Computer monitors are viewing devices commonly used in conjunction with a computer to view images, documents and other computer-related figures. Some computer monitors are separate devices that plug into a stand-alone computer, while some monitors are built into portable computers, or laptops. Monitors are available in a range of dimensions, features and price points.

Monitors tend to use LCD, or liquid crystal display, technology or CRT, or cathode ray tube, technology. Portable computers almost universally use LCD flat screen displays and newer computers tend towards LCD screens as well.http://computer.howstuffworks.com/monitor1.htm

Computer monitors may offer a square visible screen, or a wide-screen, rectangular shape. The quality of the display is partially based on the screen resolution. The number of dots of color per square inch, or pixels, helps establish the size and types of images that can be viewable on the screen.http://computer.howstuffworks.com/monitor1.htm

Two primary data points are used to describe the computer monitor size. The aspect ratio indicates the relationship of the width to the height of the computer screen. The most historical aspect ratio is 4:3. Widescreen monitors may have ratios of 16:10, 16:9 or 15:9. These widescreen aspect ratios are similar to ones found on high definition televisions.http://computer.howstuffworks.com/monitor2.htm As with televisions, the screen size of a computer monitor is measured diagonally. On CRT screens, the computer case is measured, on LCD monitors, the casing is not measured.http://computer.howstuffworks.com/monitor2.htm

LCD displays either use active or passive matrix technology. With the active technology, TFTs (thin film transistor) create a matrix of capacitors and transistors, that can illuminate individual pixels when an image needs to be displayed. It is turned off when no longer needed. The passive matrix uses an entire grid of charged metal to activate each pixel. Active matrix technology computer monitors are generally preferable due to the slow response rate of passive matrix displays.http://computer.howstuffworks.com/monitor5.htm