Ada 95 and the subsequent revisions Ada 2005 and Ada 2012 are highly upwards compatible with Ada 83. In particular, the design intention was that the difficulties associated with moving from Ada 83 to later versions of the standard should be no greater than those that occur when moving from one Ada 83 system to another.
However, there are a number of points at which there are minor incompatibilities. The Ada 95 Annotated Reference Manual contains full details of these issues as they relate to Ada 95, and should be consulted for a complete treatment. In practice the following subsections treat the most likely issues to be encountered.