Quick introduction to USB
Every computer has a USB connector on it, and all the connectors
are the same, with 4 pins. One pin is Ground, two pins are Data (D+ and
D-) and the last pin is 5V power. The Ground and 5V pins are used to
provide power to whatever is plugged in - keyboard, mouse, USB key, etc.
The two data lines are used to transfer information back and forth -
what keys are pressed, saving files to the USB drive, etc.
