INT 16 - KEYBOARD - KBUF extensions - ADD KEY TO TAIL OF KEYBOARD BUFFER
AH = FFh
DX = scan code
Return: AL = status
00h success
01h failure
Note:   KBUF is a keyboard buffer expander by Mark Adler

See also: 1605

16FF - KEYBOARD - KBUF extensions - ADD KEY TO TAIL OF KEYBOARD BUFFER