trivial_circular_queue_in_c

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

#define MAX 10

void enqueue();
void dequeue();
void display();
void peek();

int qArray[MAX];
int rear = -1;
int front = -1;

int main()
{
    int choice = 0;

    while (1)
    {
        printf("1. Insert\n2. Delete\n3. Display\n4. "
               "Peek\n5. Quit\nEnter your choice : ");
        scanf(" %d", &choice);

        switch (choice)
        {
        case 1:
            enqueue();
            break;
        case 2:
            dequeue();
            break;
        case 3:
            display();
            break;
        case 4:
            peek();
            break;
        case 5:
            exit(1);
        default:
            printf("Wrong choice \n");
        }
    }
    return 0;
}

void enqueue()
{
    int add_item;
    int newRear = ((rear + 1) % MAX);
    if (newRear == front)
        printf("Queue overflow \n");
    else
    {
        printf("Insert the element in queue : ");
        scanf(" %d", &add_item);
        if (front == -1)
        {
            front = 0;
            rear = 0;
            qArray[rear] = add_item;
        }
        else
        {
            rear = newRear;
            qArray[rear] = add_item;
        }
    }
}

void dequeue()
{
    if (front == -1)
    {
        printf("Queue underflow \n");
        return;
    }
    else
    {
        printf("Element deleted from queue is %d\n", qArray[front]);
        if (front == rear)
        {
            front = -1;
            rear = -1;
        }
        else
            front = ((front + 1) % MAX);
    }
}

void display()
{
    int i = 0;
    if (front == -1)
        printf("Queue is empty \n");
    else
    {
        i = front;
        printf("Queue is : \n[%d, ", qArray[i]);
        while (((i++) % MAX) != rear)
            printf("%d%s", qArray[i % MAX], (i) % MAX == rear ? "" : ", ");
        printf("]\n\n");
    }
}

void peek()
{
    if (front != -1)
        printf("front item = %d\n", qArray[front]);
    else
        printf("Queue is empty\n");
}