I recently unearthed something that I thought was 20 years old when someone asked me about it. I checked and it was only 14 years old based on mtime (thought I suspect I started the project nearly 20 years ago). Another project I unearthed for a different reason was only 13 years old by mtime (again, it was started before that). I must concede that I haven't actually recently compiled and used anything that was untouched for 20 years.
I should note that the first program I wrote that was actually used for a purpose (it calculates energy based on an internal stopwatch and then typing in values from a volt and ammeter, for a science project in 1992) still works in qb64 today.
The second program I wrote that was actually used for a purpose assumes a parallel-port printer on DOS that uses a fairly old version of PCL, and was written in 16-bit C, so probably won't work today.
