circular queue using linked list

#include<stdio.h>
#include<conio.h>
#include<malloc.h>
#include<stdlib.h>

#define SIZE 5

int Q[SIZE],front=-1,rear=-1;

void insert(int x)
{
if( (front==0 && rear==SIZE-1) || front==rear+1)
{
printf("\nOverflow");
return ;
}
if(rear==-1)
front=rear=0;
else
if(rear==SIZE-1)
rear=0;
else
rear++;
Q[rear]=x;
}

int del()
{
int item;
if(front==-1)
{
printf("\nUnderflow");
return -9999;
}
item=Q[front];
if(front==rear)
front=rear=-1;
else
if(front==SIZE-1)
front=0;
else
front++;
return item;
}

int main()
{
int n,ch;
while(1)
{
printf("\n\t\t\tMenu");
printf("\n\t\t\t1 : Insert");
printf("\n\t\t\t2 : Deletion");
printf("\n\t\t\t3 : Exit");
printf("\n\t\t\tEnter your choice :");
scanf("%d",&ch);
switch(ch)
{
case 1:
printf("\nEnter the item :");
scanf("%d",&n);
insert(n);
break;
case 2:
n=del();
if(n!=-9999)
printf("\nPopped item : %d",n);
break;
case 3:
exit(0);
default:
printf("\nInvalid Choice");
}
}
return 0;
}