what does GetCommState actually do?

So I've just started doing some Win32 programming and I'm confused on the function:

`BOOL BuildCommDCB (LPCTSTR szSettings, LPDCB lpDCB);`

The description of the LPDCB struct states that "it points to the DCB structure in which the control settings information is returned". But my question is how is the DCB structure returned when the return value is a Bool?