Xref: utzoo comp.sources.d:2067 comp.binaries.ibm.pc.d:187
Path: utzoo!mnetor!uunet!pcrat!rick
From: rick@pcrat.UUCP (Rick Richardson)
Newsgroups: comp.sources.d,comp.binaries.ibm.pc.d
Subject: Re: Standard for file transmission
Message-ID: <497@pcrat.UUCP>
Date: 10 May 88 13:09:07 GMT
References: <292@cullsj.UUCP> <55@psuhcx.psu.edu> <537@csccat.UUCP> <679@omen.UUCP>
Reply-To: rick@pcrat.UUCP (Rick Richardson)
Organization: PC Research, Inc., Tinton Falls, NJ
Lines: 32
Keywords: protocol compression source

In article <679@omen.UUCP> caf@omen.UUCP (Chuck Forsberg WA7KGX) writes:
>Again, please post the ARITH program.  It would be most interesting
>if the memory requirements are small - like Huffman encoding instead
>of LZW.

In case ARITH never gets posted:  the complete article and program appeared
in ACM last year, in C.  I typed it in myself (and lost it later).  The
program, as published, runs a lot slower than compress and does not do
quite as good a job as compress.  It was better than "pack".  It is
very small, and uses little memory.

If you dig into the article (this from memory, I seem to have misplaced
the issue of ACM as well), the program separates the algorithm for
encoding into a model.   Two models are presented, one that just
uses a static letter frequency table (for text), and an adaptive model (for
binaries).  As I recall, the author pointed out that more sophisticated
adaptive algorithms could be used for better results.

After monkeying around with the program for an evening, and even trying
my own hand at a more sophisticated model, I shelved the program, with
nary a backup.  Since it was slower and less efficient than compress,
I think its usefullness is limited to those applications which are
sensitive to both program and data size, such as in a modem.

BTW, I heard some rumor that a 16 bit "uncompress"-only is available
for limited memory systems.  If this is true, then why all the fuss
about 16 bit compression?
-- 
		Rick Richardson, President, PC Research, Inc.

(201) 542-3734 (voice, nights)   OR     (201) 834-1378 (voice, days)
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