• semaphores are used to limit the simultaneous execution of a code (procedure, line of code, etc.) to one or more threads at a given time. A semaphore can be shared between several applications.
• critical sections are used to limit the simultaneous execution of a code (procedure, line of code, etc.) to one thread at a given time in a single application.

Versions 18 and later

This feature is now available in Windows Store apps mode.

New in version 18

This feature is now available in Windows Store apps mode.

This feature is now available in Windows Store apps mode.

Versions 19 and later

This feature is now available for iPhone/iPad applications.

New in version 19

This feature is now available for iPhone/iPad applications.

This feature is now available for iPhone/iPad applications.

1. Thread #1 runs MutexStart: there is no thread in the mutex.
2. Thread #1 runs the code section protected by the mutex.
3. While thread #1 runs the code protected by the mutex, thread #2 runs MutexStart: since the code protected by the mutex is being run by thread #1, thread #2 must wait for the mutex to be released.
4. Thread #1 runs MutexEnd: no other thread runs the mutex code.
5. Thread #2 can run the code protected by the mutex.
6. The thread n°2 executes the MutexEnd function: no other thread runs the mutex code.

Steps:

1. Creating a mutex with MutexCreate. The mutex is associated with a name.
2. Calling MutexStart before the code section to protect.
3. Calling MutexEnd to define the code section to protect. Lines of code after the MutexEnd function will no longer be protected.
4. Destroying the mutex with MutexDestroy.

Remarks

• The code sections protected by a mutex must be as short as possible and they must only affect the "critical" processes.
• When a thread is pending, the resources of the processor are not used.
• Mutexes apply to both the main thread and the secondary thread s (created with the ThreadExecute function). You must avoid locking the main thread. Indeed, if the main thread is locked (pending), the application cannot be run anymore.
• MutexStart and MutexEnd must be used in the same process (in a procedure for example).
• A mutex can be shared (or not) between the different applications run on the computer. When creating a mutex, specify how it will be shared (MutexCreate).

Functions for managing a mutex

Versions 16 and later MutexCreate New in version 16 MutexCreate MutexCreate	Explicitly creates a mutex.
Versions 16 and later MutexDestroy New in version 16 MutexDestroy MutexDestroy	Explicitly destroys a mutex.
Versions 16 and later MutexEnd New in version 16 MutexEnd MutexEnd	Signals that the thread frees the mutex.
Versions 16 and later MutexStart New in version 16 MutexStart MutexStart	Locks the current thread while waiting for the mutex to be freed.