#include <stdio.h>

#define MAX 50

void qinsert();
void qremove();
void display();
int queue[MAX];
int rear = - 1;
int front = - 1;
main()
{
    char choice;
    while (1)
    {
        printf("U.Insert element to queue \n");
        printf("O.Eemove element from queue \n");
        printf("D.Display all elements of queue \n");
        printf("E.Quit \n");
        printf("Enter your choice : ");
        scanf(" %c", &choice);
        switch (choice)
        {
            case 'U':
            qinsert();
            break;
            case 'O':
            qremove();
            break;
            case 'D':
            display();
            break;
            case 'E':
            exit(1);
            default:
            printf("Wrong character! \n");
        } /* End of switch */
    } /* End of while */
} /* End of main() */

void qinsert()
{
    int add;
    if (rear == MAX - 1)
    printf("Queue Overflow \n");
    else
    {
        if (front == - 1)
        /*If queue is initially empty */
        front = 0;
        printf("Inset the element in queue : ");
        scanf("%d", &add);
        rear = rear + 1;
        queue[rear] = add;
    }
} /* End of qinsert() */

void qremove()
{
    if (front == - 1 || front > rear)
    {
        printf("Queue Underflow \n");
        return ;
    }
    else
    {
        printf("Element qremoved from queue is : %d\n", queue[front]);
        front = front + 1;
    }
} /* End of qremove() */

void display()
{
    int i;
    if (front == - 1)
        printf("Queue is empty \n");
    else
    {
        printf("Queue is : \n");
        for (i = front; i <= rear; i++)
            printf("%d ", queue[i]);
        printf("\n");
    }
} /* End of display() */