[codetrotter]

But these numeric values are also ASCII representation of numbers, rather than being the actual byte that is written to the output. Maybe there is hope still. Where do the byte values for those numbers come from when the compiler writes output?

[wahern]

The C standard (see C23 5.2.1p3) requires the values of '0' through '9' to be contiguous, so it doesn't matter if you only care about round-tripping. '7' - '0' == 7 no matter the character set. Though, for round-tripping I suppose this isn't strictly necessary, but it certainly makes parsing and printing decimal notation very convenient. Notably, for both ASCII and EBCDIC 'A'..'F' and 'a'..'f' are also contiguous, so parsing and printing hexadecimal can be done much the same as decimal.

[nialv7]

Maybe the assembler?