Abstract: A digital oscilloscope displays two waveforms on the CRT screen, a scroll bar waveform which is an abstracted representation of the full waveform data stored in memory and a generally expanded portion of the full waveform data in the memory. The portion of the full waveform that is displayed is selected by the operator by positioning cursor brackets along the abstracted scroll bar waveform to define a region of interest between the brackets. The region of interest so selected is displayed in expanded form showing all data points in the memory for the portion of the waveform being displayed. Creation of the abstracted scroll bar waveform is obtained by examining the waveform data in sections of equal time length and determining whether any data in each section falls within a series of predetermined ranges. The scroll bar waveform is formed of a series of columns of pixels equal in number to the number of sections of memory data, and having a number of pixels in each column equal to the number of data ranges.