VMS Help CC, Run-time functions, ungetwc  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Pushes a wide character back into the input stream and leaves the
  stream positioned before the character.

  Syntax:

       #include <wchar.h>

       wint_t ungetwc(wint_t wc, FILE *file_pointer);