The output devices of a computer system include:

Most general purpose computers are based on von Neumann architecture. This includes using the fetch-decode-execute cycle to process program instructions. Computer performance depends on cache size, clock speed and the number of cores.

An output device is any hardware device used to send data from a computer to another device or user.

Usually, most output peripherals are meant for human use, so they receive the processed data from the computer and transform it in the form of audio, video, or physical reproductions.

Typical examples of output devices are monitors and projectors (video), headphones and speakers (audio), or printers and plotters (physical reproduction in the form of text or graphics).

Output devices allow computers to communicate with users and with other devices.

This can include peripherals, which may be used for input/output (I/O) purposes, like network interface cards (NICs), modems, IR ports, RFID systems and wireless networking devices, as well as mechanical output devices, like solenoids, motors and other electromechanical devices.

Unlike input devices, output devices are not strictly necessary for a computer to operate.

However, without them the purpose of a computer may be defeated since there’s no way of determining how the data is currently processed or what the system is doing.

For example: if you click “play” on a YouTube video and then plug your monitor off, the computer will keep reproducing it and, provided the speakers are turned on, the audio output will be guaranteed.

In fact, the computer will still consume all the resources and process the data required to run the video regardless of the presence of the output device (the monitor).

In order to work, an output device needs to receive a signal from the computer after the information it has processed is ready to be displayed into its new format (e.g. audio or video).

The process usually follows certain steps:

1. A signal is sent from an input device to the computer (e.g. the user clicks with the mouse on the “play” button of a video).

2. The computer processes the input and then sends a new signal to the output device (e.g. the monitor and speakers).

3. The output devices receive the signal and display the output (e.g. the monitor shows the video, and the speakers run the audio signal).

Additional steps can be taken to let other output devices process this same signal.

For example: the user could click the “Print Screen” button on his keyword (input device) to request the printer (output device) to print a screenshot of that video.

Note that the other output device (the monitor) is not required to process this signal, so even if the monitor was turned off, the printer will still be able to print that screenshot even if the user couldn’t see it.

Other more or less common output devices include speech-generating devices that transform plain text into audible sounds, and GPS devices that process satellite geolocation signals to calculate position and time.

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Computers are a necessity of today's technological era. They are making operations or tasks easier in almost every sector. We cannot even think of a world without computers because nowadays most services depend on them. The computer has a wide range of output devices, which help us to see what the computer is doing. Although computers can operate without an output device, we will not obtain the results of the processed data/ inputs from the computer.

This article discusses most of the output devices of a computer. Before discussing computer output devices, let's first understand the definition of the output device:

Definition of Output Device

An output device is essentially a piece of instrument or computer hardware that retrieves data from a computer system and further translates the received data into a form understandable to humans. The most common human-understandable forms typically include text, visual, audio, or a hard copy (printed on a paper). 

In simple words, an output device is a type of peripheral device that helps us to get data processed from a computer, usually in the form of audio, visual, and xerox.

Note: Output devices and Output Units are the same things. They are two similar terms used in different ways by different people. Also, they are termed peripheral devices or auxiliary devices.

Results of data fed into a computer machine are performed using specific hardware devices. During the process, the result (retrieved data) is referred to as the output from the computer machine while the devices or hardware devices used to obtain the output are referred to as the output devices.

The output devices can be classified into four categories, such as visual, data, print, and sound. Depending on the type of computer and the requirements, different output devices can be attached to the computer system. The most common output devices are listed below:

Since the output devices help in performing the necessary functions for the computer, they are considered as parts of the computer system. Output devices operate by receiving signals from computers and use that signal to process a task to provide output in varying forms.

The function of the output device can be easily understood by the following steps:

• When we press a key on the keyboard (input device), it sends a signal to the computer.

• The computer further processes the input and sends the signal to the monitor (output device).

• The monitor then translates the received signals and displays the result (output) on the screen, whichever key we have pressed using the keyboard.

That is how an output device functions. In case there are no output devices attached to the computer, we would still be able to press a key on the keyboard and the computer would still process it. However, we wouldn't be able to see what key we have pressed to ensure the correct inputs.

Several types of output devices are available that help in obtaining output from a computer. Each device has its function, merits, and demerits. The following are examples of commonly used output devices:

The most common example of an output device is a monitor. It is also known as VDU (Visual Display Unit). It consists of several components, such as screens, circuitry, power supplies, screen adjustment buttons, and more, which are assembled into a casing. The monitor provides output from a computer on a screen so that users can interact with or view data digitally. 

The monitor typically provides output in symbolic and graphical form, generated using several small dots, known as pixels. These pixels are usually arranged in a rectangular form. That way, the monitor creates real-time video pictures and other contents with the help of a video card. The more pixels we have, the better the sharpness and quality of images.

Monitors are broadly classified into two types, such as cathode-ray tubes and flat-panel displays:

CRT monitors use cathode ray tubes that help to produce images in the form of video signals on the screen. More clearly, the cathode ray tube generates electron beams through the electron guns, which strike the screen's inner phosphorescent surface to form the image on the screen. 

The monitor usually contains millions of phosphorus dots in red, green, and blue. These phosphorescent dots help to form pixels. The sharpness and clarity of the picture depend mainly on how many pixels are there and what their sizes are. The smaller the pixels, the better the picture quality of the screen.

Since CRT monitors use red, green, and blue electron beams, the colors we see on the screen are a mixture of these three lights. The magnetic field helps to control the electron rays accordingly. Due to the large size and heavy power consumption, CRT monitors are currently not in widespread use.

Flat-panel displays use liquid crystal technology or plasma to generate output. In these devices, light is passed through liquid crystals to form pixels. Nowadays, most of the devices are manufactured using flat panel displays as there are significant advantages of using these displays over the traditional CRT displays.

Flat-panel displays typically have lower volume, weight, and power consumption than CRT monitors. They are very light and thin and can even be hung on walls or worn on wrists. These types of displays can be found in devices such as calculators, portable video games, laptops, monitors, smartwatches, and many other digital devices.

There are mainly two categories of flat-panel displays, such as a non-emissive display and an emissive display.

Non-Emissive Displays: Non-emissive displays include all such devices that use optical effects to transform sunlight or light from other sources into graphics patterns. LCD is an example of a non-emissive display.

• LCD: LCD monitors are small and lightweight flat panel displays. These monitors use the light-modulating property of liquid crystals. In particular, an LCD screen is constructed using two layers of polarized glasses with a liquid crystal solution between them. Additionally, a cold cathode fluorescent light is placed in these devices to backlight the displays.

When light is passed through the first layer, the electric current aligns the liquid crystals. These aligned crystals then allow different levels of light to pass through another layer, creating an image on the screen. These displays can be found on the screens of laptops, smartphones, tablets, televisions, etc.

LCDs typically use a matrix of pixels to display images on the screen. Previously, LCDs used passive-matrix technology, whereas modern LCDs use capacitors and thin-film transistors as well as active matrix technology. Because of this, modern LCDs include pixels that can hold their charge. Thus, modern LCDs do not have the blurry image problem that older LCDs had to face when images moved fast.   

Emissive Displays: Emissive displays include all such devices that typically transform electrical energy to light. LED and plasma panels are examples of emissive displays.

• LED: The LED monitor is an improved version of the LCD monitor. Unlike LCDs, LED monitors make use of multiple panels consisting of multiple LEDs to backlight the display. Regardless of the backlighting source, the technology used in LEDs is similar to LCD. LED monitors are comparatively more reliable because they have a wider dimming range.

LED displays are in widespread use due to their advantages over other displays. These displays can be found in modern TVs, monitors, laptop screens, smartphones, tablets, smartwatches, etc. LED displays have better light intensity and therefore produce better quality output. In addition, LEDs are known to consume less power than other displays.

• Plasma: Plasma monitors use plasma display technology. These displays usually consist of small cells between two glass panels. Cells typically contain a mixture of noble gases with small amounts of mercury. When the voltage is applied, the gas in the cells converts to plasma and emits ultraviolet light to produce images on the screen.

Plasma monitors are relatively thinner than CRT monitors and brighter than LCD monitors. These types of monitors offer high resolutions up to 1920 x 1080 with excellent contrast ratio, refresh rates, and wide viewing angles. That way, they provide us a brilliant viewing experience either we watch movies, play games, or study.

The printer is another most common example of output devices that can be easily found in homes and many workplaces. The primary function of a printer is to make a copy (usually called ‘Hard copy’ or ‘Xerox copy’) or print the information on paper that is sent from the computer to the printer. The printer receives electronic data from the computer and produces a hard copy of the processed data.

Earlier printers were only able to make black and white prints; however, today's printers can produce monochrome and color prints with high quality. Additionally, they are now available with wireless support, making the print job much easier.

Printers are broadly classified into two types, such as impact printers and non-impact printers:

Impact printers typically use a type of hammer or print head that is pushed onto the ink ribbon, which then jointly strikes on a paper and draws the characters. Although these printers come at a low cost, they make a lot of noise and are therefore not in widespread use nowadays. However, they can be the best choice for bulk printing due to their reasonable cost.

Impact printers are divided into two types, such as character printers and line printers:

Character Printers: Character printers refer to printers that can only print one character at a time. These printers use one single stroke of the hammer/ print head at a time. Therefore, they cannot print an entire line at once. In addition, character printers are not compatible with printing images (except a dot-matrix printer), making them less useful for the current era.

Character printers are further sub-divided into the following two types:

• Dot Matrix Printers: Dot matrix printers are the most popular type of impact character printer. These printers use a pattern of dots to print characters or pictures. The pattern is structured by striking a ribbon soaked in ink on paper with the help of a hammer or print head. The print head consists of several pins and structures with multiple dots in a pattern to generate the corresponding character.

To print color documents, the black ribbon on these printers can be replaced with colored stripes. Generally, dot matrix printers can print 200–500 characters per second.

• Daisy Wheel Printers: The daisy wheel printer consists of a wheel or a disc with a print head and several pins such as a daisy's petal (a flower) corresponding to the characters. Thus, it is called a daisy wheel printer.

To make a print, the printer rotates the wheel with its respective characters. When the desired character reaches the print location, the hammer strikes the disc and the ink ribbon further creates a corresponding character on the paper. These printers are slow and noisy, making them unusable for today's generation.

Line Printers: Line printers refer to printers that can print one line at a time. These printers are high-speed impact printers and can print up to 3000 lines per minute. Like character printers, line printers are also not compatible with printing images.

Line printers are further sub-divided into the following two types:

• Drum Printers: Drum printers use a rotating drum that has a circular band on its surface. The band contains characters on its surface. Multiple hammers are used in these printers to print characters from different columns of the band. A paper is rolled around the surface of the drum. When the print command is given, the drum rotates and the hammer strikes on the ink ribbon, respective to the desired character. That way, the drum printers eventually print a character on paper.  

Drum printers usually print character by character and are not compatible with printing graphics. However, the overall speed of printing characters using these printers is quite fast. Like other impact printers, drum printers also make noise due to the hammering system.

• Chain Printers: Chain printers use a rotating chain with characters printed on their surface. The chain rotates horizontally with the help of two gears. These printers have several hammers: the total number of hammers is equal to the number of print positions in these printers. 

When the print command is given, the chain rotates and the hammer strikes the ink ribbon as soon as the desired character arrives at the print location. The ribbon then creates a character on paper. These printers can print 500 to 3,000 lines per minute. Chain printers also make a noise like other impact printers.

Non-impact printers do not use any hammer or print head to strike the ink ribbon. These printers print characters or images without using ribbons. Unlike impact printers, the internal machinery of non-impact printers does not make direct physical contact with the paper. These types of printers usually print the entire page at once, and therefore, are also called page printers. 

Non-impact printers are divided into two types, such as laser printers and inkjet printers. Among all printers, these are the two most common types of printers.

Laser Printers: Laser printers use laser light to make dots, which later help to form letters to print on paper. In particular, the laser beam hits the drum and structures the image structure on the drum by controlling the electric charge. The drum then rolls into toner and sends the charged structure to the toner. The toner prints the respective structure on the paper with the help of some heat and pressure.

After the document is fully printed, the drum loses electric charge and collects the remaining toner. Instead of using liquid ink, laser printers use powder toner for printing documents. This ultimately helps these printers to produce quality prints with resolutions of 600 dpi (dots per inch) and more.

Inkjet Printers: Inkjet printers are widely used non-impact character printers. These printers usually print the characters or pictures by spraying small drops of ink on the paper. These droplets are passed through an electric field that controls the sprays to print the appropriate characters or images.

Inkjet printers do not make noise because there is no hammer like an impact printer. These printers use ink cartridges. Modern inkjet printers have ink cartridges of four different colors: black, yellow, cyan, and magenta. This ultimately allows these printers to produce high-quality color prints.

Touchscreens are output devices seen in various devices due to the use of portable devices. It is a thin, lightweight panel developed to receive output from a computer. In particular, the touch screen is a touch-sensitive surface or monitor that can display visuals or graphics.

Nowadays touch screens can be easily found in modern devices, such as laptops, smartphones, tablets, etc. Because we can also use touchscreens to give input, these devices are also known as input-output devices.

A projector is a display output device because it receives images from a computer and transfers those computer images to a wall, surface, or projection screen. Specifically, the computer first sends the signal to the video card, which then transmits the signal to the projector to project the images on the surface.

Previously, projectors used lens systems that produced images by shining light through transparent lenses. Modern projectors use laser systems to directly project images using lasers. Modern projectors are also called video projectors because these projectors can also project moving images along with still images. 

Speakers are one of the most common output devices used on computers to achieve audio output. Computer speakers usually receive signals from the sound card and then convert them to audio. These speakers use internal amplifiers that vibrate at different frequencies to increase/decrease the volume or amplitude of the sound as per the choice of the user.

Most monitors and laptops come with inbuilt speakers. However, we can also connect external speakers to the computer via both wired and wirelessly. The speakers are mainly used to obtain the loud sound output.

Headphones, also known as earphones, are output devices that allow us to listen to audio from a computer. These devices are mainly used to listen to audio privately or without disturbing others around. Headphones come in a variety of sizes and designs and can connect with supported devices via both wired or wirelessly.  

Headphones primarily receive audio input from connected devices and convert them into audio output in waveforms. Many headphones come with a microphone, making them a great device for communicating with family or friends. These output devices are mostly used to communicate in gaming and on bulk calls.

A sound card, also known as an expansion card, is a type of output device that is usually installed on a motherboard in the inner case of a computer. The main function of a sound card is to control the output of sound signals and enable devices such as speakers and headphones to function.

Sound cards usually work with the help of drivers and software. Although a sound card is not mandatory for the basic functions of a computer system, it is added to the computer for listening to audio, playing games, watching movies, listening to music, video conferencing, and more.

As the sound card, a video card is also an expansion card installed on the slots in the motherboard. The primary function of a video card is to process images and videos so that their visuals are displayed on the screen. It is also known as a video adapter.

A video card is a basic requirement of a computer system and therefore most computers come with regular video and graphics capabilities to display images and video. However, to get more detailed graphics, a higher video card is required. This is why most gaming computers and laptops use additional (dedicated) video cards. 

GPS or a global positioning system is a radio-based navigation system consisting of a network of multiple satellites. It uses a system of about 31 satellites located in space to provide accurate results. The satellites use microwave signals to interact with GPS devices.

Nowadays GPS is mostly found in smartphones, smartwatches, laptops, etc. Anyone can use this system to get the location on the map. This mainly helps in obtaining the exact location of connected devices or locations on the map in the form of latitude and longitude coordinates on the Earth. In addition, these devices provide information on vehicle speed, weather conditions, and many other pieces of data.

A Braille reader is an output device that primarily helps blind people read content (texts only) from a computer screen. The computer sends signals to the Braille reader, which converts them into Braille letters in the form of pins embossed on a flat surface. People with blindness can touch these pins and interpret the letters accordingly.

Braille readers are manufactured in different sizes, making them usable on different devices. Generally, they are found in the size of the computer keyboard.

Speech generating devices are output devices that help generate voice output from the text displayed on a computer screen. In particular, these devices convert text to speech. Additionally, whenever a user enters something from the keyboard and when the command is executed, SGD can help listen to the entered data as sound output. 

Speech generating devices are also known as speech synthesizers and voice output communication aids. These output devices are widely used in telephone exchanges and the treatment of blind and mute people.

A plotter is an output device that is almost identical to a printer. However, it is primarily used to print vector graphics with high quality. Unlike a printer, a plotter has various advanced features and can also print on cardboard, film, fabric, and many other synthetic surfaces.

The plotter helps to produce large-size hardcopies of graphics or designs. It derives the design from the graphic card and then interprets the vector graphics. A plotter usually uses color pens to draw multiple lines between different points to create the entire design. Plotters are expensive compared to printers.

Note: Many more output devices are used on computers to fulfill specific objectives. Some other output devices include smart television (TV), computer output microfilm (COM), modem, a network card (NIC), digital camera, AirPods (also called earpods), and more.

This article covers more than 10 examples of output devices used for computers, including their names, pictures, and functions on each. The primary function of an output device is to retrieve data from a computer and convert it into a human-readable form because we cannot understand data in machine language.