Re: Joystick>>RobotC>>.txt file>>arduino?
What are your goals? Like Ernest3.14 said, it may be easier to have arduino to read the joystick directly. The game controllers are USB HID devices. It is relatively easy to write a Windows App to read the joystick. I haven't hacked too much with arduino but the USB interface is supposed to be a COM interface (i.e. serial) So it should be quite easy to have the Windows app reading the joystick and writing it to the USB COM port. But of course, the next step is to write code for the arduino to read the serial stream and react to it.
Alternatively, there are many variations of arduino. If your arduino has a USB host port (e.g. USB host shield), you can even plug the game controller directly to it. But then you need to understand how to write arduino code to read and interpret HID reports unless there is an Arduino library for it. There is a pretty good article on the subject.http://www.circuitsathome.com/communica ... ces-part-1