Abstract: A digital oscilloscope includes an acquisition system for digitizing an input signal to produce and store in memory a waveform data sequence representing the input signal. A display system within the instrument reads out and processes the data stored in the memory to produce a waveform display representing the input signal. The instrument responds to an input "erase" command from a user by overwriting the waveform data sequence stored in memory with a predetermined data sequence defining an easily recognizable display pattern. The oscilloscope thereafter performs a checksum operation on overwritten portions of memory to determine whether the overwrite operation was successful, and displays an indication of overwrite success on its screen.