title: How to differentiate Null or Empty ? on what criteria Null and Empty treated?
body: <p>Hi all of SO users I'm having little confusion with understanding null and Empty. 
  I know null is special case, which is not equal to itself. I want to know how to determine  that it is null, on what basis you are telling it is null, and the same for empty also </p>
  
  <ol>
  <li>Is it based on memory allocation or what? </li>
  <li>If then how memory allocated for null.</li>
  <li>If its empty then what crieteria suits for it to be as "EMPTY".</li>
  </ol>
  
  <p>Just I want know how the compiler come to know it is NULL or Empty.</p>