Global extinction level event, all our culture lost, but we want to keep a record of what we were doing. A library of Alexandria built in this age would contain much computer code. How to archive it in a format that's likely to be understood by future civilizations ?
An idea is a tool is an idea. Or an idea is a description of a tool. In any case, code is a history of our time. A computed history. It encodes the way we thought about things, reflected in the way we arranged our systems of doing things. There's an argument to be made that it is a highly efficient description -- it might be possible to accurately rebuild a fallen civilization if we could read its computer code. At the very least, we'd have a start on rebuilding its infrastructure. The writings of a time encode its culture, you can rebuild a culture from that. The Renaissance did this with the culture of ancient Greece and Rome. Code is a medium, of today. It works to save that, if we value the preservation of our time.
Considering all the bits and pieces of plastic we have manufactured will be around on this planet until well after we are gone I would take a guess at saying plastic film would be best.
