virtual base conceptual questions

[StGuru]

Hello!

I got few things that I do not understand about virtual bases.

I got this code:

class PoweredDevice
{
public:
    PoweredDevice(int nPower)
    {
		cout << "PoweredDevice: " << nPower << endl;
    }
};

class Scanner: virtual public PoweredDevice
{
public:
    Scanner(int nScanner, int nPower)
        : PoweredDevice(nPower)
    {
		cout << "Scanner: " << nScanner << endl;
    }
};

class Printer: virtual public PoweredDevice
{
public:
    Printer(int nPrinter, int nPower)
        : PoweredDevice(nPower)
    {
		cout << "Printer: " << nPrinter << endl;
    }
};

class Copier: public Scanner, public Printer
{
public:
    Copier(int nScanner, int nPrinter, int nPower)
        : Scanner(nScanner, nPower), Printer(nPrinter, nPower), PoweredDevice(nPower)
    {
    }
};

Now, when you create a Copier class, you will get only one copy of PoweredDevice that will be shared by both Scanner and Printer.

However, this leads to one more problem: if Scanner and Printer share a PoweredDevice base class, who is responsible for creating it? The answer, as it turns out, is Copier. The Copier constructor is responsible for creating PoweredDevice. Consequently, this is one time when Copier is allowed to call a non-immediate-parent constructor directly

Since when the constructor creates objects?

Does the Copier creates the PoweredDevice and how the sharing is done? I do not understand.

Also why virtual bases are created before non-virtual bases?

Why virtual classes are said to run on run-time and not compiling time?

Thanks in advance.

Regards.

P.S Here is link that I read from.