Final answer:
A semaphore is a synchronization primitive used to control access to a shared resource. The wait() operation decrements the semaphore value by 1, while the signal() operation increments it. An exception is raised when the semaphore value exceeds the maximum value.
Step-by-step explanation:
In computer science, a semaphore is a synchronization primitive that is used to control access to a shared resource.
A semaphore has a minimum value and a maximum value, typically initialized to 0 and 1 respectively. The semaphore can be accessed using two operations: wait() and signal().
The wait() operation decrements the semaphore value by 1. If the semaphore value becomes negative, it means that the resource is already in use and the wait() operation needs to wait. In this case, an exception is not raised.
On the other hand, the signal() operation increments the semaphore value by 1. If the semaphore value exceeds the maximum value, an exception is raised indicating that the semaphore is in an invalid state.