Newsgroups: comp.lang.apl
Path: watmath!watserv2.uwaterloo.ca!watserv1!AGRTQB@IRMFAO01.BITNET
From: agrtqb%irmfao01.bitnet@utcs.utoronto.ca
Subject:      XXencode/decode
Message-ID: <920914.122517.ITA.AGRTQB@IRMFAO01>
X-Acknowledge-To: <AGRTQB@IRMFAO01>
Sender: root@watserv1.uwaterloo.ca
Organization: Food and Agriculture Organization of the UN
Date: Mon, 14 Sep 1992 12:25:17 GMT


Note on the XXencode/decode process.

When I did send the directory of APLers I did ZIP the ASCII file and
then XXencoded it.

Many people told me that they did not know about the xxencoding system so
I thought I should post a brief explanation.

The traditional process for transfer of non ASCII files is the
UUENCODE/UUDECODE system. I will not describe the system but the
important point here is that the coding is done using the 64 characters
ASCII 32 to 95.

As some of the characters (mainly the square brackets, caret and stile)
do no always pass properly (in general when the file passes through an
... machine :-) ) a new system has been proposed, the XXENCODE/DECODE.

At present the lower case characters pass without problem so the new
encoding uses:

+-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz

The rest of the process (breaking the bytes, grouping, ...) is the same
as for uuencode/decode. So a global replace (on the coded part of the
XXencoded file) of the above codes by the ASCII 32 to 95 should give a
UUencoded file. This global replace is of course very simple to program
in APL as well as the whole XXencoding/decoding process.

A good introduction can be found in:

A SHORT INTRODUCTION TO NETWORKING AND FILE TRANSMISSION
by Erich Neuwirth

(file TRANSGID.TXT in <MSDOS.STARTER> directory available by anonymous
ftp from SIMTEL20 or TRICKLE).

Yours,

Alain Delmotte     Agrometeorology / FAO         or   Avenue du Marathon, 6
                   Via delle Terme di Caracalla       B1348 Louvain-la-Neuve
                   I00100 Rome ITALY                  BELGIUM
                   tel.: Italy-6-5797 5504            Belgium-10-45 11 92

PS. The directory is available for anonymous ftp as:

ADDRESS.ZOO      directory languages/apl     at watserv1.uwaterloo.ca
or
ADDRESS.Z        directory pub/apl/apl-email at astrpi.difi.unipi.
