Semaphore is a synchronization primitive used in concurrent programming to
control access to a shared resource. Mutual exclusion using semaphores
ensures that only one process or thread can access the shared resource at a
time. Here’s how semaphore mutual exclusion works:
Explanation:
1. **Semaphore Initialization**: Initialize a semaphore with an initial value
of 1. This semaphore acts as a lock for the shared resource.
2. **Acquiring the Semaphore**: When a process wants to access the
shared resource, it must acquire the semaphore. If the semaphore’s
value is greater than 0 (i.e., the resource is available), the process
decrements the semaphore value and proceeds. If the semaphore’s
value is 0 (i.e., the resource is currently being used), the process is
blocked until the semaphore’s value becomes greater than 0.
3. **Releasing the Semaphore**: After a process finishes using the shared
resource, it releases the semaphore by incrementing its value. This
allows other processes waiting for the resource to acquire it.
### Example Code (Using Pthreads and Semaphores in C):
```c
#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
#define NUM_THREADS 5
