"High" and "low" are relative adjectives. The meaning of "high-level language" has changed. C was considered a high-level language, and it is now considered a low-level language. Not by everyone, of course. There are still a pair of definitions for "high-level language" and "low-level language" that draw the line right above assembly. I won't say "nobody" uses those definitions anymore; lots of people learned them and many still use them. I will say that it is pointless to act as if those are the only definitions of the terms anymore.
I think I'm confident in saying that K&R saw C as lower-level language. As you say, it is relative [1]. I just don't think enough people considered C to be a high-level language (given that Smalltalk, APL, and Lisp were about) to make your broader characterization that "C was considered a high-level language."
They describe what "low level" means to them: "This characterization is not pejorative; it simply means that C deals with the same sort of objects that most computers do. namely characters, numbers, and addresses."
And on page 2 we see how they don't regard C as the lowest level: "Of 13000 lines of system code, only about 800 lines at the very lowest level are in assembler."
Now to the [1], I found the paper "Implementing LISP in a high‐level language" from 1977, where that high-level language is BCPL, which is a precursor to C, so clearly a good number of people at the time would have considered C a high-level language, at the very least in the context of developing a Lisp.
K&R are not the last word on this. They made their comment in 1978, and now it's 2021, and computing is very different.
"Characters, numbers, and addresses" are very much not what CPUs deal with internally today. Most languages no longer reference addresses directly, and "characters and numbers" live behind abstractions of their own.
The point is that C assumes a certain model of computing that was baked into both hardware and software from the late 70s onwards. That model has been superseded, but hardware and software still lose a lot of cycles emulating it. The claim is that this is both inefficient and unnecessary.
But the advantage of the C model is that it's simple, comprehensible, and general.
If you expose more of what goes on inside a modern CPU, programming becomes more difficult. If you build a CPU optimised for some specific other language abstractions you bake other assumptions and compromises into the hardware, and other languages become less efficient.
So if you want to replace the C model you'd first have to define an industry standard for - say - highly parallel languages with object orientation. That is not a small or simple project. And previous attempts to tie hardware to more abstract languages haven't ended well.
So C persists not because it's high or low level, but because it's general in a way that other potential abstractions aren't.
This is not to say that alternatives couldn't be both more general and more performant. It's more a reminder that designing performant alternatives is harder than it looks, and this is not a solved problem.
My guess (FWIW) is that nothing credible will emerge until radically new technologies become more obviously better for general purpose computing - whatever that looks like - than current models.
People don't call C high-level, but I also don't see people call it low-level even in a casual setting with newer programmers. Instead I see it called a system-level language.
> It has been closely associated with the UNIX system, since it was developed on that system, and since UNIX and its software are written in C. The language, however, is not tied to any one operating system or machine; and although it has been called a “system programming language” because it is useful for writing operating systems, it has been used equally well to write major numerical, text processing, and data-base programs.
So it sounds like they're endorsing that concept, and just don't want it to be a limiting term in terms of what people expect in regards to portability and scope?
"System level" does that just fine right? There's not much confusion about if C is tied to Unix anymore after all...
I really don't understand the aim of your inquiry.
Yes, I see it called a systems programming language.
But unlike you, I see people call it low-level. The easiest counter-example was to point to K&R, which was my textbook in college. (Yes, pre-ANSI). And there are many people who still say that, as I found in a quick Google Scholar search:
No, I can and I will, and it will still be truthful.
Because to most people with a firm understanding of the nature of English my statement means:
"When I, in current times not 40 years ago, hear people talk about C, they most often refer to it as a systems level language".
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Of course, I forget this is HN and there are some people who think that it means:
I have never seen "C" and "low level" on the same line of text!
For these unfortunate cases, there is a belief that 40 year old K&R references (...) and some hastily assembled search results will change my reality... but that's a separate issue I'm not interested in.
Those people are definitely free to consider me a liar, the world will keep spinning for the rest of us.
I don't like responding to anecdotes with anecdotes, so rather than reply with a (IMO pointless) "what?! I hear people talk about C as a low-level language far more often than I hear them talk about it as a systems language", I prefer to give something more substantial.
Restricting my hastily assembled search to HN, I easily find comments from within the last few months referring to C as a low-level language ... and yes, as a systems language too.
