Creation of stack using Linked list

Stack_Linkedlist.c

#include <stdio.h>
#include <stdlib.h>
struct node{
char k;
struct node *addr;
};
struct node *start,*ptr,*nn,*top;
int main(){
struct node *ms;
int y;
char x;
printf("\nEnter how many nodes you want : ");
scanf("%d", &y);
printf("\n\nEnter the data  : \n");
for(;y!=0;y--)
{
    scanf(" %c",&x);
    nn=(struct node *) malloc(sizeof(struct node));
    if (nn==NULL)
    {
        printf("No Space left");
    }
    else
        {
        if (start==NULL)
            {
        start=nn;
        nn->k=x;
        nn->addr=NULL;

            }
            else
                {
                ptr=start;
            while(ptr->addr!=NULL)
            {
                ptr=ptr->addr;
            }
            ptr->addr=nn;
            nn->k=x;
            nn->addr=NULL;



                }

        }

}
ptr=start;
printf("\nLinked list : \n");
while(ptr!=0)
{
    printf("%c\n",ptr->k);
    ptr=ptr->addr;
}
top=start;
int m;
printf("\n\nSelect 1 for Peek \nSelect 2 for Push\nSelect 3 for pop\n\n-----------------------\n :");
scanf("%d",&m);
switch(m)
{
case 1:
        printf("\nPeek Value of the Stack is %c\n\n",top->k);
        break;
case 2:
    nn=(struct node *) malloc(sizeof(struct node));
    printf("Enter the data : ");
    char ll;
    scanf(" %c",&ll);
    nn->k=ll;
    nn->addr=top;
    start=nn;
    ptr=start;
printf("\nNew Linked list : \n");
while(ptr!=0)
{
    printf("%c\n",ptr->k);
    ptr=ptr->addr;
}
break;
case 3 :
    ptr=start;
    start=ptr->addr;
    free(ptr);
    top=start;
       ptr=start;
printf("\nNew Linked list : \n");
while(ptr!=0)
{
    printf("%c\n",ptr->k);
    ptr=ptr->addr;
}
break;
}
}