/sys$common/syshlp/helplib.hlb CC, Messages, READONLYEXT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        readonly is a language extension.

 Description    The readonly storage class modifier is a language
                extension of Compaq C.  Other C compilers might not
                successfully compile a program that uses the
                extension.

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