Editing Output device

{{short description|Piece of computer hardware}}
{{More citations needed|date=April 2023}}

An '''output device''' is any piece of [[computer 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 include [[Computer monitor|monitors]], [[Printer (computing)|printers]] and [[sound card]]s.

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 

== Visual ==
[[File:Ecran plat wikipedia.jpg|thumb|Monitor in use]]
{{Main|Electronic visual display}}
A ''display 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 of . 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&nbsp;Hz on consumer devices.

=== Interface ===

[[File:MSI MS-V328 outputs 20181231.jpg|thumb|left|Output interfaces on the rear of a graphics card]]

The interface between a computer's [[CPU]] and the display is a [[Graphics Processing Unit]] (GPU). This processor is used to form images on a [[framebuffer]]. When the image is to be sent to the display, the GPU sends its image through a [[video display controller]] to generate a [[video signal]], which is then sent to a [[List of video connectors|display interface]] such as [[HDMI]], [[VGA]], or [[DVI]]

GPUs can be divided into [[discrete GPU|discrete]] and [[integrated GPU|integrated]] units, the former being an external unit and the latter of which is included within a CPU die.<ref>{{Cite web|url=https://www.technipages.com/discrete-vs-integrated-graphics|title=Discrete vs Integrated Graphics|website=Technipages|date=22 July 2020 }}</ref> Discrete graphics cards are almost always connected to the host through the [[PCI Express]] bus, while older graphics cards may have used [[Accelerated Graphics Port|AGP]] or [[Peripheral Component Interconnect|PCI]]. Some mobile computers support an external graphics card through [[Thunderbolt (interface)|Thunderbolt]] (via PCIe).

=== Form factors ===

==== Monitor ====
{{Main|Computer monitor}}

A monitor is a standalone display commonly used with a [[desktop computer]], or in conjunction to a [[laptop]] as an external display. The monitor is connected to the host through the use of a display cable, such as [[HDMI]], [[DisplayPort]], [[VGA]], and more.

Older monitors use [[Cathode-ray tube|CRT]] technology, while modern monitors are typically [[flat panel display]]s using a plethora of technologies such as [[TFT-LCD]], [[LED]], [[OLED]], and more.

==== Internal display ====

Almost all mobile devices incorporate an internal display. These internal displays are connected to the computer through an internal display interface such as [[LVDS]] or [[Embedded DisplayPort|eDP]]. The chief advantage of these displays is their portability.

==== Terminal ====
[[File:Colossal Cave Adventure on VT100 terminal.jpg|thumb|[[Colossal Cave Adventure]] being played on a [[VT100]] terminal]]
{{Main|Computer terminal#VDUs}}

Prior to the development of modern pixel-oriented displays, [[computer terminals]] were used, composed of a character-oriented display device known as a ''VDU'' and a [[computer keyboard]].<ref>{{Cite web|url=https://www.pcmag.com/news/the-forgotten-world-of-dumb-terminals|title=The Forgotten World of Dumb Terminals|website=PCMag}}</ref>

These terminals were often monochromatic, and could only display text. Rudimentary graphics could be displayed through the use of [[ASCII art]] along with [[box-drawing character]]s. [[Teleprinter]]s were the precursors to these devices.

==== Projector ====
[[File:LED Projector machine.jpg|thumb|upright=0.8|An LED projector]]
{{Main|Video projector}}

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.<ref>{{Cite web|url=https://www.computerhope.com/jargon/p/projecto.htm|title=What is a Projector?|website=Computer Hope}}</ref>

=== Technologies ===
{{See also|Comparison of CRT, LCD, plasma, and OLED displays|Comparison of display technology}}

Display technologies can be classified based on working principle, lighting (or lack thereof), pixel layout, and more.

; [[Cathode-ray tube]] (CRT) : CRT screens produce an image using electron tube, which fires electrons at a phosphorous coated screen to light up pixels in order to display images.

; [[Liquid crystal display]] (LCD) : An LCD is a display technology employing the use of [[liquid crystal]]s to form images.

; [[Thin-film-transistor liquid crystal display|Thin-film transistor]] (TFT) : A TFT refers to the thin layer of transistors used with an LCD.

; [[LED-backlit LCD]] : An LCD display which uses [[LED]]s as a [[backlight]]. Prior to the use of LED based backlighting, [[Cold cathode#Lamps|Cold Cathode Fluorescent]] (CCFL) tubes were used. LED displays use an array of LEDs to form an image.

; [[Organic Light Emitting Diode]] (OLED) : Unlike an LED display, an OLED display does not use a backlight.

; [[Electronic paper]] (e-ink) : An e-ink display uses encapsulated pigment to form an image resembling printed paper, commonly used in [[e-book readers]].

=== Color output ===

==== Monochromatic display ====
A monochrome display is a type of CRT common in the early days of [[computing]], from the 1960s through the 1980s, before color monitors became popular.<ref>{{Cite news|url=https://www.elprocus.com/cathode-ray-tube/|title=Understanding of Cathode Ray Tube – CRT
|date=2013-10-26|work=ElProCus – Electronic Projects for Engineering Students|access-date=2018-09-15|language=en-US}}</ref>

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.

==== Colored display ====
Color monitors, sometimes called [[RGB color model|RGB]] 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 the [[Video card|video adapter]].<ref>{{Cite news|url=https://www.techwalla.com/articles/types-of-video-adapters|title=Types of Video Adapters {{!}} Techwalla.com|work=Techwalla|access-date=2018-09-15|language=en}}</ref>

== Auditory ==
{{main|Loudspeaker}}
[[File:CREATIVE GIGAWORKS T40 ii AUX input.jpg|thumb|A speaker connected to a smartphone|upright=0.6]]

A ''speaker'' is an output device that produces sound through an oscillating [[transducer]] called a driver. The equivalent input device is a [[microphone]].

Speakers are plugged into a computer's [[sound card]] via a myriad of interfaces, such as a [[Phone connector (audio)|phone connector]] for analog audio, or [[SPDIF]] for digital audio. While speakers can be connected through cables, [[wireless speaker]]s are connected to the host device through radio technology such as [[Bluetooth]].

Speakers are most often used in pairs, which allows the speaker system to produce [[positional audio]]. When more than one pair is used, it is referred to as [[surround 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.

=== Interface ===

[[File:Creative SoundBlaster Audigy 2 (SB0400)-4.jpg|Rear of a PCI sound card showing 3.5mm analog outputs|thumb|left|upright=0.8]]

The interface between an auditory output device and a computer is the [[sound card]]. Sound cards may be [[Sound card#Integrated sound hardware on PC motherboards|included]] on a computer's [[motherboard]], installed as an [[expansion card]], or as a [[sound card#USB sound cards|desktop unit]].<ref>{{Cite web|url=https://www.soundguys.com/what-is-a-sound-card-26851/|title=What is a sound card? Everything you need to know|website=SoundGuys|date=10 February 2023 }}</ref><ref>{{Cite web|url=https://www.lifewire.com/what-is-a-sound-card-2618160|title=What Is a Sound Card & What Does It Do?|website=Lifewire}}</ref>

The sound card may offer either an analog or [[digital audio|digital]] output. In the latter case, output is often transmitted using [[SPDIF]] as either an electrical signal or an [[fiber optic|optical]] interface known as [[TOSLINK]]. Digital outputs are then decoded by an [[AV receiver]].

In the case of wireless audio, the computer merely transmits a [[radio signal]], and responsibility of decoding and output is shifted to the speaker.

=== Form factors ===

==== Computer speakers ====
[[File:Creative T4 Wireless 2.1 Speakers.jpg|thumb|A pair of [[computer speaker]]s and a [[subwoofer]] used in a desktop environment]]
{{main|Computer speakers}}

While speakers can be used for any purpose, there are ''computer 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.<ref name="cnet">{{Cite web|title=Desktop and hi-fi speakers, what's the difference?|website=CNET|url=https://www.cnet.com/tech/home-entertainment/desktop-and-hi-fi-speakers-whats-the-difference/}}</ref>

Computer speakers may be powered via [[USB#Power|USB]], and are most often connected through a 3.5mm phone connector.

==== PC speaker ====
{{main|PC speaker}}

The ''PC speaker'' is a simple loudspeaker built into [[IBM PC]] compatible computers. Unlike a speaker used with a sound card, the PC speaker is only meant to produce [[Square wave (waveform)|square wave]]s to produce sounds such as [[beep (sound)|beeping]].

Modern computers utilize a [[piezoelectric speaker|piezoelectric buzzer]] or a small speaker as the PC speaker.

PC speakers are used during [[Power-on self-test#Progress and error reporting|Power-on self-test]] to identify errors during the computer's boot process, without needing a video output device to be present and functional.

==== Studio monitor ====
[[File:Andrew Pilling's 2011 Recording Equipment.jpg|thumb|A recording setup with two monitor speakers]]
{{Main|Studio monitor}}

A ''Studio monitor'' is a speaker used in a [[studio]] environment. These speakers optimize for accuracy.<ref>{{Cite web|url=https://bpmskills.com/producer/studio-monitors/what-is-a-studio-monitor/|title=What Is a Studio Monitor and What Are They Used For|website=Bpm Skills}}</ref> A monitor produces a flat (linear) frequency response which does not emphasize or de-emphasize of particular frequencies.

==== Headphones ====
{{main|Headphones}}

''Headphones'', ''earphones'', and ''earpieces'' 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 the [[public space|public]], [[office]] or other quiet environments.

[[Noise-cancelling headphones]] are built with [[Headphones#Ambient noise reduction|ambient noise reduction]] capabilities which may employ [[active noise cancelling]].

=== Technology ===

Loudspeakers are composed of several components within an [[loudspeaker enclosure|enclosure]], such as several [[Electrodynamic speaker driver|drivers]], [[Powered speakers|active amplifier]]s, [[audio crossover|crossover]]s, and other electronics. Multiple drivers are used to reproduce the full frequency [[Hearing range#Human|range of human hearing]], with [[tweeter]]s producing high pitches and [[woofer]]s producing low pitches. [[Full-range speaker]]s use only one driver to produce as much of a frequency response as possible.<ref>{{Cite web|title=Guide on what is a Full Range Speaker? Should I Go For it?|url=https://audiocurious.com/what-is-a-full-range-speaker/|website=Audio Curious}}</ref>

While [[Hi-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.<ref name="cnet" />

== Tactile ==
{{main|Tactile technology}}

=== Braille display ===
{{Multiple image
|image1=Brno, Universal Learning Design, Braille laptop 2 - detail (2).JPG|
|caption1=Closeup of a refreshable braille display
|image2=Plage-braille.jpg
|caption2=Braille display in use
|total_width=380px
}}
{{main|Refreshable braille display}}

A ''refreshable braille display'' outputs braille characters through the use of pins raised out of holes on its surface. It is ordinarily used by [[visually-impaired]] individuals as an alternative to a [[screen reader]].<ref>{{Cite web|url=https://www.afb.org/node/16207/refreshable-braille-displays|title=Refreshable Braille Displays|website=American Foundation for the Blind}}</ref>

=== Haptic technology ===
{{main|Haptic technology}}

''Haptic technology'' involves the use of vibration and other motion to induce a sense of touch.<ref>{{Cite web|url=https://www.rfwireless-world.com/Terminology/haptic-technology-basics.html|title=Haptic technology basics {{!}} How haptic technology Works}}</ref> Haptic technology was introduced in the late 1990s for use in [[game controller]]s, to provide tactile feedback while a user is playing a video game. Haptic feedback has seen further uses in the automotive field, [[flight simulator|aircraft simulation]] systems, and [[brain-computer interface]]s.<ref>{{Cite web|url=https://www.ultraleap.com/company/news/blog/what-is-haptic-feedback/|title=What is Haptic Feedback?|website=Ultraleap}}</ref><ref>{{Cite web|url=https://www.aratronics.com/hapticfeedbackandbci|title=Haptic Feedback and BCI|website=ARAtronics}}</ref>

In mobile devices, [[Apple Inc.|Apple]] added haptic technology in various devices, marketed as 3D Touch and [[Force Touch]]. In this form, several devices could sense the amount of force exerted on its touchscreen, while [[MacBook]]s could sense two levels of force on its [[touchpad]], which will produce a haptic sensation.<ref>{{Cite web|title=Apple Introduces iPhone 6s & iPhone 6s Plus|url=https://www.apple.com/newsroom/2015/09/09Apple-Introduces-iPhone-6s-iPhone-6s-Plus/|website=Apple Newsroom}}</ref>

== Printing devices ==

===Printer===
{{Main|Printer (computing)}}

A ''printer'' is a device that outputs data to be put on a physical item, usually a piece of [[paper]]. 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 like [[vector graphics]], as an [[image]], a program written in a [[page description language]], or a string of characters.

Multiple types of printers exist:
; [[Inkjet printer]]s : An inkjet printer injects tiny droplets onto the printing medium via a series of nozzles on a printing head.
; [[Laser printer]]s : A laser printer uses a [[laser]] to charge a drum of [[toner (printing)|toner]] in order to mark points where the toner would stick onto the medium.
; [[Thermal printer]]s : A printer which heats up a thermally sensitive roll of paper to reveal ink. Most often seen in retail stores to print [[receipt#Shop receipts|receipts]].
; [[Dot matrix printer]] : A printer which uses [[impact printer|impact]] to transfer ink from a ribbon to the medium.

===Plotter===
{{Main|Plotter}}

A ''plotter'' is a type of printer used to print [[vector graphics]]. Instead of drawing pixels onto the printing medium, the plotter draws lines, which may be done with a [[writing implement]] such as a pencil or pen.<ref>{{Cite web|url=https://www.techtarget.com/whatis/definition/plotter|title=What is plotter? - Definition from WhatIs.com|website=TechTarget}}</ref>

===Teleprinter===
{{Main|Teleprinter#Teleprinters in computing}}

A ''teleprinter'' or ''teletypewriter'' (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 the [[system 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 a [[computer terminal]], which had a display instead of a printer.

== Headless operation ==
{{Multiple image
|image1=X11 ssh tunnelling.png
|caption1=[[SSH]] can be used to run programs [[remote desktop|remotely]] on a [[headless computer]] without having an output device connected
|image2=Rackmount Console (1).jpg
|caption2=A rackmount console connected to a [[KVM switch]] allows multiple computers to be used through a switchable display and [[input devices]]
|total_width=400
}}
{{Main|Headless computer}}
{{See also|Headless software}}
A computer can still function without an output device, as is commonly done with [[server (computing)|servers]], 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 a [[KVM switch]] or equivalent.

Some methods to use remote systems are:
; Remote access : The computer's [[system console|console]] can be accessed through a network connection such as the Internet, using protocols such as [[telnet]] or [[SSH]].
; [[Remote desktop]] : Allows a [[graphical user interface]] to be accessed through remote access even without a monitor.
; [[KVM switch]] : Multiple computers are connected to a single display device which can be switched between computers.
; [[Serial port]] : A serial console can be connected to access the device's console.

== See also ==
* [[Input device]]

==References==
{{Reflist}}

==External links==
*{{Commons category-inline|Output devices}}

{{Basic computer components}}

[[Category:Computer output devices| ]]