When a Format 4 DISPLAY statement is specified, the value stored in
  arg-position is moved to argument-number. This updates the current
  argument position indicator for the command line. See ARGUMENT-NUMBER
  in the SPECIAL-NAMES paragraph. This point to to selected argument to
  be read by a Format 7 ACCEPT statement.

  Format 4 -

   DISPLAY arg-position UPON argument-number
      [ END-DISPLAY ]