What you'll learn
Input devices get data into a computer; output devices present the results to people or act on the world. This guide covers manual input devices such as keyboards, mice and touchscreens; automatic data capture devices such as barcode readers, OCR, OMR, MICR and RFID; sensors and actuators in control systems; and the main output devices — screens, printers of different kinds, plotters, speakers and 3D printers. Throughout, the focus is on choosing the right device for a task and justifying that choice, which is how most marks in this topic are earned.
Exam questions typically describe a situation — a supermarket, a bank, a school marking answer sheets, a greenhouse — and ask which device is most suitable and why. Learn each device's main advantage and main limitation so that you can compare them quickly.
Key terms and definitions
Input device — Hardware used to enter data into a computer.
Output device — Hardware used to present information from a computer or carry out a physical action.
Direct data entry — Capturing data automatically, without a person typing it, such as scanning a barcode.
Barcode reader — Reads the pattern of black and white bars on a product to identify it.
OCR (optical character recognition) — Software and a scanner that convert printed or typed text into editable text.
OMR (optical mark recognition) — Reads marks made in set positions on a form, such as multiple-choice answer sheets.
MICR (magnetic ink character recognition) — Reads characters printed in magnetic ink, as along the bottom of bank cheques.
RFID (radio-frequency identification) — Reads data from tags using radio waves, without line of sight.
Sensor — A device that measures a physical quantity, such as temperature or light, and sends a signal to a computer.
Actuator — An output device in a control system that causes movement or change, such as a motor or valve.
Data logging — Using sensors to record readings automatically over time.
Core concepts
Manual input devices
Keyboard — the standard way to enter text and commands. Fast for skilled typists, but slow for others and can contribute to repetitive strain injury. Concept keyboards (with symbols instead of letters) are used in fast-food tills.
Mouse, touchpad and trackerball — pointing devices used to select items on screen. A trackerball stays still and is useful where space is limited or for users with limited hand movement.
Touchscreen — both an input and an output device. Intuitive and quick, with no separate keyboard or mouse needed, so it suits public kiosks, phones and tablets. Screens can get dirty and are less accurate than a mouse for detailed work.
Microphone — captures sound for recording, calls and voice recognition. Voice input is hands-free and helps users who cannot use their hands, but accuracy drops with background noise and unfamiliar accents.
Digital camera and webcam — capture images and video directly as digital files.
Scanner — converts printed images and documents into digital images. Combined with OCR software, it can turn a printed page into editable text.
Graphics tablet — a flat pad and stylus used by artists and designers. It allows natural, pressure-sensitive drawing that a mouse cannot match.
Automatic data capture
Automatic methods are faster and far more accurate than typing, and they reduce staffing costs.
Barcode readers at supermarket checkouts identify products instantly; the computer looks up the price and updates stock levels. Errors in pricing usually come from the stored price being wrong, not the scan. Handheld scanners let staff scan bulky items without lifting them.
OMR is ideal for marking thousands of multiple-choice answer sheets or reading lottery tickets and registers. It only reads the position of marks, so it cannot read handwriting.
OCR converts the shapes of printed characters into text. It is used to digitise documents and to read car number plates in automatic number plate recognition (ANPR) systems. It can make mistakes with poor-quality print or unusual fonts.
MICR is used by banks for cheques. Magnetic ink is hard to forge and can be read even if the cheque is overwritten or slightly damaged, which is why banks still use it rather than ordinary barcodes.
RFID tags can be read from a distance without being visible, so they are used for contactless payment cards, stock tracking, library books, passports and pet microchips.
Chip-and-PIN and contactless card readers read data stored on bank cards; the PIN adds a second check that the card is being used by its owner.
Sensors, data logging and control
Sensors measure physical quantities: temperature, light, pressure, moisture, humidity, sound, motion (infrared), pH and gas levels. Most sensors produce an analogue signal, which is converted to digital before the computer processes it.
Data logging uses sensors to collect readings automatically at set intervals. It is used for weather stations, scientific experiments, hospital patient monitoring and environmental surveys. Its advantages are clear: readings can be taken continuously, day and night, in dangerous or remote places, at precise intervals, without human error or tiredness.
In a control system, a computer reads sensors, compares the readings with set values, and switches actuators to make changes. A greenhouse system reads a temperature sensor; if the temperature rises above the set value, the computer signals an actuator to open a window and turn on a fan. The sensor alone does nothing — it only measures. The decision is made by the processor comparing the reading with the stored target, and the action is carried out by the actuator. This continuous cycle of measuring, comparing and acting is called a feedback loop.
Output devices
Monitors display information on screen. Larger and higher-resolution screens show more detail.
Speakers and headphones produce sound for music, alerts and screen readers for visually impaired users.
Printers produce hard copy:
- Laser printers are fast and quiet with sharp text, so they suit high-volume office printing. They cost more to buy, but the cost per page is low.
- Inkjet printers are cheap to buy and good for colour photos, but slower, and ink is expensive per page, making them costly for heavy use.
- Dot matrix printers strike an inked ribbon. They are noisy and low-quality but can print multi-part carbon copies and continuous stationery, so they are still used for some invoices and in industrial settings.
Plotters draw large, highly accurate technical drawings, such as architectural plans and engineering designs, on large paper.
3D printers build solid objects layer by layer from plastic or other materials. They are used for prototypes, custom parts, medical implants and models.
Projectors display images on large screens for audiences.
Actuators, such as motors, valves, heaters and buzzers, are outputs in control systems.
Accessibility
ICT can help users with disabilities. Visually impaired users may use screen readers, speech output, Braille displays, large-key keyboards and screen magnification. Users with limited movement may use voice recognition, eye-tracking, trackerballs or switches.
Choosing devices: a checklist
When a question asks you to choose input or output devices, work through these factors:
- Volume and speed — how much data must be entered or printed, and how quickly? High volumes favour automatic capture and laser printers.
- Accuracy — automatic methods such as barcodes, OMR and sensors avoid typing errors.
- Environment — dusty, wet or outdoor locations may need rugged devices; noisy places make voice input unreliable; public kiosks need robust touchscreens.
- Users — their skills, age and any disabilities. Menus and touchscreens suit the public; specialist devices suit designers.
- Cost — both purchase price and running costs, such as ink, toner and maintenance.
- Output form — does the user need a screen display, hard copy, sound, a large drawing, a physical object or a physical action?
Applying even two or three of these factors to the scenario will make a justification specific rather than generic.
Devices working together
Real systems combine several devices. A supermarket checkout uses a barcode reader, keypad, card reader, screen, receipt printer and weighing scales. A car park uses ANPR cameras (OCR), barrier actuators, payment machines and display boards. An exam question may ask you to identify each device's role in such a system — say whether it is input or output and what it contributes.
Worked examples
Example 1: Marking answer sheets
A school must mark 2,000 multiple-choice answer sheets quickly and accurately. Which input method is most suitable? Justify your choice. (3 marks)
Answer: Optical mark recognition (1). It reads the position of pencil marks in boxes very quickly, so thousands of sheets can be processed in a short time (1), and it avoids the errors a person would make typing the answers by hand (1).
Example 2: Choosing a printer
A busy solicitors' office prints hundreds of pages of text documents every day. Which printer should it buy?
Answer: A laser printer. It prints quickly and quietly with sharp text, and its low cost per page makes it economical for high volumes. An inkjet would be cheaper to buy but expensive to run because of ink costs, and slower.
Example 3: Data logging in a hospital
Explain why a hospital uses sensors to record a patient's heart rate overnight rather than having a nurse take readings.
Answer: Sensors take readings continuously and at precise intervals throughout the night without tiring or forgetting. An alarm can sound immediately if the reading goes outside safe limits. This frees nurses for other tasks and removes the risk of human error in recording.
Example 4: Explaining a control system
A greenhouse uses a temperature sensor and a window motor. Describe how the system keeps the greenhouse at the right temperature.
Answer: The sensor measures the temperature and sends the reading to the computer. The computer compares it with the stored target. If it is too high, the computer sends a signal to the actuator to open the window; if it is too low, the window is closed. The process repeats continuously, forming a feedback loop.
Common mistakes and how to avoid them
- Calling a sensor an output device. Sensors are inputs. Actuators are outputs.
- Saying the sensor "decides" what to do. The processor makes the decision by comparing readings with stored values.
- Mixing up OCR and OMR. OCR reads characters (text); OMR reads marks in set positions.
- Choosing an inkjet for heavy office printing. Running costs make laser better for volume.
- Forgetting that touchscreens are both input and output.
- Giving a device without a reason. Always add the benefit in the context: speed, accuracy, cost, accessibility.
Exam technique for "Input and Output Devices"
- Use the structure device → feature → benefit in this situation. "A barcode reader scans products instantly, so queues move faster and pricing errors from typing are avoided."
- When comparing devices, give one advantage and one disadvantage of each, then decide.
- In control-system questions, describe the full loop: sensor reading → conversion → comparison with target → actuator → repeat.
- Do not write brand names; use the general device name.
Quick revision summary
- Manual input: keyboard, mouse, touchscreen, microphone, camera, scanner, graphics tablet.
- Automatic capture: barcode, OMR (marks), OCR (text), MICR (cheques), RFID (no line of sight), card readers.
- Sensors measure; data logging records over time; actuators carry out actions; the processor compares and decides.
- Printers: laser (fast, cheap per page), inkjet (cheap to buy, good colour, costly ink), dot matrix (multi-part copies).
- Plotters for large accurate drawings; 3D printers for prototypes and parts.
- Always justify a device choice with a benefit linked to the scenario.