Question

What is Semaphore?

(a) Grant more than one thread access to a shared resource at the same time

(b) Useful when a collection of resources is being synchronized

(c) Make use of a counter to control access to a shared resource

(d) All of the mentioned

I had been asked this question in an international level competition.

Question is taken from Multithreaded Programming topic in division Reflections, Multithreaded Programming, Collection Classes and Mathematical Functions of C#

Answer 1

Correct answer is (d) All of the mentioned

To explain: A semaphore is similar to a mutex except that it can grant more than one thread access to a shared resource at the same time. Thus, the semaphore is useful when a collection of resources is being synchronized. A semaphore controls access to a shared resource through the use of a counter. If the counter is greater than zero, then access is allowed. If it is zero, access is denied.