Lovely article, that brought back memories!
A wee pedantic bit here, to exit the program, it was the school of thought, to use the following instruction - set the exit code to zero and issue terminate.
mov ah, 4ch
mov al, 00h
; Or combine both mov into mov ax, 4c00h
int 21h
mov ah, 4ch mov al, 00h ; Or combine both mov into mov ax, 4c00h int 21h