Abstract *A11 teaching processes can be precisely specified by means of Helmar Frank's six didactic variables (each of which can in turn be interpreted as a vector of vectors). These are: learning system, teaching system, subject matter, target standard, environment and teaching algorithm. In order to improve understanding and retention of the subject matter, teaching programmes use longer and more complex teaching algorithms than do conventional instruction and lectures. Retention requires a certain amount of well‐spaced repetition. The control of the repetition function can be exercized by the teaching system or by the learning system, provided the latter is willing and able to do so. Conventional instruction leaves the control of the repetition function (and other learning functions) to the learning system and often fails to reach the target standard because it has overestimated the ability or willingness of the learning system to control its own learning activities. Programmed instruction makes a cons...