difference between semaphor lock and monitor

The signal operation opens a semaphore and if there is a thread already waiting in the queue, that process is allowed to proceed and if there are no threads waiting in the queue the signal is remembered for the next threads.

If the semaphore is closed when the wait operation is called by a thread, the thread is blocked and it has to wait in the queue. When the wait operation is called by a thread, if the semaphore is open, the thread can continue. Each semaphore is associated with a queue of waiting processes. The wait operation blocks a process until the semaphore is open and the signal operation allows another process (thread) to enter. Semaphores mainly support two operations called wait (historically known as P) and signal (historically known as V). Semaphore is a data structure that is used to provide mutual exclusion to critical sections. Monitors use conditional variables to achieve this task. Monitor is a programming language construct that is also used to avoid multiple processes accessing a common resource at the same time therefore guarantees mutual exclusion. Semaphores are used to avoid dead locks and race conditions. Semaphore is a data structure that is used to make sure that multiple processes do not access a common resource or a critical section at the same time, in parallel programming environments.

Difference between semaphor lock and monitor