I can not run this core without following file. How can i do it
#ifndef FLTK_GUARD
#define FLTK_GUARD 1
#include "FL/Fl.H"
#include "FL/Fl_Window.H"
#include "FL/Fl_Button.H"
#include "FL/Fl_Input.H"
#include "FL/Fl_Output.H"
#include // for exit(0)
#include "FL/fl_draw.H"
#include "FL/Enumerations.H"
#include "Fl/Fl_JPEG_Image.H"
#include "Fl/Fl_GIF_Image.H"
#endif