The screen network is essentially open-ended and unbounded in any direction. The coordinate system has its origin (0,0) at the lower left corner of the opening window and increases to the right and up. In the present implementation, the coordinates are stored in double precision format with up to 20 significant figures to enable the retention of real world coordinates. The coordinates are used in specifying the location of a node, text item, or the bounding rectangle of a background picture.