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Packing, compressing and encoding files

It is very convenient and efficient for the storage and transfer of files via ftp to pack, compress and encode them. The reasons for so doing are:

Available Software

The most popular and widely-used programs for packing, compressing and encoding files are indicated in the list below.

  File     Program               Pack  Compress  Encode   File  Operating
Extension   Name                                          Type   System    

.arc       ARC                     X      X              binary  MS-DOS
.bin       MacBinary                               X     binary  Macintosh
.cpt       Compactor Pro           X      X              binary  Macintosh
.gz        GNU zip                        X              binary  UNIX
.hqx       BinHex4                 X               X     text    Macintosh
.lha,.lzh  Lempel-Ziv-Huffman      X      X              binary  Atari
.msa       Magic Shadow Archiver   X      X              binary  Atari
.sea       Self Extracting Archive X      X              binary  Macintosh
.shar      Shell Archive           X                     text    UNIX
.sit       Stuffit                 X      X              binary  Macintosh
.tar       tar                     X                     binary  UNIX
.uue       uuencode                                X     text    UNIX
.Z         compress                       X              binary  UNIX
.zip       PKZIP                   X      X              binary  MS-DOS
.zoo       Zoo                     X      X              binary  MS-DOS

In most cases one identifies the compression or packing algorithm from the file extension. A file may be packed by one program and then compressed by another. For example, .tar.Z means that file structure was first packed by tar and then compressed with compress. In some cases one see only one extension is appended, e.g. only .uue. But when such a file is decoded (with uuencode), a new file is produced with another extension, e.g. .Z.

The above software can be obtained from many anonymous ftp servers spread around the world. Locations can be identified by using an Archie server. On the anonymous ftp servers one frequently finds a FAQ document giving much fuller information on packing, compressing and encoding.

Image, video and audio

Other compression techniques exist for image, video and audio files. These can be both lossless and lossy algorithms. GIF, JPEG and MPEG are standards in this area.


[Index] - 20th June 1996 - © Howard Flack - Not to be copied or reproduced without permission