What is the Difference Between Semaphore and Mutex?

The main difference between a semaphore and a mutex lies in their purpose and implementation. Here are the key differences:

1. Purpose: A mutex is used to provide mutual exclusion, ensuring that only one process or thread can access a shared resource at a time. On the other hand, a semaphore is used to control access to a shared resource with multiple instances, allowing multiple processes or threads to access the resource until a finite instance of the resource becomes available.
2. Locking Mechanism: Mutex uses a locking mechanism, where a process locks the resource, uses it, and then releases it. Semaphores, on the other hand, use a signaling mechanism with wait() and signal() methods to indicate whether a resource is available or not.
3. Object vs. Integer Variable: A mutex is an object, while a semaphore is an integer variable.
4. Functionality: Mutex has no wait() and signal() functions, whereas semaphores do.
5. Ownership: A mutex can be acquired and released by the same process at a time. However, the value of a semaphore variable can be modified by any process that needs the resource.

In summary, a mutex is better suited for situations where a single shared resource needs to be accessed by multiple processes or threads one at a time, while a semaphore is more appropriate for managing access to multiple instances of a shared resource.

Comparative Table: Semaphore vs Mutex

Here is a table comparing the differences between Semaphore and Mutex:

In summary, Semaphores use a signaling mechanism with two atomic operations (Wait and Signal) for process synchronization, while Mutexes use a locking mechanism to provide mutual exclusion.