Compiler problem Calculator program in C++Builder Starter

In the introductery program Calculator in C++Builder Starter there is a change of classname that looks like poison to the compiler. I am not able to continue programming from this  point on.   It is in the form header file that I am told to change the classname to     class TForm1 : public TForm, ICalculatorDisplay   from class TrForm1 : public TForm   Is this a compiler-related problem? I have turned off the Borland-compiler.   Anyone who have had the same problem? This is a pity, because this introductery lessons from David Millington is very much a sucsess story.   Leiv Amund Haaland