from
The Free On-line Dictionary of Computing (8 July 2008)
Universal Serial Bus
USB 2.0
<hardware, standard> (USB) An external {peripheral} interface
{standard} for communication between a computer and external
{peripherals} over an inexpensive cable using {biserial}
transmission.
USB is intended to replace existing {serial ports}, {parallel
ports}, {keyboard}, and {monitor} connectors and be used with
{keyboards}, {mice}, {monitors}, {printers}, and possibly some
low-speed {scanners} and removable {hard drives}. For faster
devices existing {IDE}, {SCSI}, or emerging {FC-AL} or
{FireWire} interfaces can be used.
USB works at 12 Mbps with specific consideration for low cost
peripherals. It supports up to 127 devices and both
{isochronous} and {asynchronous} data transfers. Cables can
be up to five metres long and it includes built-in power
distribution for low power devices. It supports {daisy
chaining} through a tiered star multidrop topology. A USB
cable has a rectangular "Type A" plug at the computer end and
a square "Type B" plug at the peripheral end.
Before March 1996 Intel started to integrate the necessary
logic into {PC} {chip sets} and encourage other manufacturers
to do likewise. It was widely available by 1997. Later
versions of {Windows 95} included support for it. It was
standard on {Macintosh} computers in 1999.
The USB 2.0 specification was released in 2000 to allow USB to
compete with {Firewire} etc. USB 2.0 is backward compatible
with USB 1.1 but works at 480 Mbps.
usb.org (http://usb.org/).
(2004-01-31)