#include <iostream>
#include <string>
using namespace std;

const int number_students = 15;

struct student
{
	string ID;
	int mark;
	// add name here
};

student classroom[number_students];

void initialize_classroom();
void print_classroom();
int select_student();
void modify_student(int n);

int main()
{
	int n;
	initialize_classroom();
	while(true)
	{
		print_classroom();
		n = select_student();
		if (n==-1) break;
		modify_student(n);
	}
	// save to file here
	return 0;
}

void initialize_classroom()
{
	// read from file here instead
	for(int i=0;i<number_students;i++)
	{
		classroom[i].ID = "(no ID)";
		classroom[i].mark = 0;
	}
}

void print_classroom()
{
	cout << "\tID  \tMark" << endl; // fix this
	cout << "\t~~  \t~~~~" << endl;
	for(int i=0;i<number_students;i++)
	{
		cout <<  i << "\t";
		cout << classroom[i].ID << "\t";
		cout << classroom[i].mark << endl;
		// also display name
	}
}

int select_student()
{
	int selection;
	do
	{
		cout << "Select student (0-"<<number_students-1<<") or -1 to exit: ";
		cin >> selection;
	}
	while (selection < -1 || selection >= number_students);
	return selection;
}

void modify_student(int n)
{
	cout << "Student   ID: " << classroom[n].ID << endl;
	cout << "Student Mark: " << classroom[n].mark << endl;
	if (classroom[n].ID == "(no ID)")
	{
		cout << "Enter Student ID: ";
		cin >> classroom[n].ID;
	}
	cout << "Enter New student mark: ";
	cin >> classroom[n].mark;
	// also modify name
}