Resumen
The computational capabilities of computer tools expand the student?s search capabilities. Conducting computational experiments in the classroom is no longer an organizational problem. This raises the ?black box? problem, when the student perceives the computational module as a magician?s box and loses conceptual control over the computational process. This article analyses the use of various computer tools, both existing and specially created for ?key? computational experiments, that aim at revealing the essential aspects of the introduced concepts using specific examples. This article deals with a number of topics of algebra and calculus that are transitional from school to university, and it shows how computational experiments in the form of a ?transparent? box can be used.