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Universal Serial Bus: a standard for connection sockets on computers and other electronic equipment


(computer science)






(1) Short for "USB flash drive" or "USB port." See USB drive and USB port.

(2) (Universal Serial Bus) The most widely used hardware interface for attaching peripherals to a computer. There are at least two USB ports on laptops and four on desktop computers, while USB "hubs" provide more connections (see below). After appearing in 1997, USB became the standard for connecting keyboards, mice, printers and hard drives, eventually replacing the PC's serial and parallel ports and the Apple Desktop Bus on Macs (see serial port, parallel port and ADB).

Supporting 127 peripheral units on a single computer, devices can be plugged and unplugged while the computer is on, although a manual "eject" is required before removing. This "hot swappable" feature, combined with easy-to-reach ports on the front of the computer case, gave rise to the ubiquitous flash drive for transport (see USB drive). See PoweredUSB, USB device class, USB OTG, USB switch and USB toy.

USB Can Be Power Only
USB is also a power source for many small devices. This Chromecast streamer gets its DC power from a USB port (conveniently nearby in this photo). See Chromecast. (Image courtesy of Google Inc.)

                           Transfer RateVersion (Year)               (Mbps)

 USB 1.1 (1998)             1.5 & 12
  (1.5 Mbps slow channel
  for keyboards, mice, etc.)

 USB 2.0 Hi-Speed (2001)       480

 USB 3.0 SuperSpeed (2008)    4800
  (see  USB 3.0)

 USB 3.1 (2014)               9600
  (see  USB 3.1)

Type A and Type B Ports
All USB devices have sockets, and all the cables have plugs. Host sockets are Type A, and peripheral sockets are B, Mini-B or Micro-B. For expansion, hubs have a B or Mini-B socket to connect to the computer and several Type A sockets for devices (see USB hub).

USB Plug Configurations
With several type A sockets on every computer, USB cables have a Type A plug on one end and one of the B plugs on the other. There are also A-to-A extension cables. See Mini USB, Micro USB and USB OTG.
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Further, new devices with OTG will even be able to peer with existing, non-OTG USB devices--provided the manufacturer of the new device supports older hardware.
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