Exercice 5 l’héritage en programmation C++

#include <iostream.h>
#include <string>
#include <stdlib.h>
using namespace std;
class date{
protected:
int jour;
int mois;
int annee;
public:
date(int jr=0, int ms=0, int an=0);
void getday();
void getmonth();
void getyear();
void setday();
void setmonth();
void setyear();
virtual string datetostring();
};
class datefr:public date{
public:
datefr(int jr=0, int ms=0, int an=0);
string datetostring();
};
datefr::datefr(int jr, int ms, int an):date(jr,ms,an){}
string datefr::datetostring(){
char tab1[60]="";
char tab2[20]="";
char tab3[20]="";
cout<<"date en version europeenne"<<endl;
itoa(jour,tab1,10);
itoa(mois,tab2,10);
itoa(annee,tab3,10);
strcat(tab1,tab2);
//cout<<tab1<<endl;
strcat(tab1,tab3);
//cout<<tab1<<endl;
return tab1;
}
date::date(int jr, int ms, int an){
jour=jr;
mois=ms;
annee=an;
}
void date::getday(){
cout<<"Jour :"<<jour;
}
void date::getmonth(){
cout<<"Mois :"<<mois;
}
void date::getyear(){
cout<<"Annee :"<<annee<<endl;
}
void date::setday(){
cout<<"Entrer le jour"<<endl;
cin>>jour;
}
void date::setmonth(){
cout<<"Entrer le mois"<<endl;
cin>>mois;
}
void date::setyear(){
cout<<"Entrer l' annee"<<endl;
cin>>annee;
}
string date::datetostring(){
char tab1[60]="";
char tab2[20]="";
char tab3[20]="";
itoa(annee,tab1,10);
itoa(mois,tab2,10);
itoa(jour,tab3,10);
strcat(tab1,tab2);
//cout<<tab1<<endl;
strcat(tab1,tab3);
//cout<<tab1<<endl;
return tab1;
}
void main(){
date a;
a.setday();
a.setmonth();
a.setyear();
a.getday();
a.getmonth();
a.getyear();
string tab= a.datetostring();
for(int i=0;i<20;i++)
cout<<tab[i];
cout<<endl;
datefr b(22,9,81);
string tab1=b.datetostring();
for(int j=0;j<20;j++)
cout<<tab1[j];
cout<<endl;
}