Type the following commands in DrScheme.
; nothing appears to happen ; but behind the scenes ... > (open-graphics) ; viewport appears > (define w (open-viewport "practice" 300 300)) ; line appears > ((draw-line w) (make-posn 30 30) (make-posn 100 100)) ; viewport disappears > (close-viewport w) ; again, nothing appears to happen ; unclosed viewports (if any) would disappear > (close-graphics)