Use an array to store test grades.
<UL>
<LI> <A HREF='GradeBook.h'>GradeBook.h</A> - definition of class
GradeBook.  Note that the public data member "students" can be
initialized in this way, because it is "static const".
Otherwise, data members are generally initialized in constructors.
    <UL>
    <LI> Initialize a non-static data member is a warning.
    <LI> Initialize a non-const data member is an error.
    </UL>
<LI> <A HREF='GradeBook.cpp'>GradeBook.cpp</A> - member function
implementation
<LI> The <A HREF='fig07_17.cpp'>main program</A> accesses the 
<em>class variable</em> "GradeBook::students".
</UL>