Circular Queue using Array

This is a simple implementation of Circular Queue using arrays.
A Circular Queue is a Data Structure in which the data is stored in a circular manner , i.e. the array can be reused from the front also.

 #include <iostream>
#include <stdlib.h>

void err_quit(char* msg)
{
  printf("%s\n",msg);
  exit(0);
}

using namespace std;
class cirq{

  int cirq_len;
  int *queue;
  
  public:
    
  int front;
  int rear;
  cirq(int size);
  ~cirq();
  void insert_rear(int item);
  void delete_front();
  void show();
};

cirq::cirq(int size = 0)
{
  front = -1;
  rear = -1;
  cirq_len = size;

  queue = new int[size]; 
}
cirq::~cirq()
{
  delete[] queue;
}

void cirq::insert_rear(int item)
{

  if((front == 0)&& (rear == cirq_len - 1) || (rear + 1 == front))
  {
    err_quit("Queue Overflow!!!");
  }
  
  if(rear == -1)
  {
      front = rear = 0;
  }
  else if(rear == (cirq_len - 1))
  {
      rear  = 0;
  }
  else 
    rear++;
  
  queue[rear] = item;

}
       
void cirq::delete_front()
{ 
  if(front == -1 || rear == -1)
  {
    err_quit("Queue Underflow!!!");
  }
  front++;
 
}
       
void cirq::show()
{
  int i;
  if( front == -1 || rear == -1)
  {
    cout<<"Queue is empty!!!";
    return;
  }

  if(front < rear)
    for(i = front ; i <= rear; i++)
      cout<<queue[i]<<" ";

  else
  {
    for(i = front ; i <= (cirq_len - 1); i++)
      cout<<queue[i]<<" ";
    for(i = 0 ; i <= rear ; i++)
      cout<<queue[i]<<" ";
      
  }
  cout<<endl;
}

       
int main()
{
  int ch;
  cirq c1(5); 
  c1.show();
  c1.insert_rear(1);
  c1.show();
  c1.insert_rear(2);
  c1.show();
  c1.insert_rear(3);
  c1.show();
  c1.insert_rear(4);
  c1.show();
  c1.insert_rear(5);
  c1.show();

  c1.delete_front();
  c1.show();
  c1.delete_front();
  c1.show();
  c1.insert_rear(6);
  c1.show();
  c1.insert_rear(7);
  c1.show();
  c1.insert_rear(7);
  c1.show();
  c1.insert_rear(7);
  c1.show();
  
}