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

 Message        The text library module form of #include is an
                extension.

 Description    On OpenVMS systems, an #include directive whose file
                specifier is not enclosed in either quotation marks
                or angle brackets denotes an include from a text
                library.  This is an extension of Compaq C/C++.  This
                directive will not work as expected on non-VMS
                systems.

 User Action    Be aware of this if you wish to port the program.