It is in fact physically impossible to fully understand a modern desktop PC. Just the amount of lines of code involved makes it impossible to ever read them all, even if you had them. And that's just the software side. I doubt anyone can fully comprehend in detail everything that happens in a modern CPU, let alone the entire hardware system.
Computers are like cities, they can be managed effectively only by dealing with aggregates and abstractions. It's impossible for someone to know every tile in the sidewalk, but it is possible for them to effectively manage sidewalk repair if they have the right abstractions.
it may not be possible to conceptualize all parts of a system simultaneously but that doesn't mean nobody can fully understand the system. A layer of abstraction isn't about not having to understand what's beneath it; it's a tool to aid in understanding.
No, i literally mean there's too much information involved to review in a human lifetime. You can at one point understand any part of it, but a human life is too short to at one point understand every part of it.
Computers are like cities, they can be managed effectively only by dealing with aggregates and abstractions. It's impossible for someone to know every tile in the sidewalk, but it is possible for them to effectively manage sidewalk repair if they have the right abstractions.