5.Priority Queue using array (DS)

#include<conio.h>
#include<stdio.h>
#define max 100
typedef struct
{
    int q[max];
    int f,r;
}queue;
int isempty(queue *t)
{
    if(t->f==t->r+1)
        return 1;
    else return 0;
}
void insert(queue *t,int ele)
{
    if(t->r==max-1)
    {
        printf("\nQUEUE OVERFLOW\n");
        return ;
    }
    t->r++;
    t->q[t->r] = ele;
    return;
}
void delete1(queue *t)
{
    int i,max1,pos;
    if(isempty(t)==1)
    {
        printf("\nQUEUE UNDERFLOW\n");
        return ;
    }
    max1 = t->q[t->f];
    pos = t->f;
    for(i=t->f+1;i<=t->r;i++)
    {
        if(max1<(t->q[i]))
        {
            max1=t->q[i];
            pos=i;
        }
    }
    for(i=pos;i<t->r;i++)
    {
        t->q[i]=t->q[i+1];
    }
    t->r--;
    printf("Deleted element is %d",max1);
    return;
}
void queuefront(queue *t)
{
    int z;
    if(isempty(t)==1)
    {
        printf("\nQUEUE UNDERFLOW");
        return;
    }
    z  = t->q[t->f];
    printf("QUEUEFRONT is %d",z);
    return;
}
void display(queue *t)
{
    int i;
    if(isempty(t)==1)
    {
        printf("\nQUEUE UNDERFLOW");
        return;
    }
    printf("\nELEMENT OF QUEUE ARE SHOWN BELOW\n");
    for(i=t->f;i<=t->r;i++)
    {
        printf("%d\t",t->q[i]);
    }
    return ;
}
int  main()
{
    int ch,ele;
    queue x;
    x.f = 0;
    x.r = -1;
    printf("IMPLEMENTATION OF PRIORITY QUEUE ");
    while(1)
    {
        printf("\nENTER CHOICE \n1.INSERT 2.DELETE 3.QUEUEFRONT 4.DISPLAY 5.EXIT\n");
        scanf_s("%d",&ch);
        if(ch==5)
        {
            break;
        }
        switch(ch)
        {
        case 1:printf("\nEnter element to insert\n");
            scanf_s("%d",&ele);
            insert(&x,ele);
            break;
        case 2:delete1(&x);
            break;
        case 3:queuefront(&x);
            break;
        case 4:display(&x);
            break;
        default:printf("\nINVALID INPUT");
        }
    }
    _getch();
    return 0;
}