VDU stands for Visual Display Unit, which is an older British term used to describe any device used with computers to display text and images. It is a device that displays text and graphics on a screen, and it is commonly used in computers to display the output of the computers processing unit, allowing the user to interact with the computer and see the results of their actions. The VDU consists of a screen, which is usually a flat panel display such as an LCD or LED, and a circuit board that drives the screen and processes the input and output signals. The term VDU is often used synonymously with "monitor," but it can also be used to describe the display as a digital projector. The first VDUs were developed in the 1960s and were used primarily as terminal devices for computers. Early VDUs were essentially cathode ray tube (CRT) displays, and they were very large in size, as of 13 inches or less. During the 1990s, 15" and 17" displays became standard, and some manufacturers began producing displays over 20" in size. During the early 2000s, flat-panel displays started to replace the CRT displays and became more popular. Nowadays, the estimated size of 20" to 30" of screen size is most common to come with computers.