This book defines and describes communication media; discusses the difference between information and instruction, instructional media and instructional aids; and proposes a set of criteria by means of which communication media may be distinguished from nonmedia, one medium distinguished from another, and a single medium distinguished from multimedia applications. A two-dimensional classification system for communication media is proposed: in one dimension, seven classes are defined, based on ways of representing information; in the other, communication media are divided into two groups, telemedia and recording media. Twenty-eight specific communication media are defined and described. This list includes the major available and soon-to-be-available media.

Bretz presents a review of the new communication systems which allow people to respond and interact with each other, or the machine, as if in face-to-face conversation. Video conferencing, video telephones, and teletext -- a range of such communication media are already in use or on the drawing boards. The author describes a number of such systems and their uses. He also discusses quasi-interactive systems, which seek responses from an audience before they can proceed. He considers the problems involved in designing such systems and suggests future possibilities.