Lab6.c

#include <stdio.h>
#define SIZE 4
int rear = -1, front = -1;
char queue[SIZE];
char item;
void insert()
{
    if (front == ((rear + 1) % SIZE))
        printf("Queue is full.\n");
    else
    {
        rear = (rear + 1) % SIZE;
        printf("Enter ITEM: ");
        scanf("%*c%c", &item);
        queue[rear] = item;
        printf("Item inserted: %c\n", item);
        if (front == -1) /* first element insertion into queue used for deletion */
            front++;
    }
}
void del()
{
    if (front == -1)
        printf("Queue is empty.\n");
    else
    {
        item = queue[front];
        printf("ITEM deleted: %c\n", item);
        if (front == rear)
        {
            front = rear = -1;
        }
        else
            front = (front + 1) % SIZE;
    }
}
void display()
{
    int i, j;
    if (front == -1)
        printf("Queue is empty.\n");
    else
    {
        printf("Elements of queue are\n");
        i = front;
        while (i != rear)
        {
            printf("%c ", queue[i]);
            i = (i + 1) % SIZE;
        }
        printf("%c ", queue[i]);
        printf("\n");
    }
}
main()
{
    int choice;
    while (1)
    {
        choice = 0; /* to select default option of switch when non-integer */
        printf("\nCircular Queue Operations:\n");
        printf("1.Insert \n2.Delete \n3.Display \n4.Exit \n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
        switch (choice)
        {
        case 1:
            insert();
            break;
        case 2:
            del();
            break;
        case 3:
            display();
            break;
        case 4:
            return;
        default:
            printf("Invalid choice.\n");
            return;
        }
    }
}