Stack

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

struct node
{
    int data;
    struct node * link;
};
struct node * top=NULL;

void push(int item)
{
    struct node * temp=(struct node *)malloc(sizeof(struct node));
    if(temp==NULL)
    {
        printf("\n STACK is OVERFLOW");
    }
    else
    {
        temp->data=item;
        temp->link=top;
        top=temp;
    }
}
void pop()
{
    struct node * temp;
    if(top==NULL)
        printf("\nSTACK is UNDERFLOW");
    else
    {
        temp=top;
        printf("\n%d is deleted.", temp->data);
        top=temp->link;
        temp->link=NULL;
        free(temp);
    }
}
void traverse()
{
    struct node * temp=top;
    if(top==NULL)
        printf("stack is underflow and nothing to flow");
    else
    {
    while(temp!=NULL)
    {
        printf("%d-> ",temp->data);
        temp=temp->link;
    }
    }
}
int main()
{
    int k,item;
    while(1)
    {
        printf("\nSTACK OPERATION");
        printf("\n1.PUSH\n2.POP\n3.TRAVERSE\n4.EXIT");
        printf("\nEnter your choice: ");
        scanf("%d",&k);
        switch(k)
        {
            case 1: printf("\n Enter an element to be inserted");
                    scanf("%d",&item);
                    push(item);
            break;
            case 2: pop();
            break;
            case 3: traverse();
            break;
            case 4: exit(1);
            break;
            default: printf("\n Wrong choice entered");
            break;
        }
    }
}