NUMBER:  31

  ERROR CODE:  F

  MESSAGE TEXT:  mixed file access modes

  EXPLANATION:  One of the following conditions occurred:

   o  An attempt was made to use both formatted and unformatted
      operations on the same unit.

   o  An attempt was made to use an invalid combination of access
      modes on a unit, such as direct and sequential.  The only valid
      combination is sequential and keyed access on a unit opened
      with ACCESS='KEYED'.

   o  An attempt was made to execute a Fortran I/O statement on a
      logical unit that was opened by a program coded in a language
      other than Fortran.