因为它是一个全球性的功能，你可以在任何地方使用它的程序，只需包含头文件和执行文件添加到项目。

Because it is a global function, you can use it anywhere in the program, just include the header file and add the implementation file to the project.

youdao

在理想情况下，头文件应该包含所有类定义、成员函数和变量。

This header file should ideally contain all the class definitions, member functions, and variables.

youdao

这个头文件包含共用的定义和过程。

This header file contains common definitions and procedures.

youdao