Which of the following statements are correct?

#include<iostream.h> 
int main()
{
    int x = 10, y = 20;
    int *ptr = &x;
    int &ref = y;

    *ptr++;
     ref++;    

    cout<< x << " " << y;
    return 0; 
}

#include<iostream.h> 
class CuriousTabBase
{
    public:
    int x, y; 
    public:
    CuriousTabBase(int xx = 0, int yy = 0)
    {
        x = xx;
        y = yy; 
    } 
 };
class CuriousTabDerived : public CuriousTabBase
{
    private:
        CuriousTabBase objBase; 
    public:
    CuriousTabDerived(int xx, int yy) : CuriousTabBase(xx), objBase(yy)
    {
        cout << x          << " " 
             << this->x    << " "  
             << CuriousTabBase::x << " "     
             << this->objBase.x ;
    } 
    ~CuriousTabDerived()
    { }
};
int main()
{
    CuriousTabDerived objDev(11, 22); 
    return 0;
}

#include<iostream.h>
class CuriousTab
{
    int x, y, z; 
    public:
    CuriousTab(int x = 100, int y = 30, int z = 0)
    {
        this->x = x; 
        this->y = y;
        this->z = z; 
        Display();
    }
    void Display()
    {
        cout<< x << " " << y << " " << z;
    }
};
int main()
{
    int a = 0, b = 1, c = 2; 
    int &x = ++a; 
    int &y = --b; 
    int z = c + b - -c; 
    CuriousTab objCuriousTab(x, y, z); 
    return 0; 
}

#include<iostream.h>
#include<string.h>
#include<malloc.h>
class CuriousTabString
{
    char txtName[20]; 
    public:
    CuriousTabString(char *txtTemp = NULL)
    {
        if(txtTemp != NULL)
        strcpy(txtName, txtTemp);
    }
    void Display(void)
    {
        cout<<txtName;
    }
};
int main()
{
    char *txtName = (char*)malloc(10);
    strcpy(txtName, "CuriousTab");
    *txtName = 48;
    CuriousTabString objTemp(txtName);
    cout<< sizeof(txtName);
    return 0; 
}

#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> 
class CuriousTabBase
{
    int x, y; 
    public:
    CuriousTabBase(int xx = 10, int yy = 10)
    {
        x = xx;
        y = yy;
    }
    void Show()
    {
        cout<< x * y << endl;
    }
};
class CuriousTabDerived
{
    private:
        CuriousTabBase objBase; 
    public:
    CuriousTabDerived(int xx, int yy) : objBase(xx, yy)
    {
        objBase.Show();
    }
};
int main()
{
    CuriousTabDerived objDev(10, 20);
    return 0; 
}

#include<iostream.h> 
class Point
{
    int x, y; 
    public:
    Point(int xx = 10, int yy = 20)
    {
        x = xx;
        y = yy; 
    }
    Point operator + (Point objPoint)
    {
        Point objTmp;
        objTmp.x = objPoint.x + this->x; 
        objTmp.y = objPoint.y + this->y;
        return objTmp;
    }
    void Display(void)
    {
        cout<< x << " " << y;
    }
};
int main()
{
    Point objP1;
    Point objP2(1, 2);
    Point objP3 = objP1 + objP2;
    objP3.Display(); 
    return 0; 
}