c program for operations on queue using arrays

QUEUE OPERATIONS

#include<stdio.h>
#include<stdlib.h>
#define MAX 10

int queue_arr[MAX];
int rear=-1;
int front=-1;

void insert(int item);
int del();
int peek();
void display();
int isFull();
int isEmpty();

main()
{
int choice,item;
while(1)
{
 printf("1.Insert\n");
 printf("2.Delete\n");
 printf("3.Display element at the front\n");
 printf("4.Display all elements of the queue\n");
 printf("5.Quit\n");
 printf("Enter your choice : ");
 scanf("%d",&choice);

 switch(choice)
 {
 case 1:
printf("Input the element for adding in queue : ");
scanf("%d",&item);
insert(item);
break;
 case 2:
item=del();
printf("Deleted element is  %d\n",item);
break;
 case 3:
printf("Element at the front is %d\n",peek());
break;
 case 4:
display();
break;
 case 5:
exit(1);
 default:
printf("Wrong choice\n");
 }/*End of switch*/
}/*End of while*/
}/*End of main()*/

void insert(int item)
{
if( isFull() )
{
 printf("Queue Overflow\n");
 return;
}
if( front == -1 )
 front=0;
rear=rear+1;
queue_arr[rear]=item ;
}/*End of insert()*/

int del()
{
int item;
if( isEmpty() )
{
 printf("Queue Underflow\n");
 exit(1);
}
item=queue_arr[front];
front=front+1;
return item;
}/*End of del()*/

int peek()
{
if( isEmpty() )
{
 printf("Queue Underflow\n");
 exit(1);
}
return queue_arr[front];
}/*End of peek()*/

int isEmpty()
{
if( front==-1||front==rear+1 )
 return 1;
else
 return 0;
}/*End of isEmpty()*/

int isFull()
{
if( rear==MAX-1 )
 return 1;
else
 return 0;
}/*End of isFull()*/

void display()
{
int i;
if ( isEmpty() )
{
 printf("Queue is empty\n");
 return;
}
printf("Queue is :\n\n");
for(i=front;i<=rear;i++)
 printf("%d  ",queue_arr[i]);
printf("\n\n");
}/*End of display() */