What should we teach in an introductory programming course?

Abstract

An introductory course (and its successor) in programming should be concerned with three aspects of programming: I. How to solve problems, 2. How to describe an algorithmic solution to a problem, 3. How to verify that an algorithm is correct. i should like to discuss mainly the first two aspects. The third is just as important, but if the first two are carried out in a systematic fashion, the third is much easier than commonly supposed. (Note that the third step is not "debugging," because the word "debugging" conveys the impression that errors are alright-that they are a natural phenomenon which, like flies in a house, must be found and swatted. If "debugging" was called "getting rid of one's mistakes," I'm sure most programmers would change their attitude and work harder at producing a correct program initially.) I want to indicate what I feel is being taught as opposed to what should be taught. My main theme is, of course, structured programming, but I will discuss some other points. For example, I will outline a replacement for that crutch the computer industry has been using for so long, the flow chart. While my remarks are aimed at the instructors of introductory programming courses, I feel they are important to the whole programming profession. Let us begin with the first aspect of programming, problem solving.