It may also be noted that some programs, like AOL, if left running in the background, on a computer which is left running constantly can degrade. Then you have to reboot to restore the program to the origonal configuration.
Mark
The link to the Mailbag answer is: Should I leave my computer running when it’s not in use?
I asked my grandfather this a couple of years ago. He was a computer designer for Texas Instruments for 30 something years, so he has the qualifications. he says that it doesn’t matter much anymore. the reason you were supposed to leave it on in the past is because the hard drive spins and when you shut it off, the reader would slide to a rest on top of it. (imagine a turntable) But in recent past, designers have designed a specified place on the drive for this purpose. The real problem is having some outside force (your comp sci 101 friend) screw something up while you’re not there.
All this science, I don’t understand. It’s just my job 5 days a week-- Rocketman
I used to work in a large data center with more than 3 terabytes of hard drive storage. The systems, including the hard drives (refered to as DASD) ran constantly, rarely being shut down. I observed that there was a slight tendancy for some of the disk drives to have problems after being started back up after a period of being shut down, and this was even more so if power was suddenly dropped.
To summarize for best hard drive reliability, the best option was to keep the drives running constantly, followed by shutting them down gracefully, followed by a sudden, ungraceful shutdown.
I remember those old hard drives that you couldn’t just turn off. (Well, you could…) The read/write head that normally floats on a cushion of air caused by the rotary motion would fall on the disk’s surface, possibly causing some damage, at least in the long run. However, you could turn them off safely by using a “park” utility that put the head in a specific position at the edge of the disk. But that was at least ten years ago. All modern drives have an “auto-park” feature that uses the rotary energy of the disk itself to park the head even at instant shut-off.
Recently I was talking to my uncle, and and was surprised to find out how early he had been using computers, when he mentioned that they hated it when a program went into an infinite loop, because that required shutting down the computer to reset things, and they usually had to also replace a couple of vacuum tubes which wouldn’t power up any longer.
The reason for degrading computer preformance in the long run is from “memory leaks”. In you computer, you only have so much RAM. Each program uses some of it. In addition, they use “dynamic memory”- they request large portions of RAM while running the program to store data with unknown sizes (files, web pages, etc.). This is fine, so long as they remember to “free” it- tell the OS when they’re done with it, so the OS can give it out again. A lot of programs, due to either poor planning, rushed delivery schedules, honest mistakes, or pure carelessness forget to free it. The OS then doesn’t know its done with the memory, so it never gives out that section again, and it becomes lost. The only way to reclaim it is by restarting, which wipes out the OS’s memory of what is used and what isn’t. Thats why computers seem to run faster/better after a restart- they have more available RAM and have to use less “virtual memory” (using your slow hard drive for RAM).
As for turning off/on the computers, I would say it doesn’t really matter for most PCs. The hardware is built with shutdown in mind. I would suggest using the OS’s shutdown command instead of hitting the switch (especially for Linux, it doesn’t matter nearly as much in Windows), but turning it off will do absolutely no damage to the computer. Neither will leaving it on, unless you generate a tremendous amount of heat (again, not a concern for the average user. Overclockers mileage may vary). I base my decision on whos paying the electric bill and what special phone deals I get for my internet calls. At home my parents have a per call deal on local calls on the internet line, so its cheaper to keep it on then ever shut it off.
He who is truly wise is the one who knows how much he has yet to learn.
There’re also the issues of crappy 230W (+/- ~100W) power supplies (built someplace like Malaysia and sold across the nation as if they are low-cost but otherwise the same), and power spikes big enough to get through any “surge protector” you or I are ever likely to see.
For the first (cheap P/S), I really don’t know which is worse - stressing them by turning all the loads on at once, or leaving them on all the time, running a little too hot because they are actually (though not according to the label) overloaded.
For the second, whether or not you should leave the circuit closed (power ON) depends upon the answer to another question, specifically: who pays for the new, faster, better in almost every way replacement for the system that blew while you were away? My dad works for the county here; they recently had a power surge that blew out half the desktops at one facility - specifically, the half left on over the weekend. THOSE people got faster replacements. The people who saved their computers by shutting them off still have the old, slower models with less storage and memory.