To check if your [https://www.minitool.com/lib/random-access-memory.html|RAM] is working properly and how much RAM is installed on your computer, refer to these articles:
[https://www.techjunkie.com/check-ram-working/|https://www.techjunkie.com/check-ram-working/]
[https://www.computerhope.com/issues/ch000149.htm|https://www.computerhope.com/issues/ch000149.htm]
With your system on, disconnect all of your external devices. This includes your mouse, keyboard, '''external hard drive''', and so on. Restart your computer and see if you still get the black screen. If you don’t, plug each device in one at a time until you find what’s causing the problem.
As you have connected to an external monitor and screen is still black, it could be an issue with the video cable. You can try with a new cable. Make sure your cable supports the correct version of your display standard.