How LCD Monitors Work ...

Dual Monitors

One way to expand your computer's display is to add a second monitor. Using dual monitors can make you more productive and add a lot to your computing experience.

With two monitors, you can:

• View large spreadsheets

• Make changes to a web page's code on one monitor and view the results on the second

• Open two different applications, such as a Word document on one monitor and your web browser on the second

Besides two displays and two sets of the appropriate video cables, the only other thing you need is a video adapter with two display connections. The connections can be analog or digital; they need only to match the type of connections on the monitors. It does not matter what type of monitor you use; two LCDs, two CRTs, or one of each works fine as long as the video adapter has compatible connections.

If you don't have a video adapter with two connections, you can purchase one and replace your current adapter. This generally works better than simply installing another video card with a single connection. Combination cards also come with more features, such as a TV-out port.

In addition to verifying your hardware, you should also double-check your computer's operating system to be sure it supports the use of dual monitors. For example, Windows 98 SE, Me, 2000, and XP support multiple monitors.

If you really want to increase your screen real estate, especially for applications such as financial trading or 3-D design, you can even implement three or more monitors.

Other Technologies

Touch-screen Monitors
Displays with touch-screen technology let you input information or navigate applications by touching the surface of the display. The technology can be implemented through a variety of methods, including infrared sensors, pressure-sensitive resistors or electronic capacitors.

Wireless Monitors
Similar in looks to a tablet PC, wireless monitors use technology such as 802.11b/g to connect to your computer without a cable. Most include buttons and controls for musing and web surfing, and some also include keyboards. The displays are battery-powered and relatively lightweight. Most also include touch-screen capabilities.

Television and HDTV Integration
Some displays have built-in television tuners that you can use for viewing cable TV on your computer. You can also find displays that accept S-video input directly from a video device. Additional features include picture-in-picture or picture-on-picture capability, a remote control and support for high-definition television (HDTV).

Display Technology
Often referred to as a monitor when packaged in a separate case, the display is the most-used output device on a computer. The display provides instant feedback by showing you text and graphic images as you work or play.
Most desktop displays use liquid crystal display (LCD) or cathode ray tube (CRT) technology, while nearly all portable computing devices such as laptops incorporate LCD technology. Because of their slimmer design and lower energy consumption, monitors using LCD technology (also called flat panel or flat screen displays) are replacing the venerable CRT on most desktops.


Standards and Resolution
Resolution refers to the number of individual dots of color, known as pixels, contained on a display. Resolution is expressed by identifying the number of pixels on the horizontal axis (rows) and the number on the vertical axis (columns), such as 800x600. Resolution is affected by a number of factors, including the size of the screen.
As monitor sizes have increased over the years, display standards and resolutions have changed. In addition, some manufacturers offer widescreen displays designed for viewing DVD movies.

In addition to the screen size, display standards and resolutions are related to something called the aspect ratio. Next, we'll discuss what an aspect ratio is and how screen size is measured.

Color Depth
The combination of the display modes supported by your graphics adapter and the color capability of your monitor determine how many colors it displays. For example, a display that operates in SuperVGA (SVGA) mode can display up to 16,777,216 (usually rounded to 16.8 million) colors because it can process a 24-bit-long description of a pixel. The number of bits used to describe a pixel is known as its bit depth.
With a 24-bit bit depth, eight bits are dedicated to each of the three additive primary colors -- red, green and blue. This bit depth is also called true color because it can produce the 10,000,000 colors discernible to the human eye, while a 16-bit display is only capable of producing 65,536 colors. Displays jumped from 16-bit color to 24-bit color because working in eight-bit increments makes things a whole lot easier for developers and programmers.
Simply put, color bit depth refers to the number of bits used to describe the color of a single pixel. The bit depth determines the number of colors that can be displayed at one time. Take a look at the following chart to see the number of colors different bit depths can produce:

Notice that the last entry in the chart is for 32 bits. This is a special graphics mode used by digital video, animation and video games to achieve certain effects. Essentially, 24 bits are used for color and the other eight bits are used as a separate layer for representing levels of translucency in an object or image. Nearly every monitor sold today can handle 24-bit color using a standard VGA connector.
To create a single colored pixel, an LCD display uses three subpixels with red, green and blue filters. Through the careful control and variation of the voltage applied, the intensity of each subpixel can range over 256 shades. Combining the subpixels produces a possible palette of 16.8 million colors (256 shades of red x 256 shades of green x 256 shades of blue).
Now that you have a general idea of the technology behind computer monitors, let's take a closer look at LCD monitors, CRT monitors, and the general buying considerations for both.