Documentation

Documentation is a systematically ordered collection of documents and other material that makes a system easier to use, understand, or evaluate. It need not be prose alone. A presentation, a video, a diagram, or a recorded walkthrough can serve the same purpose as a written document.

For a software system, documentation typically spans several audiences and purposes at once: user-facing guides that explain how to operate the system, and internal material such as architecture views, design rationale, and runbooks that record how the system is built and operated. The two kinds serve different readers, but both aim at the same goal, which is to reduce the gap between what a person needs to know and what they currently know.

Documentation ages faster than the system it describes. Keeping it under version control alongside the code it documents, and treating stale documentation as a defect rather than a cosmetic issue, is one of the more reliable ways of keeping the two in sync.