A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

181. Consider the following set of processes and the length of CPU burst time given in milliseconds:

Assume that processes being scheduled with Round-Robin Scheduling Algorithm with time quantum 4 ms. The the waiting time for P4 is .............. ms.
a. 0
b. 4
c. 12
d. 6
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Answer: (c).12

182. Suppose P, Q and R are co-operating processes satisfying Mutual Exclusion condition. Then, if the process Q is executing in its critical section then
a. Both ‘P’ and ‘R’ execute in critical section
b. Neither ‘P’ nor ‘R’ executes in their critical section
c. ‘P’ executes in critical section
d. ‘R’ executes in critical section
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Answer: (b).Neither ‘P’ nor ‘R’ executes in their critical section

183. A process residing in Main Memory and Ready and Waiting for execution, is kept on
a. Execution Queue
b. Job Queue
c. Ready Queue
d. Wait Queue
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Answer: (c).Ready Queue

184. At a particular time of computation, the value of a counting semaphore is 10. Then 12 P operations and “x” V operations were performed on this semaphore. If the final value of semaphore is 7, x will be:
a. 8
b. 9
c. 10
d. 11
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Answer: (b).9

185. In a multi-user operating system, 30 requests are made to use a particular resource per hour, on an average. The probability that no requests are made in 40 minutes, when arrival pattern is a poisson distribution, is ...............
a. e^−15
b. 1−e^−15
c. 1−e^−20
d. e^−20
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Answer: (d).e^−20

186. Normally user programs are prevented from handling I/O directly by I/O instructions in them. For CPUs having explicit I/O instructions, such I/O protection is ensured by having the I/O instructions privileged. In a CPU with memory mapped I/O, there is no explicit I/O instruction. Which one of the following is true for a CPU with memory mapped I/O?
a. I/O protection is ensured by operating system routines.
b. I/O protection is ensured by a hardware trap.
c. I/O protection is ensured during system configuration.
d. I/O protection is not possible.
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Answer: (a). I/O protection is ensured by operating system routines.

187. Which of the following statements are true?

(a) External Fragmentation exists when there is enough total memory space to satisfy a request but the available space is contiguous.
(b) Memory Fragmentation can be internal as well as external.
(c) One solution to external Fragmentation is compaction.
a. (a) and (b) only
b. (a) and (c) only
c. (b) and (c) only
d. (a), (b) and (c)
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Answer: (c).(b) and (c) only

188. Page information in memory is also called as Page Table. The essential contents in each entry of a page table is/are ....................
a. Page Access information
b. Virtual Page number
c. Page Frame number
d. Both virtual page number and Page Frame Number
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Answer: (c).Page Frame number

189. Consider a virtual page reference string 1, 2, 3, 2, 4, 2, 5, 2, 3, 4. Suppose LRU page replacement algorithm is implemented with 3 page frames in main memory. Then the number of page faults are .................
a. 5
b. 7
c. 9
d. 10
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Answer: 2

190. Consider the following three processes with the arrival time and CPU burst time given in milliseconds. The Gantt Chart for preemptive SJF scheduling algorithm is ...............
a. 1
b. 2
c. 3
d. 4
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Answer: (b).2