Architecture and requirements for a Windows screen reader

Blind people have been successfully accessing standard applications on desktop computer systems using screen readers. These programs can echo user input and provide screen information to the user by using synthetic speech and/or a Braille display. This paper describes two aspects of screen readers. Firstly, it describes the mechanisms currently available for capturing the activities of the user and the user's application(s) that normally result in updates to the screen display. Secondly, the interface for presenting that information in an appropriate form to blind users is discussed. In both cases these are illustrated by reference to an ongoing project to produce a Windows (95, 98, NT4 and Windows 2000) screen reader for blind people, called Lookout. In the first instance this project only uses synthetic speech and, consequently, we do not discuss Braille output in this paper.