Q1. A computer has 128 MB memory and each word is 8 bytes. How many bits are required to address a single word?
Why: Memory size = 128 MB = 2²⁷ bytes. Word size = 8 bytes = 2³ bytes. Total number of words = 2²⁷ / 2³ = 2²⁴ words. Therefore, 24 bits are required to uniquely address each word.
Q2. For a processor with 5 ns cache-hit time, 50 ns cache-miss time, and 80% hit rate, what is the average read access time?
Why: Average Access Time = (Hit Rate × Hit Time) + (Miss Rate × Miss Time) = (0.80 × 5) + (0.20 × 50) = 4 ns + 10 ns = 14 ns.
Q3. In memory management, page size depends primarily on which factor?
Why: Page size is determined by the underlying hardware architecture (MMU and CPU design), not by the operating system software.
Q4. A memory-resident virus is also called what?
Why: A memory-resident virus installs itself into system RAM and modifies system interrupt vectors to hide its presence, making it a Stealth Virus.
Q5. What is the restriction on page size for the indirect-addressing case described in paging theory?
Why: In indirect addressing schemes within paging hardware, to ensure valid multi-level pointer offsets without ambiguity, the page size must satisfy Page-size ≤ 2^(k-1).
Q6. Which page-replacement algorithm requires knowledge of future page references?
Why: The Optimal Page Replacement algorithm (OPT) replaces the page that will not be used for the longest period of time in the future. Because it requires knowledge of future reference string, it is theoretical and used as a benchmark.
Q7. Which of these is NOT an Operating System function?
Why: Virus protection is performed by third-party antivirus utility software. Memory management, Process management, and Processor management are fundamental core OS functions.
Q8. Which scheduling algorithm is designed especially for time-sharing systems?
Why: Round Robin scheduling assigns a fixed time quantum to each process in a cyclic order, making it ideally suited for interactive multi-user time-sharing environments.
Q9. Under which scheduling policy does preemptive context switching NOT occur?
Why: FCFS is strictly a non-preemptive scheduling policy: once the CPU has been allocated to a process, that process keeps the CPU until it releases it.
Q10. Which system call loads/replaces the current process image with an executable binary?
Why: The exec() family of functions replaces the current process image with a new process image loaded from a specified binary file.
Q11. A blocked process that has completed its I/O operation moves to which state?
Why: When a waiting/blocked process completes its I/O event, it transitions to the Ready state, joining the ready queue until the CPU scheduler selects it.
Q12. A system has 3 processes, 4 resource units, and each process may need at most 2 units. Deadlock under the stated conditions:
Why: Condition for guaranteed deadlock freedom: R ≥ N × (Max - 1) + 1. Here N=3 processes, Max=2 resources/process. Minimum R needed = 3 × (2 - 1) + 1 = 4. Since 4 units are available, deadlock can NEVER occur.
Q13. On a 19.2 kbps asynchronous line, with 7 data bits, 1 parity bit, 1 start bit and 1 stop bit per character, what is the maximum characters per second?
Why: Total bits transmitted per character = 7 + 1 + 1 + 1 = 10 bits/char. Bit rate = 19.2 kbps = 19,200 bits per second. Max characters/sec = 19,200 / 10 = 1920 cps.
Q14. Which routing-protocol type uses the Shortest Path First algorithm?
Why: Link State routing protocols (e.g., OSPF, IS-IS) collect topology information from all routers and apply Dijkstra's Shortest Path First (SPF) algorithm to calculate the optimal path.
Q15. A UDP server and a TCP server each maintain 100 client sessions. How many sockets do they use respectively?
Why: UDP is connectionless; a single socket receives datagrams from all 100 clients (1 socket). TCP is connection-oriented; it needs 1 listening socket + 100 dedicated connected sockets = 101 sockets.
Q16. If a TCP receiver advertises 20 kB and the congestion window is 10 kB, what sender window should be used?
Why: Effective Transmission Window = min(Receiver Window, Congestion Window) = min(20 KB, 10 KB) = 10 KB to prevent network congestion or receiver buffer overflow.
Q17. For a noiseless channel of 1000 Hz bandwidth with two signal levels, what is the maximum bit rate?
Why: Using Nyquist Bit Rate Formula: Bit Rate = 2 × Bandwidth × log₂(Levels) = 2 × 1000 × log₂(2) = 2000 bps.
Q18. Which data structure follows the Last-In-First-Out (LIFO) order of operation?
Why: A Stack operates on the LIFO principle, where elements pushed last are popped first (e.g. call stack, undo operations). Queue operates on FIFO.
Q19. What is the worst-case time complexity of QuickSort algorithm?
Why: QuickSort worst case occurs when the chosen pivot is always the smallest or largest element (e.g. sorted array with bad pivot), leading to O(n²) time complexity.
Q20. In a binary search tree (BST), which traversal produces sorted elements in ascending order?
Why: In-order traversal (Left, Root, Right) of a Binary Search Tree visits nodes in strictly sorted ascending numerical key order.
Q21. Minimum number of queues required to implement a priority queue efficiently is:
Why: If using simple FIFO queues to implement fixed priority queueing, one queue per distinct priority level is required.
Q22. Which normal form is based on the concept of full functional dependency?
Why: A relation is in 2NF if it is in 1NF and no non-prime attribute is partially dependent on any candidate key (i.e. full functional dependency required).
Q23. In SQL, which command is used to remove a table along with its structure and data from a database?
Why: DROP TABLE removes the entire table definition, constraints, and rows. DELETE removes rows matching criteria. TRUNCATE removes all rows keeping schema structure.
Q24. ACID properties of a transaction stand for:
Why: ACID stands for Atomicity (all or nothing), Consistency (preserves invariants), Isolation (transactions execution independent), and Durability (committed changes persist).
Q25. Which lock type allows multiple transactions to read a data item concurrently but prevents write operations?
Why: Shared locks (S) permit multiple transactions to read a resource simultaneously. Exclusive locks (X) grant sole read/write access to a single transaction.
Q26. Which addressing mode is used in instructions like 'MOV A, @R0' where operand address is held in a register?
Why: In Register Indirect mode, the instruction specifies a register that contains the memory address of the operand (indicated by @ or parentheses).
Q27. DMA (Direct Memory Access) transfer is controlled by which component?
Why: DMA Controller takes control of system buses from the CPU to transfer block data directly between I/O device and main RAM without CPU intervention.
Q28. How many selection lines are required for a 32-to-1 Multiplexer (MUX)?
Why: For a 2^n to 1 multiplexer, n selection lines are required. Since 32 = 2⁵, exactly 5 selection lines are required.
Q29. Which software development lifecycle model is best suited for projects with high risk and evolving requirements?
Why: The Spiral Model combines iterative prototyping with systematic risk analysis at each cycle, making it optimal for high-risk software projects.
Q30. Coupling between software modules measures what characteristic?
Why: Coupling measures the degree of interdependence between different software modules (low coupling is desired). Cohesion measures intra-module strength.
Q31. Cyclomatic Complexity of a software module with 10 edges (E) and 7 nodes (N) is:
Why: Cyclomatic Complexity V(G) = E - N + 2P. For a single program connected graph (P=1): V(G) = 10 - 7 + 2 = 5.
Q32. Which machine is capable of recognizing Context-Sensitive Languages (CSL)?
Why: Linear Bounded Automata (LBA) is a restricted Turing Machine that recognizes Context-Sensitive Languages (Type-1 grammar in Chomsky hierarchy).
Q33. The lexical analysis phase of a compiler produces which output?
Why: Lexical Analyzer (Scanner) reads source characters and groups them into meaningful token sequences (keywords, identifiers, operators).
Q34. In virtual memory system, TLB stands for:
Why: TLB is a fast hardware memory cache used by MMU to reduce virtual address to physical address translation time.
Q35. Banker's Algorithm in an operating system is used for:
Why: Banker's Algorithm tests for safe states before allocating resources to avoid entering an unsafe state that could cause deadlock.
Q36. What is the worst-case space complexity of Depth First Search (DFS) on a tree of height h?
Why: DFS uses a recursion stack that grows to the maximum depth of the tree path, yielding O(h) space complexity.
Q37. In relational algebra, which operator selects rows that satisfy a given predicate?
Why: Selection (σ) filters tuple rows matching a boolean condition. Projection (π) selects specific columns/attributes.
Q38. Black box testing techniques primarily test which aspect of software?
Why: Black box testing examines functional system behavior against specified requirements without examining underlying code structure.
Q39. A 4-stage instruction pipeline has stage delays of 10ns, 20ns, 12ns, and 15ns. What is the minimum clock cycle time?
Why: Clock cycle time of a pipeline is bounded by the slowest stage delay + overhead. Maximum stage delay = max(10, 20, 12, 15) = 20 ns.
Q40. Which MAC layer mechanism is used in Wi-Fi (IEEE 802.11) wireless networks for collision management?
Why: Wi-Fi networks use CSMA/CA (Collision Avoidance) because wireless transceivers cannot detect collisions while transmitting.
Q41. Which class of formal languages is closed under union, intersection, complementation, concatenation, and Kleene star?
Why: Regular languages are closed under all boolean and set operations: Union, Intersection, Complementation, Concatenation, Reversal, and Kleene Star.
Q42. Regular Expressions can be parsed and recognized using which class of automaton?
Why: According to Kleene's Theorem, every regular expression can be converted into a Deterministic or Nondeterministic Finite Automaton.
Q43. How does an LALR(1) parser differ from an LR(1) parser during construction?
Why: LALR(1) combines LR(1) states with identical production cores by merging their lookaheads, reducing the total state count to equal SLR(1) state count.
Q44. Which intermediate code form explicitly specifies at most three memory addresses (two operands, one result) per instruction?
Why: Three-Address Code (TAC) consists of quadruples/triples where each instruction contains at most 3 addresses, e.g., t1 = a + b.
Q45. In an instruction cycle with Indirect Addressing Mode, how many total memory accesses are needed to execute a data manipulation instruction?
Why: Indirect addressing requires 3 memory cycles: (1) Fetch the instruction from memory, (2) Fetch the effective address pointer from memory, (3) Fetch/write the actual operand data.
Q46. In IEEE 754 single-precision 32-bit floating-point format, how many bits are assigned to Sign, Exponent, and Mantissa (Fraction)?
Why: IEEE 754 32-bit standard uses 1 sign bit (S), 8 biased exponent bits (E, bias=127), and 23 fraction/mantissa bits (M). Total = 1 + 8 + 23 = 32 bits.
Q47. What is the worst-case time complexity of building a Binary Heap (Build-Heap algorithm) from an unsorted array of n elements?
Why: Using bottom-up heapification starting from parent nodes (n/2 down to 1), the sum of heights simplifies to O(n) linear time.
Q48. In an AVL Tree, what is the balance factor constraint for every node x?
Why: An AVL Tree is a height-balanced binary search tree where the height difference between left and right subtrees of any node is at most 1 (i.e. -1, 0, or +1).
Q49. Which Normal Form strictly requires the removal of Transitive Functional Dependencies X → Y where neither X is a super key?
Why: A table is in 3NF if it is in 2NF and no non-prime attribute is transitively dependent on the primary key.
Q50. In transaction processing ACID properties, which property guarantees that committed changes persist even after subsequent system crashes?
Why: Durability guarantees that once a transaction has committed, its updates survive power failures or system crashes via write-ahead logging (WAL).
Q51. In the IPv4 header, if the HLEN (Header Length) field value is 5, what is the actual header length in bytes?
Why: HLEN is represented in 4-bit words (32-bit units). Total bytes = HLEN value × 4 bytes = 5 × 4 = 20 bytes (the standard IPv4 minimum header size).
Q52. Which TCP control flag is transmitted by a client to initiate a 3-Way Connection Handshake?
Why: The 3-way handshake begins with client sending SYN, server replying with SYN-ACK, and client concluding with ACK.
Q53. What is the Maximum Transmission Unit (MTU) payload size for a standard Ethernet frame (IEEE 802.3)?
Why: Standard Ethernet MTU payload is 1500 bytes (excluding Ethernet header and FCS, making the total max frame size 1518 bytes).
Q54. Belady's Anomaly refers to the counter-intuitive phenomenon where increasing physical page frames leads to:
Why: Belady's Anomaly states that in First-In-First-Out (FIFO) page replacement, allocating more memory frames can increase total page faults for certain reference strings.
Q55. What is the core function of a Translation Lookaside Buffer (TLB) in virtual memory hardware?
Why: TLB is a fast associative hardware cache that stores recent virtual-to-physical address mappings, bypassing page table lookups on TLB hits.
Q56. Shortest Remaining Time First (SRTF) is the preemptive version of which CPU scheduling algorithm?
Why: SRTF continuously preempts the currently running process if a new process arrives with a shorter remaining burst time than the current job.
Q57. What does Thomas McCabe's Cyclomatic Complexity metric measure in a control flow graph G with E edges, N nodes, and P connected components?
Why: Cyclomatic complexity V(G) measures code structural complexity. For a single flow graph (P=1), V(G) = E - N + 2, or Predicate Nodes + 1.
Q58. In Agile Software Development (Scrum), what is the main objective of the Sprint Retrospective meeting?
Why: The Sprint Retrospective occurs at the end of a sprint to review what went well, what problems arose, and how the team can improve its workflow.
Q59. In a paging system, page table entry contains valid/invalid bit. What does a '0' (invalid bit) indicate during address translation?
Why: An invalid bit (0) signals that the requested virtual page is either outside the process address space or currently stored on disk, triggering a Page Fault exception.
Q60. What is the Lossless-Join condition when decomposing relation R into R1 and R2 with functional dependencies F?
Why: Decomposition into R1 and R2 is lossless if and only if the common attributes (R1 ∩ R2) functionally determine either R1 or R2.