data segment
str0 db 0
str1 db 'd:\567.TXT',0
old09h dw 2 dup (0)
data ends
stack segment
sta db 512 dup (0)
stack ends

code segment
assume ds:data,cs:code,ss:stack
ok:
mov ax,data
mov ds,ax
mov ax,stack
mov ss,ax
mov dx,offset str1
mov al,2
mov ah,3dh
int 21h
mov bx,ax

in al,60h
mov str0,al
out 60h,al
mov dx,offset str0
mov cx,1
mov ah,40h
int 21h
mov ah,3eh
int 21h
pushf
call dword ptr old09h
iret

;chushihuabufen
start:
mov ax,data
mov ds,ax
mov dx,offset str1
mov cx,0
mov ah,3ch
int 21h
mov ax,3509h
int 21h
mov old09h,bx
mov old09h+2,es
push cs
pop ds
mov dx,offset ok
mov ax,2509h
int 21h
abc:
mov ah,00h
int 16H
cmp al,0dh
jz over
jmp abc
over:
mov ah,4ch
int 21h
code ends
end start
以上代码错在哪里  找了很久没找到  高手指点
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