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.