When a computer system developer needs to maintain self-propagating and self-altering programs, the most common way to do so is to create maintenance programs that will run along the way with the main program, similar to the anti-virus or disk defragmentation programs that we have on our computers. These programs are not really part of the operating system, but they are crucial in maintaining computer stability, especially if it is heavily loaded. Our world has many of these programs running, including ones that control the spinning of our planets, stars, and galaxies. Other very close ones include the weather and seismic movements.
Why do I call them programs? Because if you deal with computers, everything that happens there is a program, including the operating system. In my view, programs, which are self-altering or self-propagating, one way or another, are "alive" (including us). The rest is what we call an "Operating System", "System Services," and "Applications".
If you want to maintain control over your computer system, you need to have programs that will cause system adjustments in case some program starts running out of control. In our search for immortality, for example, if we crack the code, this may throw some red flags that will cause a major shift in the tectonic plates that could wipe out the entire or a portion of the population, or a comet could hit the Earth causing a global extinction and reboot / repopulation with new species, or something else of the sort.
Those above are really global things. More often people deal with more localized issues where they get acquainted with Angels and Demons. Certain small violations of rules are happening left and right in the self-evolving systems. There are minor touch-ups done here and there to maintain the balance. One is saved by a miracle while the other is killed or becomes crippled for no apparent reason. One is steered in the sleep to do "the right thing", while the other has nightmares. One receives the Nobel Prize for an accidental discovery, while the other loses his or her mind spending a lifetime in a dead ended search for something. Tyrants live long lives, while progressive and humane leaders are being killed as soon as they start bringing positive changes to the world. There are many things happening that are beyond simple understanding. Before every battle, soldiers pray to their gods, saints, and angels for protection in the upcoming deadly clash, but the angels who save soldiers on one side of the battle are in fact demons for the opposite side and vice versa. Why one is saved and the other one is killed is beyond our understanding. All we can do is grieve for the ones lost.
If we think about it, Angels and Demons, as we call them, are programs performing tasks assigned by the Creator, shepherding us in the direction that would maintain the balance of the Creator's computer system. Also, we, humans, are self-altering entities with chaotic alterations permitted. We call this "free will". Angels and Demons are pretty much fixed in their duties to stabilize the computer, so no "free will" for them. They are also immortal, by our standards, but the Creator can terminate them at his pleasure.
It is amazing how much wisdom humanity has accumulated. Our curse is that we understand everything way too literally.