queue using linked list.c

#include<stdio.h>
#include<stdlib.h>

struct node
{
	int data;
	struct node *link;
}*front = NULL, *rear = NULL;

int isEmpty()
{
	if(front == NULL)
	{
		return 1;
	}
	else
	{
		return 0;
	}
}

void insert(int item)
{
	struct node *temp;
	temp = (struct node *)malloc(sizeof(struct node));
	if(temp == NULL)
	{
		printf("Queue is not Allocated\n");
		return;
	}
	temp->data = item;
	temp->link = NULL;
	if(front == NULL)
	{
		front = temp;
	}
	else
	{
		rear->link = temp;
	}
	rear = temp;
}

int delete_node()
{
	struct node *temp;
	int item;
	if(isEmpty())
	{
		printf("Queue is Empty\n");
		exit(1);
	}
	temp = front;
	item = temp->data;
	front = front->link;
	free(temp);
	return item;
}

int front()
{
	if(isEmpty())
	{
		printf("Queue is Empty\n");
		exit(1);
	}
	return front->data;
}

void display()
{
	struct node *ptr;
	if(isEmpty())
	{
		printf("Queue is Empty\n");
		return;
	}
	printf("Queue Elements (or Nodes):\n");
	for(ptr = front; ptr != NULL; ptr = ptr->link)
	{
		printf("%d ", ptr->data);
	}
	printf("\n\n");
}

int main()
{
	int option, item;
	while(1)
	{
		printf("1. Insert an Element in the Queue\n");
		printf("2. Delete an Element from the Queue\n");
		printf("3. Display Element at the Front position\n");
		printf("4. Display All Elements of the queue\n");
		printf("5. Exit\n");
		printf("Enter your option:\t");
		scanf("%d", &option);
		switch(option)
		{
			case 1:
				printf("Enter the Element to Add in Queue:\t");
				scanf("%d", &item);
				insert(item);
				break;
			case 2:
				printf("The Deleted Element from the Queue:\t%d\n", delete_node());
				break;
			case 3:
				printf("Element at the Front:\t%d\n", front());
				break;
			case 4:
				display();
				break;
			case 5:
				exit(1);
			default:
				printf("Wrong option\n");
		}
	}
        return 0;
}