C Program for Circular Queue implementation through Array

//Program for Circular Queue implementation through Array
#include <stdio.h>
#include<conio.h>
#define MAXSIZE 5
int cq[MAXSIZE]={0};
int front,rear;
void main()
{
void add(int);
void del();
void display();
int ch,i,num;
front = -1;
rear = -1;
clrscr();
printf("\nProgram for Circular Queue demonstration through array");
while(1)
{
printf("\n\nMAIN MENU\n1.INSERTION\n2.DELETION\n3.DISPLAY\n4.EXIT");
printf("\n\nENTER YOUR CHOICE : ");
scanf("%d",&ch);
switch(ch)
{
case 1:
printf("\n\nENTER THE QUEUE ELEMENT : ");
scanf("%d",&num);
add(num);
break;
case 2:
del();
break;
case 3:
   display();
    break;
case 4:
    exit(0);
default: printf("\n\nInvalid Choice . ");
}

}
}


void add(int item)
{
if(front ==(rear+1)%MAXSIZE)
{
printf("\n\nCIRCULAR QUEUE IS OVERFLOW");
}
else
{
 if(front==-1)
   front=rear=0;
   else
   rear=(rear+1)%MAXSIZE;
   cq[rear]=item;
   printf("\n\nRear = %d    Front = %d ",rear,front);
}
}


void del()
{
int a;
if(front == -1)
{
printf("\n\nCIRCULAR QUEUE IS UNDERFLOW");
}
else
{
a=cq[front];
 cq[front]=0;
if(front==rear)
front=rear=-1;
else
 front = (front+1)%MAXSIZE;
printf("\n\nDELETED ELEMENT FROM QUEUE IS : %d ",a);
printf("\n\nRear = %d    Front = %d ",rear,front);

}
}

void display()
{
 int i;
 for(i=0;i<MAXSIZE;i++)
   printf("%d\t",cq[i]);
}