'Reference' doesn't mean C++'s reference, it means that you pass where the data is, not the data itself. Even Visual Basic had this concept.
Unlike C++, C does not support pass-by-reference (ignoring preprocessor silliness). Passing a pointer by value is not the same thing. edit To be clear, C++ supports both pass-by-value and pass-by-reference.
This topic cropped up a year ago: https://news.ycombinator.com/item?id=23553574
Wasn't there, but pretty sure in 70s, the notion of pointer and reference (and 'handle', etc) were pretty much interchangeable, since AFAIK there wasn't any compiler capable of creating a compiler-checked 'reference' construct.
so, if this is true, in the relm of asm, since really we are just dealing with bits in a register that could be interpreted as data or addresses, it makes sense to treat pointer and reference interchangably, since there is no such thing as a higher-order 'reference' anyway.
[0] Amir M. Ben-Amram and Zvi Galil. 1992. On pointers versus addresses. J. ACM 39, 3 (July 1992), 617–648. DOI:https://doi.org/10.1145/146637.146666
In that case perhaps the response should have been "pass-by-reference doesn't exist on machine level", not "pass-by-reference is something different", as the latter would seem to be a category error.
Which would barely make any sense.
A typical CPU deals with abstractions like jumps and copies, and has no real concept of a function call. It seems fair to say that, at the level of a typical assembly language/machine language, there is no argument passing, and therefore no evaluation strategy. Same goes for a Turing machine.
> I'm reluctant to bikeshed
This is the kind of topic where precise phrasing is important, so I wouldn't chalk it up as pedantry. It doesn't help that Java muddied the waters with its use of the word reference.
[0] Here's the link again: https://news.ycombinator.com/item?id=23553574
Kinda, but that difference is important. We can say that C allows us to simulate pass-by-reference by using pointers. It's still true that the C language does not support pass-by-reference semantics.
Taking the address of a variable is an operation that the C language permits us to do, yielding a new value (a pointer value). This isn't part of C's argument-passing functionality, though.
> What does the 'ref' keyword change about how C# passes the argument to the function?
The internals of C# compilers aren't really the point, but I believe .Net does it the copy-intensive way, copying to pass in and copying again to pass the new value back out. I don't think this a real performance problem though, unless you overuse the feature.
It's not a C++ concept, I only used C++ in that example simply because godbolt.org makes it really easy to show how the language treats the two concepts differently even though they compile to the same thing.