Re: TALK: xxdecode

Winston Smith (win...@merk.com) wrote:
: On Wednesday, June 8, 1994 at 07:09:53 GMT  (1:09am EDT ?)
:   pau...@heino.ibh.rwth-aachen.de (Paul Foerster) writes:

:  PF> ... I never heard of xxencode. So let's generate some questions from
:  PF>  scratch:
:  
:      I can think of a very good reason for XXENCODE, namely that the first,
: and fastest hardware on the computer networks are typically IBM mainframes
: which run the EBCDIC character set (a.k.a. translation tables for Hollerith
: punchcard strings).  As a result, files in the big networks are constantly
: "pouring through" EBCDIC IBM mainframes at the large academic and
: industrial sites.


[...Winston Smith's treatise on XX encoding omitted...]

Well I'm not sure about the contents of your treatise but here is 
what Richard Marks, author of the UU/XX Encoder/Decoder 
has to say about  UU and XX encoding systems:

-------------------------------------------------------------------

[ EXTRACT FROM: Richard Marks UUENCODE/DECODE  Documentation File ]

UU-encoding is a way to code a file which may contain any characters 
into a standard character set that can be reliably sent over diverse 
networks.  

Another newer less popular encoding method, called XX-encoding uses 
the set: 

        +-01..89ABC...XYZabc...xyz

In my opinion, XX-encoding is superior to UU-encoding because it 
uses more "normal" characters that are less likely to get corrupted.  
In fact several of the special characters in the UU set do not get 
thru an EBCDIC to ASCII translation correctly.  

Conversely, an advantage of the UU set is that it does not use lower 
case characters.  Now-a-days both upper and lower case are sent with 
no problems; maybe in the communications dark ages, there was a 
problem with lower case.  

A third encode mapping is the one used by Brad Templeton's ABE 
program.  This is not handled by these programs as the check and 
control information surrounding the actual encoded data is in a 
different form.  

[ end of extract ]


*************************************
Q.  What does the acronym XX mean ?
*************************************

"XX" is not an acronym.  It is a name for a variation of the UUencode
program.  I guess the writer just chose the "XX" letters and the name 
stuck.  

The "XX" and "UU" programs are identical except that "UU" maps into 
one set of ASCII characters and "XX" uses another mapping; except 
for the mapping tables, the programs are identical.  The "XX" 
mapping is superior now.  

--------------------------------------------------------------------

Bye,

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