For more than fifty years people have been exploring how computers might enhance learning and teaching. The malleable nature of computers has enabled suggestions that a computer can act like flash cards, personal tutors, textbooks, reference books, virtual laboratories, quizzes, virtual spaces, lecture halls, and study groups. Perhaps the most radical suggestion has been to see the computer as something learners can creatively mold into something personally meaningful that is dynamic, interactive, and shared. And that the process of constructing such computational artefacts is rich in learning opportunities. These range from a deeper understanding of the subject matter of the constructions to high-level skills in thinking and problem solving.