GATE CS 1992 Q02 — Concurrency and Synchronization

A counting semaphore $S$ is an integer variable that is modified by two standard atomic operations: $P$ (wait) and $V$ (signal).

• $P$ operation: Decrements the semaphore value by $1$ ($S = S - 1$).
• $V$ operation: Increments the semaphore value by $1$ ($S = S + 1$).

Given:

• Initial value of the semaphore, $S_{\text{initial}} = 7$
• Number of $P$ operations = $20$
• Number of $V$ operations = $15$

We can calculate the final value of the semaphore as follows:

Thus, the resulting value of the semaphore is $2$, which corresponds to option B.