This function both decrements the value of the specified 32-bit variable and checks the resulting value. InterlockedDecrement prevents more than one thread from using the InterlockedDecrement function or InterlockedIncrement function to access the same variable simultaneously.
The functions InterlockedDecrement, InterlockedCompareExchange, InterlockedExchange, InterlockedExchangeAdd, and InterlockedIncrement provide a simple mechanism for synchronizing access to a variable that is shared by multiple threads. The threads of different processes can use this mechanism, if the variable is in shared memory.
The variable pointed to by the lpAddend parameter must be aligned on a 32-bit boundary.