Abstract: A VDU line marker enables a specific line on a Visual Display Unit to be quickly and accurately located, similar to using a straight edge and/or a marker pen on paper. The line may be scrolled over the displayed information or the displayed information may be scrolled with the line stationary. A VDU electronic line marker is coupled between the Visual Display Unit and a computer/terminal combination and works independently of the software. It offers a choice of line color, line thickness and precise line position without using costly memory, memory controls, software, menus or multi-function use of keys and it derives its timing from the host computer.