[support] Clarification about hook_schema(), hook_update() and hook_install() in D6

Hello! I need some clarification on D6 behavior with hook_install(), hook_update() and hook_schema(). This is my question within a simple use case: When I write a module, I implement hook_schema(). I then do a hook_install() which call drupal_install_schema() function. Then ok, it works. BUT, then I have to add a single field to my database. So, I write a hook_update_N() and use drupal_add_field(). Ok, this works. The question is: do I have to modify my hook_schema so it carries the new field or not ? When a new user will install the module, does drupal just assume that the schema is up to date then it does not need to do the updates ? Simple question. It was this behavior with D5, but I'm not sure with D6. Thanks.