Why are not all the buttons responding while pressing them?Some buttons does not respond completely.
Answer to: Why is my screen black?There could be two problems that are causing this to happen regarding this question. The first one is that the calculator might be on high contrast and that is on the troubleshooting page, and here is the link for it that shows how it could be fixed. Casio FX-115MS The second problem might be because of a broken screen, and here is the link for it that shows how to fix it in the troubleshooting page. Casio FX-115MS