#include <iostream>
 
class BaseClass
{
     public:
     void myFunc()  //Can't be overridden, can be overloaded.
     {
         std::cout << "BaseClass::myFunc() called" << std::endl;
     }
 
     virtual void myVirtualFunc() //Can be overridden, but doesn't have to be.
     {
         std::cout << "BaseClass::myVirtualFunc() called" << std::endl;
     }
 
     virtual void myPureVirtualFunc() = 0; //Must be overridden.
};
 
class DerivedClass : public BaseClass
{
     public:
     void myFunc()
     {
         std::cout << "DerivedClass::myFunc() called" << std::endl;
     }
 
     virtual void myVirtualFunc()
     {
         std::cout << "DerivedClass::myVirtualFunc() called" << std::endl;
     }
 
     virtual void myPureVirtualFunc()
     {
         std::cout << "DerivedClass::myPureVirtualFunc() called" << std::endl;
     }
};
 
int main()
{
    //BaseClass baseClass; //Can't be constructed because of pure-virtual.
    DerivedClass derivedClass;
 
    BaseClass &derivedPretendingToBeBase = derivedClass;
 
    derivedClass.myFunc(); //Calls DerivedClass::myFunc().
    derivedClass.myVirtualFunc(); //Calls DerivedClass::myVirtualFunc().
    derivedClass.myPureVirtualFunc(); //Calls DerivedClass::myPureVirtualFunc().
 
    derivedPretendingToBeBase.myFunc(); //Calls BaseClass::myFunc(), because it's not virtual.
    derivedPretendingToBeBase.myVirtualFunc(); //Calls DerivedClass::myVirtualFunc(), because it IS virtual and overridden.
    derivedPretendingToBeBase.myPureVirtualFunc(); //Calls DerivedClass::myPureVirtualFunc(), because it is virtual and overridden.
 
    return 0;
}

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