Queue program in c using array with menu

 A queue is a linear data structure where elements are inserted from one end and deleted from other end. Element are inserted for rare and deleted from front of the queue.

#include <stdio.h>
#define MAX 10 

int queue[MAX];
int front = -1, rear = -1;

void insert()
{
int num;
printf("n Enter the number to be inserted in the queue :n");
scanf("%d", &num);
if(rear == MAX-1)
printf("n OVERFLOW");
else if(front == -1 && rear == -1)
front = rear = 0;
else
rear++;
queue[rear] = num;
}

int delete_element()
{
int val;
if(front == -1 || front>rear)
{
printf("n UNDERFLOW");
return -1;
}
else
{
val = queue[front];
front++;
if(front > rear)
front = rear = -1;
return val;
}
}

int peek()
{
if(front==-1 || front>rear)
{
printf("n QUEUE IS EMPTY");
return -1;
}
else
{
return queue[front];
}
}


void display()
{
int i;
if(front == -1 || front > rear)
printf("n QUEUE IS EMPTYn");
else
{
for(i = front;i <= rear;i++)
printf("%d t", queue[i]);
}
}


void main()
{
int option, val;
do
{
	printf("n***** MAIN MENU *****");
	printf("n 1. Insert an element");
	printf("n 2. Delete an element");
	printf("n 3. Peek");
	printf("n 4. Display the queue");
	printf("n 5. EXIT");
	printf("n Enter your option : n");
	scanf("%d", &option);
	switch(option)
		{
		case 1:
			insert();
		break;
		case 2:
			val = delete_element();
			if (val != -1)
			printf("n The number deleted is : %dn", val);
		break;
		case 3:
			val = peek();
			if (val != -1)
			printf("n The first value in queue is : %dn", val);
		break;
		case 4:
		    display();
		break;
	}
}while(option != 5);
getch();
}