An electrically-powered visual display unit (VDU), commonly known as a screen or a monitor, designed for displaying graphical information under program control in only one text/image colour, e.g., measured values or images from other devices. The information displayed will be limited (the view will become confusing to the user when too much information is shown). A keyboard may be connected for interactive manipulation of the data by the user. This group of devices is the product identifier for the monitor only and does not include the device(s) from which the data is generated and includes different screen technologies, e.g., cathode-ray tube (CRT) or liquid crystal display (LCD).