What is the use of virtual and override?

Hi Everyone,

I had tried the following programs.

1 st program---------------------------

public class a
{
public void run()
{
console.writeline("hai");
}
}
public class b:a
{
public void run()
{
console.writeline("hello");
}
class c
{
public static void main()
{
b b1 =new b();
b1.run();
a a1=new a();
a1.run();
}
}


2 ND program----------------



public class a
{
public vitual void run()
{
console.writeline("hai");
}
}
public class b:a
{
public override void run()
{
console.writeline("hello");
}
class c
{
public static void main()
{
b b1 =new b();
b1.run();
a a1=new a();
a1.run();
}
}

note:

These two programs print same output means for which i had created object for class ,that method will be called.Then what is the role of Virtual and Override.We already know that override is used it code replacement,but what is the another use in above program...


Thanks,
Maheswar