The Zip file format is the most popular archive file format. Zip allows the packing and compressing of multiple files in one archive. Zip has been around since the 90s. Here is some more information about the Zip format and its history.

Zip is a lossless data compression format. In other words Zip was designed to compressed data files such as Word documents and spreadsheets. It is not intended for multimedia compression for example photos are better compressed using the JPEG algorithm rather than the Zip algorithm.

Zip was created in the 90s by Phil Katz who named his Zip software after himself the Phil Katz Zip software or more widely known as PKZip. Over the years there were many software utilities developed to support Zip files. Some of them were limited to just opening Zip files while others were full blown Zip utilities that can open and create Zip files. Today the most popular commercial Zip software utility is WinZip while the most popular free Zip utility is the open source 7Zip project.

Zip files can be identified by their zip file extension although it is not mandatory and Zip archive files can have any file extension that one wishes. Zip supports a few compression algorithms although in practice the most and almost solely used is the Deflate algorithm. In fact Zip also support an algorithm that is known as Store which just adds files to an archive without any compression.

The Zip file packs a few files into one archive but its compression is implemented on each file in the file separately. In other words Zip has two different stages when creating an archive. The first stage is to compress each file separately and the second is to pack them all in one file with an index that allows access to each of those files directly.

In addition to packing and compressing files into one archive Zip supports some other features. For example Zip can allow archive files to be split if the file is too big. Splitting archives into smaller partial files is useful when for example when you want to burn the files to a CD or transfer them over email. Zip also allows to secure the archive by encrypting it using a few optional different strengths encryption algorithms. When you encrypt a Zip file nobody will be able to open and read the files in the archive unless they know the encryption key that is also called the Zip archive file password.

Zip is available on multiple platforms including Windows Mac OS and linux but also on smaller systems like portable operating systems. If the Zip software you use on your platform adheres to the Zip standard than the Zip archive should be cross platform compatible.

Zip files are also used as software installation formats. Zip supports what is known as a self extract archive file. A self extract archive is a Zip archive that is added a code that can open the archive without the need for a Zip utility. Self extract files are executable files with a EXE extension. The self extract code can also be programmed to automatically run one of the files extracted from the self extract archive usually a file called setup.exe