Why doesn't my code work?

Question

Hi everyone!
I created this code and separated the header & the source file, but it doesn't work.
Take a look:

main.cpp:
-------------------------------------------
#include <iostream>
#include <string>
#include "person.h"
using namespace std;

int main()
{
person John;
John.print_name("John");
John.print_age(61);
John.print_birthplace("England");
John.set_NSN(136);
John.print_NSN();
return 0;
}
------------------------------------------------------

person.h:
----------------------------------------------------
#ifndef PERSON_H
#define PERSON_H

class person
{
public:
person();

void print_name(string name);

void print_age(int age);

void print_birthplace(string birthplace);

void set_NSN(int x);

void print_NSN();

protected:

private:
int NSN;
};

#endif // PERSON_H
---------------------------------------------

person.cpp:
---------------------------------------------
#include "person.h"

person::person()
{
cout<<"person:\n";
}

void person::print_name(string name="John")
{
cout<<name<<endl;
}

void person::print_age(int age=66)
{
cout<<age<<endl;
}

void person::print_birthplace(string birthplace="England")
{
cout<<birthplace<<endl;
}

void person::set_NSN(int x=136)
{
NSN=x;
}

void person::print_NSN()
{
cout<<NSN;
}

Answer 1

It worked.
Thanks a lot!