{{page>en:templates:dosint}}

====== Int 21H, AH=1CH ======

===== Version =====

1 and higher

===== Brief =====

GET DRIVE PARAMETER BLOCK FOR DEFAULT DRIVE

===== Family API =====


===== Input =====

        AH = 1Fh

===== Return =====

 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)

===== Notes =====

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 ^
| 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
         
===== See also =====

SeeAlso: AH=[[en:docs:dos:api:int21:32|32h]],AX=[[en:docs:dos:api:int21:73:02|7302h]]

===== Note =====

Text based on [[http://www.cs.cmu.edu/~ralf/files.html|Ralf Brown Interrupt List Release 61]]

{{page>en:templates:int}}

{{page>en:templates:fapi}}