in c++ header file code example

Example 1: header file headers

#ifndef HEADER_FILE
#define HEADER_FILE

the entire header file file

#endif

Example 2: what is a header in c++

// my_class.h
#ifndef MY_CLASS_H // include guard
#define MY_CLASS_H

namespace N
{
    class my_class
    {
    public:
        void do_something();
    };
}

#endif /* MY_CLASS_H */