C++ Primer, Fifth Edition

19.2. Run-Time Type Identification

Run-time type identification (RTTI) is provided through two operators:

• The typeid operator, which returns the type of a given expression

• The dynamic_cast operator, which safely converts a pointer or reference to a base type into a pointer or reference to a derived type

When applied to pointers or references to types that have virtual functions, these operators use the dynamic type (§ 15.2.3, p. 601) of the object to which the pointer or reference is bound.

These operators are useful when we have a derived operation that we want to perform through a pointer or reference to a base-class object and it is not possible to make that operation a virtual function. Ordinarily, we should use virtual functions if ...