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

  Converts the argument, a wide character, to lowercase.  If the
  argument is not an uppercase character, it is returned unchanged.

  Syntax:

       #include <wctype.h>  (ISO C Standard)
       #include <wchar.h>   (XPG4 Standard)

       int towlower(wint_t wc);