Insert Display Delete from Queue

/*************************************************************
This Program implements Queue
Insert Number into Queue and Displays Numbers(in FIFO order)
Deletes Number from rear
*************************************************************/

#include "stdio.h"

#define max 10

int front=0;
int rear=0;
int p[max];
int q;

void insert(){
if(front==max){
printf("\nQueue Full");
}
else
{
printf("\nEnter a Number: ");
scanf("%d",&q);
p[front]=q;
front++;
}
}

void display(){
rear=0;
while(rear
printf("%d",p[rear]);
printf("\t");
rear++;
}
}

void delete(){
if(front==0){
printf("\nNothing to delete");
return;
}
else
{
p[front-1]='\0';
front--;
printf("\nOne element of Queue deleted");
}
}

int main(){
int i;
do{
printf("\nEnter ur Choice:");
printf("\n1. Insert into Queue");
printf("\n2. Diplay Queue");
printf("\n3. Delete from Queue");
printf("\n4. Exit. ");
scanf("%d",&i);
switch(i){
case 1:
insert();
break;
case 2:
printf("\nData in Queue: ");
display();
break;
case 3:
delete();
break;
case 4:
break;
default:
printf("\nInvalid Choice,Re-Enter Choice");
break;
}
}while(i != 4);
return 0;
}