92 E7

#include<iostream> using namespace std;

const int maxqueue = 10; 

class Queue

{ 

public:   Queue( );

  bool empty( ) const;  

Error_code serve( );  

Error_code append(const Queue_entry item);  

Error_code retrieve(Queue_entry item) const;

protected:   int front,rear;   Queue_entry entry [maxqueue];  

bool is_empty; };

Queue :: Queue( )  

{rear = maxqueue-1;   front = 0;   is_empty = true;}

bool Queue :: empty( ) const  

{return is_empty;}

Error_code Queue :: append(const Queue_entry item)

  if (!empty( )&&(rear+1)%maxqueue ==  front) return overflow;  

is_empty = false;  

rear=(rear+1)%maxquene;  

entry[rear]=item;  

return success;

}

Error_code Queue :: serve( )

 {

if(empty( ))return underflow;

  if(rear==front)is_empty = true;  

front=((front+1)==maxqueue)?0:(front+1);   return success;

}

Error_code Queue::retrieve(Queue_entry item)

const  {

if

(

empty( ))return underflow;

  item=entry[front];

  return success;

}