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.

201. User level threads are threads that are visible to the programmer and are unknown to the kernel. The operating system kernel supports and manages kernel level threads. Three different types of models relate user and kernel level threads.

Which of the following statements is/are true?
(a) (i) The Many - to - one model maps many user threads to one kernel thread
(ii) The one - to - one model maps one user thread to one kernel thread
(iii) The many - to - many model maps many user threads to smaller or equal kernel threads

(b) (i) Many - to - one model maps many kernel threads to one user thread
(ii) One - to - one model maps one kernel thread to one user thread
(iii) Many - to - many model maps many kernel threads to smaller or equal user threads
a. (a) is true; (b) is false
b. (a) is false; (b) is true
c. Both (a) and (b) are true
d. Both (a) and (b) are false
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Answer: (a).(a) is true; (b) is false

202. Consider a system with five processes P0 through P4 and three resource types A, B and C. Resource type A has seven instances, resource type B has two instances and resource type C has six instances suppose at time T0 we have the following allocation.
If we implement Deadlock detection algorithm we claim that system is ..................
a. Semaphore
b. Deadlock state
c. Circular wait
d. Not in deadlock state
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Answer: (d).Not in deadlock state

203. Consider a disk queue with requests for I/O to blocks on cylinders 98, 183, 37, 122, 14, 124, 65, 67. Suppose SSTF disk scheduling algorithm implemented to meet the requests then the total number of head movements are ................... if the disk head is initially at 53.
a. 224
b. 248
c. 236
d. 240
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Answer: (c).236

204. The Bounded buffer problem is also known as ..................
a. Producer - consumer problem
b. Reader - writer problem
c. Dining Philosophers problem
d. Both (2) and (3)
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Answer: (a).Producer - consumer problem

205. Consider the input/output (I/O) requests made at different instants of time directed at a hypothetical disk having 200 tracks as given in the following table.

Assume that:

Current head position is at track no. 65
Direction of last movement is towards higher numbered tracks
Current clock time is 160 milliseconds
Head movement time per track is 1 millisecond.

“look” is a variant of “SCAN” disk-arm scheduling algorithm. In this algorithm, if no more I/O requests are left in current direction, the disk head reverses its direction. The seek times in Shortest Seek First (SSF) and “look” disk-arm scheduling algorithms respectively are:
a. 144 and 123 milliseconds
b. 143 and 123 milliseconds
c. 149 and 124 milliseconds
d. 256 and 186 milliseconds
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Answer: (b).143 and 123 milliseconds