Human-computer interaction (HCI) refers to the usage and designing of computer technology for communication between the computer and the user. As a field of research, HCI studies the way humans interact with computers and design technologies that facilitate this interaction. An interface between humans and computers is essential to this interaction. Internet browsers, desktop applications, computer kiosks and handheld computers use graphical user interfaces. Voice user interfaces are required for speech synthesizing and speech recognition systems. Research in this domain is focused on designing new computer interfaces, implementing interfaces, studying human computer use and sociocultural implications, etc. The ever-growing need of advanced technology is the reason that has fueled the research in the field of human-computer interaction in recent times. The aim of this book is to present researches that have transformed this discipline and aided its advancement. As this field is emerging at a rapid pace, the contents of this book will help the readers understand the modern concepts and applications of the subject.