Very often, living beings seem able to change their functioning when external conditions vary. In order to study this property, we have devised abstract machines whose internal organisation changes whenever the external conditions vary. The internal organisations of these machines, are as simple as possible, functions of discrete variables. We call such machines self-modifying automata.These machines stabilise after any transient steps when they go indefinitely through a loop called p-cycle or limit cycle of length p. More often than not, the (...) p in the cycle is equal to one and the cycle reduces to a fixed point. (shrink)