Queue Operations

Enqueue(queue, n, front, rear, item)//inserts item into a queue
1.	[queue already filled?]
If front := 1 and rear := n or front := rear +1 then:
Print OVERFLOW and return
2.	[find new value of rear]
If front : =NULL , then [Q initially empty]
Set front := 1 and rear := 1;
Else if rear := n then set  rear := 1;
Else set  rear : = rear + 1;
3.	Set queue[rear] := item [inserts new element].
4.	Return;

Dequeue(queue, n, front, rear, item) //deletes element from q and assign it to variable item.
1.	[Queue already empty?]
If front := NULL then : print UNDERFLOW and return.
2.	Set item : = queue[front].
3.	[find new value of front]
If front=rear then, [queue has only one element]
Set front=rear=NULL;
Else if front=n then : set front := 1;
Else set  front : = front +1;
4.	Return.

#include<stdio.h>
#include<conio.h>

int arr[50],n;
int rear=-1;
int front=-1,flag=0;
void isfull()
{
       if (rear==n-1)
 	 {
		printf("Queue Overflow\n");
		flag=1;
	 }
}
void isempty()
{
	if (front == -1||front>rear)
	{
		printf("Queue Underflow\n");
		flag=1;
	}
}
void insert()
{
	int added_item;
	isfull();
	if(flag==0)
	{
		if (front==-1)
			front=0;
		printf("Input the element for adding in queue : ");
		scanf("%d", &added_item);
		rear=rear+1;
		arr[rear] = added_item ;
	}
}
void del()
{
	isempty();
	if(flag==0)
	{
		printf("Element deleted from queue is : %d\n",arr[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\t ",arr[i]);

	}
}
void size()
{
 	int s= rear-front+1;
	printf("\n size of queue is %d ",s);
}
void fron()
{
	printf("front element is %d ",arr[front]);
}

int main()
{
	int choice;
	printf("length of queue is ");
	scanf("%d",&n);
	while(1)
	{
		printf("\n\n1.Insert\n");
		printf("2.Delete\n");
		printf("3.Display\n");
		printf("4.Front element\n");
		printf("5.Size\n");
		printf("6: queue is full\n");
		printf("7: queue is empty\n");
		printf("8.Quit\n");
		printf("Enter your choice : ");
		scanf("%d",&choice);
		switch(choice)
		{
			case 1 :insert();
			break;
			case 2 :del();
			break;
			case 3:display();
			break;
			case 4:fron();
			break;
			case 5:size();
			break;
			case 6:isfull();
			break;
			case 7:isempty();
			break;
			case 8:exit(1);
			default:
			printf("Wrong choice\n");
		}
	}
	return 0;
}