Input restricted deque

#include <stdio.h>
#define SIZE 5

int deque[SIZE];
int front = -1, rear = -1;

int isFull()
{
    return (front == 0 && rear == SIZE - 1) || (front == rear + 1);
}

int isEmpty()
{
    return (front == -1);
}

void insertRear(int value)
{
    if (isFull())
    {
        printf("Deque is full.\n");
        return;
    }

    if (isEmpty())
    {
        front = rear = 0;
    }
    else if (rear == SIZE - 1)
    {
        rear = 0; // Wrap around manually
    }
    else
    {
        rear++;
    }

    deque[rear] = value;
}

void deleteFront()
{
    if (isEmpty())
    {
        printf("Deque is empty.\n");
        return;
    }

    printf("Deleted from front: %d\n", deque[front]);

    if (front == rear)
    {
        front = rear = -1;
    }
    else if (front == SIZE - 1)
    {
        front = 0; // Wrap around manually
    }
    else
    {
        front++;
    }
}

void deleteRear()
{
    if (isEmpty())
    {
        printf("Deque is empty.\n");
        return;
    }

    printf("Deleted from rear: %d\n", deque[rear]);

    if (front == rear)
    {
        front = rear = -1;
    }
    else if (rear == 0)
    {
        rear = SIZE - 1; // Wrap around manually
    }
    else
    {
        rear--;
    }
}

void display()
{
    if (isEmpty())
    {
        printf("Deque is empty.\n");
        return;
    }

    printf("Deque contents: ");
    int i = front;
    while (1)
    {
        printf("%d ", deque[i]);
        if (i == rear)
            break;

        if (i == SIZE - 1)
            i = 0;
        else
            i++;
    }
    printf("\n");
}

int main()
{
    int choice, value;

    while (1)
    {
        printf("\n--- Input-Restricted Deque (No Modulo) ---\n");
        printf("1. Insert at rear\n");
        printf("2. Delete from front\n");
        printf("3. Delete from rear\n");
        printf("4. Display\n");
        printf("0. Exit\n");
        printf("Choice: ");
        scanf("%d", &choice);

        switch (choice)
        {
        case 1:
            printf("Enter value: ");
            scanf("%d", &value);
            insertRear(value);
            break;
        case 2:
            deleteFront();
            break;
        case 3:
            deleteRear();
            break;
        case 4:
            display();
            break;
        case 0:
            return 0;
        default:
            printf("Invalid choice.\n");
        }
    }
}