4.Circular Queue (DS)

#include<stdio.h>
#include<conio.h>
#define max 100
#define pf printf
#define sf scanf_s
typedef struct
{
    int q[max];
    int r,f,flag;
}queue;
int  isempty(queue *t)
{
    if(t->flag==0)
    return 1;
    else return 0;
}
void insert(queue *t,int ele)
{
    if(t->f==(t->r+1)%max && t->flag==1)
    {
        pf("\nCircular Queue Overflow\n");
        return;
    }
    t->flag=1;
    t->r=(t->r+1)%max;
    t->q[t->r] = ele;
    return;
}
void delete1(queue *t)
{
    int z;
    if(isempty(t))
    {
        pf("\nCircular Queue Underflow\n");
        return;
    }
    if(t->f==t->r)
    {
    t->flag=0;
    }
    z = t->q[t->f];
    t->f=(t->f+1)%max;
    pf("\nDeleted element is %d",z);
    return;
}
void display(queue *t)
{
    int i;
    if(isempty(t))
    {
        pf("\nCircular Queue Underflow\n");
        return;
    }
    for(i=t->f;i<=t->r;i=(i+1)%max)
    {
        pf("%d\n",t->q[i]);
    }
    return;
}
int main()
{
    int ch,ele;
    queue x;
    x.f=0;
    x.flag=0;
    x.r=-1;
    pf("\nIMPLEMENTATION OF CIRCULAR QUEUE\n");
    while(1)
    {
        pf("\nEnter choice\n");
        pf("\n1.Insert 2.Delete 3.Display 4.Exit\n");
        sf("%d",&ch);
        if(ch==4)
        {
            break;
        }
        else
        {
            switch(ch)
            {
            case 1:pf("\nEnter element to insert\n");
                sf("%d",&ele);
                insert(&x,ele);
                break;
            case 2:delete1(&x);
                break;
            case 3:display(&x);
                break;
            default:pf("\nINVALID INPUT\n");
            }
        }
    }
    _getch();
    return 0;
}