Side-by-side displays for instrument having a data processing system

A data processing system for processing measurement instrument data is disclosed having a processor for digitally manipulating the measurement instrument data, a memory for storing the digitally manipulated data, and a display. In one preferred embodiment, the display simultaneously displays side by side two traces of the data, so as to provide two independent side by side displays. The displays can be either real time or can be recovered from memory, and a plotter can be used to produce hard copy. In another embodiment, the display provides a trace of the data with a plurality of markers. The user can then choose one of the markers as a reference and the processor will automatically provide the value of the trace at each of the other markers relative to the value of the reference marker. In another embodiment, the system includes a keyboard having a value key for entering into the processor the current value of a marker on the data trace.