CS and IT GATE 2017 Set-1 Questions with Answer

Ques 53 Mathematics

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Let X be a Gaussian random variable with mean 0 and variance σ². Let Y = max(X,0) where max(a,b) is the maximum of a and b. The median of Y is _____.

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Ques 54 Operating System

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Consider the following CPU processes with arrival times (in milliseconds) and length of CPU bursts (in milliseconds) as given below:

Process	Arrival Time	Brust Time
P1	0	7
P2	3	3
P3	5	5
P4	6	2

If the pre-emptive shortest remaining time first scheduling algorithm is used to schedule the processes, then the average waiting time across all processes is _______ milliseconds.

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Ques 55 Operating System

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Recall that Belady’s anomaly is that the pages-fault rate may increase as the number of allocated frames increases. Now consider the following statements:

Which of the following is CORRECT?

A

S1 is true, S2 is true

B

S1 is true, S2 is false

C

S1 is false , S2 is true

D

S1 is false, S2 is false

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Ques 56 Operating System

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A multithreaded program P executes with x number of threads and uses y number of locks for ensuring mutual exclusion while operating on shared memory locations. All locks in the program are non-reentrant, i.e., if a thread holds a lock l, then it cannot re-acquire lock l without releasing it. If a thread is unable to acquire a lock, it blocks until the lock becomes available. The minimum value of x and the minimum value of y together for which execution of P can result in a deadlock are:

A

x = 1, y = 2

B

x = 2, y = 1

C

x = 2, y = 2

D

x = 1, y = 1

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Ques 57 Operating System

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Threads of a process share

A

global variables but not heap

B

heap but not global variables.

C

neither global variables nor heap.

D

both heap and global variables.

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