USB flash drive

USB flash drives are NAND-type flash memory data storage devices integrated with a USB (universal serial bus) interface. They are typically small, lightweight, removable and rewritable. As of April 2007, memory capacities for USB Flash Drives currently are sold from 32 megabytes up to 64 gigabytes [1]. Capacity is limited only by current flash memory densities, although cost per megabyte may increase rapidly at higher capacities due to the expensive components. (USB Memory card readers are also available, whereby rather than being built-in, the memory is a removable Flash memory card housed in what is otherwise a regular USB flash drive, as described below.)
USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk. They are more compact, generally faster, hold more data, and are more reliable (due to both their lack of moving parts, and their more durable design) than floppy disks. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Linux, Mac OS X, Unix, and Windows.
A flash drive consists of a small printed circuit board typically in a plastic or metal casing, making the drive sturdy enough to be carried about in a pocket, as a key fob, or on a lanyard. Only the USB connector protrudes from this protection, and is usually covered by a removable cap. Most flash drives use a standard type-A USB connection allowing them to be connected directly to a port on a personal computer.
To access the data stored in a flash drive, the drive must be connected to a computer, either by plugging it into a USB host controller built into the computer, or into a USB hub. Flash drives are active only when plugged into a USB connection and draw all necessary power from the supply provided by that connection. However, some flash drives, especially high-speed drives utilizing the USB 2.0 standard, may require more power than the limited amount provided by a bus-powered USB hub, such as those built into some computer keyboards or monitors. These drives will not work unless plugged directly into a host controller (i.e., the ports found on the computer itself) or a self-powered hub.