[pdftex] PdfTeX - letter é catcode def

[Karl Berry]

Vincent - I'm not sure if you saw Thierry's answer
(https://tug.org/pipermail/pdftex/2021-December/009244.html).
(Thierry - please cc the original poster on replies to all tug mailing
lists.) It seems sensible to me, except E9 is the Unicode code point for
e-acute.

pdftex simply reads bytes, having been written long before UTF-8 became
pervasive. LaTeX will read UTF-8 input by default these days and map it
to the font slots as needed (defined). Plain TeX is not going to do
that; it's up to you to define it to output to the correct location.

In genera, you can't play around with Unicode code points in pdftex as
if they were characters (\lccode, \lowercase). LuaTeX and XeTeX read
UTF-8 natively so behave differently.

Good luck,
Karl