You should be able to edit text in a familiar manner regardless of what kind of text it is. It might be source code, or it might be an email, a webpage, a document, your shell, a debugger, or anything else you can think of. No matter what you're editing you'll have the same features, keyboard shortcuts, etc available.

A programmer who wants a good universal text editor will find one that also has good integration with their compiler and debugger; emacs and vim are both pretty good choices there.