Computer Science section is highly important and challenging in modern competitive exams like SSC CGL (Tier 2), RRB NTPC, Banking, and State Level IT Officer exams. Attempt these Top 100 Hard-Level MCQs covering advanced Networking, OS, Database, and Cryptography. After attempting, click on ‘Show Answer’ to see the detailed explanation.
Q. 1. Which of the following is a symmetric key cryptographic algorithm?
(a) RSA
(b) DSA
(c) AES
(d) Diffie-Hellman
Answer:-(c) AES
AES (Advanced Encryption Standard) is a symmetric key algorithm, meaning the same key is used for both encrypting and decrypting the data.
Q. 2. In OSI model, which layer is responsible for logical addressing and routing?
(a) Data Link Layer
(b) Network Layer
(c) Transport Layer
(d) Session Layer
Answer:-(b) Network Layer
The Network Layer is responsible for logical addressing (IP addresses) and routing packets across different networks.
Q. 3. What is the primary function of a TLB (Translation Lookaside Buffer)?
(a) To cache frequently used data
(b) To cache recently accessed instructions
(c) To cache recent virtual-to-physical address translations
(d) To manage disk I/O operations
Answer:-(c) To cache recent virtual-to-physical address translations
A TLB acts as a memory cache that stores recent translations of virtual memory to physical memory, speeding up memory access.
Q. 4. Which of the following sorting algorithms has the worst-case time complexity of O(n log n)?
(a) Quick Sort
(b) Merge Sort
(c) Bubble Sort
(d) Insertion Sort
Answer:-(b) Merge Sort
Merge Sort consistently divides the array in half and takes linear time to merge, guaranteeing an O(n log n) time complexity in all cases.
Q. 5. In relational databases, what does the ACID property ‘Isolation’ guarantee?
(a) Transactions are executed fully or not at all
(b) Data remains valid after transaction completion
(c) Concurrent transactions run as if they were executed sequentially
(d) Completed transactions are permanently saved
Answer:-(c) Concurrent transactions run as if they were executed sequentially
Isolation ensures that concurrent execution of transactions leaves the database in the same state that would have been obtained if the transactions were executed sequentially.
Q. 6. What is the purpose of the ‘BGP’ (Border Gateway Protocol)?
(a) To map IP addresses to MAC addresses
(b) To assign dynamic IP addresses
(c) To route data between autonomous systems on the internet
(d) To translate private IP addresses to public IPs
Answer:-(c) To route data between autonomous systems on the internet
BGP is the core routing protocol of the internet, designed to exchange routing and reachability information among autonomous systems (AS).
Q. 7. Which of the following scheduling algorithms can suffer from ‘Starvation’?
(a) Round Robin
(b) First-Come, First-Served (FCFS)
(c) Shortest Job Next (SJN)
(d) Multi-level Feedback Queue
Answer:-(c) Shortest Job Next (SJN)
In SJN, a continuous stream of short CPU bursts could cause a long process to wait indefinitely, resulting in starvation.
Q. 8. In cryptography, what is a ‘Salt’?
(a) A secret key used in symmetric encryption
(b) Random data added to a password before hashing
(c) A technique to compress secure data
(d) A type of digital signature algorithm
Answer:-(b) Random data added to a password before hashing
A salt is random data that is used as an additional input to a one-way function that hashes data, primary used to defend against dictionary attacks and pre-computed rainbow tables.
Q. 9. What is the main difference between TCP and UDP?
(a) TCP is connectionless, UDP is connection-oriented
(b) TCP provides reliable delivery, UDP does not
(c) TCP is faster than UDP
(d) UDP operates at the Network layer, TCP at the Transport layer
Answer:-(b) TCP provides reliable delivery, UDP does not
TCP establishes a connection and ensures reliable, ordered data delivery. UDP is connectionless and sends packets without guaranteeing delivery or order, making it faster but less reliable.
Q. 10. Which normal form (NF) in database normalization deals with multi-valued dependencies?
(a) 2NF
(b) 3NF
(c) BCNF
(d) 4NF
Answer:-(d) 4NF
Fourth Normal Form (4NF) aims to eliminate independent multi-valued dependencies, ensuring that a relation is in at least BCNF and contains no non-trivial multi-valued dependencies.
Q. 11. Advanced Web Tech Concept Q11: Which HTTP status code indicates ‘Forbidden’?
(a) 403
(b) 404
(c) 401
(d) 400
Answer:-(a) 403
403 Forbidden means the server understood the request but refuses to authorize it.
Q. 12. Advanced Databases Concept Q12: What is the highest isolation level in SQL standards?
(a) Read Uncommitted
(b) Serializable
(c) Read Committed
(d) Repeatable Read
Answer:-(b) Serializable
Serializable is the highest isolation level, ensuring complete isolation from other concurrent transactions.
Q. 13. Advanced Security Concept Q13: Which attack involves sending forged ARP messages to a LAN?
(a) IP Spoofing
(b) ARP Spoofing
(c) DNS Poisoning
(d) MAC Spoofing
Answer:-(b) ARP Spoofing
ARP spoofing or ARP poisoning involves sending forged ARP messages to associate an attacker’s MAC address with the IP address of a legitimate node.
Q. 14. Advanced Security Concept Q14: Which attack involves sending forged ARP messages to a LAN?
(a) DNS Poisoning
(b) IP Spoofing
(c) ARP Spoofing
(d) MAC Spoofing
Answer:-(c) ARP Spoofing
ARP spoofing or ARP poisoning involves sending forged ARP messages to associate an attacker’s MAC address with the IP address of a legitimate node.
Q. 15. Advanced Architecture Concept Q15: Which architectural feature introduces overlapping execution of multiple instructions?
(a) Caching
(b) Virtual Memory
(c) Pipelining
(d) Multithreading
Answer:-(c) Pipelining
Pipelining allows multiple instructions to be overlapped in execution to increase instruction throughput.
Q. 16. Advanced Security Concept Q16: Which attack involves sending forged ARP messages to a LAN?
(a) ARP Spoofing
(b) DNS Poisoning
(c) MAC Spoofing
(d) IP Spoofing
Answer:-(a) ARP Spoofing
ARP spoofing or ARP poisoning involves sending forged ARP messages to associate an attacker’s MAC address with the IP address of a legitimate node.
Q. 17. Advanced Architecture Concept Q17: Which architectural feature introduces overlapping execution of multiple instructions?
(a) Multithreading
(b) Virtual Memory
(c) Pipelining
(d) Caching
Answer:-(c) Pipelining
Pipelining allows multiple instructions to be overlapped in execution to increase instruction throughput.
Q. 18. Advanced Databases Concept Q18: What is the highest isolation level in SQL standards?
(a) Read Committed
(b) Repeatable Read
(c) Read Uncommitted
(d) Serializable
Answer:-(d) Serializable
Serializable is the highest isolation level, ensuring complete isolation from other concurrent transactions.
Q. 19. Advanced Data Structures Concept Q19: What is the worst-case time complexity of searching in a Binary Search Tree (BST)?
(a) O(1)
(b) O(log n)
(c) O(n log n)
(d) O(n)
Answer:-(d) O(n)
In the worst case (a highly unbalanced/skewed tree), searching degrades to linear time O(n).
Q. 20. Advanced Web Tech Concept Q20: Which HTTP status code indicates ‘Forbidden’?
(a) 400
(b) 401
(c) 403
(d) 404
Answer:-(c) 403
403 Forbidden means the server understood the request but refuses to authorize it.
Q. 21. Advanced Data Structures Concept Q21: What is the worst-case time complexity of searching in a Binary Search Tree (BST)?
(a) O(1)
(b) O(n log n)
(c) O(n)
(d) O(log n)
Answer:-(c) O(n)
In the worst case (a highly unbalanced/skewed tree), searching degrades to linear time O(n).
Q. 22. Advanced Architecture Concept Q22: Which architectural feature introduces overlapping execution of multiple instructions?
(a) Virtual Memory
(b) Caching
(c) Pipelining
(d) Multithreading
Answer:-(c) Pipelining
Pipelining allows multiple instructions to be overlapped in execution to increase instruction throughput.
Q. 23. Advanced Operating Systems Concept Q23: Which page replacement algorithm suffers from Belady’s Anomaly?
(a) LRU
(b) Optimal
(c) FIFO
(d) LFU
Answer:-(c) FIFO
Belady’s Anomaly occurs in FIFO where increasing the number of page frames results in an increase in the number of page faults.
Q. 24. Advanced Databases Concept Q24: What is the highest isolation level in SQL standards?
(a) Read Uncommitted
(b) Read Committed
(c) Serializable
(d) Repeatable Read
Answer:-(c) Serializable
Serializable is the highest isolation level, ensuring complete isolation from other concurrent transactions.
Q. 25. Advanced Networking Concept Q25: What is the size of an IPv6 address?
(a) 64 bits
(b) 32 bits
(c) 256 bits
(d) 128 bits
Answer:-(d) 128 bits
IPv6 addresses are 128 bits long, compared to 32 bits for IPv4.
