My mac bookpro screen hangs and freeze after restarting it displays black screen I bought macbook pro-13 inches last year September, since last 15 days I'm facing difficulties regarding to booting issues and also some times suddenly the display hangs no controls, keys, trackpad not working the display just hanged. 

After restarting the device by long pressing power button and power on it after some time some times it shows some black lines appearing on screen after 30 seconds they disappear and turn into black screen sounding 3 beeps. 

Last week I've consulted authorized dealer for service they just formatted my system and told me there is no problem regarding to hard-disk drive, RAM and logic board. But I'm facing this problem daily...Please tell the exact reason, and what should i do to it work properly.
The 3 beep sounds indicate problem with your EFI.

EFI is located on your disk in a hidden partition and is mainly responsible for booting and other key functions.

It is possible you do have a disk error (even if the "authorized dealer") did not find anything. I would suggest you use the Disk Utility and check your disk again and while at it repair the permissions.

Check your version.

How to repair EFI: Find your EXACT model here.

http://support.apple.com/downloads/#macnotebooks