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.

31. A LRU page replacement is used with four page frames and eight pages. How many page faults will occur with the reference string 0172327103 if the four frames are initially empty?
a. 6
b. 7
c. 8
d. 5
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Answer: (b).7

32. Match the following for operating system techniques with the most appropriate advantage :

List – I List – II

(a) Spooling (i) Allows several jobs in memory to improve CPU utilization

(b) Multiprogramming (ii) Access to shared resources among geographically dispersed computers in a transparent way

(c) Time sharing (iii) Overlapping I/O and computations

(d) Distributed computing (iv) Allows many users to share a computer simultaneously by switching processor frequently

Codes:
a b c d
a. (iii) (i) (ii) (iv)
b. (iii) (i) (iv) (ii)
c. (iv) (iii) (ii) (i)
d. (ii) (iii) (iv) (i)
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Answer: (b).(iii) (i) (iv) (ii)

33. Which of the following statements is not true for Multi-Level Feedback Queue processor scheduling algorithm?
a. Queues have different priorities
b. Each queue may have different scheduling algorithm
c. Processes are permanently assigned to a queue
d. This algorithm can be configured to match a specific system under design
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Answer: (c).Processes are permanently assigned to a queue

34. What is the most appropriate function of Memory Management Unit (MMU)?
a. It is an associative memory to store TLB
b. It is a technique of supporting multiprogramming by creating dynamic partitions
c. It is a chip to map virtual address to physical address
d. It is an algorithm to allocate and deallocate main memory to a process
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Answer: (c).It is a chip to map virtual address to physical address

35. In ___________ allocation method for disk block allocation in a file system, insertion and deletion of blocks in a file is easy.
a. Index
b. Linked
c. Contiguous
d. Bit Map
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Answer: (b).Linked

36. Consider a program that consists of 8 pages (from 0 to 7) and we have 4 page frames in the physical memory
for the pages. The page reference string is :
1 2 3 2 5 6 3 4 6 3 7 3 1 5 3 6 3 4 2 4 3 4 5 1
The number of page faults in LRU and optimal page replacement algorithms are respectively (without including initial page faults to fill available page frames with, pages) :
a. 9 and 6
b. 10 and 7
c. 9 and 7
d. 10 and 6
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Answer: (b).10 and 7

37. Which of the following statements is not true about disk-arm scheduling algorithms?
a. SSTF (shortest seek time first) algorithm increases performance of FCFS
b. The number of requests for disk service are not influenced by file allocation method
c. Caching the directories and index blocks in main memory can also help in reducing disk arm movements
d. SCAN and C-SCAN algorithms are less likely to have a starvation problem
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Answer: (b).The number of requests for disk service are not influenced by file allocation method

38. Consider the reference string 0 1 2 3 0 1 4 0 1 2 3 4 If FIFO page replacement algorithm is used, then the number of page faults with three page frames and four page frames are .......... and ........... respectively.
a. 10, 9
b. 9, 9
c. 10, 10
d. 9, 10
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Answer: (d).9, 10

39. Suppose there are four processes in execution with 12 instances of a Resource R in a system. The maximum need of each process and current allocation are given below:
Process Max. Need Current Allocation
P1 8 3
P2 9 4
P3 5 2
P4 3 1

With reference to current allocation, is system safe? If so, what is the safe sequence?
a. No
b. Yes, P1 P2 P3 P4
c. Yes, P4 P3 P1 P2
d. Yes, P2 P1 P3 P4
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Answer: (c).Yes, P4 P3 P1 P2

40. If the Disk head is located initially at track 32, find the number of disk moves required with FCFS scheduling criteria if the disk queue of I/O blocks requests are: 98, 37, 14, 124, 65, 67
a. 320
b. 322
c. 321
d. 319
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Answer: (c).321

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