||This article needs attention from an expert in Software. The specific problem is: Most sections refer to single source and are specific to Microsoft Windows. (November 2012)|
Generally, most (third-party) uninstallers contain the following components:
- Logger: The Logger is used to log installations (e.g., log which files were added or changed, which registry entries were added or changed, etc. at the time of installation). This log is used when the user decides to uninstall the logged installation at later date (in that case, the log is "reversed" — i.e., the log is read, but opposite actions are taken in reverse order).
- Uninstaller: The Uninstaller is used to reverse changes in the log. This way, the applications can be uninstalled because all changes that were made at the times of installation are reversed.
- Analyzer (optional): The Analyzer is used to uninstall programs of which installation is not logged by the uninstaller. In that case, the program analyzes the program and finds (and deletes, if the user decided to uninstall the program) all related files and registry entries.
- Watcher (optional): The Watcher watches running programs for installation programs (and usually offers to start the logger when such programs are detected). Usually, this works by watching the tasklist for any names that are usually used by installation programs (e.g., SETUP.EXE, INSTALL.EXE, etc.)
- Other tools (optional): Some uninstallers may also contain other related tools like a junk file cleaner, browser history cleaner, cache cleaner, etc. These tools are not mandatory for uninstallers and are added mainly to improve the merchantability (since pure uninstallers are unpopular today).
Usually, in most (third-party) uninstallers, the following operations can be performed:
- Log: watches any changes made to the system during installation
- Uninstall: uninstalls a program (based on the log or analysis)
- Move/Transport: backs up a program (usually packs all required files and registry entries in a "transport package", which can be transported and installed in another computer) and uninstalls them
- Archive: backs up a program (and possibly compresses it to save disk space) and uninstalls it
- Backup: backs up a program (for reinstallation at a later date should the program fail)
- Other related operations: such as junk file cleaning, cache cleaning, etc.
Third-party uninstallers today
Nowadays, pure third-party uninstallers (uninstallers that only contain basic components — that is the watcher, logger, uninstaller, and probably the analyzer) generally are unpopular and are not needed anymore, because:
- Most software programs come with their own uninstallers (which are generally better and more accurate),
- Most uninstallers are not entirely accurate (most of them are known to leave leftovers, which should be deleted by uninstallers),
- There are many better and safer tools that can be used to replace uninstallers,
Because of this, to make uninstallers more merchantable, most (if not all) of today's uninstallers contain other related tools (such as a cache cleaner, a junk file cleaner, etc.). 
Why the third-party uninstallers are still used today:
- More complex installed programs make system changes that the authors forget, ignore or are not aware of. They often integrate third-party components with no thought of their uninstallation. The competition to release new software versions with additional features leaves the uninstallation with a very small amount of attention and testing. The accuracy of the integrated uninstallers commonly leaves much to be desired.
- The uninstallers that don't contain a logger module are aggressively promoted on the market claiming that they completely uninstall programs (a task that is impossible and even dangerous without monitoring an installation)
- Many programs are bundled with all kind of add-ons, spyware or not, that are intentionally left on the user's computer after uninstallation of the main program.
- At this time — when adware, spyware, keyloggers, trojans and other Internet threats appear every day — installation of a software product from an unknown source is a great risk. When things go wrong with a newly installed program, an uninstaller with a logger module can prove invaluable.
History of uninstallers
Uninstall was invented by Jack Bicer. While he was working on Norton Desktop for Windows at Symantec, Bicer came up with the Uninstall concept and developed the first Uninstall program. Ken Spreitzer wrote the first widely used PC program called "UnInstaller", first licensed to MicroHelp and then by February 1998 sold by CyberMedia. After writing the program, Spreitzer went on to create Maximized Software.
- Installation (computer programs)
- Revo Uninstaller
- ZSoft Uninstaller
- Windows Installer
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