Creates multiple physical cores

49th BCS Written (Special); Subject Code: CSE-971; Exam: 10.10.2025 | প্রশ্ন ও সমাধান

Question 1Networking

A router processes packets @1 Gbps; if 10 packets (1200 bytes each) arrive at once, queuing delay for the 10th packet (in µs) is:

a)96
b)86.4
c)115.2
d)120

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Question 2Networking

OSI ___ Layer establishes, manages & terminates logical connections between applications.

a)Transport
b)Network
c)Session
d)Data link

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Question 3Networking

OSI model Data Link Layer's primary function:

a)Packet routing
b)Error detection & correction
c)end-to-end communication
d)Data encryption

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Question 4Computer Architecture

Hyper-threading:

a)Creates multiple physical cores
b)Allows a single physical core to execute multiple threads simultaneously (correct answer)
c)Reduces cache size
d)Only applied to GPU

Answer and explanation

Correct answer: (b) Allows a single physical core to execute multiple threads simultaneously

Hyper-Threading is Intel's implementation of simultaneous multithreading (SMT). Each physical core keeps two copies of the architectural state (registers, program counter), so the operating system sees two logical processors per core. Both threads share the core's execution units and caches; when one thread stalls, for example waiting on memory, the other can use the idle units. This raises throughput, but it does not double performance, because the hardware resources are shared.

Why the other options are wrong

(a) Creates multiple physical cores: No new hardware cores appear; one physical core is presented as two logical cores.
(c) Reduces cache size: The cache size is unchanged; the two threads simply share the core's existing caches.
(d) Only applied to GPU: Hyper-Threading is a CPU feature (Intel processors); AMD CPUs use the same SMT idea.

Tip: Cores = physical hardware; threads (logical processors) = cores × 2 with Hyper-Threading.

Source: What Is Hyper-Threading? (Intel)

Question 5Digital Logic

The minimum number of NAND gates required to implement an OR gate is:

a)1
b)2
c)3
d)4

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Question 6Digital Logic

A half-adder circuit has:

a)1 input, 2 outputs
b)2 inputs, 2 outputs (correct answer)
c)2 inputs, 1 output
d)3 inputs, 2 outputs

Answer and explanation

Correct answer: (b) 2 inputs, 2 outputs

A half adder adds two 1-bit numbers A and B, so it has 2 inputs. The largest result is 1 + 1 = 10₂ (decimal 2), which needs two bits, so it has 2 outputs: Sum = A ⊕ B and Carry = A·B.

Truth table (A B → Carry Sum): 00 → 0 0, 01 → 0 1, 10 → 0 1, 11 → 1 0.

It is called "half" because it has no carry input, so it can only add the least significant bits.

Why the other options are wrong

(a) 1 input, 2 outputs: With a single input there is nothing to add.
(c) 2 inputs, 1 output: One output cannot show 1 + 1 = 10₂; the carry would be lost.
(d) 3 inputs, 2 outputs: This describes a full adder, which takes a carry-in as its third input.

Tip: Half adder: 2 in, 2 out (no carry-in). Full adder: 3 in, 2 out.

Source: University of Cambridge, Digital Electronics: Combinational Logic, binary adders (slides)

Question 7Database

Reduces redundancy and improves integrity:

a)Indexing
b)Normalization
c)Denormalization
d)Partitioning

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Question 8Database

Which command can we use to save all transactions?

a)savepoint
b)commit
c)save
d)rollback

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Question 9Mathematics

The bisection method is used to:

a)Find the eigenvalue of a matrix
b)Solve a system of linear equation
c)find roots of non-linear equations
d)Perform numerical integration

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Question 10Cloud & Emerging Tech

In machine learning, supervised learning means:

a)training with unlabeled data
b)no training is required
c)training with labeled data
d)Only reinforcement signals are used

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Question 11Programming

What does the 'continue' statement do inside a loop?

a)exits the loop entirely
b)terminates the program
c)re-executes the loop twice
d)skips the rest of the current iteration and moves to the next

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Question 12Computer Architecture

Which register in a CPU points to the next instruction to be executed?

a)Accumulator
b)Flags
c)SP
d)PC

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Question 13Microprocessor

Intel 8085 microprocessor is a ________ bit microprocessor.

a)8
b)16
c)32
d)64

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Question 14Algorithms

Which of the following is not a characteristic of problems suited for Dynamic programming (SP means subproblems)?

a)Overlapping SP
b)Optimal substructure
c)Independent SP
d)Repeated computation of SP

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Question 15Mathematics

The chromatic index of a bipartite graph with at least one edge is:

a)1
b)2
c)3
d)4

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Question 16Algorithms

In Huffman coding, the algorithm repeatedly picks two nodes and merges those. These two nodes are:

a)with the highest frequency
b)with the lowest frequency
c)one highest and one lowest frequency
d)picked arbitrarily

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Question 17Database

A primary key:

a)Can have NULL
b)Uniquely identifies each row (correct answer)
c)Must be a foreign key
d)Can have duplicates

Answer and explanation

Correct answer: (b) Uniquely identifies each row

A primary key is the column (or column set) chosen to identify every row of a table. A PRIMARY KEY is both UNIQUE and NOT NULL (entity integrity; SQLite's documentation notes that the SQL standard requires PRIMARY KEY to imply NOT NULL), and a table can have only one. Run in SQLite on CREATE TABLE t(id TEXT PRIMARY KEY, v TEXT) STRICT:

INSERT INTO t VALUES ('A1', 'x');   -- accepted
INSERT INTO t VALUES ('A1', 'y');   -- UNIQUE constraint failed: t.id
INSERT INTO t VALUES (NULL, 'z');   -- NOT NULL constraint failed: t.id

Why the other options are wrong

(a) Can have NULL: A NULL cannot identify a row, because NULLs cannot be compared, so primary-key columns are NOT NULL in PostgreSQL, Oracle and the SQL standard. (An ordinary SQLite table without STRICT does accept a NULL here; SQLite's own documentation calls this a legacy bug, so it is not the rule.)
(c) Must be a foreign key: The primary key is usually what other tables' foreign keys point to. It may also be a foreign key in special designs (a one-to-one sub-table), but that is optional, never required.
(d) Can have duplicates: The second insert above was rejected for exactly this reason.

Tip: Primary key = UNIQUE + NOT NULL, at most one per table.

Source: PostgreSQL Documentation: 5.5 Constraints
Source: Oracle Database 19c Concepts: Data Integrity
Source: SQLite: CREATE TABLE

Question 18Networking

The address block 192.168.16.0/20 contains ________ IP addresses.

a)1024
b)4096
c)2048
d)65536

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Question 19Algorithms

A* search algorithm is:

a)only complete but not optimal
b)Only optimal but not complete
c)complete and optimal if the heuristic is admissible (correct answer)
d)Neither optimal nor complete

Answer and explanation

Correct answer: (c) complete and optimal if the heuristic is admissible

A* expands the frontier node with the smallest f(n) = g(n) + h(n), where g(n) is the cost so far and h(n) estimates the remaining cost. A heuristic is admissible if it never overestimates: 0 ≤ h(n) ≤ h*(n). Then any node on the optimal path has f ≤ the optimal cost, so A* expands it before it can return a worse goal; the first goal returned is optimal. A* is also complete when the branching factor is finite and every step cost is at least some ε > 0, because f keeps growing until a goal is reached.

Why the other options are wrong

(a) only complete but not optimal: with an admissible heuristic, A* is optimal as well.
(b) Only optimal but not complete: under the same mild conditions (finite branching, positive step costs), A* always finds a solution if one exists.
(d) Neither optimal nor complete: this fits greedy best-first search, which uses h(n) alone, not A*.

Tip: In graph search that never reopens visited states, optimality needs the stronger consistent heuristic: h(n) ≤ c(n, n′) + h(n′). Consistency implies admissibility.

Source: UC Berkeley CS 188 (Fall 2022), Note 2: Informed Search

Question 20Cyber Security

Which of the following protocols is used together with HTTP in HTTPS?

a)SHA
b)SSH
c)TLS
d)VPN

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Question 21Programming

________ is used in C to write a single character to a file.

a)fputs()
b)fprintf()
c)putc()
d)fwrite()

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Question 22Database

"Either all of its operations are executed or none." - this refers to:

a)Consistency
b)Isolation
c)Atomicity
d)Durability

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Question 23Algorithms

________ algorithm is used to find a shortest path in a positive weighted graph.

a)Prim's
b)Kruskal's
c)Dijkstra's
d)DFS

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Question 24Algorithms

Pushdown automata (PDA) is equivalent in power to:

a)regular expressions
b)context-free grammars
c)context-sensitive grammars
d)Turing machines

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Question 25Networking

________ operates at the network layer and is used to connect different networks.

a)Hub
b)Switch
c)Router
d)Repeater

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Question 26Mathematics

________ method is a first order optimization method

a)Newton
b)Quasi-Newton
c)Gradient descent
d)Conjugate gradient

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Question 27Mathematics

Which one below is an iterative method?

a)Gauss elimination
b)Gauss-Seidel
c)Cramer's rule
d)Matrix inversion

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Question 28Programming

In C, to retain the values of variables between function calls, we should use:

a)auto
b)extern
c)static
d)register

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Question 29Software Engineering

Which phase in the compiler design performs data type checking?

a)Lexical analysis
b)Syntax analysis
c)Semantic analysis
d)Code generation

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Question 30Data Structures

For an n-element min-Heap:

a)the smallest element can be found anywhere in the heap
b)It is a type of binary search tree.
c)accessing an arbitrary element is an O(n) operation.
d)the largest element is always at the root.

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Question 31Data Structures

For BFS of a graph, we should use:

a)queue
b)Stack
c)priority queue
d)Binary search tree

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Question 32Software Engineering

Which optimization technique is not used for eliminating redundant code?

a)Dead code elimination
b)Partial redundancy elimination
c)Common subexpression elimination
d)Constant folding

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Question 33Networking

________ layer of the TCP/IP model is responsible for port binding.

a)Application
b)Internet
c)Transport
d)Network

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Question 34Database

Which one below is an example of a NoSQL database?

a)MySQL
b)MongoDB
c)Oracle
d)PostgreSQL

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Question 35Mathematics

A complete graph of n vertices has ________ edges.

a)n
b)n(n+1)/2
c)n(n-1)/2
d)n²

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Question 36Digital Logic

What is the hexadecimal value of (1111011011)₂?

a)3BD
b)3DB
c)3CB
d)3DA

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Question 37Programming

Which one is a compile-time polymorphism?

a)Virtual function
b)Operator overloading
c)Function overriding
d)Dynamic binding

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Question 38Database

Data ________ is the ability to modify a schema definition in a level without affecting the next higher level.

a)binding
b)abstraction
c)mapping
d)independence

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Question 39Operating Systems

________ is a non-preemptive algorithm.

a)FCFS
b)Round Robin
c)Shortest Remaining Time
d)None of the above

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Question 40Digital Logic

The main difference between a latch (L) and a flip-flop (FF) is:

a)FF is level-triggered, L is edge-triggered
b)FF is edge-triggered, L is level-triggered
c)FF cannot store data but L can
d)L can store more data than a FF

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Question 41Database

What is the role of an Index in a database?

a)To store large binary objects
b)To store data integrity constraints
c)To group the related table together
d)To boost the speed of data retrieval operations

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Question 42Database

Which of the following will delete all records from the table with the table structure?

a)ALTER
b)DELETE
c)DROP
d)TRUNCATE

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Question 43Programming

In OOP, ________ is used to restrict access to certain details of an object.

a)Inheritance
b)Polymorphism
c)Abstraction
d)Encapsulation

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Question 44Data Structures

To solve a problem using recursion we should use a:

a)Linked list
b)stack
c)queue
d)array

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Question 45Software Engineering

In Agile, Software is delivered:

a)at the end of the project
b)in small incremental iterations (correct answer)
c)after complete documentation
d)only when all features have been implemented

Answer and explanation

Correct answer: (b) in small incremental iterations

Agile teams build the product in short iterations (sprints) and deliver a working increment at the end of each one. The principles behind the Agile Manifesto put the customer first through early and continuous delivery of valuable software and ask teams to deliver working software frequently, every few weeks to a couple of months, preferring the shorter timescale. Each increment adds features and brings feedback that shapes the next iteration.

Why the other options are wrong

(a) at the end of the project: that is single big-bang delivery, typical of the waterfall model.
(c) after complete documentation: Agile values working software over comprehensive documentation and does not wait for full documents.
(d) only when all features have been implemented: Agile releases usable subsets of features early and adds the rest in later increments.

Tip: Agile = iterative + incremental + frequent delivery + continuous feedback.

Source: Principles behind the Agile Manifesto

Question 46Networking

UDP is a ________ protocol.

a)Connection-less (correct answer)
b)Connection-oriented
c)application layer
d)Network access layer

Answer and explanation

Correct answer: (a) Connection-less

UDP (User Datagram Protocol) is a transport-layer protocol that runs directly on top of IP. A sender simply wraps data in a datagram with source port, destination port, length and checksum, and sends it; there is no handshake beforehand and no connection state afterwards. RFC 768 calls UDP "transaction oriented" and states that delivery and duplicate protection are not guaranteed. Because there is no connection setup, no acknowledgement and no retransmission, UDP has very low overhead, which suits DNS queries, VoIP, live streaming and online games.

Why the other options are wrong

(b) Connection-oriented: That describes TCP, which opens a connection with a three-way handshake and then delivers bytes reliably and in order.
(c) application layer: UDP is not an application protocol; it is a transport-layer service that application protocols such as DNS and TFTP use.
(d) Network access layer: That layer covers framing and physical delivery on a link (e.g. Ethernet). UDP sits two layers higher, above IP.

Tip: TCP = connection-oriented and reliable; UDP = connectionless and best-effort. Both are transport-layer protocols.

Source: RFC 768: User Datagram Protocol

Question 47Mathematics

The number of binary strings of length 5 is:

a)10
b)25
c)32
d)64

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Question 48Programming

Which one is correct to declare & initialize an array in C?

a)int arr(5) = (1,2,3,4,5);
b)int arr[5] = {1,2,3,4,5};
c)int arr() = 1,2,3,4,5;
d)Array arr(5) = {1,2,3,4,5};

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Question 49Mathematics

A relation R on a set B is an equivalence relation if it is:

a)Reflexive and symmetric
b)Reflexive and transitive
c)symmetric and transitive
d)Reflexive, symmetric and transitive

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Question 50Database

________ refers to information about data

a)Hyper data
b)Tera data
c)Meta data
d)Big data

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Question 51Computer Architecture

Which one is not an addressing mode?

a)Immediate
b)Direct
c)Indirect
d)Sequential

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Question 52Data Structures

Using ________ order we can delete tree nodes in such a way that a child node is deleted before its parent

a)Pre
b)Post
c)In
d)Level

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Question 53Computer Architecture

The Principle of Locality in memory systems helps to:

a)reduce CPU clock cycles
b)Improve cache performance
c)increase instruction length
d)Reduce I/O latency

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Question 54Digital Logic

Which of the following is a combinational circuit?

a)Counter
b)Flip-flop
c)Multiplexer
d)Register

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Question 55Algorithms

Which one is true for a DFA?

a)DFA can have ε-transitions
b)DFA accepts all context-free languages
c)DFA accepts regular languages
d)DFA can have multiple transitions for the same input from a state

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Question 56Algorithms

Greedy methods guarantee an optimal solution when:

a)Overlapping subproblems exist
b)problems have optimal substructure and greedy choice property
c)divide and conquer can be applied
d)Subproblems are independent

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Question 57Software Engineering

Adaptive maintenance is required when:

a)errors are found in software
b)user requirements are stable
c)documentation is missing
d)The environment such as OS, hardware changes

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Question 58Software Engineering

What output will be generated by the compiler after lexical and syntax analyses, respectively?

a)Tokens and a parse tree
b)A parse tree and tokens
c)A syntax tree and intermediate code
d)Tokens and error messages

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Question 59Mathematics

Contrapositive of "If it rains, the home team wins":

a)If the home team wins, then it rains
b)If the home team does not win, it does not rain
c)If it does not rain then the home team does not win
d)The home team wins whenever rains

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Question 60Cloud & Emerging Tech

Which one is a supervised learning algorithm?

a)K-means
b)Decision tree
c)Apriori
d)DBSCAN

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Question 61Mathematics

Which of the following is a numerical method for eigenvalue problems?

a)Gauss elimination
b)Power method
c)Newton interpolation
d)Trapezoidal rule

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Question 62Computer Architecture

Direct Memory Access allows:

a)CPU to execute instructions while I/O transfers data directly to memory
b)Only CPU controlled data transfer
c)memory to execute instructions independently
d)Reducing cache hits

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Question 63Operating Systems

________ replaces the page that has not been used for the longest time:

a)MRU
b)LRU
c)FIFO
d)LIFO

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Question 64Computer Architecture

Cache hit rate = 80%; cache access time = 5 ns; memory access time = 50 ns. Then, effective access time (in ns):

a)15 ns
b)45 ns
c)50
d)55

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Question 65Database

Which one is true for a B+ tree?

a)Internal nodes store only actual data
b)Leaf nodes store actual data
c)Does not maintain sorted data
d)Retrieval of data is slower

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Question 66Networking

Which one is false with respect to a VLAN?

a)Provides a logical separation on Layer 2
b)Improves security
c)VLAN tag can distinguish traffic
d)Increases network management complexity

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Question 67Data Structures

Which data structure allows insertion at one end and deletion at the other end?

a)Stack
b)Tree
c)Queue
d)Graph

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Question 68Programming

What is the output of the following C code?

#include<stdio.h>
int main(){
    int arr[5] = {1,2,3,4,5};
    int *p = (arr+2);
    printf("%d", p[-1]);
    return 0;
}

a)2
b)3
c)undefined behaviour
d)Compilation error

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Question 69Operating Systems

In virtual memory, TLB is used to:

a)store instructions
b)control data transfers
c)handle cache misses
d)translate virtual address to physical address quickly

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Question 70Algorithms

____ sort uses a divide and conquer approach.

a)Insertion
b)Quick
c)Bubble
d)Selection

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Question 71Web Technology

________ is used to store web addresses for future use.

a)Routing
b)DNS resolution
c)Caching
d)ARP resolution

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Question 72Operating Systems

Consider 3 processes (P1, P2, P3) and 2 resources (R1, R2). If P1 holds R1 & requests R2, P2 holds R2 & requests R1, what is the minimum number of additional resource units of R1 or R2 needed to resolve the deadlock assuming no preemption?

a)0 unit
b)1 unit of R1 or 1 unit of R2
c)2 units: 1 of R1 & 1 of R2
d)Not enough information

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Question 73Data Structures

In an array-based implementation of a complete binary tree, what is the index of the left child of a node at index i (assuming zero-based indexing)?

a)2i
b)2i+1
c)i+1
d)i-1

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Question 74Algorithms

The space complexity of a recursive algorithm is mainly due to:

a)Input size
b)Output size
c)Variables inside loops
d)Function call stack

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Question 75Networking

____ combines multiple signals over a single medium by assigning different time slots.

a)FDM
b)TDM
c)WDM
d)SDM

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Question 76Networking

During a phone conversation, which mode of communication takes place?

a)Simplex
b)Full-duplex
c)Half-duplex
d)Multiplex

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Question 77Computer Architecture

Garbage collection is required in SSD, because:

a)SSD cells must be erased before being written
b)SSDs cannot store large files
c)SSDs do not support random access
d)it reduces read latency

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Question 78Operating Systems

________ uses disk space as an extension of RAM.

a)Caching
b)Virtual memory
c)Spooling
d)Buffer

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Question 79Mathematics

Newton's backward interpolation formula is the most effective when:

a)Interpolation point is near the beginning
b)Interpolation point is near the end
c)Data points are not equally spaced
d)Function is non-polynomial

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Question 80Software Engineering

____ testing is performed without knowledge of the internal implementation.

a)White box
b)Black box
c)Unit
d)Integration

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Question 81Operating Systems

Which criterion is not mandatory for a solution of critical section problem?

a)Mutual exclusion
b)Bounded waiting
c)Circular Waiting
d)Progress

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Question 82Operating Systems

Interrupt-driven I/O is preferred over polling because it :

a)reduces CPU idle time
b)is slower
c)uses more memory
d)requires fewer devices

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Question 83Mathematics

For a connected acyclic graph with v vertices and e edges we have:

a)v=e
b)v=e+1
c)v=e+2
d)v+1=e

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Question 84Operating Systems

Thrashing in memory management occurs when:

a)Page size is too small
b)CPU utilization is very high
c)The system spends more time swapping pages than executing processes
d)Page table is too large

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Question 85Computer Architecture

A 16-bit address bus can address a maximum of ________ KB memory.

a)16
b)32
c)64
d)128

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Question 86Software Engineering

In Agile, backlog refers to the list of:

a)completed tasks
b)pending bugs
c)features and tasks to be developed
d)rejected requirements

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Question 87Microprocessor

The register SP in a microprocessor:

a)points to the first instruction
b)points to the top of the stack
c)holds the base address of the memory
d)holds the I/O port address

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Question 88Data Structures

A priority queue is best-implemented using a:

a)Stack
b)Linked list
c)array
d)heap

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Question 89Programming

Which loop is an exit-controlled loop?

a)for loop
b)while loop
c)do while loop (correct answer)
d)None of the above

Answer and explanation

Correct answer: (c) do while loop

A loop is called exit-controlled when its condition is checked at the exit point, after the body. In do { body } while (condition); the body runs first and the condition is evaluated after every pass, so the body always runs at least once. A test with a false condition (n = 10, n < 5) confirmed it: the do-while printed one line, the while printed nothing.

Why the other options are wrong

(a) for loop: Entry-controlled; its condition is evaluated before each pass, so it can run zero times.
(b) while loop: Entry-controlled; it also tests before each pass.
(d) None of the above: Wrong, because do-while is exit-controlled.

Tip: Entry-controlled = for, while (test first); exit-controlled = do-while (test last).

Source: do-while loop - cppreference.com; while loop - cppreference.com; for loop - cppreference.com

Question 90Database

Which one is not an ACID property?

a)Authenticity
b)Consistency
c)Isolation
d)Durability

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Question 91Networking

Which protocol is used to send an email over the Internet?

a)FTP
b)SMTP
c)HTTP
d)SNMP

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Question 92Microprocessor

Intel 8086 (16-bit) microprocessor has a ________ bit address bus.

a)8
b)16
c)20
d)32

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Question 93Digital Logic

Which of the following is the simplified version of Boolean function F = Ȳ (X + X̄Y)?

a)X̄.Y
b)X.Ȳ
c)X.Y
d)X̄.Ȳ

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Question 94Networking

Which of the following is a guided transmission medium?

a)Radiowave
b)Microwave
c)Coaxial Cable
d)Infrared

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Question 95Operating Systems

Assuming P1, P2, P3 have burst time (in ms) 6, 8, 3, respectively, which statement is true about SJF?

a)Waiting time of P1 is 3 ms
b)Turn-around time of P3 is 9 ms
c)Waiting time for P2 is 6 ms
d)Turn-around time of P1 is 8 ms

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Question 96Operating Systems

OS system calls perform the following basic operations on files:

a)Read, Write, Delete
b)Write, Print, Reposition
c)Delete, Truncate, Sort data
d)Modify, update, sort data

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Question 97Operating Systems

A page fault occurs when:

a)deadlock happens
b)segmentation starts
c)page is found in memory
d)page is not found in memory (correct answer)

Answer and explanation

Correct answer: (d) page is not found in memory

A page fault is the trap raised when a program touches a virtual page that is not currently present in physical memory (RAM). The OS fault handler then resolves it: for a hard fault it reads the page from the backing store (the paging file or a memory-mapped file), puts it in a free frame (evicting another page if needed), updates the page table and restarts the instruction. Page faults are a normal part of demand paging.

Why the other options are wrong

(a) deadlock happens: deadlock is processes waiting on each other for resources; it has nothing to do with whether a page is resident.
(b) segmentation starts: segmentation is a different memory-management scheme; "starting" it does not raise a page fault.
(c) page is found in memory: that is a hit, the opposite of a fault; no OS intervention is needed.

Tip: Page fault = page not in RAM → OS loads it from disk.

Source: Working Set - Win32 apps | Microsoft Learn

Question 98Algorithms

Alpha-Beta pruning can:

a)change the final minimax result
b)Only reduces the number of nodes evaluated
c)increase the depth of the tree
d)Increase the branching factor

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