You can create functions with the same name and return type but with different parameters, this is called overloaded functions.
A function can have ‘default parameters’ however they must be specified at the end of the parameter list unless all parameters have a default expression
double Area(double Pi = 3.14, double radius);
This will result in a compiler error as the default parameter ‘Pi’ is not at the end of the parameter list for this to compile it would need to look like
double Area(double radius, double Pi = 3.14);
OR
double Area(double Pi = 3.14, double radius = 0.0);