when a computer freezes, what is actually happening to the system and components?
In: Engineering
There are a lot of reasons for a computer to freeze, but ultimately it means that it has stopped responding to input or doing much if any processing.
This can be because it’s stuck in a loop. Consider this simplified version of an operating system. The computer does the following steps in order:
1. Check input from mouse, keyboard, etc.
2. Act on that input (do whatever a click does, or a keypress)
3. Check for important system requests, like “close a program” if the user clicked exit or “connect to wi-fi” if a wi-fi signal is in range
4. Do whatever those system requests requested
5. Go back to step 3 and check if the system request is still there
6. Go back to step 1 and start everything over
If step 4 somehow fails – you clicked exit but the program doesn’t want to stop yet – then the computer will just perform steps 3, 4 and 5 over and over and you will never get back to step 1 and the computer won’t be able to respond to your inputs.
Real-life computers don’t hit this specific issue, but it’s a simplified version of how they can get stuck due to software issues.
Hardware can cause this as well. Your computer might have an instruction that says “Save this number to RAM and wait for confirmation that it is saved.” If your RAM is faulty, it will never get the confirmation and remain stuck. If your CPU overheats, it will slow down and may have issues correctly performing operations, resulting in it getting stuck.
The processor has an input “pipe” and an output “pipe”. Typically, a modern processor can handle taking input from various sources at once without a noticeable delay, but occasionally it will get stuck on one task. When that happens, the entire input pipe is shut off while the processor thinks about the problem that it is on. Usually it recovers, and opens the pipe again.
A similar issue can happen with RAM as well. Basically, the general concept when a computer freezes is data can’t get where it’s trying to go, because a part of the hardware is struggling to process something, which is holding up everything else. Like a pileup on the freeway.
TL;DR: These days, is usually the computer detecting some internal glitch and shutting itself down rather than risk worse.
On a modern computer, it’s usually that the system has detected something wrong and shuts itself down to prevent data corruption or security risks. That’s the windows blue screen of death. Imagine a play rehearsal where somebody flubs a line and the director face palms and says “ok everyone, from the top.”
Systems are pretty well protected from software flaws these days, but there are some components that’s hard to do for. Problems in the deep reptile brain parts of system software can still cause freezes. That’s the software that directly works with hardware.
Electrical problems can cause freezes. There’s an amazing number of things working in very close synchronization inside a computer, and if something glitches that it can get to the digital equivalent of gears grinding. But at a trillion RPM. So it just stops instead.
Finally, you can have it get so slow it feels frozen. Like people, switching attention is one of the hardest things for computers. It can take a computer milliseconds to go from one task to another! So, if a few things get stuck interrupting each other, the computer can show to a crawl. Computers manage resources by moving things around internally, which is great, but as the demands start to exceed resources, they’ll spend more and more time juggling, eventually entering one-armed wallpaper hanger territory.
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