These are ultra-compact flash memory data storage devices that have an integral USB interface. They are very small (typically 100mm or about four inches long), ultra lightweight, removable, and rewritable. They are also popularly called “thumb drives” or “jump drives” because of their size. They are capable of holding a lot of data, yet are very reliable due to their lack moving parts. The USB interface is now universal, so flash drives may be supported natively by operating systems as diverse as Windows, Mac OS X, Linux, and Unix. There is a small printed circuit board inside these drives, protected by a plastic or metal casing, making them sturdy enough to be attached (depending upon the design) to a keychain or lanyard. The protruding USB connector is protected by a removable cap or by retracting into the body of the device. Flash drives are active only when plugged into a host device (typically a laptop computer or USB hub) which provides the necessary power for the drive to become active.