C++: A Dialog Programming with the C++ Standard Library

The protected Access Specifier

Member variables and member functions that are listed in a protected section of the interface definition are treated as though they were private, with one important exception: member functions of derived classes can access them when they occur as the base class part of a derived class object.

In the current case, we've seen that a DatedStockItem is “just like” a StockItem with one additional member variable and some other additions and changes that aren't relevant here. The important point is that every DatedStockItem contains everything that a StockItem contains. For example, every DatedStockItem has a m_MinimumStock member variable because the StockItem class has a m_MinimumStock member variable, and we're defining ...