Method Overriding in C++

Program 1

// Inheritance in CPP
#include<iostream>
using namespace std;
class Base
{
      public:
      Base(int n)
      {
        cout<<"Constructor of Base class";
      }
     Base(){}
};
class Derived:public Base
{
      public:
      Derived(){}
      Derived(int n):Base(n)
      {
        cout<<"\nConstructor of Dervied class";
      }
};

class Derived1:public Derived
{
      public:
      Derived1(){}
      Derived1(int n):Derived(n)
      {
        cout<<"\nConstructor of Dervied 1 class";
      }
};

int main()
{
    system("cls");
    //Base B;
    Derived1 D(500); 
    return 0;
}

Program 2

// Inheritance in CPP
#include<iostream>
using namespace std;
class MyMath
{
       protected:
       int a,b,c;
       public:
       MyMath()
       {
          a=500;
          b=100;
       }
       void add()
       {
          c=a+b;
          cout<<"addition is : "<<c;
       }
};
class MyMath1:public MyMath
{
    public: 
    MyMath1(){}
    void swap()
    {
           cout<<"\nBefore swaping : "<<a << "  "<<b;
           c=a;
           a=b;
           b=c;
           cout<<"\nAfter swaping : "<<a << "  "<<b;
    }
};
int main()
{
    system("cls");
   MyMath1 M;

    //M.add();
    
    M.swap();
    return 0;
}

Program 3

// Method overriding
#include<iostream>
using namespace std;
class Base
{
    public:
    void show()
    {
        cout<<"\n Show method with zero parameter of base class";
    }
};
class Derived:public Base
{
    public:
   void show()   
    {
        cout<<"\n Show method  of derived class zero paramert ";
    }
};
int main()
{
    system("cls");
    Derived D;
    D.show();
    return 0;
}