Hey there!

I have heard about editing the Linux kernel to create operating systems, but how? I would like to create my own personal operating system just for fun, nothing big, and I'd like to use the Linux kernel. It would just have basic software on it, and would be able to read from the Floppy, CD, and maybe a DVD drive. I know where to download the kernel, but once I do, then what? Where do I open it to edit it? What language is it in? I know some C, C++, and Perl, and other languages. Does anyone know a good book I can get started on this with?

Thanks!
~Matt

That's no small task if you're unfamiliar with all of the things you'll need. You could try starting at http://www.linuxfromscratch.org/ and see if that's what you want to do. You could also start with an existing distribution, customise it and produce your own distro from that.

I haven't done either of those - I'm sticking with Slackware...

It may be good to define some semantics....
"operating system" means kernel + all the other utilities---this combination is what is commonly called a "distribution"
The kernel is not "edited"---if you want a custom kernel, you modify the source code a re-compile.

I can't tell from you post if you want a custom kernel or a custom distribution. For the latter, Linux from Scratch is a good source of info---but you can also use something like Gentoo to make a custom setup.
If you want a custom kernel, you can find all the relevant documentation at TLDP