This currency coverter in c++ doesn't work - c++

Question

problem: the cout is always strange numbers or the else cout or the cout that say "useless conversion"
. I've tried also using integers and strings instead of letters for the currencies but doesn't work anyway
I've done in Object oriented programming for necessity
#include<iostream>
using namespace std;
/*Object oriented programming*/
class Convertitore{
public:
char vEntrata, vUscita;
double qEntrata;
Convertitore();
Convertitore(char vEntrata, char vUscita, double qEntrata);
double Calcolo();
};
Convertitore::Convertitore(){
vEntrata = 'a';
vUscita = 'a';
qEntrata = 0;
}
Convertitore::Convertitore(char vEntrata, char vUscita, double qEntrata){
vEntrata = vEntrata;
vUscita = vUscita;
qEntrata = qEntrata;
}
double Convertitore::Calcolo(){
if(vEntrata == 'e' && vUscita == 'e'){
cout << "Useless conversion";
}
else if(vEntrata == 'e' && vUscita == 'd'){
cout << qEntrata << "€ equal to " << qEntrata*1.22 << "$";
}
else if(vEntrata == 'e' && vUscita == 'l'){
cout << qEntrata << "€ equal to " << qEntrata*1936 << "£";
}
else if(vEntrata == 'd' && vUscita == 'e'){
cout << qEntrata << "$ equal to " << qEntrata/1.22 << "€";
}
else if(vEntrata == 'd' && vUscita == 'd'){
cout << "Useless conversion";
}
else if(vEntrata == 'd' && vUscita == 'l'){
cout << qEntrata << "$ equal to " << qEntrata*1510.29 << "£";
}
else if(vEntrata == 'l' && vUscita == 'e'){
cout << qEntrata << "£ equal to " << qEntrata/1936.27 << "€";
}
else if(vEntrata == 'l' && vUscita == 'd'){
cout << qEntrata << "£ equal to " << qEntrata/1510.29 << "$";
}
else if(vEntrata == 'l' && vUscita == 'l'){
cout << "Useless conversion";
}
else{
cout << "wrong inputs";
}
}
int main(){
char vEntrata, vUscita;
double qEntrata;
cout << "Scegli la valuta da convertire: digita e per euro, d per dollar, l per italian lira: "; cin >>
vEntrata;
cout << "Scegli la valuta in cui convertire: digita e per euro, d per dollar, l per italian lira: "; cin
>> vUscita;
cout << "digitare la quantità di " << vEntrata << " da convertire: "; cin >> qEntrata;
Convertitore Valuta = Convertitore(vEntrata, vUscita, qEntrata);
cout << Valuta.Calcolo();
return 0;
}

Answer 1

In your constructor
Convertitore::Convertitore(char vEntrata, char vUscita, double qEntrata){
vEntrata = vEntrata;
vUscita = vUscita;
qEntrata = qEntrata;
}
You are assigning local variables to themselves.
You can use the member initializer list instead:
Convertitore::Convertitore(char vEntrata, char vUscita, double qEntrata)
: vEntrata(vEntrata),
vUscita(vUscita),
qEntrata(qEntrata)
{}
Secondly your function double Convertitore::Calcolo() promises to return a double, but doesn't return anything.
Because of this the line
cout << Valuta.Calcolo();
causes undefined behaviour and most likely will print garbage data.
It seems like Calcolo isn't designed to return something, but print the result directly. If that's what you want, change the return type to void:
void Convertitore::Calcolo()
and don't attempt to print the (now non-existent) return value.