WAP of LINKED lIST insert front , print , delet front in single linked list

/*WAP of LINKED lIST insert front , print , delet front in single linked list*/

#include<stdio.h>
#include<conio.h>

void insert_front_sl();
void print_sl();
void insert_end_sl();

struct node
{
	int data;
	struct node *link;
};
struct node *header;

void main()
{
	clrscr();
	
	header = (struct node *) malloc(sizeof(struct node));
	header->data = NULL;
	header->link = NULL;
	
	insert_front_sl();
	insert_front_sl();
	print_sl();
	insert_end_sl();
	insert_end_sl();
	print_sl();
	
	getch();
}

void insert_front_sl()
{
	struct node *temp,*ptr;
	int X;
	temp = (struct node *) malloc(sizeof(struct node));
	
	if(temp == NULL)
	{
		printf("Memory Insufficient");
	}
	else
	{
		ptr = header->link;
		
		printf("\nEnter the value to insert at front: ");
		scanf("%d", &X);
		temp->data = X;
		temp->link = ptr;
		header->link = temp;
	}
}

void print_sl()
{
	struct node *ptr;
	ptr = header;
	
	while(ptr->link != NULL)
	{
		ptr = ptr->link;
		printf("%d ",ptr->data);
	}
}

void insert_end_sl()
{
	struct node *temp,*ptr;
	int X;
	temp = (struct node *) malloc(sizeof(struct node));
	
	if(temp == NULL)
	{
		printf("Memory Insufficient");
	}
	else
	{
		ptr = header;
		while(ptr->link != NULL)
		{
			ptr = ptr->link;
		}
		
		printf("\nEnter the value to insert at end: ");
		scanf("%d", &X);
		temp->data = X;
		temp->link = NULL;
		ptr->link = temp;
	}
}