Parameter of the parameter interface of a procedure or event. Formal parameters have names and are either generic or completely typed. Either pass by reference or pass by value is defined for each formal parameter. Depending on their typing, they can be used in the same way as data objects in a 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.