My iPhone 4 lost his display & also apple logo

Hi everyone!

I lost my iPhone display after picking a call, this time i using some apps and suffering WiFi. I all try my best via restarting iPhone with Home and Sleep button.But all is fail. Here is also a problem that when i restart my iPhone the apple logo also hide from begging. I need help to finding the real problem, is this problem by hardware or software? Please suggest me a good advice and take Thank in advance. Sorry for my poor English, its my beginner level.

Phone Spec:

iPhone 4 (Model: A1332)

iOS 7.1.2

Regard

Muhammad Shiraz Kamboh