When to call virtual

When would I need to call a function virtual? Since derived functions will already override a base class function, when would I need to include virtual? Thanx for ur help. =D

example:

Code:

class A
{
   void Type(void) { cout << "A"; }
}

class B: public A
{
   void Type(void) { cout << "B"; }
}

class C: public B
{
   void Type(void) { cout << "C"; }
}

int main(void)
{
   A a;
   B b;
   C c;

   a.Type(); // prints "A"
   b.Type(); // prints "B"
   c.Type(); // prints "C"

   A* aptr = &a;
   aptr->Type(); // prints "A"

   aptr = &b
   aptr->Type(); // prints "A", should print "B"

   aptr = &c;
   aptr->Type(); // prints "A", should print "C"

   B* bptr = &b;
   bptr->Type(); // prints "B"

   bptr = &c;
   bptr->Type(); // prints "B", should print "C"

   return(0);
}

to make the functions work properly:

Code:

class A
{
   virtual void Type(void) { cout << "A"; }
}

class B: public A
{
   virtual void Type(void) { cout << "B"; }
}

class C: public B
{
   virtual void Type(void) { cout << "C"; }
}

int main(void)
{
   A a;
   B b;
   C c;

   a.Type(); // prints "A"
   b.Type(); // prints "B"
   c.Type(); // prints "C"

   A* aptr = &a;
   aptr->Type(); // prints "A"

   aptr = &b
   aptr->Type(); // prints "B"

   aptr = &c;
   aptr->Type(); // prints "C"

   B* bptr = &b;
   bptr->Type(); // prints "B"

   bptr = &c;
   bptr->Type(); // prints "C"

   return(0);
}

hope this helps!
U.

Thanx. I understand now. I thought that I had read that before but was not sure.