Because changing a class definition in a header file effectively changes the text of every source file that includes that header, code that uses a class must be recompiled when the class changes.

• 改变头文件中的类定义可有效地改变包含该头文件的每个源文件的程序文本，所以，当类发生改变时，使用该类的代码必须重新编译。