Historically pure machine code with jumps etc lacked any from of encapsulation as any data can be accessed and updated by anything.

However, you would still use abstractions. If you pretend the train is actually going 80.2 MPH instead of somewhere between 80.1573 MPH to 80.2485 MPH which you got from different sensors you don’t need to do every calculation that follows twice.

The code always ends up nice and clean and modular. And, since I'm working towards the idea, I can say "here are the modular pieces I have to work with, dictated the fundamentals beneath, how do I use them to accomplish the task?". When working from the idea, I think it's easier to want to write something to achieve the immediate task, in a "not see the forest for the trees" kind of way (abstractions are about the goal, rather than the reality under). Of course, both directions are required, but I get the best "separation of concerns" going in reverse.