A computer can be used without a monitor. Screen reader software makes the screen display available as synthesized speech.
People who are blind might not have a monitor. They often use a screen reader or a Braille display rather than a monitor. Although most screen readers are a software package that makes on-screen information available as synthesized speech, there are other screen reading devices that involve some hardware equipment. A Braille display shows the on–screen information as a refreshable Braille sequence.
Generally, screen readers and Braille displays can only translate information that is text. But as you will see in the following sections, it's possible to add text descriptions to graphics on Web pages that screen readers can translate.
But no matter how good a screen reader is, there are still several things that you must do to your documents so that screen readers can work successfully.