A Windows Installer patch (.msp file) is a self-contained package that has the updates to the application and describes which versions of the application can receive the patch. An application that has been established using the Microsoft Windows Installer can be advanced by reinstalling an updated installation package (.msi file), or by applying a Windows Installer patch (an .msp file) to the application. Patches handles at a minimum of two database transforms and can contain patch files that are saved in the cabinet file stream of the patch package. Servicing applications by distributing a Windows Installer patch, relatively than a complete installation package for the updated product can have advantages. A patch can handle an entire file or only the file bits necessary to update part of the file. This can enable the user to download an upgrade patch that is much smaller than the installation package for the entire product. An update using a patch can protect a user customization of the application thru the upgrade.
Equipped with a high compression ratio (as high as 7z format via LMZA and LMZA2), 7-Zip is an open-source ZIP archiver software that is usable on any computer regardless of operating system installed from the latest to the earlier versions and without any charge at all. Majority of the source codes used by this program are on the list of GNU LGPL License. These include unRar, RAR,ZIP, ARJ, XZ, Z, TAR, WIM, BZIP2, GZIP, CAB, HFS, LZMA, NSIS, CPIO, RPM, VHD, DEB, CHM, LZH, MBR, FAT, NTFS, XAR, DMG, CramFS, ISO, MSI, SquashFS, and UDF. Technically, formats ZIP and GZIP have a ratio of 2 to 10%, 7z has high ratio from 30 to 70% plus this same format has self extracting capability while both ZIP and 7z has AES 256 encryption. Other features include windows shell, file manager, command line version, FAR manager plug-in and localizations for languages up to 79.