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comp.compression Frequently Asked Questions (part 1/3)
Section - [2] What is this .xxx file type? Where can I find the corresponding compression program?

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Top Document: comp.compression Frequently Asked Questions (part 1/3)
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All the programs mentioned in this section are lossless.  For most
programs, one US and one European ftp site are given.  (
and Many other sites (in particular
have the same programs.

To keep this list to a reasonable size, many programs are not mentioned
here. When several programs can handle the same archive format, only one of
them is given. If you don't find a particular archiver here, look also in:

Sources for additional lossless data compressors can be found in (sources in Pascal) (Splay tree compression)

For Macintosh programs, look on
  or in
For VM/CMS, look on
For Atari, look on
For Amiga, look on

A general purpose lossless data compression library is available in or;
see for more information.
Another library favoring speed over compression ratio is available at

If you don't know how to use ftp or don't have ftp access, read the
article "How to find sources" which is regularly posted in news.answers.

If you can't find a program given below, a newer version probably exists in
the same directory.  Tell me at <jloup at>

A very short description of the compression algorithm is given for most
programs. For the meaning of LZ77, LZ78 and LZW, see question 70 in part 2 of
the FAQ.  If you are looking for the file format of a specific compression
program, look at "The File Format Collection" in
and/or get the sources of the decompressor. For the format of uuencode, do
"man 5 uuencode" on a Unix box.

ext:  produced by or read by

.ace: ACE

.arc, .ark: arc, pkarc for MSDOS. (LZW algorithm)

      arc for Unix
        Contact: Howard Chu <>

      arc for VMS

      for Mac

      arc for Amiga

.arj: arj for MSDOS (LZ77 with hashing, plus secondary static Huffman
          encoding on a block basis)
        Contact: Robert K Jung <>

      unarj for Unix. Decompresses only. (There is no arj compressor for Unix.
        Don't post a request.)

      unarj for Mac      

      unarj for Amiga

base64 (MIME encoding): This is *not* a compression issue but it keeps
       coming as a question on comp.compression. So:
        (MSDOS exe)

.bck: VMS BACKUP. BACKUP is *not* a compression program. Do "help backup".

.bz2: bzip2 by Julian Seward (Burrows-Wheeler block sorting, see item 78)

.cab: Microsoft Cabinets

.cpt: Compact Pro for Mac and Power PC

      For Unix:

      For DOS:

.ddi:  files made by DiskDupe (Pro)

.exe: self-extracting MSDOS executable (creates files on disk when run)
      Run the file, or try unzip, lha or arj on it.

.exe: compressed MSDOS executable (decompresses itself in memory then runs
      the decompressed code). To get the original uncompressed .exe:
      To create such files: (for Windows)

.gif: gif files are images compressed with the LZW algorithm. See the FAQ list for programs manipulating .gif files. See
      suffix .Z below for source of LZW.

.gz, .z: gzip (or pack, see .z below). gzip uses the same algorithm as
         zip 2.0x (see below); it can also extract packed and compressed files.
	Contact: Jean-loup Gailly <support at>

      For Unix, MSDOS, OS/2, VMS, Atari, Amiga, Primos: (.shar or .tar.gz: source) (MSDOS self-extract) (MSDOS)          (source)       (MSDOS exe)     (WIN95 & NT)        (OS/2)    (VMS exe) (Solaris 2)                      (MVS exe)

      For Mac: (MacGzip page)

.ha: ha 0.99 (improved PPMC - 4th order Markov modeling)
	Contact: Harri Hirvola <>

.hap: Hamarsoft HAP archiver (Markov modeling + arithmetic coding)
      Contact: or

.hpk: hpack (archiver with strong encryption)
      Contact: Peter Gutmann <>

.hqx: Macintosh BinHex format.. (BinHex is *not* a compression program,
	  it is similar to uuencode but handles multiple forks.)
       for Mac:

       for Unix:

       for MSDOS:

.jam: JAM real-time compressor for MSDOS

.lzh: lha for MSDOS (LZ77 with a trie data structure, plus secondary static
          Huffman coding on a block basis)

      lharc for Unix. (LZ77 with hash table and binary trees, plus secondary
          Huffman coding).  See lha for Unix below.
           Warning: lharc can extract .lzh files created by
           lharc 1.xx but not those created by lha.

      lharc for VMS. Same warning as for Unix lharc.

      lha for Unix.
          Contact: or

      lha for Mac

      lha for Amiga
      lha for OS/2:

MIME: see base64 above

.pak: pak for MSDOS (LZW algorithm)

.pit: PackIt (Macintosh)
       for Mac:

       for Unix:

.pp: PowerPacker (Amiga)

.rar: RAR Contact: Eugene Roshal <>
          or Andrey Spasibozhko <>

      MSDOS: rar*.exe rar*.exe rar*.exe *rar2*.exe
      Unix: rar*.exe
      Amiga (Unrar):

.sea: self-extracting archive (Macintosh)
         Run the file to extract it. The self-extraction code can be
         removed with: (MS Windows, .sit only)

.sdn: used by the Shareware Distribution Network.
      Try the decompressors for .pak or .arj (see above)

.shar:  Shell archive. This is not a compression program. Use "sh foo.shar"
        to extract on Unix.  (MSDOS) (Mac)

.sit: Stuffit for Macintosh
       for Mac:

       for Amiga:

       for MSDOS:

.?q?: Squeeze for MSDOS (do not confuse with other 'squeeze' below).
      Static Huffman coding. (squeeze) (unsqueeze)

.sqz: Squeeze for MSDOS (do not confuse with other 'squeeze' above)
      LZ77 with hashing.

.tar: tar is *not* a compression program. However, to be kind for you:
      for MSDOS

      for Unix
        tar (you have it already. To extract: tar xvf file.tar)

      for VMS

      for Macintosh

      for Amiga:

.tar.Z, .tar-z, .taz: tar + compress
      For Unix:     zcat file.tar.Z | tar xvf -
      with GNU tar: tar xvzf file.tar.Z
      for MSDOS:  (MSDOS exe)* (sources)* (MSDOS exe)
      Other OS: first uncompress (see .Z below) then untar (see .tar above)

.tar.gz, .tgz, .tar-gz, .tar.z: tar + gzip
      For Unix: gzip -cd file.tar.gz | tar xvf -
        with GNU tar: tar xvzf file.tar.gz
      for MSDOS:
      for MSDOS, Windows 95, NT & OS/2:
      for Windows 95 & Windows NT: or

      Other OS: first uncompress (see .gz above) then untar (see .tar above)

.td0: (compressed MS-DOS floppy image produced by TeleDisk)

.uc2: UC2 for MSDOS and OS/2. (LZ77 with secondary static Huffman encoding on
	 a block basis, and dynamic dictionaries shared among files.)
	Contact:  (or uc2pro.exe)

.z:   pack or gzip (see .gz above). pack uses static Huffman coding.
      To extract, see .gz above.

.zip: pkzip 2.04g for MSDOS. (LZ77 with hashing, plus secondary static
           Huffman coding on a block basis). Contact:
           or (WIN95)

      arcutil 2.0 for VM/CMS (unzip only, not yet compatible with pkzip 2.04)*

      zip 1.1 for Unix, MSDOS, VMS, OS/2, ... (compatible with pkzip 1.10.
	 For corresponding unzip, see unzip 5.32 below).

      zip 2.2 and unzip 5.32 for Unix, MSDOS, VMS, OS/2, Amiga, ...
          Compatible with pkzip 2.04g (LZ77 with hashing, plus secondary static
          Huffman coding on a block basis). Contact:
          See also
          (On SGI, do not confuse with the editor also named 'zip'.)      (source)     (source)   (MSDOS exe) (MSDOS exe)  (Win95 & NT) (Win95 & NT)
         [The Win95 version supports long file names; MSDOS version doesn't]          (OS/2 exe 16&32 bit)
          See also AMIGA, ATARI, MAC, UNIX, RISCOS, VMS... subdirectories.
    (encryption source)

       for Macintosh:

       WinZip by Nico Mak <> (uses Info-ZIP compress. code): or   (MS Windows)

.zoo: zoo 2.10 for MSDOS (algorithm copied from that of lha, see lha above)

      zoo 2.10 for Unix, VMS

      zoo for Mac

      zoo for Amiga

.??_: Microsoft compress.exe and expand.exe. compress.exe is available
	in the Windows SDK (Software Development Kit) and in

.F: freeze for Unix (LZ77 with hashing, plus secondary dynamic Huffman
     Contact: Leonid A. Broukhis <>

.Y: yabba for Unix, VMS, ... (Y coding, a variant of LZ78)
  Contact: Dan Bernstein <>

.Z: compress for Unix ('the' LZW algorithm)
      It is likely that your Unix system has 'compress' already. Otherwise:
        (not in .Z format to avoid chicken and egg problem)

    compress for MSDOS

    compress for Macintosh

    compress for Amiga

    compress for VAX/VMS

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