[cgranade]

That would also break the trick of declaring something `const volatile`. While that seems like a contradiction, I've heard of it being used to force the compiler to include a symbol in the final object file. In particular, I've seen it used to make a poor-man's plugin architecture.

[msandford]

It's not as crazy as you think. "volatile" means that something else other than us can change the value, somehow. "const" means that we aren't allowed to write to it.

So what is that? It's any kind of input. Like memory mapped GPIO.