An implementation may
define static or non-static class members, or both, as needed to implement the
semantics of the member functions specified in [support]
through [thread] and [depr].
For the sake of exposition,
some subclauses provide representative declarations, and semantic requirements, for
private members of classes that meet the external specifications of the classes.
The declarations for such members are
followed by a comment that ends with exposition only, as in: