U3 (software)

U3 was a joint venture between SanDisk and M-Systems, producing a proprietary method of launching Windows software from special USB flash drives. Flash drives adhering to the U3 specification are termed "U3 smart drives". U3 smart drives come preinstalled with the U3 Launchpad. Applications that comply with U3 specifications are allowed to write or registry information to the host computer, but they must remove this information when the flash drive is ejected. Customizations and settings are instead stored with the application on the flash drive. Microsoft and SanDisk created a successor called StartKey. SanDisk began phasing out support for U3 Technology in late 2009. A U3 flash drive presents itself to the host system as a USB hub with a CD drive and standard USB mass storage device attached. This configuration causes Windows disk management to show two drives: A read-only ISO 9660 volume on an emulated CD-ROM drive with an autorun configuration to execute the U3 LaunchPad, and; A standard flash drive ( formatted) that includes a hidden "SYSTEM" folder with installed applications. U3 compliant applications can be (optionally) preloaded by manufacturers. The U3 Launchpad (LaunchU3.exe) is a Windows program manager that is preinstalled on every U3 smart drive. The U3 Launchpad automatically starts at insertion of a U3 enabled device. To be fully U3 compliant, an application has to be programmed to clean up its own data from the local machine. It must also be packaged in U3's special program format. U3 applications will only run from a U3 device. U3 programs can be downloaded from the U3 website and other places. Applications include Opera and Skype and do not need to be installed on the computer. The U3 application programming interfaces (APIs) allow U3 programs lower-level access to USB flash drive, and to query the drive letter. The U3 APIs primarily allow developers who choose to use more of the power of U3 to control how their application handles things like device removal and saves data back to the drive such as configuration or documents.