Difference Between Compiler and Interpreter

• Translation Method: A compiler translates the entire source code at once; an interpreter translates and executes code line by line.
• Execution Speed: Compiled programs execute faster; interpreted programs execute slower.
• Error Detection: A compiler shows errors after compiling the whole program; an interpreter shows errors one by one during execution.
• Output: A compiler generates object/executable code; an interpreter does not generate separate object code.
• Memory Usage: Compiler requires more memory to store object code; interpreter requires less memory.
• Examples: C, C++ use compiler; Python, JavaScript use interpreter.

SDLC is a structured process used to develop high-quality software in a systematic and organized manner. It defines a set of phases that guide the development team from planning to maintenance.

Phases of SDLC:

1. Planning: Identify the problem, define objectives, scope, budget, and feasibility of the project.
2. Requirement Analysis: Gather and analyze user requirements to determine what the system should do.
3. System Design: Prepare system architecture, database design, interface design, and technical specifications.
4. Implementation (Coding): Develop the software according to the design.
5. Testing: Test the system to detect and fix errors (unit, integration, system testing).
6. Deployment: Install and release the software for users.
7. Maintenance: Provide updates, fix bugs, and improve performance after deployment.

Difference Between while and do-while Loop (With Example)

• Condition Checking: In a while loop, the condition is checked before executing the loop body; in a do-while loop, the condition is checked after executing the loop body.
• Execution Guarantee: A while loop may execute zero times if the condition is false; a do-while loop executes at least once.
• Type of Loop: while is an entry-controlled loop; do-while is an exit-controlled loop.
• Syntax Structure: In while loop, the condition appears at the beginning; in do-while loop, the condition appears at the end.
• Semicolon Usage: while loop does not require a semicolon after the condition; do-while loop requires a semicolon at the end.

Example:

while loop:
int i = 5;
while(i < 5) {
System.out.println(i);
i++;
}
(Output: No output because condition is false at the beginning)

do-while loop:
int i = 5;
do {
System.out.println(i);
i++;
} while(i < 5);
(Output: 5 → Executes at least once)

RSA Algorithm (Public Key Cryptography)

RSA is an asymmetric encryption algorithm that uses two keys: a Public Key and a Private Key.

Step 1: Key Generation

1. Choose two large prime numbers: p and q.
2. Compute n = p × q.
3. Compute Euler’s Totient: φ(n) = (p − 1)(q − 1).
4. Choose an integer e such that:
   • 1 < e < φ(n)
   • gcd(e, φ(n)) = 1
5. Compute d such that:
   d × e ≡ 1 (mod φ(n))

Public Key: (e, n)
Private Key: (d, n)

Step 2: Encryption
To encrypt message M:
C = M^e mod n

Step 3: Decryption
To decrypt ciphertext C:

M = C^d mod n

Binary Search Algorithm

Binary Search is used to find a key element in a sorted array by repeatedly dividing the search interval into two halves.

Pseudocode:

BINARY_SEARCH(A, n, key)
1. low ← 0
2. high ← n - 1
3. while low ≤ high do
4.     mid ← (low + high) / 2
5.     if A[mid] = key then
6.         return mid
7.     else if A[mid] < key then
8.         low ← mid + 1
9.     else
10.        high ← mid - 1
11. return -1

Explanation:

• If the key equals the middle element, return its index.
• If the key is greater, search the right half.
• If the key is smaller, search the left half.
• If not found, return -1.

Time Complexity: O(log n)
Space Complexity: O(1)

Types of CPU Scheduling

• First Come First Serve (FCFS): Processes are executed in the order of their arrival.
• Shortest Job First (SJF): The process with the shortest burst time is executed first.
• Shortest Remaining Time First (SRTF): Preemptive version of SJF where the process with the shortest remaining time is selected.
• Priority Scheduling: The process with the highest priority is executed first.
• Round Robin (RR): Each process gets a fixed time quantum in cyclic order.
• Multilevel Queue Scheduling: Processes are divided into different queues based on priority or type.
• Multilevel Feedback Queue: Processes can move between queues based on their behavior and execution history.

Best Performing CPU Scheduling Method – Shortest Job First (SJF)

Shortest Job First (SJF) is considered one of the best scheduling algorithms in terms of performance because it minimizes the average waiting time.

• Working Principle: The process with the smallest CPU burst time is selected first.
• Performance: It gives minimum average waiting time among all scheduling algorithms.
• Efficiency: Short processes are completed quickly, improving overall throughput.
• Limitation: It may cause starvation for long processes.

Types of Information Security Against Cyber Threats

Information Security includes different protective measures to safeguard data and systems from cyber attacks.

1. Network Security: Protects network infrastructure from unauthorized access and attacks using Firewall, IDS/IPS, VPN, etc.
2. Application Security: Secures software and applications from vulnerabilities through secure coding, patch management, and testing.
3. Data Security: Protects sensitive data using encryption, data masking, and backup systems.
4. Endpoint Security: Secures end-user devices such as computers and smartphones using antivirus and anti-malware tools.
5. Cloud Security: Protects cloud-based systems and data using access control, encryption, and monitoring.
6. Identity and Access Management (IAM): Controls user authentication and authorization using passwords, biometrics, and multi-factor authentication (MFA).
7. Physical Security: Protects hardware and infrastructure from physical damage or theft.

Conclusion: Effective information security requires a combination of technical, administrative, and physical controls to protect against cyber threats.

• To enforce business rules automatically.
• To maintain data integrity.
• To audit changes (track modifications).
• To automatically update related tables.

CREATE TRIGGER emp_log
AFTER INSERT ON Employee
FOR EACH ROW
BEGIN
   INSERT INTO Employee_Log(emp_id, action)
   VALUES (NEW.id, 'New Employee Added');
END;

• This trigger runs automatically after a new record is inserted into the Employee table.
• It stores the employee ID and action in the Employee_Log table.