From Wikipedia, the free encyclopedia.
A keydrive (also keychain drive, pen drive, pocket drive, thumb drive, USB flash drive, USB flash memory drive, USB key, USB memory key) is a small removable data storage device that uses flash memory and a USB connector.
Keydrives take their power from the USB connection of the PC they are connected to and do not need batteries. They are impervious to the scratches and dust that have plagued previous forms of portable storage media like Compact Discs and floppy disks. Most are lightweight and small - about the size of a key or a thumb. They are popular with people who carry data between home and school or work and are quickly replacing the floppy disk as a portable data device.
Capacity has ranged from a few megabytes in size up to a few gigabytes, although some computers have trouble reading and writing to devices that have more than 2 GB of storage. In 2003 most keydrives ran at the USB 1.0/1.1 speeds of 1.5 Mbit/s or 12 Mbit/s. However, newer USB keys have the capability to utilize the high-speed USB 2.0, which tops out at 480 Mbit/s. Theoretically, the flash memory in the drives can retain data for 10 years.
Some keydrives have a physical "write protect" switch so they may be plugged with impunity into a system that might harbor a virus or worm (when set to write protected).
Most modern operating systems can read and write to keydrives without any special device drivers. Linux, Microsoft's Windows Me, 2000 and XP are able to access them, but Windows 98, which was one of the first OSes with much support for USB, needs specialized software for each different type of USB storage device it encounters. MS-DOS does not include support for USB (nor for USB booting).
Some computers have the ability to boot up from keydrives, but that capability must be supported in the computer's BIOS.
- See also: BIOS boot devices, including USB, Master Boot Record.
