Int 21H, AH=1CH

1 and higher

GET DRIVE PARAMETER BLOCK FOR DEFAULT DRIVE

      AH = 1Fh

AL = sectors per cluster (allocation unit), or FFh if invalid drive

      CX = bytes per sector
      DX = total number of clusters
      DS:BX -> media ID byte (see #01356)

this call was undocumented prior to the release of DOS 5.0; however,
        only the DOS 4.0+ version of the DPB has been documented

Format of DOS 1.1 and MS-DOS 1.25 drive parameter block: Offset Size Description (Table 01357) 00h BYTE sequential device ID 01h BYTE logical drive number (0=A:) 02h WORD bytes per sector 04h BYTE highest sector number within a cluster 05h BYTE shift count to convert clusters into sectors 06h WORD starting sector number of first FAT 08h BYTE number of copies of FAT 09h WORD number of directory entries 0Bh WORD number of first data sector 0Dh WORD highest cluster number (number of data clusters + 1) 0Fh BYTE sectors per FAT 10h WORD starting sector of directory 12h WORD address of allocation table Note: the DOS 1.0 table is the same except that the first and last fields

        are missing; see INT 21/AH=32h for the DOS 2+ version
       

SeeAlso: AH=32h,AX=7302h

Text based on Ralf Brown Interrupt List Release 61