Output device

Auditory

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.

Interface

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.

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.

Form factors

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.

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

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 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.

Studio monitor

A Studio monitor is a speaker used in a studio environment. These speakers optimize for accuracy. A monitor produces a flat (linear) frequency response which does not emphasize or de-emphasize of particular frequencies.

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, office or other quiet environments.

Noise-cancelling headphones are built with ambient noise reduction capabilities which may employ active noise cancelling.

Technology

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.

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.

Tactile

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.

Haptic technology

Haptic technology involves the use of vibration and other motion to induce a sense of touch. 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.

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.

Printing devices

Printer

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 printers

An inkjet printer injects tiny droplets onto the printing medium via a series of nozzles on a printing head.

Laser printers

A laser printer uses a laser to charge a drum of toner in order to mark points where the toner would stick onto the medium.

Thermal printers

A printer which heats up a thermally sensitive roll of paper to reveal ink. Most often seen in retail stores to print receipts.

Dot matrix printer

A printer which uses impact to transfer ink from a ribbon to the medium.

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.

Teleprinter

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

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:

Remote access

The computer's 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.