assume cs:code, es:data
data segment
    a db 1,2,3,4,5,6,7,8
    b dw 0
data ends

code segment

start:	mov ax, data
		mov es, ax
		mov si, 0
		mov cx, 8
	s:	mov al, a[si]
		mov ah, 0
		add b, ax
		inc si
		loop s

		mov ax,4c00h
		int 21h

code ends
end start