A Notes System for Technical Learning

Notes systems tend to fail for one reason: they are harder to maintain than the learning they are meant to support. Good notes are written for a future problem, not for the lecture that produced them. A small system with three kinds of note covers most needs, and it stays light enough to keep using.

Three kinds of note

Concept notes hold one idea each. Write the idea in your own words, add one small example, and say what the idea is used for. Keep the title specific, such as "why a matrix has no inverse when its determinant is zero," rather than a topic name like "matrices." A concept note should be understandable without the source that introduced the idea.

Worked examples record a problem, the steps taken, and the place where progress stopped. Include the mistake if one was made. A worked example shows a method in use, and it is often the note that gets reread most when a similar problem appears.

Open questions are things not yet understood, written as clear questions with a date. They are the most valuable of the three, because they show exactly where understanding ends. Review them regularly, and remove each one when it is answered. An open question might read: why does a learning rate that works on one dataset fail on another? That form is specific enough to answer later and gives the note a reason to exist.

Write for a future problem

Each note should answer a question likely to arise later. Before writing, imagine returning to the note in a month, without the lecture or the textbook, while stuck on something related. A useful note at that point contains the missing context, usually a worked number or a sentence about when the idea applies. Compare two versions of a note on the dot product. One gives only the formula. The other says what the quantity measures, gives two small vectors and states the result. The second is the one that helps in a month.

This test also guides length. A note that tries to cover a whole chapter is hard to use. A note that covers one idea and one example is easy to find and easy to reread. A long note is a signal to split it into two.

Link notes instead of filing them

Links between notes do more than folders can. A concept note can point to the worked examples that use it, and a worked example can point back to the concept it relies on. Over time the links show how ideas depend on one another, which is exactly what is needed when a new topic builds on older ones.

Links need upkeep, so keep their number small. Use a simple naming convention so notes can be found by title, and add tags only where they help with search. Deep folder trees tend to become places where notes are forgotten. A link that no longer makes sense is worth removing, just as a stale note is worth correcting. A flat structure with good titles and a few links usually works better.

Links are only useful if they are added when a note is written. Adding them later from memory is slow, so include a line for related notes in every new entry.

A weekly review

Set aside about thirty minutes each week. Read through the open questions and try to resolve one. If a worked example has proved useful more than once, turn the underlying idea into a concept note. Look for notes that are now wrong or incomplete, and correct them rather than leaving them as they are.

The review is what turns notes into knowledge. Without it, notes become a record of what was once read. With it, they become a working reference that can be trusted, because it was checked recently. Duplicates deserve attention too. Two notes that cover the same idea in slightly different words are harder to trust than one, so merge them and keep the clearer title.

Keep notes short enough to reread

A note that fits on one screen gets reread. A note that needs scrolling and searching often does not. When a formula appears, write a sentence after it that explains each symbol. A formula without its symbols explained will be hard to use in a month, even if it was understood when written.

Avoid copying large passages from a source. Paraphrase the idea, and record the source in one line. Copied text feels like learning but rarely produces the explanation needed later. A status word at the top of each concept note, such as draft or checked, tells a future reader how far to trust it. The act of rewriting is part of the work.

Try the system for two weeks

After the next study session, write one concept note, one worked example and one open question. Give the notes titles that describe their content, and link the concept note to the example. Place the open question on the list to review at the end of the week.

A week later, read the concept note without the worked example and try to apply the idea to a new case. If that works, the note is doing its job. If it does not, the note is missing context or an example. Revise it, then decide whether the system is light enough to keep. The aim is not a perfect structure. It is a set of notes worth finding when stuck.