DC Origin

Application programs are required to keep their graphics within an array of 2 (27) by 2 (27) pixels. The device space has additional size at the DDI level because the Window Manager may offset the application’s coordinate system by one signed 27-bit coordinate, the DC origin. The DC origin is not visible to the driver and the driver identifies the graphics coordinates only after the offset is applied. The graphics driver can take advantage of the fact that a graphics primitive cannot extend beyond the 2 (27) pixel-width coordinate system, and can use the extra space to manage overflow.