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

===== Version =====

1 and higher

===== Brief =====

GET ALLOCATION INFORMATION FOR SPECIFIC DRIVE

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

none

===== Input =====

        AH = 1Ch
        DL = drive (00h = default, 01h = A:, etc)

===== 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 =====

  under DOS 1.x, DS:BX points at an actual copy of the FAT; later
          versions return a pointer to a copy of the FAT's ID byte
        on a DBLSPACE drive, the total number of clusters is based on the
          estimated compression ratio
        this function may not be properly supported on CD-ROMs and other
          installable file systems (use AX=4402h"CD-ROM" for CD-ROMs
          instead)
BUG:    DOS 7.10 (Win95B/Win98) reportedly returns incorrect values in AL and
          DX for FAT12/FAT16 drives, even though it manages correct results
          for FAT32 drives (DOS windows are not affected, only real-mode
          DOS)

         
===== See also =====

AH=1Bh,AH=36h

===== Note =====

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

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