GENERAL: WHAT ARE SEMAPHORES?
What are semaphores and how would I use them?
There are several types of semaphores (the basic idea behind each type is the same):
Semaphores are typically used in one of two ways:
Counting semaphores are used when you might have multiple devices (like 3 printers or multiple memory buffers).
Binary semaphores are used to gain exclusive access to a single resource (like the serial port, a non-reentrant library routine, or a hard disk drive). A counting semaphore that has a maximum value of 1 is equivalent to a binary semaphore (because the semaphore's value can only be 0 or 1).
Mutex semaphores are optimized for use in controlling mutually exclusive access to a resource. There are several implementations of this type of semaphore.
Last Reviewed: Thursday, March 1, 2007
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