本文为《汇编语言程序设计》1503小节例程。点击链接…进课程主页。

任务：在屏幕中间依次显示 ‘a’~’z’ ，并可以让人看清，在显示的过程中，按下Esc键后，改变显示的颜色。
程序：
v0.2

assume cs:code
code segment
start:  mov ax,0b800hmov es,axmov ah,'a's: mov es:[160*12+40*2],ahinc ahcmp ah,'z'jna smov ax,4c00hint 21h
code ends
end start

v0.4

assume cs:code
stack segmentdb 128 dup (0)
stack endscode segment
start:  mov ax,stackmov ss,axmov sp,128; 显示字符mov ax,0b800hmov es,axmov ah,'a's:  mov es:[160*12+40*2],ahcall delayinc ahcmp ah,'z'jna smov ax,4c00hint 21h; 定义延时函数
delay:  push axpush dxmov dx,10hmov ax,0s1:  sub ax,1sbb dx,0cmp ax,0jne s1cmp dx,0jne s1pop dxpop axretcode ends
end start

v1.0

assume cs:codestack segmentdb 128 dup (0)
stack endsdata segmentdw 0,0
data endscode segment
start:  mov ax,stackmov ss,axmov sp,128mov ax,datamov ds,ax; 改中断例程入口地址mov ax,0mov es,axpush es:[9*4]pop ds:[0]push es:[9*4+2]pop ds:[2]mov word ptr es:[9*4],offset int9mov es:[9*4+2],cs; 显示'a'~'z'mov ax,0b800hmov es,axmov ah,'a's:   mov  es:[160*12+40*2],ahcall delayinc ahcmp ah,'z'jna smov ax,0mov es,ax; 恢复原来的地址push ds:[0]pop es:[9*4]push ds;[2]pop es;[9*4+2]mov ax,4c00hint 21h; 定义延迟程序
delay:  push axpush dxmov dx,10hmov ax,0s1:  sub ax,1sbb dx,0cmp ax,0jne s1cmp dx,0jne s1pop dxpop axret; 定义中断例程
int9:   push axpush bxpush esin al,60hpushfpushfpop bxand bh,11111100bpush bxpopfcall dword ptr ds:[0]cmp al,1 ; ESC扫描码1jne int9ret;改变颜色mov ax,0b800hmov es,axinc byte ptr es:[160*12+40*2+1]
int9ret:pop espop bxpop axiretcode ends
end start

注：此程序运行后，键盘功能将失效。程序中潜伏着一个不引人注目的小bug。——先请自行找一找