ASM

DISK I/O

Get a volume's drive number

I think you actually mean the "working directory reference number" of the folder; it's often incorrectly called a "volume reference number" in the FB documentation. At any rate, either a working dir. reference number or a "true" volume reference number will work in the following:

DIM pb.128
pb.ioCompletion& = _nil
pb.ioNamePtr& = _nil
pb.ioVRefNum% = theRefNum
pb.ioVolIndex% = 0
OSErr = FN HGETVINFO(@pb)
driveNum = pb.ioVDrvInfo%