text: #ifndef _QUEUE_H
  #define _QUEUE_H
  
  typedef char queueElementT;
  
  typedef struct queueTag {
      queueElementT element;
      struct queueTag *next;
  } queueNodeT;
  
  typedef struct {
      queueNodeT *firstNode;
      queueNodeT *lastNode;
  } queueT;
  
  void QueueInit(queueT *queueP);
  
  void QueueDestroy(queueT *queueP);
  
  void Enqueue(queueT *queueP, queueElementT element);
  queueElementT Dequeue(queueT *queueP);
  
  int QueueIsEmpty(queueT *queueP);
  
  #endif
  