Point noted DrJim - as well as the fact that most of the sources you quote are from Scratch.mit.edu., however you might have missed my intent in posting the previous message. I was not specifically talking about having an avatar compute Fibonacci numbers or even circular linkedlists. (I have an avatar that allows anyone to click on it and play the old game of Pong. Gabe's setting prevented me from using it when I joined ). I was simply making a statement about using Alice ,and hopefully this forum, to present a good understanding of programming techniques.

As to the use of recursion, it is a requirement of the AP that students have a good understanding of how to solve a problem using recursive calls and shows up more than once on both the A and AB Exams. I do concurr with you that it is incumbent upon the person presenting the data to make the student aware of stack overflows, out-of-memory errors, etc. which can occur if the programmer does not have a good understanding of when and how to use recursion in a program.

What makes it even more confusing is trying to explain to young "programmers" the difference between linear recursion and exponential recursion or infinite recursion and conditional recursion - knowing when to use each recursive method is important, but you already know that. Unfortunately for the students. the AP requires that we teach them recursion.

I use the Sierpinski gasket (C. Herbert), Towers Of Hanoi (Dann, et al) and exercises in Joel Adams book as introductory examples of how to use recursion. I have found that if students can visualize how recursion works they can understand it better once they move into a pure programming environment and prepare for the Advanced Placement Exams.

Keep up the good work in responding to all of the questions appearing in this forum.

lanceA