Linked list head double pointer passing

Question

I have seen this in some book/ tutorial.

When you pass in the head pointer (of linked list) into a function, you need to pass it as a double pointer.

For eg:

Answer 1

The reason for having double pointer passing (the first example) is that you want to change the head of the list. Since you are reversing the list, the head should point to the last element of the list after you have done the reversing.

digit* list; 
// initialize list
nReverse(&list); 
// now list is pointing to the last element of the chain (and not the first)

If you don't use double pointers, then list will still point to the original first element which next now points to NULL because its the last element after the reversing. So you loose all your other elements.