.model tiny
.code
org 100h
s:
	mov	ax,5802h
	int	21h
	jc	no_umb
	mov	ax,5803h
	mov	bx,1
	int	21h
	jc	no_umb		
	mov	ax,5803h
	mov	bx,0
	int	21h
	mov	ax,4c00h
	int	21h
no_umb:	mov	ax,4c01h
	int	21h
end s