I was trying to find a more appropriate tag for this question and couldn't. It is about implementation of variables, but not really about programming languages. It is not really computer architecture (but it is a bit related). It is not really memory-allocation, but it has something to do with memory and the way we keep information in the computer (e.g., register vs memory).
I feel that a tag is missing here, but can't put my finger on the right terms. "implementation"? "Low-level Design"? "hardware-software relation"? Help?
I had a similar feeling with Could you explain this signed fixed point number equation?; it is definitely about binary arithmetic, but I felt it should be tagged also as related to computer-architecture (which it is not!). As if a tag that deals with the implementation of things is missing.