Computer Science , CLASS 11 comprehensive notes.

CLASS11(CS).md

Unit 1: Computer Systems and Organisation Overview

Basic Computer Organisation

Computer systems consist of several core components that enable them to function and perform tasks. These components include:

• Hardware: The physical parts of a computer such as the CPU, memory units, and I/O devices.
• Software: Programs and operating systems that run on hardware, directing its operations.
• Input Devices: Tools used to input data into a computer (e.g., keyboard, mouse).
• Output Devices: Devices that output data from a computer (e.g., monitors, printers).
• CPU (Central Processing Unit): Acts as the brain of the computer, processing instructions.
• Memory: Includes primary storage (RAM, cache) and secondary storage (hard drives, SSDs).

Units of Memory

Memory units are categorized from the smallest to the largest as follows:

• Bit
• Byte
• Kilobyte (KB)
• Megabyte (MB)
• Gigabyte (GB)
• Terabyte (TB)
• Petabyte (PB)

These units help quantify data storage capacity in computing.

Types of Software

Software can be broadly classified into:

• System Software: Includes operating systems, system utilities, and device drivers that help manage the computer's hardware and basic system operations.
• Programming Tools and Language Translators: Tools like assemblers, compilers, and interpreters that convert programming code into machine language that computers can understand.
• Application Software: Programs that perform specific tasks for users, such as word processors or web browsers.

Operating System (OS)

The OS is crucial system software that manages computer hardware and software resources. It provides common services for computer programs and enables user interaction through a user interface. Key functions include:

• Booting the computer
• Managing system resources
• Executing and providing services for application software.

Boolean Logic and Logic Circuits

Boolean logic is fundamental to computer science, involving basic operators like NOT, AND, OR, NAND, NOR, and XOR. These operators are used to create truth tables and logic circuits, which are essential for digital computing and circuit design. De Morgan’s Laws are also a critical part of Boolean logic, providing rules for converting expressions into alternative forms.

Number Systems

Computers use different number systems to handle data:

• Binary: Base-2, used internally by computers.
• Octal: Base-8, occasionally used in computing.
• Decimal: Base-10, used universally in human interactions.
• Hexadecimal: Base-16, commonly used in programming and debugging.

Conversion between these systems is a common task in computer science and programming.

Encoding Schemes

Encoding schemes like ASCII, ISCII, and Unicode (UTF-8, UTF-32) are used to represent characters in computers. Unicode is particularly important for supporting a wide array of characters and symbols globally.

This overview encapsulates the foundational elements of computer systems and organization, highlighting the integral components and functions that make up modern computing environments.

Unit 2: Computational Thinking and Programming - I Overview

Introduction to Problem-solving

Problem-solving in programming involves several systematic steps:

1. Analyzing the Problem: Understanding the problem's requirements and constraints.
2. Developing an Algorithm: Creating a step-by-step solution to the problem.
3. Coding: Translating the algorithm into a programming language.
4. Testing: Running the code to find any errors or bugs.
5. Debugging: Fixing the errors identified during testing.

Algorithms can be represented using flowcharts and pseudocode, which help in visualizing and planning the solution before actual coding.

Familiarization with Python Programming

Python is a versatile and widely-used programming language known for its readability and straightforward syntax. Key aspects include:

• Execution Modes: Python can run in interactive mode or script mode.
• Python Tokens: Includes keywords, identifiers, literals, operators, and punctuators.
• Variables and Comments: Understanding the use of variables and the importance of comments for code readability.
• L-value and R-value: Concepts that refer to the memory location and data value of variables, respectively.

A simple "Hello World" program in Python can be executed as follows:

print("Hello, World!")

Data Types and Operators

Python supports various data types and operators:

• Data Types: Includes integers, floating points, complex numbers, booleans, strings, lists, tuples, dictionaries, and the special value None.
• Operators: Python provides a rich set of operators such as arithmetic, relational, logical, assignment, augmented assignment, identity, and membership operators.

Control Flow

Understanding the flow of control in Python involves:

• Conditional Statements: if, if-else, and if-elif-else structures allow for branching based on conditions.
• Iterative Statements: for loops and while loops enable executing a block of code multiple times. Useful for iterating over data structures or performing repetitive tasks.

Strings and Collections

• Strings: Operations include concatenation, repetition, membership testing, slicing, and various built-in methods like len(), find(), replace(), and more.
• Lists: Support indexing, slicing, and methods like append(), extend(), pop(), etc.
• Tuples: Immutable sequences that support similar operations to lists but cannot be changed after creation.
• Dictionaries: Key-value pairs that are mutable and can be dynamically altered. Methods include keys(), values(), items(), get(), update(), etc.

Python Modules

Modules enhance Python's functionality. They can be imported using import statements. Common modules include:

• Math Module: Provides access to mathematical functions like sqrt(), ceil(), floor(), etc.
• Random Module: Includes functions for generating random numbers.
• Statistics Module: Offers statistical functions like mean(), median(), and mode().

This unit provides a comprehensive introduction to computational thinking and basic programming in Python, equipping learners with the necessary tools and concepts to start solving problems using Python.

Unit 3: Society, Law, and Ethics

Digital Footprints

A digital footprint is the record or trail left by the activities one engages in online. This includes social media activity, browsing history, and any data uploaded such as photos or videos. It's important to be aware of what you share online because once information is on the internet, it can be accessed globally and may be difficult to erase.

Digital Society and Netizen

In the digital age, being a responsible netizen (a citizen of the internet) involves adhering to netiquettes (internet etiquettes). This includes being polite, respecting others' privacy, and engaging in ethical online interactions. Social media etiquettes are particularly important as they guide behavior in platforms where rapid and wide dissemination of information can occur.

Data Protection

Intellectual Property Rights (IPR) protect creators' legal rights to their inventions, literary and artistic works, symbols, names, and images used in commerce. Violations of IPR include:

• Plagiarism: Using someone else's work without proper attribution.
• Copyright Infringement: Using copyrighted work without permission.
• Trademark Infringement: Unauthorized use of a trademark which can confuse consumers about the true source of products or services.

Open source software and licensing frameworks like Creative Commons, GPL, and Apache license provide mechanisms through which software can be freely used, modified, and shared.

Cyber Crime

Cyber crimes are illegal activities conducted online. They include:

• Hacking: Unauthorized access to computer systems.
• Eavesdropping: Intercepting private communications.
• Phishing and Fraud Emails: Deceiving recipients into providing sensitive information.
• Ransomware: Malware that encrypts the victim's data and demands ransom for the decryption key.
• Cyber Bullying and Trolling: Using the internet to harass or intimidate others.

Cyber Safety

To safely browse the web, it's crucial to:

• Protect your identity.
• Ensure confidentiality of your data.
• Be cautious of the websites you visit and the information you share online.

Malware

Malware includes various forms of harmful software such as:

• Viruses: Software that replicates itself and spreads to other computers.
• Trojans: Disguises itself as legitimate software to trick users into loading and executing the malware on their system.
• Adware: Automatically delivers advertisements to generate revenue for its author.

E-waste Management

Proper disposal of electronic gadgets is essential to prevent harmful substances contained in e-waste from damaging the environment and human health. Recycling and responsible e-waste management practices are crucial.

Information Technology Act (IT Act)

The IT Act in India provides the legal framework for electronic governance by recognizing electronic records and digital signatures. It aims to ensure the security of online transactions and penalizes cyber crimes.

Technology and Society

Issues of gender and disability accessibility in technology usage highlight the need for inclusive designs that accommodate all users, ensuring that technology benefits everyone without discrimination.

This unit covers the intersection of technology with societal norms, legal frameworks, and ethical considerations, emphasizing the importance of responsible and informed digital citizenship.