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.

41. A scheduling Algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (lowest priority). The scheduler re-evaluates the process priority for every 'T' time units and decides next process to be scheduled. If the process have no I/O operations and all arrive at time zero, then the scheduler implements .............. criteria.
a. Priority scheduling
b. Round Robin Scheduling
c. Shortest Job First
d. FCFS
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Answer: (b).Round Robin Scheduling

42. There are three processes P1, P2 and P3 sharing a semaphore for synchronising a variable. Initial value of semaphore is one. Assume that negative value of semaphore tells us how many processes are waiting in queue. Processes access the semaphore in following order:

(a) P2 needs to access
(b) P1 needs to access
(c) P3 needs to access
(d) P2 exits critical section
(e) Pi exits critical section

The final value of semaphore will be:
a. 0
b. 1
c. -1
d. -2
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Answer: (a).0

43. In a paging system, it takes 30 ns to search translation Look-aside Buffer (TLB) and 90 ns to access the main memory. If the TLB hit ratio is 70%, the effective memory access time is:
a. 48 ns
b. 147 ns
c. 120 ns
d. 84 ns
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Answer: (b).147 ns

44. Match the following w.r.t. Input/Output management:

List-l List-II
a. Device controller i. Extracts information from the controller register and store it in data buffer
b. Device driver ii. I/O scheduling
c. Interrupt handler iii. Performs data transfer
d. Kernel I/O subsystem iv. Processing of I/O request

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

45. Which of the following scheduling algorithms may cause starvation?
a. First-come-first-served
b. Round Robin
c. Priority
d. Shortest process next
e. Shortest remaining time first
a. a, c and e
b. c, d and e
c. b, d and e
d. b, c and d
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Answer: (b).c, d and e

46. Distributed operating systems consist of:
a. Loosely coupled O.S. software on a loosely coupled hardware
b. Loosely coupled O.S. software on a tightly coupled hardware
c. Tightly coupled O.S. software on a loosely coupled hardware
d. Tightly coupled O.S. software on a tightly coupled hardware
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Answer: (a).Loosely coupled O.S. software on a loosely coupled hardware

47. Which of the following is incorrect for virtual memory
a. Large programs can be written
b. More I/O is required
c. More addressable memory available
d. Faster and easy swapping of process
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Answer: (b).More I/O is required

48. Consider following schedules involving two transactions:

S1: r1(X); r1(Y); r2(X); r2(Y); w2(Y); w1(X)
S2: r1(X); r2(X); r2(Y); w2(Y); r1(Y); w1(X)

Which of the following statement is true?
a. Both S1 and S2 are conflict serializable
b. S1 is conflict serializable and S2 is not conflict serializable
c. S1 is not conflict serializable and S2 is conflict serializable
d. Both S1 and S2 are not conflict serializable
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Answer: (c).S1 is not conflict serializable and S2 is conflict serializable

49. A memory management system has 64 pages with 512 bytes page size. Physical memory consists of 32 page frames. Number of bits required in logical and physical address are respectively:
a. 14 and 15
b. 14 and 29
c. 15 and 14
d. 16 and 32
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Answer: (c).15 and 14

50. Consider a disk queue with I/O requests on the following cylinders in their arriving order:

6,10,12,54,97,73,128,15,44,110,34,45

The disk head is assumed to be at cylinder 23 and moving in the direction of decreasing number of cylinders. Total number of cylinders in the disk is 150. The disk head movement using SCAN-scheduling algorithm is:
a. 172
b. 173
c. 227
d. 228
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Answer: (b).173

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