#include <iostream.h>

const int MAXQUEUE = 100;
const int TRUE = 1;
const int FALSE = 0;

// class declaration

// preconditions: requires that MAXQUEUE, the maximum size of the
//              : queue, be defined
//              : requires that TRUE be defined as a nonzero integer
//              : requires that FALSE be defined as 0

class Queue
{
  private:
    int queueIn;   // top-of-queue position
    int num[MAXQUEUE];

  public:
    Queue();   // constructor
    void enqueue(int);
    int serve();
    int isempty();
    int isfull();

};

// implementation section

Queue::Queue()  // constructor
{
  queueIn = -1;   // initialize the top-of-queue position
}

void Queue::enqueue(int value)
{
  queueIn++;   // increment the index stored in queueIn
  num[queueIn] = value;  // store the value

  return;
}

int Queue::serve()
{
  int i, botval;

  botval = num[0];       // retrieve the first array element
  for(i = 0; i < queueIn; i++)  // shift all elements down
    num[i] = num[i+1];
  queueIn--;

  return(botval);
}

int Queue::isempty()
{
  if (queueIn == -1)
    return TRUE;
  else
    return FALSE;
}

int Queue::isfull()
{
  if (queueIn == MAXQUEUE - 1)
    return TRUE;
  else
    return FALSE;
}

int main()
{
  Queue digits;    // define a Queue named digits
  int newnum;

  cout << "Enter as many digits as you wish, one per line"
       << "\nTo stop entering digits, enter a number greater than 9\n";
  while (1)
  {
    cout << "Enter a digit: ";
    cin  >> newnum;
    if (newnum > 9)
      break;
    if (digits.isfull()) // check for overflow
    {
      cout <<"\nNo more storage allocation space"
           << "\nThe last digit has not been entered on the queue"
           << endl;
      break;
    }
    else
      digits.enqueue(newnum); // enqueue value onto the queue
  }

    // serve and display digits from the queue

  cout << "\nThe values served from the queue are:\n";
  while(!digits.isempty())   // check for underflow
  {
    cout << digits.serve() << endl;
  }

  return 0;
}