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Chapter Introduction


The main goals of the chapter are to accomplish the following:

  • Provide an overview of the diversity of interfaces.

  • Highlight the main design and research considerations for each of the interfaces.

  • Discuss what is meant by a natural user interface.

  • Consider which interface is best for a given application or activity.


When considering how to solve a user problem, the default solution that many developers choose to design is an app that can run on a smartphone. Making this easier still are many easy-to-use app developer tools that can be freely downloaded. It is hardly surprising, therefore, to see just how many apps there are in the world. In 2022, Apple had over 2 million apps in its store while Google had over 3 million!

Despite the immensity of the smartphone app industry, the web continues to proliferate in offering services, content, resources, and information. A central concern is how to design websites that deliver services, content, resources and information across different devices and browsers, which takes into account the varying form factors of smart watches, smartphones, laptops, smart TVs, and computer screens. Besides the app and the web, many other kinds of interfaces have been developed and researched, including voice interfaces, touch interfaces, gesture interfaces, and multimodal interfaces.

The proliferation of technological developments has encouraged different ways of thinking about interaction design and UX. For example, input can be via mice, touchpads, pens, remote controllers, joysticks, RFID readers, gestures, and even brain-computer interaction. Output is equally diverse, appearing in the form of graphical interfaces, speech, mixed realities, augmented realities, tangible interfaces, wearable computing, and more.

The goal of this chapter is to give you an overview of the diversity of interfaces that can be developed for different environments, people, places, and activities. We present a catalog of 22 interface types, starting with command-based and ending with holographic ones. For each interface, we present an overview and outline the key research and design considerations. Some are only briefly touched upon, while others, which are more established in interaction design, are described in greater depth.

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