{**********************************************************************}
{ Scroll using arrow keys and quit if Escape is pressed		}
{**********************************************************************}

procedure smooth_vertical;
const
KEY_ESC = $1B;
KEY_UP = 72;
KEY_DOWN = 80;
KEY_ENTER = $0D;
var
y : word;
key : char;
i : integer;
begin
    y := 0;
    key := ReadKey;
    i := integer(key);
    while i <> KEY_ENTER do begin
    	case i of
    	    KEY_UP :   if y > 0 then y := y-1;	{ Scroll up	}
	    KEY_DOWN:  y := y+1;
	end;
	vertical_scroll(y);		{ Scroll down	}
        key := ReadKey;
        i := integer(key);
    end;	
vertical_scroll(0);
end;