C++ Primer, Fifth Edition

15.2.2. Defining a Derived Class

A derived class must specify from which class(es) it inherits. It does so in its class derivation list, which is a colon followed by a comma-separated list of names of previously defined classes. Each base class name may be preceded by an optional access specifier, which is one of public, protected, or private.

A derived class must declare each inherited member function it intends to override. Therefore, our Bulk_quote class must include a net_price member:

class Bulk_quote : public Quote { // Bulk_quote inherits from Quote    Bulk_quote() = default;    Bulk_quote(const std::string&, double, std::size_t, double); ...