Xref: utzoo comp.binaries.ibm.pc.d:108 comp.sources.d:2025 Path: utzoo!mnetor!uunet!epiwrl!epimass!jbuck From: jbuck@epimass.EPI.COM (Joe Buck) Newsgroups: comp.binaries.ibm.pc.d,comp.sources.d Subject: Re: Standard for file transmission Message-ID: <2096@epimass.EPI.COM> Date: 5 May 88 16:30:24 GMT References: <299@cullsj.UUCP> Reply-To: jbuck@epimass.EPI.COM (Joe Buck) Organization: Entropic Processing, Inc., Cupertino, CA Lines: 34 Keywords: compression, archive, UUCP In article <299@cullsj.UUCP> jeff@cullsj.UUCP (Jeffrey C. Fried) writes: > > I stand corrected. Since Lem-Ziv was DESIGNED for text compression, and >the authors do not mention its use for binaries, i never considered using it. >I tried it on an executable under UNIX and obtained a good reduction, for >reasons which are not apparent. I'm sure that there are cases where this does >not work (like graphics files), but it does appear to work , and in this case >better than the current version of ARITH. Jeff, Jeff, Jeff. You're STILL putting your foot in your mouth. :-) A Unix file is just a stream of bytes, and so is an MS-DOS file except that it has extra attributes as well. Compress replaces byte strings with codes whose lengths are between 9 and 16 bits. It will work well on any file in which some byte sequences are more common than others. An executable file consists of instructions, which, for almost all processors are integral numbers of bytes, and some are much more common than others. So compress works fine, and will give good compression for just about any executable file. There are several types of graphics files: bitmaps are HIGHLY compressible; other types of files act like a program for an imaginary computer and consist of byte codes, some much more common than others. These compress well also. There are only three types of files I've ever given to compress that haven't been reduced in size as a result: random binary data, floating point binary data, and files that have already been compressed. -- - Joe Buck {uunet,ucbvax,sun,}!epimass.epi.com!jbuck Old Internet mailers: jbuck%epimass.epi.com@uunet.uu.net Argue for your limitations and you get to keep them. -- Richard Bach