Form over function: teaching beginners how to construct programs

Teaching beginners how to program is hard: As knowledge about systematic construction of programs is quite young, knowledge about the didactics of the discipline is even younger and correspondingly incomplete. Developing and refining an introductory-programming course for more than a decade, we have learned that designing a successful course is a comprehensive activity and teachers should consider and question all aspects of a course. We doubt reports of sweeping successes in introductory-programming classes by the use of just one single didactic device---including claims that "switching to Scheme" magically turns a bad course into a good one. Of course, the choice of individual devices (including the use of Scheme) does matter, but for teaching an effective course the whole package counts. This paper describes the basic ideas and insights that have driven the development of our introductory course. In particular, a number of conclusions about effective teaching were not as we had originally expected.