add forward declaration

add classes

CPlusPlus/Classes/main.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+
+#include "Entity.h"
+#include "Monster.h"
+#include "Vector3.h"
+
+using namespace std;
+
+int main()
+{
+	Entity entity; // this is an entity instance
+	cout << entity.toString() << endl;
+
+	Monster monster;
+	cout << monster.toString() << endl;
+
+	Vector3 position;
+	Vector3 position2(1.0f, 0.0f, -10.0f);
+	Vector3 position3 = Vector3();
+	Vector3 position4{}; // list-initializer
+	Vector3 position5 = {}; // list-initializer assigned
+
+	return 0;
+}