Illegal operation (ERR=141)

  The program attempts to do one of the following:

   o  Delete a record in a sequential file
   o  Update a record on a magtape file
   o  Transpose a matrix, or perform a matrix multiplication,  with  the
      same array as source and destination
   o  Rewind a process-permanent file
   o  Delete a record in a read-only file
   o  Assign a value to a virtual array element in a read-only file
   o  Perform a MARGIN operation on VIRTUAL file
   o  Perform an invalid operation on a VIRTUAL file, for example, using
      GET  and  PUT  on  a  VIRTUAL file, then attempting to reference a
      virtual array dimensioned on that file.

  Change the illegal operation.