> After all, if I said "try opening a Generations Family Tree .cht file and you'll know what I mean" - would you know what I mean? No, I've never heard about n

> After all, if I said "try opening a Generations Family Tree .cht file and you'll know what I mean" - would you know what I mean? No, I've never heard about neither this program nor its file format. Strangely I can't even find a copy I could download — but there's its manual on archive.org and several sites that could sell me a CD... But even if the program that made the file is lost, you could try reverse engineering the format by collecting as many files as you could find. It's harder, but it's still worth giving a shot. But then again, how popular was that program? > the BBC Domesday Project [1] which paid homage to a 900-year-old book in the form of... a LaserDisc. I read the wiki article and it's wild how it depended on one particular computer and disc reader model. I didn't even know there was a standard for encoding digital data onto LaserDiscs (granted, I've never seen a LaserDisc in person to begin with). But my point is that your examples are all from the early days of widespread computing. You can't just extrapolate it like that. There weren't established standard formats for things back then. Also a lot more software was proprietary AND platform-specific. Today, even if a file format is "unknown", poke at it with a hex editor or the `file` utility and there's a high probability that it's actually something standard like a zip archive or an sqlite database. It's not like we'll ever lose the knowledge of how to read and display a JPEG image from a DVD, unless our entire civilization somehow suffers a collapse so severe we go back to stone age.