Scope and Initialization of static Data Members

A class’s static data members have class scope. A static data member must be initialized exactly once. Fundamental-type static data members are initialized by default to 0. Prior to C++11, a static const data member of int or enum type could be initialized in its declaration in the class definition and all other static data members had to be defined and intialized at global namespace scope (i.e., outside the body of the class definition). Again, C++11’s in-class initializers also allow you to initialize these variables where they’re declared in the class definition. If a static data member is an object of a class that provides a default constructor, the static data member need not be initialized because its default constructor will be called.