How does a computer printer works?

When a text or image is entered into the CPU, it produces a series of varying voltages. This controls a LASER diode in the printer. This emits flashes of light which are directed by a rotating mirror scanning device to the precharged photoconducting drum, when it falls on the precharged photoconducting drum. The area corresponding the text or image will either be neutralized or oppositely charged. A plastic toner powder which has the same charge as the background is sprayed onto it. It only sticks to the text or image and is repelled by the background. A fresh paper is now pressed onto the toner. When the paper leaves the drum it is heated by the fixer so that the toner melts and sticks firmly on the paper.