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The title say sit all, but why does restarting a computer tend to fix things? It seems like IT folks always ask, "Have you restarted your PC?" But Why?

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And yes.... This was a lame ploy to get some rep on SU when the site launched... – RSolberg Apr 3 '10 at 6:07
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6 Answers

up vote 13 down vote accepted

Basically because anything that's got in a mess gets the chance to start over. Imagine you're making toast and you burn it. Throwing it away and starting again is one way to fix that problem and will always work out better than scraping the burnt bits of toast off.

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+1 Nice analogy – LeopardSkinPillBoxHat Jul 16 '09 at 7:12
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and tasty too! like the pizza you dropped before it went in the oven... far better to not pick up all the grated cheese and tomato sauce.. oh wait i think i went too far.. – geocoin Jul 16 '09 at 11:19
Can anyone come up with a better but similar analogy? I'm not 100% happy with this one. – tjrobinson Jul 16 '09 at 19:50
Yeah, restarting your computer is like scraping the burnt bits off the toast and putting it back in the toaster. What you described was reinstalling the OS ;-) – DisgruntledGoat Jul 17 '09 at 18:40
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Ok, imagine you have a whiteboard where you've space to write 5 things you need to do. Every so often you scrub out a task you've completed and replace it with a new one. Now say you accidently pick up a permanent marker rather than a water soluble one to write your new task. When you come to scrub out this task you can't until you wipe the whole board clean with some alcohol. Restarting you computer is "the same' as wiping the board clean, it removes all the "stuck" code – David Hayes Jul 17 '09 at 21:37
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up vote 6 down vote

Good question! The short answer is "it depends"

The longer answer is that Windows has limited resources for applications to use (Memory, Window Handles, File Handles etc.) if a badly written application doesn't give these resources back to Windows when it's finished you Windows run out of resources. This causes problems with other applications. Obviously the same applies to all other operating systems too

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up vote 6 down vote

Two reasons:

  • The OS and software gets to start with a clean slate
  • Any OS / driver updates or installs that have occurred since the latest reboot may need a chance to be part of the boot sequence
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up vote 6 down vote

One of the major reasons your computer slows down is that its Random Access Memory (RAM) is being used. The operating system, as well as the programs you're running, all use RAM. However, there's only so much of it, and it can only be accessed so fast. If your computer is trying to use a lot of RAM (often more than is availablee), it slows down. It needs to create files extra swap files on the hard drive to act as extra, but less efficient, "RAM." This, among other things, makes your computer slow down.

Closing some programs should free up RAM space, but memory leaks may have occurred. That means that the program may have accidentally taken up RAM that it didn't/couldn't free up when it closed. "Ahhh," you say, "it's going to eat up all my RAM!" Nope. If you restart the computer, all the RAM is cleared out. You've got more avaliable RAM, so your computer can run faster.

There are other problems that could be fixed by a restart, too. For example, if a program somehow begins to use a huge amount of processor cycles (each cycle consists of a calculation, and all of these calculations make your computer "computer," aka work). When the computer is restarted, the control of the processor is unconditionally given to the bootloader, and then it's handed off to the OS, which can start from scratch. It's no longer being dominated by the greedy program.

Yet another possibility is that the computer was overheating. Overheating, simply put, isn't good for the computer. Turning a the machine off and leaving it to cool for a few minutes couldn't hurt. In fact, some (if not all) computers are set to shut down if they reach a certain internal temperature.

In summary, a restart puts the computer into a state where the right software is controlling the right (possibly cooler) hardware, in a state this is already known to work right.

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I once had a Dell Inspiron with a Pentium 4 inside. In summer, it would occasionally switch off without warning. It turned out dust had built up inside, causing it to heat up until it hit 75 degrees celsius, which is the temperature at which P4s automatically switch off.. – John Fouhy Jul 16 '09 at 1:40
The memory leak issue isn't really that relevant with any NT based (Windows 2000 and onwards) or Linux OS. Sure it used to be the case for DOS, but modern OS's will recover all them memory a program was allocated, leaked or not, when it closes*. It's theoretically an issue for services and the like, but these are generally pretty solid in the first place. * Because the memory allocation algorithms these OS's use are not the simple mem allocs you might expect. – user2630 Jul 17 '09 at 18:19
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up vote 1 down vote

Have you ever watched "The IT Crowd?"

IT support people use "Try restarting it" as the first response because:

  1. It often will make the problem go away, at least temporarily.
  2. They don't need to exert any further effort.
  3. They don't need to have face to face contact a human being.
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my wife worked in a place where 'have you tried turning it off and on' was the official first response. she had a problem that caused her desktop to blue screen causing loss of work on a regular basis, however she could never get a fix as 'turning it off and on' always 'fixed' the bluescreen! – geocoin Jul 16 '09 at 11:23
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up vote -1 down vote

To clean the RAM probably

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