💻 Paper 1 · Topic 3: Hardware
3.2 Input & Output Devices
Cambridge IGCSE Computer Science 0478 · ~13 min read · ⭐ Pro

Input Devices

An input device allows data to be entered into a computer system. Different input devices are suited to different types of data and applications.

Keyboard

Used to enter text, numbers and commands. Most common input device for general-purpose computing. A keyboard is a good choice when accuracy and speed of text entry are needed.

Mouse / Trackpad / Trackball

Pointing devices used to control an on-screen cursor. The mouse is the most common; a trackball is better in confined spaces; a trackpad is used on laptops.

Microphone

Converts sound (analogue) to digital data. Used for voice input, voice recognition software, video calling, and recording audio.

Touchscreen

Detects the position of a touch on the screen. Acts as both an input AND output device. Used in smartphones, ATMs, kiosks, and medical equipment. Types: resistive (pressure-based) and capacitive (electrical charge, used in smartphones).

Scanner / Barcode Reader

A scanner converts physical documents/images to digital form. A barcode reader reads barcodes (used in retail, stock control, libraries). A QR code reader reads 2D codes with much more data capacity.

Digital Camera

Captures images and video as digital data. Used in surveillance, medical imaging, and photography.

Sensors

Sensors detect real-world physical values and convert them to digital data. Used in embedded systems and IoT devices.

Sensor TypeWhat it detectsExample use
TemperatureHeat levelThermostat, greenhouse control
LightLight intensityAutomatic street lighting
SoundSound level/volumeSecurity alarms
PressureForce/weightTraffic monitoring, robotics
HumidityMoisture levelGreenhouse, HVAC systems
InfraredMotion/heatBurglar alarms, automatic doors
pHAcidityWater quality monitoring

Output Devices

An output device allows data to be sent out of a computer system in a usable form.

Monitor / Screen

Displays visual information. Key characteristics: resolution (pixels), refresh rate (Hz), size. Types: LCD, LED, OLED. Touchscreens are both input and output.

Printer

  • Inkjet: sprays droplets of ink; good for photos and colour; slow; cheap to buy
  • Laser: uses toner and heat; fast; good for high-volume black-and-white printing; expensive to buy
  • 3D printer: builds 3D objects layer by layer; used in manufacturing, medicine, prototyping

Speaker / Headphones

Converts digital audio data to sound (analogue). Used for music, voice output, system sounds.

Actuators

An actuator is an output device in a control system — it converts a digital signal into a physical action. Examples: motors, fans, pumps, heaters, solenoids.

Embedded Systems

An embedded system is a dedicated computer system built into a device to perform a specific task. It uses sensors (input) and actuators (output) with a microcontroller at its core.

Examples: washing machine controller, microwave oven, digital camera, antilock braking system (ABS), pacemaker.

Key characteristics: dedicated to one task, often real-time, low power consumption, small and cheap.

Exam tip: For "suggest a suitable input/output device for [situation]", always justify your choice — don't just name the device. E.g. "A barcode reader because it quickly and accurately reads product codes at a checkout." Questions often ask for input AND output in the same scenario — name both and justify both.
⚠️ Common Mistakes
  • Forgetting to say a touchscreen is BOTH input AND output
  • Confusing a sensor (input) with an actuator (output) in a control system
  • Just naming a device without explaining WHY it is suitable for the given scenario
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Worksheet — Input & Output Devices

5 questions · 16 marks

Q1A self-service checkout system at a supermarket uses a touchscreen, barcode reader, and speaker. For each, state whether it is an input or output device and give one reason. [6]
✅ Mark scheme
Touchscreen: input AND output [1] — it both displays information and detects customer touches [1]; Barcode reader: input [1] — it reads product barcodes and sends data to the system [1]; Speaker: output [1] — it plays audio messages/beeps to the customer [1]
Q2State two differences between an inkjet printer and a laser printer. [2]
✅ Mark scheme
Any two: Inkjet uses liquid ink / Laser uses toner [1]; Laser is faster / inkjet is slower [1]; Laser is better for high-volume printing [1]; Inkjet is cheaper to buy / laser is more expensive [1]
Q3A greenhouse uses sensors and actuators. Name one suitable sensor and one actuator that could be used, and explain the purpose of each. [4]
✅ Mark scheme
Sensor: temperature sensor [1] — measures the temperature inside the greenhouse [1]; Actuator: heater/motor/fan [1] — turns on to warm the greenhouse or open a vent when temperature is too low/high [1]
Q4State what is meant by an embedded system and give two examples. [3]
✅ Mark scheme
An embedded system is a computer system built into a device to perform a dedicated/specific task [1]; Examples (any two): washing machine, microwave, digital camera, ABS braking system, pacemaker [2]
Q5Suggest a suitable input device for a visually impaired user who wants to enter text by speaking. Give a reason. [1]
✅ Mark scheme
Microphone [1] (with voice recognition software) — allows text to be entered without needing to see a screen or keyboard
Quiz — Input & Output Devices
Q 1 of 8
Score
/ 8
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TermDefinition
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Mini Test — Input & Output Devices

10 minutes · mixed marks

← 3.1b FDE Cycle Topic 3: Hardware Next: 3.3 Data Storage →
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