Write code in C for Linear Queue through Array?

#include <stdio.h>
#include<ctype.h>
# define MAXSIZE 200
int queue[MAXSIZE];
int front=-1, rear=-1; //index pointing to the top of stack
void main()
{
void enqueue(int);
int dequeue();
int will=1,i,num,ch;
while(will ==1)
{
printf("MAIN MENU:
1. Enqueue
2.Dequeue
3. Check Queue Full
4. Check Queue Empty ");
Scanf ("%d", &ch);
switch(ch)
{
case 1: printf("Enter the data to add... ");
scanf("%d", &num);
enqueue(num);
break;
case 2: num=dequeue();
if(num==-1)
printf("Queue is empty");\
else
printf("Value returned from pop function is %d ",num);
break;
case 3 : isFull();
break;
case 4 : isEmpty();
break;
default: printf ("Invalid Choice . ");
}
printf("Do you want to do more operations on Stack ( 1 for yes, any other key to exit) "); 
scanf("%d" , &will);
} //end of outer while
} //end of main
void enqueue (int elem)
{
if(isfull())
{
printf("QUEUE FULL");
return;
}
else{
if(front==-1)
front=rear=0;
else
rear++;
queue[rear]=elem;
}
}
int dequeue()
{
int elem;
if(isEmpty())
{
return -1;
}
else
{ 
elem=queue[front];
if (front==rear)
front=rear=-1;
else
front++;
}
return(elem);
}
int isFull()
{
if(rear==MAXSIZE-1)
return 0;
else
return 1;
}
int isEmpty()
{
if((front==-1) && (front==rear))
return 0;
else
return 1;
}