INT 21 - DOS 2+ - "WRITE" - WRITE TO FILE OR DEVICE
AH = 40h
BX = file handle
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 (05h,06h) (see AH=59h)
Notes:  if CX is zero, no data is written, and the file is truncated or
extended to the current position
data is written beginning at the current file position, and the file
position is updated after a successful write
the usual cause for AX < CX on return is a full disk
BUG:    a write of zero bytes will appear to succeed when it actually failed
if the write is extending the file and there is not enough disk
space for the expanded file (DOS 5.0); one should therefore check
whether the file was in fact extended by seeking to 0 bytes from
the end of the file (INT 21/AX=4202h/CX=0/DX=0)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=3Fh,AH=93h,INT 2F/AX=1109h

See also: 2128

2140 - DOS 2+ - "WRITE" - WRITE TO FILE OR DEVICE