c++ Class containing vectors of other Classes - c++

Question

I am trying to make a program that has "Class University" that contains a vector for "class Department" [vector Departments]. Inside of the "class Department" under public I have two constructors and a print function.
In my University.cpp, I am trying to make a function that adds a new object Department and puts it into the vector Departments in "University". I believe I am doing this wrong because I am trying to call the constructor for Department() in the University function and I am getting this error message:
$ g++ University.cpp
/usr/li`enter code here`b/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
/tmp/cc6XExwc.o: In function `University::CreateNewDepartment(std::string, std::string, long)':
University.cpp:(.text+0x7d): undefined reference to `Department::Department(std::string, std::string, long)'
collect2: error: ld returned 1 exit status
Class Departments has the following private variables (long id, string name, string location, long chairID). Do I need to use a set() function to create the object, and if so how would I go about doing this?
University.h below
#include <string>
#include <vector>
#include <iostream>
#include <fstream>
using namespace std;
#include "Person.h"
#include "Student.h"
#include "Faculty.h"
#include "Department.h"
#include "Course.h"
class University
{
protected:
vector<Department> Departments;
vector<Student> Students;
vector<Course> Courses;
vector<Faculty> Faculties;
public:
University();
~University();
bool CreateNewDepartment(string depName, string depLoc, long depChairId);
University.cpp below
#include <string>
#include <vector>
#include <iostream>
#include <fstream>
using namespace std;
#include "University.h"
bool University::CreateNewDepartment (string n, string l, long c)
{
if ( (c != 0) && (!validFaculty (c) ))
return false;
Department D (n, l, c);
Departments.push_back (D);
return true;
}
Department.h
#ifndef DEPARTMENT_H
#define DEPARTMENT_H
#include <string>
#include <iostream>
using namespace std;
class Department
{
friend class University;
protected:
long id;
string name;
string location;
long chairId;
static long nextDepartId;
public:
Department();
Department(string n, string l, long c);
void Print() const;
};
#endif
Department.cpp
#include "Department.h"
using namespace std;
#include <string>
long Department::nextDepartId;
Department::Department()
{
id = chairId = 0;
name = location = " ";
}
Department::Department(string n, string l, long c)
{
name = n;
location = l;
chairId = c;
}
void Department::Print() const
{
cout << "Name: " << name << endl;
cout << "Id: " << id << endl;
cout << "Location: " << location << endl;
cout << "Chair id: " << chairId << endl;
}

Answer 1

As said in the comments by #SteveHolodnak and #M.M., you have two undefined reference problems here.
No main function.
Undefined reference to Department::Department()
Using g++ main.cpp University.cpp Department.cpp where main.cpp is your file with your main function should solve all your problems.