stampa c++

#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;

class base{
	protected:
		ofstream out;
		char *str;
	public:
    base(){
			str = new char[10];
			strcpy(str, "prova2");
		}
	virtual void stampa();
};

class derivate: public base{
	private:
		char* str2;
	public:
		derivate():base(){
			str2 = new char[10];
			strcpy(str2, "prova3");
		}
	void stampa();
};

void  base::stampa(){
	  out.open ("esempio.txt",ios::app); //ios::app per non cancellare il contenuto del file
  	  out << str <<endl;
  	  out.close();
}

void  derivate::stampa(){
	  out.open ("esempio.txt",ios::app); //ios::app per non cancellare il contenuto del file
  	  out << str <<" "<<str2<<endl;
  	  out.close();
}

int main () {
	base a;
	a.stampa();
	derivate b;
	b.stampa();
	return 0;
}