Implementing a Reverse Debugger for Logo

Programming is a creative activity that teaches precision. In Logo, novices write simple programs that draw geometric shapes onto a screen. Logical flaws, however, cause unintended results and pose a major challenge for young programmers who yet need to learn how to search for errors in their code. We discuss the problems novices face when learning to program in Logo. Furthermore, we present a reverse debugger for Logo that enables programmers to step through their code in either direction. Using a stack, previous program states can be retrieved on demand. Our solution balances performance and memory consumption and hence can be used to debug even long and complex programs.