几个要点：
具体例子：
include guard：
/*Swmm5Extend.h*/ //if this head file is called before, nothing will be reached #ifndef SWMM5EXTEND_H //this can be everything, but SWMM5EXTEND_H is clear #define SWMM5EXTEND_H /* other head files */ #endif // !SWMM5EXTEND_H
导入其他文件夹内的头文件：
/*in the subdirectory*/ #include "/subdirectory/structure.h" /*in another directory*/ #include "../anotherdirectory/structure.h" //Linke: //https://stackoverflow.com/questions/7581408/including-a-header-file-from-another-directory
原文：https://www.cnblogs.com/kimilin/p/10367132.html