# Standard zero 'AC.00 JDex for …' – what's it for?

> Clarifying a common confusion: what are these 'standard zero' entries for?

There's a reason [the standard zeros](/documentation/the-standard-zeros) live in the site's `12 Advanced` section. Including them all in our [standard](/las/) [systems](/sbs/) was a difficult decision.[^included]

[^included]: In the end, we included them. It's easier to delete what you don't want than it is to create what you do.

Let's look at one of these specifically, the `AC.00 JDex for …` entry.

## 00.00 JDex for the system

This one is the clearest. As the 'first' ID in any system, `00.00` serves as its introductory document.

If there's anything that you need to know _about the system_, it should go here. I think of it like, if I got amnesia, what's the _one thing_ I'd need to know? It's the location of this note. From here, you should be able to find everything else.

Here's what I've written at `00.00` in my personal system:

## 00.00 JDex for P76 Johnny's personal system

- JDex for this system is right here in Bear. You're reading it.
- Filesystem for this system is primarily at `iCloud Drive/Documents/P76 Johnny's personal system`.
  - When folders live elsewhere, that location is specifically noted in the JDex entry.

---

### Area-level entry

Let's go down to the area level, `10.00`, `20.00` and so on. In exactly the same way, the JDex entries for the area serve as the documentation for that area.

What's in it? Why did you decide to put these things in it? What isn't in it?

I just did a bit of a tidy-up and I created myself a new area. (I use the [Life Admin](/las/) system but it's specifically not designed to handle all the _other_ stuff we do: our hobbies and jobs and whatnot.)

I don't have a single hobby because I'm the sort of person who creates a bunch of stupid little 'projects'. These have accumulated over the years and I have an archive I'd like to save. And I'll need IDs for new projects from now on.

I also need a place to store stuff that I've downloaded. So I created a new area, `20-29 Create & collect`.

An area is little more than the categories it contains, so the JDex entry `20.00` is very simple. I've just told myself:

_This area is for all the crazy ideas. See the category JDex for more details._

– and then linked to `21.00`, `22.00`, and `29.00`.

### Category-level entry

Here are my categories:

- 21 🧠 Imaginarium[^imaginarium]
- 22 😍 Humans are brilliant
- 29 🏛️ The Omnium[^omnium]

[^imaginarium]: A name gratefully borrowed from Lucy, who came up with it [when she built her own system](/jdu/workshop).

[^omnium]: Yes, I pushed this out to `29`, further reinforcing its archive-ness.

And here are their JDex entries:

#### 21.00 JDex for Imaginarium

This is a place for all the crazy projects. But _not_ for learning about, and documenting, technology and code. That's more useful in a work context, and is going to be _way_ more useful for linking in Obsidian, so code learning and notes are at D25.[^d25]

[^d25]: `D25` is my [Small Business System](/sbs/) and it lives in Obsidian.

#### 22.00 JDex for Humans are brilliant

A place for 'collected works' but only things that are made _by other humans_.

#### 29.00 JDex for The Omnium

This is a place for _your_ historical collected works. You shouldn't be working in here day-to-day. Things here shouldn't ever change.

- And don't move completed things from **21.00 JDex for Imaginarium** here. They just stay there and age out per the Johnny.Decimal system design.
- Only add entries here if, in the process of tidying up old hard drives/folders, you find more old things.

### Summary

So in summary, these JDex notes are your documentation of your own system's structure and purpose, at each level.

- `00.00` is your description of _the entire system_.
- `A0.00` is your description of _this area_.
- `AC.00` is your description of _this category_.

And if you don't need them, or that's confusing, you can just ignore or delete them.