Which of the following is used to make an abstract class?

#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; 
}