A 'bit' in information theory is just a unit of measurement, corresponding to the information conveyed by one yes-or-no question (where both answers were previo

A 'bit' in information theory is just a unit of measurement, corresponding to the information conveyed by one yes-or-no question (where both answers were previously equally likely). Since it's a fairly natural unit, your alien archaeologist might even use it. However, if they had a weird taboo against binary, they could define a similar concept in other ways. In fact, we humans have too. Bletchley Park used "bans" or hartleys, which is the information carried by a single base-10 digit (without any a priori information). Nats use a base-e representation instead, which ties into statistical physics nicely. There's nothing stopping you from inventing a weird informational unit where 1 corresponds to "the answer to a seven way question were two of the answers are each twice as likely as the rest." So, suppose your alien digs up my thumbdrive. It examines it carefully and notices that each MOSFET is always in one of two states. That suffice to describe its information-carrying capacity in whatever system they use: bits, hartleys, nats, zorblaxen. A similar analysis of their own media would let them say "This thing is so sophisticated, it can hold the work of 10,000 scribes" or "This junk can barely contain a moment of our 16D videos." If your drive were packed with different types of media, they might even discover that some parts of the disk (e.g., ascii text) DON'T use all of the available capacity. None of this, of course, tells them what the data means. For that, you'd need to relate these data to some external source.