Abstract: For a general program P, multi-valued interpretations and models are defined, considering a set of truth logic values and an undefined value. The program P may contain constant propositions, which are defined for each truth logic value. Two orderings between the set of all multi-valued interpretations are considered: one is Fitting ordering and the other is standard ordering. The semantics of type well-founded and of type stable for a program P are introduced. This study showed that the well-founded model is the least stable model with respect to Fitting ordering.