The various devices used in programed instruction range from the simple linear programed book to branching and skip branching programs, adaptive teaching machines, and even complex computer based systems. In order to provide a background for the would-be programer, the essential principles of each of these devices is outlined. Different ideas of programing as advanced by Pressey, Skinner, Crowder, Gilbert, and Mager are discussed. Before dealing with the actual process of programing, the principles, objectives and criteria necessary to provide a framework are presented. This work also discusses techniques for evaluating the effectiveness and efficiency of programed instruction, and presents some of its possible uses in the total educational process, particularly in industrial training and university teaching. Looking ahead, the text points out areas for research, examines team teaching and clock paced systems for their possible contributions, and deals in depth with the most advanced of teaching machines--the computer. Some speculations are offered about the social implications of the developing instructional technology. A selected bibliography is included. (JY)