Gradebook1.cpp (Your first simplest OOP program)
Gradebook1b.cpp (Same as above, but with :: implementation)
Gradebook2.cpp (private and public)
Gradebook3.cpp (constructor and destructor)

GradeBook4.h (implementation)
Gradebook4.cpp (driver)

GradeBook6.h (header)
GradeBook6.cpp (implementation file with validity check)
driver6.cpp (driver)