Parameter of the parameter interface of a procedure. Formal parameters have names and are either generic or completely typed. Either pass by reference or pass by value is determined for each formal parameter. Depending on their type assignment, they can be used in the same way as data objects in the procedure. The formal parameters make up a substantial part of the signature of a procedure. Formal parameters are either positional parameters (for subroutines) or keyword parameters (for methods and function modules). When a procedure is called, formal parameters are bound to actual parameters.