Menu Driven program for implementing all stack using linked list

#include<stdio.h>
#include<stdlib.h>
void push();
void pop();
void display();
struct node
{
	int val;
	struct node *next;
};
struct node *head;

int main()
{
	int choice = 0;
	printf("\n*********Stack Operation Usinf Linked List*********\n");
	printf("\n-----------------------------------------\n");
	while(choice != 4)
	{
		printf("\n\n Choose one from the below options...\n");
		printf("\n1.Push\n2.Pop\n3.Show\n4.Exit");
		printf("\n Enter your choice \n");
		scanf("%d",&choice);
		
		switch(choice)
		{
			case 1:
			{
				push();
				break;
			}
			case 2:
			{
				pop();
				break;
			}
			case 3:
			{
				display();
				break;
			}
			case 4:
			{
				printf("Exiting...");
				break;
			}
			default:
			{
				printf("Please enter valid choice: ");
			}
		};
	}
}

void push()
{
	int val;
	struct node *ptr = (struct node*)malloc(sizeof(struct node));
	if(ptr == NULL)
	{
		printf("Not Able to push the element");
	}
	else
	{
		printf("Enter the value: ");
		scanf("%d",&val);
		if(head == NULL)
		{
			ptr->val = val;
			ptr->next = head;
			head = ptr;
		}
		printf("Item Pushed!!");
	}
}

void pop()
{
	int item;
	struct node *ptr;
	if(head == NULL)
	{
		printf("Underflow");
	}
	else
	{
		item = head->val;
		ptr = head;
		head = head->next;
		free(ptr);
		printf("Item Popped!!");
	}
}

void display()
{
	int i;
	struct node *ptr;
	ptr = head;
	if(ptr == NULL)
	{
		printf("Stack is empty..\n");
	}
	else
	{
		printf("Printing stack elements\n");
		while(ptr != NULL)
		{
			printf("%d\n",ptr->val);
			ptr = ptr->next;
		}
	}
}