Learn Spanish (Latin America): Si el teclado está sucio, hay que apagar la computadora. - If the keyboard is dirty, you have to turn off the computer.

In Spanish, when you talk about a real or likely situation using si (if), the verb right next to it must be in the present tense. This is true even if the second half of the sentence gives a command or talks about the future.

Can I put the si part of the sentence at the end instead?

Yes! You can flip the order without changing the meaning: Hay que apagar la computadora si el teclado está sucio. Notice that when the si clause comes second, you no longer need a comma to separate the two halves.

Why does the sentence use hay que instead of tienes que?

The English translation uses 'you have to', but hay que actually means 'one must' or 'it is necessary to'. It is an impersonal phrase used for general rules that apply to anyone. If you used tienes que, you would be telling one specific person that they need to do it.

Why is it está sucio instead of es sucio?

You use estar (here as está) to talk about temporary states or physical conditions. The keyboard is dirty right now, but it can be cleaned. If you used ser (es sucio), it would imply the keyboard is a fundamentally filthy object by its very nature!