As in other fields, progress is based on a certain number of intelligent and innovative ideas, abstraction of a mathematical nature and a relative distance from the technology of the moment. It's the kind that could give rise to many of the major innovations that have shaped the computing landscape. It should be noted that the fact that several “useless” branches long considered pure mathematics but at least recognized as having a certain “depth”, have found unexpected applications in computer science. One historical source consists of very theoretical needs for understanding the formal calculations that underlie mathematical analysis. It is thanks to these achievements that the public can now have access to the Internet, the Web, DVDs and mobile phones.,