CIE 0478 only Lesson 6
Input/Output Devices and Sensors
CIE names a long list of specific devices that candidates can be asked about by name. This lesson covers each one with its typical use, advantages and limitations.
Key Terms
Input device
Sends data into the computer (keyboard, mouse, scanner, sensor).
Output device
Sends processed data out (monitor, printer, speaker, actuator).
Sensor
A specialised input device that measures a physical quantity from the environment.
Devices
Named input devices
2D / 3D scanner
Captures a flat document or a solid object as digital data. 3D scanners are used in medicine and reverse engineering.
Barcode reader
Reads a 1D barcode, e.g. at supermarket checkouts. Fast, low error rate.
QR code reader
Reads 2D QR codes; stores far more data than a barcode (up to several thousand characters).
Digital camera
Captures still or moving images using a CCD or CMOS sensor.
Microphone
Converts sound waves into a digital audio signal.
Touch screen
Acts as both input and output. Resistive, capacitive and infrared variants exist with different precision and cost trade-offs.
Devices
Named output devices
Inkjet printer
Sprays liquid ink. Cheap to buy, expensive ink, good photo quality.
Laser printer
Uses toner and a heated drum. High speed, sharp text, cheaper per page.
3D printer
Builds a solid object layer by layer from a digital model. Used in prototyping and prosthetics.
Actuator
A motor or valve that converts an electrical signal into physical motion.
Speaker
Converts a digital audio signal back into sound waves.
LCD / LED screen
Displays the visual output of the computer.
Devices
Named sensors and their uses
Temperature
Greenhouses, central heating, fridges.
Pressure
Burglar alarms (under doormats), tyre-pressure monitors.
Light
Streetlight controllers, smartphone screen brightness.
Sound
Voice-activated assistants, security alarms.
Humidity / moisture
Greenhouses, weather stations, soil monitors.
pH
Aquariums, water-quality monitoring.
Motion / infrared
Burglar alarms, automatic doors.
Gas
Carbon-monoxide detectors, industrial safety.
Exam tip
CIE questions love to ask "name a sensor and describe one application". Memorise at least one concrete real-world use for each sensor type above.
Think Deeper
Beyond the basics
A school is buying one printer for the main office. The headteacher wants the cheapest option and is leaning towards an inkjet because the printer itself only costs 60 pounds. The IT lead disagrees. Build the IT lead's case: pick the better printer for the use case, justify the choice using cost-per-page, speed and longevity, and identify one situation where the inkjet would in fact be the right choice.
Better choice for a main office: a laser printer.
Justification:
- Cost per page: laser toner lasts much longer than inkjet cartridges. The headteacher's 60-pound saving disappears the first time someone replaces the ink.
- Speed: laser printers print pages per second, not per minute. A busy office printing class lists, letters and reports cannot afford to wait.
- Longevity: lasers handle high-volume daily printing for years. Inkjets are designed for occasional household use and will jam or wear out under office load.
When the inkjet would be the right choice: if the office mainly needed to print photographs, marketing leaflets or full-colour artwork. Inkjets reproduce continuous colour better than lasers.
Justification:
- Cost per page: laser toner lasts much longer than inkjet cartridges. The headteacher's 60-pound saving disappears the first time someone replaces the ink.
- Speed: laser printers print pages per second, not per minute. A busy office printing class lists, letters and reports cannot afford to wait.
- Longevity: lasers handle high-volume daily printing for years. Inkjets are designed for occasional household use and will jam or wear out under office load.
When the inkjet would be the right choice: if the office mainly needed to print photographs, marketing leaflets or full-colour artwork. Inkjets reproduce continuous colour better than lasers.
Compare
Input vs output vs sensor
| Category | Direction | Examples | Typical use |
|---|---|---|---|
| Input device | Human → computer | Keyboard, mouse, scanner, microphone, touchscreen | The user deliberately enters data |
| Output device | Computer → human | Monitor, printer, speakers, projector, actuator | The computer presents results to the user |
| Sensor | Environment → computer (no human) | Temperature, light, moisture, pressure, infra-red | The computer measures the world without a person involved |
Spot the difference
A microphone is an input device because a person speaks into it deliberately. A noise sensor on a road is a sensor because nobody is choosing to make a sound for the computer. Both convert sound to digital, but the role they play in the system is different.
Common Misconception
"A touchscreen is one device"
A touchscreen is two devices stacked together: an output device (the LCD or OLED display) and an input device (the touch-sensitive layer that detects fingers). The exam may ask you to identify both. Saying just "input" or just "output" misses half the marks.
Worked Exam Answer
A six-mark exam question with mark scheme
Question (CIE-style, 6 marks): A self-service supermarket checkout uses several input and output devices. Identify three appropriate input devices and three appropriate output devices, justifying each choice.
Mark scheme - one mark per device with valid justification, up to 6
- Barcode scanner (input): reads the product code from each item quickly and accurately.
- Touchscreen (input): lets the customer choose loose items (e.g. apples) and confirm payment.
- Card reader / NFC (input): reads the customer's debit card or phone for contactless payment.
- Touchscreen display (output): shows the running total, prompts and on-screen receipt.
- Speaker (output): plays prompts and beeps to alert staff when intervention is needed.
- Receipt printer (output): produces a paper receipt for the customer at the end.
Think Deeper
Beyond the basics
A school uses an inkjet printer for student work and a 3D printer in DT lessons. Both are output devices, but they share almost nothing else. Pick three concrete differences in how they receive data, what they produce and how they fail, and explain why one would be a poor substitute for the other.
1. Data format. Inkjet receives a 2D bitmap or PDF; 3D printer receives a 3D model converted into layered slicing instructions (G-code). Sending one format to the other device produces nothing useful.
2. What is produced. Inkjet prints a flat image on paper in seconds. 3D printer builds a physical solid object layer by layer over hours.
3. Failure modes. An inkjet failure (paper jam, low ink) wastes one sheet. A 3D-printer failure halfway through a long job wastes hours of machine time and the plastic filament for the entire object so far. The cost of "trying again" is completely different.
A 3D printer cannot replace an inkjet for printing essays, and an inkjet cannot replace a 3D printer for making prototypes. They are output devices for different problems.
2. What is produced. Inkjet prints a flat image on paper in seconds. 3D printer builds a physical solid object layer by layer over hours.
3. Failure modes. An inkjet failure (paper jam, low ink) wastes one sheet. A 3D-printer failure halfway through a long job wastes hours of machine time and the plastic filament for the entire object so far. The cost of "trying again" is completely different.
A 3D printer cannot replace an inkjet for printing essays, and an inkjet cannot replace a 3D printer for making prototypes. They are output devices for different problems.
Check Your Understanding
Q1. Which sensor would best detect a person walking past a security camera at night?
Infrared motion sensors detect the body heat of a moving person.
Q2. Give one advantage of a laser printer over an inkjet printer.
Laser printers excel at fast, high-volume text printing with low cost per page.
Q3. Why is a touch screen described as both an input and an output device?
It senses where the user touches (input) and shows the visual output (output).
CIE 0478 - Lesson 6
Input/Output Devices and Sensors
Starter activity
Lay out a tray of real devices (or photos) on each desk: a USB barcode scanner, a smartphone, a microphone, a thermometer, a smoke alarm, a printed photo. Ask students to sort them into "input", "output" and "both". Use the inevitable disagreements to draw out that touch screens, smartphones and games consoles are all input/output devices.
Lesson objectives
1
Distinguish input devices, output devices and sensors with named examples.2
Describe the typical use of each named CIE input device (scanner, barcode reader, QR reader, camera, microphone, touch screen).3
Compare laser, inkjet and 3D printers on cost, speed and use case.4
Match each named sensor type (temperature, pressure, light, sound, humidity, pH, motion, gas) to a real-world application.5
Justify the choice of a specific device or sensor for a given scenario. Key vocabulary
input deviceoutput devicesensorbarcode readerQR code2D scanner3D scannerinkjetlaser printer3D printeractuatortouch screeninfrared
Discussion questions
Why is a touch screen counted as both input and output? Name another device that is both.
For each room in a house, which sensor would be most useful and why?
3D printers are now affordable for schools. What are the pros and cons of giving students free access?
Exit tickets
Name two named input devices and describe a typical use of each. [4 marks]
Compare an inkjet printer with a laser printer for an office. [3 marks]
A greenhouse needs to monitor air temperature, soil moisture and light. Name a suitable sensor for each. [3 marks]
Homework suggestion
Design the input and output devices for a brand-new self-checkout machine in a supermarket. List every input device, output device and sensor needed, justify each choice and produce a labelled diagram. Include at least one sensor that prevents misuse (e.g. theft or scanning the wrong item).
Classroom tools