This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
Subclasses can access protected members by inheritance. So an instance of the subclass can access it's own protected member from the superclass, but it can't access the same member on a different object. Your example neatly demonstrates exactly what this means - line 27 compiles but line 24 doesn't.