说明：  每个 C++/C 程序通常分为两个文件。一个文件用于保存程序的声明（declaration）， 称为头文件。另一个文件用于保存程序的实现（implementation），称为定（definition）文件。
(Each C + + / C program is usually divided into two files. A file is used to hold the declaration of a program, called a header file. Another file is used to hold the implementation of the program, called the definition file.)