CBSE Class 12 CS Notes

Cheatsheet Content

1. Python Fundamentals Tokens Keywords: Reserved words in Python that have special meaning and cannot be used as identifiers. Examples: if , else , while , for , def , import . Identifiers: Names given to variables, functions, classes, modules, or other objects. They must start with a letter or an underscore, followed by letters, numbers, or underscores. They are case-sensitive. Literals: Raw data values given in a variable or constant. Numeric Literals: Integers (e.g., 10 ), Floating-point numbers (e.g., 3.14 ), Complex numbers (e.g., 3 + 4j ). String Literals: Sequence of characters enclosed in single, double, or triple quotes (e.g., 'hello' , "Python" ). Boolean Literals: True and False . Special Literal: None (represents the absence of a value). Operators: Special symbols or keywords that perform operations on one or more operands. Arithmetic: + , - , * , / , % (modulo), ** (exponentiation), // (floor division). Relational (Comparison): == , != , > , < , >= , <= . Evaluate to True or False . Logical: and , or , not . Used to combine conditional statements. Assignment: = , += , -= , *= , etc. Used to assign values to variables. Bitwise: & , | , ^ , ~ , << , >> . Operate on bits. Identity: is , is not . Check if two variables refer to the same object in memory. Membership: in , not in . Check if a value is present in a sequence. Punctuators: Symbols used in programming to organize sentence structure, indicating the beginning and end of statements, blocks, or lists. Examples: () , [] , {} , , , : , . . Data Types int (Integer): Whole numbers, positive or negative, without decimals. E.g., -5 , 0 , 100 . float (Floating-point): Real numbers with a decimal point. E.g., 3.14 , -0.001 . complex (Complex Number): Numbers with a real and an imaginary part. E.g., 3 + 4j . bool (Boolean): Represents truth values: True or False . str (String): An ordered sequence of characters, enclosed in quotes. Immutable. E.g., "hello" . list: An ordered, mutable sequence of items. Items can be of different data types. Enclosed in square brackets. E.g., [1, 'a', 3.14] . tuple: An ordered, immutable sequence of items. Items can be of different data types. Enclosed in parentheses. E.g., (1, 'a', 3.14) . set: An unordered collection of unique items. Mutable. Enclosed in curly braces. E.g., {1, 2, 3} . dict (Dictionary): An unordered collection of key-value pairs. Keys must be unique and immutable. Mutable. Enclosed in curly braces. E.g., {'name': 'Alice', 'age': 30} . None: A special data type that represents the absence of a value or a null value. Control Flow Conditional Statements (if-elif-else): Allow the program to execute different blocks of code based on whether specified conditions are true or false. if : Executes a block of code if its condition is true. elif (else if): Checks an additional condition if the preceding if or elif conditions were false. else : Executes a block of code if all preceding if and elif conditions were false. Looping Statements (for, while): Allow a block of code to be executed repeatedly. for loop: Iterates over the items of any sequence (such as a list, tuple, string, or range) or other iterable objects, executing the loop body for each item. while loop: Executes a block of code repeatedly as long as a given condition remains true. The loop terminates when the condition becomes false. Jump Statements: Used to alter the flow of a loop or function. break: Terminates the current loop ( for or while ) and transfers execution to the statement immediately following the loop. continue: Skips the rest of the current iteration of the loop and immediately proceeds to the next iteration. pass: A null operation; nothing happens when it executes. It is used as a placeholder where a statement is syntactically required but you don't want any code to execute. Functions Function: A named block of reusable code designed to perform a specific task. Functions promote modularity and code reuse. Built-in Functions: Functions that are pre-defined in Python and are always available for use without needing to import any module. Examples: print() , input() , len() , type() , sum() . Module Functions: Functions that are part of a specific module and need to be imported before they can be used. Examples: math.sqrt() , random.randint() . User-defined Functions: Functions created by the programmer to perform specific tasks. Defined using the def keyword. Arguments: Values passed to a function when it is called. Positional Arguments: Arguments passed to a function in the correct positional order. Keyword Arguments: Arguments passed to a function identified by their parameter name, allowing them to be passed in any order. Default Arguments: Parameters that have a default value assigned in the function definition. If no argument is provided for them during the call, their default value is used. Variable-length Arguments ( *args , **kwargs ): Allow a function to accept an arbitrary number of arguments. *args collects positional arguments into a tuple, and **kwargs collects keyword arguments into a dictionary. Scope (LEGB Rule): The region of a program where a variable is accessible. Python follows the LEGB rule for resolving names: Local: Names defined inside a function. Enclosing function locals: Names in the local scope of any enclosing functions (for nested functions). Global: Names defined at the top level of a module or explicitly declared global . Built-in: Names pre-defined in Python (e.g., print , len ). Recursion: A programming technique where a function calls itself directly or indirectly to solve a problem. It involves a base case to stop the recursion and a recursive step to call itself with a smaller subproblem. Module: A file containing Python definitions and statements. It allows for logical organization of code and promotes reusability. Modules can be imported into other Python programs. 2. File Handling File Types Text Files: Files that store data as a sequence of characters, typically readable by humans using a text editor. Each line usually ends with a newline character. Binary Files: Files that store data in a format identical to how it's stored in memory, rather than as readable text. They are not directly human-readable and often contain non-textual data like images, audio, or compiled programs. File Operations File Object: An object returned by the open() function, which provides methods for reading from or writing to a file. File Modes: Specify the purpose for which a file is opened. 'r' (read): Opens a file for reading. Error if the file does not exist. 'w' (write): Opens a file for writing. Creates the file if it does not exist, or truncates (empties) the file if it does exist. 'a' (append): Opens a file for appending. Creates the file if it does not exist. Data written is added to the end of the file. 'x' (exclusive creation): Creates a new file and opens it for writing. Fails if the file already exists. 'b' (binary mode): Used with other modes (e.g., 'rb' , 'wb' ) to open files in binary format. 't' (text mode): Default mode, opens files in text format. '+' (update mode): Used with other modes (e.g., 'r+' , 'w+' ) to open a file for both reading and writing. open() : A built-in function used to open a file and return a file object. close() : A method of file objects used to close an opened file, flushing any unwritten data and releasing system resources. Essential to call after file operations. with statement (Context Manager): A construct that ensures resources (like files) are properly managed. When used with open() , it automatically closes the file, even if errors occur. Syntax: with open("filename", "mode") as file_object: read() : Reads the entire content of a file as a single string (or bytes in binary mode). readline() : Reads a single line from a file. It includes the newline character at the end of the line. readlines() : Reads all lines from a file and returns them as a list of strings, where each string is a line from the file (including newline characters). write(string) : Writes a given string (or bytes in binary mode) to the file. It does not automatically add a newline character. writelines(list_of_strings) : Writes a list of strings to the file. Each string in the list is written sequentially, but no newline characters are added between them by default. CSV Files CSV (Comma Separated Values): A plain text file format used to store tabular data (numbers and text) in which each line represents a data record, and fields within a record are separated by commas. csv module: A built-in Python module that provides functionality to work with CSV files, simplifying the reading and writing of structured data. csv.reader() : An object that iterates over lines in the specified CSV file, parsing each line and returning it as a list of strings. csv.writer() : An object used to write data to a CSV file. writerow() : A method of a csv.writer object that writes a single row (a list of values) to the CSV file. writerows() : A method of a csv.writer object that writes multiple rows (a list of lists of values) to the CSV file. Binary Files (Pickling) pickle module: A Python module that implements binary protocols for serializing and de-serializing a Python object structure. Serialization (Pickling): The process of converting a Python object (like a list, dictionary, or custom object) into a byte stream. This byte stream can then be stored in a file or transmitted over a network. Deserialization (Unpickling): The reverse process of converting a byte stream (created by pickling) back into a Python object. pickle.dump(obj, file) : Writes the pickled representation of the object obj to the open file object file . pickle.load(file) : Reads the pickled representation from the open file object file and reconstructs the original Python object. 3. Data Structures Lists List: An ordered, mutable (changeable) sequence of items. Lists can contain items of different data types and allow duplicate elements. Defined using square brackets [] . Indexing: Accessing individual elements of a list using their position (index), starting from 0 for the first element. Negative indices count from the end of the list. Slicing: Extracting a subsequence (a "slice") from a list using a start, end, and step index. Syntax: list[start:end:step] . Concatenation: Combining two or more lists into a single new list using the + operator. Repetition: Creating a new list by repeating an existing list a specified number of times using the * operator. append() : Adds a single element to the end of a list. extend() : Appends all elements from an iterable (like another list) to the end of the current list. insert(index, element) : Inserts an element at a specified position in the list. remove(element) : Removes the first occurrence of a specified element from the list. Raises a ValueError if the element is not found. pop([index]) : Removes and returns the element at a given index. If no index is specified, it removes and returns the last element. clear() : Removes all elements from the list, making it empty. index(element) : Returns the index of the first occurrence of a specified element in the list. count(element) : Returns the number of times a specified element appears in the list. sort() : Sorts the items of the list in place (modifies the original list). Can sort in ascending or descending order. reverse() : Reverses the order of elements in the list in place. Tuples Tuple: An ordered, immutable (unchangeable) sequence of items. Tuples can contain items of different data types and allow duplicate elements. Defined using parentheses () . Immutability: Once a tuple is created, its elements cannot be modified, added, or removed. Indexing, Slicing, Concatenation, Repetition: Similar to lists, but these operations return new tuples rather than modifying the original. count(element) : Returns the number of times a specified element appears in the tuple. index(element) : Returns the index of the first occurrence of a specified element in the tuple. Dictionaries Dictionary: An unordered collection of key-value pairs. Each key must be unique and immutable, while values can be of any data type and mutable. Dictionaries are mutable. Defined using curly braces {} . Key-Value Pair: An association between a unique key and its corresponding value. Keys are used to retrieve values. Accessing Values: Values are accessed using their corresponding keys, e.g., my_dict['key'] . Adding/Updating Items: New key-value pairs can be added, or existing values can be updated by assigning a new value to a key. Deleting Items: Items can be deleted using the del keyword or methods like pop() . keys() : Returns a view object that displays a list of all the keys in the dictionary. values() : Returns a view object that displays a list of all the values in the dictionary. items() : Returns a view object that displays a list of a dictionary's key-value tuple pairs. get(key, default_value) : Returns the value for the specified key. If the key is not found, it returns None or the default_value if provided, instead of raising a KeyError . pop(key, default_value) : Removes the item with the specified key from the dictionary and returns its value. If the key is not found, it returns default_value if provided, otherwise raises a KeyError . clear() : Removes all items from the dictionary. update(other_dict) : Updates the dictionary with elements from another dictionary or from an iterable of key-value pairs. If a key exists, its value is updated; otherwise, the new key-value pair is added. Stacks Stack: A linear data structure that follows the LIFO (Last In, First Out) principle. The last element added to the stack is the first one to be removed. Think of a stack of plates. push() : The operation to add an element to the top of the stack. In Python, this can be implemented using list.append() . pop() : The operation to remove and return the element from the top of the stack. In Python, this can be implemented using list.pop() . peek() (or top() ): An operation to view the top element of the stack without removing it. isEmpty() : An operation to check if the stack contains any elements. Applications: Function call stack in programming, undo/redo features in software, expression evaluation (infix to postfix conversion). Queues Queue: A linear data structure that follows the FIFO (First In, First Out) principle. The first element added to the queue is the first one to be removed. Think of a line at a ticket counter. enqueue() : The operation to add an element to the rear (back) of the queue. In Python, this can be implemented using list.append() . dequeue() : The operation to remove and return the element from the front of the queue. In Python, this can be implemented using list.pop(0) (though more efficient implementations exist using collections.deque ). peek() (or front() ): An operation to view the front element of the queue without removing it. isEmpty() : An operation to check if the queue contains any elements. Applications: Printer job scheduling, CPU task scheduling, breadth-first search (BFS) algorithm. 4. Database Concepts Introduction to Databases Database: An organized collection of structured information, or data, typically stored electronically in a computer system. It is designed to efficiently store, retrieve, and manage large amounts of data. DBMS (Database Management System): Software that allows users to define, create, maintain, and control access to the database. It acts as an interface between the database and its end-users or applications. Examples: MySQL, PostgreSQL, Oracle, SQL Server. RDBMS (Relational Database Management System): A type of DBMS that organizes data into one or more tables (relations) of rows and columns. Data is structured in a way that allows it to be easily accessed and reassembled in many different ways without reorganizing the database tables. Table (Relation): A collection of related data entries organized in terms of rows and columns. Each table represents a specific entity (e.g., 'Students', 'Courses'). Row (Tuple/Record): A single entry or instance within a table, representing a complete set of related data for a particular entity. Column (Attribute/Field): A vertical entity in a table that contains all information associated with a specific attribute of the table's entity. E.g., 'Student_ID', 'Name', 'Age'. Schema: The logical design or structure of a database, describing how the data is organized, including table names, column names, data types, and relationships between tables. Instance: The actual data stored in a database at a particular moment in time. Keys Primary Key: A column or a set of columns in a table that uniquely identifies each row (record) in that table. A primary key must contain unique values and cannot contain NULL values. There can be only one primary key per table. Candidate Key: A column or a set of columns that can uniquely identify each row in a table. A table can have multiple candidate keys. A primary key is chosen from the set of candidate keys. Alternate Key: Any candidate key that is not chosen to be the primary key for a table. Foreign Key: A column or a set of columns in one table (the referencing table) that refers to the primary key of another table (the referenced table). It establishes a link or relationship between two tables. It can contain duplicate values and NULL values. Super Key: A set of one or more attributes that, taken collectively, can uniquely identify a tuple (row) in a relation (table). A candidate key is a minimal super key (i.e., no proper subset of its attributes is a super key). Relational Algebra Relational Algebra: A procedural query language that takes instances of relations as input and yields instances of relations as output. It uses a set of fundamental operations to manipulate relations. Selection ($\sigma$): A unary operation that selects a subset of rows (tuples) from a relation that satisfy a specified condition. Notation: $\sigma_{condition}(R)$. Projection ($\pi$): A unary operation that selects a subset of columns (attributes) from a relation, removing duplicate rows if any. Notation: $\pi_{A1, A2, ...}(R)$. Union ($\cup$): A binary operation that combines all rows from two relations, $R$ and $S$, provided they are union-compatible (same number of columns and corresponding data types). Duplicate rows are eliminated. Notation: $R \cup S$. Set Difference ($-$): A binary operation that returns all rows that are in relation $R$ but not in relation $S$. Relations must be union-compatible. Notation: $R - S$. Cartesian Product ($\times$): A binary operation that combines every row of the first relation with every row of the second relation. If relation $R$ has $n$ rows and $S$ has $m$ rows, $R \times S$ will have $n \times m$ rows. Notation: $R \times S$. Rename ($\rho$): A unary operation used to give a new name to a relation or to an attribute within a relation. Notation: $\rho_X(R)$ (rename relation $R$ to $X$), or $\rho_{A_1 \to B_1, A_2 \to B_2}(R)$ (rename attributes). 5. Structured Query Language (SQL) DDL (Data Definition Language) DDL: Commands used to define, modify, or delete database objects like tables, indexes, and users. CREATE DATABASE database_name; : Creates a new database. CREATE TABLE table_name (column1 datatype PRIMARY KEY, column2 datatype, ...); : Creates a new table with specified column names, data types, and constraints. ALTER TABLE table_name ADD column_name datatype; : Adds a new column to an existing table. ALTER TABLE table_name DROP COLUMN column_name; : Deletes a column from an existing table. ALTER TABLE table_name MODIFY COLUMN column_name new_datatype; : Changes the data type or size of an existing column. DROP TABLE table_name; : Deletes an entire table, including its structure and all data. TRUNCATE TABLE table_name; : Deletes all rows from a table, but keeps the table structure. It is faster than DELETE for removing all rows. DML (Data Manipulation Language) DML: Commands used to manipulate data within database objects (tables). INSERT INTO table_name (col1, col2) VALUES (val1, val2); : Adds new rows of data into a table. UPDATE table_name SET col1 = val1 WHERE condition; : Modifies existing data in one or more rows of a table based on a specified condition. DELETE FROM table_name WHERE condition; : Deletes one or more rows from a table based on a specified condition. DQL (Data Query Language) DQL: Commands used to retrieve data from the database. The primary command is SELECT . SELECT column1, column2 FROM table_name WHERE condition ORDER BY column DESC/ASC; : Retrieves data from one or more tables. SELECT : Specifies the columns to be retrieved. FROM : Specifies the table(s) from which to retrieve data. WHERE : Filters rows based on a specified condition. ORDER BY : Sorts the result set by one or more columns in ascending ( ASC ) or descending ( DESC ) order. Aggregate Functions: Functions that perform calculations on a set of values and return a single summary value. COUNT() : Returns the number of rows or non-NULL values in a column. SUM() : Calculates the sum of values in a numeric column. AVG() : Calculates the average of values in a numeric column. MIN() : Returns the minimum value in a column. MAX() : Returns the maximum value in a column. Clauses: GROUP BY : Groups rows that have the same values in specified columns into summary rows, typically used with aggregate functions. HAVING : Filters groups created by the GROUP BY clause. It is similar to WHERE but applies to groups rather than individual rows. JOINs: Used to combine rows from two or more tables based on a related column between them. INNER JOIN : Returns only the rows that have matching values in both tables. LEFT JOIN (or LEFT OUTER JOIN ): Returns all rows from the left table, and the matching rows from the right table. If there's no match, NULLs are used for the right table's columns. RIGHT JOIN (or RIGHT OUTER JOIN ): Returns all rows from the right table, and the matching rows from the left table. If there's no match, NULLs are used for the left table's columns. FULL JOIN (or FULL OUTER JOIN ): Returns all rows when there is a match in one of the tables. Returns rows from both tables, with NULLs for the side that has no match. 6. Computer Networks Network Topologies Network Topology: The arrangement of the various elements (links, nodes, etc.) of a computer network. It describes the physical or logical arrangement of nodes and connections. Bus Topology: All devices are connected to a single central cable (the "bus"). Data travels in both directions, but only one device can transmit at a time. Simple and inexpensive but a single break in the cable can bring down the entire network. Star Topology: All devices are connected to a central hub, switch, or server. Each device has a dedicated point-to-point connection to the central device. Robust (failure of one link doesn't affect others) but the central device is a single point of failure. Ring Topology: Each device is connected to exactly two other devices, forming a single continuous pathway for signals. Data travels in one direction (unidirectional ring). Token-passing is common. A break in any link can disrupt the entire network. Mesh Topology: Each device is connected to every other device in the network. Provides high redundancy and fault tolerance, as there are multiple paths for data. However, it is very expensive to implement due to the large number of connections. Tree Topology: A hybrid topology that combines characteristics of bus and star topologies. Multiple star networks are connected to a central bus cable. It allows for easy expansion and fault isolation. Types of Networks LAN (Local Area Network): A computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus, or office building. MAN (Metropolitan Area Network): A computer network that interconnects users with computer resources in a geographic region larger than that covered by a LAN but smaller than the area covered by a WAN, typically covering a city or a large campus. WAN (Wide Area Network): A telecommunications network that extends over a large geographical distance (e.g., across regions, countries, or continents). The Internet is the largest WAN. PAN (Personal Area Network): A computer network used for data transmission among devices such as computers, smartphones, tablets, and personal digital assistants. PANs can be used for communication among the personal devices themselves, or for connecting to a higher-level network such as the Internet. Typically covers a range of a few meters (e.g., Bluetooth). Network Devices Modem (Modulator-Demodulator): A device that converts digital signals from a computer into analog signals suitable for transmission over analog telephone lines or cable lines, and vice versa. Hub: A central device in a star topology that connects multiple network devices. It broadcasts incoming data packets to all connected devices, making it less efficient and less secure than a switch. Switch: A more intelligent version of a hub. It connects multiple network devices but sends incoming data packets only to the specific device for which they are intended, based on MAC addresses. This improves network efficiency and security. Repeater: A network device that regenerates and retransmits network signals. It extends the physical distance a network signal can travel by boosting its strength, thus overcoming signal degradation over long cables. Router: A networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. They connect different networks (e.g., your home LAN to the Internet WAN) and determine the best path for data to travel. Gateway: A network node that serves as an access point to another network. It can connect two networks with different protocols. A router can function as a gateway. Bridge: A network device that connects two separate LAN segments, often using the same protocol. It filters network traffic, forwarding data only to the segment where the destination device is located, thus reducing traffic on other segments. Network Protocols Protocol: A set of rules and standards that govern how data is transmitted and received between devices in a network. TCP/IP (Transmission Control Protocol/Internet Protocol): A suite of communication protocols used to interconnect network devices on the internet. It is the fundamental protocol suite for most internet traffic. TCP (Transmission Control Protocol): A connection-oriented protocol that provides reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts communicating over an IP network. IP (Internet Protocol): A connectionless protocol responsible for addressing and routing data packets across networks. It defines how data should be packaged, addressed, and sent. HTTP (Hypertext Transfer Protocol): The foundation of data communication for the World Wide Web. It is used for transmitting hypertext messages (web pages) between web servers and web browsers. HTTPS (Hypertext Transfer Protocol Secure): An extension of HTTP that encrypts communication between a web browser and a website using SSL/TLS. It provides secure communication over a computer network. FTP (File Transfer Protocol): A standard network protocol used for the transfer of computer files between a client and server on a computer network. POP3 (Post Office Protocol version 3): An application-layer protocol used by email clients to retrieve email from a mail server. It downloads emails to the local device and typically deletes them from the server. IMAP (Internet Message Access Protocol): A protocol for accessing email on a remote mail server from a local client. Unlike POP3, IMAP keeps messages on the server, allowing multiple clients to access the same mailbox and synchronize status. SMTP (Simple Mail Transfer Protocol): An internet standard communication protocol for sending electronic mail (email) across IP networks. VoIP (Voice over Internet Protocol): A technology that allows voice communication and multimedia sessions to be conducted over IP networks, such as the Internet, instead of traditional public switched telephone networks (PSTN). Remote Login (SSH, Telnet): Protocols that allow a user to log into and control a computer remotely over a network. SSH (Secure Shell): A cryptographic network protocol for operating network services securely over an unsecured network. Commonly used for remote command-line login and secure file transfer. Telnet: An older network protocol used for remote command-line login. It sends data in plain text, making it insecure for sensitive information. Wi-Fi (Wireless Fidelity): A family of wireless network protocols based on the IEEE 802.11 standards, commonly used for local area networking of devices and internet access. Bluetooth: A short-range wireless technology standard used for exchanging data between fixed and mobile devices over short distances using short-wavelength UHF radio waves. Network Security Concepts Malware (Malicious Software): Any software intentionally designed to cause damage to a computer, server, client, or computer network. Virus: A type of malware that, when executed, replicates itself by modifying other computer programs and inserting its own code. Worm: A standalone malware computer program that replicates itself in order to spread to other computers. Unlike a virus, it does not need to attach to an existing program. Trojan (Horse): A type of malware that disguises itself as legitimate software but carries out malicious functions when executed. It does not replicate itself directly. Phishing: A type of social engineering attack where an attacker attempts to trick individuals into revealing sensitive information (like usernames, passwords, credit card details) by impersonating a trustworthy entity in an electronic communication. DoS (Denial of Service) Attack: An attack that aims to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet. Snooping: Unauthorized monitoring or interception of data or communications, often to obtain sensitive information. Firewall: A network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between a trusted internal network and untrusted external networks (like the Internet). Antivirus Software: Software used to prevent, detect, and remove malicious software, including viruses, worms, and Trojans, from a computer system. Encryption: The process of converting information or data into a code to prevent unauthorized access. Encrypted data is unreadable without the correct decryption key. Digital Signature: A mathematical scheme for verifying the authenticity of digital messages or documents. It provides assurance of the message's origin, integrity, and non-repudiation. VPN (Virtual Private Network): A technology that creates a secure, encrypted connection over a less secure network, such as the Internet. It allows users to send and receive data across public networks as if their computing devices were directly connected to the private network. Cybercrime: Criminal activities carried out using computers or the internet, including hacking, phishing, identity theft, and online fraud. Cyber Law: The legal framework that addresses issues related to the Internet and other forms of cyberspace, including intellectual property, privacy, freedom of expression, and cybercrime. Mobile Telecommunication Technologies 1G (First Generation): Analog cellular technology, primarily for voice calls. Low capacity, poor voice quality, no data services. 2G (Second Generation): Digital cellular technology. Introduced SMS (text messaging) and basic data services (GPRS, EDGE). Improved voice quality and security. 3G (Third Generation): Introduced higher data transfer rates, enabling mobile internet access, video calls, and multimedia services. Examples: UMTS, CDMA2000. 4G (Fourth Generation): Fourth generation of broadband cellular network technology. Provides significantly faster internet speeds, supporting high-definition mobile TV, video conferencing, and cloud computing. Examples: LTE, WiMAX. 5G (Fifth Generation): The latest generation of cellular technology, designed to deliver extremely high speeds, ultra-low latency, greater capacity, and massive connectivity for IoT devices. 7. Data Communication Transmission Media Transmission Media: The physical path over which information is transmitted between two or more points. Guided Media (Wired): Physical media through which signals are guided along a solid medium. Twisted Pair Cable: Consists of pairs of insulated copper wires twisted together to reduce electromagnetic interference. UTP (Unshielded Twisted Pair): Most common, used in Ethernet LANs. STP (Shielded Twisted Pair): Has an extra metallic shield to further reduce interference. Coaxial Cable: Consists of a central copper conductor, an insulating layer, a metallic shield, and an outer insulating jacket. Used in cable TV and older Ethernet networks. Optical Fiber Cable: Transmits data as pulses of light through thin strands of glass or plastic. Offers very high bandwidth, long transmission distances, and immunity to electromagnetic interference. Unguided Media (Wireless): Transmits signals through the air or space without a physical conductor. Radio Waves: Electromagnetic waves used for broadcasting, mobile communication, and wireless networking. Long-distance communication, can penetrate walls. Microwaves: High-frequency radio waves used for line-of-sight communication, satellite communication, and terrestrial wireless links. Shorter wavelength than radio waves. Infrared: Uses infrared light for short-range, line-of-sight communication, typically found in remote controls and some short-distance data links. Cannot penetrate solid objects. Bandwidth Bandwidth: The maximum rate of data transfer across a given path. It is the capacity of a communication channel to transmit data, typically measured in bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps). Data Transfer Rate Data Transfer Rate: The actual speed at which data is transmitted from one place to another over a network or communication channel. It is often influenced by factors like network congestion, latency, and protocol overhead, and can be less than the theoretical bandwidth. 8. Societal Impacts of IT Digital Footprint Digital Footprint: The trail of data that a person leaves behind when using the Internet or digital devices. It includes all records and traces that a person or entity leaves online. Active Digital Footprint: Data that a user intentionally submits online, such as posts on social media, comments, emails, or online forms. Passive Digital Footprint: Data collected without the user's explicit knowledge, such as browsing history, IP address, location data, or cookie information. Digital Society and Net Etiquettes Digital Society: A society where the creation, distribution, and manipulation of information have become the most significant economic and cultural activities. It is characterized by the widespread use of digital technologies in all aspects of life. Net Etiquettes (Network Etiquette): The rules of polite and appropriate behavior and communication when interacting with others online, such as in emails, forums, social media, and chat rooms. It encompasses respect, clarity, and professionalism in digital interactions. Data Protection and Privacy Data Protection: The set of policies, procedures, and legal frameworks designed to safeguard personal information from unauthorized access, use, disclosure, alteration, or destruction. Privacy: The right of individuals to control the collection, use, and dissemination of their personal information. In the digital age, it concerns how personal data is handled by organizations and governments. Intellectual Property Rights (IPR) Intellectual Property Rights (IPR): Legal rights that protect creations of the mind. They grant creators exclusive rights over the use of their creations for a certain period. Copyright: A legal right granted to the creator of original literary, dramatic, musical, and artistic works (including software code, books, music, films, and websites). It gives the creator exclusive rights to reproduce, distribute, perform, display, or license their work. Patent: An exclusive right granted for an invention, which is a product or process that provides a new way of doing something, or offers a new technical solution to a problem. It allows the patent owner to prevent others from making, using, or selling the invention. Trademark: A recognizable sign, design, or expression that identifies products or services of a particular source from those of others. It helps consumers distinguish goods and services. Plagiarism: The act of presenting someone else's work or ideas as your own, without proper attribution, whether intentionally or unintentionally. It is a serious academic and ethical offense. Open Source Concepts Open Source Software (OSS): Software whose source code is made available to the public with a license that allows users to study, change, and distribute the software to anyone and for any purpose. Examples: Linux, Python, Firefox. Freeware: Software that is available for use free of charge, but usually comes with proprietary licensing terms that restrict modification, redistribution, or reverse engineering. The source code is typically not available. Shareware: Software that is distributed free of charge on a trial basis, often with limited features or for a limited time. Users are usually encouraged or required to pay a fee to unlock full functionality or continue using it after the trial period. Proprietary Software: Software whose source code is not publicly available and whose use, modification, and redistribution are restricted by its owner (vendor). Users typically purchase a license to use it under specific terms. Examples: Microsoft Windows, Adobe Photoshop. E-Waste Management E-Waste (Electronic Waste): Discarded electrical or electronic devices. It includes old computers, mobile phones, televisions, refrigerators, etc. E-Waste Management: The process of handling, collecting, dismantling, recycling, and disposing of electronic waste in an environmentally sound manner to minimize its harmful effects on the environment and human health. Health Concerns Ergonomics: The science of designing and arranging workplaces, products, and systems so that they fit the people who use them. In computing, it focuses on designing comfortable and efficient computer workstations to prevent injuries. Eye Strain: A common condition resulting from intense use of the eyes, especially when looking at digital screens for prolonged periods. Symptoms include tired, aching eyes, blurred vision, and headaches. RSI (Repetitive Strain Injury): An umbrella term for pain and discomfort in muscles, tendons, and nerves caused by repetitive tasks, forceful exertions, vibrations, mechanical compression, or sustained awkward positions. Common in computer users (e.g., carpal tunnel syndrome). Digital Addiction: A behavioral addiction characterized by compulsive use of digital technologies (internet, social media, video games) to the extent that it interferes with daily life, relationships, and well-being.