Re: My Querry

From: Philippe Verdy (
Date: Tue Nov 23 2004 - 14:58:40 CST

  • Next message: Mike Ayers: "RE: My Querry"

    From: "Antoine Leca" <>
    > I do not know what does mean "fully compatible" in such a context. For
    > example, ASCII as designed allowed (please note I did not write "was
    > designed to allow") the use of the 8th bit as parity bit when transmitted
    > as
    > octet on a telecommunication line; I doubt such use is compatible with
    > UTF-8.

    The parity bit is not data; it's a framing bit used for transport/link
    purpose only.

    ASCII is 7 bit only, so even if a parity bit is added (parity bit can be
    added as well to 8-bit quantities...), it won't be part of the effective
    data, because once the transport unit is received and checked, it has to be
    cleared (so an '@' character will effectively be equal to 64 in ASCII, not
    to 192 if a even parity bit is added.)

    By saying UTF-8 is fully compatible with ASCII, it says that any ASCII-only
    encoded file needs no reencoding of its bytes to make it UTF-8.

    Note that this is only true for the US version of ASCII (well, "ASCII" is
    normally designating only the last standard US variant of ISO 646, other
    standard national variants or proprietary variants of ISO 646 should not be
    named ASCII, but more accurately, for example, "ISO 646-FR:1989", or without
    the ISO prefix if this is a proprietary charset and not an approved charset
    published in the ISO 646 standard).

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