subroutine openw(iounit,fname)

c     Open a file for writing, deleting any existing version first.

      implicit none

c input:

c     Fortran I/O unit to use
      integer iounit
c     file name
      character*(*) fname

c local

c     whether the file already exists
      logical exists

c executable

 10   format(a,' ',a)

c     see whether an old file with this name already exists:
      inquire(file=fname,exist=exists,err=990)

c     if yes, delete it
      if(exists)then
         print10,'Deleting old file',fname
         open(iounit,file=fname,status='old',err=990)
         close(iounit,status='delete',err=990)
      endif

c     open the file
      open(iounit,file=fname,status='new',err=990)

      return
 990  print10,'Problem opening file',fname
      stop
      end