Indicates the position of a file connected for sequential access.
  It takes the following form:

  POSITION = pos

  pos   Is a character expression with one of the
        following values:

  'ASIS'   Indicates the file position is unchanged if the file
           exists and is already connected.  The position is
           unspecified if the file exists but is not connected.
           This is the default.

  'REWIND' Indicates the file is positioned at its initial point.

  'APPEND' Indicates the file is positioned at its terminal point
           (or before its end-of-file record, if any).)

  A new file (whether specified as new explicitly or by default) is
  always positioned at its initial point.