In this section I will walk you through all of the core concepts in detail.

I strongly recommend that you read the core concepts section end-to-end, in the order shown below, at least once. This will give you a solid grasp of the system; you may then choose to use individual sections like a reference manual.

As you read it, you’ll have questions. Hold your horses and keep reading – I believe I have addressed most of them, but because this is a linear thing it might take me a few pages to get there.

The basic idea of Johnny.Decimal is very simple, but its power comes when you truly understand it. Reading this should give you that understanding; if you still have questions, or if I have not made something clear, please get in touch and I will help you.


You should be familiar with this section before you attempt to start your own Johnny.Decimal system.

Areas & categories group similar things together, and appear before the decimal.
Within each category, each item has a unique ID. It comes after the decimal.
How to use Johnny.Decimal to organise your file system.
Using the J.D system to keep simple text notes.
How (and why) to track the numbers within your system.
Ready to start? Here’s how you develop your own J.D system.


You do not need to know everything in this section initially, but you will find it useful as you become more familiar with the system.

How to expand the system beyond the single project described so far.
Using the system to effectively manage your inbox.
Why I reserve 00-09 for ‘Management & Meta’, and what this means.
Using J.D to move around the command line.
Because rules are meant to be broken, right?

Other notes

How I refer to the system in the abstract.