What is a display?
In computing, a display is a device with a screen that shows a rendered electronic image made up of pixels that are illuminated in a way that distinguishes text and graphic elements. Pixels are tiny areas of illumination -- bright dots of light -- that can number in the millions on a single display. Today, most displays use colored pixels.
What are the types of computer displays?
Over the years, three primary technologies have been used to render images on display screens:
- Cathode ray tube (CRT). Although seldom used today, the CRT was at one time the dominant type of display used in computing. Based on the same technology originally used in televisions, CRTs are big, bulky and consume a lot of power. This bulkiness is due in large part to the CRT technology, which requires a certain distance from the beam projection device to the screen to function. The CRT is made up of a large vacuum tube that uses electron beams to generate an image on the phosphorescent surface of the screen.
- Liquid crystal display (LCD). The LCD is a type of flat-panel display that is much thinner and lighter than the CRT. To generate an image, the LCD uses liquid crystal sandwiched between two panes of polarized glass, with a backlight illuminating the glass. LCDs work by blocking light rather than creating it. The display's pixels are switched on or off electronically as the liquid crystals rotate the polarized light. LCDs are generally available in three panel types: twisted nematic (TN), in-plane switching (IPS) and vertically aligned (VA). Because of its thinner profile and lower power consumption, LCDs have replaced CRTs for most computing needs.
- Light-emitting diode (LED). An LED display is a type of LCD that uses a set of LEDs as its light source, rather than the types of backlights (often cold cathode fluorescent lamps) used for LCD displays. LED technology is generally smaller and lighter than the original LCD. A newer type of LED is the organic LED (OLED), which uses an organic polymer as the semiconductor material. And a more recent type of LED is the quantum dot LED (QLED), which incorporates a layer of nanoparticles to improve color and luminance.
- Video Graphics Array (VGA). This was one of the original analog display standards used extensively with CRT monitors. The first generation of VGA technology supported a resolution of 640 x 480. Because this standard was unable to meet the demands of newer displays, extended versions of VGA were introduced, such as Super VGA (SVGA), Extended Graphics Array (XGA), and Ultra Extended Graphics Array (UXGA), which can support resolutions up to 1600 x 1200. Despite these gains, VGA has been steadily giving way to digital display technologies that can handle greater resolutions.
- Digital Visual Interface (DVI). DVI is a newer technology than VGA. It can carry both analog and digital signals, depending on the DVI type. It also offers better image quality, delivering resolutions up to 2560 x 1600. There are three primary types of DVI systems: DVI-A (analog only and rarely used), DVI-D (digital only) and DVI-I (digital and analog).
- DisplayPort (DP). DisplayPort is a digital display interface that was standardized by the Video Electronics Standards Association (VESA) as a high-performance replacement for display technologies such as VGA and DVI. DisplayPort is extensible, supports high resolutions and uses packetized data transmission like Ethernet. The latest versions of the DisplayPort -- 1.3 and 1.4 -- can deliver resolutions up to 7680 x 4320.
- High-Definition Multimedia Interface (HDMI). HDMI is popular in connecting audiovisual devices, as well as computers to monitors. It supports high-quality digital and audio signals (both uncompressed) and can handle display resolutions up to 3840 x 2160. Many computers now include HDMI ports to simplify connecting to home AV equipment. Many external monitors also include HDMI ports.Whether the image signals are digital or analog, the computer must be able to communicate with the display. With an integrated display, connectivity is established through the computer's architecture.If an external monitor is used, the computer and monitor must support the same connectivity technology. Currently, there are four primary display technologies used to facilitate communications:
- Video Graphics Array (VGA). This was one of the original analog display standards used extensively with CRT monitors. The first generation of VGA technology supported a resolution of 640 x 480. Because this standard was unable to meet the demands of newer displays, extended versions of VGA were introduced, such as Super VGA (SVGA), Extended Graphics Array (XGA), and Ultra Extended Graphics Array (UXGA), which can support resolutions up to 1600 x 1200. Despite these gains, VGA has been steadily giving way to digital display technologies that can handle greater resolutions.
- Digital Visual Interface (DVI). DVI is a newer technology than VGA. It can carry both analog and digital signals, depending on the DVI type. It also offers better image quality, delivering resolutions up to 2560 x 1600. There are three primary types of DVI systems: DVI-A (analog only and rarely used), DVI-D (digital only) and DVI-I (digital and analog).
- DisplayPort (DP). DisplayPort is a digital display interface that was standardized by the Video Electronics Standards Association (VESA) as a high-performance replacement for display technologies such as VGA and DVI. DisplayPort is extensible, supports high resolutions and uses packetized data transmission like Ethernet. The latest versions of the DisplayPort -- 1.3 and 1.4 -- can deliver resolutions up to 7680 x 4320.
- High-Definition Multimedia Interface (HDMI). HDMI is popular in connecting audiovisual devices, as well as computers to monitors. It supports high-quality digital and audio signals (both uncompressed) and can handle display resolutions up to 3840 x 2160. Many computers now include HDMI ports to simplify connecting to home AV equipment. Many external monitors also include HDMI ports.