A USB drive -- also known as a flash drive or keychain drive -- is a plug-and-play portable storage device that uses flash memory and is lightweight enough to attach to a key chain. A USB drive can be used in place of a floppy disk, Zip drive disk, or CD. When the user plugs the device into the USB port, the computer's operating system recognizes the device as a removable drive and assigns it a drive letter.
Unlike most removable drives, a USB drive does not require rebooting after it's attached, does not require batteries or an external power supply, and is not platform dependent. Several manufacturers offer additional features such as password protection, and downloadable drivers that allow the device to be compatible with older systems that do not have USB ports. USB drives are available in capacities ranging up to about 65 gigabytes (GB), depending on manufacturer, in a corresponding range of prices.
With a USB drive, data can be retained for long periods when the device is unplugged from the computer, or when the computer is powered-down with the drive left in. This makes the USB drive convenient for transferring data between a desktop computer and a notebook computer, or for personal backup needs.