AdaTutor is an Ada 95 tutorial program written by John J. Herro. It has been placed into public domain by John.
It is a great tutorial although it only touches on Ada 95 and does not contain information for Ada 2005 and 2012.
Here I have the AdaTutor presented on the Web.
You could visit my blog to browse directly on the web.
The HTML version is licensed CC0 1.0 Universal (CC0 1.0), in other words, it is in public domain.