A formal model of the state of a dynamic system with updateable locations as values is presented. A mechanism of dynamic function declaration resembling that of variable declaration in programming languages is suggested.With each of these functions a dynamic access function is associated. An access function can be used either explicitly or implicitly like in programming languages (explicit or implicit dereferencing). An update of an access function causes the update of the corresponding location. A procedure parameter declared as a reference parameter accepts locations as arguments so that a value associated with the location can be updated by the procedure.