U3

n. small portable USB drive developed so that applications can be performed directly from a specially designed USB flash drive without leaving a bit of data on the host computer (can be used for storing pictures, music and documents; enables to store and run software programs; emails and calendars can be carried in it as well)

For the airline using U3 as its IATA designator, see Avies. U3 LLC is a joint venture that is backed by Sandisk and its subsidiary, M-Systems. U3 is responsible for the development of a proprietary application design specification created for Microsoft Windows operating systems so that applications can be executed directly from a specially formatted USB flash drive (i.e. it can be run without first being installed on the computer). Applications are allowed to write files or registry information to the host computer, but this information must be removed when the flash drive is ejected. Customizations and settings are instead stored with the application on the flash drive which allows one to run software on any computer with the same settings. USB flash drives adhering to the U3 specification are termed "U3 smart drives" by U3.com. "U3 smart drives" differ from traditional USB flash drives because they come preinstalled with the U3 Launchpad, which emulates the Windows OS start menu, and controls program installation.
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