What does vdu resolution refers to?

Answer 1

The display resolution of a digital television or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube (CRT) and flat panel or projection displays using fixed picture-element (pixel) arrays.

One use of the term "display resolution" applies to fixed-pixel-array displays such as plasma display panels (PDPs), liquid crystal displays (LCDs), Digital Light Processing (DLP) projectors, or similar technologies, and is simply the physical number of columns and rows of pixels creating the display (e.g., 1920×1200). A consequence of having a fixed grid display is that, for multi-format video inputs, all displays need a "scaling engine" (a digital video processor that includes a memory array) to match the incoming picture format to the display.

Note that the use of the word resolution here is misleading. The term "display resolution" is usually used to mean pixel dimensions(e.g., 1920×1200), which does not tell anything about the resolution of the display on which the image is actually formed. In digital measurement the display resolution would be given in pixels per inch. In analog measurement, if the screen is 10 inches high, then the horizontal resolution is measured across a square 10 inches wide. This is typically stated as "xxx lines horizontal resolution, per picture height." Example: Analog NTSC and PAL TVs can typically display 480 (for NTSC) lines horizontal resolution, per picture height which is equivalent to 640 total lines from left-edge to right-edge.