This innovative book develops a formal computational theory of writing systems and relates it to psycholinguistic results. Drawing on case studies of writing systems around the world, it offers specific proposals about the linguistic objects that are represented by orthographic elements and the formal constraints that hold of the mapping relation between them. Based on the insights gained, it posits a new taxonomy of writing systems. The book will be of interest to students and researchers in theoretical and computational linguistics, the psycholinguistics of reading and writing, and speech technology.