# 第 17 章：使用 BIOS 进行键盘输入和磁盘读写

## 检测点 17.1

“在 int16h 中断例程中，一定有设置 IF=1 的指令。”这种说法对吗？

答案：**对。**

int 16h 中断的 0 号功能，若缓冲区空，则循环等待，直到缓冲区中有数据。所以缓冲区空的时候，它又会继续检测，也就是可以说返回上一步。 

int 9h 是将按键信息放入缓冲区。 若没有设置 IF=1 的指令，也即 IF=0，则不会处理任何（可屏蔽）中断，当然也就不能屏蔽 int 9 中断，则缓冲区永远不会有数据放入，这将造成 int 16h 的死循环检测。显然不允许这样的事发生，所以一定有设置 IF=1 的指令。


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