Re: Last Call: UTF-16

From: Markus Kuhn (
Date: Mon Aug 16 1999 - 05:40:17 EDT

Paul Keinanen wrote on 1999-08-16 08:54 UTC:
> At 15:34 15.8.1999 -0700, Markus Kuhn wrote:
> > a) it has been long-established practice to use *exclusively* bigendian
> > convention in ISO, ITU, IETF, ECMA, and Internet RFC protocols
> While Internet RFCs are bigendian, it is twisting the truth by claiming that
> the other organisations have a long established practice of bigendianess.
> Look at any bit serial protocols since Baudot (R)TTY, RS-232 and their CCITT
> (currently ITU-T) variants, SDLC, HDLC, X.25 etc. they all transmit the
> least significant bit first.

I was certainly not twisting the truth. You mix up here two
independent problem fields:

  a) the order of bytes within a word
  b) the order of bits within a byte

I was exclusively talking about a). For a), not only Internet RFCs, but
also all ISO/ITU/ECMA standards that I have ever seen use EXCLUSIVELY
the most-significant-byte-first convention (including JPEG, MPEG, JBIG,
ASN.1/BER, all OSI protocols, and many others). The conventions in b) are
none of our business here, because

 - the respective conventions are well established for the
   respective media types (no confusion happens in practice, with
   the ISO 7816-3 (contact smartcards) bit order mess perhaps
   being a potential unfortunate exception)
 - the respective bit-order conventions are handled completely
   invisible to the applications and systems programmer by
   the parallel/serial conversion hardware in the media interface
   adapter and do not interact with the bytes-in-a-word conventions
   that are usually handled on the other side of a byte-addressing
   parallel CPU bus by software

Further information and lots of excellent references on this
(rather old) subject can be found for instance in:


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>

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