You can use a different text editor than the one that's included with the IDE, but you'll lose the integration of the various views and perspectives. For example, within the C/C++ editor, you can set breakpoints and then see them in the Breakpoints view, or put to-do markers on particular lines and see them in the Tasks view, or obtain hover help as you pause your cursor over a function name in your code, and so on.
If you want to use other editors, you can do so either externally, or within the IDE.