queue

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define max 100
void insert();
void delete_item();
void display();
int queue[max];
int front=-1;
int rear=-1;
int main()
{
		int choice;
		while(1)
	{
		printf("1.insert item in queue: ");
		printf("\n2.delete item from queue: ");
		printf("\n3.display items of queue: ");
		printf("\n4.exit.");
		printf("\nEnter your choice: ");
		scanf("%d", &choice);
		switch(choice)
		{
			case 1:
			insert();
			break;
			case 2:
			delete_item();
			break;
			case 3:
			display();
			break;
			case 4:
			exit(1);
			default:
			printf("Wrong choice!\n");
		}
	}
}
void insert()
{
	int item;
	if(rear==max-1)
	{
		printf("overflow!");
	}
	else
	{
		if(front==-1)
		front=0;
		printf("insert the item in queue: ");
		scanf("%d", &item);
		rear++;
		queue[rear]=item;
	}
	
}
void delete_item()
{
	if(front==-1 || front>rear)
	{
		printf("underflow!");
		return;
	}
	else
	{
		printf("deleted item is %d: \n", queue[front]);
		front=front+1;
	}
}
void display()
{
	int i;
	if(front==-1)
	{
		printf("Underflow!");
	}
	else
	{
	printf("Queue is : \n");
	for(i=front;i<=rear;i++)
	printf("%d  ", queue[i]);
	printf("\n");
	}
}