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

     /NOUNSIGNED_CHAR (D)

  Changes the default for all char types from signed to unsigned.
  This qualifier causes all plain char declarations to have the same
  representation and set of values as signed char declarations.  The
  default is /NOUNSIGNED_CHAR.