My Iphone has a black screen but still vibrates and charges?

My iphone 4s is not working, it had a black screen but the vibrate button still works, so does the siri noise when i press and hold the home button down, i have tried the simple reset with on/off button and home button together, nothing happens, i tried plugging into my computer, the iphone comes up on itunes but my iphone still is black, it ...