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

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).

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.

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.

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.

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.

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.

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.

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.

Summary Example:

When you browse the web:

Input: You use the mouse and keyboard to type a website URL.
CPU: The CPU processes the URL and retrieves the website's data from storage.
Primary Memory: The website is loaded into RAM for quick access.
Cache: Frequently used data from the website may be stored in cache memory for faster future access.
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.

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:

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).
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.
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.

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:

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.
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.
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.

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:

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.
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.
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.
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.
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.

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

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:

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.

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.

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.

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.

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.

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.

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.

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

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.
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.
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.

Examples of Operating Systems with Different UIs

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.
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.
Linux (Ubuntu):
- A GUI-based OS that also provides a CLI option for more advanced users. The GNOME desktop environment is widely used.
Android:
- A touch-based UI designed for smartphones and tablets. Users interact with touch gestures and access apps through a home screen.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.
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.

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

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.

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.

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.

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.

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.

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.

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

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

So, 13 in decimal is 1101 in binary.

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.

255 ÷ 16 = 15 remainder 15 → F
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.

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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.

Introduction to Problem-Solving

Problem-solving is the process of identifying a solution to a given issue. In programming, it involves breaking down complex tasks into manageable steps and transforming these steps into code.

Steps for Problem-Solving:

Analyzing the Problem:
- Understand the problem clearly by reading the description and identifying inputs and outputs. Break it into smaller subproblems if needed.
- Example: In a problem to find the sum of two numbers, the analysis shows that you need two numbers as input and the result as their sum.
Developing an Algorithm:
- An algorithm is a step-by-step solution to the problem. It should be simple, efficient, and clear.
- Example:
  Algorithm to find the sum of two numbers:
  - Step 1: Take two numbers as input.
  - Step 2: Add the two numbers.
  - Step 3: Display the result.
Coding:
- Convert the algorithm into a programming language. In Python, this might involve writing code that follows the logic you developed in the algorithm.
- Example:

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Unit 3: Society, Law and Ethics

● Digital Footprints

● Digital Society and Netizen: net etiquettes, communication etiquettes, social media etiquettes

● Data Protection: Intellectual property rights (copyright, patent, trademark), violation of IPR (plagiarism, copyright infringement, trademark infringement), open source software and licensing (Creative Commons, GPL and Apache)