Abstract: A system for displaying data, especially graphics data in color or grey scale on a raster-scanned display device. The information to be displayed is supplied in a coded representation in which a run of a new display value is represented by a transition code element representing at least the display value of the first picture element of the run, followed by a run-length code indicating the length of the segment of picture elements following the element or elements represented by the transition code. The coded representation is decoded to drive a display device.