Visuelle Programmierumgebungen wie Scratch führen dazu, dass bottom-up und sehr feingranular programmiert wird. Dies widerspricht den Grundsätzen der Informatik für gute Programmentwicklung, die eher top-down und klare Strukturen empfehlen. Sind somit visuelle Programmiersprachen gut für den Einstieg, aber schlecht für die spätere Vertiefung?

Visual programming environments are widely used to introduce young people to computer science and programming; in particular, they encourage learning by exploration. During our research on teaching and learning computer science concepts with Scratch, we discovered that Scratch engenders certain habits of programming: (a) a totally bottom-up development process that starts with the individual Scratch blocks, and (b) a tendency to extremely fine-grained programming. Both these behaviors are at odds with accepted practice in computer science that encourages one: (a) to start by designing an algorithm to solve a problem, and (b) to use programming constructs to cleanly structure programs. Our results raise the question of whether exploratory learning with a visual programming environment might actually be detrimental to more advanced study.

Probably the paper that most influenced my thinking was Orni Meerbaum-Salant’s paper on Habits of Programming in Scratch (same session). They studied a bunch of students’ work in Scratch, and identified a number of common misconceptions and errors. What was fascinating was that the bugs looked (to me) a lot like the ones that Elliot Soloway found with the Rainfall Problem, and the issues with concurrency were like the ones that Mitchel Resnick found with Multilogo and that John Pane found with HANDS. That suggests that changing the environment doesn’t change the kinds of errors students are making. And since all student programming misconceptions come from our instruction (i.e., students don’t know much about programming before we teach them programming), it means that we’ve been teaching programming in basically (from a cognitive perspective) the same way since Pascal.