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

     /COMMENTS={AS_IS | SPACE}
     /COMMENTS=SPACE (D) (ANSI89, RELAXED_ANSI89, and MIA compiler
 modes)
     /NOCOMMENTS (D) (all other compiler modes)

  Governs whether or not comments appear in preprocess output files
  and, if they are to appear, whether they appear themselves or are
  replaced by a single space.  Specify one of the following qualifier
  options:

   AS_IS     Specifies that the comment appears in the output file.

   SPACE     Specifies that a single space replaces the comment in
             the output file.

 NOCOMMENTS specifies that nothing replaces the comment in the output
 file.  This can result in inadvertent token pasting.

 The Compaq C preprocessor might replace a comment at the end of a
 line or on a line by itself with nothing, even if /COMMENTS=SPACE is
 specified.  Doing so does not change the meaning of the program.

 The default is /COMMENTS=SPACE for the ANSI89, RELAXED_ANSI89, and
 MIA compiler modes.  The default is /NOCOMMENTS for all other
 compiler modes.

 Specifying just /COMMENTS defaults to /COMMENTS=AS_IS.