Queue c program

#define true 1
#define false 0

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

struct queue_point {
    int element;
    struct queue_point *n;
};

struct queue_point *f_ptr = NULL;

int is_que(void);

void add_ele(int);

int remove_ele(void);

void show_ele();

int main()
{
    int ele, choice, j;

    printf("1 To insert an element");
    printf("\n2 To remove an element");
    printf("\n3 To display all the elements");
    printf("\n4 Exit\n");
    while (1)
    {
        printf("\nEnter your choice: ");
        scanf("%d", &choice);

        switch (choice)
        {
            case 1:
            {
                printf("\nElement to be inserted: ");
                scanf("%d", &ele);
                add_ele(ele);
                break;
            }

            case 2:
            {
                if (!is_que())
                {
                    j = remove_ele();
                    printf("\n%d is removed from the queue", j);
                    printf("\n");
                }
                else
                {
                    printf("\nQueue is Empty.\n");
                }
                break;
            }

            case 3:
                show_ele();
                break;

            case 4:
                exit(1);
                break;

            default:
                printf("\nInvalid choice.\n");
                break;
        }

    }
    return 0;
}

/* Function to check if the queue is empty*/
int is_que(void)
{
    if (f_ptr == NULL)
        return true;
    return false;
}

/* Function to add an element to the queue*/
void add_ele(int element)
{
    /*dynamically allocate the memory*/
    struct queue_point *queue = (struct queue_point *) malloc(sizeof(struct queue_point));

    queue->element = element;
    queue->n = NULL;
    if (f_ptr == NULL)
    {
        f_ptr = queue;
    }
    else
    {
        struct queue_point *ptr;
        ptr = f_ptr;
        for (ptr = f_ptr; ptr->n != NULL; ptr = ptr->n);
        ptr->n = queue;
    }
}

/* Function to remove an element from the queue*/
int remove_ele()
{
    struct queue_point *queue = NULL;
    if (is_que() == false)
    {
        int j = f_ptr->element;
        queue = f_ptr;
        f_ptr = f_ptr->n;

        /*If you have allocated a memory block with the functions malloc(), calloc()
        or realloc() then you need to free the previously allocated memory.*/

        free(queue);
        return j;
    }
    else
    {
        printf("\nQueue is empty.\n");
        return -9999;
    }
}

/* Function to display the queue*/
void show_ele()
{
    struct queue_point *ptr = NULL;
    ptr = f_ptr;
    if (is_que())
    {
        printf("\nQUEUE is Empty.\n");
        return;
    }
    else
    {
        printf("\nElements present in Queue are: ");
        while (ptr != NULL)
        {
            printf("%d\t", ptr->element);
            ptr = ptr->n;
        }
        printf("\n");
    }
}

Output :

1 To insert an element
2 To remove an element
3 To display all the elements
4 Exit

Enter your choice: 1

Element to be inserted: 10

Enter your choice: 1

Element to be inserted: 12

Enter your choice: 2

10 is removed from the queue

Enter your choice: 1

Element to be inserted: 19

Enter your choice: 3

Elements present in Queue are: 12       19

Enter your choice: 4