ISRO | ISRO CS 2016 | Question 42

At a particular time of computation the value of a counting semaphore is 7. Then 20 P operations and xV operations were completed on this semaphore. If the new value of semaphore is 5 ,x will be
(A) 18
(B) 22
(C) 15
(D) 13


Answer: (A)

Explanation: P operation : Decrements the value of semaphore by 1
V operation : Increments the value of semaphore by 1
Initially, value of semaphore = 7
After 20 P operations, value of semaphore = 7 – 20 = -13
Now, after xV operations, value of semaphore = 5
-13 + xV = 5
xV = 5 + 13 = 18
So, option (A) is correct.

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