1 Getting the best from interaction devices

Once we have chosen an interaction device for a user interface, we need to consider how to use it effectively. We have relatively little control over the appearance or use of input devices, so we concentrate on the design of the feedback provided by output devices. In particular, we concentrate on the following software components that form this feedback.

• Text. How can we ensure that the text is legible? Which font should we use? How long should the lines be?
• Colour. Which colours go well together? How should colour be used in order to communicate information more effectively? How can we ensure that the colours we use have the correct connotations?
• Images. What are the different types of image? How do you choose the right one?
• Moving images. When is it useful to animate images? When can video clips be used to good effect?
• Sound. When can sound be useful? What are the different categories of sound and when should each be used?

Many of these issues are also relevant to input devices, such as the choice of colour for the panic button in a train or the font chosen for entering text into a form-fill application.

These software components are usually relatively easy and cheap to change, but applying them in a consistent and thoughtful manner can make a big difference to the usability of the User Interface (UI).

It is important to be clear what you are trying to achieve when you use these components. We are assuming that you want to communicate information and functionality in a simple but effective manner. This is different to a graphic designer, whose priority may be to create a design that is fresh and innovative. These differences have practical implications. For example, an advertising website designed by a graphic designer may have shorter line lengths, and employ more colours and images than we would recommend.