Making a new operating system drive us to conceive a new programmation language Lisaac.This language based on prototype object is strongly inspired from self language.More than the advantages of self, Lisaac give protection of comunication mecanism and operating system tools. Using prototype and dynamic inheritance is fully adapted to the conception of operating system. First tests learn us, that Lisaac compiler is able to give the same performance than C compiler. Lisaac inherit of Self's semantic and of the Eiffel's static typing.