Oleg Orlov / Pure virtual functions

#include <iostream>

using namespace std;

enum Codes
{
    Oct = 8,
    Dec = 0xa,
    Hex = 0x10,
};

class Base
{
protected:
    int value;

public:
    void SetValue(int n)
    {
        this->value = n;
        Print();
    }

    virtual void Print(void) = 0;
};

class Hex : public Base
{
public:
    void Print(void)
    {
        cout << hex << this->Base::value << endl;
    }
};

class Oct : public Base
{
public:
    void Print(void)
    {
        cout << oct << this->Base::value << endl;
    }
};

class Dec : public Base
{
public:
    void Print(void)
    {
        cout << dec << this->Base::value << endl;
    }
};

class Numeral : Dec, Oct, Hex
{
public:
    void Call(int num_sys, int value)
    {
        switch(num_sys)
        {
            case Codes::Oct:
                this->Oct::SetValue(value);
                break;
            case Codes::Dec:
                this->Dec::SetValue(value);
                break;
            case Codes::Hex:
                this->Hex::SetValue(value);
                break;
        };
    }
};

void main(void)
{
    Numeral *object = new Numeral();

    object->Call(Codes::Oct, 9);
    object->Call(Codes::Dec, 0xa);
    object->Call(Codes::Hex, 0xf);

    delete object;

    system("pause");
};