Just knocked up the Bresenham algorithm in a VB prog and it works well.
There is an error on the web site pseudo code however.  In order to specify
the origin of the circle Andy quotes this as a possibility:

    plot (x+xcenter,y+ycenter): plot (x+xcenter, -(y+ycenter))
    plot (-(x+xcenter),y+ycenter): plot (-(x+xcenter), -(y+ycenter))
    plot (y+ycenter,x+xcenter): plot (y+ycenter, -(x+xcenter))
    plot (-(y+ycenter),x+xcenter): plot (-(y+ycenter), -(x+xcenter))


However, this will break the circle into 4 quarters.  The brackets are not
needed on the negative terms:

i.e. -(x+xcenter) should be -x+xcenter.


Next stop, sin value extraction!


Regards

Mike Rigby-Jones
mrjones@nortel.co.uk