File Extension APP
File extension APP is most commonly associated with Macintosh OS X application package files. Though less common, the APP file extension is also used by Visual FoxPro 5 and above, the object-orientated procedural programming language developed by Microsoft, as well as by applications that run on the Symbian Operating System, typically found on Nokia and Sony Ericsson mobile phones and PDA?s. The APP file extension has also been used by numerous applications to denote generic application resource files or add-ons.
Mac application package files, or bundles, are similar in nature to executable File extension EXE files in Windows, and can be run to launch an application or open a self-extracting archive. In Mac OS X, it is also possible to view the contents of the package by control-clicking on it in Finder -- the Mac equivalent of Windows Explorer - and selecting "Show Package Contents" from the context menu. The contents of an APP package typically includes application resources, frameworks and plug-ins required either by or to run an application, as well as a File extension PLIST (Property List) file, which is used to store user settings or application version information. As Mac application packages often contain source files, it is not advisable to modify their contents without a full understanding of the consequences as it may prevent the application from running correctly.
Any executable file is a potential security risk, and even though malware such as viruses are rare on both the Mac and Symbian Operating Systems, they do exist. However, the risk can be minimised by having up to date antivirus software installed and only acquiring and running APP files from trusted sources.
APP files are native to Mac OS X, which runs them itself, as does Symbian OS on supported mobile phones. Microsoft Visual FoxPro is required to open generated automated procedure APP files.