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Detailed notes on Hardware for Cambridge IGCSE Computer Science, covering key concepts, explanations, examples, and exam-focused revision points.
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.
Mapped to the Cambridge IGCSE 0478 syllabus (2026-2028).
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:
Cambridge tip. When a question asks for 'an input device', name a SPECIFIC device with a CLEAR PURPOSE — not 'a sensor' or 'a button'.
Monitors, printers, speakers, actuators.
An output device receives data from the computer and presents it to the user or environment.
Visual outputs.
Print outputs.
Audio outputs.
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.
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.
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.
Infrared. A grid of infrared LEDs projects beams across the screen surface; receivers detect when an object (any object) breaks the beams.
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.
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:
Real-world uses.
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.
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.
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).
Verbatim phrases and definitions Cambridge mark schemes credit.
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.
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.
Question
State whether each device is an INPUT device or an OUTPUT device: (a) microphone, (b) actuator. (2 marks)
Step-by-step solution
Step 1
(a) Microphone (1 mark). A microphone captures sound and sends it INTO the computer to be processed/stored — so it is an INPUT device.
Step 2
(b) Actuator (1 mark). An actuator receives a signal FROM the computer and turns it into physical movement (e.g. opening a valve) — so it is an OUTPUT device.
Answer
(a) Input. (b) Output.
Examiner tip
Ask 'which way does the data flow?' Data IN = input; data OUT to the user/environment = output. A sensor is always input; an actuator is always output.
Question
A poster links visitors to a website. State whether a barcode or a QR code is more suitable and give one reason. (2 marks)
Step-by-step solution
Step 1
Choice (1 mark). A QR code is more suitable.
Step 2
Reason (1 mark). A QR code is a 2D code that can store far more data than a 1D barcode — enough to hold a full URL — and can be read by a smartphone camera/app.
Answer
QR code, because it stores much more data (a full web address) than a 1D barcode and can be read by a phone camera.
Examiner tip
Don't just name the device — the second mark is the JUSTIFICATION. 'More data / can hold a URL / 2D matrix' all score.
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
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.
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.
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.
Examiner tip
Always name the SPECIFIC sensor type — 'a sensor' on its own scores nothing. Each device earns 1 mark for the sensor and 1 mark for how the system reacts to its reading.
Question
An office prints thousands of black-and-white documents every day. Recommend a suitable printer and justify your choice by comparing it with the alternative. (4 marks)
Step-by-step solution
Step 1
Recommendation (1 mark). A laser printer is the most suitable choice.
Step 2
Speed / volume (1 mark). Laser printers print a full page at once using a drum, so they are very fast and handle high print volumes far better than an inkjet, which prints line-by-line.
Step 3
Running cost (1 mark). Toner cartridges last for many thousands of pages, giving a low cost-per-page — cheaper over time than inkjet ink for high volumes.
Step 4
Reliability (1 mark). Toner is a dry powder, so there is no risk of nozzles clogging or ink drying up if the printer is idle (a common inkjet problem).
Answer
Laser printer: faster, lower cost-per-page (toner lasts thousands of pages) and more reliable for high-volume work than an inkjet, which is slower and whose ink can clog/dry up.
Examiner tip
A 'recommend and justify' question needs a clear choice PLUS reasons tied to the SCENARIO (high volume, black-and-white). Comparing against the rejected option strengthens the answer.
Question
Describe how a 3D printer creates a physical object from a digital design. (6 marks)
Step-by-step solution
Step 1
Design (1 mark). A 3D model is created using CAD (computer-aided design) software, then exported (typically as an .stl file).
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.
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.
Step 4
Bonding and cooling (1 mark). Each new layer fuses to the previous one as the material cools, building the solid 3D shape.
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'.
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
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).
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.
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.
Examiner tip
Each touch-screen type earns 1 mark for an advantage and 1 for a disadvantage. Capacitive's defining limit (needs a conductive object) and infrared's durability are the highest-value points.
High-scoring sample answers for input and output devices on the Cambridge IGCSE 0478 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.
Name one input device used to enter text into a computer. [1]
Model answer
A keyboard.
(A virtual/on-screen keyboard is also acceptable.)
Why this scores
1 mark (AO1, recall). Any valid text-entry input device scores. A mouse or scanner would NOT — they don't enter text directly.
A user wants a temporary on-screen copy of a document and, separately, a permanent paper copy. Name the output device for each. [2]
Model answer
Why this scores
2 marks (AO1/AO2). Watch the keywords: 'temporary/on-screen' = soft copy (monitor); 'permanent/paper' = hard copy (printer).
Describe how a light sensor is used in an automatic street-lighting system. [3]
Model answer
Why this scores
3 marks (AO2). Award marks for: reads light level → compared to a preset value → output action triggered by the comparison. The sensor only inputs data; it does NOT make the decision.
Explain two differences between an LCD monitor and an LED (LED-backlit) monitor. [4]
Model answer
Why this scores
4 marks (AO1/AO2): 2 marks per difference (the LCD side and the LED side). The core distinction is the backlight — an LED monitor IS an LCD, just lit by LEDs rather than fluorescent lamps.
Describe how a barcode reader reads a barcode at a supermarket checkout. [5]
Model answer
Why this scores
5 marks (AO1/AO2). Key sequence: light shone → reflected/absorbed by bars → sensor detects → converted to digital → decoded to a number → looked up in the database. Don't say the reader 'reads the price' — it reads a code; the DATABASE holds the price.
A self-service museum kiosk lets visitors browse exhibits and listen to audio guides. Recommend a suitable input device and a suitable output device for the kiosk, justifying each choice. [6]
Model answer
Input device — touch screen:
Output device — speakers / headphones:
Why this scores
6 marks (AO2/AO3): 3 marks per device = (named device) + (justified against the scenario) + (an extra scenario-relevant point). Marks come from the JUSTIFICATION tied to a public, browse-and-listen kiosk — not just naming 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.
A peripheral that sends data INTO the computer for processing (keyboard, mouse, microphone, scanner, sensor, camera).
A peripheral that receives data FROM the computer and presents it to the user or environment (monitor, printer, speaker, actuator).
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.
An output component that converts an electrical signal into physical action (motor, valve, hydraulic ram, heater).
Scans a 1D pattern of black-and-white bars and converts it into a numeric/alphanumeric code (commonly used in retail/inventory).
Scans a 2D matrix of black-and-white squares to decode much more data than a barcode, including URLs and short text.
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.
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).
A grid of infrared beams across the screen surface; an object breaking the beams registers a touch. Durable, works with any object, but expensive.
Display that uses liquid crystals between polarising filters; needs a separate backlight (originally CCFL, now usually LED).
An LCD that uses LEDs as the backlight (LED-backlit LCD), or a true OLED display where each pixel emits its own light.
Building a 3D object by adding material layer-by-layer from a digital model.
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.
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.
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.
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 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.
The things students keep getting wrong in this sub-topic, answered.