There are several ways to deal with this problem.
You could have a look for some syntax highlighter plugin, those will also bring you coloured text with highlighted keywords etc. pp. This is probably nice, if you use code quite often. I use SyntaxHighlighter Evolved.
If you want to do this by hand, <code>
is probably the HTML-element you want to use, just like Stack Overflow does, too. It´s “designed” to be used that way (and understood as code from a semantical view, too).
If you want to prevent line breaks, you can add this to your CSS:
code { white-space: nowrap; }
You have to use this in the text view of the editor though, as the WYSIWYG version would probably strap it out.
You can get around that by defining a shortcode for your code-tag. You will find lots of examples for that around the web.