Touch screen interfaces

A touch screen works as both an input and an output device. You view the options available to you on the screen (output) and use your finger to touch the option you want (input).

A touch-sensitive screen uses resistive or capacitive technology to detect touch. Many mobile phones use touch screens and do away with a keypad entirely. They are often used on cash machines and in shopping centres too. Touch screens are robust, easy to operate and easy to reprogram.

Resistive

When considering smartphone touch screens, resistive touch screen is the older of the two technologies.

The surface is made of flexible plastic with a thin film of conductive material printed onto its underside. Beneath it is a second layer – usually made of glass, but sometimes of hard plastic – also with a coating of conductive material.

The two layers are kept apart by tiny bumps (or spacers) placed at regular intervals. When the screen is touched, the plastic deforms so the two conductive films meet and, by measuring the resistance of both layers at their point of contact, it's possible to get an accurate measurement of the touch position.

Capacitive

A consists of two plates separated by an insulating material, which may of course be air. A capacitive touch screen consists of two spaced layers of glass, coated with a conductive material. As your finger comes close to a capacitor it changes the local field, and the system constantly monitors each tiny capacitor to discover exactly where the finger touched the screen.

Because the measurement points are discrete, it is possible to tell whether several fingers are touching the screen at once, unlike with a resistive unit.

Advantages	Disadvantages
Ease of use – they are intuitive so they require limited training.	Not suitable for inputting large amounts of data.
Can be used without additional peripherals such as keyboard or mouse.	Loss of accuracy due to selecting options/items with fingers.
Switches and buttons are not physically required. Software designers can make and modify various input interfaces for different situations.	Easily damaged – touch screens, partly due to their portability, can be fragile.
With capacitive multi-touch function, various operations/inputs (eg: zoom-in/zoom-out, rotation) are possible.	Expense – Large touch screens can be a lot more expensive than using traditional keyboard and mouse solutions.
Hygiene – Easy to wipe clean, unlike traditional keyboard.

Advantages	Ease of use – they are intuitive so they require limited training.
Disadvantages	Not suitable for inputting large amounts of data.

Advantages	Can be used without additional peripherals such as keyboard or mouse.
Disadvantages	Loss of accuracy due to selecting options/items with fingers.

Advantages	Switches and buttons are not physically required. Software designers can make and modify various input interfaces for different situations.
Disadvantages	Easily damaged – touch screens, partly due to their portability, can be fragile.

Advantages	With capacitive multi-touch function, various operations/inputs (eg: zoom-in/zoom-out, rotation) are possible.
Disadvantages	Expense – Large touch screens can be a lot more expensive than using traditional keyboard and mouse solutions.

Advantages	Hygiene – Easy to wipe clean, unlike traditional keyboard.
Disadvantages

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Digital development considerations - CCEATouch screen interfaces