"Una computadora" is one of the regional expressions for "computer". Others can be "un computador", or "un ordenador".
Is there a computer in your class?
As a statement it means "you have a computer" As a question it means "Do you have a computer?"
¿Tiene usted un ordenador/una computadora? -formal ¿Tienes un ordenador/una computadora? -informal
Es sólo una computadora.
"Is there a computer in your class?"
To say 'I want a computer' in Spanish, you would say 'Yo quiero una computadora.'
You say, "Trabaja por una empresa computadora."
the student (female) wants a new computer.
La disquetera es el dispositivo o unidad lectora/grabadora de disquetes.
The statement is "Fernando has a computer". If he has one, you would say "sí". If not, you would say "no".
You use the computer.