How is a computed existence different from a non-computed existence? Because some theorize our world is a simulation, it implies the existence of computed existences and non-computed existence. Did philosopher address this question?
I think your terms may need some defining to get a good answer. The whole "simulation" argument is interesting and quirky, but may say more about the paradoxes of probability than "reality," if I may use such a vulgar term.
Since you use the word "computed," not simply discrete and "computable," I guess this would entail an updated argument from design, positing some rational entity doing the computing, a real Laplace Demon at the cosmic keyboard. Then did this "computing entity" or "designer" design itself?
It seems to me we just reintroduce all the old questions of theology under a different terminology. We are just updating God the universal designer with a more restricted God the computer programmer. As Xenophanes said, if horses had Gods they would resemble horses.
Or we could drop the demon and suggest that a universe made of discrete elements "computed" itself into existence, in the manner of John Wheeler's "it from bit" maxim. This is more of an observation about methodology and the universal applicability of information theory, I believe, and otherwise leaves things as they were.
You also distinguish between "computed existences" and "non-computed existences." I'm not sure, but I think the simulation thesis would imply that it's computation "all the way down," which I suppose is an improvement on the regress of turtles thesis, slightly more evidence.
Those "non-computable" and therefore "non-computed" existences could be a definition of life or of rational consciousness. Others might think differently, but I suspect that there is some insurmountable Goedel-type contradiction in the notion of self-computing, so that whatever is meant by "computed existence" will mean something external to it.
In set theory, computability is an example of countable order. The numbers under this heading sum at a so-called "large countable ordinal," which notwithstanding its "height" is still encoded into the smallest transfinite cardinal. I'm not smart enough to grasp the details but Turing is historiographically relevant so I assume the set-theoretic notion of computability underlies much of what is possible, here.
Now, physical space is a melange of continuity and discretion, so might be computable in the latter state, but is not only incomputable but also uncountable from the former condition. If the world is a computable simulation, it must either involve a broader (more directly physical) image of computation (perhaps quantum in this case) or something beyond strict computation (if we don't extend the image itself).
EDIT: At the least, if a computer was simulating continuous spacetime, it would have to have an uncountable imaging function, so to speak. Otherwise, how do we have an intuition of continuity in our perception, being simulated?
The computed is such representation which is not that of the actual / physical entity [system].
If your system is computed using electricity than its very nature is unstable and transient as such resistance of its components defines its operation and thus easily influenced by pressure et temperature.