SUB ENTIRE_SCREEN

	!+
	!   This Subroutine will modify the VIEWPORT, DEVICE VIEWPORT,
	!   and DEVICE WINDOW so that the World Coordinate WINDOW
	!   selected will be mapped to the entire terminal screen.
	!   
	!   This is accomplished by mapping the selected WC Window
	!   onto a portion of NDC space that is proportional to the 
	!   device, and then mapping that same portion of NDC space 
	!   to the entire device.
	!-

	OPTION TYPE = EXPLICIT

	DECLARE SINGLE DC_XMAX, DC_YMAX, ASPECT_RATIO
	ASK DEVICE SIZE DC_XMAX, DC_YMAX

	ASPECT_RATIO = DC_YMAX / DC_XMAX
	SET VIEWPORT 0,1,0,ASPECT_RATIO
	SET DEVICE WINDOW 0,1,0,ASPECT_RATIO
	SET DEVICE VIEWPORT 0,DC_XMAX, 0,DC_YMAX

    END SUB