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Anoutput device is any piece ofcomputer hardware that converts information or data into a human-perceptible form or, historically, into a physical machine-readable form for use with other non-computerized equipment. It can be text, graphics, tactile, audio, or video. Examples includemonitors,printers andsound cards.
In an industrial setting, output devices also include "printers" for paper tape and punched cards, especially where the tape or cards are subsequently used to control industrial equipment, such as an industrial loom with electrical robotics which is not fully computerized
Adisplay device is the most common form of output device which presents output visually on computer screen. The output appears temporarily on the screen and can easily be altered or erased.
With all-in-one PCs, notebook computers, hand held PCs and other devices; the term display screen is used for the display device. The display devices are also used in home entertainment systems, mobile systems, cameras and video game systems.
Display devices form images by illuminating a desired configuration ofpixels. Raster display devices are organized in the form of a 2-dimensional matrix with rows and columns. This is done many times within a second, typically 60, 75, 120 or 144 Hz on consumer devices.
The interface between a computer'sCPU and the display is aGraphics Processing Unit (GPU). This processor is used to form images on aframebuffer. When the image is to be sent to the display, the GPU sends its image through avideo display controller to generate avideo signal, which is then sent to adisplay interface such asHDMI,VGA,DisplayPort, orDVI.[1]
GPUs can be divided intodiscrete andintegrated units, the former being an external unit and the latter of which is included within a CPU die.[2] Discrete graphics cards are almost always connected to the host through thePCI Express bus, while older graphics cards may have usedAGP orPCI. Some mobile computers support an external graphics card throughThunderbolt (via PCIe).
A monitor is a standalone display commonly used with adesktop computer, or in conjunction to alaptop as an external display. The monitor is connected to the host through the use of a display cable, such asHDMI,DisplayPort,VGA, and more.
Older monitors useCRT technology, while modern monitors are typicallyflat panel displays using a plethora of technologies such asTFT-LCD,LED,OLED, and more.
Almost all mobile devices incorporate an internal display. These internal displays are connected to the computer through an internal display interface such asLVDS oreDP. The chief advantage of these displays is their portability.
Prior to the development of modern pixel-oriented displays,computer terminals were used, composed of a character-oriented display device known as aVDU and acomputer keyboard.[3]
These terminals were often monochromatic, and could only display text. Rudimentary graphics could be displayed through the use ofASCII art along withbox-drawing characters.Teleprinters were the precursors to these devices.
A projector is a display that projects the computer image onto a surface through the use of a high power lamp. These displays are seen in use to show slideshow presentations or in movie screenings.[4]
Display technologies can be classified based on working principle, lighting (or lack thereof), pixel layout, and more.
A monochrome display is a type of CRT common in the early days ofcomputing, from the 1960s through the 1980s, before color monitors became popular.[5]
They are still widely used in applications such as computerized cash register systems. Green screen was the common name for a monochrome monitor using a green "P1" phosphor screen.
Color monitors, sometimes calledRGB monitors, accept three separate signals (red, green, and blue), unlike a monochromatic display which accepts one. Color monitors implement the RGB color model by using three different phosphors that appear red, green, and blue when activated. By placing the phosphors directly next to each other, and activating them with different intensities, color monitors can create an unlimited number of colors. In practice, however, the real number of colors that any monitor can display is controlled by thevideo adapter.[6]
Aspeaker is an output device that produces sound through an oscillatingtransducer called a driver. The equivalent input device is amicrophone.
Speakers are plugged into a computer'ssound card via a myriad of interfaces, such as aphone connector for analog audio, orSPDIF for digital audio. While speakers can be connected through cables,wireless speakers are connected to the host device through radio technology such asBluetooth.
Speakers are most often used in pairs, which allows the speaker system to producepositional audio. When more than one pair is used, it is referred to assurround sound.
Certain models of computers includes a built-in speaker, which may sacrifice audio quality in favor of size. For example, the built-in speaker of a smartphone allows the users to listen to media without attaching an external speaker.
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The interface between an auditory output device and a computer is thesound card. Sound cards may beincluded on a computer'smotherboard, installed as anexpansion card, or as adesktop unit.[7][8]
The sound card may offer either an analog ordigital output. In the latter case, output is often transmitted usingSPDIF as either an electrical signal or anoptical interface known asTOSLINK. Digital outputs are then decoded by anAV receiver.
In the case of wireless audio, the computer merely transmits aradio signal, and responsibility of decoding and output is shifted to the speaker.
While speakers can be used for any purpose, there arecomputer speakers which are built for computer use. These speakers are designed to sit on a desk, and as such, cannot be as large as conventional speakers.[9]
Computer speakers may be powered viaUSB, and are most often connected through a 3.5mm phone connector.
ThePC speaker is a simple loudspeaker built intoIBM PC compatible computers. Unlike a speaker used with a sound card, the PC speaker is only meant to producesquare waves to produce sounds such asbeeping.
Modern computers utilize apiezoelectric buzzer or a small speaker as the PC speaker.
PC speakers are used duringPower-on self-test to identify errors during the computer's boot process, without needing a video output device to be present and functional.
AStudio monitor is a speaker used in astudio environment. These speakers optimize for accuracy.[10] A monitor produces a flat (linear) frequency response which does not emphasize or de-emphasize of particular frequencies.
Headphones,earphones, andearpieces are a kind of speaker which is supported either on the user's head, or the user's ear.
Unlike a speaker, headphones are not meant to be audible to people nearby, which suits them for use in thepublic,office or other quiet environments.
Noise-cancelling headphones are built withambient noise reduction capabilities which may employactive noise cancelling.
Loudspeakers are composed of several components within anenclosure, such as severaldrivers,active amplifiers,crossovers, and other electronics. Multiple drivers are used to reproduce the full frequencyrange of human hearing, withtweeters producing high pitches andwoofers producing low pitches.Full-range speakers use only one driver to produce as much of a frequency response as possible.[11]
WhileHi-Fi speakers attempt to produce high quality sound, computer speakers may compromise on these aspects due to their limited size and to be inexpensive, and the latter often uses full-range speakers as a result.[9]
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Arefreshable braille display outputs braille characters through the use of pins raised out of holes on its surface. It is ordinarily used byvisually-impaired individuals as an alternative to ascreen reader.[12]
Haptic technology involves the use of vibration and other motion to induce a sense of touch.[13] Haptic technology was introduced in the late 1990s for use ingame controllers, to provide tactile feedback while a user is playing a video game. Haptic feedback has seen further uses in the automotive field,aircraft simulation systems, andbrain-computer interfaces.[14][15]
In mobile devices,Apple added haptic technology in various devices, marketed as 3D Touch andForce Touch. In this form, several devices could sense the amount of force exerted on its touchscreen, whileMacBooks could sense two levels of force on itstouchpad, which will produce a haptic sensation.[16]
Aprinter is a device that outputs data to be put on a physical item, usually a piece ofpaper. Printers operate by transferring ink onto this medium in the form of the image received from the host.
Early printers could only print text, but later developments allowed printing of graphics. Modern printers can receive data in multiple forms likevector graphics, as animage, a program written in apage description language, or a string of characters.
Multiple types of printers exist:
Aplotter is a type of printer used to printvector graphics. Instead of drawing pixels onto the printing medium, the plotter draws lines, which may be done with awriting implement such as a pencil or pen.[17]
Ateleprinter orteletypewriter (TTY) is a type of printer that is meant for sending and receiving messages. Before displays were used to display data visually, early computers would only have a teleprinter for use to access thesystem console. As the operator would enter commands into its keyboard, the teleprinter would output the results onto a piece of paper. The teleprinter would ultimately be succeeded by acomputer terminal, which had a display instead of a printer.
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A computer can still function without an output device, as is commonly done withservers, where the primary interaction is typically over a data network. A number of protocols exist over serial ports or LAN cables to determine operational status, and to gain control over low-level configuration from a remote location without having a local display device. If the server is configured with a video output, it is often possible to connect a temporary display device for maintenance or administration purposes while the server continues to operate normally; sometimes several servers are multiplexed to a single display device though aKVM switch or equivalent.
Some methods to use remote systems are:
Media related toOutput devices at Wikimedia Commons