;在A,B和C单元分别存放着三个数。若三个数都不是0,则求出三数之
;和存放在D单元;若其中有一个数为0，则把其它两单元也清零。
data segment
org 1000h
a dw 0ffffh
b dw 0ffffh
c dw 0ffffh
d dw 2 dup(?)
data ends
code segment
assume cs:code,ds:data
start: mov ax,data
       mov ds,ax
       mov ax,a
       mov bx,b
       mov cx,c
       mov si,0
       cmp ax,0
       je j1
       cmp bx,0
       je j1
       cmp cx,0
       je j1
       adc ax,bx
       jnc a1
       inc si
a1:    adc ax,cx
       jnc a2
       inc si
a2:    mov d,ax
       mov d+2,si
       jmp j2
j1:    mov a,0
       mov b,0
       mov c,0
j2:    mov ah,4ch
       int 21h
code   ends
       end start