where should i not put header files c++ code example

Example 1: what is a header in c++

// my_program.cpp
#include "my_class.h"

using namespace N;

int main()
{
    my_class mc;
    mc.do_something();
    return 0;
}

Example 2: how to include seld declared header file in c++

#include "Employee.h"
//Employee.h should be saved in the same directory.