Ada portability-is it oversold?

It is argued that Ada code is not as portable as was first hoped. However, many of the nonportable sections of Ada code are much more easily identifiable than in other programming languages. It is further maintained that, any real programming project, it will be almost impossible to transfer code from one architecture to another or from one compiler to another without at least some changes. Changes will be required where the program accesses the file system or operating system. The programmer should also be aware that there are other issues which will affect efficient portability of the Ada code. The stack and heap handling will differ between compilers, and this can affect run-time efficiency. It is concluded that designers and developers of real-time programs, such as simulators, need to understand the portability limits of their code in order to make effective life-cycle decisions about these projects