function overloading

#include<iostream>
#include<conio.h>
class A
{
private:
      int x;
public:
     A()
     {
         x = 0;
         cout << "\n A\'s Def. constructor.";
     }
     A( int a )
     {
         x = a;
         cout<< "\n A\'s para.constructor.";
     }
     void show()
     {
         cout<< "\n x : " << x;
     }
};
class B : public A
{
private:
      int y;
public:
     B() : A()
     {
          y = 0;
          cout<< "\n B\'s Def. constructor.";
     }
     B( int a, int b ) : A(a)
     {
          y = b;
          cout << "\n B\'s para.constructor.";
     }
     void show()
     {
          cout << "\n y : " << y;
     }
};
void main()
{
    cirscr();
    B b1(10, 20);
    b1.show();
    getch();
}