The aim of this book is to both outline the nature and design of interfaces based around the available computing technologies, and also to discuss the extent to which designers can develop interfaces that "understand" their potential users. It also examines the concept of usability. "Understanding Interfaces" is divided into four parts. The first introduces the issues of interface use and design; the second discusses understanding uiterfaces in terms of human communication; the third covers the skills necessary for interface use; and the final part examines the design and evaluation of interfaces. The title "Understanding Interfaces" has a dual interpretation. Firstly, there is wealth of research and development work associated with the design and use of machine interfaces, which requires a detailed explanation. Secondly, there is also great interest in the design of interfaces which are constructed in a way which is sympathetic to, or "understands", the potential user. In order to capture and integrate the number of different ways of looking at interface use, the book has been divided into four parts. The first part introduces the issues of interface use and design; the second discusses understanding interfaces in terms of human communication; the third covers the skills necessary for interface use; and the final part examines the design and evaluation of interfaces. "Understanding Interfaces" aims to be an essential text for students of interface design, software design, ergonomics, cognitive psychology, and human-computer interaction. It should also be useful for practitioners in the area.