I'm sure this is very simple, but I'm new to processing and arduino communication. I have 3 buttons that are hooked up to my arduino uno and I want to be able to press one of the buttons and make a sound file play. Basically I want to be able to press button 1 and sound 1 plays, button 2 and sound 2, button 3 and sound 3. I have no clue what so ever on how to have the two talk to each other. As much help as I could get would be amazing, really looking for the processing code, I think I understand how to send from arduino but that code would be helpful too.

I'm pretty new to arduino and processing, but I want to control a stepper motor using processing to control a arduino. What I had in mind was when I held down a button such as "A" then the motor would turn to the left keep moving till I let up on it. When I press "D" then the motor would move to the right until I let up. I would also like to have it so when I press a button such as "S" it would turn on a pin on the arduino for as long as I had it down. The stepper can only move 180 degrees. Any help on this code would be amazing and very helpful along with any other tips or suggestions.