Implementation of Queue in C using array

#include <stdio.h>

#include<stdlib.h>
#define MAX 5
void insert();
void delete();
void display();
int que[MAX];
int rear = - 1;
int front = - 1;
int main()
{
  int choice;
  printf("1.Insert element to queue \n");
  printf("2.Delete element from queue \n");
  printf("3.Display all elements of queue \n");
  printf("4.Quit \n");
  while(1)
  {
   printf("Enter your choice : ");
   scanf("%d", &choice);
   switch(choice)
   {
    case 1: insert();  break;
    case 2: delete();  break;
    case 3: display(); break;
    case 4: exit(1);
    default: printf("Wrong choice \n");
   }
  }
}
void insert()
{
 int item;
 if(rear == MAX - 1)
 printf("Queue Overflow \n");
 else
 {
  if(front== - 1)
  front = 0;
  printf("Inset the element in queue : ");
  scanf("%d", &item);
  rear = rear + 1;
  que[rear] = item;
 }
}

void delete()
{
 if(front == - 1 || front > rear)
 {
  printf("Queue Underflow \n");
  return;
 }
 else
 {
  printf("Element deleted from queue is : %d\n", que[front]);
  front = front + 1;
 }
}

void display()
{
 int i;
 if(front==- 1)
 printf("Queue is empty \n");
 else
 {
  printf("Queue is : \n");
  for(i = front; i <= rear; i++)
    printf("%d ", que[i]);
    printf("\n");
 }
} 

Output: