Two functions are associated with drawing filled ellipses: areacircle()
and areaellipse(). areacircle()  (a macro that calls areaellipse()) will
draw a circle from the specified center point using the specified radius.
This function is executed by the statement:

    AreaCircle(&rastPort, center_x, center_y, radius);

Similarly, areaellipse() draws a filled ellipse with the specified radii
from the specified center point:

    AreaEllipse(&rastPort, center_x, center_y, horiz_r, vert_r);

Outlining with setopen() is not currently supported by the areacircle()
and areaellipse() routines.

    Caution:
    --------
    If you attempt to fill an area outside the bounds of the bitmap,
    using the basic initialized rastport, it may crash the system. you
    must either do your own software clipping to assure that the area is
    in range, or use the layers library.