On the off chance that your Mac is just showing the blue screen when you start up, or you can sign in however the work area neglects to show up, you may have an issue with your startup drive. The typical strategy is to run Disk Utility to endeavor to repair the startup drive, however you can't do that if your Mac doesn't begin, isn't that so? All things considered, this is what you can do.
At the point when a Mac neglects to fire up regularly, one of the normal investigating hones is to check and repair the startup drive.
A startup drive that is encountering issues is probably going to keep your Mac from beginning, so you may wind up in a dilemma. You have to run Disk Utility's First Aid apparatuses, yet you can't get the opportunity to Disk Utility in light of the fact that your Mac won't begin.
There are three techniques for getting around this issue.
Booting from an alternate source:-
This can be another drive that has a bootable framework on it, or your OS X Install DVD, which likewise contains the Disk Utility instruments, or the Recovery HD which is an extraordinary parcel on your startup drive that has been available since OS X Lion and later.
Protected Mode:-
This is an extraordinary booting strategy that powers your Mac to play out a programmed circle check and repair as it tries to fire up.
Single User Mode:-
This is another exceptional startup strategy that enables you to run order line utilities, for example, fsck, which can confirm and repair hard drives