Like when you’re restarting your computer or console.
You have it make itself turn off and on again, how does it turn itself back on after being turned off?
In: Technology
it doesn’t actually turn off, as in the power is off and everything is disabled, it just follows the shutdown sequence, and then follows the startup procedure, effectively this achieves pretty much the same result, just it’s a different way of putting it
The computer is actually a collection of several small computers working together. Mostly we just think about the one that runs programs.
But there is also another small computer that deals with power management. This is especially true in laptops, because they need a small computer to manage charging the battery. THIS small computer is technically always on.
So when you shut down your computer, the OS knows how to talk to this small computer. Once the OS has cleaned up all its mess and tucked itself in, it sends a signal that means “please shut down”. Then the computer in charge of power stops providing power to most of the components of the rest of the computer.
Or, for a restart, it may shut off the power for a short time then turn it back on again. Sometimes that process doesn’t really involve turning things off. It just involves a slightly different computer that’s in charge of “warming up” the hardware and getting the OS ready to run. If the OS tells that thing to start over and do its checklist from the beginning, it looks like the computer was shut off and turned back on even if the power hasn’t been removed.
Frequently asked question, for example, one month ago: https://www.reddit.com/r/explainlikeimfive/comments/1bedvku/eli5_how_does_a_computer_prevent_itself_from/
Let’s just imagine a basic desktop computer.
When you turn it on from scratch, the motherboard loads up its firmware from a predetermined area. That startup is all done using some predetermined circuitry, and from there it starts down the branching paths.
The firmware contains different techniques for booting off of storage mediums. It’s likely configured to look at the primary storage device. That storage device contains a Master Boot Record at the *very beginning* of the drive. That MBR contains information on how to load more bespoke software somewhere else on the disk, such as a Windows installation (this is also where you would configure a dual-boot scenario).
And once you’ve started loading the OS, the sky’s the limit.
Actually, you got it backwards! Reset is a built-in operation in most computer components. It doesn’t require you to turn them off and on again – you just send a “reset” signal, and that’s it. Reset forces the components to go into their predefined “startup” state.
On the contrary, many components actually require a mandatory reset after power on! Without a reset, they wake up in a some kind of “zombie” state, where they cannot do anything useful.
Computers usually have a special component, who’s job is to automatically send a reset to all components, when the power goes on. Without that component, you would have to manually press the “Reset” button each time you switch power on.
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