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Two atomic operations permissible on Semaphores are __________ and __________.

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UGC NET Computer Science (Paper 2) Nov 2017 Official Paper
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  1. wait, stop
  2. wait, hold
  3. hold, signal
  4. wait, signal

Answer (Detailed Solution Below)

Option 4 : wait, signal
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Semaphores are integer variables that are used to solve the critical section problem by using two atomic operations, wait and signal that are used for process synchronization.

Wait:

The wait operation decrements the value of its argument S if it is positive. If S is negative or zero, then no operation is performed.

wait(S)

{  

    while (S<=0)

     S--;

}

Signal:

The signal operation increments the value of its argument S.

signal(S)

{

    S++;

}

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