USB or "Universal Serial Bus", the Chinese name for the universal serial bus. This is gradually in recent years of new interface technology widely used in the field of PC. USB interface transmission speed is faster, and support hot-plug features and connecting multiple devices. Is now widely used in all types of external device. At present there are three USB interfaces: USB1.1 and USB2.0 and usb3.0 in recent years. USB1.1 transfer speed can theoretically achieve 12Mbps/seconds and USB2.0 can reach speed of 480Mbps/seconds and can be backward compatible with USB1.1. With the rapid development of computer hardware and peripherals increasing, keyboards, mice, modems, printers, scanners, already well known, digital cameras, MP3 players followed, so many devices, how to access the PC? USB is based on this objective.