On Windows it's called Virtual Memory and is an option you can modify. On Linux it's something you choose the size of when setting up the system and is called swap [probably the same for most UNIXes].
As a real easy one liner: "Swap/Virtual-memory is when the computer runs out of real memory and has to use the hard drive as very slow pretend memory" The existence of a swap file is not necessarily bad, it's probably not using it, but when you switch applications and hear your computer 'churn', it's often due to swapping. [Not when you open a new application though]. Obviously things get bad if you're running low on hard drive space. This is why a swap file often exists before you need it, so that using up your hard drive doesn't suddenly mean you have no swap left. On my machine, I seem to have 256M of swap. It also has 766M of memory or some such, so it thinks it has 1024M [1G] of memory available and will churn slowly from 766 upwards until it runs out. It does still run out though, I've not seen an OS that expands its swap as needed as that usuallly requires a reboot. Hen On Thu, 29 Apr 2004, John Robinson wrote: > Bill, > > Many thanks, like Marta I am glad to be educated on this, and yes she > was right there were others of us that needed this and just didn't have > her guts to ask. > > John R. > > > On Apr 29, 2004, at 9:25 AM, Bill Rising wrote: > > > On 4/28/04 19:37, Marta Edie wrote > > > >> Well, here comes the ignorant old lady again. I know you know it all, > >> but I have no idea what swap files are. And where do you find them > >> and what are they supposed to do and are or are not doing? And what > >> garbage is not collected? I am sure there are others on this list who > >> don't know and would like to, just don't have my fortitude in asking. > > > > Launching applications, opening documents, surfing the web all cause > > the > > operating system to allocate memory to hold relevant data and commands > > to > > process the data (such as where windows are and what they need to > > display). Typically, this memory comes from RAM (random access memory) > > of > > some sort. If the computer needs to allocate more memory than it has in > > RAM, it moves some of the non-recently used info into Virtual Memory > > (VM), which is really in a file on a disk. Since memory is being > > swapped, > > the files which hold the stuff in virtual memory are called swap files. > > > > Large amounts of swap files is worrisome on a machine with a lot of > > RAM, > > because there should be little need for the swap files. If there are > > too > > many, it might be because applications are not telling the operating > > system that they no longer need the memory they asked for, and they > > keep > > asking for new memory (this is a memory leak), or because memory is not > > deallocated when applications quit (lack of garbage collection). > > > > This info could be wrong in the details, because it is inferred from > > reading, and not from actually reading up on how memory allocation > > works. > > Still, it should be roughly correct. > > > > Bill > > > > > > | The next meeting of the Louisville Computer Society will > > | be May 25. The LCS Web page is <http://www.kymac.org>. > > | List posting address: <mailto:macgroup at erdos.math.louisville.edu> > > | List Web page: <http://erdos.math.louisville.edu/macgroup> > > > > > > | The next meeting of the Louisville Computer Society will > | be May 25. The LCS Web page is <http://www.kymac.org>. > | List posting address: <mailto:macgroup at erdos.math.louisville.edu> > | List Web page: <http://erdos.math.louisville.edu/macgroup> > | The next meeting of the Louisville Computer Society will | be May 25. The LCS Web page is <http://www.kymac.org>. | List posting address: <mailto:macgroup at erdos.math.louisville.edu> | List Web page: <http://erdos.math.louisville.edu/macgroup>
