[bits 16]
reset equ 0
writes equ 9
dos equ 0x21
tlength equ 0x80
ctail equ 0x81
org 0x100
section .text
;; get address of end of command tail
mov bl,[tlength] ;move value at 0x80 into low byte
mov bh,0 ;move zero into high byte
add bx,ctail ;add 0x81
;; add '$' to command tail
mov byte [bx],'$' ;write byte '$' to address determined
;; output command tail
mov dx,ctail
mov ah,writes
int dos
;; quit program
mov ah,reset
int dos