assume cs:code
code segment
;编写中断例程的安装程序
start: mov ax,cs
mov ds,ax
mov si,offset dot
mov ax,0
mov es,ax
mov di,200h
mov cx,offset dotend-offset dot
cld
rep movsb
;设置中断例程的中断向量
mov ax,0
mov es,ax
mov word ptr es:[7ch*4],200h
mov word ptr es:[7ch*4+2],0
mov ax,4c00h
int 21h
;编写中断例程
dot: push bp
mov bp,sp
dec cx
jcxz ok
add [bp+2],bx
ok:
pop bp
iret
dotend:
nop
code ends
end start