Input and Input Devices

Short answer

• Input is data and instructions entered into a computer system, and an input device is any piece of hardware that collects that data and sends it to the computer for processing. Common input devices include keyboards for text and commands, mice and other pointing devices for selecting and moving items on screen, touch screens for direct tapping and gestures, microphones for voice and sound, scanners and barcode readers for turning printed material and codes into digital data, cameras for still images and video, and sensors for measurements such as temperature, light, motion, and pressure. Input differs from output: input goes into the system, while output, such as a picture on a monitor or sound from speakers, comes out of the system after processing. Some devices, notably touch screens, do both jobs. After input arrives, software called a driver helps the operating system interpret the signals, the processor and programs act on the data, and the result is stored, displayed, or sent onward as output.

Introduction

Every computer task starts the same way, with something going in. A person types a sentence, taps a screen, speaks a command, scans a ticket, or walks past a sensor. None of that becomes useful until a computer receives it, understands it as data, and acts on it. The hardware that makes that first step possible is called input hardware, and the individual pieces of hardware are called input devices.

This guide explains input and input devices in plain language, with enough detail to be useful for study and for everyday computer use. It covers what input means, the main categories of devices, how input is processed, how input differs from output, and how accessible input methods open computing to people who cannot use a standard keyboard or mouse comfortably. Where a technical term is needed, such as driver or sensor, it is explained when it first appears.

What Input Means in Computing

In computing, input is data or instructions supplied to a computer system so that it can process them. Data might be words in a document, numbers in a spreadsheet, a photograph, a spoken instruction, or a temperature reading. Instructions might be a command to open a file, save a document, move a character in a game, or turn a light on.

A useful way to picture this is the input, process, output cycle, often shortened to IPO. First, input enters the system. Second, the system processes it, which means it carries out calculations, comparisons, sorting, searching, or other operations according to the program in use. Third, the system produces output, which might be text on a screen, a printed page, a sound, a stored file, or a physical action such as a motor moving. Storage sits alongside this cycle, because input and results often need to be kept for later use.

Two points deserve emphasis. First, a computer can only process what it has been given or what it has collected. If the input is incomplete, unclear, or wrong, the output will usually reflect that problem, no matter how powerful the computer is. Second, input does not have to come from a person typing at a desk. It can come from another machine, from a network, from a file, or from the physical environment through a sensor. A weather station that records temperature every hour, a shop till that reads a barcode, and a phone that records your voice are all collecting input, even though no one is typing in those moments.

Categories of Input Devices

Input devices are often grouped by what kind of data they collect and how the user interacts with them. These groups overlap, and many modern devices combine more than one kind of input, but the categories below give a practical starting point.

Text input devices enter characters, words, and commands. The keyboard is the classic example, joined by on screen keyboards and handwriting recognition on phones and tablets.

Pointing devices let a user indicate a position or select an item on screen. The mouse is the best known example, joined by trackpads, trackballs, styluses, and joysticks used as pointing tools.

Touch input devices accept direct contact with a screen or surface. Touch screens, touchpads, and graphics tablets belong here. They are popular because the user points at the thing itself, rather than moving a separate pointer.

Audio input devices capture sound. Microphones are the main example, used for calls, recordings, voice commands, and dictation.

Image and document input devices turn visual material into digital data. Scanners, digital cameras, and webcams belong here, along with barcode and QR code readers that read coded patterns rather than full pictures.

Sensor input devices measure the physical world. Temperature sensors, light sensors, motion sensors, pressure sensors, and proximity sensors collect readings automatically, without a person entering each value by hand.

Control and game input devices translate physical movement into commands for software, especially games and simulations. Game controllers, joysticks, steering wheels, and motion controllers belong here, although many of them also work as general pointing or selection tools.

The Keyboard: Text, Numbers, and Commands

The keyboard remains the main way most people enter text into a computer. A standard keyboard has letter keys, number keys, punctuation keys, and special keys. Letter and number keys enter characters. Modifier keys, such as Shift, Control, and Alt, change what another key does when pressed at the same time. Function keys and shortcut combinations let a user carry out commands, such as copying, pasting, saving, or switching between programs, without reaching for a mouse.

Most desktop keyboards use a QWERTY layout, named for the first six letters on the top row of letter keys. Other layouts exist for other languages and for particular needs, including layouts designed to reduce finger travel. The layout matters less for understanding input than the principle behind it: each key press is an event. When you press a key, the keyboard sends a signal that identifies that key. The operating system and the program in use then decide what that signal means in context, whether it is a letter in a document, a number in a spreadsheet cell, or a shortcut that triggers a command.

Keyboards come in many physical forms. Desktop keyboards are separate units connected by cable or wireless link. Laptop keyboards are built into the machine and are usually more compact. On screen keyboards appear on a touch display when text entry is needed, and they send the same kind of key events even though there is no physical key to press. Braille keyboards and other adapted keyboards use a different key arrangement to suit a particular user, but the job is the same: turn a deliberate action into characters and commands a program can use.

The Mouse and Other Pointing Devices

A mouse is a pointing device. Moving it across a surface moves a pointer, usually called a cursor, on the screen. Pressing a button selects, opens, drags, or activates whatever is under the pointer. A scroll wheel, where fitted, moves a page up or down without moving the pointer itself. The idea is simple, and that simplicity is part of its success: the user does not need to memorize a command to point at something. The user points.

The computer mouse was invented in 1963 and 1964 by Douglas Engelbart at the Stanford Research Institute, as part of work on better ways to point at and select items on a display screen. Britannica records that the early mouse had a carved wood casing and just one button, and that Engelbart and his colleague William English later refined a range of input devices that became common, including joysticks, light pens, and trackballs. Before such devices, controlling a computer often meant laborious keypunch cards or manually set switches, and results often had to be printed before they could be viewed. The mouse, together with the graphical user interface, helped make direct manipulation normal: you see an object on screen, you point at it, and you act on it.

Other pointing devices solve the same problem in different settings. A trackpad, common on laptops, senses finger movement on a flat surface and turns it into pointer movement, with taps acting as clicks. A trackball keeps the ball in place while the user rolls it with fingers or thumb, which suits a small desk or a user who cannot move an arm freely across a surface. A stylus is a pen shaped tool used on a touch screen or graphics tablet for writing, drawing, and precise selection. A joystick moves in several directions from a central position and is used for pointing in some systems and for control in games and simulations.

Touch Input: Tapping, Swiping, and Gestures

Touch input lets a user interact directly with what is on screen. Instead of moving a separate pointer, the user touches the item itself: a button, a photo, a map, or a word. Common touch actions include tapping to select, double tapping to open or zoom, swiping to move through a list or page, pinching to zoom in or out, and dragging to move an item. Many devices also recognize multi touch, where two or more fingers act at once, for example to rotate an image or to zoom with a pinch gesture.

A touch screen is both an input device and an output device. The screen displays text, images, and controls, which is output. When the user touches the screen, the device detects the position and movement of the touch and sends that information to the system as input. That combination is why phones, tablets, self service kiosks, ticket machines, and many point of sale systems use touch screens: the display and the control are the same surface, so there is nothing extra to learn or carry.

Touch input has clear advantages. It is intuitive for beginners, it works well in a small space, and it suits tasks such as choosing from a menu, signing a delivery screen, or exploring a map. It also has limits. A finger is wider than a mouse pointer, so very small targets are harder to hit accurately. Long typing on a flat glass surface can be slower and more tiring than typing on a physical keyboard for many people. Screens also collect fingerprints and smudges, and touch input can be difficult in wet conditions, with gloves, or for users who cannot press precisely. Those limits explain why many larger devices offer both touch and a keyboard or pointer, rather than touch alone.

Voice and Audio Input

Voice input turns spoken words into data a computer can use. A microphone captures sound waves and converts them into electrical signals, which are then digitized, meaning converted into numbers, so software can process them. That software may record the sound for playback, as in a voice note, transcribe speech into text, as in dictation, or recognize commands, as in a voice assistant that responds to a spoken instruction.

Voice input is valuable because it frees the hands and eyes. A driver can ask for directions without looking away from the road, a person cooking can set a timer without touching a screen with wet hands, and a person with limited mobility can control a device by speaking. It is also useful for people who find typing slow or painful, and for entering text that is awkward to type on a given keyboard.

Voice input also has limits that are worth stating plainly. Background noise can confuse recognition. Accents, unusual names, and specialized vocabulary can be misheard. Privacy matters too, because a microphone may pick up nearby conversation, and voice data sent to a remote service raises questions about storage and use that typed input does not raise in the same way. For those reasons, voice input works best as one option among several, with a visible way to correct mistakes and a clear way to turn the microphone off.

Scanners, Readers, and Cameras

Scanners and readers turn material from the physical world into digital data without a person retyping it. That single idea covers a wide range of devices, and each one suits a different kind of source material.

A flatbed scanner copies a document or photograph placed on a glass plate. Light shines on the page, a sensor detects the reflected light, and the result is a digital image that can be viewed, edited, searched with text recognition software, or stored. Handheld scanners work on a similar principle, but the user moves the scanner across the document. Three dimensional scanners use reflected light or laser measurement to build a digital model of an object, which can then be examined, shared, or used with manufacturing software.

Barcode readers and QR code readers are specialized scanners. A barcode reader reads the pattern of bars on a product label and looks up the associated product code in a system, which is why shop checkouts are faster and less error prone than typing each price by hand. A QR code reader reads a square pattern that can hold a web address, a ticket reference, or other short data. Passport scanners at airports, ticket scanners at venues, and parcel scanners in delivery networks all use the same idea: read a code quickly, match it to a record, and avoid manual entry.

Digital cameras and webcams are also input devices. A digital camera captures still images or video as digital data that can be stored and edited. A webcam captures live video for calls, meetings, and recordings. The quality of the result depends on the sensor, the lens, and the light, but the input principle does not change: light is captured and digitized so software can use it.

Sensors: Input Without Typing

Sensors are input devices that measure the environment and report readings automatically. A temperature sensor reports how hot or cold a place is. A light sensor reports brightness. A motion sensor reports movement in front of it, as in an automatic door. A pressure sensor reports force or weight. A proximity sensor reports whether an object is near, as when a phone screen turns off during a call. A humidity sensor reports moisture in the air. Each sensor converts a physical quantity into an electrical signal, which is then digitized and sent to a system as data.

Sensors matter because they allow input without a person watching and typing every value. A thermostat can read room temperature and adjust heating without anyone entering a number. A fitness tracker can count steps and measure heart rate through the day. A factory system can monitor vibration, temperature, and pressure to warn of a fault before it causes damage. A farm system can read soil moisture and decide when to water. In each case, the human role shifts from entering data to deciding what should happen when the data crosses a threshold.

Sensors also raise design questions that typing does not. A sensor reading can be noisy, meaning it jumps around even when the real value is stable, so software often smooths or averages readings. A sensor can fail, drift out of calibration, or be placed in the wrong spot, and the system may act on a wrong reading without a person noticing. Good sensor design therefore includes checking, calibration, and sensible defaults, such as asking for confirmation before an automatic action that is hard to undo.

How Input Is Processed, Step by Step

Understanding what happens after input arrives makes the whole system easier to reason about, and it helps explain common problems such as delay, missed keystrokes, and devices that stop working.

First, the device detects an action or a measurement. A key is pressed, a finger touches a screen, a microphone diaphragm vibrates, a sensor registers a change, or a scanner reads a pattern. The device turns that physical event into an electrical signal.

Second, the signal is digitized where needed and packaged as data. For a keyboard, that package identifies the key and whether it was pressed or released. For a mouse, it reports movement and button state. For a microphone, it is a stream of digitized sound samples. For a touch screen, it reports touch position, movement, and pressure where available.

Third, the operating system receives the data, usually through a driver. A driver is software that knows how to talk to a particular kind of hardware and translate its signals into a standard form programs can use. Without the right driver, a device may be detected but not understood, which is why a newly connected device sometimes needs driver software before it works properly.

Fourth, the active program acts on the input according to its own rules. A word processor inserts a character. A browser follows a link. A game moves a character. A thermostat program compares a temperature reading with a target and decides whether to switch heating on or off. If the input is a command, the program carries it out. If it is data, the program stores it, displays it, transforms it, or sends it onward.

Fifth, the result becomes output or stored data. Text appears on screen, a file is saved, a message is sent, a motor moves, or a record is updated. That output may then prompt further input, and the cycle repeats.

Input Versus Output, and Devices That Do Both

Input and output are easy to confuse because many devices sit on a desk together and many tasks involve both in quick succession. The test is direction. If data or instructions are going into the system, that is input. If results are coming out of the system in a form a person or another machine can use, that is output.

A keyboard is input only in normal use: it sends characters and commands in. A monitor is output only in normal use: it displays results. A printer is output: it produces a paper copy. Speakers are output: they produce sound. A mouse is input: it sends pointer movement and clicks in. A microphone is input: it sends sound in.

Touch screens, headsets with microphones, network cards, modems, and storage drives that both read and write blur the line, and they are best described as bidirectional or combined devices. A touch screen displays output and accepts input on the same surface. A network card sends data out and receives data in. A headset plays output through its earpieces and captures input through its microphone. Naming both directions avoids the common study mistake of forcing every device into one box.

Accessibility: Input Methods for Different Needs

Input design matters most for people who cannot use a standard keyboard and mouse in the usual way, whether because of vision, hearing, movement, or cognitive needs, or because of a temporary situation such as an injury or a broken arm. Accessible input is not a separate topic from ordinary input. It is the same principle applied more carefully: offer more than one way to enter the same data and commands.

Keyboard only operation is a foundation. Guidance from the World Wide Web Consortium, in its Web Content Accessibility Guidelines, states that functionality should be available from a keyboard, and explains that if all functionality can be achieved using the keyboard, it can also be accomplished by speech input, which creates keyboard input, by mouse use through on screen keyboards, and by a wide variety of assistive technologies that create simulated keystrokes. In practical terms, that means a person who cannot use a mouse should still be able to reach every control, enter text, and complete a task using keyboard input or a device that emulates a keyboard.

Switch devices take this idea further. A switch may be a single button that a user presses with a hand, foot, head movement, or another reliable movement. Scanning software then steps through options on screen, and the user presses the switch to select the highlighted option. Sip and puff devices work on a similar principle, using breath through a tube to send signals. Eye tracking systems follow gaze to select items on screen. Head tracking systems turn head movement into pointer movement. Voice control lets a user speak commands and dictate text. On screen keyboards, word prediction, and sticky keys, which allow modifier keys to be pressed one at a time rather than held together, all reduce the physical effort of typing.

Good accessible input design also respects timing and feedback. Controls should not require very fast or precisely timed presses unless the task genuinely needs them. Every action should give clear feedback, so the user knows what was selected or entered. Error messages should explain what went wrong in plain language and how to fix it. These practices help everyone, not only users of assistive technology, because they reduce mistakes and make correction easier.

Frequently Asked Questions

What is the difference between input and input devices?

Input is the data and instructions that enter a computer system. An input device is the hardware that collects that data and sends it into the system. Typing the words of an essay is input. The keyboard you type them on is the input device. A temperature reading is input. The sensor that measures it is the input device.

What are the most common input devices?

The most common input devices for everyday computing are the keyboard, the mouse, the touch screen, the microphone, the webcam, and the scanner. Which one counts as most common depends on the device: a desktop setup centers on keyboard and mouse, a phone centers on touch screen, microphone, and cameras, and a shop till centers on keyboard, barcode reader, and touch screen. Sensors are also extremely common, but they are often hidden inside phones, cars, appliances, and buildings, so they are noticed less.

Is a touch screen an input device or an output device?

A touch screen is both. It is an output device because it displays text, images, and controls. It is an input device because it detects touches and gestures and sends them to the system as data. For that reason, touch screens are often called bidirectional devices, meaning data flows in both directions.

Is a printer an input device?

No. A printer is an output device. It takes digital data from a computer and produces a paper copy. A device that looks similar but works in the opposite direction, a scanner, is an input device, because it turns a paper document into digital data. A combined printer and scanner unit contains both: the printer part is output, and the scanner part is input.

How does a keyboard send input to a computer?

When you press a key, the keyboard sends a signal identifying that key to the computer. A driver helps the operating system interpret the signal, and the active program decides what it means in context, such as inserting a letter, entering a number, or carrying out a shortcut command. When you release the key, a further signal marks the end of that key event. The same principle applies to an on screen keyboard, except that the key press is a tap on a displayed key rather than a physical movement.

Can you use a computer without a mouse?

Yes. Many tasks can be done with a keyboard alone, using shortcuts, menus, and tab navigation to move between controls. Touch screens, voice control, switch devices, and eye tracking also provide alternatives to a mouse. Accessibility guidance emphasizes keyboard operation precisely because keyboard input can be produced by many different assistive technologies, so keyboard support opens a system to a wider range of users.

What is an example of input in everyday life?

Everyday examples are everywhere once you look for them. Tapping a card reader to pay, speaking to a voice assistant, scanning a parcel barcode, unlocking a phone with a fingerprint or face scan, adjusting a thermostat, and pressing a doorbell camera button all send input into a system. In each case, a device collects data from a person or the environment, and software acts on it.

Sources & references

• Encyclopaedia Britannica, Douglas Engelbart: invention of the computer mouse in 1963 and 1964, early wood casing and single button, later refinement of joysticks, light pens, and trackballs with William English, and the shift from keypunch cards and manual switches to direct manipulation.
• World Wide Web Consortium, Web Content Accessibility Guidelines, Understanding Guideline 2.1: Keyboard Accessible: keyboard operation as a foundation for speech input, on screen keyboards, and assistive technologies that create simulated keystrokes.
• Study Rocket, Input and Output, GCSE Computer Science Eduqas Revision: definition of input devices as hardware that feeds data and instructions into a system, examples including keyboards, mice, touch screens, barcode scanners, and microphones, and touch screens as bidirectional devices.