My computer turns on, but the screen stays bl

Hello, when I turn on my computer, it turns on and so does the screen. BUT the screen stays black, you can see that the screen is on, but nothing shows up but a black screen. Everything is on, but the screen just stays the same. I've tried to just leave it for a couple hours to see if it'll show up, but it stays the same as always. Help? I don't know if it's just because it's an old computer but it was working perfectly fine, till the next day when I turned it on.