title: what is NSZone? What are the advantages of using initWithZone:?
body: <p>There are so many functions like </p>
  
  <pre>
  1. NSDefaultMallocZone()
  2. NSCreateZone();
  3. NSRecycleZone();
  4. NSSetZoneName();
  5. NSZoneMalloc();
  and many more related to NSZone
  </pre>
  
  <p>What does NSZone means, where to use these functions and when?<br/>
  What are the advantages of initWithZone: and how to use in my iphone app?</p>