ABSTRACT
Instructional text is one of the most venerable of educational technologies, and is still among the most widely used, probably exceeded only by the blackboard. Teachers rely on the textbook to provide accurate, up-to-date information and clear explanations aided by appropriate examples, illustrations, and analogies (chap. 9, this volume) for themselves and their students. Students view the text as the voice of authority (chap. 7, this volume), and it is continuously available to them, so they can return to it again and again when the teacher and other learning resources are unavailable.
