We proceed by splitting our task in three files.
We define first a header file complex.h which contains the declarations of the class. The header file contains the class declaration (data and functions), declaration of stand-alone functions, and all inlined functions, starting as follows
#ifndef Complex_H
#define Complex_H
// various include statements and definitions
#include <iostream> // Standard ANSI-C++ include files
#include <new>
#include ....
class Complex
{...
definition of variables and their character
};
// declarations of various functions used by the class
...
#endif