C program to implement a linked queue

#include <stdio.h>
#include <conio.h>
#include <malloc.h>
struct node
{
int data;
struct node *next;
};
struct queue
{
struct node *front;
struct node *rear;
};
struct queue *q;
void create_queue(struct queue *);
struct queue *insert(struct queue *,int);
struct queue *delete_element(struct queue *);
struct queue *display(struct queue *);
int peek(struct queue *);
int main()
{
int val, option;
create_queue(q);
clrscr();
do
{
 printf("\n *****MAIN MENU*****");
 printf("\n 1. INSERT");
 printf("\n 2. DELETE");
printf("\n 3. PEEK");
 printf("\n 4. DISPLAY");
 printf("\n 5. EXIT");
 printf("\n Enter your option : ");
 scanf("%d", &option);
switch(option)
 {
 case 1:
 printf("\n Enter the number to insert in the queue:");
 scanf("%d", &val);
 q = insert(q,val);
 break;
 case 2:
 q = delete_element(q);
 break;
 case 3:
 val = peek(q);
 if(val! = –1)
 printf("\n The value at front of queue is : %d", val);
 break;
 case 4:
 q = display(q);
 break;
 }
}while(option != 5);
getch();
return 0;
}
void create_queue(struct queue *q)
{
q -> rear = NULL;
q -> front = NULL;
}
struct queue *insert(struct queue *q,int val)
{
struct node *ptr;
ptr = (struct node*)malloc(sizeof(struct node));
ptr -> data = val;
if(q -> front == NULL)
{
 q -> front = ptr;
 q -> rear = ptr;
 q -> front -> next = q -> rear -> next = NULL;
}
else
{
 q -> rear -> next = ptr;
 q -> rear = ptr;
 q -> rear -> next = NULL;
}
return q;
}
struct queue *display(struct queue *q)
{
struct node *ptr;
ptr = q -> front;
if(ptr == NULL)
 printf("\n QUEUE IS EMPTY");
else
{
 printf("\n");

while(ptr!=q -> rear)
 {
 printf("%d\t", ptr -> data);
 ptr = ptr -> next;
 }
 printf("%d\t", ptr -> data);
}
return q;
}
struct queue *delete_element(struct queue *q)
{
struct node *ptr;
ptr = q -> front;
if(q -> front == NULL)
 printf("\n UNDERFLOW");
else
{
 q -> front = q -> front -> next;
 printf("\n The value being deleted is : %d", ptr -> data);
 free(ptr);
}
return q;
}
int peek(struct queue *q)
{
if(q->front==NULL)
{
 printf("\n QUEUE IS EMPTY");
 return –1;
}
else
 return q->front->data;
}