Top Document: Graphics File Formats FAQ (Part 1 of 4): General Graphics Format Questions Previous Document: II. General Graphics File Questions Next Document: V. Graphics Formats Misnomers, Misgivings, and Miscellany See reader questions & answers on this topic! - Help others by sharing your knowledge ------------------------------ ubject: 0. How can I email a graphics file? Normally you would move a file around the Internet using a data transport program that handles binary data, such as UUCP and FTP. If you only have an ASCII-only data transport mechanism available to you, such as electronic mail, you will need to convert your binary graphics files to an ASCII format before sending them. This process is only necessary for binary files. ASCII-based file formats, such as DXF and PostScript, do not require uuencoding before emailing. On the Unix operating system you will use a program called uuencode to convert the 8-bit data of a graphics file to a 7-bit ASCII data file. The data file is then emailed and uudecoded on the receiving end. To uuencode and email a file: % uuencode picture.img picture.img | Mail user@host.site This command will pipe the output of the uuencode command to the input of an email program. Realize that if your email program is set up to keep a copy of all of the email you send, and you email a lot of uuencoded graphics files, your outgoing email folder will grow quite large. You can modify your .mailrc (or equivalent) file to route the copy of the outgoing graphics file to /dev/null, or you can write-protect your outgoing mail folder so the data can't be written: % chmod -w ~/Mail/mbox.out % uuencode picture.img picture.img | Mail user@host.site /home/Mail/mbox.out: Permission denied % chmod +w ~/Mail/mbox.out Once the emailed data is received, you will need to strip off the mailing header before you can uudecode it. The uuencoded data starts with the word "begin" and is followed by the file mode, file name, and a series of 61-character lines. The file is ASCII, so you can use an editor such as vi to do the stripping. Assuming the received data is saved to a file named "file", the uudecoing process is thus: % uudecode file The original graphics file is now in the current directory. You may delete the uuencoded file if you wish to do so. The uuencode and uudecode programs have been ported to other systems, such as MS-DOS, MS Windows, OS/2, Amiga, and the Macintosh (the BinHex program for the Mac does not produce the same ASCII data as uuencode), and may be used in the same way. For more information on accessing the Internet via email, please refer to the FAQ "Accessing The Internet By E-Mail: Doctor Bob's Guide to Offline Internet Access", found on the news.answers and alt.internet.services Usenet newsgroups and your favorite FAQ archives. ------------------------------ ubject: 1. Where can I find graphics files on Usenet? The vast majority of graphics files posted to Usenet will be found in the alt.binaries.pictures.* newgroups. If you do not have access to Usenet, then you will not be able to retrieve files posted to these groups. For much more information on the alt.binaries.pictures.* newsgroups, please consult the alt.binaries.pictures FAQ (pictures-faq/part[1-3]) posted to news.answers and alt.binaries.pictures.d. ------------------------------ ubject: 2. How do I decode a graphics file posted to Usenet? Graphics files are posted to Usenet as uuencoded binaries. Although you may see files posted using BinHex or someother ASCII format, the uuencode data format is the defacto standard of Usenet. A graphics file may be contained in a single-part posting, which you will save to a file, strip off the mailing header using a text editor, and use the uudecode program to convert the data into the original graphics file. Many online news readers will perform this operation for you. Graphics files are usually quite large and uuencoding will increase the file size by another 33%. For this reason, graphics files (and most binary files) are split into 1000 line or 60KB chunks (multi-part postings) for easier handling. If each chunk includes a shell wrapper (the string "[sh]" usually appears in the Subject: line of such postings), online news readers, such as tin, can tag each part of the posting and decode it into the original file for you. The most labor-intensive way to decode a multi-part uuencoded posting is to save each part into a separate file, edit each file to remove the mailing headers, concatenate them all into a single file, uudecode the file, and delete the original parts: % vi picture.1 picture.2 picture.3 % cat picture.1 picture.2 picture.3 | uudecode % rm picture.1 picture.2 picture.3 There are, of course, several utilities to decode single- and multi-part binary posting for you without all this bother. Please refer to the alt.binaries.pictures FAQ (pictures-faq/part[1-3]) posted to news.answers and alt.binaries.pictures.d for more information on decoding graphics files posted to Usenet. ------------------------------ ubject: 3. How can I post a graphics file to Usenet? Posting a graphics file to a Usenet newsgroup is very similar to emailing a graphics file, but there are some important extra steps you must take in order to do so. First, a graphics file must be uuencoded. That is, converted from 8-bit binary data to 7-bit ASCII data. Second, the resulting uuencoded file must be split into 60K chunks (1000 lines) for posting. And lastly, each chunk posted must be given a description and a part number. Under Unix we would use the uuencode, split, expr, and inews commands to post a graphics (or any binary) file as such: % uuencode picture.img picture.img > picture.img.uue % split -1000 picture.img.uue picture.img.uue. % ls Total 535 picture.img picture.img.uue picture.img.uue.1 picture.img.uue.2 picture.img.uue.3 % sh $ i=1 $ for j in picture.img.uue.*; do > (echo "Subject: picture.img [$i/3]" > echo "Newsgroups: news.test > echo > cat $j) | /usr/lib/news/inews > i=`expr "$i" + 1` > done $ rm picture.img.* $ exit % In this example, we take a graphics file named picture.img, uuencode it, and place the output in a file names picture.img.uue. This file is then split into three chunks named picture.img.uue.1, picture.img.uue.2, and picture.img.uue.3. We then loop through each file and create a Subject: and Newsgroup: line for each of the file chunks and post them using inews. There are, of course, programs which automate this process. One such program is xmitBin, written by Jim Howard and availble via FTP from: ftp://ftp.cadence.com/utils http://mrcnext.cso.uiuc.edu/~deej/index.html Refer to the alt.binaries.pictures FAQ (pictures-faq/part[1-3]) posted to news.answers and alt.binaries.pictures.d for more information on posting graphics files to Usenet. ------------------------------ ubject: 4. How do I submit a file format specification to an archive? There are several FTP and WWW sites which act as archives for graphics file format specifications (see the section "Graphics and Image File FTP Archives and WWW Pages"). If you have a file format specification that is legal to share with the rest of the world-wide Internet community, then you may wish to submit it to one or more of these archives. There are generally two ways to submit a file format specification to an FTP archive: 1) Upload (or "put") the file in the /incoming or /pub/incoming directory. 2) Email the file to the archive maintainer (the email address is usually in the README or similar file in the root FTP directory). Realize that most FTP sites don't allow unsolicited uploads and instead require you to contact the archive maintainer to make a submission. Many sites are simply mirrors for other archives and don't accepts any kind of submissions at all. In any case, it's usually good form to include a description file with your submission to describe in a few words what you have uploaded and where it originated. If your upload is named foo.doc then the description file should be named foo.txt. If your upload is named foo.txt, improvise. ------------------------------ ubject: 5. How can I make transparent and interlaced GIFs for a Web page? Transparent GIFs are used to eliminate the typical rectangular borders associated with most bitmapped images that appear on a Web page. The creator of a GIF image may set certain pixels within the bitmap to a color desiganted within the image file as "transparent". When this GIF image is displayed by a Web browser the transparent pixels take on the color of the user's display. This is identical to the blue screen effect found in chromakeying. GIF89a files are made transparent by the use of graphics file editing software (GIF87a files do not support transparency and must first be converted to the GIF89a format). Such software will set the transparency color flag and the transparent color index value of a Graphics Control Extension block within the GIF89a file. Any pixel set to the specified transparent color index value will take on the background color of the display device when displayed. Interlaced GIFs are used to give the user a idea of that an image looks like before all of the bitmapped data has been received. Non-interlaced images paint in a linear fashion from the top to the bottom of the display. Over a slow link it make take several minutes for an image to paint. When 50% of the bitmapped data is received only the top half of the image is displayed. The contents bottom half is still a mystery to the user. Interlaced GIFs paint quickly over the entire display first as a very low resolution image. Only about 12.5% of the bitmap is displayed in this first pass. The GIF image is then repainted in three more passes, with each pass supplying more resolution until all of the data is received (12.5%, 25%, and 50% respectively). A user can usually get a good idea of what the entire image is when only 30-50% of the bitmapped data has been received. This is very useful for knowing when to abort an image being viewd via a slow link. Interlacing is supported by both the GIF87a and GIF89a formats. Graphics file editing software that supports interlaced GIF should not only be able to display such GIF files, but also convert non-interlaced GIFs to the interlaced format (and back again as well). This involves reading in the GIF bitmap and writing it back out using the GIF 4-pass interlace scheme. In a non-interlaced GIF the pixel lines are displayed in consecutive order. For example, the lines of a 16-line non-interlaced GIF file are stored as 0, 1, 2, 3, 4, 5...15. The lines of the same 16-line bitmap in an interlaced GIF would be stored as 0, 8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15. Graphics file format software packages for Unix which handles both trasparent and interlaced GIFs include NETPBM and giftool. For the Macintosh: Transparency, Graphic Converter, Imagery, and clip2gif The Visioneering image manipulation page will allow you to convert your GIFs to transparent and interlaced without having special software on your system. Your GIF files will be read, converted, and written using the Web. Visioneering's page is at: http://www.vrl.com/Imaging/ More detailed information on images used in Web pages can be found in the FAQ for the newsgroup comp.infosystems.www.authoring.images found at: http://www.island.net/help/faq/www_faq/ http://www.io.org/faq/www/index.html A collection of links to a number of Web and FTP resources that store information on transparent and interlaced GIFs for Unix, Macintosh, and MS-DOS/Windows, including executable programs and tutorials, may be found at: http://members.aol.com/htmlguru/transparent_images.html http://dragon.jpl.nasa.gov/~adam/transparent.html ftp://csi.jpl.nasa.gov/pub/graphics/ ------------------------------ ubject: 6. How do I combine still images to make animations? You might have a collection of imaes and drawings stored in a variety of still-image formats (TIFF, BMP, IFF, and so forth) and want to combine them into an animation or video file format that wil allow you to play them back. Have a look at the following Web page: http://www.prism.uvsq.fr/public/wos/multimedia/ ------------------------------ Subject: IV. Copyrights, Patents, and other Legalities of Graphics File Formats ------------------------------ ubject: 0. Can a graphics file be copyrighted? No. A graphics file cannot normally be copyrighted under United States copyright laws (although the rulings of some judges may disagree on this). The specification of a format and the contents of a graphics file, however, are subject to copyright. For anything to be copyrighted it must be: 1) A work of authorship 2) Fixed in a tangible medium of expression The description of a graphics format does meet both of these criteria (it is fixed in a medium and a work of authorship) and is therefore protected under the copyright laws. A graphics file created using the format description, however, meets the second criteria, but not the first (that is, it is not considered to be a work of authorship). The format itself is considered instead to be an idea or system, and is therefore not protected by copyright. So the description of a file format is copyrightable, but the format as it exists in its medium is not. What about the graphics data that the file contains? If the graphical data written to a graphics file also meets the above two criteria, then it is also protected by the copyright laws as intellectual property. You will not wave your copyright protection by storing any original information using a graphics file format. For more information on copyright, please refer to the Copyright FAQ found on the misc.legal, misc.legal.computing, misc.int-property, and comp.patents newsgroups: ftp://rtfm.mit.edu/pub/usenet/news.answers/law/Copyright-FAQ/ ftp://rtfm.mit.edu/pub/usenet/news.answers/law/Copyright-FAQ/myths/ Apparently, quite a number of copyright discussions also occur on the comp.infosystems.www.* newsgroups as well. Information on patents, copyrights, and intellectual property may be found at: http://www.questel.orbit.com/patents/readings.html Patent and trademark information http://www.uspto.gov U.S. Patent and Trademark Office http://www.spi.org Software Patent Institute ------------------------------ ubject: 1. Is it now illegal to use CompuServe's GIF format? It is not illegal to own, transmit, or receive GIF files (provided that no unlicensed compression and/or decompression of the files occurs). You must realize, however, that GIF files are not the issue. The issue is, in fact, the LZW data compression algorithm. In 1984, while working for Sperry Corporation, Terry Welch modified the Lempel-Ziv 78 (LZ78) compression algorithm for greater efficiency for implementation in high-performance disk controllers. The result was the LZW algorithm. The world was informed of the existence of LZW by the following journal article, published by Mr. Welch after he left the employment of Sperry: Welch, T. A., "A Technique for High Performance Data Compression," IEEE Computer, Volume 17, Number 6, June 1984. In 1985, Sperry Corporation was granted a patent (4,558,302) for the Welch invention and implementation of the LZW data compression algorithm. Since that time, this LZW patent has been publicly available for all to see in the US Patent Office and many public libraries, and is available through many on-line services. In 1987, CompuServe Corporation created the GIF (Graphical Interchange Format) file format to be used for the storage and on-line retrieval of bitmapped graphical data. The GIF specification required the use the LZW algorithm to compress the data stored in each GIF file. It is very possible that CompuServe did not check the patent files to determine whether the GIF format infringed on any patents. Such a check would have found the Welch LZW patent, which was then owned by Unisys as a result of their having purchased Sperry in 1986. At that time, Unisys also did not know that LZW was the method of compression used by the very popular GIF file format. In 1988, Aldus Corporation released Revision 5 the TIFF file format. This revision added a new feature giving TIFF the ability to store RGB bitmapped data using either a raw format, or a compressed format using the LZW algorithm. (Although the LZW algorithm used by TIFF is considered to be "broken", it is still covered by the Unisys patent). Since 1991, in accordance with their agreement with Unisys, Aldus has been required to place a notice regarding the Unisys patent and its applicability to TIFF, in Aldus documentation. The 1992 release of Revision 6 of the TIFF specification includes this notice of the Unisys patent regarding LZW. The TIFF Revision 6 specification also recommends against using LZW to compress RGB bitmaps stored using the TIFF format. In 1990, Unisys licensed Adobe for the use of the Unisys LZW patent for PostScript. In 1991, Unisys licensed Aldus for the use of the Unisys LZW patent in TIFF. In 1994, Unisys and CompuServe came to an understanding whereby the use of the LZW algorithm would be licensed for the application of the GIF file format in software. In 1995, America Online Services and Prodigy Services Company also entered license agreements with Unisys for the utilization of LZW. Published information indicates that Unisys' licensing policies are as follows: 1) Unisys considers all software created or modified before January 1, 1995 that supports the GIF and/or TIFF-LZW formats to be inadvertently infringing upon its patent; Unisys will therefore not require a license for GIF software products delivered before January 1, 1995. Unisys will therefore not pursue legal actions against such pre-1995 software products. 2) However, Unisys expects developers of commercial or for-profit software to obtain a GIF-LZW license agreement from Unisys if, after December 31, 1994, the developer creates new software or updates or modifies existing software, or issues a new release of software that supports the GIF file format. 3) Unisys does not require licensing of non-commercial, not-for-profit software applications that support the GIF file format. 4) With respect to TIFF, if a license is entered before July 1, 1995, there will be no liability for pre-1995 software with respect to that software's support of TIFF which uses LZW. Unisys has drafted licenses for several different applications of the LZW algorithm. The two license agreements of most interest in this FAQ are applicable to software supporting the GIF file format alone and the agreement applicable to software supporting both GIF and the TIFF file format's LZW compression feature. Realizing that you have many questions about GIF-LZW and TIFF-LZW licensing, the remainder of this section is arranged in a Question/Answer format to help convey information about this subject more clearly. Q: Just what is this all about? A: Unisys has asserted its claim to the ownership of the LZW compression and decompression algorithm. If you wish to implement LZW in a software or firmware application, you must arrange to pay a small royalty to Unisys for every software package that you sell. You do this by applying to Unisys for an LZW license agreement for your software. Q: What file formats are effected? A: GIF, TIFF, PDF, and PostScript Level II. All of these formats use, or can use, LZW compression. For example, a TIFF or PostScript Level II file may or may not use the LZW algorithm to compress the data it contains. GIF files, and most PDF files, always store bitmap data that is compressed using LZW. Q: How does this agreement affect my use of GIF and TIFF files? A: It does not affect the ownership, transmission, or reception of GIF and TIFF-LZW files themselves. Only the software that performs compression and/or decompression of GIF may be effected in any way by license agreements. You are free to store and transport GIF and TIFF-LZW files without fear of legalities or cost from the Unisys licenses provided that any compression and/or decompression on GIF files is performed by licensed software, or by software products delivered prior to 1995. Q: Which agreement do I need? A: If your software supports only GIF then you need the GIF-LZW agreement. If it supports TIFF-LZW or both GIF and TIFF-LZW then you need the TIFF-LZW and GIF-LZW agreement. Q: My software supports TIFF-LZW, but not GIF. A: You still need to obtain the TIFF-LZW and GIF-LZW agreement. Q: So if my software only supports non-LZW versions of TIFF and PostScript Level II I don't need to worry about obtaining a license agreement? A: That is correct. Only software that is capable of using the LZW algorithm requires an agreement. This includes all software that supports the GIF file format. Q: What about file compression programs such as compress, PKZIP, zoo, and lha? Don't they use LZW too? A: Most file compression programs use the LZ77 algorithm for compressing text. The LZ77 compression algorithms (and several of its derivatives) predates LZW by several years and is covered by its own series of patents. The predecessor to LZW, LZ78, is used primarily for compressing binary data and bitmaps. Any software that uses the LZ77 and/or LZ78 algorithms without the LZW improvement is not affected by the Unisys LZW patent. Of the mentioned software packages, the Unix compress utility does use LZW and therefore requires a license. Q: Doesn't IBM also hold a patent on LZW? A: IBM was granted a patent (4,814,746) for use of LZW in disk drive technology. This patent does not award ownership of LZW to IBM. Q: Is there a chance that the Unisys patent is actually invalid? A: In 1994, the U.S Patent Office reexamined the Welch patent and, on January 4th of that year, not only confirmed the patentability of the original 181 patent claims, but also confirmed that 51 claims added during the reexamination were also patentable. Q: I have heard that the Welch patent only covers LZW compression and not decompression. Is this true? A: Many people who have read the patent claim that this is true. Unisys, of course, strongly maintains that the patent does cover LZW decompression, and will pursue legal action against unlicensed software which only performs LZW decompression. It is not clear (to the author of this text) if the 1994 patent reexamination specifically asserted the existence of the description of LZW decompression in the original Welch patent. Q: But you can't patent a mathematical abstraction. Doesn't this also include algorithms implemented as computer software? A: A patent grants the exclusive rights, title, or license to produce, use, or sell an invention or process. One or more algorithms may be applied using software to create an invention. It is this invention whose use is restricted by the patent and not the algorithm(s) involved. In the case of software, it seems that it is not very easy to separate the algorithm(s) from the invention itself. Use of the algorithm(s) would seem to imply use of the invention as well. Q: I use LZW in my programs, but not for GIF or TIFF graphics. What should I do? A: If you are not a business, and the programs are for your own personal non-commercial or not-for-profit use, Unisys does not require you to obtain a license. If they are used as part of a business and/or you sell the programs for commercial or for-profit purposes, then you must contact the Welch Patent Licensing Department at Unisys and explain your circumstances. They will have a license agreement for your application of their LZW algorithm. Q: Where can I apply for a GIF-LZW, TIFF-LZW and GIF-LZW, PDF, PostScript Level II, or any other LZW license? A: You can write to: Welch Patent Licensing Department Unisys Corporation Mail Stop C1SW19 P.O. Box 500 Blue Bell, PA 19424 USA Or fax: 215.986.3090 Or email: lzw_info@unisys.com General licensing information may also be obtained from the home page of the Unisys Web Server: http://www.unisys.com/ http://www.unisys.com/ServerInformation/contact/contact.html http://www.unisys.com/LeadStory/lzwfaq.html Q: How much does a license cost? A: The terms and cost of the license policy has changed since its introduction in 1995. Contact Unisys for the latest LZW licensing terms. Q: Do I need a separate license for each GIF-using software product I sell? A: If you sell three products that all use the GIF format, for example, then you will need only one license. License fees must be paid for each product sold. Q: Do I need to obtain a new license if I release a new version of my software? A: No. However, a license fee is required for each update, improvement, or enhancement of your software that is sold. Q: What if I give my software away? A: If you distribute for free your product directly to end-users for their personal use and your distributing the software is non-commercial and not-for-profit use and you receive no financial gain (such as Shareware donations, royalties for CD-ROM distributions, or as advertising to attract for-profit business), then you do not need a license. Q: But what about Shareware donations? A: Each Shareware "payment" you receive is considered the selling price of that unit. Whatever a user pays to you for your GIF-using software is required to be included in your quarterly license fee payment to Unisys. However, minimum license fees per unit must be always paid. Q: My Shareware GIF software is being sold for-profit on a CD-ROM, but I do not make any profit from its sale. Can I get in trouble? Do I need a license? A: The person/business that is selling your program for profit on their CD-ROM is responsible for obtaining the proper license. You would only need a license if you received any payments from the CD-ROM vendor or from users of your Shareware. Q: I do not live in the United States and my software is not available there. Do I still need to obtain a license agreement? A: Yes, you do. The Unisys patent has many foreign counterparts and the legalities of using LZW apply to most other countries in addition the US. Q: What will happen to me if I continue to revise my GIF-using software, sell it for profit, and yet not bother to obtain a license? A: Most likely, when your unlicensed program is discovered by Unisys, you will be notified of your need to obtain a license for your product. If you then fail to obtain the proper license, Unisys may seek an injunction against your product including damages. You could also be charged with willful infringement, which could result in treble damages. Q: On what Usenet newsgroups is this LZW agreement being discussed? A: You will find threads appearing on comp.graphics.misc and other related graphical newsgroups. The official newsgroup where much discussion takes place is alt.gif-agreement. You might also find information on the misc.legal.computing, misc.int-property, and comp.patents newsgroups. Q: Where can I get a copy of the Unisys patent? A: Copies of patents may be found in public libraries or be obtained directly from the U.S. Patent Office. The patent is also available at many Internet sites, including: ftp://ftp.std.com/obi/USPatents/ ftp://ftp.uu.net/doc/literary/obi/USPatents/lzw-patent.Z Q: What are my alternatives to GIF and TIFF-LZW file formats? A: A good alternative to LZW for compressing ASCII data is the LZ77 algorithm used by the zip and PKZIP file archivers and the gzip (GNU zip) file compression program. The most popular alternative for multi-bit image data is the JPEG compression algorithm and the JFIF and SPIFF file formats. JFIF and SPIFF-JPEG files are smaller and store far more colors than GIF files. Another newer alternative is the PNG format, which is currently under development (see the section "PNG - Portable Network Graphics" in Part 3 of this FAQ). PNG is unencumbered by patent licenses and has much potential and promise in replacing GIF. But, most software that supports PNG will likely have been written after January 1, 1995, so make sure that your GIF-to-PNG conversion program has the proper Unisys license. Q: Will Unisys' actions hurt the use of GIF? A: Yes it will. People will continue to write software that supports GIF only if their customers demand it. The licensing will hasten the eventual demise of GIF, as both people and companies will be more motivated to standardize on "free" formats, such as JFIF, SPIFF, PNG, BMP, and TGA. Q: This agreement is bogus! I refuse to ever use GIF again! A: As an end-user you are free never to read, write, or archive another LZW-encoded file as long as you live. As a developer you are only free of the legal implications of the Unisys patent if you remove any LZW code from your programs, including those shipped to your customers after 1994. Q: Wait! I have more questions! A: Contact the Welch Patent Licensing Department at the aforementioned addresses. I (the author of this FAQ) am not an employee nor legal representative of Unisys. You can also find this information on the Unisys web page: http://www.unisys.com/LeadStory/lzwfaq.html And in the following InfoWorld article: "Graphics file format patent Unisys seeks royalties from GIF developers", Karen Rodriguez, InfoWorld, Jan 09, 1995 (Vol.17, Issue 02, p3) And the following Web pages are devoted to this issue: http://www.lpf.org/Patents/Gif/unisys.html http://www.lpf.org/Patents/Gif/Gif.html http://www-cmpo.mit.edu/met_links/resources/LZW_patent.html http://www.webhaven.com/izivkov/scanfax/GIF.HTM http://rom.oit.gatech.edu/~willday/gif.html Disclaimer: The information in this FAQ regarding the Unisys LZW licensing agreement has been presented in an attempt to allow the reader to understand some of the legalities they may face by the use of the LZW algorithm. The author has rendered this explanation and example questions using the most accurate information available to him at the date of this FAQ. In no regard should this text be considered an official publication of Unisys Corporation or a legal representation of the policies of Unisys, or in any way obligating Unisys to enter into a license agreement based upon the terms, interpretations, and/or answers to question provided in this text. User Contributions:Top Document: Graphics File Formats FAQ (Part 1 of 4): General Graphics Format Questions Previous Document: II. General Graphics File Questions Next Document: V. Graphics Formats Misnomers, Misgivings, and Miscellany Part1 - Part2 - Part3 - Part4 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jdm@ora.com (James D. Murray)
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