assume cs:code,ds:a,es:b,ss:c
a segment
db 1,2,3,4,5,6,7,8
a ends
b segment
db 1,2,3,4,5,6,7,8
b ends
c segment
db 0,0,0,0,0,0,0,0
c ends
code segment
start:mov ax,a
mov ds,ax
mov ax,b
mov es,ax
mov bx,0
mov cx,8
s:mov al,[bx]
add es:[bx],al
push es:[bx]
add bx,1
loop s
mov 4c00h
int 21h
code ends
end start