Stack Implementation

gistfile1.c

#include<stdio.h>
#include<conio.h>
#include<malloc.h>
struct node
{
      int data;
     struct node *link;
}   NODE;

void push(int);
int pop();
void display();
struct node  *top= NULL;     // to point the top element of stack

void main()
{
	int opn,elem;
	printf("LINKED lIST IMPLEMENTATION OF STACK OPERATIONS");
	printf("\n1.push\n2.pope\n3.Display\n4.exit\n");
	do
	{
	     printf("\nenter your option");                         // option for pushing,popping,displaying or exit
	     scanf("%d",&opn);
	switch(opn)
	       {
		case 1:                                                                              
		printf("\nenter the element to be  pushed");
		scanf("%d",&elem);
		push(elem);
		break;

		case 2:
		elem=pop();
		if(elem!=-1)		// if -1 then stack empty
		printf("poped node node from front is %d",elem);
		break;

		case 3:
		printf("\nelements in stack for ll implementation are ");
		display();
		break;
		
		case 4: exit();
	     }
             }while(opn!=4);
}

void push(int info)
{
	struct node *temp;
	temp=(struct node *)malloc(sizeof(struct node));     //  assinging memory to the node
	if(temp==NULL)
	printf("out of memory");
	    else
	{
	temp->data=info;
	temp->link=top;
	top=temp;
	printf("\nNode pushed at end");
	}
}

int pop()
{
	int info;
	struct node *t;
	if(top==NULL)
	{
	printf("underflow");
	return -1;
	}

	else
	{
	t=top;
	info=top->data;          // to store the data in the node to be poped
	top=top->link;
	t->link=NULL;
	free(t);
	return(info);
	}
}

void display()
{
struct node *t;
if(top==NULL)
printf("stack empty");
else
          {
	t=top;
	printf(" TOP->");
	
	while(t)
	{
	printf("%d  : ",t->data);
	t=t->link;
	}
         }
}