We introduce an infinite proper subset of regular languages (RL), so called the state change couple of finite automata (FA). The execution time state change behavior of FA is shown to be modelled as state automata (SA). For our purpose, we define a unary operator whose domain is FA and range is SA. The new language class obtained by applying the operator on FA is called state change languages (SCL). We show that SCL is closed under union, but not under complementation, homomorphism and inverse homomorphism. We also investigate the properties of SA with empty string transitions. The work given here can be considered as a basis for analyzing the language class properties of the runtime attributes of basic computational models.