I don't know what haphazard reference gave my present haunt OTBD for Doha.
At least the USA has a semblance of sense and I can usually type the ICAO ref from memory.
The haphazard K followed by the airfield name. KDEN = Denver, KJFK = JFK, KCOS = Colorado Springs.
I have no idea where the others for the smaller US fields came from though (any help out there ?) why Meadowlake is 00V I do not know.
DGG