A USB flash drive is essentially NAND-type flash memory integrated with a USB 1.1 or 2.0 interface used as a small, lightweight, removable data storage device of up to 8 GB (as of 2006). Depending on the drive type and OS version, and in some cases what patches are installed, the drives generally work with Windows 98/ME/2000/XP (Windows 98 requires a driver to be installed; often, inconveniently, a specific driver for each type of flash drive), Macintosh, Linux, and other Unix-like platforms that support USB.
USB flash drives are also known as "pen drives", "thumb drives", "flash drives", "USB keys", and a wide variety of other names. They are also sometimes erroneously called memory sticks, which is a Sony trademark describing their proprietary memory card system.
A flash drive consists of a small printed circuit board encased in a robust plastic or metal casing, making the drive sturdy enough to be carried about in a pocket, as a keyfob, or on a lanyard. Only the USB connector protrudes from this protection, and is usually covered by a removable cap. Most flash drives feature the standard type-A USB connection allowing them to be connected directly to the port. Some small drives have been made with a thin plug designed to mate with a standard USB port[3] but these are very rare.
Flash drives are active only when powered by a USB computer connection, and require no other external power source or battery power source; key drives are run off the limited supply afforded by the USB connection (5 volts and up to 500 mA). To access the data stored in a flash drive, the flash drive must be connected to a computer, either by direct connection to the computer's USB port or via a USB hub. Some need most of the power a standard USB port can supply and therefore cannot be used with a bus powered hub.
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