Learn GCD now and can't find any example of QOS_CLASS_DEFAULT usage
<p>I found many examples of any global queue usage but couldn't find any example of QOS_CLASS_DEFAULT usage. 
Can someone provide any info when we have to use it.</p>

<p>I just know that it's priority is lower that QOS_USER_INITIATED (DISPATCH_QUEUE_PRIORITY_HIGH) and higher that QOS_CLASS_UTILITY (DISPATCH_QUEUE_PRIORITY_LOW).</p>

<p>Thank you for any explanation!</p>