VMS Help CC, Messages, COMPLEXNA  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        The complex data types are not supported in this
                language mode.  This will be treated as an identifier
                in this compilation.

 Description    Support for the complex data types is only available
                in certain language modes.  Support is not present
                when the compiler is in VAX C, K & R (common), or
                strict ANSI89 standard modes.  In these language
                modes _Complex and _Complex_I will be treated as
                identifiers.

 User Action    Compile using one of the other compilation modes.