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

  Controls whether the compiler generates informational diagnostics
  for questionable programming practices which, though allowed, often
  are the result of programming errors.

  The current set of questionable usages that the compiler detects
  are:

   o  A branch into a DO loop or IF block from outside the loop or
      block.  (Note that use of the Fortran 66 "extended range of a
      DO loop" feature will result in a diagnostic.)

   o  Passing an identifier, which had previously been used as an
      intrinsic routine, as an actual argument without naming that
      identifier in an INTRINSIC statement.

   o  Use of the DATE or IDATE intrinsics which may cause problems
      after the year 2000.

   o  Having a COMMON block with the same name as another global
      entity such as a SUBROUTINE, FUNCTION, ENTRY or EXTERNAL.