写出下面程序的执行结果：

#include<iostream.h>

class A{

private:

    int a,b;

public :

    A( );

    A(int i,int j);

    void print ( );

};

A::A( )

{  a=b=0;  cout<<"Default constructor is called.
";  }

A::A(int i,int j)

{  a=i;    b=j;    cout<<"Constructor is called.
";  }

void A::print ( )

{  cout<<"a="<<a<<","<<"b="<<b<<endl;  }

void main( )

{  Am,n(4,8);  m.print ( );    n.print ( );  }