All three! Technically speaking, you can develop the objects with just C. However, with Lookout 4.0 and above, C++ is used in the sense that all the files and syntax is in C++.
(Object Oriented Programming is just a concept -- can be, theoretically at least, accomplished with any language, but C++ makes it much easier).
Visual C++ is the compiler Lookout and NI prefers and recommends. You can try using other compilers but may run into compilation problems.. which will not be supported by NI.
So, C++ in Visual C++ environment is the answer to your question.
Hope this helps,
Regards,
Khalid
