All Notes on BCA

#include<stdio.h>
#include<conio.h>
#include<malloc.h>
struct stack
{
 int data;
 struct stack *next;
};struct stack *nw, *temp, *top;

void push()
{
 int item;
 clrscr();
  printf("Enter Element : ");
  scanf("%d",&item);
   if(top->data == NULL)
     top->data = item;
    else
     {
      nw = (struct stack *)malloc(sizeof(struct stack));
      nw -> data = item;
      nw -> next = top;
      top = nw;
     }
}

void pop()
{
 clrscr();
 if(top->data == NULL)
   printf("\nSTACK UNDERFLOW ! ! !");
  else
   {
    temp = top;
    top = top -> next;
     printf("%d is element deleted . . .",temp->data);
     free(temp);
   }
 }

void display()
{
  if(top->data == NULL)
    printf("STACK UNDERFLOW . . .");
   else
    {
     temp = top;
      while(temp != NULL)
       {
 printf("Your Stack Element : %d\n",temp->data);
 temp = temp->next;
 }
     }
 }

void main()
{
int ch;
 nw = (struct stack *)malloc(sizeof(struct stack));
 nw -> data = NULL;
 nw -> next = NULL;
 top = nw;
do
 {
clrscr();
 printf("1. Push Operation\n2. Pop Operation\n3. Display\n4. Exit\nEnter Any number : ");
 scanf("%d",&ch);
  switch(ch)
   {
    case 1:
      push();
     break;
    case 2:
      pop();
      getch();
     break;
    case 3:
      clrscr();
      display();
      getch();
     break;
    }
  }while(ch != 4);
 }

OUTPUT1. Push Operation
2. Pop Operation
3. Display
4. Exit
Enter Your Choice : 1
Enter any Number : 10
1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 1
Enter any Number : 20

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 1
Enter any Number : 30

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 1
Enter any Number : 40

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 1
Enter any Number : 50

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 3
Stack Element -
50
40
30
20
10

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 2
Deletion Element is = 50

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 2
Deletion Element is = 40

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 2
Deletion Element is = 30
1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 2
Deletion Element is = 20
1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 2
Deletion Element is = 10

1. Push Operation
2. Pop Operation
3. Display
4. Exit

Enter Your Choice : 2
STACK UNDERFLOW !!!!!!!!!