A visual (or video) display unit of the raster scan type has a symbol memory, where the dot patterns of the available symbols are stored, and a refresh memory, where information is stored which identifies the symbols present on the image in question and their positions on the image. An auxiliary memory...http://www.google.com.tw/patents/US4591850?utm_source=gb-gplus-share專利 US4591850 - Auxiliary memory in a video display unit of the raster scan type
