What does & in front of a function argument mean?

[Zyprexa]

Hi

I have this function:
EventGetUserId(Event, &userID);

userID is an (unsigned int) variable, but what does the & in front of it mean/do?

[Bazzy]

It returns the memory address of userID
see http://www.cplusplus.com/doc/tutorial/pointers/

[kbw]

It means, pass the address of userID rather than pass its value. We call this pass by reference. It allows EventGetUserId to change the value of userID.

[Zyprexa]

Thanks