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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