// main .cpp file
#include <iostream>
#include "Room.h"

using namespace std;

CRoom Rooms[14]={1,2,3,4,5,6,7,8,9,10,11,12,13,14};

void main()
{

	title();

	Rooms[1].set_door(0,2,0,1);
	Rooms[2].set_door(7,1,9,11);
	Rooms[3].set_door(9,0,0,10);
	Rooms[4].set_door(0,10,0,0);

// ...etc etc

// another .cpp file

#include <iostream>
#include "Player.h"

using namespace std;

CPlayer::~CPlayer()
{

}

void CPlayer::move(int direction)
{
     Rooms[1].set_door(1,2,3,4); 

// errors occurs when this line is include e.g.
// 'Rooms' : undeclared identifier
// subscript requires array or pointer type
// left of '.set_door' must have class/struct/union type

}

#include <iostream>
#include "Player.h"

extern CRoom Rooms[14]; // newly added

using namespace std;

CPlayer::~CPlayer()
{

}

void CPlayer::move(int direction)
{
      Rooms[1].set_door(1,2,3,4);
}