In computer science, a semaphore is a variable or abstract data type used to control access to a common resource by multiple processes and avoid critical section problems in a concurrent system such as a multitasking operating system.

What is the purpose of semaphores?

A semaphore is an integer variable, shared among multiple processes. The main aim of using a semaphore is process synchronization and access control for a common resource in a concurrent environment. The initial value of a semaphore depends on the problem at hand.

What is a semaphore and why would you use one?

Semaphore is simply a variable that is non-negative and shared between threads. This variable is used to solve the critical section problem and to achieve process synchronization in the multiprocessing environment. Semaphores are of two types: Binary Semaphore – This is also known as mutex lock.