A simple question about "virtual" keyword

[meili100]

class A{
public:
  virtual void foo(){}
};

class B : public A{
public:
  virtual void foo(){}
  // void foo(){}
};

What's the difference between

  virtual void foo(){}

and

  void foo(){}

in a derived class?

I guess they are the same, am I right? That is to say, we don't need to give a "virtual" keyword for overriding?

[laserlight]

No difference other than style. Whether the virtual keyword is omitted or not from the derived class definition, the foo() is still a virtual function.

[Daved]

The only difference is that someone looking only at the derived class interface can tell that foo is virtual if the virtual keyword is there.