The operation P in a semaphore scheme requires a(n)____ sequence to be performed as an indivisible action in a single machine cycle.
A) test,fetch,increment,and store
B) test,fetch,decrement,and store
C) increment and store
D) decrement and store

Question

Quizplus · Accepted Answer

The P operation in a semaphore scheme requires testing the value of the semaphore, fetching the value, decrementing it by 1, and storing the new value. This sequence must be performed atomically, as an indivisible action in a single machine cycle. Choice B, test, fetch, decrement, and store, is the correct sequence for the P operation. Choice A is incorrect because it includes an increment instead of a decrement. Choices C and D are incorrect because they do not include the necessary test and fetch operations.

The Operation P in a Semaphore Scheme Requires A(n)____ Sequence