Access base class's virtual if derived class does not redefine it : virtual function « Class « C++ Tutorial

1. C++ Tutorial
2. Class
3. virtual function

#include <iostream> 
using namespace std; 
 
class BaseClass { 
public: 
  virtual void who() { 
    cout << "Base\n"; 
  } 
}; 
 
class DerivedClass1 : public BaseClass { 
public: 
  void who() { 
    cout << "First derivation\n"; 
  } 
}; 
 
class DerivedClass2 : public BaseClass { 
// who() not defined 
}; 
 
int main() 
{ 
  BaseClass base_obj; 
  BaseClass *p; 
  DerivedClass1 DerivedClass1_obj; 
  DerivedClass2 DerivedClass2_obj; 
 
  p = &base_obj; 
  p->who();  // access BaseClass's who() 
 
  p = &DerivedClass1_obj; 
  p->who(); // access DerivedClass1's who() 
 
  p = &DerivedClass2_obj; 
  p->who(); /* access BaseClass's who() because 
               DerivedClass2 does not redefine it */ 
 
  return 0; 
}

Base
First derivation
Base