network communication to obtain confidential information.

       Protection

       • Use secure networks.
       • Prefer encrypted websites and services.
       • Avoid sensitive transactions on untrusted networks.
       • Keep devices and software updated.

       ---

       25. PHISHING

       Meaning

       Phishing is a social-engineering technique in which an attacker attempts to trick a person into revealing sensitive information or performing an unsafe action.

       Phishing may happen through:

       • Email
       • SMS
       • Websites
       • Social media
       • Messaging applications
       • Phone calls

       Example

       A person receives an email:

       Your bank account will be blocked today. Click here to verify your account.

       The link leads to a fake website designed to steal login information.

       Warning Signs

       • Urgent language
       • Suspicious links
       • Unknown sender
       • Requests for passwords
       • Requests for OTPs
       • Unexpected attachments
       • Spelling or formatting mistakes

       ---

       26. FRAUD EMAILS

       Fraud emails are deceptive emails designed to:

       • Steal money
       • Obtain passwords
       • Collect personal information
       • Spread malware
       • Trick users into clicking malicious links

       Example

       An email claims:

       Congratulations! You have won ₹10,00,000. Pay ₹5,000 processing fee to receive your prize.

       This may be an online scam.

       Safety Rule

       Never send money or sensitive information simply because an email asks for it. Verify independently.

       ---

       27. RANSOMWARE

       Meaning

       Ransomware is malicious software that can block access to files or systems, often by encrypting files, and then demand payment from the victim.

       Typical Process

       Ransomware enters system ↓ Files are encrypted ↓ Victim cannot access files ↓ Attacker demands ransom

       Protection

       1. Maintain regular backups.
       2. Keep operating systems updated.
       3. Keep security software updated.
       4. Do not open suspicious attachments.
       5. Avoid suspicious links.
       6. Use strong security practices.

       Important

       Paying a ransom does not guarantee recovery of files.

       ---

       28. CYBER TROLLS

       A cyber troll is a person who deliberately posts provocative, insulting or disruptive content online to cause arguments or provoke reactions.

       Example

       Someone repeatedly posts offensive comments under online discussions just to create conflict.

       How to Deal with Trolling

       • Do not unnecessarily engage.
       • Block the user when appropriate.
       • Report abusive behaviour.
       • Keep evidence if serious harassment is involved.

       ---

       29. CYBER BULLYING

       Cyber bullying is the use of digital technologies to repeatedly harass, threaten, humiliate or intimidate another person.

       It can occur through:

       • Social media
       • Messaging apps
       • Online games
       • Email
       • Discussion forums

       Examples

       • Sending threatening messages
       • Spreading humiliating rumours
       • Sharing embarrassing content
       • Repeatedly posting abusive comments
       • Creating fake accounts to harass someone

       What to Do

       1. Do not retaliate.
       2. Save evidence.
       3. Block the offender.
       4. Report the account/content.
       5. Tell a trusted adult, teacher or appropriate authority.
       6. Seek help if there is a serious threat.

       ---

       30. CYBER SAFETY

       Cyber safety means using computers, smartphones, networks and the Internet in a secure and responsible manner.

       ---

       31. SAFELY BROWSING THE WEB

       Important Safety Practices

       1. Use trusted websites.
       2. Check the website address carefully.
       3. Look for HTTPS when entering sensitive information.
       4. Do not click suspicious links.
       5. Do not download files from unknown sources.
       6. Keep browsers updated.
       7. Avoid entering passwords on suspicious websites.
       8. Log out of accounts on shared computers.
       9. Avoid unnecessary browser extensions.
       10. Be careful with pop-ups and unexpected downloads.

       ---

       32. IDENTITY PROTECTION

       Meaning

       Identity protection means protecting personal information from unauthorised use.

       Information to Protect

       • Full name
       • Address
       • Phone number
       • Email address
       • Passwords
       • OTPs
       • Bank details
       • Government identification information
       • Personal photographs

       Safety Measures

       1. Use strong and unique passwords.
       2. Enable multi-factor authentication.
       3. Never share OTPs.
       4. Avoid sharing unnecessary personal information.
       5. Check privacy settings.
       6. Be careful with unknown callers and messages.
       7. Monitor suspicious account activity.

       ---

       33. CONFIDENTIALITY

       Confidentiality means ensuring that information is available only to authorised persons.

       Example

       A student's academic record should not be publicly accessible to everyone.

       Ways to Maintain Confidentiality

       • Password protection
       • Encryption
       • Access control
       • Secure networks
       • Multi-factor authentication
       • Proper permissions

       CIA Triad

       Information security is often explained using:

       C → Confidentiality I → Integrity A → Availability

       Confidentiality

       Only authorised people can access information.

       Integrity

       Information remains accurate and is not changed improperly.

       Availability

       Authorised users can access information when needed.

       ---

       34. MALWARE

       34.1 Meaning

       Malware stands for Malicious Software.

       It refers to software intentionally designed to perform harmful or unauthorised actions.

       Examples include:

       • Viruses
       • Trojans
       • Adware
       • Ransomware
       • Spyware
       • Worms

       This syllabus specifically includes:

       • Virus
       • Trojan
       • Adware

       ---

       35. COMPUTER VIRUS

       A computer virus is malicious code that can attach itself to legitimate files or programs and replicate when the infected host is executed or otherwise activated.

       Possible Effects

       • Corrupt files
       • Delete data
       • Slow down the system
       • Modify programs
       • Cause unexpected behaviour

       Protection

       • Use reputable security software.
       • Keep software updated.
       • Avoid unknown files.
       • Scan external storage devices.
       • Do not run suspicious programs.

       ---

       36. TROJAN

       A Trojan or Trojan horse is malware that disguises itself as legitimate or useful software to trick a user into installing or running it.

       Example

       A user downloads a program advertised as a useful utility, but the program secretly performs malicious activities.

       Protection

       • Download software from trusted sources.
       • Avoid pirated/cracked software.
       • Check the publisher.
       • Keep security software updated.

       ---

       37. ADWARE

       Adware is software that displays unwanted advertisements.

       Some adware may also collect information or modify browser behaviour, depending on the program.

       Common Signs

       • Excessive pop-up advertisements
       • Unexpected browser redirects
       • Unwanted extensions
       • Changes to browser settings

       Protection

       • Install software from trusted sources.
       • Avoid suspicious downloads.
       • Review browser extensions.
       • Use security software.

       ---

       38. VIRUS vs TROJAN vs ADWARE

       Virus	Trojan	Adware
       Can replicate by infecting files/programs	Disguises itself as legitimate software	Displays advertisements
       Can damage or modify files	Tricks users into installing/running it	May cause unwanted pop-ups
       Usually spreads through infected files/programs	Often relies on social engineering	Often comes bundled with software

       ---

       39. E-WASTE MANAGEMENT

       39.1 What is E-Waste?

       E-waste means discarded electrical and electronic equipment and components.

       Examples:

       • Old computers
       • Keyboards
       • Monitors
       • Printers
       • Mobile phones
       • Chargers
       • Batteries
       • Television sets
       • Circuit boards
       • Electronic accessories

       ---

       40. Problems Caused by E-Waste

       Improper disposal of electronic waste can:

       • Pollute soil
       • Pollute water
       • Release hazardous substances
       • Harm human health
       • Harm animals and ecosystems
       • Waste valuable recyclable materials

       ---

       41. Proper Disposal of Electronic Gadgets

       Follow the 4R approach where applicable:

       Reduce Reuse Repair Recycle

       Good Practices

       1. Repair devices when practical.
       2. Reuse working equipment.
       3. Donate usable devices where appropriate.
       4. Recycle through authorised e-waste collection/recycling channels.
       5. Do not throw electronic waste into ordinary household waste.
       6. Handle batteries carefully.
       7. Erase personal data before giving away or recycling a device.

       Important

       Electronic devices may contain valuable materials as well as substances requiring controlled handling. Therefore, e-waste should be managed through appropriate collection and recycling systems.

       ---

       42. INFORMATION TECHNOLOGY ACT (IT ACT)

       42.1 Introduction

       The Information Technology Act, 2000 is an important Indian law concerning electronic records, electronic communication and various aspects of cyber activities.

       It provides a legal framework for areas including:

       • Electronic records
       • Electronic transactions
       • Digital/electronic signatures
       • Certain cyber offences
       • Penalties and legal procedures relating to specified activities

       The Act has also been amended over time.

       ---

       43. Importance of the IT Act

       The IT Act provides legal recognition and a legal framework for electronic activities.

       It helps address issues related to:

       • Electronic records
       • Electronic authentication
       • Cyber offences
       • Unauthorised access
       • Damage to computer resources
       • Certain forms of online misuse

       Important

       Students should understand that cyber activities are subject to laws, and misuse of computers or the Internet can have legal consequences.

       ---

       44. TECHNOLOGY AND SOCIETY

       Technology has changed the way people:

       • Learn
       • Work
       • Communicate
       • Travel
       • Shop
       • Access government services
       • Obtain information

       However, technology should be designed and used in a way that promotes equality, accessibility and inclusion.

       Two important issues in the syllabus are:

       1. Gender issues
       2. Disability issues

       ---

       45. GENDER ISSUES IN TECHNOLOGY

       Meaning

       Gender issues refer to unequal opportunities, access, participation or treatment based on gender in the use and development of technology.

       Examples

       • Unequal access to computers or Internet facilities
       • Stereotypes about who should study technology
       • Unequal participation in technology-related education or careers
       • Online harassment based on gender
       • Lack of representation in some technology-related fields

       ---

       46. Addressing Gender Issues

       Schools and organisations can help by:

       1. Providing equal opportunities.
       2. Encouraging all students to learn computer science.
       3. Avoiding gender stereotypes.
       4. Providing equal access to digital devices.
       5. Promoting safe online environments.
       6. Encouraging participation in technology activities.
       7. Supporting students according to their interests and abilities.

       Important Principle

       Technology education should be accessible to everyone regardless of gender.

       ---

       47. DISABILITY ISSUES IN TECHNOLOGY

       People with disabilities may face difficulties when accessing computers, websites or digital services.

       Examples

       A person may have:

       • Visual impairment
       • Hearing impairment
       • Physical/motor limitations
       • Learning difficulties
       • Speech-related disabilities

       Technology should be designed to reduce unnecessary barriers.

       ---

       48. ASSISTIVE TECHNOLOGY

       Assistive technology refers to devices or software that help people with disabilities use technology and perform tasks more independently.

       Examples

       Disability/Need	Possible Assistive Technology
       Visual impairment	Screen reader
       Low vision	Screen magnification
       Hearing impairment	Captions/subtitles
       Motor difficulties	Alternative input devices
       Speech difficulties	Speech-generating systems
       Reading difficulties	Text-to-speech tools

       ---

       49. ACCESSIBILITY IN COMPUTER EDUCATION

       Teachers should try to make computer education accessible to all students.

       Good Practices

       1. Provide accessible learning materials.
       2. Use captions for videos.
       3. Use readable fonts and suitable contrast.
       4. Provide alternative text for meaningful images.
       5. Allow assistive technologies.
       6. Give sufficient time when appropriate.
       7. Provide alternative methods of interaction.
       8. Encourage inclusive classroom participation.

       ---

       50. DIGITAL DIVIDE

       The digital divide is the gap between people who have adequate access to digital technology and those who do not.

       Factors can include:

       • Income
       • Location
       • Internet availability
       • Digital literacy
       • Disability
       • Availability of devices

       Example

       If one group of students has high-speed Internet and personal computers while another group has no reliable device or Internet access, there is a digital access gap.

       ---

       51. RESPONSIBLE DIGITAL CITIZEN

       A responsible digital citizen:

       RESPONSIBLE DIGITAL CITIZEN | ┌──────────────┼──────────────┐ ↓ ↓ ↓ Privacy Respect Safety ↓ ↓ ↓ Security Ethics Laws ↓ ↓ ↓ IPR Netiquette Responsibility

       Main Responsibilities

       • Respect privacy.
       • Follow cyber laws.
       • Respect intellectual property.
       • Communicate politely.
       • Protect accounts.
       • Avoid cyber bullying.
       • Verify information.
       • Report harmful activities.
       • Dispose of electronic waste properly.

       ---

       52. IMPORTANT DIFFERENCES

       Active vs Passive Digital Footprint

       Active	Passive
       Deliberately created/shared by user	Collected through online activity
       Posts and comments	Cookies and visit records
       Emails	Some usage/technical data

       ---

       Copyright vs Plagiarism

       Copyright	Plagiarism
       Legal protection for original works	Presenting another's work as your own
       Concerned with legal rights	Concerned with academic/ethical attribution and may also involve legal issues
       Example: unauthorised copying of protected content	Submitting copied assignment without acknowledgement

       ---

       Phishing vs Hacking

       Phishing	Hacking
       Usually involves deception/social engineering	Often involves exploiting weaknesses or bypassing controls
       Attempts to trick users into revealing information or taking unsafe actions	May involve unauthorised access
       Often uses fake emails/websites/messages	May target systems, accounts or networks

       ---

       Virus vs Trojan

       Virus	Trojan
       Can infect/replicate through host files or programs	Disguises itself as legitimate software
       Replication is a characteristic feature	Does not need to replicate like a virus
       Often spreads through infected files/programs	Often relies on tricking users into executing it

       ---

       53. QUICK REVISION

       Digital Footprints

       Digital Footprint = Record/trail of online activities

       Netizen

       Netizen = Internet + Citizen

       Netiquette

       Netiquette = Good manners and responsible behaviour online

       IPR

       IPR = Intellectual Property Rights

       Main IPR Terms

       Copyright → Creative works Patent → Qualifying inventions Trademark → Brand identity/marks

       Cyber Crime

       Hacking Eavesdropping Phishing Fraud emails Ransomware Cyber trolling Cyber bullying

       Malware

       Virus Trojan Adware

       Cyber Safety

       Safe browsing Identity protection Confidentiality

       E-Waste

       Old/discarded electronic equipment

       Technology and Society

       Gender equality Accessibility Inclusion Digital divide Assistive technology

       ---

       54. IMPORTANT EXAM QUESTIONS

       Very Short Answer Questions

       1. What is a digital footprint?
       2. What is an active digital footprint?
       3. What is a passive digital footprint?
       4. What is a digital society?
       5. Who is a netizen?
       6. What is netiquette?
       7. Write any four rules of netiquette.
       8. What is data protection?
       9. What is Intellectual Property?
       10. What is IPR?
       11. Define copyright.
       12. What is a patent?
       13. What is a trademark?
       14. What is plagiarism?
       15. What is copyright infringement?
       16. What is trademark infringement?
       17. What is open source software?
       18. What is a software licence?
       19. What is Creative Commons?
       20. What is GPL?
       21. What is Apache License?
       22. Define cyber crime.
       23. What is hacking?
       24. What is eavesdropping?
       25. What is phishing?
       26. What is ransomware?
       27. What is cyber bullying?
       28. What is malware?
       29. What is a computer virus?
       30. What is a Trojan?
       31. What is adware?
       32. What is e-waste?
       33. What is cyber safety?
       34. What is confidentiality?
       35. What is identity protection?
       36. What is the Information Technology Act, 2000?
       37. What is assistive technology?
       38. What is the digital divide?

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       55. SHORT ANSWER QUESTIONS

       Q1. Differentiate between active and passive digital footprints.

       Answer:

       An active digital footprint is deliberately created by a user, such as posting a photograph or writing a comment.

       A passive digital footprint is information collected through online activities without the user deliberately posting it, such as certain website visit records or cookies.

       ---

       Q2. Write four rules of social media etiquette.

       Answer:

       1. Think before posting.
       2. Respect other users.
       3. Do not spread false information.
       4. Do not share private information unnecessarily.

       ---

       Q3. Differentiate between copyright, patent and trademark.

       Answer:

       • Copyright protects original creative works.
       • Patent protects qualifying inventions.
       • Trademark identifies and distinguishes goods or services.

       ---

       Q4. What is plagiarism? How can it be avoided?

       Answer:

       Plagiarism is presenting another person's work or ideas as one's own without proper acknowledgement.

       It can be avoided by:

       • Writing in one's own words.
       • Giving credit to sources.
       • Using quotations appropriately.
       • Providing references where required.

       ---

       Q5. What is phishing?

       Answer:

       Phishing is a social-engineering technique in which an attacker attempts to trick a user into revealing sensitive information or performing an unsafe action, often through fake emails, messages or websites.

       ---

       Q6. Write four precautions against phishing.

       Answer:

       1. Do not click suspicious links.
       2. Check the sender carefully.
       3. Never share passwords or OTPs through unsolicited messages.
       4. Verify requests through an independent trusted channel.

       ---

       Q7. What is ransomware?

       Answer:

       Ransomware is malware that can deny access to files or systems, commonly by encrypting files, and then demand payment from the victim.

       ---

       Q8. What is e-waste? How should it be disposed of?

       Answer:

       E-waste is discarded electrical and electronic equipment.

       It should be:

       • Reused where possible.
       • Repaired where practical.
       • Donated if usable.
       • Sent to appropriate authorised collection/recycling channels.

       ---

       Q9. What is assistive technology?

       Answer:

       Assistive technology consists of devices or software that help people with disabilities use computers and digital services more effectively.

       Examples include screen readers, screen magnifiers and captions.

       ---

       56. LONG ANSWER QUESTIONS

       Q1. Explain digital footprints and their types.

       Include:

       • Definition
       • Active digital footprint
       • Passive digital footprint
       • Examples
       • Importance
       • Methods of managing digital footprints

       ---

       Q2. Explain Intellectual Property Rights.

       Include:

       • Meaning of intellectual property
       • Copyright
       • Patent
       • Trademark
       • Plagiarism
       • Copyright infringement
       • Trademark infringement

       ---

       Q3. Explain different types of cyber crime.

       Discuss:

       • Hacking
       • Eavesdropping
       • Phishing
       • Fraud emails
       • Ransomware
       • Cyber trolling
       • Cyber bullying

       ---

       Q4. Explain cyber safety measures.

       Include:

       • Safe web browsing
       • Strong passwords
       • Multi-factor authentication
       • Identity protection
       • Confidentiality
       • Avoiding suspicious links and attachments
       • Software updates
       • Backups

       ---

       Q5. Explain malware and its types.

       Explain:

       1. Virus
       2. Trojan
       3. Adware

       Also include their effects and prevention methods.

       ---

       Q6. Explain gender and disability issues in technology.

       Include:

       • Equal access
       • Avoiding gender stereotypes
       • Online safety
       • Accessibility
       • Assistive technology
       • Inclusive teaching
       • Digital divide

       ---

       57. IMPORTANT KEYWORDS FOR CBSE EXAM

       Keyword	Meaning
       Digital Footprint	Trail/record of online activity
       Netizen	Internet user participating in digital society
       Netiquette	Good online manners
       IPR	Intellectual Property Rights
       Copyright	Protection for original creative works
       Patent	Protection for qualifying inventions
       Trademark	Identifying/distinguishing mark
       Plagiarism	Presenting another's work as one's own
       Phishing	Deceptive attempt to obtain information
       Hacking	Unauthorised access/exploitation of systems
       Eavesdropping	Unauthorised monitoring of communication
       Ransomware	Malware that denies access and demands ransom
       Malware	Malicious software
       Virus	Malware that can infect/replicate through host files or programs
       Trojan	Malware disguised as legitimate software
       Adware	Software that displays unwanted advertisements
       E-Waste	Discarded electronic equipment
       Confidentiality	Preventing unauthorised access to information
       Accessibility	Making technology usable by people with different needs
       Assistive Technology	Technology supporting people with disabilities

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       58. ONE-PAGE REVISION MAP

       UNIT 3 SOCIETY, LAW AND ETHICS | ┌─────────────────┼─────────────────┐ ↓ ↓ ↓ DIGITAL SOCIETY DATA CYBER | PROTECTION SAFETY | | | Digital Footprint IPR Safe Browsing Netizen Copyright Identity Netiquette Patent Confidentiality Communication Trademark Social Media Open Source Licensing | ↓ CYBER CRIME | ┌───────────────┼────────────────┐ ↓ ↓ ↓ Hacking Phishing Ransomware Eavesdropping Fraud Emails Cyber Bullying Cyber Trolls | ↓ MALWARE | ┌─────────┼─────────┐ ↓ ↓ ↓ Virus Trojan Adware | ↓ E-WASTE | Reduce / Reuse Repair / Recycle | ↓ IT ACT, 2000 | ↓ TECHNOLOGY & SOCIETY | ┌─────────┴─────────┐ ↓ ↓ Gender Issues Disability Issues | Assistive Technology Accessibility Inclusion

       59. FINAL EXAM REMEMBER POINTS

       1. Digital footprint is the trail of information left through digital activities.
       2. Netizen means a citizen/user of the Internet.
       3. Netiquette means good manners and responsible behaviour online.
       4. Copyright protects original creative works.
       5. Patent protects qualifying inventions.
       6. Trademark identifies and distinguishes goods or services.
       7. Plagiarism means presenting someone else's work or ideas as one's own without proper acknowledgement.
       8. Phishing uses deception to obtain information or cause unsafe actions.
       9. Ransomware commonly encrypts files and demands payment.
       10. Cyber bullying involves harassment or intimidation through digital technologies.
       11. Malware means malicious software.
       12. Virus, Trojan and adware are examples of malware.
       13. Confidentiality protects information from unauthorised access.
       14. E-waste should be handled through proper reuse, collection and recycling channels.
       15. The Information Technology Act, 2000 is an important Indian law concerning electronic records, electronic transactions and specified cyber activities.
       16. Technology should promote equality, accessibility and inclusion.
       17. Assistive technology helps people with disabilities use digital technologies.
       18. Every user should behave as a responsible digital citizen.

       Golden Rule of Digital Citizenship

       Use technology safely, legally, ethically and respectfully.