Recovering the Lost Apollo 10 LM Software [video]
youtube.comSummary: they found a document with checksums for each of the 36 banks of the missing software. This let them know that two banks had changed. Working from an earlier and later source listing versions, they had to recreate only some of the changes. Luckily, they found memos describing the changes - mostly in a newer gravity model. All that was left was to put the code in the proper places, and some obvious guesses (e.g. new constants at the end of existing constants) -- and it worked!
A fun watch.
We aren't printing out our source code any more. Which means that such recovery methods won't work in the future. Has archival of such historic stuff improved since?
There's some projects. Like arctic archival of github repos: https://archiveprogram.github.com/
Granted, this is only a snapshot, and preservation is a big problem. And you can't easily preserve gigabytes of data in dead tree format...
Generally the best approach is "Lots of Copies Keep Stuff Safe" but moves to streaming media and game rental services worry me.
There also needs to be a recognition that what we see is often a very small fraction of what existed... most things won't survive, unless successive generations of people continuously care sufficiently about them. Or they're ubiquitous that we'll find at least one...
Lots of copies on flash chips are all going to be gone in 100 years.
I don't trust flash chips at all.
My older media is all pretty much unreadable for one reason or another. My solution is to buy new drives every year and copy everything forward. Fortunately, the capacity keeps rising so that works out rather well.
In many cases it will prove difficult to even be able to build or run software that hasn't been touched in 10+ years. Preserving the computational environment is a whole another concern for future software archeology.
Related (not historic stuffs necessarily): https://www.softwareheritage.org/
I think that archive.org is doing great work in that area as an entity and as an umbrella to other people like Al Kossow at bitsavers.org.
I think this is the GitHub repo with the code shown in the video. Very impressive!
That LEM simulator they used at the end was fascinating. Is there a video that does a deep dive of that.
Mike Stewart seems like the most charming technical guy I've ever seen.
Incredible.