BLANK = blnk

  blnk  Is a character scalar memory reference that is
        assigned one of the following values:

  'NULL'      If null blank control is in effect for the
              file open for formatted I/O.  (Blanks are
              ignored unless the field is all blanks, in
              which case it is treated as zero.)

  'ZERO'      If zero blank control is in effect.  (All
              blanks other than leading blanks are treated
              as zeros.)

  'UNDEFINED' If the file is not open or if the existing
              file is not open for formatted I/O.