Need some help with one function

Original - code Code ifndef _STUDENTREC_H #define _STUDENTREC_H #define NUM_OF_MARKS 5 // indexed 0-4 class studentRecord { private: unsigned int studentNumber; char* _firstName; char* _lastName; unsigned int marks[NUM_OF_MARKS]; public: // the default constructor studentRecord(); // the destructor ~studentRecord(); // sets the student number of the record to studentNum. void setStudentNumber(unsigned int studentNum); // sets the student first name to firstName. void setFirstName(char* firstName); // sets the student last name to lastName. void setLastName(char* lastName); // sets the mark at index "index" of the student record to mark. // the method assumes the index is in 0-4 range, and // the mark is in 0-100 range. void setMark(int index, unsigned int mark); // returns the student number. unsigned int getStudentNumber(); // returns a pointer to the first name of the student record. char * getFirstName(); // returns a pointer to the last name of the student record. char * getLastName(); // returns the mark at index "index" of the student record. // it assumes the index is in 0-4 range. unsigned int getMark(int index); // prints the student record to the standard output in the format // specified in the assignment specifications. void print(); }; //studentRecord #endif

ifndef _STUDENTREC_H
#define _STUDENTREC_H

#define NUM_OF_MARKS 5   // indexed 0-4

class studentRecord {
private:
    unsigned int studentNumber;
    char* _firstName;
        char* _lastName;
    unsigned int marks[NUM_OF_MARKS];

public:
    // the default constructor
    studentRecord();

    // the destructor
    ~studentRecord();  

    // sets the student number of the record to studentNum.
    void setStudentNumber(unsigned int studentNum);

    // sets the student first name to firstName.
    void setFirstName(char* firstName);

    // sets the student last name to lastName.
    void setLastName(char* lastName);

    // sets the mark at index "index" of the student record to mark.
    // the method assumes the index is in 0-4 range, and 
    // the mark is in 0-100 range.
    void setMark(int index, unsigned int mark);

    // returns the student number.
    unsigned int getStudentNumber();

    // returns a pointer to the first name of the student record.
    char * getFirstName();

    // returns a pointer to the last name of the student record.
    char * getLastName();

    // returns the mark at index "index" of the student record.
    // it assumes the index is in 0-4 range.
    unsigned int getMark(int index);

    // prints the student record to the standard output in the format
    // specified in the assignment specifications.
    void print();
}; //studentRecord

#endif 

void setLastName( char* lastName )
{
  _lastname = lastName;
}

StudentRecord(string lastname, string firstname)
{
  _lastname = lastname;
  _firstname = firstname;
}