/USING_STD
       /USING_STD
       /NOUSING_STD (D)

    Controls whether standard library header files are processed as
    though the compiled code were written as follows:

    using namespace std;
    #include <header>

    These options are provided for compatibility for users who do not
    want to qualify use of each standard library name with std:: or
    put using namespace std; at the top of their sources.

    /USING_STD turns implicit using namespace std on; this is
    the default when compiling /STANDARD=ARM, /STANDARD=GNU,
    /STANDARD=MS, or /STANDARD=RELAXED.

    /NOUSING_STD turns implicit using namespace std off; this is the
    default when compiling /STANDARD=STRICT_ANSI.