Question - internal representation of char in Algol 68

[chris hermansen]

Ok, I found this:

https://gcc.gnu.org/onlinedocs/ga68/POSIX-string-transput.html

where it states:

The following procedures read or write characters and strings from and to
> open files. The external encoding of the files is assumed to be UTF-8.
> Since Algol 68 chars are UCS-4, this means that reading or writing a
> character may involve reading or writing more than one byte, depending on
> the particular Unicode code points involved.


There appears to be some difference between UTF-32 and UCS-4; see this
article

https://stackoverflow.com/questions/30186631/what-is-the-difference-between-utf-32-and-ucs-4

in which comments indicate:

UCS-4 and UTF-32 are now identical except that the UTF-32 standard has
additional Unicode semantics

and

"Additional Unicode semantics" means the extra properties Unicode adds
> above and beyond the code points, such as bidirectionality, collation
> rules, normalization of forms, etc. Some features of Unicode have been
> implemented in software that technically only supports UCS, but those are
> extensions that partly implement Unicode.


So I guess I should ask, is Algol 68 char really UCS-4 or is it rather
UTF-32 and includes those extra semantics?

Not knowing the depth of collation rules, I can imagine there would be
circumstances where we might want to apply collation rules for comparing
two strings and other circumstances where we don't.  I further suppose that
would require two different operators, maybe EQ and COLLATESTO?

On Fri, Jan 9, 2026 at 1:12 PM chris hermansen <clhermansen@gmail.com>
wrote:

> I notice in the online docs here:
>
> https://gcc.gnu.org/onlinedocs/ga68/Standard-modes.html
>
> this information:
>
> Mode: char
>
> Mode for character values. The character values are mapped one-to-one to
> code points in the 21-bit space of Unicode.
>
> To me this implies that char is implemented as UTF-32.  And for some
> reason I think I have read that elsewhere, but I can't put my finger on it.
>
> Please confirm (or not) that mode char is UTF-32!
> --
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
>


-- 
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.
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