SIS is an acronym for Symbian Installation Source. The SIS file format was developed by Symbian OS for use on mobile devices such as PDA's and Cellphones.
Contrary to popular belief, files with the .sis extension are installation files and not an application file. The real application file is the .APP file that the SIS file adds to the device that the APP application is being installed on.
The SIS files are created with the Symbian's "makesis" command line tool, which is included with the CreateSIS development program. Program developers will often use the CreateSIS program when creating applications for the Symbian operating system.
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