A combined display surface and a control device for a data processing system, wherein the position of a light beam hitting the display surface is measured and the measured result is used by the data processing system as a basis for determining a cursor position on the display surface. Several strip-shaped optical position detectors are arranged along the edge of the display surface, the measured signals of which are fed into the data processing system. The cross-sectional shape of the indicator beam is formed by several lines which protrude both the display surface and the position detectors arranged thereon. The optical position detectors are formed by a layered structure made of organic material.