If your computer or laptop screen is dark but you can hear the sounds, try to shut down the computer gracefully. This situation can happen if you walk away from the computer for a few minutes and the computer tells the screen to go to sleep. Even though the computer is on, the signal to the computer screen is stopped and you’ll most probably see the computer screen’s power button flashing.

To shut down the computer gracefully, press the power button for a second and it will shut down gracefully. By gracefully, what I mean is that all of the applications open your computer at the time, will close normally and save anything that you are working on into the computer’s memory.
This ensures that when you boot up the computer, you can retrieve the work that you were working on.

If that doesn’t work, then you will be forced to do a hardware shutdown. This means that you must hold in the power button on your computer for more than five seconds.
The computer will turn off, but anything that you were working on, will be lost. It’s like pulling out the power plug of your computer. It is brutal and should be the last thing that you try.