Computer Science Examination
Instructions:
1. Answer ALL questions.
2. Show all workings where applicable.
3. Time allowed: 2 Hours.
4. Each question carries equal marks unless otherwise stated.
1. Explain the difference between a compiler and an interpreter.
Answer:
A compiler translates the entire program into machine code before execution, producing an
executable file. An interpreter translates and executes the program line by line, without producing a
separate executable.
2. Write a SQL query to retrieve all students with marks above 70 from a table named
Students.
Answer:
SQL Query:
SELECT * FROM Students WHERE marks > 70;
3. Describe three differences between TCP and UDP.
Answer:
- TCP is connection-oriented, UDP is connectionless.
- TCP guarantees reliable delivery, UDP does not.
- TCP has higher overhead due to error-checking and acknowledgments, UDP is faster with less
overhead.
4. Explain the concept of process synchronization in operating systems.
Answer:
Process synchronization ensures that multiple processes can operate safely when accessing
shared resources, preventing race conditions and ensuring data consistency. Common
mechanisms include semaphores, mutexes, and monitors.
5. List and briefly explain the four principles of Object-Oriented Programming (OOP).
Answer:
1. Encapsulation โ Bundling data with methods.
2. Abstraction โ Hiding unnecessary details.
3. Inheritance โ Deriving new classes from existing ones.
4. Polymorphism โ One interface, multiple implementations.
6. A password system stores hashes instead of plaintext passwords. Explain why this is
important.
Answer:
Storing hashes increases security by preventing attackers from directly obtaining user passwords if
the database is compromised. Even if hashes are stolen, reversing them is computationally difficult,
especially with salted hashes.
7. Differentiate between Waterfall and Agile models in Software Engineering.
