C++ visual function / C++ visualna funkcja

This is visual function
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#include <iostream>
using namespace std;
class A
{
public:
    virtual void read()
    {
    cout << "This is A" << endl;
    }
private:

};
class B:public A
{
public:
     void read()
    {
    cout << "This is B" << endl;
    }
private:

};
class C:public A
{
public:
     void read()
    {
    cout << "This is C" << endl;
    }
private:
};

int main()
{
//standard use
A o1;
o1.read();
B o2;
o2.read();
C o3;
o3.read();
//Vitualization
cout << "Virtual" << endl;
A *wsk=&o1;
wsk->read();
wsk=&o2;
wsk->read();
wsk=&o3;
wsk->read();
return 0;
}