Stack Operations.c

#include <stdio.h>
#include <stdlib.h>
struct node
{
    int info;
    struct node *ptr;
}*top,*top1,*temp;

int topelement();
void push(int data);
void pop();
void display();
void create();

int count = 0;

void main()
{
    int no, ch, e;

    printf("\n----MENU----");
	printf("\n1.Push");
    printf("\n2.Pop");
	printf("\n3.Dipslay");
    printf("\n4.Exit");
    create();

    while (1)
    {
        printf("\nEnter option: ");
        scanf("%d",&ch);

        switch (ch)
        {
        case 1:
            printf("Enter item : ");
            scanf("%d", &no);
            push(no);
            break;
        case 2:
            pop();
            break;
        case 3:
            display();
            break;
        case 4:
            exit(0);
        default :
            printf("Invalid input!");
            break;
        }
    }
}
void create()
{
    top = NULL;
}
void push(int data)
{
    if (top == NULL)
    {
        top =(struct node *)malloc(1*sizeof(struct node));
        top->ptr = NULL;
        top->info = data;
    }
    else
    {
        temp =(struct node *)malloc(1*sizeof(struct node));
        temp->ptr = top;
        temp->info = data;
        top = temp;
    }
    count++;
}
void display()
{
    top1 = top;

    if (top1 == NULL)
    {
        printf("Stack is empty");
        return;
    }

    while (top1 != NULL)
    {
        printf("%d ", top1->info);
        top1 = top1->ptr;
    }
 }
void pop()
{
    top1 = top;

    if (top1 == NULL)
    {
        printf("\nSTACK UNDERFLOW");
        return;
    }
    else
        top1 = top1->ptr;
    printf("\nPopped value: %d", top->info);
    free(top);
    top = top1;
    count--;
}
int topelement()
{
    return(top->info);
}