C++ Specific —>
using [::] nested-name-specifier unqualified-id
using :: unqualified-id
The using declaration introduces a name into the declarative region in which the using declaration appears. The name becomes a synonym for a variable or function declared elsewhere. It allows an individual name from a specific namespace to be used without explicit qualification. This is in contrast to the using directive which allows all the names in a namespace to be used without qualification. See using Directive for related information.
END C++ Specific