Virtual Functions question

Hi, This is my class structure: Base interpolation class linear interpolation class (derived from base interpolation class) hermite spline interpolation class (derived from base interpolation class) Anyway, in my program, you can read a textfile and call a load function. linear.load() takes 2 parameters hermite.load()takes 3 parameters I tried simply overloading my virtual function in the base interpolation class, but I get a few errors: Hermite: cannot instantiate abstract class due to following members: See declaration of "hermite" see declaration of "Load" warning C4259: 'void __thiscall Interp::Load(class ifstream &,int,class point *)' : pure virtual function was not defined Linear: Cannot instantiate abstract class due to following members: See declaration of "linear" See declaration of "load" warning C4259: 'void __thiscall Interp::Load(class ifstream &,int,class point *,class vector *)' : pure virtual function was not defined how do I declare my overloaded virtual functions inside of the base interpolation class? Thanks, -pete [edited by - pschmitt on April 24, 2003 7:51:46 PM] [edited by - pschmitt on April 24, 2003 7:52:28 PM]