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

3.2 and higher

GENERIC CHARACTER DEVICE REQUEST

AX = 440Ch
BX = device handle
CH = category code (see #01545)
CL = function number (see #01546)
DS:DX -> parameter block (see #01547,#01548,#01549,#01550,#01551,#01552)
SI = parameter to pass to driver (European MS-DOS 4.0, OS/2 comp box)
DI = parameter to pass to driver (European MS-DOS 4.0, OS/2 comp box)

CF set on error
    AX = error code (see #01680 at AH=59h/BX=0000h)
CF clear if successful
    DS:DX -> iteration count if CL=65h
    SI = returned value (European MS-DOS 4.0, OS/2 comp box)
    DI = returned value (European MS-DOS 4.0, OS/2 comp box)

DR DOS 3.41 and 5.0 return error code 16h on CL=45h,65h if the device does not support a retry counter

AX=440Dh,INT 2F/AX=0802h,INT 2F/AX=122Bh,INT 2F/AX=14FFh, INT 2F/AX=1A01h

Text based on Ralf Brown Interrupt List Release 61