Int 2F Fn 4A11  - Dblspace.bin - "getdrivemapping" - Get Drive Mapping     [d]

   AX = 4A11h
   BX = 0001h
   DL = drive number (0=A:)

Return: AX = status (see also below)
       0000h successful
       BL = host drive (bit 7 set if specified drive is compressed)
       BH = DoubleSpace sequence number
       other error code (0101h) (see below)

Note:  the compressed volume file for the specified compressed drive is
     host:\DBLSPACE.sequence

See Also: AX=4A11h/BX=0000h

Values for status:
 0000h successful
 0100h bad function
 0101h invalid drive
 0102h not a compressed drive
 0103h drive already swapped
 0104h drive not swapped