This manual contains useful information in writing programs using the GNAT compiler. It includes information on implementation dependent characteristics of GNAT, including all the information required by Annex M of the standard.
Ada 95 is designed to be highly portable. In general, a program will have the same effect even when compiled by different compilers on different platforms. However, since Ada 95 is designed to be used in a wide variety of applications, it also contains a number of system dependent features to be used in interfacing to the external world. Note: Any program that makes use of implementation-dependent features may be non-portable. You should follow good programming practice and isolate and clearly document any sections of your program that make use of these features in a non-portable manner.