title: Why subclass NSObject?
body: <p>What is the purpose/use of NSObject in Objective-C? I see classes that extend NSObject like this:</p>
  
  <pre><code>@interface Fraction : NSObject 
  </code></pre>
  
  <p>In C++ or Java, we don't use any variables like NSObject even though we have preprocessor directives and import statements in both Objective-C and Java. </p>
  
  <p>Why do classes explicitly inherit from NSObject in Objective-C? What are the consequences of not declaring inheritance from NSObject?</p>