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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 monitors, printers, speakers, headphones, projectors, GPS devices, optical mark readers, and braille readers.
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.
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 Hz on consumer devices.
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 display interface such as HDMI, VGA, or DVI
GPUs can be divided into discrete and integrated units, the former being an external unit and the latter of which is included within a CPU die. [1] Discrete graphics cards are almost always connected to the host through the PCI Express bus, while older graphics cards may have used AGP or PCI. Some mobile computers support an external graphics card through Thunderbolt (via PCIe).
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 CRT technology, while modern monitors are typically flat panel displays using a plethora of technologies such as TFT-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 as LVDS or eDP. 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 a VDU and a computer keyboard. [2]
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 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. [3]
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 of computing, from the 1960s through the 1980s, before color monitors became popular. [4]
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 called 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 adapter. [5]
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 for analog audio, or SPDIF for digital audio. While speakers can be connected through cables, wireless speakers 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.
The interface between an auditory output device and a computer is the sound card. Sound cards may be included on a computer's motherboard, installed as an expansion card, or as a desktop unit. [6] [7]
The sound card may offer either an analog or digital output. In the latter case, output is often transmitted using SPDIF as either an electrical signal or an 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.
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. [8]
Computer speakers may be powered via USB, and are most often connected through a 3.5mm phone connector.
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 waves to produce sounds such as beeping.
Modern computers utilize a piezoelectric buzzer or a small speaker as the PC speaker.
PC speakers are used during Power-on self-test to identify errors during the computer's boot process, without needing a video output device to be present and functional.
A Studio monitor is a speaker used in a studio environment. These speakers optimize for accuracy. [9] A monitor produces a flat (linear) frequency response which does not emphasize or de-emphasize of particular frequencies.
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, office or other quiet environments.
Noise-cancelling headphones are built with ambient noise reduction capabilities which may employ active noise cancelling.
Loudspeakers are composed of several components within an enclosure, such as several drivers, active amplifiers, crossovers, and other electronics. Multiple drivers are used to reproduce the full frequency range of human hearing, with tweeters producing high pitches and woofers producing low pitches. Full-range speakers use only one driver to produce as much of a frequency response as possible. [10]
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. [8]
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. [11]
Haptic technology involves the use of vibration and other motion to induce a sense of touch. [12] Haptic technology was introduced in the late 1990s for use in game 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, and brain-computer interfaces. [13] [14]
In mobile devices, 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 MacBooks could sense two levels of force on its touchpad, which will produce a haptic sensation. [15]
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:
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. [16]
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.
A computer can still function without an output device, as is commonly done with 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:
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
In digital imaging, a pixel, pel, or picture element is the smallest addressable element in a raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, pixels are the smallest element that can be manipulated through software.
A dot matrix is a 2-dimensional patterned array, used to represent characters, symbols and images. Most types of modern technology use dot matrices for display of information, including mobile phones, televisions, and printers. The system is also used in textiles with sewing, knitting and weaving.
A screensaver is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a designated time. The original purpose of screensavers was to prevent phosphor burn-in on CRT or plasma computer monitors. Though most modern monitors are not susceptible to this issue, screensaver programs are still used for other purposes. Screensavers are often set up to offer a basic layer of security by requiring a password to re-access the device. Some screensaver programs also use otherwise-idle computer resources to do useful work, such as processing for volunteer computing projects.
A graphics card is a computer expansion card that generates a feed of graphics output to a display device such as a monitor. Graphics cards are sometimes called discrete or dedicated graphics cards to emphasize their distinction to an integrated graphics processor on the motherboard or the central processing unit (CPU). A graphics processing unit (GPU) that performs the necessary computations is the main component in a graphics card, but the acronym "GPU" is sometimes also used to erroneously refer to the graphics card as a whole.
A framebuffer is a portion of random-access memory (RAM) containing a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in a complete video frame. Modern video cards contain framebuffer circuitry in their cores. This circuitry converts an in-memory bitmap into a video signal that can be displayed on a computer monitor.
Apple Inc. has sold a variety of LCD and CRT computer displays since introducing their first display in 1980. Apple paused production of their own standalone displays in 2016 and partnered with LG to design displays for Macs. In June 2019, the Pro Display XDR was introduced, however it was expensive and targeted for professionals. In March 2022, the Studio Display was launched as a consumer-targeted counterpart. These are currently the only Apple-branded displays available.
Display may refer to:
A film recorder is a graphical output device for transferring images to photographic film from a digital source. In a typical film recorder, an image is passed from a host computer to a mechanism to expose film through a variety of methods, historically by direct photography of a high-resolution cathode ray tube (CRT) display. The exposed film can then be developed using conventional developing techniques, and displayed with a slide or motion picture projector. The use of film recorders predates the current use of digital projectors, which eliminate the time and cost involved in the intermediate step of transferring computer images to film stock, instead directly displaying the image signal from a computer. Motion picture film scanners are the opposite of film recorders, copying content from film stock to a computer system. Film recorders can be thought of as modern versions of Kinescopes.
The refresh rate, also known as vertical refresh rate or vertical scan rate in reference to terminology originating with the cathode-ray tubes (CRTs), is the number of times per second that a raster-based display device displays a new image. This is independent from frame rate, which describes how many images are stored or generated every second by the device driving the display. On CRT displays, higher refresh rates produce less flickering, thereby reducing eye strain. In other technologies such as liquid-crystal displays, the refresh rate affects only how often the image can potentially be updated.
The display resolution or display modes of a digital television, computer monitor, or other display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT) displays, flat-panel displays and projection displays using fixed picture-element (pixel) arrays.
Text mode is a computer display mode in which content is internally represented on a computer screen in terms of characters rather than individual pixels. Typically, the screen consists of a uniform rectangular grid of character cells, each of which contains one of the characters of a character set; at the same time, contrasted to graphics mode or other kinds of computer graphics modes.
Pixels per inch (ppi) and pixels per centimetre are measurements of the pixel density of an electronic image device, such as a computer monitor or television display, or image digitizing device such as a camera or image scanner. Horizontal and vertical density are usually the same, as most devices have square pixels, but differ on devices that have non-square pixels. Pixel density is not the same as resolution — where the former describes the amount of detail on a physical surface or device, the latter describes the amount of pixel information regardless of its scale. Considered in another way, a pixel has no inherent size or unit, but when it is printed, displayed, or scanned, then the pixel has both a physical size (dimension) and a pixel density (ppi).
A composite monitor or composite video monitor is any analog video display that receives input in the form of an analog composite video signal to a defined specification. A composite video signal encodes all information on a single conductor; a composite cable has a single live conductor plus earth. Other equipment with display functionality includes monitors with more advanced interfaces and connectors giving a better picture, including analog VGA, and digital DVI, HDMI, and DisplayPort; and television (TV) receivers which are self-contained, receiving and displaying video RF broadcasts received with an internal tuner. Video monitors are used for displaying computer output, closed-circuit television and other applications requiring a two-dimensional monochrome or colour image.
An active shutter 3D system is a technique of displaying stereoscopic 3D images. It works by only presenting the image intended for the left eye while blocking the right eye's view, then presenting the right-eye image while blocking the left eye, and repeating this so rapidly that the interruptions do not interfere with the perceived fusion of the two images into a single 3D image.
Screen burn-in, image burn-in, ghost image, or shadow image, is a permanent discoloration of areas on an electronic display such as a cathode ray tube (CRT) in an old computer monitor or television set. It is caused by cumulative non-uniform use of the screen.
A video wall is a special multi-monitor setup that consists of multiple computer monitors, video projectors, or television sets tiled together contiguously or overlapped in order to form one large screen. Typical display technologies include LCD panels, Direct View LED arrays, blended projection screens, Laser Phosphor Displays, and rear projection cubes. Jumbotron technology was also previously used. Diamond Vision was historically similar to Jumbotron in that they both used cathode-ray tube (CRT) technology, but with slight differences between the two. Early Diamond vision displays used separate flood gun CRTs, one per subpixel. Later Diamond vision displays and all Jumbotrons used field-replaceable modules containing several flood gun CRTs each, one per subpixel, that had common connections shared across all CRTs in a module; the module was connected through a single weather-sealed connector.
A multiple-sync (multisync) monitor, also known as a multiscan or multimode monitor, is a raster-scan analog video monitor that can properly synchronise with multiple horizontal and vertical scan rates. In contrast, fixed frequency monitors can only synchronise with a specific set of scan rates. They are generally used for computer displays, but sometimes for television, and the terminology is mostly applied to CRT displays although the concept applies to other technologies.
A monochrome monitor is a type of computer monitor in which computer text and images are displayed in varying tones of only one color, as opposed to a color monitor that can display text and images in multiple colors. They were very common in the early days of computing, from the 1960s through the 1980s, before color monitors became widely commercially available. They are still widely used in applications such as computerized cash register systems, owing to the age of many registers. Green screen was the common name for a monochrome monitor using a green "P1" phosphor screen; the term is often misused to refer to any block mode display terminal, regardless of color, e.g., IBM 3279, 3290.
Display lag is a phenomenon associated with most types of liquid crystal displays (LCDs) like smartphones and computers and nearly all types of high-definition televisions (HDTVs). It refers to latency, or lag between when the signal is sent to the display and when the display starts to show that signal. This lag time has been measured as high as 68 ms, or the equivalent of 3-4 frames on a 60 Hz display. Display lag is not to be confused with pixel response time, which is the amount of time it takes for a pixel to change from one brightness value to another. Currently the majority of manufacturers quote the pixel response time, but neglect to report display lag.