On Mon, 28 Oct 1991 17:07:37 -0500 (EST), Nathaniel Borenstein wrote:
In case other people didn't notice it, Mark's latest message contained
what I assume to be a deliberately provocative header:
Content-type: TEXT/ISO-2022; charset=US-ASCII
I shudder to think at how any software SHOULD interpret this. Mine
didn't fare TOO badly, since it really only understands ASCII to begin
with...
Presumably this is not really a provocation, since the charset subtypes
will go away if we move to the charset= syntax. -- Nathaniel
Actually, it's an attempt by an ISO-2022 capable (but text-only) mailer (MS)
to express what it does in a meaningful way. I just happened to use that
mailer to send that message instead of my more usual window-based mailer.
Remember, ISO-2022 is not a character set, it is a means of representing
character set shifts.
This mailer accepts ISO-2022 input from the user. This could be pure ASCII,
or it could have ISO-2022 sequences that shift into JIS. There is no way the
lower level can know, unless it actually examined the text. Actually, it is
perfectly valid ISO-2022 even if there are no shift sequences in the message!
So, it punts and says everything is ISO-2022.
The basic character set is US-ASCII, hence the charset attribute. However, it
*might* have ISO-2022 shift codes, hence the ISO-2022 subtype.