We can use binary semaphores to deal with the critical-section problem for multiple processes.Semaphores can be used to solve various synchronization problems and can be implemented efficiently, especially if hardware support for atomic operations is available.

A semaphore S is an integer variable that,apart from initialization,is accessed only through two standard atomic operations:wait() and signal().The wait() operation was originally termed P;signal() was originally called V.All the modifications to the integer value of the semaphore in the wait() and signal() operations must be executed indivisibly.That is,when one process modifies the semaphore value,no other process can simultaneously modify that same semaphore value.In addition,in the case of wait(S),the testing of the integer value of S(S<=0),and its possible modification(S--),must also be executed without interruption.