Output Devices
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- Advantages: Immediate display of results; can show colour, video, and interactive content; no ongoing consumable costs such as paper or ink.
- Disadvantages: Output disappears once the device is switched off; cannot be physically handed to another person; can cause eye strain with prolonged use.
- Inkjet printers spray tiny droplets of liquid ink onto paper and are popular for home use because they produce high-quality colour output at a relatively low purchase cost, although the ink cartridges can be expensive to replace.
- Laser printers use a laser to transfer toner powder onto paper, which is then fused using heat. Laser printers are faster and more cost-effective for high-volume printing, making them common in offices and schools.
- Dot matrix printers use pins striking an inked ribbon and are still used in some businesses because they can print on multi-part carbon forms, such as invoices with several copies.
- Output device: hardware used by a computer to present the results of processing.
- Soft copy: output displayed temporarily on a screen.
- Hard copy: a permanent, physical version of output, usually on paper.
- Actuator: a device that converts an electrical signal into physical movement.
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Introduction to Output Devices
An output device is any piece of hardware that a computer uses to communicate the results of processing to the user or to another system. After data has been entered through an input device and processed by the central processing unit, the results must be presented in a form that people can understand, such as text, images, sound, or physical movement. Output can also be sent to another device or machine, for example when a computer sends a signal to control a robotic arm.
Output devices are commonly divided into those that produce a temporary, on-screen result known as soft copy, and those that produce a permanent, physical result known as hard copy. Choosing the correct output device depends on the type of output required, the audience, and the environment in which it will be used.
Monitors and Screens
A monitor, or visual display unit (VDU), is the most common output device and displays text, images, and video using technologies such as LCD (Liquid Crystal Display) and LED (Light Emitting Diode). Monitors produce soft copy output, meaning the result exists only while the computer is switched on and displaying it.
Printers
A printer produces a permanent, physical copy of output on paper, known as hard copy. There are several types of printer commonly used, each suited to different needs.
Plotters
A plotter is a specialised output device that draws images using one or more pens, and is used to produce large, precise line drawings such as architectural plans, engineering designs, and clothing patterns. Plotters can print on very large sheets of paper that would not fit through an ordinary printer.
Speakers and Headphones
Speakers and headphones convert electrical signals from the computer into sound waves that can be heard by the user. They are essential for multimedia applications, video conferencing, gaming, and assistive technologies such as screen readers, which read on-screen text aloud for visually impaired users.
Actuators
An actuator is a device that converts an electrical control signal from a computer into physical movement. Actuators are widely used in control and automation systems, such as opening a valve in a greenhouse irrigation system, moving a robotic arm on a production line, or unlocking an electronic door. Unlike a monitor or printer, an actuator's output is a mechanical action rather than something to be seen, heard, or read.
Multimedia Projectors
A projector takes the video output from a computer and projects an enlarged image onto a screen or wall, allowing a large audience to view the same content at once. Projectors are widely used in classrooms, lecture halls, and business presentations.
Choosing the Right Output Device
The correct output device depends on whether a permanent record is needed, how large the audience is, and whether the output needs to be seen, heard, read aloud, or converted into physical movement. For example, a school report card requires a printer to produce hard copy for parents to keep, a classroom presentation is best shown using a projector so the whole class can see it, and an automated factory process requires actuators to physically carry out actions based on computer instructions.
Key Terms to Remember
Braille Displays and Assistive Output
A braille printer, sometimes called an embosser, produces raised dots on paper that can be read by touch, allowing visually impaired users to access text output. A braille display works similarly but presents a single refreshable line of raised dots connected to a computer, updating as the user moves through a document. These devices show that output technology must sometimes be adapted for users who cannot rely on a visual display.
Screen readers work alongside speaker output to convert on-screen text into synthesised speech, reading out menus, buttons, and document content so that a visually impaired user can navigate a computer without needing to see the screen at all. This combination of software and speaker output is an important example of how output devices support accessibility.
3D Printers
A 3D printer is a specialised output device that builds a solid, three-dimensional object layer by layer, typically by depositing melted plastic or another material according to a digital design file. Unlike a traditional printer, which produces a flat image on paper, a 3D printer produces a physical model that can be held and used, and this technology is increasingly applied in engineering prototyping, medical modelling, and manufacturing small spare parts.
Control Output and Automation
In automated and control systems, output is not always intended for a human being at all. A computer controlling a greenhouse, for example, may send output signals to devices that open windows, switch on heaters, or start a watering system, based on readings taken from sensors. In this context, the "output" is a change made directly to the physical environment rather than something displayed, printed, or spoken, which highlights how broad the concept of output can be within computer systems.
Comparing Impact and Non-Impact Printers
Printers can also be classified as impact or non-impact. Impact printers, such as dot matrix printers, physically strike an inked ribbon against the paper to form characters, which makes them noisy but allows them to print through carbon paper to create several copies of a document at once, useful for delivery notes and receipts requiring a duplicate. Non-impact printers, such as inkjet and laser printers, form images without physically striking the page, making them quieter, faster, and capable of producing higher-quality graphics and colour output, though they cannot create carbon copies in the way impact printers can.
Environmental and Cost Considerations
When an organisation selects output devices, it must also weigh running costs and environmental impact alongside the initial purchase price. Laser printers, for example, have a higher upfront cost than inkjet printers but a lower cost per page when printing large volumes, making them more economical for busy offices. Reducing unnecessary printing by relying more on soft copy output, such as sharing documents on screen or by email, also reduces paper waste and environmental impact, which is an increasingly important consideration for schools and businesses alike.
Summary
Output devices allow a computer to present processed information to a user or to control another machine. Monitors and speakers provide immediate, temporary soft copy output, printers and plotters provide permanent hard copy output on paper, and actuators convert digital instructions into real-world physical movement. Selecting the appropriate output device depends on the nature of the task, the need for a permanent record, and the intended audience.
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