Отсортировать данные по фамилиям студентов в алфавитном порядке

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
 
#define FILE "C:\\STUDENTS"
 
struct STUDENT {
    char name[40];
    char lastname[40];
    unsigned short date[3];
    unsigned short subjects[5];
};
 
void getDatasFROMfile (STUDENT *students, unsigned int &counter);
void rating(STUDENT *students, int counter);
void ViewTable (STUDENT *students, int counter);
 
int main() {
 
    STUDENT students[30];
    unsigned int counter; // к-сть студентів
 
    getDatasFROMfile(students, counter);
    ViewTable(students, counter);
    rating(students, counter);
 
    return 0;
}
 
void getDatasFROMfile (STUDENT *students, unsigned int &counter) {
    counter = 0;
 
    ifstream out;
    out.open(FILE);
 
    char charDATE[11];
    char *nums;
 
    while ( !out.eof() ) {
        out >> students[counter].name;
        out >> students[counter].lastname;
        out >> charDATE;
        out >> students[counter].subjects[0];
        out >> students[counter].subjects[1];
        out >> students[counter].subjects[2];
        out >> students[counter].subjects[3];
        out >> students[counter].subjects[4];
 
            nums = strtok(charDATE, ".");
        students[counter].date[0] = atoi(nums);
            nums = strtok(NULL, ".");
        students[counter].date[1] = atoi(nums);
            nums = strtok(NULL, ".");
        students[counter].date[2] = atoi(nums);
 
        counter++;
    }
 
    out.close();
}
 
void rating(STUDENT *students, int counter) {
    double averageMarkOfGroup = 0.0; 
    int SumMarksOfOneStudent = 0;
    double averageMarkOfStudent = 0.0; 
 
    for (int i=0; i<counter; i++) {
        for (int j=0; j<5; j++) {
            SumMarksOfOneStudent += students[i].subjects[j];
        }
    }
 
    averageMarkOfGroup =  SumMarksOfOneStudent / ( 5.0 * counter );
    SumMarksOfOneStudent = 0;
 
    for (int i=0; i<counter; i++) {
        for (int j=0; j<5; j++) {
            SumMarksOfOneStudent += students[i].subjects[j];
        }
 
        if ( SumMarksOfOneStudent/5.0  <  averageMarkOfGroup ) {
            cout << students[i].name << " " << students[i].lastname << endl;
        }
        SumMarksOfOneStudent = 0;
    }
}
 
 
void ViewTable (STUDENT *students, int counter) {
    for (int i=0; i<counter; i++) {
        cout << students[i].name << "\t";
        cout << students[i].lastname << "\t";
        cout << students[i].subjects[0] << "\t";
        cout << students[i].subjects[1] << "\t";
        cout << students[i].subjects[2] << "\t";
        cout << students[i].subjects[3] << "\t";
        cout << students[i].subjects[4] << "\t";
        cout << "\n";
    }
    cout << "\n\n\n";
}