I have found a new app Touch C in wp store. I think this is the best c language compilor in wp store... You can write program and execute it in app itself.....
Buy Lumia 1520 6inch phone...
My app is now free for limited period. Grab it if you already haven't :
touch C | Windows Phone Apps+Games Store (United States)
dude, can you add in c++ support, its been my primary language, and many schools use c++ or c# than just c.
Your app is very good!