Difference between Heap Sort and Merge Sort
Heap Sort
• Based on Binary Heap data structure
• Sorting is done in-place
• Time Complexity: O(n log n) in all cases
• Space Complexity: O(1) (in-place)
• Not stable sorting algorithm
Example: Array: [4,10,3,5,1] → Build Max-Heap → Extract max repeatedly → Sorted array: [1,3,4,5,10]

Merge Sort
• Based on Divide and Conquer approach
• Array is divided into subarrays and merged
• Time Complexity: O(n log n) in all cases
• Space Complexity: O(n) (extra memory needed)
• Stable sorting algorithm
Example: Array: [4,10,3,5,1] → Divide into halves → Merge sorted halves → Sorted array: [1,3,4,5,10]

Stateless Protocol
A stateless protocol does not remember previous interactions between the client and server. Each request is treated independently and must contain all the required information to be processed.
Example: HTTP, UDP

Stateful Protocol
A stateful protocol maintains session information about previous interactions. The server remembers the client’s state and uses it to process future requests.
Example: FTP, TCP

Which Type of Protocol is HTTP?
HTTP is a stateless protocol. Each HTTP request is independent, and the server does not store client information between requests. State management is achieved using cookies and sessions.

Subnet Mask of 10.2.1.3/26
/26 means 26 bits are used for the network part.
Subnet Mask = 255.255.255.192

Usable Number of IP Addresses
Host bits = 32 − 26 = 6
Total IP addresses = 2⁶ = 64
Usable IP addresses = 64 − 2 (Network + Broadcast) = 62

Purpose of Routers
Routers are network devices used to connect multiple networks and forward data packets between them based on IP addresses. They select the best path for data using routing tables and protocols, helping reduce traffic and improve network efficiency.

Congestion Control in TCP
TCP congestion control prevents network overload by adjusting the data transmission rate. It uses mechanisms such as Slow Start (gradually increases sending rate), Congestion Avoidance (careful growth of data rate), Fast Retransmit, and Fast Recovery. TCP detects congestion through packet loss or delay and reduces the sending rate to maintain reliable communication.

Purpose of Database Triggers
A database trigger is a special stored program that automatically executes when an INSERT, UPDATE, or DELETE operation occurs on a table. Triggers are used to maintain data integrity, enforce business rules, and perform automatic actions without user intervention.

Example
Automatically log salary changes of employees.

CREATE TRIGGER salary_update_trigger 
AFTER UPDATE ON employee 
FOR EACH ROW BEGIN 
INSERT INTO salary_log(emp_id, old_salary, new_salary)
 VALUES (OLD.emp_id, OLD.salary, NEW.salary); 
END;

Types of Database Keys
Primary Key: A key that uniquely identifies each record in a table and cannot be NULL.
Example: Student(student_id, name) → student_id

Foreign Key: A key that references the primary key of another table to maintain relationships.
Example: Order(customer_id) references Customer(customer_id)

Candidate Key: All possible keys that can uniquely identify records; one is chosen as primary key.
Example: Employee(emp_id, email) → emp_id, email

Super Key: A set of one or more attributes that uniquely identify records (may contain extra attributes).
Example: (emp_id, name)

Composite Key: A key formed by combining two or more attributes.
Example: Enrollment(student_id, course_id)

DFS vs BFS: Speed and Memory
Which is faster? It depends on the problem. BFS is faster for finding the shortest path (in unweighted graphs) because it explores level by level. DFS may be faster when the solution is deep and not necessarily the shortest.

Which uses more memory? BFS requires more memory because it stores all nodes at the current level (queue). DFS uses less memory as it stores only the path being explored (stack/recursion).

Difference between Linked List and Stack
Linked List
• A dynamic data structure consisting of nodes linked by pointers
• Insertion and deletion can be done at any position
• No restriction on access order
• Can be singly, doubly, or circular linked list
• Used to implement dynamic memory structures

Stack
• A linear data structure following LIFO (Last In First Out) principle
• Insertion (push) and deletion (pop) occur only at one end (top)
• Restricted access to elements
• Can be implemented using array or linked list
• Used in function calls, expression evaluation, undo operations

Difference between Supervised and Unsupervised Learning
Supervised Learning
• Uses labeled data (input with known output)
• Learns by mapping inputs to correct outputs
• Used for prediction and classification tasks
• Requires training data with labels
Example: Email spam detection, house price prediction, student result prediction

Unsupervised Learning
• Uses unlabeled data (no predefined output)
• Finds hidden patterns or groupings in data
• Used for clustering and association analysis
• Does not require labeled data
Example: Customer segmentation, market basket analysis, grouping similar images

Three Types of Cloud Services
1) IaaS (Infrastructure as a Service): Provides virtualized hardware resources like servers, storage, and networks.
Example: Amazon EC2, Google Compute Engine

2) PaaS (Platform as a Service): Provides a platform to develop, test, and deploy applications without managing infrastructure.
Example: Google App Engine, Heroku

3) SaaS (Software as a Service): Provides ready-to-use software applications over the internet.
Example: Gmail, Microsoft Office 365

Difference between FDM and TDM
Frequency Division Multiplexing (FDM)
• Divides the available bandwidth into multiple frequency bands
• Each signal is transmitted simultaneously on different frequencies
• Requires guard bands to avoid interference
• Used mainly in analog communication
Example: Radio and cable TV transmission

Time Division Multiplexing (TDM)
• Divides the channel into different time slots
• Each signal uses the full bandwidth but at different times
• No guard band is required
• Used mainly in digital communication
Example: Digital telephony, GSM

Difference between Vector and Raster Graphics
Vector Graphics
• Based on mathematical paths (lines, curves, shapes)
• Resolution-independent; no quality loss on scaling
• Smaller file size for simple images
• Easy to edit shapes and colors
Examples: SVG, AI, EPS

Raster Graphics
• Made of pixels arranged in a grid
• Resolution-dependent; quality degrades when scaled up
• Larger file size for high resolution
• Best for complex images and photos
Examples: JPEG, PNG, BMP

Applications of Computer Graphics
• User interfaces and web design
• Animation, movies, and games
• Medical imaging and visualization
• CAD/CAM and engineering design
• Education, simulations, and data visualization

Thread
A thread is the smallest unit of execution within a process. Multiple threads can exist inside a single process and share the same memory and resources while executing independently.

Benefits of Multithreaded Programming
• Better CPU utilization by running tasks in parallel
• Faster execution and improved application performance
• Efficient resource sharing (shared memory)
• Improved responsiveness (e.g., UI remains active)
• Lower overhead compared to multiple processes

Artificial Intelligence (AI)
Artificial Intelligence (AI) is a branch of computer science that focuses on creating systems capable of performing tasks that normally require human intelligence, such as learning, reasoning, problem-solving, decision-making, and understanding natural language.

Necessary Conditions for Deadlock in an Operating System
A deadlock occurs when a set of processes are blocked forever because each process is holding a resource and waiting for another. For a deadlock to occur, the following four conditions must hold simultaneously:
• Mutual Exclusion: At least one resource must be held in a non-shareable mode.
• Hold and Wait: A process holds one or more resources while waiting for additional resources.
• No Preemption: Resources cannot be forcibly taken from a process; they must be released voluntarily.
• Circular Wait: A circular chain of processes exists where each process waits for a resource held by the next process.