Ask HN: Oldest code you have written that is still in use?

The code I wrote that will be running the longest is code I've contribute to Emacs. User-facing features are unlikely to be removed anytime soon.

The oldest is the internal system for a record label written in 1997 and I still occasionally get emails asking how such and such works (and I have little idea, it was in PERL).

Through to code that processes video and audio snippets for most of the UK Football League premium content sites. Authored in 2000 (mostly VBScripts that slice, encode, and distribute media files and the metadata).

Parts of btinternet.com still appear to use my horrible CMS... written in 1999... though gladly it's now very few parts and I suspect these are just cached outputs rather than the CMS still being in production.

Most worryingly would be the UK Home Office, and most UK banks and some heavy manufacturing companies that I wrote project management reporting software for over a decade ago, and as they manage 20 year projects I believe that stuff has at least another decade in production. At least all of these systems are not internet connected (then again, they'll never be updated either).

My code isn't terrible clever or pretty, those requirements got dropped a long time ago. But I have learned to make code that is simple to read, easy to maintain and tweak, and that can sprintf debug with the best of them (debug tools of choice have come and gone in the time my code has been live).

Nobody uses it now apart from me, but I still maintain it.