Veamos:

#include <iostream>
#include <vector>

class window {
public:
    virtual void draw()
    {
        std::cout << "Window" << std::endl;
    }
};

class button : public window {
public:
    void draw()
    {
        std::cout << "Button" << std::endl;
    }
};

class entry_field : public window {
public:
    // No vamos a definir ninguna funcion draw()
};

class icon : public window {
public:
    void draw()
    {
        std::cout << "Icon" << std::endl;
    }
};

int main(int argc, char* argv[])
{
    std::vector<window*> windows;

    windows.push_back(new button);
    windows.push_back(new entry_field);
    windows.push_back(new icon);

    for (std::vector<window*>::const_iterator i = windows.begin();
        i != windows.end(); i++)
    {
        (*i)->draw();  // POLIMORFISMO: ¿Cual draw() llamamos?
    }

    return(0);
}