How to know if I cracked the LCD on my Iphone; or not, when I cracked my screen?

I dropped my iphone 4S and cracked the screen pretty bad. The screen still works perfect. I need to buy a replacement glass lens. Before I do that I need to know if the LCD on the screen is broken but I have no idea what that means. Any insight would be appreciated.

The LCD is actually the part that displays the screen, it contains the pixels. So if the screen still works, you didn't crack the LCD. If you had cracked the LCD, there would be parts of the screen that would be black or the wrong color, etc.