Universal Serial Bus

In computing, a royalty-free connector intended to replace the out-of-date COM and parallel printer ports that have been used in PCs since 1981. The USB allows up to 127 peripherals – including joysticks, scanners, printers, and keyboards – to be daisy-chained from a single socket, offering higher speeds and improved plug-and-play facilities.

The USB includes hardware and software specifications controlled by the multivendor USB-IF (Universal Serial Bus Implementors Forum) formed in March 1995. This original specification is now known as USB1 and it operates at between 1 and 12 megabits per second. USB2 (with speeds of up to 480 megabits per second) was developed as an alternative to IEEE 1394 (or FireWire), which was capable of allowing speeds of up to 400 megabits per second (since improved to 800 megabits per second). USB1 peripherals can be linked to USB2 sockets, avoiding the need to change the peripherals that the switch to IEEE 1394 would require. Some PC motherboards included USB connectors from October 1996, and Release 2 of Windows 95 supported USB as long as peripherals came with their own drivers. Microsoft provided full software support for USB from Windows 98 onwards.