It seems like you erased the system files and now your Mac is unable to find the system files to load. If you are trying to erase the Mac and install fresh OS X, then follow the steps below;
Turn off your Mac by holding down Power button for 5-10 seconds. Turn on your Mac and immediately hold down Command and R keys at the same time for 15 seconds and this will boot your Mac to the Mac OS X Utilities screen. If that didn't boot into OS X Utilities screen, then restart and immediately hold down Command, Option and R keys at the same time for 20 seconds and this will boot into OS X Utilities screen.
If you want to erase the Mac, then click Disk Utility in OS X Utilities screen. In Disk Utility, select your hard disk in left column which would be Macintosh HD or Mac HD (the second one in the list). Select it, click on Erase tab and click Erase button. Then close Disk Utility.
Click Reinstall OS X and follow the onscreen instructions to reinstall it.
If you don't want to erase the Mac, then don't use Disk Utility to erase it. Instead, click Reinstall OS X.
Please let me know if that didn't work, so we can continue troubleshooting.