RAR
The RAR compression format was created by Eugene Rorshal, and originally used in his RAR archiver for MS-DOS. RAR provides somewhat higher compression than the popular ZIP format. RAR files also provide special support for multi-media files, as well as the ability to create archives that span multiple RAR files, and to specify the size of individual archive files, as well as providing features for repairing archives damaged in transmission or with missing parts. As Windows became popular, a GUI Windows version of the archiver was written and is the current version.
Rorshal released public domain C code years ago to open and extract RAR archives, so many utilities exist to open RAR files, but only RAR/WinRAR can create them.
RAR files are more widely used in Europe than the US, where the Zip file is the default standard, but they are popular for posting in Usenet binary newsgroups because of the ability to control the size of individual parts and the facilities available to repair RAR archives damaged in transmission or for which all parts have not been received.
A number of archive utilities exist that can extract RAR archives, including the free and open source 7zip utility, and the freeware Izarc and Tugzip utilities for Windows.
RAR is embedded in the CBR format used for Comic Books.