RogerRowland:
"Hacking" in this context means taking an exisiting device (like an old printer, scanner, washine machine, whatever) and either adapting it to some new purpose by reconfiguring it, or exposing or adding functionality that was never intended, or removing component parts and re-assembling them into something new. The Arduino can be used as part of this process, by acting as a hardware and software resource that can, for example, read the optical sensor from a laser mouse or drive a stepper motor taken from an old printer, etc.It has nothing to do with the other use of the work "hacking" - illegal entry into secure systems, password cracking, etc.
ok but for exmaple how would i get the code to access a usb keyboard, and is this possible with the arduino uno?