Why cant I use my touch screen?

[AC Question]

I have never dropped my phone and it has never been near water. I just went to use it and for some reason, it wont let me put my code in to open it. Its like my touch screen don't work. I reset the phone but it didn't do anything.

 

[B. Diddy]

Welcome to Android Central! Tech components sometimes just fail, or are defective. Which phone do you have, and is it still under warranty?