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From: djb@wjh12.harvard.edu (David J. Birnbaum)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: uuencode vs. xxencode
Message-ID: <519@wjh12.harvard.edu>
Date: 17 Jul 90 19:03:03 GMT
References: <9007171240.AA00322@thep.lu.se> <1990Jul17.160257.24567@murdoch.acc.Virginia.EDU>
Reply-To: djb@wjh12.UUCP (David J. Birnbaum)
Organization: Harvard University, Cambridge MA
Lines: 32

Someone asks:

>What's the difference between uuencode and xxencode, and which encoding
>scheme is the "best" for mailing binaries (i.e. which one produces the smallest
>output files?)

To which someone else replies:

>As I understand it, both uuencode and xxencode do basically the same
>thing:  convert 2 8-bit bytes (i.e. binary data) into 3 6-bit bytes
>(i.e. text).  Therefore, they create the same size output files.  
>I've been told that (somehow) xxencode is superior, but since uuencode
>is much more universally available, uuencode is the method of choice.

The methods have the same results as long as the files must pass only
through systems with identical character mapping.  Unfortunately, there
are several flavors of EBCDIC and substantial differences between
EBCDIC and ASCII, which means that unlike machines try to translate
characters to their own mapping.  The translations are not one-to-one,
which means that characters may be conflated, producing a corrupt file.
Xxencode uses a more restricted character set, limited to characters
that are coded identically in ASCII and all flavors of EBCDIC.  Thus,
xxencoded files can be transferred safely anywhere.  Uuencoded files
are frequently corrupted.

There are a few other encoding systems, including util3, abe/dabe, and
ascify.

--David
==================================================================
David J. Birnbaum                 djb@wjh12.harvard.edu [Internet]
                                  djb@harvunxw.bitnet [Bitnet]