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Why does the compiler understand ASCII by default?
(piefed.blahaj.zone)
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this post was submitted on 07 Jun 2026
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C Programming Language
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LOL (please excuse my early 2000's slang)
Thanks for that clarification.
What I still don't quite understand is, does this mean that there is no "checking against an ASCII table" or "lookup" going on? But how then does it know that 0x18 is CAN (disregard)?
Imagine you want to cypher a text, you can have a table with a column with the char you really want to be the meaning and another column with the obscured representation, what you write is the obscured thing, but when you read you take out that table to translate to the original meaning. Computers do sort of the same thing with the translation from bits to letters. But there are many tables, it depends on the languages to read and write.
@akunohana The compiler doesn't need to know that 0x18 is CAN; that knowledge is embedded in whatever decided that the data you're inspecting is UTF-8 or ASCII.
The content of your original post has been replaced with a link that I can't open so I can't go back and confirm where you said the data was coming from. But if the data was some other exotic encoding then 0x18 would mean something else in the context of that data.
Oh, maybe I messed something up when editing... Here's what I wrote:
What it "that thing" that decided the encoding?
@akunohana OK that's a pretty good question then. In that case the encoding is determined by your terminal (or if not terminal then execution environment). Try invoking
env(orlocale) and looking at LANG and LC_ALL; those should tell you what your terminal accepts as input and passes along to your program.Sweet! I think this is the answer that I was looking for, although my post is poorly phrased. 😅
Does this mean that in theory, there could arise problems with portability? 98-ish percent of all systems use Unicode, but if I were to run my program on an obscure system whose underlying character encoding is not Unicode or some superset of ASCII, I assume it would return other values?
@akunohana Yes! Although I would say that ASCII is a pretty safe assumption and it’s really anything above the top of ASCII that you need to account for (document as a requirement for your program, or take steps to ensure the OS uses the right encoding if you are packaging something for distribution)