These can only be used to describe and format documents, not to write programs, which is why they are markup languages and not programming languages.
https://stackoverflow.com/questions/2497146/is-css-turing-co...
You can't have any programming language that is more powerful than that. So technically speaking (HTML + CSS) is a "proper programming language". Just a very awkward one where the user has to "operate the crank on the machine" to execute it.
As most human things, programming languages don’t have a specific definition, but as a point of reference we should probably have a look at whether that “thing” was ever intended to be used as that. Sure, there is a program that can encode loops into html tags, but it is generally used as a markup language for describing the DOM. Not for programming it.
> The formal definition (simplest) of Turing Machine is simply a tuple of states set, symbol set, initial state, accepting states set and a transition function. There is no crank in it. By computation we mean somebody needs to apply the transition function faithfully on the tape which is exactly like the clicking in this case. More formally, a model of computation can be viewed as a set of rules somebody needs to follow to do the computation. In that sense, I think CSS is Turing-Complete. – Shuhao Tan Jun 11, 2018 at 21:32
[Emphasis mine]
There is no restriction on the "device" executing a program.¹
Steam devices like in the case of power looms are for example just fine. As the human brain is in case of say abstractly but formally expressed algorithms (think Ada Lovelace).
Also programmable machines that were in fact run by spinning a crank by a human are considered some kind of archaic "computers" (think for example antique mechanical music devices which could "load" a peace form a kind of card or tape).
(HTML + CSS) can be used to formulate executable algorithms to compute anything computable. You can't be more of a programming language than that! Only that the executing device is a little bit awkward as you need in fact "spin a crank" manually.
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¹ For example there was this nice Lego Turing machine:
https://www.youtube.com/watch?v=FTSAiF9AHN4
If I would replace the electrical motors by a hand crank would anything fundamentally change?
No, of course not! The machine would be still a universal computer. Only one that needs to be operated "semi-manually"—exactly like a "computer" build in (HTML + CSS).
I’m still not sure I would call it a programming language. But I wouldn’t say it’s not one.