It doesn't matter. The fact that you're able to compare the Hello on your "screen" to the Hello in your "memory" should prove to you that there's at least two of them. A computer can't distinguish if it has started running in the middle of a computation with its registers and memory arbitrarily filled with values, but it can still arrive at results based on those values. Likewise someone might very patiently turn a computer on and off while each time filling its memory and registers with data that would be consistent with the equivalent computation as if it had been running each step of the way. That would mean whoever is doing that needs to hold at least as much state as would be necessary to execute the computation normally.