SET(SCROLL_BAR)
  Enables a horizontal or vertical scroll bar for the specified window.
  Syntax
     [integer | widget] := SET (SCROLL_BAR, window, {HORIZONTAL | VERTICAL},
                                {ON | OFF})
  Parameters
     integer              The widget instance implementing the vertical or
                          horizontal scroll bar associated with a window.
     widget               The value 0 if an error prevents DECTPU from
                          associating a widget with the window.
     SCROLL_BAR           A keyword directing DECTPU to enable or disable a
                          scroll bar in a DECTPU window.
     window               The window in which the scroll bar does or does
                          not appear.
     HORIZONTAL           A keyword directing DECTPU to enable or disable a
                          horizontal scroll bar.
     VERTICAL             A keyword directing DECTPU to enable or disable a
                          vertical scroll bar.
     ON                   A keyword indicating that the scroll bar is to be
                          visible in the specified window.
     OFF                  A keyword indicating that the scroll bar is not to
                          be visible in the specified window.