Circular Queue using Structure

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

#define max 5

typedef struct Queue
{
int val[max];
int rear,front;
}qu;

void enque(qu *,int);
int deque(qu*);
int peek(qu);
int isempty(qu);
int isfull(qu);
void disp(qu);


void main()
{
qu q;
int g,v;
q.rear=q.front=-1;
while(1)
{
printf("\n1) Insert\n2) Delete\n3) Peek\n4) Display\n5) Exit");
printf("\n Enter your choice :");
scanf("%d",&g);
switch(g)
{
case 1: printf("\n Enter the value");
scanf("%d",&v);
if(!isfull(q))
enque(&q,v);
else
printf("\nNo more space");
break;
case 2: if(!isempty(q))
printf("\nDeleted element is %d",deque(&q));
else
printf("\nNothing to delete");
break;
case 3:
if(!isempty(q))
printf("\n value at front %d",peek(q));
else
printf("\n Nothing in the front");
break;
case 4: if(!isempty(q))
{
printf("\nValues int queue : ");
disp(q);
}
else
printf("\nNothing to display");
break;
case 5: exit(0);
default: printf("\n wrong choice");
}
}
}


void enque(qu *q,int p)
{
if(q->rear==-1)
q->rear=q->front=0;
else if(q->rear==max-1)
q->rear=0;
else
q->rear++;
q->val[q->rear]=p;
}

int deque(qu *q)
{
int g;
g=q->val[q->front];
if(q->front==q->rear)
q->rear=q->front=-1;
else if(q->front==max-1)
q->front=0;
else
q->front++;
return g;
}


int peek(qu q)
{
return q.val[q.front];
}

int isempty(qu q)
{
if((q.front==-1 && q.rear==-1))
return 1;
else
return 0;
}

int isfull(qu q)
{
if((q.front==0 && q.rear==max-1) || q.front==q.rear+1)
return 1;
else
return 0;
}

void disp(qu q)
{
int i;
if(q.front>q.rear)
{
for(i=q.front;i<=max-1;i++)
printf("%d,",q.val[i]);

for(i=0;i<=q.rear;i++)
printf("%d,",q.val[i]);
}
else
for(i=q.front;i<=q.rear;i++)
printf("%d,",q.val[i]);
}

I/O: