Since the 7.0 release of EiffelStudio, BIT types are almost gone. To be precise they are not completely gone but your code will not compile out of the box if you are still using them. To make it compile, you need to define the ECF variable USE_BIT to bring the BIT types (See http://docs.eiffel.com/book/eiffelstudio/release-notes-eiffelstudio-70 for the release notes).

So far, we haven't heard of anyone missing them, therefore in the forthcoming release of 7.2 in the fall of 2012 we will fully remove BIT support from the Eiffel compiler.

Farewell, BIT