A Binary Semaphore is a synchronization mechanism that can only take two values, 0 and 1. This makes it ideal for managing access to a single resource by ensuring that only one thread can use the resource at a time, effectively providing mutual exclusion. Operations on a binary semaphore simply toggle its state between locked (0) and unlocked (1), much like a mutex.
A Counting Semaphore can hold any non-negative integer value. It is used to control access to a pool of identical resources. Each wait (P) operation decreases the count, indicating a resource has been taken, while each signal (V) operation increases the count, indicating a resource has been released. This allows for flexible management of multiple resources, such as limiting the number of concurrent connections to a server.
Summary Table:
| Aspect | Binary Semaphore | Counting Semaphore |
|---|---|---|
| Values | 0 or 1 | Any non-negative integer |
| Usage | Single resource (mutual exclusion) | Multiple identical resources |
| Operation | Simple toggle between 0 and 1 | Increment/decrement resource count |
Binary semaphores are simpler and focus on mutual exclusion, while counting semaphores provide broader resource management for multiple resources.