Помогите пожалуйста со сдвигами,не могу разобраться.

mov	ah,02
	mov	bh,00
	mov	dh,05
	mov	dl,05
	int	10h

        mov	ah,0ah
	lea	dx,vvod
	int	21h

        call	asciibin
	mov     ax,binv
	mov	d,ax

	mov	ah,02
	mov	bh,00
	mov	dh,06
        mov	dl,06
	int	10h

	mov	ah,0ah
	lea	dx,vvod
	int	21h

	call	asciibin
	mov	ax,binv
	mov	c,ax

        mov	ax,d
	shl	d,cl
	sub     d,1
	sub	ax,c
	mov	b2,ax
	shr	b2,cl
	mov	dx,b2
	xor	ax,ax
	mov	ax,c
	shl	c,cl
	add	c,1
	mov	b4,ax
	add	dx,b4
	mov	ax,dx
	mov	y,ax
	mov	bx,y
	call binascii
        mov	bx,y

asciibin	proc	near
	mov	binv,0
	mov	mul10,1
	mov	cx,0010
	lea	si,numb-1
	xor	bx,bx
	mov	bl,real
b20:	mov	al,[si+bx]
	and	ax,000fh
	mul	mul10
	add	binv,ax
	mov	ax,mul10
	mul	cx
	mov 	mul10,ax
	dec	bx
	jnz	b20
	ret
asciibin	endp

binascii	proc	near
	mov	cx,0010
	lea	si,ascii-1
	mov	bx,c
	mov	ax,binv
c20:	cmp	ax,0010
	jb	c30
	xor	dx,dx
	div	cx
	or	dl,30h
	mov	[si+bx],dl
	dec	bx
	jmp	c20
c30:	or	al,30h
	mov	[si+bx],al
ascii	db	4 dup(?),'$'
	ret
binascii	endp
binv 	dw	0
mul10	dw	1
by	dw	0
k	dw	0
d	dw	0
b	dw	0
i	dw	0
y	dw	0
c	dw	0
b1	dw	0
b2	dw	0
b3	dw	0
b4	dw	0
vvod	label	byte
max	db	4
real	db	?
numb	db	4 dup(' ')
sgcod	ends
	end	begin