Steve,
Ignore the <code> tags, they're superfluous in Francis' wikicode.
By simply indenting each line with a space, the text is stopped from being reformatted (it still interprets Wiki markup and special characters, like →):
hello
world
Alternatively, the <pre> tags will also stop the text being reformatted, but will instead ignore Wiki markup (but not special characters, like →):
<pre>
hello
world
</pre>
Useful link on Wikitext, the markup language, found through the Help page here:
http://meta.wikimedia.org/wiki/Help:WikitextThey might exist, but I've not personally gone looking for an off-line editor, persay, though someone may also have written a definition language template for syntax colouring in popular programming editors (maybe Notepad++?) - you'd have to look. I think I've heard you might be able to use
TiddlyWiki as an off-line wiki and then synchronise it with an online MediaWiki wiki, such as ours, using plugins - though I've never tried it.
Sam.