A fast input/output (I/O) data transfer standard used for connecting peripherals to a computer or controller. Typically, each device connected to a computer uses its own port. USB can connect up to 127 peripherals through a single port, and peripherals can be connected together. USB devices may be hot plugged, which means that power does not have to be turned off to connect or disconnect a peripheral. USB is becoming the primary means of connection for printers and other peripherals to PCs, and is supported by most major hardware, software and telecommunications providers.