 The VT101 was essentially a base-model VT100, while the VT102 came standard with the AVO and serial printer port options pre-installed.The VT105 contained a simple graphics subsystem known as waveform graphics which was mostly compatible with same system in the earlier VT55.This system allowed two mathematical functions to be drawn to the screen on top of the normal text display, allowing text and graphics to be mixed to produce charts and similar output.