Stack

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

#define CAPACITY 100
struct node
{
    int data;
    struct node *next;
} *top;

int size = 0;

int main()
{

    int choice,data,n;
    while(1)
    {
        printf("\n\n\t<<<<<<<WELCOME TO STACK PROGRAM>>>>>>>\n\n");
        printf("\t1. Push\n");
        printf("\t2. Pop\n");
        printf("\t3. Size\n");
        printf("\t4. TOP\n");
        printf("\n\tEnter Your Choice: ");

        scanf("%d", &choice);

        switch(choice)
        {
        case 1:
            printf("\tEnter data to push into stack: ");
            scanf("%d", &data);
            push(data);
            break;

        case 2:
            data = pop();

        if (data !=n )
                printf("\tData : %d\n", data);
            break;

        case 3:
            printf("\tStack size: %d\n", size);
            break;

        case 4:
            printf("\tTop is :%d\n",pop());
            break;

        default:
            printf("\tInvalid choice, please try again.\n");
        }

        printf("\n\n");
    }



}


void push(int element)

    {


    if (size >= CAPACITY)
    {
        printf("\tStack Overflow\n");
        return;
    }


    struct node *N = (struct node *) malloc(sizeof(struct node));


    N->data = element;

    N->next = top;


    top = N;

    ++size;

    printf("\tData is pushed into stack.\n");
}



int pop()
{
    int data = 0,n;
    struct node * N;

    if (size <= 0 || !top)
    {
        printf("\tStack is empty.\n");

        return n;
    }


    N = top;
    data = top->data;


    top = top->next;


    free(N);

   size--;

    return data;
}