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A USB flash drive consists of a flash memory data storage device integrated with a USB (Universal Serial Bus) 1.1 or 2.0 interface. USB flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g (1 oz).[1] Storage capacities in 2010 can be as large as 256 GB[2] with steady improvements in size and price per capacity expected. Some allow 1 million write or erase cycles[citation needed] and have a 10-year data retention cycle.[3][4]

USB flash drives are often used for the same purposes as floppy disks were. They are smaller, faster, have thousands of times more capacity, and are more durable and reliable because of their lack of moving parts. Until approximately 2005, most desktop and laptop computers were supplied with floppy disk drives, but most recent equipment has abandoned floppy disk drives in favor of USB ports.

Flash drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Mac OS X, Linux, and other Unix-like systems. USB drives with USB 2.0 support can store more data and transfer faster than a much larger optical disc drive and can be read by most other systems such as the PlayStation 3.

Nothing moves mechanically in a flash drive; the term drive persists because computers read and write flash-drive data using the same system commands as for a mechanical disk drive, with the storage appearing to the computer operating system and user interface as just another drive. Flash drives are very robust mechanically.

A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case which can be carried in a pocket or on a key chain, for example. The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. Most flash drives use a standard type-A USB connection allowing plugging into a port on a personal computer, but drives for other interfaces also exist.

Most USB flash drives draw their power from the USB connection, and do not require a battery. Some devices that combine the functionality of a digital audio player with flash-drive-type storage require a battery for the player function.