;安装4号中断处理程序。中断处理程序在屏幕右下角,打印“attention: of = 1”。
assume cs:code
code segment
start:mov ax,0 ;do4安装程序,安装到安全空间0000:0200处
mov es,ax
mov di,200h
mov ax,cs
mov ds,ax
mov si,offset do4
mov cx,offset do4end-offset do4
cld
rep movsb
mov ax,0 ;将do4在内存中的入口地址保存在4号表项中(中断向量表)
mov es,ax
mov word ptr es:[4*4],200h ;入口地址为二个16位(word型)的数据,分别为ip和cs的值
mov word ptr es:[4*4+2],0
mov ah,4ch
int 21h
do4:jmp short do4start ;do4功能:将定义的字符显示出来
db 'attention:of = 1'
do4start:mov ax,cs
mov ds,ax
mov si,202h
mov ax,0b800h
mov es,ax
mov di,20*160+60*2
mov cx,16
do4s: mov al,[si]
mov es:[di],al
inc si
add di,2
loop do4s
mov ah,4ch
int 21h
do4end:nop
code ends
end start
测试程序:test2.asm
assume cs:code
code segment
start:mov ax,0
add ax,0
mov al,98
add al,99
int 4
mov ah,4ch
int 21h
code ends
end start