One of the most important features of living beings that seems universal is perhaps their ability to be modified in a functional way. In order to modelize this characteristic, we designed automata with a finite number of instantaneous internal descriptions, with input(s) and output(s) and which are able to be functionally modified. The rules which govern the evolution of these automata (and the initial conditions) are randomly chosen at the beginning and once and for all. When such an automaton is linked by its input and output to a deterministic process, it always stabilizes and it then has the property to rebuild itself. Thus it made a function which is inverse of the external function. We demonstrate the prevalence of p = 1 length period and of tau = 0 transient length for automata with m instantaneous internal descriptions.