Graphics problems typically focus on your ability to implement primitive graphics functions rather than using a high-level API as you would in most programming projects.
Eighth of a Circle
void drawEighthOfCircle( int radius );
void setPixel( int xCoord, int yCoord );
This problem is not as contrived as it seems. If you were trying to implement a full-circle drawing routine, you would want to do as little calculation as possible to maintain optimum performance. Given the pixels for one-eighth of a circle, you can easily determine the pixels for the remainder of the circle from symmetry.
This problem is an example of a scan conversion, converting a geometric drawing to a pixel-based raster image. You need an equation for a circle before you can calculate anything. The common mathematical function that produces a circle is: