Int 21H, AH=44H, AL=05H

2 and higher

WRITE TO BLOCK DEVICE CONTROL CHANNEL

AX = 4405h
BL = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> data to write

Return: CF clear if successful

    AX = number of bytes actually written
CF set on error
    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)

format of data is driver-specific

this function was not supported by Digital Research's DOS Plus

AX=4403h,AX=4404h,INT 2F/AX=122Bh

Text based on Ralf Brown Interrupt List Release 61