I don't understand how arrays can help me to reduce the size of the void loop code though.
Well, pinMode() doesn't take that many arguments...
So is there a function that send a understandable signal to processing just once and not 9600 times per second?
Yes. It is Serial.print(). The key is to call the function just once, not 9600 times per second (or more). I suggested that you look at the state change detection example. Apparently, you haven't, so I'll make the same suggestion again.