UGC NET Computer Science 2025 Previous Year Questions (PYQs) – Page 6 of 9
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In a relational database, which one of the following is CORRECT:
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Solution
A prime attribute is one that is part of a candidate key.
In BCNF (Boyce-Codd Normal Form), for every functional dependency $X \to Y$, $X$ must be a super key.
If all attributes are prime, there cannot exist a dependency where a non-superkey determines another attribute.
Hence, the relation is automatically in BCNF.
Match List I with List II
| List I (Hashing Collision Handling Method) | List II (Strategy) |
|---|---|
| A. Chaining | I. Check next slot |
| B. Linear Probing | II. Use second hash function |
| C. Quadratic Probing | III. Linked list at index |
| D. Double Hashing | IV. Skip slots using quadratic step |
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Solution
Chaining → Linked list at index (III)
Linear probing → Check next slot (I)
Quadratic probing → Skip slots using quadratic step (IV)
Double hashing → Use second hash function (II)
Binary equivalent to $(A0F)_{16}$ is:
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Solution
A = 1010,
0 = 0000,
F = 1111
So, $(A0F){16} = 101000001111{2}$.
In a Stop-and-Wait system, the bandwidth of the line is 1 Mbps, and 1 bit takes 30 milliseconds to make a round trip.
The bandwidth-delay product is:
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Solution
Bandwidth-delay product = Bandwidth × Round-trip time
= $1 \times 10^6 \times 30 \times 10^{-3}$
= 30,000 bits.
CB84000D001C001C is the content of a UDP header in hexadecimal format. The source port number is:
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Solution
First 16 bits = Source port = CB84
Convert CB84 to decimal →
= (12 × 4096) + (11 × 256) + (8 × 16) + 4
= 49152 + 2816 + 128 + 4 = 52000.
Identify the correct statement(s) from the following with respect to Spinlock Semaphores:
A. The name refers to busy waiting semaphores.
B. They are not useful when the locks are to be held for a short duration of time.
C. It may require multiple context switches when a process waits on a lock.
D. They are often employed on Uniprocessor systems.
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Solution
Spinlocks are busy waiting locks, meaning the thread repeatedly checks until the lock becomes available — so A is correct.
They are actually useful for short duration locks, since blocking (context switch) is costlier — so B is incorrect.
They do not cause context switches, as the waiting is done actively in CPU — so C is incorrect.
Spinlocks are inefficient on uniprocessor systems, because while one thread spins, the other cannot release the lock — so D is incorrect.
Which of the following is NOT a parent selection technique used in genetic algorithm implementations?
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Solution
Common parent selection methods in Genetic Algorithms include —
Roulette Wheel Selection
Tournament Selection
Rank Selection
Boltzmann Selection
“Radial” is not a valid selection technique.
Arrange the following types of testing in the order they are usually performed in the Software Development Life Cycle (SDLC):
A. Integration testing
B. Unit testing
C. System Testing
D. Acceptance Testing
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Solution
Testing follows this order:
Unit Testing → tests individual components.
Integration Testing → combines modules.
System Testing → tests complete integrated system.
Acceptance Testing → done by client before release.
void main() {
int *i, a = 12, b = 2, c;
c = (a = a + b, b = a / b, a = a * b, b = a - b);
i = &c;
printf("%d", -(*i));
}
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Solution
Step-by-step explanation:
a = 12, b = 2
a = a + b → a = 14
b = a / b → b = 7
a = a * b → a = 98
b = a - b → b = 91
→ c = 91
Hence, -(*i) = -91
Output: 91 (negative of c printed as -(-91) → 91)
Which of the following gates do not give output 1 when both inputs are 0?
A. NAND gate
B. NOR gate
C. XOR gate
D. XNOR gate
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Solution
Step-by-step explanation:
a = 12, b = 2
a = a + b → a = 14
b = a / b → b = 7
a = a * b → a = 98
b = a - b → b = 91
→ c = 91
Hence, -(*i) = -91
Output: 91 (negative of c printed as -(-91) → 91)
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and More.
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