求一个 汇编 的 字符串倒置 程序代码

d:\MASM>type dao.asm
assume  cs:code,ds:data
data    segment
buff    db      256 dup (0)
data    ends
code    segment
start:
        mov ax,data
        mov ds,ax
        mov bx,offset buff
_input:
        mov ah,1
        int 21h
        cmp al,0dh
        jz ok
        mov [bx],al
        inc bx
        jmp _input
ok:
        mov ah,2
        mov dl,0dh
        int 21h
        mov dl,0ah
        int 21h
        mov cx,bx
_output:
        dec bx
        mov ah,2
        mov dl,[bx]
        int 21h
        loop _output


        mov ah,4ch
        int 21h
code    ends
end     start

d:\MASM>