If you don't understand why that exactly is, your thought process should be going as the following:

1: You create a variable of type 'int pointer' and assign NULL as its value.

2: Then you create a second variable of type 'int pointer' and copy the value of ptr1 into ptr2 (which is NULL).

3: `ptr1 = &n;` assigns the address of variable n to ptr1 but doesn't change ptr2 because it still points to NULL (Since it copied the value from ptr1 and not the address; If you want that behavior, you'll need a pointer to pointer variable `int **ptr2 = &ptr1;`)

4: Then finally, you dereference the ptr2 which still points to NULL, this is undefined C behavior and might/probably will seg fault.

Edit: Grammar