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+13 votes
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Choose the correct alternatives (more than one may be correct) and write the corresponding letters only:

At a particular time of computation, the value of a counting semaphore is $7$. Then $20$ $P$ operations and $15$ $V$ operations were completed on this semaphore. The resulting value of the semaphore is :

  1. $42$
  2. $2$
  3. $7$
  4. $12$

     

asked in Operating System by Veteran (59.5k points)
edited by | 2.7k views
0
Why Semaphore Wait and Signal Operation Denoted by P and V respectively, specially in ISRO Paper.

3 Answers

+23 votes
Best answer

Answer is option B.

Currently semaphore is $7$ so, after $20$ $P$(wait) operation it will come to $-12$ then for $15$ V(signal) operation the value comes to $2.$

answered by (393 points)
edited by
+12 votes

Option B 

since P(S) decreases the counting semaphore value 

 The initial value of semaphore is 7 

After finishing 20 P operations S=-13 (i.e 7-20 =-13)

Now S=-13

V(S) increases the counting semaphore value

After finishing 15 V operations S=-13+15=2

Therefore Answer is 2 option B

answered by Boss (14.2k points)
0
which one is correct?what will be the value after 20 p operations ?

13 or 12 .please answer
+2 votes

 S = 7 - 20 =-13(in suspended list)

S= -13+15 = 2

The resulting value of the semaphore is : 2 option b

suspended list
13
answered by Active (3.7k points)
Answer:

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