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) uunet!pcrat!rick (UUCP) rick%pcrat.uucp@uunet.uu.net (INTERNET)