I consider ultra book too big. My ideal size would be something like 6" phone.
Are you referring to developing using C++ language in a 6" screen sized phone ?
If this is what you are referring to, then I think you better get ready for higher degree in myopia and long compilation time. It has nothing to do with which language you are developing with, I'm skeptical whether you will be able productive with such a small screen set and tiny fonts. It will be curious if you can remember all the SDK API and you don't need extra screen assets to view these documentation online ?
Any compelling reason why you need to develop in such constrained environment ?