enum 枚举常量谁帮我讲一下我看书上的讲的不太详细

#include <iostream>

using namespace std;



enum ERR_CODE { SUCCESS, ERROR };



ERR_CODE Factor(int, int&, int&);



int main ()

{

        int number, squared,cubed;

        ERR_CODE result;

        

        cout << "Enter a number (0 - 20):"

        cin >> number;

        

        result = Factor (number,squared,cubed);



        if (result == SUCCESS)

        {

           cout << "number: " << number << endl;

           cout << "squared: " << squared << endl;

           cout << "cubed: " << cubed << endl;

        }

        else

           cout << "Error encountered!! " << endl;

        return 0;

        

}

        ERR_CODE Factor(int, int&rSquared, int&rCubed)

{

        if (n > 20)

           return ERROR;

        else

        {

        rSquared = n*n;

        rCubed = n*n*n;

        return SUCCESS;

        }

}