Final answer:
A semaphore is a shared integer variable used to control access to shared resources in computer science and operating systems.
Step-by-step explanation:
A semaphore is a shared integer variable that can not drop below zero or be more than one.
It is commonly used in computer science and operating systems to control access to shared resources and avoid race conditions.
For example, in a multi-threaded program, multiple threads may try to access a shared resource simultaneously.
By using a semaphore, we can ensure that only one thread can access the resource at a time, preventing conflicts and ensuring data integrity.
When a thread wants to access a resource, it checks the value of the semaphore.
If the semaphore is greater than zero, it decrements the semaphore value and proceeds to access the resource.
If the semaphore is zero, it means the resource is currently in use, so the thread waits until the semaphore value becomes greater than zero.