VMS Help FORTRAN, Statements, VOLATILE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Prevents specified variables, arrays, and common blocks from being
  optimized during compilation.  Statement format:

     VOLATILE nlist

     nlist  Is a list of one or more names of variables, arrays,
            or common blocks (enclosed in slashes), separated
            by commas.

  Variables that have been equivalenced (either directly or
  indirectly) are considered volatile if one element in the
  EQUIVALENCE group is declared volatile.

  If array names or common block names are used, the entire array or
  common block becomes volatile.