Dangling Pointer

Last night I was trying my hand on C++ .... and I came across an interesting problem ...
all I was trying to do following
1) create a class ( say TestClass ) which will have an int variable( age ), and we can set value into this variable using 2 methods(set and get).
2) create a global scope pointer of this type in the file.( say m_TestClass ) ...
3) write a method( say createTestClassObject ) where I will create an object of the class "TestClass" and the pointer( m_TestClass ) will point to this object.
then I will do a set and get( printf ).
4) "createTestClassObject" method will be called from the main and after this method returns to main .. I will do another m_TestClass->getAge()( priintf ) .
This is what I have written ...( I have used .NET IDE )

#include "stdafx.h"
#include "stdio.h"
#include "iostream"
#include "conio.h"
#using
using namespace System;
using namespace std;

void createTestClassObject();


class TestClass
{
int m_Age;
public:
TestClass()
{
// dummy constructor
}

void setAge( int age )
{
m_Age = age;
}

int getAge()
{
return m_Age;
}
};

TestClass *m_TestClass;
int main()
{
createTestClassObject();
printf("\n%d", m_TestClass->getAge() );
int i = getch();
return 0;
}

void createTestClassObject()
{
TestClass obj;
m_TestClass = &obj;
m_TestClass ->setAge(100);
printf("\n%d", m_TestClass->getAge());
}

the output of the program is first 100 and then it is 4( sometime it is 6, sometime some crazy values), I was wondering why not my program is printing 100 twice?

After spening some time on it I got the cause .. as "obj" has a local scope( in the routine createTestClassObject ), hence the object dies when program flow returns to "main" and m_TestClassbecome a Dangling Pointer( I hope I am correct :) ).

I was just trying out several options to fix this issue ... and one of them paid off , this is what I did ...
I have just modified the createTestClassObject routine .. and the updated version looks like........
void createTestClassObject()
{
TestClass *obj = new TestClass();
m_TestClass = obj;
m_TestClass ->setAge(100);
printf("\n%d", m_TestClass->getAge());
}

All I have changed is created a pointer of TestClass and it points to new instance of TestClass, and it started working, but all in all I am confused, doesn't the object( new TestClass() )get dies when the routine returns to the main function ? I am in dark, can anybody please throw some light.
Neo.