Introduction to OOP Chapter 15: Overloading : next previous audio real text

Optional Parameters

Some languages allow the programmer to create optional parameters, usually only at the end of the parameter list: 
function Count (A, B : Integer; C : Integer = 0; D : Integer = 0);
begin
		(* Result is a pseudo-variable used *)
		(* to represent result of any function *)
	Result := A + B + C + D;
end

begin
	Writeln (Count(2, 3, 4, 5)); // can use four arguments
	Writeln (Count(2, 3, 4)); // or three
	Writeln (Count(2, 3)); // or two
end
Such a program will have more than one type signature.
Intro OOP, Chapter 15, Slide 13