Selects the specified display as the current program display.
    This causes the debugger to try to force program input and
    output to that display. Currently, only the PROMPT display can
    be specified.

    If you do not specify a display, the current program display is
    unselected and program input and output are no longer forced to
    the specified display.

    By default, the PROMPT display has the program attribute, except
    on workstations, where the program attribute is unselected.