assume cs:code
stack segment
db 128 dup (0)
stack ends
data segment
dw 0,0
data ends
code segment
start: mov ax,stack
mov ss,ax
mov sp,128
mov ax,data
mov ds,ax
mov ax,0
mov es,ax
push es:[0*4]
pop ds:[0]
push es:[9*4+2]
pop ds:[2]
mov word ptr es:[9*4],offset int9
mov es:[9*4+2],cs
mov ax,0b800h
mov es,ax
mov ah,'a'
s: mov es:[160*12+40*2],ah
call delay
inc ah
cmp ah,'z'
jna s
mov ax,0
mov es,ax
push ds:[0]
pop es:[9*4]
push ds:[2]
pop es:[9*4+2] ;恢复原来的INT9中断地址
mov ax,4c00h
int 21h
delay: push ax
push dx
mov dx,1000h
mov ax,0
s1: sub ax,1
sbb dx,0
cmp ax,0
jne s1
cmp dx,0
jne s1
pop dx
pop ax
ret
int9： push ax
push bx
push es
in al,60h
pushf
pushf
pop bx
and bh,11111100b
push bx
popf
call dword ptr ds:[0];对INT指令进行模拟，调用原来的INT9中断例程
cmp al,1
jne int9ret
mov ax,0b800h
mov es,ax
inc byte ptr es:[160*12+40*2+3]
int9ret: pop es
pop bx
pop ax
iret
code ends
end start
代码应该没问题是照书上的写的
但是为什么总是提示找不到
Symbol not defined: INT9
Expected: instruction or directive |
