@clew @Mumonkan @blogdiva With no modification, no emulator, etc... I came up with some LaTeX configuration code ~18 years ago that I still use as a default for some projects, and it's been handed off to other people since.

I have plain TeX that's years older than that, and it *would* produce a document without modification, but neither I nor anyone else has had a reason to touch it.

Among other things, I wrote my assignments for my poetry-workshop elective in TeX. There is no need to revisit poetry from college.

@clew @bstacey @blogdiva @tinmouth

extra credit points. the script i mention is for a project that has been running even longer. probably around 2000(?) i wrote a script to visualize activity on the project. it creates this chart every week.

so this chart has been cranked out for 25+ years. 😅 (apologies for the aspect ratio, but time is 1 dimensional, what can i say? haha)

@clew @blogdiva some "trippy graphics" programs dated from 1993, I had put the .EXE files (34K, that was a good binary size) on my CMU page, just ran them in DOS emulation.

A bit more accessibly, 1997 perl5 to render PostScript from the .puz crossword format.
https://www.cs.cmu.edu/~eli/warez/puz2ps

Other people running... pretty sure nothing.

@clew

Oldest program that can still run: A natural language understanding system that maps English sentences to an integrated semantic graph, which can then answer questions about what it's been told, connecting the dots between different pieces of information. It's about 20 years old now.

Oldest program that other people still run: An implementation of the XCS algorithm, which uses genetic algorithms and reinforcement learning to find the minimal set of rules that map from inputs to outputs reliably in the data set. It's a little over a decade old now. Unlike the NLU system, this one is open source:

https://github.com/hosford42/xcs

@bstacey @Mumonkan @blogdiva

@clew @bstacey @Mumonkan @blogdiva

I have some ultra-crudgy C programs I wrote in 1998 or 1999 to do some astronomy calculations. Somehow they managed to survive multiple disk moves without me noticing them until recently.

My personal web site has some PHP code (so, sort of “run by other people”) with origins in the early-mid-00s, though most of that has been at least partially rewritten at least once.