This class provides facilities for putting objects into a queue. A
  queue is a data structure with an associated list of objects of the
  object class, or a class derived from the object class in first-in,
  first-out order. All access to a queue is through either the attached
  qhead or the attached qtail.  You create a queue by creating either a
  qhead or a qtail. The other end of the queue is created automatically.
  You can then obtain a pointer to the head with the qtail::head
  function.

  Objects have definitions of when they are ready and pending (not
  ready). The qtail objects are ready when the queue is not full and
  pending when the queue is full.