eli5: What actually happens when you “restart” a machine – does it switch off? If so how does it start itself again?
In: Technology
Think of a computer as someone working in an office at their desk.
Let’s imagine that this person is extremely forgetful, and needs to follow some set steps in order to start their day. Imagine these steps are on a card they have in their pocket. In a computer these steps are called a basic input output system or BIOS and are stored on a very small chip on your motherboard. Whenever the computer starts up, it runs this program. The program may do things like run basic tests, and discover what storage is attached to the computer, and try to hunt down your operating system (e.g. Microsoft Windows or Mac OS or Linux).
Imagine that in order to work with any information, our office worker needs to locate and make a copy of it, bring the copy to their desk, maybe make changes, and then file away their results **so they don’t get thrown away at the end of the day**. In a computer, this desk is a type of storage called random access memory. It’s where the computer needs to copy data before it can be worked with. Note that random access memory needs constant power, or it’ll be cleared.
Think of shutting down the computer as ending the office worker’s work day early: Literally asking the worker to file away what it can, and then asking them to go home while their desk is cleared. In a computer, shutting the computer down signals all programs that the random access memory’s power will be cut soon, and then asks the computer to cut its own power. Usually there’s enough time for programs to quickly copy what they were doing to other types of storage, but there are ways you can shut it down that don’t afford it enough time. For example, if you literally pull the plug, data that was only in random access memory will be lost.
Restarting a computer just turns it off and turns it back on. In the office worker analogy, it’s like being asked to leave and go home, then being called back in.
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