The notion of affective computing refers to systems that can recognize, express and in some sense be said to have emotions. The book consists of two parts, where the first gives an overview of research into the nature of emotion from different academic fields, how emotions can be represented and what it would mean to have emotional computers. The second part is concerned with implementation techniques. Although it may seem odd to talk about emotions in relations to computers, there are potentially interesting application domains such as mediated communication, learning and adaptive systems.