Input and Output Devices

Hardware · 4 question types

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 3% of your exam marks.

stable

Rare

Stable3%

Typically tested as 'give one use of…' or 'describe how this sensor works' questions.

There are three main touch-screen technologies. The key differences are how each one detects a touch.

Feature	Resistive	Capacitive	Infrared
How it detects touch	Two flexible conductive layers that press together when touched, completing a circuit at the touch point	A grid of conductors holds a tiny electrical charge; the human body changes the charge when a finger gets close, and the screen detects the change	A grid of infrared light beams crosses the screen surface; a finger or stylus breaks the beams and the screen detects where
Works with...	Almost anything: fingers, gloves, plastic stylus, fingernails	Bare skin only (or specially-conductive styluses); standard gloves and non-conductive objects will not register	Almost anything that can block the light beam (finger, gloved hand, stylus)
Multi-touch?	No (or only basic)	Yes	Yes
Sensitivity / accuracy	Slow, less responsive	Fast, smooth, very responsive	Fast and very accurate
Screen quality	Image looks slightly dimmer (the touch layers reduce light through)	Sharp and bright	Sharp and bright
Wear / durability	Soft layer can be scratched or wear out	Glass surface; very durable	Frame can collect dust and dirt
Cost	Cheap	More expensive	Most expensive
Where you see it	Older smartphones, ATMs, point-of-sale terminals, industrial control panels where gloves are worn	Modern smartphones, tablets, touch monitors	Large interactive displays, kiosks, electronic whiteboards

For a modern smartphone, capacitive is the obvious choice: fast, accurate, supports pinch-to-zoom.
For an ATM outside in winter, resistive is better: it works with gloved hands.
For a large interactive whiteboard that needs to work with finger, pen, or hand, infrared is well suited.