First up, KDevelop is currently a waste of time. KDevelop3 is a pain, and Kdevelop4 is still in beta and (I find) way too unstable for any serious work. If you need an c IDE Qt Creator (personal favourite, even for straight c) and NetBeans are the two best Linux ones (imo).
I read the diff/sdiff/diff3 info page. Just to compare file differences... KDE has a nice file differences compare app as part of Kdevelop, which might be easyer for me (I think in visuals and not in a logical order, if you know what I mean ).