circular queue

#include <stdio.h>
#define n 5
int queue[n];
int front =-1;
int rear =-1;
void insert();
void delete();
void display();
void peek();

int main()
{
    int choice;
    while(1)
    {
        printf("\t\t\t1.Insert");
        printf("\n\t\t\t2.Delete");
        printf("\n\t\t\t3.Display");
        printf("\n\t\t\t4.Top");
        printf("\n\t\t\t5.Quit");
        printf("\nEnter your choice: ");
        scanf("%d",&choice);
        switch(choice)
        {
            case 1: insert();
                    break;
            case 2: delete();
                    break;
            case 3: display();
                    break;
            case 4: peek();
                    break;
            case 5: exit(1);
                    break;
           default: printf("error\n");
        }
        fflush(stdin);
    }
}
void insert()
{
    int x;
    printf("Enter the value to insert: ");
    scanf("%d",&x);
    if(front==-1 && rear==-1)
    {
        front=rear=0;
        queue[rear]=x;
    }
    else if(((rear+1)%n)== front)
    {
        printf("Queue is full.Overflow");
    }
    else
    {
        rear =(rear+1)%n;
        queue[rear]=x;
    }
}
void delete()
{
    if(front==-1 && rear==-1)
    {
        printf("Underflow");
    }
    else if(front == rear)
    {
        front=rear=-1;

    }
    else
    {
        printf("Dequeued:%d\n",queue[front]);
        front=(front+1)%n;
    }
}
void display()
{
    int i=front;
    if(front==-1 && rear==-1)
    {
        printf("Queue is empty");
    }
    else
    {
        printf("\n\nQueue elements are\n");
        while(i!=rear)
        {
            printf("%d\t",queue[i]);
            i=(i+1)%n;
        }
       printf("%d",queue[rear]);
    }
}
void peek()
{
    if(front==-1 && rear==-1)
    {
        printf("it is empty\n");
    }
    else
    {
        printf("\n\nPeek element:%d\n",queue[front]);
    }
}