Don't change URL when subject changes?

Let's say I edit the subject. Is there an option so that the URL does not change?

I just edited it, the initial subject was this:

http://www.webmasterstalks.com/seo-4-smf/is-it-possible-for-the-url-not-to-change-when-subject-changes-t1632.0.html

However, I still see that the initial URL leads to the same page. Is it because it is cached or redirected?