title: Unique Queue Overflow Condition (having less elements than its size)
body: <p>Got this competitive question:</p>
  
  <pre><code>Which of the following data structure may give overflow error, even though the current number of elements in it is less than its size?
  
  a. Stack 
  
  b. Circular queue 
  
  c. Simple queue                        
  
  d. None of the above  
  </code></pre>
  
  <p>I tried to Google the answer for a proper explanation however several sources marked (c) and (b) as answers which confused me even more. What's the explanation and the proper answer? 
  Thanks.</p>