Minimal example of a shape interface and extending it to create a basic square object.

shape.cpp

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#include <iostream>

using namespace std;


struct IShape
{
    virtual ~IShape() {};
    virtual void setWidth(int width) const = 0;
    virtual void setHeight(int height) const = 0;
    virtual void setX(int x) const = 0;
    virtual void setY(int y) const = 0;
    virtual int getX() const=0;
    virtual int getY() const=0;
    virtual int getWidth() const=0;
    virtual int getHeight() const=0;
};


struct Square : public IShape
{
    Square(): m_x(0),m_y(0),m_width(100),m_height(100){};
    Square(int x,int y,int width,int height){};
    virtual void setWidth(int width)const{};
    virtual void setHeight(int height) const{};
    virtual void setX(int x) const{};
    virtual void setY(int y) const{};
    virtual int getX() const{return m_x;};
    virtual int getY() const{return m_y;};
    virtual int getWidth() const{return m_width;};
    virtual int getHeight() const{return m_height;};
    private:
    int m_width;
    int m_height;
    int m_x;
    int m_y;
};

int main()
{
    Square sq;
    cout<< "X:"<<sq.getX()<<" y:"<<sq.getY()<<" Width:"<<sq.getWidth()<<" Height:"<<sq.getHeight();

    return 0;
}