title: In Objective C does every user class extend NSObject by default?
body: <p>While going through an Objective C programming book just now . I noticed this code <br></p>
  
  <pre><code>@interface Fraction: NSObject
  {
     int  numerator;
     int  denominator;
  }
  
  -(void)   print;
  -(void)   setNumerator: (int) n;
  -(void)   setDenominator: (int) d;
  
  @end
  </code></pre>
  
  <p>Author does great job in explaining every thing in this book but there is no mention on whether this is same as just</p>
  
  <pre><code> @interface Fraction
      {
         int  numerator;
         int  denominator;
      }
  
      -(void)   print;
      -(void)   setNumerator: (int) n;
      -(void)   setDenominator: (int) d;
  
      @end
  </code></pre>
  
  <p>reason I am asking this rather very simple question is that in JAVA every thing by default extends Object and you do not need to say that. Now of course they are two very different languages but it was a natural question that came to my mind.</p>