AH=40H - 8086 INT 21H

AH=40h - "WRITE" - WRITE TO FILE OR DEVICE
Entry:
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)
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

Syntax

MOV AH,40H
INT 21H

Example

MOV AH,40H
INT 21H

Output / Return Value

Return:
    CF clear if successful -AX = number of bytes actually written
    CF set on error - AX = error code (05h,06h)

Limitations

Alternatives / See Also

Reference