iPhone 4s screen not working My iPhone 4s abruptly stopped working, and the display is now completely useless. The display shows small stripes when turned on. Can somebody help/explain why this happens?
Possible hardware issue with the device.  Try a force restart by holding the power and home buttons together for ~10 seconds until you see the Apple symbol appear on the screen.  If you don't see the Apple symbol or it reverts to the blank screen with vertical lines on it, then the next step would be to complete a recovery mode restore.  

Recovery mode restore involves connecting the device to a computer with the latest version of iTunes on it and completing the same restart with the device connected via USB and iTunes open.  The steps can be found here:  https://support.apple.com/en-us/HT201263

If the issue continues after restoring the device to factory settings then you would want to look into hardware service for the device.