Compressed archives combine multiple files into a single file to make
them easier to transport or save on diskspace. Archiving software may
also provide options for encryption, file spanning, checksums,
self-extraction, and self-installation. Zip is the most-widely used
format, used by the Windows operating system and more recently by OSX as
well. RAR is also a very popular and flexible format. Unix uses the tar
file format, while Linux uses the tar and gz format.
