What does % mean?

[cpubrain]

Hello,
I was doing the Windows XP tweaking like in the article. Then I came across this:
Prefetching is a process unique to XP, which stores temporary settings that help load frequently accessed files and applications faster. However, after a time, the folder gets clogged up and overloaded, much like the temp directory found in all Windows Operating Systems, and needs to be cleaned out every so often. Go to %systemroot%Prefetch, delete everything in there and reboot. This should be done as often as you normally clean out your temp directories.
Where is this and what do the % signs mean? Is this a folder, or somewhere in the registry. I have seen this in some books also, the percent sign. I would be happy if someone could explain what this is?
Thanks

[EzyStvy]

%systemroot%Prefetch - one way to describe it, is it's a Wildcard command...

99% of the time the Prefetch is located at C:\Windows\Prefetch with C:\Windows being most people's system's folder.

[doctorgonzo]

It's an environment variable. Right-click on "My Computer", select Properties, go to the Advanced tab, and then click on Environment Variables. You will see some of the variables listed there.

You can also open a command prompt and type "SET" to see a more complete list.

Some common variables you may come across are %SystemRoot% (usually C:\Windows for XP, C:\WinNT for 2K) and %UserProfile% (where user files are stored, usually C:\Documents and Settings\username).

So if you see something that refers to %SystemRoot%\Bob\Joe, and your system root is C:\Windows, then the path for your computer would be C:\Windows\Bob\Joe.

[cpubrain]

Thanks, why would a person need to change a variable? For instance, under enviorment variables in "MY Computer" properties, TEMP is used as a system variable and a user variable. How can that be? When I type temp in the run command it opens up the system folder path and not the user folder path. And TMP which is in the system variable list, when typed in the run command opens nothing. Why would anyone want to create a variable? If you don't mind taking the time to explain this that would be great, if not, that's cool!

[doctorgonzo]

Variables exist so that programmers can take advantage of them. For example, if a program needs to create temporary files while running, a well-run program will put those files in the %TEMP% directory instead of just putting them someplace random. That way, all of your temp files are in one place, and it is easy to delete them. Of course, there is nothing that forces programmers to do these things, but it is good programming.

Users almost never have to create their own variables. If a program needs a variable, it will be created when the program is installed. Users may want to change variables (like %TEMP%) if they don't like the defaults. For example, maybe a user has an entirely separate partition for temp files, and he wants to use that instead of something else.

When there are two variable of the same name, I believe that the user variable takes precedence over the system variable. For example, when I open a command prompt and type "CD %TEMP%", it goes to the location specified in the user %TEMP% variable, not the system %TEMP% variable.

[cpubrain]

Thanks for explaining that Doc. I take it in other words, the common Computer user does not need to bother with variables ever! I found the folder the article was talking about cleaning up.
Thanks again!

[Corky]

There's a small free program called Prefetch Control (check Google) that cleans the Prefetch. I have it on a floppy and run it every Saturday as part of my regular maintenance.