What are input devices in the context of Cambridge IGCSE Computer Science?

Input devices are hardware components used to enter data and instructions into a computer system. Common examples include keyboards, mice, scanners, and microphones. In the Cambridge IGCSE Computer Science curriculum, understanding input devices is crucial as they are the primary means by which users interact with computers.

How do output devices differ from input devices in computer systems?

Output devices are hardware components that convey information from a computer to the user or another device. Unlike input devices, which send data to the computer, output devices display, project, or produce the results of computer processing. Examples include monitors, printers, and speakers. In the Cambridge IGCSE syllabus, recognizing the role of output devices is essential for understanding how computers communicate results to users.

Why are input and output devices important in computer systems?

Input and output devices are vital because they facilitate interaction between the user and the computer system. Input devices allow users to provide data and commands, while output devices enable the computer to present processed information. This interaction is fundamental to the functionality of computer systems, making these devices a key topic in the Cambridge IGCSE Computer Science curriculum.

Can you explain the role of a touchscreen as both an input and output device?

A touchscreen serves as both an input and output device. It displays visual output like a monitor while allowing users to interact with the computer by touching the screen, similar to a mouse or keyboard. This dual functionality makes touchscreens versatile and increasingly common in modern devices. In the Cambridge IGCSE Computer Science course, understanding such multifunctional devices is important for grasping the evolution of computer hardware.

What factors should be considered when choosing input and output devices for a computer system?

When selecting input and output devices, consider compatibility with the computer system, the specific needs of the user, the environment in which the devices will be used, and the budget. For example, a graphic designer might need a high-resolution monitor and a graphics tablet, while a typist might prioritize a comfortable keyboard. The Cambridge IGCSE Computer Science curriculum encourages students to evaluate these factors to understand the practical aspects of hardware selection.

Why is "Confusing laser and inkjet printers" a common mistake in Input and Output Devices?

Why it happens: Both produce 2D prints; students lump them together. How to avoid it: **Laser**: dry powder (toner) fused to paper using a heated drum; fast, sharp, high-volume. **Inkjet**: liquid ink sprayed through nozzles; cheaper hardware, better photo quality, slower, ink dries up.

Why is "Naming a 'sensor' as the input WITHOUT specifying which type" a common mistake in Input and Output Devices?

Why it happens: Students write 'a sensor' as if it's specific. How to avoid it: Always name the SPECIFIC type — temperature, light, moisture, pH, motion, infrared, pressure. Mark scheme rejects 'sensor' on its own when a specific role is required. Source: 0478 Examiner Reports 2022-2024

Why is "Calling a motor an 'output device' rather than an actuator" a common mistake in Input and Output Devices?

Why it happens: Both terms apply at GCSE level. How to avoid it: Both are technically right but ACTUATOR is the precise term in control systems. Use it when a question specifies a process-control context (motor, pump, valve, heater).

Why is "Saying 3D printers print 'in 3D ink'" a common mistake in Input and Output Devices?

Why it happens: Treating 3D printing as a fancier inkjet. How to avoid it: There is no 3D ink. The material is filament/plastic/resin/metal powder, deposited layer-by-layer. ADDITIVE manufacturing builds up; 2D printing only places material on the surface.

HardwareCambridge IGCSE Computer Science (0478)

Input and Output Devices

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Input and Output Devices Study Notes — Cambridge IGCSE Computer Science 0478 (2026-2028 syllabus)

How data gets in and out of a computer. The full set of common input devices (keyboards, mice, scanners, sensors, cameras, microphones), output devices (monitors, printers, speakers, actuators), the technologies behind touch screens and 3D printers, and what 'sensor' really means in a control system.

What you’ll learn

Mapped to the Cambridge IGCSE 0478 syllabus (2026-2028).

1.4.1 — Identify common input devices and their use.
1.4.2 — Identify common output devices and their use.
1.4.3 — Describe touch-screen technologies (resistive, capacitive, infrared).
1.4.4 — Describe how a 3D printer works.
1.4.5 — Describe sensors and actuators in process-control systems.

Common input devices

Anything that sends data INTO the computer.

An input device sends data into the computer for processing. Cambridge expects you to know all of these:

Keyboard — typing, command input, navigation. Universal but slow for non-text input.
Mouse / trackpad — pointing, selecting. Suited to graphical interfaces.
Microphone — captures sound (speech, voice commands, recordings).
Digital camera / webcam — captures still images and video.
Scanner (flatbed, document, 3D) — converts physical originals into digital images.
Barcode reader — reads 1D black-and-white bar patterns. Used in retail, libraries, warehouse picking.
QR code reader — reads 2D matrix patterns. Holds far more data than a barcode (URLs, contact info).
OCR / OMR — optical CHARACTER recognition (turns scanned text into editable text); optical MARK recognition (reads pencil marks on multiple-choice forms).
Touch screen — input AND output in one (see touch-screen section).
Sensors — capture real-world quantities (covered separately).

Cambridge tip. When a question asks for 'an input device', name a SPECIFIC device with a CLEAR PURPOSE — not 'a sensor' or 'a button'.

Know the full list and what each is for.
Be specific — 'pressure sensor', not 'a sensor'.
Touch screens count as both input and output.

Common output devices

Monitors, printers, speakers, actuators.

An output device receives data from the computer and presents it to the user or environment.

Visual outputs.

Monitors — LCD, LED-backlit LCD, OLED. Higher PPI = sharper image.
Projectors — fire light onto a surface for large-scale viewing.
Touch screens as displays (input + output).

Print outputs.

Inkjet printer — sprays liquid ink through nozzles. Cheap, photo-quality, slow, ink dries.
Laser printer — fuses dry toner to paper using a heated drum. Fast, sharp, high-volume; higher upfront cost.
3D printer — additive manufacturing (full section below).

Audio outputs.

Speakers / headphones — convert digital audio to sound waves via a digital-to-analogue converter (DAC).

Actuators. In process-control systems, the 'output device' is often an actuator that performs a PHYSICAL action — motors, valves, heaters, pumps, hydraulic rams. Specify which.

Cambridge tip. Mark schemes distinguish OUTPUT (information to a user — text, sound, image) from ACTUATOR (an action in the physical world). Use the right term for the context.

Know inkjet vs laser differences (mechanism + use case).
Actuators are output components in control systems.
Speakers convert digital → analogue audio.

Touch-screen technologies

Three families: resistive, capacitive, infrared.

Three different touch-screen technologies appear in 0478 questions.

Resistive. Two flexible conductive layers separated by a tiny gap. When you press, the layers touch and complete a circuit at that point — coordinates derived from voltage drop.

Pros: Works with any object (gloved finger, stylus). Cheap to manufacture.
Cons: Less responsive — needs firm pressure. Layers wear out. Doesn't support multi-touch well.

Capacitive. A glass surface coated with a transparent conductor stores a small electric charge. A bare fingertip is conductive; touching changes the local charge field, which sensors at the corners detect.

Pros: Very clear image; supports multi-touch (pinch, swipe, rotate); durable.
Cons: Only works with conductive objects (skin, special styluses). Doesn't work through gloves.

Infrared. A grid of infrared LEDs projects beams across the screen surface; receivers detect when an object (any object) breaks the beams.

Pros: Very durable (no surface layer to wear). Works with anything (gloves, stylus, finger). Can be made very large.
Cons: Expensive. Affected by direct sunlight, dirt or water on the bezel.

Where each is used. Resistive: industrial control, payment terminals where styluses are used. Capacitive: smartphones, tablets, modern laptops. Infrared: large interactive whiteboards, digital signage, ATMs.

Resistive — pressure, any object, less sensitive.
Capacitive — charge, multi-touch, skin only.
Infrared — beam grid, durable, expensive.

See the full worked example for input and output devices →

How a 3D printer works

Slice a 3D model, print layer by layer, fuse to make a solid.

A 3D printer builds a physical object from a digital design using additive manufacturing — adding material layer by layer rather than removing it (like CNC machining).

The process:

CAD model. A 3D model is created using computer-aided design software, exported as a standard file (e.g. .stl).
Slicing. Slicer software divides the model into thin horizontal layers (each a 2D cross-section the printer can build).
Printing. The printer extrudes material (commonly thermoplastic filament — PLA, ABS — but also resin, metal powder, even concrete) along the X-Y plane while the bed lowers (or the head rises) one layer at a time.
Bonding. Each new layer fuses to the one below as it cools, building a solid 3D shape.
Post-processing. Supports may be removed; surfaces sanded; resin parts UV-cured.

Real-world uses.

Prototyping (rapid iteration before mass production).
Custom medical implants (hip joints, hearing-aid shells, dental crowns).
Hobbyist parts and replacement components.
Food (chocolate, pasta — at the novelty end).
Construction (whole-house concrete printing in some pilots).

Cambridge tip. Top-band candidates use the word ADDITIVE explicitly. Mark scheme rewards 'layer by layer', 'CAD model', 'extruded', and 'thermoplastic / filament' as a chain.

Additive: builds up, doesn't carve away.
CAD → slicer → layer-by-layer print → fuse.
Material varies (filament, resin, metal, concrete).

See the full worked example for input and output devices →

Sensors in control and monitoring systems

Capture real-world quantities; computer compares to thresholds; actuators respond.

Sensors are input devices that capture physical quantities from the real world and convert them into digital signals the computer can process. Common sensors:

Sensor	Measures	Example use
Temperature	Heat	Heating control, glasshouse, fridge alarms
Light	Brightness	Auto-headlights, street lighting, photography
Pressure	Force per area	Burglar alarm under floor, tyre pressure
Motion / PIR	Movement / body heat	Intruder alarm, automatic lights
Sound	Sound level	Voice control, noise monitoring
Moisture / humidity	Water content	Glasshouse irrigation, hygrometers
pH	Acidity	Pool chemistry, hydroponics
Gas (CO, CO₂, smoke)	Air composition	Fire alarm, ventilation control
Infrared	Heat / proximity	Touchless taps, security

The control loop.

Sensor takes a reading.
Reading is converted to digital (via an ADC if the sensor is analogue).
Microprocessor compares the value to pre-set THRESHOLDS.
If outside the range, the microprocessor sends a signal to an ACTUATOR (motor, valve, heater) to bring it back.
Loop repeats.

Cambridge tip. Mark schemes love this five-step chain. Memorise it and adapt to whatever scenario the question gives (greenhouse, fish tank, oven, automatic doors, smart home).

Always specify the SENSOR TYPE.
Sensor → ADC → microprocessor → compare → actuator.
Process control = feedback loop; readings repeat continuously.

See the full worked example for input and output devices →

How it’s examined

Hardware appears on every Paper 1. Most-tested questions: process-control scenarios using sensors (6 marks), touch-screen comparisons (6 marks), 3D printing (6 marks), input/output device matching (4-8 marks). Examiner reports highlight that students lose marks for vague answers ('a sensor', 'a printer') instead of specific devices.

Sources: Cambridge IGCSE Computer Science 0478 syllabus (2026-2028); 0478 Examiner Reports 2022-2024; 0478/12 May/Jun 2024 question paper and mark scheme. Last reviewed 2026-05-09.

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Step-by-step worked examples — Input and Output Devices

Step-by-step solutions to past-paper-style questions on input and output devices, written exactly the way a tutor would explain them at the board.

1Compare touch-screen technologies (6 marks)
Extended• Adapted from 0478/12 May/Jun 2024 Q4• touch, input
Question
Three types of touch screen are: resistive, capacitive and infrared. For each, give one advantage and one disadvantage. (6 marks)
Step-by-step solution
1. Step 1
  Resistive (2 marks). ADVANTAGE: works with any object including a stylus or gloved finger; cheap to make. DISADVANTAGE: less sensitive — has to be pressed firmly; durability is poor (the layers wear out).
2. Step 2
  Capacitive (2 marks). ADVANTAGE: high image clarity; supports multi-touch (pinch, swipe). DISADVANTAGE: only works with bare skin or special styluses — doesn't work with gloves or any non-conductive object.
3. Step 3
  Infrared (2 marks). ADVANTAGE: very durable; works with any object (gloves, stylus, finger); large sizes possible. DISADVANTAGE: more expensive; can be affected by dirt, water or strong sunlight.
Answer
Resistive — cheap, any object, but firm press; capacitive — clear, multi-touch, but bare skin only; infrared — durable, any object, but expensive and sensitive to dirt.
2How a 3D printer works (6 marks)
Extended• printer, 3d
Question
Describe how a 3D printer creates a physical object from a digital design. (6 marks)
Step-by-step solution
1. Step 1
  Design (1 mark). A 3D model is created using CAD (computer-aided design) software, then exported (typically as an .stl file).
2. Step 2
  Slicing (1 mark). The model is divided into thin horizontal layers by 'slicer' software. Each layer becomes a 2D cross-section the printer can build.
3. Step 3
  Printing — additive process (2 marks). The printer builds the object up LAYER BY LAYER. The print head moves in the X-Y plane while extruding heated material (commonly thermoplastic filament — PLA, ABS); the bed (or head) drops slightly between layers.
4. Step 4
  Bonding and cooling (1 mark). Each new layer fuses to the previous one as the material cools, building the solid 3D shape.
5. Step 5
  Post-processing (1 mark). Finished objects may need supports removed, sanding or curing depending on the material and method.
Answer
CAD model → sliced into 2D layers → printer extrudes material layer-by-layer → layers fuse → object built additively from the bottom up.
Examiner tip
The keyword is ADDITIVE. 2D printing is reproductive (ink on paper); 3D printing builds layer by layer. Mark scheme rewards both 'layer' and 'additive'.
3Sensors in a smart glasshouse (6 marks)
Core• sensors
Question
A computer-controlled glasshouse uses sensors to manage temperature, soil moisture and light. Identify the three sensors and describe how the system uses each. (6 marks)
Step-by-step solution
1. Step 1
  Temperature sensor (2 marks). Measures air temperature. The microprocessor compares the reading to a set range; if too hot it opens vents / activates a fan; if too cold it activates a heater.
2. Step 2
  Moisture / humidity sensor (2 marks). Measures soil moisture (or air humidity). If moisture falls below the threshold, the microprocessor activates a sprinkler / drip-irrigation valve until the threshold is reached.
3. Step 3
  Light sensor (2 marks). Measures light intensity. Below threshold, grow lights are switched on; above threshold (excessive sunlight), shades / blinds may be deployed.
Answer
Temperature → vents/fans/heater. Moisture → sprinklers. Light → grow lights / shades. All readings are compared against thresholds; the microprocessor sends actuator signals to maintain conditions.

Key Definitions and Keywords — Input and Output Devices

Definitions to memorise and the exact keywords mark schemes credit for input and output devices answers — sharpened from recent examiner reports for the 2026 0478 sitting.

Input device
Examiner keyword
A peripheral that sends data INTO the computer for processing (keyboard, mouse, microphone, scanner, sensor, camera).
Output device
Examiner keyword
A peripheral that receives data FROM the computer and presents it to the user or environment (monitor, printer, speaker, actuator).
Sensor
Examiner keyword
An input device that captures real-world physical data (temperature, light, pressure, sound, motion, moisture, gas) and converts it into a digital signal the computer can process.
Actuator
Examiner keyword
An output component that converts an electrical signal into physical action (motor, valve, hydraulic ram, heater).
Barcode reader
Scans a 1D pattern of black-and-white bars and converts it into a numeric/alphanumeric code (commonly used in retail/inventory).
QR-code reader
Scans a 2D matrix of black-and-white squares to decode much more data than a barcode, including URLs and short text.
Resistive touch screen
Examiner keyword
Two conductive layers separated by a tiny gap. Pressure brings the layers into contact, generating a coordinate. Works with any object but less sensitive than capacitive.
Capacitive touch screen
Examiner keyword
A coated glass layer holds an electric charge; a fingertip changes the local charge to register a touch. Highly responsive, supports multi-touch, but only works with conductive objects (e.g. skin).
Infrared touch screen
Examiner keyword
A grid of infrared beams across the screen surface; an object breaking the beams registers a touch. Durable, works with any object, but expensive.
LCD (Liquid Crystal Display)
Display that uses liquid crystals between polarising filters; needs a separate backlight (originally CCFL, now usually LED).
LED display
An LCD that uses LEDs as the backlight (LED-backlit LCD), or a true OLED display where each pixel emits its own light.
Additive manufacturing (3D printing)
Examiner keyword
Building a 3D object by adding material layer-by-layer from a digital model.

Common Mistakes and Misconceptions — Input and Output Devices

The traps other students keep falling into on input and output devices questions — taken from recent Cambridge IGCSE 0478 examiner reports and mark schemes — and how to avoid them.

✕Confusing laser and inkjet printers
Why it happens
Both produce 2D prints; students lump them together.
How to avoid it
Laser: dry powder (toner) fused to paper using a heated drum; fast, sharp, high-volume. Inkjet: liquid ink sprayed through nozzles; cheaper hardware, better photo quality, slower, ink dries up.
✕Naming a 'sensor' as the input WITHOUT specifying which type
0478 Examiner Reports 2022-2024
Why it happens
Students write 'a sensor' as if it's specific.
How to avoid it
Always name the SPECIFIC type — temperature, light, moisture, pH, motion, infrared, pressure. Mark scheme rejects 'sensor' on its own when a specific role is required.
✕Calling a motor an 'output device' rather than an actuator
Why it happens
Both terms apply at GCSE level.
How to avoid it
Both are technically right but ACTUATOR is the precise term in control systems. Use it when a question specifies a process-control context (motor, pump, valve, heater).
✕Saying 3D printers print 'in 3D ink'
Why it happens
Treating 3D printing as a fancier inkjet.
How to avoid it
There is no 3D ink. The material is filament/plastic/resin/metal powder, deposited layer-by-layer. ADDITIVE manufacturing builds up; 2D printing only places material on the surface.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Input and Output Devices — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Input and Output Devices

Short Study Notes in the form of Slides

Detailed Study Notes

What you’ll learn

How it’s examined

1Compare touch-screen technologies (6 marks)

2How a 3D printer works (6 marks)

3Sensors in a smart glasshouse (6 marks)

Input device

Output device

Sensor

Actuator

Barcode reader

QR-code reader

Resistive touch screen

Capacitive touch screen

Infrared touch screen

LCD (Liquid Crystal Display)

LED display

Additive manufacturing (3D printing)

✕Confusing laser and inkjet printers

✕Naming a 'sensor' as the input WITHOUT specifying which type

✕Calling a motor an 'output device' rather than an actuator

✕Saying 3D printers print 'in 3D ink'

Practice questions

Past paper style quiz

Assess your understanding

Input and Output Devices — frequently asked questions