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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:[9*4]
pop ds:[0]
push es:[9*4+2]
pop ds:[2] ;将原来的int 9中断例程的入口地址保存在ds:0,ds:2单元中
mov word ptr es:[9*4],offset int9
mov es:[9*4+2],cs ;在中断向量表中设置新的int 9中断例程的入口地址
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]
mov ax,4c00H
int 21H
delay:
push ax
push dx
mov dx,6000H
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
;-----------------------------以下为新的int 9中断例程--------------------------
int9:
push ax
push bx
push es
in al,60H
pushf
call dword ptr ds:[0] ;对int指令进行模拟,调用原来的int 9中断例程
cmp al,1
jne int9ret
mov ax,0B800H
mov es,ax
inc byte ptr es:[160*12+40*2+1] ;将属性值加1,改变颜色
int9ret:
pop es
pop bx
pop ax
iret
code ends
end start