What is correct about the following program?

#include<iostream.h> 
class Addition
{
    int x; 
    public: 
    Addition()
    {
        x = 0;
    }       
    Addition(int xx)
    {
        x = xx;
    }
    Addition operator + (int xx = 0)
    {
        Addition objTemp; 
        objTemp.x = x + xx; 
        return(objTemp);
    }
    void Display(void)
    {
        cout<< x << endl;
    }
};
int main()
{
    Addition objA(15), objB;
    objB = objA + 5;
    objB.Display();
    return 0; 
}

#include<iostream.h> 
int main()
{
    float Amount;
    float Calculate(float P = 5.0, int N = 2, float R = 2.0);
    Amount = Calculate(); 
    cout<< Amount << endl; 
    return 0;
}

float Calculate(float P, int N, float R)
{
    int Year = 1;
    float Sum = 1 ;
    Sum = Sum * (1 + P * ++N * R);
    Year =  (int)(Year + Sum);
    return Year; 
}

#include<iostream.h> 
class CuriousTab
{
    int x; 
    public:
    CuriousTab(int xx, float yy)
    {
        cout<< char(yy);
    } 
}; 
int main()
{
    CuriousTab *p = new CuriousTab(35, 99.50f);
    return 0; 
}

#include<iostream.h> 
class CuriousTabTeam
{
    int x, y; 
    public:
    CuriousTabTeam(int xx)
    {
        x = ++xx;
    }
    void Display()
    {
        cout<< --x << " ";
    }
};
int main()
{
    CuriousTabTeam objBT(45);
    objBT.Display();
    int *p = (int*)&objBT;
    *p = 23;
    objBT.Display();
    return 0; 
}