ZIP
From AbiWiki
The Zip archive format was created by the late Phil Katz of PKWare, Inc. Phil began by creating archive utilities to create and extract files in the .ARC format used by the older Arc utility from Seaware. After legal battles with Seaware, Phil created a new archive format called Zip, and placed the format in the public domain so anyone could created archivers that used it.
Katz's original program, PKZip, still exists, as well as a Windows GUI version. But at this point, the most popular Zip archive utility is WinZip from Nico Mak.
Many archive utilities, both freeware and shareware, exist to handle Zip archives. As of Windows XP, Windows has built-in support for viewing and extracting Zip files in a feature called Zip Folders. It can also create them. Support for ZIP files is built into Windows XP, Windows MCP, and Windows Vista.
Info-Zip is an open source command line version that is available for many different operating systems. There is also an open source option at Yahoo widgets where there is a simple utility called ZIPPER which works effortlessly. You simply drag your file into the window for zipping or unzipping.
Another popular free zip utility is 7zip. It can view a zipped file and permits you to drag files in or out of it. This can be very handy for tweaking an ePub file, even without changing the file extension.
Embedded zip
More and more tools are now using zip to collect files and compress them while hiding this fact from the users. The tools themselves are able to work in these compressed files with no visible decompress step. eBook (eDocument) File formats that use this technique include ePUB, CBZ, SGF, ODT and DOCX. TIF can also be a compressed collection of images that use zip format although other compression methods can also be used.
The file format FB2 can also typically read a zip file by programs like FBReader or Cool Reader so you may see a file in the form of filename.fb2.zip. This double extension trick is non-standard and can lead to problems with some systems.
GZIP
GZIP is a variation of the zip format (.gz) that was developed by the GNU team. It is designed to be zipped or unzipped on the fly (perhaps in a pipe) and only supports one file. Often the file is a tar (.tar) format which is an container (archive) format. When used together the file extension is usually .tgz.
Gzip is also the compressed format used by ABW where is it called ZABW. It is also the compression method used in zText files where it read directly without a separate decompression.
