Ada 2012 redux

January 14, 2013

Jack Ganssle-January 14, 2013

Readers complain that there's little support for Ada on 8 and 16-bit processors. Is that the case?

Ada tends to be used on relatively large systems that require lots of processing, so our customers are not pushing very hard in the direction on small processors. That being said, if you look at the GCC technology, all GCC targets could potentially have support for Ada. In particular, we have AVR 8 bits ports. So it's not really a technical limitation at this stage, more where the market pressure is coming from.

One very interesting argument I've seen before is that Ada by itself adds little to the development of highly-reliable code. Some people suggest that Ada users are just better or more careful developers, so would excel working in any language. It's an interesting thought, since it implies that some (or too many) non-Ada people are less competent or less careful. Care to comment?

I would go even beyond that and say that the language by itself has little impact on the reliability on the code being developed. What really matters is the development environment: the language, its toolchain (compiler, debugger), its editing environment (IDE), its analysis tools (static and dynamic) and its testing capabilities. And, of course, the competence of the team.

What the languages provide are foundations to put this environment together, in particular with regard to static analysis. Many errors can be detected at compile time and an entirely new class of errors can be detected by the static analysis tools, much more than C. This is really a key to developing reliable software.

Now to the developer competence discussion. Thinking that a bad developer can do a good job because he has a good language is a myth. No matter what the technology, you need good, competent people. Ada allows these developers to be more productive because they can develop software at the right level of abstraction and use the semantics of the language to obtain guarantees and proofs that they would otherwise only gather through painful analysis.

Another interesting point relates to big systems developed and maintained over decades. With millions lines of code, no matter how good the team is, nothing can prevent you from making mistakes (not even Ada). What you need are all possible means to mitigate as many mistakes as possible and concentrate on the few that can't be prevented. That's what Ada is offering.

Finally, C provides surprisingly little support for the separation between specifications and implementation or helping with global program architecture.For example, headers files are merely a convention with no dedicated language features behind them, there are different ways of handling global variables, and C doesn't provide namespaces while C++ allows distributing them across several files. Ada provides a nice way of identifying programming modules, separating the specifications from the implementation, and providing the specification with high level semantics such as strong typing, parameter modes (e.g., readonly, and read-write), data ranges, etc. In a way, this makes Ada usable as a programming tool as well as a design tool.

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