using System;
using System.Windows.Forms;

class A
{ private int x;
　public A( ) { x = 0; }
　public A( int i ) { x = i; }
};

class B : A
{ private int y;
　public B( ) { y = 0; }
　public B( int i ) { y = i; }
　public B( int i, int j ):A(i) { y = j; }
};

b1 = new B();
b2 = new B(1);
b3 = new B(0,1);

output+=b1;
output+=b2;
output+=b3;


帮解释一下什么意思
语句意思不懂
我不懂才要运行
可是运行不出来..........