computer monitor a liquid crystal display lcd computer monitor a cathode ray tube crt computer monitor a computer monitor is an output device that displays information in pictorial form a monitor usually comprises the display device circuitry casing and power supply the display device in modern monitors is typically a thin film transistor liquid crystal display tftlcd with led backlighting having replaced coldcathode fluorescent lamp ccfl backlighting older monitors used a cathode ray tube crt monitors are connected to the computer via vga digital visual interface dvi hdmi displayport thunderbolt lowvoltage differential signaling lvds or other proprietary connectors and signals originally computer monitors were used for data processing while television receivers were used for entertainment from the 1980s onwards computers and their monitors have been used for both data processing and entertainment while televisions have implemented some computer functionality the common aspect ratio of televisions and computer monitors has changed from 43 to 1610 to 169 modern computer monitors are easily interchangeable with conventional television sets however as computer monitors do not necessarily include components such as a television tuner and speakers it may not be possible to use a computer monitor as a television without external components history early electronic computers were fitted with a panel of light bulbs where the state of each particular bulb would indicate the onoff state of a particular register bit inside the computer this allowed the engineers operating the computer to monitor the internal state of the machine so this panel of lights came to be known as the monitor as early monitors were only capable of displaying a very limited amount of information and were very transient they were rarely considered for program output instead a line printer was the primary output device while the monitor was limited to keeping track of the programs operation as technology developed engineers realized that the output of a crt display was more flexible than a panel of light bulbs and eventually by giving control of what was displayed in the program itself the monitor itself became a powerful output device in its own right computer monitors were formerly known as visual display units vdu but this term had mostly fallen out of use by the 1990s technologies further information comparison of crt lcd plasma and oled and history of display technology multiple technologies have been used for computer monitors until the 21st century most used cathode ray tubes but they have largely been superseded by lcd monitors cathode ray tube cathode ray tube the first computer monitors used cathode ray tubes crts prior to the advent of home computers in the late 1970s it was common for a video display terminal vdt using a crt to be physically integrated with a keyboard and other components of the system in a single large chassis the display was monochrome and far less sharp and detailed than on a modern flatpanel monitor necessitating the use of relatively large text and severely limiting the amount of information that could be displayed at one time highresolution crt displays were developed for the specialized military industrial and scientific applications but they were far too costly for general use some of the earliest home computers such as the trs80 and commodore pet were limited to monochrome crt displays but color display capability was already a standard feature of the pioneering apple ii introduced in 1977 and the specialty of the more graphically sophisticated atari 800 introduced in 1979 either computer could be connected to the antenna terminals of an ordinary color tv set or used with a purposemade crt color monitor for optimum resolution and color quality lagging several years behind in 1981 ibm introduced the color graphics adapter which could display four colors with a resolution of 320 x 200 pixels or it could produce 640 x 200 pixels with two colors in 1984 ibm introduced the enhanced graphics adapter which was capable of producing 16 colors and had a resolution of 640 x 350 by the end of the 1980s color crt monitors that could clearly display 1024 x 768 pixels were widely available and increasingly affordable during the following decade maximum display resolutions gradually increased and prices continued to fall crt technology remained dominant in the pc monitor market into the new millennium partly because it was cheaper to produce and offered to view angles close to 180 degrees over lcds but improvements to the latter have made them much less obvious the dynamic range of early lcd panels was very poor and although text and other motionless graphics were sharper than on a crt an lcd characteristic known as pixel lag caused moving graphics to appear noticeably smeared and blurry liquid crystal display liquidcrystal display and thinfilmtransistor liquidcrystal display there are multiple technologies that have been used to implement liquid crystal displays lcd throughout the 1990s the primary use of lcd technology as computer monitors was in laptops where the lower power consumption lighter weight and smaller physical size of lcds justified the higher price versus a crt commonly the same laptop would be offered with an assortment of display options at increasing price points active or passive monochrome passive color or active matrix color tft as volume and manufacturing capability have improved the monochrome and passive color technologies were dropped from most product lines tftlcd is a variant of lcd which is now the dominant technology used for computer monitors the first standalone lcds appeared in the mid1990s selling for high prices as prices declined over a period of years they became more popular and by 1997 were competing with crt monitors among the first desktop lcd computer monitors was the eizo l66 in the mid1990s the apple studio display in 1998 and the apple cinema display in 1999 in 2003 tftlcds outsold crts for the first time becoming the primary technology used for computer monitors high dynamic range hdr has been implemented into highend lcd monitors to improve color accuracy since around the late 2000s widescreen lcd monitors have become popular in part due to television series motion pictures and video games transitioning to highdefinition hd which makes standardwidth monitors unable to display them correctly as they either stretch or crop hd content these types of monitors may also display it in the proper width however they usually fill the extra space at the top and bottom of the image with black bars other advantages of widescreen monitors over standardwidth monitors is that they make work more productive by displaying more of a users documents and images and allow displaying toolbars with documents they also have a larger viewing area with a typical widescreen monitor having a 169 aspect ratio compared to the 43 aspect ratio of a typical standardwidth monitor organic lightemitting diode organic lightemitting diode organic lightemitting diode oled monitors provide higher contrast and better viewing angles than lcds but they require more power when displaying documents with white or bright backgrounds measurements of performance the performance of a monitor is measured by the following parameters luminance is measured in candelas per square meter cdm2 also called a nit aspect ratio is the ratio of the horizontal length to the vertical length monitors usually have the aspect ratio 43 54 1610 or 169 viewable image size is usually measured diagonally but the actual widths and heights are more informative since they are not affected by the aspect ratio in the same way for crts the viewable size is typically 1in 25mm smaller than the tube itself display resolution is the number of distinct pixels in each dimension that can be displayed for a given display size maximum resolution is limited by dot pitch dot pitch is the distance between subpixels of the same color in millimeters in general the smaller the dot pitch the sharper the picture will appear refresh rate is the number of times in a second that a display is illuminated maximum refresh rate is limited by response time response time is the time a pixel in a monitor takes to go from active white to inactive black and back to active white again measured in milliseconds lower numbers mean faster transitions and therefore fewer visible image artifacts contrast ratio is the ratio of the luminosity of the brightest color white to that of the darkest color black that the monitor is capable of producing power consumption is measured in watts deltae color accuracy is measured in deltae the lower the deltae the more accurate the color representation a deltae of below 1 is imperceptible to the human eye deltaes of 2 to 4 are considered good and require a sensitive eye to spot the difference viewing angle is the maximum angle at which images on the monitor can be viewed without excessive degradation to the image it is measured in degrees horizontally and vertically size display size the area height and width of displays with identical diagonal measurements vary dependent on aspect ratio on twodimensional display devices such as computer monitors the display size or view able image size is the actual amount of screen space that is available to display a picture video or working space without obstruction from the case or other aspects of the units design the main measurements for display devices are width height total area and the diagonal the size of a display is usually by monitor manufacturers given by the diagonal ie the distance between two opposite screen corners this method of measurement is inherited from the method used for the first generation of crt television when picture tubes with circular faces were in common use being circular it was the external diameter of the glass envelope that described their size since these circular tubes were used to display rectangular images the diagonal measurement of the rectangular image was smaller than the diameter of the tubes face due to the thickness of the glass this method continued even when cathode ray tubes were manufactured as rounded rectangles it had the advantage of being a single number specifying the size and was not confusing when the aspect ratio was universally 43 with the introduction of flat panel technology the diagonal measurement became the actual diagonal of the visible display this meant that an eighteeninch lcd had a larger visible area than an eighteeninch cathode ray tube the estimation of the monitor size by the distance between opposite corners does not take into account the display aspect ratio so that for example a 169 21inch 53cm widescreen display has less area than a 21inch 53cm 43 screen the 43 screen has dimensions of 168in 126in 43cm 32cm and area 211sqin 1360cm2 while the widescreen is 183in 103in 46cm 26cm 188sqin 1210cm2 aspect ratio display aspect ratio until about 2003 most computer monitors had a 43 aspect ratio and some had 54 between 2003 and 2006 monitors with 169 and mostly 1610 85 aspect ratios became commonly available first in laptops and later also in standalone monitors reasons for this transition was productive uses for such monitors ie besides widescreen computer game play and movie viewing are the word processor display of two standard letter pages side by side as well as cad displays of largesize drawings and cad application menus at the same time in 2010 the computer industry started to move over from 1610 to 169 because 169 was chosen to be the standard highdefinition television display size and because they were cheaper to manufacture in 2011 nonwidescreen displays with 43 aspect ratios were only being manufactured in small quantities according to samsung this was because the demand for the old square monitors has decreased rapidly over the last couple of years and i predict that by the end of 2011 production on all 43 or similar panels will be halted due to a lack of demand resolution display resolution the resolution for computer monitors has increased over time from 320x200 during the early 1980s to 1024x768 during the late 1990s since 2009 the most commonly sold resolution for computer monitors is 1920x1080 apple introduced 2880x1800 with retina macbook pro at 154in 39cm on june 12 2012 and introduced a 5120x2880 retina imac at 27in 69cm on october 16 2014 by 2015 most major display manufacturers had released 3840x2160 resolution displays additional features power saving most modern monitors will switch to a powersaving mode if no videoinput signal is received this allows modern operating systems to turn off a monitor after a specified period of inactivity this also extends the monitors service life some monitors will also switch themselves off after a time period on standby most modern laptops provide a method of screen dimming after periods of inactivity or when the battery is in use this extends battery life and reduces wear integrated accessories many monitors have other accessories or connections for them integrated this places standard ports within easy reach and eliminates the need for another separate hub camera microphone or set of speakers these monitors have advanced microprocessors which contain codec information windows interface drivers and other small software which help in proper functioning of these functions glossy screen glossy display some displays especially newer lcd monitors replace the traditional antiglare matte finish with a glossy one this increases color saturation and sharpness but reflections from lights and windows are very visible antireflective coatings are sometimes applied to help reduce reflections although this only mitigates the effect curved designs in about 2009 necalienware together with ostendo technologies based in carlsbad ca were offering a curved concave 43inch 110cm monitor that allows better viewing angles near the edges covering 75 of peripheral vision this monitor had 2880x900 resolution led backlight and was marketed as suitable both for gaming and office work while for 6499 it was rather expensive while this particular monitor is no longer in production most pc manufacturers now offer some sort of curved desktop display directional screen narrow viewing angle screens are used in some security conscious applications 3d stereo display see also active shutter 3d system polarized 3d system and autostereoscopy newer monitors are able to display a different image for each eye often with the help of special glasses giving the perception of depth an autostereoscopic screen can generate 3d images without headgear touch screen touchscreen these monitors use touching of the screen as an input method items can be selected or moved with a finger and finger gestures may be used to convey commands the screen will need frequent cleaning due to image degradation from fingerprints tablet screens graphics tabletscreen hybrid a combination of a monitor with a graphics tablet such devices are typically unresponsive to touch without the use of one or more special tools pressure newer models however are now able to detect touch from any pressure and often have the ability to detect tilt and rotation as well touch and tablet screens are used on lcds as a substitute for the light pen which can only work on crts ultrawide screens 219 aspect ratio monitors that feature an aspect ratio of 219 as opposed to the more common 169 mounting computer monitors are provided with a variety of methods for mounting them depending on the application and environment desktop a desktop monitor is typically provided with a stand from the manufacturer which lifts the monitor up to a more ergonomic viewing height the stand may be attached to the monitor using a proprietary method or may use or be adaptable to a video electronics standards association vesa standard mount using a vesa standard mount allows the monitor to be used with an aftermarket stand once the original stand is removed stands may be fixed or offer a variety of features such as height adjustment horizontal swivel and landscape or portrait screen orientation vesa mount the flat display mounting interface fdmi also known as vesa mounting interface standard mis or colloquially as a vesa mount is a family of standards defined by the video electronics standards association for mounting flat panel monitors tvs and other displays to stands or wall mounts it is implemented on most modern flatpanel monitors and tvs for computer monitors the vesa mount typically consists of four threaded holes on the rear of the display that will mate with an adapter bracket rack mount rack mount computer monitors are available in two styles and are intended to be mounted into a 19inch rack a fixed 19inch 48cm 43 rack mount lcd monitor fixed a fixed rack mount monitor is mounted directly to the rack with the lcd visible at all times the height of the unit is measured in rack units ru and 8u or 9u are most common to fit 17inch or 19inch lcds the front sides of the unit are provided with flanges to mount to the rack providing appropriately spaced holes or slots for the rack mounting screws a 19inch diagonal lcd is the largest size that will fit within the rails of a 19inch rack larger lcds may be accommodated but are mountonrack and extend forward of the rack there are smaller display units typically used in broadcast environments which fit multiple smaller lcds side by side into one rack mount a 1u stowable clamshell 19inch 48cm 43 rack mount lcd monitor with keyboard stowable a stowable rack mount monitor is 1u 2u or 3u high and is mounted on rack slides allowing the display to be folded down and the unit slid into the rack for storage the display is visible only when the display is pulled out of the rack and deployed these units may include only a display or may be equipped with a keyboard creating a kvm keyboard video monitor most common are systems with a single lcd but there are systems providing two or three displays in a single rack mount system a panel mount 19inch 48cm 43 rack mount lcd monitor panel mount a panel mount computer monitor is intended for mounting into a flat surface with the front of the display unit protruding just slightly they may also be mounted to the rear of the panel a flange is provided around the lcd sides top and bottom to allow mounting this contrasts with a rack mount display where the flanges are only on the sides the flanges will be provided with holes for thrubolts or may have studs welded to the rear surface to secure the unit in the hole in the panel often a gasket is provided to provide a watertight seal to the panel and the front of the lcd will be sealed to the back of the front panel to prevent water and dirt contamination open frame an open frame monitor provides the lcd monitor and enough supporting structure to hold associated electronics and to minimally support the lcd provision will be made for attaching the unit to some external structure for support and protection open frame lcds are intended to be built into some other piece of equipment an arcade video game would be a good example with the display mounted inside the cabinet there is usually an open frame display inside all enduse displays with the enduse display simply providing an attractive protective enclosure some rack mount lcd manufacturers will purchase desktop displays take them apart and discard the outer plastic parts keeping the inner openframe lcd for inclusion into their product security vulnerabilities according to an nsa document leaked to der spiegel the nsa sometimes swaps the monitor cables on targeted computers with a bugged monitor cable in order to allow the nsa to remotely see what is being displayed on the targeted computer monitor van eck phreaking is the process of remotely displaying the contents of a crt or lcd by detecting its electromagnetic emissions it is named after dutch computer researcher wim van eck who in 1985 published the first paper on it including proof of concept phreaking is the process of exploiting telephone networks used here because of its connection to eavesdropping history of display technology flat panel display multimonitor vector monitor virtual desktop wikimedia commons has media related to computer monitors vtebasic computer componentsinput devices keyboard image scanner microphone pointing device graphics tablet joystick light pen mouse optical pointing stick touchpad touchscreen trackball refreshable braille display sound card webcam softcam video card output devices monitor refreshable braille display printer speakers plotter sound card video card removable data storage optical disc cd dvd bluray disk pack floppy disk memory card usb flash drive computer case central processing unit cpu hdd ssd sshd motherboard network interface controller power supply randomaccess memory ram fax modem expansion card ports ethernet firewire ieee 1394 parallel port serial port ps2 port usb thunderbolt displayport hdmi dvi vga esata audio jack 