By Emily McEwan


Monitors are display devices external to the computer case and connect via a cable to a port on the video card or motherboard. Even though the monitor sits outside the main computer housing, it is an essential part of the complete system.

Monitors come in two major types - LCD or CRT. CRT monitors look much like old-fashioned televisions and are very deep in size. LCD monitors are much thinner, use less energy, and provide a greater graphics quality.

Catho Ray tube


CRT stands for Cathode Ray Tube, and is descriptive of the technology inside that chunky monitor you might have on your desk.

CRTs receive their picture through an analogue cable, and that signal is decoded by the display controller, which handles the internal components of the monitor - think of it as the mini-CPU for the monitor.

CRTs have a distinctive funnel shape. At the very back of a monitor is an electron gun. The electron gun fires electrons towards the front through a vacuum which exists in the tube of the monitor. The gun can also be referred to as a cathode - hence the electrons fired foward are called Cathode Rays.

These rays correspond to to the red, green and blue channels of the display and video card.

At the neck of the funnel-shaped monitor is an anode, which is magnetised according to instructions from the display controller. As electrons pass the anode, they are shunted or pulled in one direction or the other depending on how magnetic the anode is at that time. This moves the electrons towards the correct part of the screen.


Flat panel monitors are a relatively recent product to enter the computer market. The clue to LCD technology is in the name - crystals that are in liquid form. Because they are in a liquid form they are easily manipulable, and this allows us to play with the way that light interacts with them. If you have a flat panel in front of you, try just pressing gently on the surface - you can see the crystals move around and alter the picture.

LCD panels are fairly simple to understand. The signal comes in and, as with a CRT, the signal from the video controller is decoded and understood by a display controller on the monitor itself. The controller has two things to control - the electrics of the pixels and the light source.

The actual image on an LCD is made up of a matrix of pixels. Unlike with CRTs, there's no complex equation of dot pitch and image area to try and calculate - the native resolution of the monitor is simply the number of pixels contained in the matrix. If it's a 17" monitor, chances are there are 1280 pixels in the matrix horizontally, and 1024 vertically.