Abstract: A computer-based digital oscilloscope includes a touchscreen mechanism for generating output signals indicating when an operator has touched the oscilloscope's screen and identifying a particular touch zone area that the operator has touched from among a plurality of touch zone areas of the screen. A computer which controls display of waveforms and other images on the screen, monitors the touchscreen output signals to determine whether the operator is touching a touch zone and to determine whether a portion of a particular image other than a waveform is displayed on the screen within boundaries of the touch zone.