Abstract: A segment constituting several points of digitized waveform data from a digitizer is stored in a pixel memory which has a number of memory locations corresponding to the number of pixels in the horizontal screen width of a raster scan video screen. As each new data point is written into a sequentially higher location in the memory, the data at the memory location a selected number of memory locations lower, constituting the desired number of pixels in the waveform segment, is erased. When a full new segment of data is in the waveform memory, the contents of the memory is provided to a raster scan graphics control unit which causes a new raster scan frame to be written on the video monitor screen. Only the portion of the waveform corresponding to the segment of waveform data in the waveform memory is illuminated on the screen. New data continues to be written into the waveform memory until another full segment of waveform data is in the memory and all previous waveform data points have been erased.