It's debatable, technically it does start with a vowel so "an" should be used, but since it starts with a Y consonant sound, using "a" sounds a lot better and may also be considered correct/better.
Modern USB keyboards need to be asked what's being pressed by the CPU multiple times a second, but old PS/2 keyboards will actually interrupt the CPU to send the key press command
Looks like you're missing the cup there mate 😬