Int 21H, AH=44H, AL=0DH

3.2 and higher

GENERIC BLOCK DEVICE REQUEST

AX = 440Dh
BL = drive number (00h=default,01h=A:,etc)
CH = category code (see #01558)
CL = minor code (function) (see #01559)
DS:DX -> (DOS) parameter block (see #01560,#01562,#01563,#01564,#01565)
SI:DI -> (OS/2 comp box) parameter block (see #01566,#01568,#01569,#01572)

 CF set on error
    AX = error code (01h,02h,etc.) (see #01680 at AH=59h/BX=0000h)
CF clear if successful
    DS:DX -> data block if CL=60h or CL=61h

DOS 4.01 seems to ignore the high byte of the number of directory entries in the BPB for diskettes.

functions 46h and 66h undocumented in DOS 4.x, documented for DOS 5+

the DUBLDISK.SYS v2.6 driver only supports minor codes 60h and 67h

DR DOS 3.41-6.0 only support minor codes 40h-42h and 60h-62h; all other minor codes return error code 16h

some PCMCIA calls reportedly appear to be dangerous for MS-DOS versions prior to 5.0

minor code 60h normally produces no I/O except with AutoMount=1 for DBLSPACE/DRVSPACE

AX=440Ch,AX=440Dh/CX=084Ah,AX=440Dh/CX=0871h,AH=69h,INT 2F/AX=0802h, INT 2F/AX=122Bh

Text based on Ralf Brown Interrupt List Release 61