UNIX man pages

What might be somewhat more surprising though considering its research origins is that Unix almost since the very beginning had a comprehensive set of online reference documentation for all its commands, system calls, file formats, etc. These are the the manual- or man-pages. On Unix systems used interactively, the man-pages have historically always been installed, space permitting.

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The way the manual pages have evolved and how they are used has changed over the decades. This set of posts is intended to give people unfamiliar with them an overview, as well as offer a review to seasoned users.
↫ Alex Bochannek

Right in this first article in the series there’s an interesting observation I never stopped and thought about: because the original creators of UNIX were writing the content of man pages with the very tools they were creating for UNIX, it led to a virtuous cycle. “Unix tools were used to document Unix, improving the documentation tools themselves as well.” I tend to use the internet now to learn how specific tools and commands work, but having such detailed man pages built right into the operating system was a huge deal pre-internet.