people（人员）类派生出student（学生）类，添加属性：班号char classNo[7]；从people类派生出teacher（教师）类，添加属性：职务char principalship[11]、部门char department[21]。从student类中派生出graduate（研究生）类，添加属性：专业char subject[21]、导师teacher adviser；从graduate类和teacher类派生出　　TA（助教生）类，注意虚基类的使用-people (staff) derived class student (student) category, add the attribute: Class No. char classNo [7]　people class derived from the teacher (teacher) class, add the attribute: Title char principalship [11], department char department [21 ]. Derived from the student class graduate (graduate) class, add the attribute: Professional char subject [21], mentor teacher adviser　graduate class and the teacher from the derived class TA (teaching assistant students) class, pay attention to the use of virtual base class