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.

It has two operations wait() and signal()

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--;

}

The signal operation increments the value of its argument S.

signal(S)

{

   S++;

}

Using semaphores to solve the producer-consumer problem