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UGC NET · PAPER 2

UGC NET Paper 2 Computer Science – Unit 5: System Software and Operating System PYQ (June 2023)

15 questions · answer key at the end · updated 11 Oct 2026
Q9. Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: I/O protection is ensured by a hardware trap.
Reason R: I/O interrupts are caused by conditions like I/O completion and device malfunction occurring within the I/O devices.
  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is NOT the correct explanation of A
  3. A is true but R is false
  4. A is false but R is true
Answer & explanation →
Q13. Consider the following statements:
S1: The LRU page-replacement algorithm suffers from Belady's anomaly.
S2: Shortest-remaining-time-first scheduling may cause starvation.
S3: The stack is shared by all threads in a process.
  1. S1, S2 and S3 are true
  2. S1, S3 are false and S2 is true
  3. S1, S2 are false and S3 is true
  4. S1, S2 and S3 are false
Answer & explanation →
Q20. Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: A process invokes a library function to create a thread.
Reason R: Threads make system calls to convey their resource and I/O requirements to the kernel.
  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is NOT the correct explanation of A
  3. A is true but R is false
  4. A is false but R is true
Answer & explanation →
Q26. With respect to virtual memory:
Statement I: Address translation is performed for every logical address used during the execution of a program.
Statement II: A program can execute only when all of its components are loaded in memory.
  1. Both Statement I and Statement II are correct
  2. Both Statement I and Statement II are incorrect
  3. Statement I is correct but Statement II is incorrect
  4. Statement I is incorrect but Statement II is correct
Answer & explanation →
Q38. A virtual memory system uses the first-in first-out page replacement policy and allocates a fixed number of frames to a process.
Assertion A: Increasing the number of page frames allocated to a process sometimes increases the page fault rate.
Reason R: Some programs do not exhibit locality of reference.
  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is NOT the correct explanation of A
  3. A is true but R is false
  4. A is false but R is true
Answer & explanation →
Q42. Consider the following arrival and burst times for three processes P0, P1, P2. The pre-emptive shortest job first algorithm is used, and scheduling is carried out only at the arrival or completion of a process. What is the average waiting time for the three processes?
ProcessArrival timeBurst time
P00 ms7
P11 ms3
P22 ms7
  1. 3 ms
  2. 3.67 ms
  3. 4.47 ms
  4. 4 ms
Answer & explanation →
Q46. Match List I with List II
List IList II
A. RAID level 2I. Bit interleaved parity
B. RAID level 4II. Block interleaved distributed parity
C. RAID level 5III. Error correcting parity
D. RAID level 3IV. Block interleaved parity
  1. A-IV, B-III, C-I, D-II
  2. A-III, B-IV, C-II, D-I
  3. A-III, B-I, C-II, D-IV
  4. A-I, B-III, C-IV, D-I
Answer & explanation →
Q54. Match List I with List II
List IList II
A. Critical regionI. Hoare's monitor
B. Wait/signalII. Mutual exclusion
C. Working setIII. Principle of locality
D. DeadlockIV. Circular wait
  1. A-IV, B-I, C-III, D-II
  2. A-II, B-I, C-III, D-IV
  3. A-I, B-II, C-III, D-IV
  4. A-IV, B-III, C-I, D-II
Answer & explanation →
Q58. At a particular time of computation, the value of a counting semaphore is 7. Then 20 P operations and x V operations were completed on this semaphore. If the final value of the semaphore is 5, x will be
  1. 15
  2. 22
  3. 18
  4. 13
Answer & explanation →
Q78. Requests to access cylinders occur in the sequence 4, 34, 10, 7, 19, 73, 2, 15, 6, 20. The head is currently at cylinder 50, and it takes 1 ms to move between adjacent cylinders. What is the time taken to satisfy all requests with the shortest-seek-time-first policy?
  1. 119 ms
  2. 120 ms
  3. 142 ms
  4. 146 ms
Answer & explanation →

Directions (Q91–95): Consider the following program fragment that deals with a table T with 17 rows and 1024 columns, computing an average for each column and printing it (i is the row index and j is the column index):

for j = [0...1023] {
  temp = 0;
  for i = [0...16]
    temp = temp + T[i][j];
  print(temp / 17.0);
}

T[i][j] and temp are 32-bit floating-point values and memory is word addressable. temp is kept in a processor register, so accessing temp does not involve a memory reference. The main memory is paged and holds 16 pages of 1024 words each. The page replacement policy is least recently used (LRU). Unless stated otherwise, T is stored in the virtual address space in row-major format.

Q91. Consider now that T is stored in column-major format. What is the main memory hit ratio?
  1. 80%
  2. 95.6%
  3. 97.8%
  4. 99.9%
Answer & explanation →
Q92. Consider that T is stored in column-major format. How many page faults will be encountered?
  1. 14
  2. 15
  3. 16
  4. 17
Answer & explanation →
Q93. With T stored in row-major format, how many page faults will be encountered?
  1. 16,402
  2. 17,408
  3. 18,208
  4. 18,608
Answer & explanation →
Q94. What is the ratio of page faults for the row-major to the column-major arrangement?
  1. 1024 : 1
  2. 1301 : 1
  3. 1240 : 1
  4. 9107 : 8
Answer & explanation →
Q95. With T stored in row-major format, what is the main memory hit ratio?
  1. 0
  2. 1
  3. 2
  4. 3
Answer & explanation →

Answer key

  1. 9 – D
  2. 13 – B
  3. 20 – B
  4. 26 – C
  5. 38 – B
  6. 42 – B
  7. 46 – B
  8. 54 – B
  9. 58 – C
  10. 78 – A
  11. 91 – D
  12. 92 – D
  13. 93 – B
  14. 94 – A
  15. 95 – A