Multi-threading : When to use synchronization classes.

The six Multi-threaded classes provided with MFC fall into two categories.

1.     Synchronization objects and 
2.     Synchronization access objects.

1.Synchronization classes are used when access to a resource must be controlled to ensure integrity of the resource.To determine which synchronization class you should use,

• If the application have to wait for something to happen before it can access the resource use "CEvent".
• If more than one thread within the same application access this resource at one time use "CSemaphore".
• Can more than one application use this resource use "CMutex".
• When a synchronization object that allows one thread at a time to access a resource use "CCriticalSection".

2. Synchronization access classes are used to gain access to these controlled resources.

• If your application is concerned with accessing a single controlled resource only use "CSingleLock".
• If your application needs to access to any one of a number of controlled resources use "CMultiLock".

Source:MSDN