AFNI file: README.bzip2

The following is the README, man page, and LICENSE files for the bzip2 utility, which is included in the AFNI package. The home page for bzip2 is http://www.muraroa.demon.co.uk/ , where the entire bzip2 distribution can be found. This program is included to allow compressed dataset .BRIK files to be used with AFNI. See the file README.compression for more information. Note that bzip2 usually compresses more than gzip or compress, but is much slower. ========================================================================= GREETINGS! This is the README for bzip2, my block-sorting file compressor, version 0.1. bzip2 is distributed under the GNU General Public License version 2; for details, see the file LICENSE. Pointers to the algorithms used are in ALGORITHMS. Instructions for use are in bzip2.1.preformatted. Please read all of this file carefully. HOW TO BUILD -- for UNIX: Type `make'. (tough, huh? :-) This creates binaries "bzip2", and "bunzip2", which is a symbolic link to "bzip2". It also runs four compress-decompress tests to make sure things are working properly. If all goes well, you should be up & running. Please be sure to read the output from `make' just to be sure that the tests went ok. To install bzip2 properly: -- Copy the binary "bzip2" to a publicly visible place, possibly /usr/bin, /usr/common/bin or /usr/local/bin. -- In that directory, make "bunzip2" be a symbolic link to "bzip2". -- Copy the manual page, bzip2.1, to the relevant place. Probably the right place is /usr/man/man1/. -- for Windows 95 and NT: For a start, do you *really* want to recompile bzip2? The standard distribution includes a pre-compiled version for Windows 95 and NT, `bzip2.exe'. This executable was created with Jacob Navia's excellent port to Win32 of Chris Fraser & David Hanson's excellent ANSI C compiler, "lcc". You can get to it at the pages of the CS department of Princeton University, www.cs.princeton.edu. I have not tried to compile this version of bzip2 with a commercial C compiler such as MS Visual C, as I don't have one available. Note that lcc is designed primarily to be portable and fast. Code quality is a secondary aim, so bzip2.exe runs perhaps 40% slower than it could if compiled with a good optimising compiler. I compiled a previous version of bzip (0.21) with Borland C 5.0, which worked fine, and with MS VC++ 2.0, which didn't. Here is an comment from the README for bzip-0.21. MS VC++ 2.0's optimising compiler has a bug which, at maximum optimisation, gives an executable which produces garbage compressed files. Proceed with caution. I do not know whether or not this happens with later versions of VC++. Edit the defines starting at line 86 of bzip.c to select your platform/compiler combination, and then compile. Then check that the resulting executable (assumed to be called bzip.exe) works correctly, using the SELFTEST.BAT file. Bearing in mind the previous paragraph, the self-test is important. Note that the defines which bzip-0.21 had, to support compilation with VC 2.0 and BC 5.0, are gone. Windows is not my preferred operating system, and I am, for the moment, content with the modestly fast executable created by lcc-win32. A manual page is supplied, unformatted (bzip2.1), preformatted (bzip2.1.preformatted), and preformatted and sanitised for MS-DOS (bzip2.txt). COMPILATION NOTES bzip2 should work on any 32 or 64-bit machine. It is known to work [meaning: it has compiled and passed self-tests] on the following platform-os combinations: Intel i386/i486 running Linux 2.0.21 Sun Sparcs (various) running SunOS 4.1.4 and Solaris 2.5 Intel i386/i486 running Windows 95 and NT DEC Alpha running Digital Unix 4.0 Following the release of bzip-0.21, many people mailed me from around the world to say they had made it work on all sorts of weird and wonderful machines. Chances are, if you have a reasonable ANSI C compiler and a 32-bit machine, you can get it to work. The #defines starting at around line 82 of bzip2.c supply some degree of platform-independance. If you configure bzip2 for some new far-out platform which is not covered by the existing definitions, please send me the relevant definitions. I recommend GNU C for compilation. The code is standard ANSI C, except for the Unix-specific file handling, so any ANSI C compiler should work. Note however that the many routines marked INLINE should be inlined by your compiler, else performance will be very poor. Asking your compiler to unroll loops gives some small improvement too; for gcc, the relevant flag is -funroll-loops. On a 386/486 machines, I'd recommend giving gcc the -fomit-frame-pointer flag; this liberates another register for allocation, which measurably improves performance. I used the abovementioned lcc compiler to develop bzip2. I would highly recommend this compiler for day-to-day development; it is fast, reliable, lightweight, has an excellent profiler, and is generally excellent. And it's fun to retarget, if you're into that kind of thing. If you compile bzip2 on a new platform or with a new compiler, please be sure to run the four compress-decompress tests, either using the Makefile, or with the test.bat (MSDOS) or test.cmd (OS/2) files. Some compilers have been seen to introduce subtle bugs when optimising, so this check is important. Ideally you should then go on to test bzip2 on a file several megabytes or even tens of megabytes long, just to be 110% sure. ``Professional programmers are paranoid programmers.'' (anon). VALIDATION Correct operation, in the sense that a compressed file can always be decompressed to reproduce the original, is obviously of paramount importance. To validate bzip2, I used a modified version of Mark Nelson's churn program. Churn is an automated test driver which recursively traverses a directory structure, using bzip2 to compress and then decompress each file it encounters, and checking that the decompressed data is the same as the original. As test material, I used several runs over several filesystems of differing sizes. One set of tests was done on my base Linux filesystem, 410 megabytes in 23,000 files. There were several runs over this filesystem, in various configurations designed to break bzip2. That filesystem also contained some specially constructed test files designed to exercise boundary cases in the code. This included files of zero length, various long, highly repetitive files, and some files which generate blocks with all values the same. The other set of tests was done just with the "normal" configuration, but on a much larger quantity of data. Tests are: Linux FS, 410M, 23000 files As above, with --repetitive-fast As above, with -1 Low level disk image of a disk containing Windows NT4.0; 420M in a single huge file Linux distribution, incl Slackware, all GNU sources. 1900M in 2300 files. Approx ~100M compiler sources and related programming tools, running under Purify. About 500M of data in 120 files of around 4 M each. This is raw data from a biomagnetometer (SQUID-based thing). Overall, total volume of test data is about 3300 megabytes in 25000 files. The distribution does four tests after building bzip. These tests include test decompressions of pre-supplied compressed files, so they not only test that bzip works correctly on the machine it was built on, but can also decompress files compressed on a different machine. This guards against unforeseen interoperability problems. Please read and be aware of the following: WARNING: This program (attempts to) compress data by performing several non-trivial transformations on it. Unless you are 100% familiar with *all* the algorithms contained herein, and with the consequences of modifying them, you should NOT meddle with the compression or decompression machinery. Incorrect changes can and very likely *will* lead to disastrous loss of data. DISCLAIMER: I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE USE OF THIS PROGRAM, HOWSOEVER CAUSED. Every compression of a file implies an assumption that the compressed file can be decompressed to reproduce the original. Great efforts in design, coding and testing have been made to ensure that this program works correctly. However, the complexity of the algorithms, and, in particular, the presence of various special cases in the code which occur with very low but non-zero probability make it impossible to rule out the possibility of bugs remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER SMALL, THAT THE DATA WILL NOT BE RECOVERABLE. That is not to say this program is inherently unreliable. Indeed, I very much hope the opposite is true. bzip2 has been carefully constructed and extensively tested. PATENTS: To the best of my knowledge, bzip2 does not use any patented algorithms. However, I do not have the resources available to carry out a full patent search. Therefore I cannot give any guarantee of the above statement. End of legalities. I hope you find bzip2 useful. Feel free to contact me at jseward@acm.org if you have any suggestions or queries. Many people mailed me with comments, suggestions and patches after the releases of 0.15 and 0.21, and the changes in bzip2 are largely a result of this feedback. I thank you for your comments. Julian Seward Manchester, UK 18 July 1996 (version 0.15) 25 August 1996 (version 0.21) Guildford, Surrey, UK 7 August 1997 (bzip2, version 0.1) 29 August 1997 (bzip2, version 0.1pl2) ======================================================================= bzip2(1) bzip2(1) NNAAMMEE bzip2 - a block-sorting file compressor, v0.1 SSYYNNOOPPSSIISS bzip2 [ -cdfkstvVL123456789 ] [ filenames ... ] DDEESSCCRRIIPPTTIIOONN Bzip2 compresses files using the Burrows-Wheeler block- sorting text compression algorithm, and Huffman coding. Compression is generally considerably better than that achieved by more conventional LZ77/LZ78-based compressors, and approaches the performance of the PPM family of sta- tistical compressors. The command-line options are deliberately very similar to those of GNU Gzip, but they are not identical. Bzip2 expects a list of file names to accompany the com- mand-line flags. Each file is replaced by a compressed version of itself, with the name "originalname.bz2". Each compressed file has the same modification date and permissions as the corresponding original, so that these properties can be correctly restored at decompression time. File name handling is naive in the sense that there is no mechanism for preserving original file names, per- missions and dates in filesystems which lack these con- cepts, or have serious file name length restrictions, such as MS-DOS. Bzip2 and bunzip2 will not overwrite existing files; if you want this to happen, you should delete them first. If no file names are specified, bzip2 compresses from standard input to standard output. In this case, bzip2 will decline to write compressed output to a terminal, as this would be entirely incomprehensible and therefore pointless. Bunzip2 (or bzip2 -d ) decompresses and restores all spec- ified files whose names end in ".bz2". Files without this suffix are ignored. Again, supplying no filenames causes decompression from standard input to standard output. You can also compress or decompress files to the standard output by giving the -c flag. You can decompress multiple files like this, but you may only compress a single file this way, since it would otherwise be difficult to sepa- rate out the compressed representations of the original files. Compression is always performed, even if the compressed file is slightly larger than the original. Files of less than about one hundred bytes tend to get larger, since the compression mechanism has a constant overhead in the region of 50 bytes. Random data (including the output of most file compressors) is coded at about 8.05 bits per byte, giving an expansion of around 0.5%. As a self-check for your protection, bzip2 uses 32-bit CRCs to make sure that the decompressed version of a file is identical to the original. This guards against corrup- tion of the compressed data, and against undetected bugs in bzip2 (hopefully very unlikely). The chances of data corruption going undetected is microscopic, about one chance in four billion for each file processed. Be aware, though, that the check occurs upon decompression, so it can only tell you that that something is wrong. It can't help you recover the original uncompressed data. You can use bzip2recover to try to recover data from damaged files. Return values: 0 for a normal exit, 1 for environmental problems (file not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt compressed file, 3 for an internal consistency error (eg, bug) which caused bzip2 to panic. MEMORY MANAGEMENT Bzip2 compresses large files in blocks. The block size affects both the compression ratio achieved, and the amount of memory needed both for compression and decom- pression. The flags -1 through -9 specify the block size to be 100,000 bytes through 900,000 bytes (the default) respectively. At decompression-time, the block size used for compression is read from the header of the compressed file, and bunzip2 then allocates itself just enough memory to decompress the file. Since block sizes are stored in compressed files, it follows that the flags -1 to -9 are irrelevant to and so ignored during decompression. Com- pression and decompression requirements, in bytes, can be estimated as: Compression: 400k + ( 7 x block size ) Decompression: 100k + ( 5 x block size ), or 100k + ( 2.5 x block size ) Larger block sizes give rapidly diminishing marginal returns; most of the compression comes from the first two or three hundred k of block size, a fact worth bearing in mind when using bzip2 on small machines. It is also important to appreciate that the decompression memory requirement is set at compression-time by the choice of block size. For files compressed with the default 900k block size, bunzip2 will require about 4600 kbytes to decompress. To support decompression of any file on a 4 megabyte machine, bunzip2 has an option to decompress using approximately half this amount of memory, about 2300 kbytes. Decompres- sion speed is also halved, so you should use this option only where necessary. The relevant flag is -s. In general, try and use the largest block size memory con- straints allow, since that maximises the compression achieved. Compression and decompression speed are virtu- ally unaffected by block size. Another significant point applies to files which fit in a single block -- that means most files you'd encounter using a large block size. The amount of real memory touched is proportional to the size of the file, since the file is smaller than a block. For example, compressing a file 20,000 bytes long with the flag -9 will cause the compressor to allocate around 6700k of memory, but only touch 400k + 20000 * 7 = 540 kbytes of it. Similarly, the decompressor will allocate 4600k but only touch 100k + 20000 * 5 = 200 kbytes. Here is a table which summarises the maximum memory usage for different block sizes. Also recorded is the total compressed size for 14 files of the Calgary Text Compres- sion Corpus totalling 3,141,622 bytes. This column gives some feel for how compression varies with block size. These figures tend to understate the advantage of larger block sizes for larger files, since the Corpus is domi- nated by smaller files. Compress Decompress Decompress Corpus Flag usage usage -s usage Size -1 1100k 600k 350k 914704 -2 1800k 1100k 600k 877703 -3 2500k 1600k 850k 860338 -4 3200k 2100k 1100k 846899 -5 3900k 2600k 1350k 845160 -6 4600k 3100k 1600k 838626 -7 5400k 3600k 1850k 834096 -8 6000k 4100k 2100k 828642 -9 6700k 4600k 2350k 828642 OPTIONS -c --stdout Compress or decompress to standard output. -c will decompress multiple files to stdout, but will only compress a single file to stdout. -d --decompress Force decompression. Bzip2 and bunzip2 are really the same program, and the decision about whether to compress or decompress is done on the basis of which name is used. This flag overrides that mech- anism, and forces bzip2 to decompress. -f --compress The complement to -d: forces compression, regard- less of the invocation name. -t --test Check integrity of the specified file(s), but don't decompress them. This really performs a trial decompression and throws away the result, using the low-memory decompression algorithm (see -s). -k --keep Keep (don't delete) input files during compression or decompression. -s --small Reduce memory usage, both for compression and decompression. Files are decompressed using a mod- ified algorithm which only requires 2.5 bytes per block byte. This means any file can be decom- pressed in 2300k of memory, albeit somewhat more slowly than usual. During compression, -s selects a block size of 200k, which limits memory use to around the same figure, at the expense of your compression ratio. In short, if your machine is low on memory (8 megabytes or less), use -s for everything. See MEMORY MANAGEMENT above. -v --verbose Verbose mode -- show the compression ratio for each file processed. Further -v's increase the ver- bosity level, spewing out lots of information which is primarily of interest for diagnostic purposes. -L --license Display the software version, license terms and conditions. -V --version Same as -L. -1 to -9 Set the block size to 100 k, 200 k .. 900 k when compressing. Has no effect when decompressing. See MEMORY MANAGEMENT above. --repetitive-fast bzip2 injects some small pseudo-random variations into very repetitive blocks to limit worst-case performance during compression. If sorting runs into difficulties, the block is randomised, and sorting is restarted. Very roughly, bzip2 persists for three times as long as a well-behaved input would take before resorting to randomisation. This flag makes it give up much sooner. --repetitive-best Opposite of --repetitive-fast; try a lot harder before resorting to randomisation. RECOVERING DATA FROM DAMAGED FILES bzip2 compresses files in blocks, usually 900kbytes long. Each block is handled independently. If a media or trans- mission error causes a multi-block .bz2 file to become damaged, it may be possible to recover data from the undamaged blocks in the file. The compressed representation of each block is delimited by a 48-bit pattern, which makes it possible to find the block boundaries with reasonable certainty. Each block also carries its own 32-bit CRC, so damaged blocks can be distinguished from undamaged ones. bzip2recover is a simple program whose purpose is to search for blocks in .bz2 files, and write each block out into its own .bz2 file. You can then use bzip2 -t to test the integrity of the resulting files, and decompress those which are undamaged. bzip2recover takes a single argument, the name of the dam- aged file, and writes a number of files "rec0001file.bz2", "rec0002file.bz2", etc, containing the extracted blocks. The output filenames are designed so that the use of wild- cards in subsequent processing -- for example, "bzip2 -dc rec*file.bz2 > recovereddata" -- lists the files in the "right" order. bzip2recover should be of most use dealing with large .bz2 files, as these will contain many blocks. It is clearly futile to use it on damaged single-block files, since a damaged block cannot be recovered. If you wish to min- imise any potential data loss through media or transmis- sion errors, you might consider compressing with a smaller block size. PERFORMANCE NOTES The sorting phase of compression gathers together similar strings in the file. Because of this, files containing very long runs of repeated symbols, like "aabaabaabaab ..." (repeated several hundred times) may compress extraordinarily slowly. You can use the -vvvvv option to monitor progress in great detail, if you want. Decompres- sion speed is unaffected. Such pathological cases seem rare in practice, appearing mostly in artificially-constructed test files, and in low- level disk images. It may be inadvisable to use bzip2 to compress the latter. If you do get a file which causes severe slowness in compression, try making the block size as small as possible, with flag -1. Incompressible or virtually-incompressible data may decom- press rather more slowly than one would hope. This is due to a naive implementation of the move-to-front coder. bzip2 usually allocates several megabytes of memory to operate in, and then charges all over it in a fairly ran- dom fashion. This means that performance, both for com- pressing and decompressing, is largely determined by the speed at which your machine can service cache misses. Because of this, small changes to the code to reduce the miss rate have been observed to give disproportionately large performance improvements. I imagine bzip2 will per- form best on machines with very large caches. Test mode (-t) uses the low-memory decompression algorithm (-s). This means test mode does not run as fast as it could; it could run as fast as the normal decompression machinery. This could easily be fixed at the cost of some code bloat. CAVEATS I/O error messages are not as helpful as they could be. Bzip2 tries hard to detect I/O errors and exit cleanly, but the details of what the problem is sometimes seem rather misleading. This manual page pertains to version 0.1 of bzip2. It may well happen that some future version will use a different compressed file format. If you try to decompress, using 0.1, a .bz2 file created with some future version which uses a different compressed file format, 0.1 will complain that your file "is not a bzip2 file". If that happens, you should obtain a more recent version of bzip2 and use that to decompress the file. Wildcard expansion for Windows 95 and NT is flaky. bzip2recover uses 32-bit integers to represent bit posi- tions in compressed files, so it cannot handle compressed files more than 512 megabytes long. This could easily be fixed. bzip2recover sometimes reports a very small, incomplete final block. This is spurious and can be safely ignored. RELATIONSHIP TO bzip-0.21 This program is a descendant of the bzip program, version 0.21, which I released in August 1996. The primary dif- ference of bzip2 is its avoidance of the possibly patented algorithms which were used in 0.21. bzip2 also brings various useful refinements (-s, -t), uses less memory, decompresses significantly faster, and has support for recovering data from damaged files. Because bzip2 uses Huffman coding to construct the com- pressed bitstream, rather than the arithmetic coding used in 0.21, the compressed representations generated by the two programs are incompatible, and they will not interop- erate. The change in suffix from .bz to .bz2 reflects this. It would have been helpful to at least allow bzip2 to decompress files created by 0.21, but this would defeat the primary aim of having a patent-free compressor. For a more precise statement about patent issues in bzip2, please see the README file in the distribution. Huffman coding necessarily involves some coding ineffi- ciency compared to arithmetic coding. This means that bzip2 compresses about 1% worse than 0.21, an unfortunate but unavoidable fact-of-life. On the other hand, decom- pression is approximately 50% faster for the same reason, and the change in file format gave an opportunity to add data-recovery features. So it is not all bad. AUTHOR Julian Seward, jseward@acm.org. The ideas embodied in bzip and bzip2 are due to (at least) the following people: Michael Burrows and David Wheeler (for the block sorting transformation), David Wheeler (again, for the Huffman coder), Peter Fenwick (for the structured coding model in 0.21, and many refinements), and Alistair Moffat, Radford Neal and Ian Witten (for the arithmetic coder in 0.21). I am much indebted for their help, support and advice. See the file ALGORITHMS in the source distribution for pointers to sources of documenta- tion. Christian von Roques encouraged me to look for faster sorting algorithms, so as to speed up compression. Bela Lubkin encouraged me to improve the worst-case com- pression performance. Many people sent patches, helped with portability problems, lent machines, gave advice and were generally helpful. ========================================================================= GNU GENERAL PUBLIC LICENSE Version 2, June 1991 Copyright (C) 1989, 1991 Free Software Foundation, Inc. 675 Mass Ave, Cambridge, MA 02139, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) 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If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances. It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice. This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. 8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. 9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation. 10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS Appendix: How to Apply These Terms to Your New Programs If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. <one line to give the program's name and a brief idea of what it does.> Copyright (C) 19yy <name of author> This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. Also add information on how to contact you by electronic and paper mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: Gnomovision version 69, Copyright (C) 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program. You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. <signature of Ty Coon>, 1 April 1989 Ty Coon, President of Vice This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.

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