Binary tree insert

[nhrnjic6]

I get the algorithm and how binary trees should work but this I don't get :

look at the basic binary tree insert function :

node* insert_in_tree(int number,node* p_tree) {

   if(p_tree == 0) {

    node* newNode = new node;
    node->num = number;
    node->p_left = 0;
    node->p_right = 0;
    return newNode;

    }



if(number < p_tree->num) {

 p_tree->p_left = insert_in_tree(number,p_tree->p_left);

 }

 else { 

    p_tree->p_right = insert_in_tree(number,p_tree->p_right);

 }

  return p_tree;

  so from main : 

  int main()


int main()
{
   node* tree_node = 0;
   cin >> num;
   insert_in_tree(num,tree_node); 

}

I get the first call to the function, tree is equal to 0, it creates a new node and so on, but how does tree changes it value so its not 0 anymore. I just can't see it in code?

[nhrnjic6]

Think I got it, just a Q :

is this how I call it in main :

  while(num != 0) {cin >> num; tree_node = insert(num,tree_node);}