Circular Queue Implementation in C using array !

Circular_Queue.c

//Circular Queue Implementation in C using Array !


#include<stdio.h>         
#include<stdlib.h>        //header file for using return and exit function

#define max 5         //symbolic constant

int front=-1,rear=-1;       // global variable
int CQueue[max];          

void insert();
int delete();
void display();

main()
{
    int w,no;         
    for(;;)
    {
        printf("\n1. Insert");
        printf("\n2. Delete");
        printf("\n3. Display");
        printf("\n4. EXIT");
        printf("\nEnter what you want :");
        scanf("%d",&w);

        switch(w)
        {
        case 1:
            insert();
            break;
        case 2:
            no=delete();
            break;
        case 3:
            display();
            break;
        case 4:
            exit(1);
        default:
            printf("\nInvalid Choice !!\n");
        }
    }
}

void insert()
{
    int no;
    if((front ==0 && rear == max-1) || front == rear+1)
    {
        printf("\nCircular Queue Is Full !\n");
        return;
    }
    printf("\nEnter a number to Insert :");
    scanf("%d",&no);
    if(front==-1)
        front=front+1;
    if(rear==max-1)
        rear=0;
    else rear=rear+1;
        CQueue[rear]=no;
}

int delete()
{
    int e;
    if(front==-1)
    {
        printf("\nThe Circular Queue is Empty !!\n");
        return;
    }
    e=CQueue[front];
    if(front==max-1)
        front=0;
    else if(front==rear)
    {
        front=-1;
        rear=-1;
    }
    else front=front+1;
    printf("\n%d was deleted !\n",e);
    return e;
}

void display()
{
    int i;
    if(front==-1)
    {
        printf("\nThe Circular Queue is Empty ! Nothing To Display !!\n");
        return;
    }
    i=front;
    if(front<=rear)
    {
        printf("\n\n");
        while(i<=rear)
            printf("%d ",CQueue[i++]);
        printf("\n");
    }
    else
    {
        printf("\n\n");
        while(i<=max-1)
           printf("%d ",CQueue[i++]) ;
        i=0;
        while(i<=rear)
            printf("%d ",CQueue[i++]);
        printf("\n");
    }
}