Here's a stupid little thingy for those of you who like to play with Petit Computer for DSi. It's a program that "goes" or "stops" depending on button input. It's not terribly fun to play, but if you want some code to look at to figure out determining button input, this program is for you. You may "download" it with your DSi or 3DS by using the QR Code shown below.
Here's some example code that may help you with programming for the touch screen. If you run the progran for a few seconds, you'll probably figure out what's going on, and then hopefully understand the code. Basically, it's an infinate loop that detects if the screen is being touched, and then displays the touch coordinates. Press A to break out of the loop and exit.