;编写一四字节压缩型BCD码的减法运算。
;要求完成:buf<--86174563-57261403
data   segment
a1     db 86h,17h,45h,63h
a2     db 57h,26h,14h,03h
buf    db 4 dup(?)
data   ends
code   segment
assume cs:code,ds:data
start: mov ax,data
       mov ds,ax
       mov cx,4
       mov si,3          ;mov si,0
       clc
l1:    mov al,a1[si]     ;mov al,a1[si+3]
       sbb al,a2[si]     ;sbb al,a2[si+3]
       das
       mov buf[si],al    ;mov buf[si+3],al
       dec si
       loop l1
       mov ah,4ch
       int 21h
code   ends
       end start