Following are popular archiving formats that are used to compress one or more files into a single file. Archive formats are typically capable of also storing folders in order to reconstruct the file/folder relationship when decompressed. See archive. .ARC Compressed archive. Requires ARC from SEAware, PKARC, or Vernon Buerg's tiny, free ARCE or ARC-E programs to extract. Macintosh program ArcMac and Unix program arc5521 will also work. .ARJ A compressed archive requiring the ARJ program to uncompress. Requires UNARJ. No Macintosh equivalent is available. .BTOA Binary to ASCII. A binary file in text format that must be converted back to binary with the Unix program BTOA or the Windows/DOS program ATOB. (No Mac equivalent.) The file extension .atob is, of course, ASCII to Binary. .CP or .CPIO Archives created by Unix CPIO (copy-in/copy-out) tape archiving program. An early competitor to TAR. Unix users may use the PAX (Portable Archive Exchange) program to deal with such files or with .TAR files. For DOS/Windows users, the program to get is PAX2EXE. (No Mac equivalent.) .CPT A Macintosh file created by Compactor. (No DOS/Windows equivalent.) .EXE Compression programs such as PKZIP and LHA have the ability to create "self-extracting" archive files. These are files that combine the decompression program and the compressed data. When you run the EXE, you immediately decompress the archive. .gz A compressed archive requiring a Unix interpretation of PKZIP, specifically the gzip (GNU Zip) program from the GNU Project. Get gzip or gunzip for DOS/Windows machines. (No Mac equivalent.) .Hqx or .hqx A Macintosh compression format. Requires the Mac program BinHex, the DOS/Windows program XBIN or the Unix program MCVERT to convert. .LHA or .LZH A DOS compressed archive requiring the use of the public domain program LHA, which can handle archives created by its predecessor if you specify the /O (for "old version") switch. LHA or WinZip are good choices for DOS/Windows users. Mac users should get MacLHarc. .PAK A DOS compressed archive created by the PAK program. Rarely seen these days. (No Mac equivalent.) .PIT A file created by the Macintosh program PackIt. DOS/Windows users can use UNPACKIT. .RAR Based on the ZIP method, the RAR format supports international character sets and is popular in Europe and Russia. .SEA A Macintosh self-extracting archive. (No DOS/Windows equivalent.) .shar, .sh, or .Shar A "shell archive" created by the Unix SHAR program. Use UNSHAR to uncompress. There are versions for both Wintel machines and the Macintosh. .SIT, .SITX A compressed archive created by Stuffit from Allume Systems, Inc. (formerly Aladdin Systems). Originally for the Mac, then Windows and Linux. UNSTUFF and UNSIT were used for earlier DOS/Windows files. .taz or .tgz Short for ".tar.z". Use the gzip program first on such files, and then TAR. No Mac equivalent for gzip, but there is one for TAR. .tar or -tar "Tape ARchive" files are packed into a single file by the Unix TAR program. Use TAR to unpack. Macintosh users should look for UNTAR. .UU or .UUE A binary file in ASCII format requiring the UUDECODE program or a clone to convert back into binary form. DOS/Window users should use UUDECODE by Richard Marks since it is the best version. Macintosh users should look for UUTOOL. .Z Upper case "Z." A compressed file requiring the Unix UNCOMPRESS program or a clone, such as the DOS program U16 or the Mac program MacCompress. .z Lower case "z." Usually indicates an archive requiring the free gzip program from GNU Project. To reduce confusion, newer versions of the gzip program create files ending in .gz instead. .ZIP Compressed archive created by PKZIP, WinZip, or a similar program. Mac owners may use ZipIt, UnZip or Stuffit Expander. The standard in the Windows world. .ZOO Compressed archive created by the ZOO program, which is required to uncompress it. DOS/Windows users use ZOO. Macintosh users use MaxBooz.