>I gonna picking up some old c++ book and study delphi to
>make the concept of oop more clearly .
Why not try for the VFP version? One old book that may be useful still for concepts (though the code is a little out of date) is:
"The Revolutionary Guide to Visual FoxPro OOP"
Phelps et al
Wrox Press, May 1996
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Regards
Andy Kramek