ShreddingDragon: I’ve gone through every single log and email I have, and there are barely any codes in them.
Rather late reply, but there a quite a few logs and e-mails that are only available on papers or computers in the environment -- i.e., their contents aren't copied into your e-reader, and you can't pick them up and take them with you physically. There are also at least one or two for which partial codes are spread across multiple logs from different people. I doubt there's a single keypad code where you're meant to just blindly guess the entire thing with no hints, though. It's just the type of game where you're expected to both explore the environment fairly thoroughly, and to take notes outside the game if necessary -- and from an era when those things were considered normal for certain genres.
Also, don't forget that you can take notes on the in-game map. However, there seems to be some limit to this that you'll run into eventually, so don't go
too wild marking every minor point of interest or bit of info you come across, lest you have to go back through the various level maps deleting notes to make room for new ones by the time you're halfway through the game! (I speak from experience here.)
