usb 的功用，重有佢的優點，還有佢的影響！Thx

Universal Serial Bus (USB) is a serial bus standard to connect devices to a host computer. USB was designed to allow many peripherals to be connected using a single standardized interface socket and to improve plug and play capabilities by allowing hot swapping; that is, by allowing devices to be connected and disconnected without rebooting the computer or turning off the device. Other convenient features include providing power to low-consumption devices, eliminating the need for an external power supply; and allowing many devices to be used without requiring manufacturer-specific device drivers to be installed.

adv:
A new major feature is the SuperSpeed bus, which provides a fourth transfer mode at 5 Gbit/s. The raw throughput is 500 MByte/s, and the specification considers it reasonable to achieve 400 MByte/s or more after protocol overhead.