Screen Reader/2: Access to OS/2 and the Graphical User Interface
Jim Thatcher · 1994 · Proceedings of the First Annual ACM Conference on Assistive Technologies (Assets '94) · doi:10.1145/191028.191039
Summary
This paper describes IBM Screen Reader/2, a screen access system that enabled blind users to interact with the OS/2 graphical user interface (GUI), Windows programs running under OS/2, and text-mode DOS and OS/2 programs. The system evolved from nearly a decade of development beginning with the SAID (Synthetic Audio Interface Driver) prototype created at IBM Raleigh in 1978, which used a modified 3377 terminal and a Votrax speech synthesizer. Screen Reader/2 was built on five core philosophical principles: blind users must have access to the same computing environment as sighted colleagues; certain information must be spoken automatically; users must be able to customize their system; interference between access software and applications must be minimized; and the GUI and text-based interfaces are fundamentally different ways of doing the same thing. The system used an independent 18-key keypad connected through the mouse port, avoiding conflicts between application keyboard shortcuts and screen reader commands. All functionality was programmable through the Profile Access Language (PAL), a Pascal-style scripting language that allowed users to define keypad functions, automatic speech triggers, and application-specific behaviors. The paper details how Screen Reader/2 tackled the fundamental challenge of GUI access: unlike text-mode displays where ASCII character data is stored directly in display memory, graphical displays contain only pixel data with no inherent textual information.
Key findings
Screen Reader/2 addressed the GUI accessibility challenge through an off-screen model (OSM) approach, intercepting drawing calls before they became pixels and recording text, position, color, font, and window handle information in a separate data structure. The system's key innovation was its "concept of view," which transformed graphical window contents into a familiar text-mode row-and-column format. Text strings within the foreground main window were sorted by baseline to create rows, with the maximum character length determining column count. This abstraction allowed all existing text-mode reading commands to work identically in the GUI environment. The system handled GUI-specific elements including menus (automatically adjusting the view when menus appeared), dialogs and controls (announcing control types, states, and associated prompts as users navigated with Tab and arrow keys), and provided mouse click emulation through the keypad. A Switch List feature allowed users to bookmark up to 15 windows for quick access, addressing the inherent difficulty of managing overlapping windows without visual cues. Over 30 application-specific PAL profiles were supplied, and the internal IBM discussion archives on Screen Reader contained over 140,000 lines of user feedback that shaped the product.
Relevance
This paper is a landmark document in the history of screen reader technology, authored by Jim Thatcher, one of the most influential figures in digital accessibility. The philosophical principles articulated here — particularly that blind users deserve access to the same computing environment as sighted peers, and that customizability is essential — remain foundational to modern assistive technology design. The off-screen model approach described became the dominant paradigm for GUI screen readers throughout the 1990s and into the 2000s, preceding the accessibility API approaches used today. The emphasis on user-driven development, with real blind employees testing and shaping the product through extensive feedback, presaged modern participatory design methodologies. For practitioners, this paper provides valuable historical context for understanding why screen readers work the way they do and how early design decisions continue to influence current assistive technology.
Tags: screen readers · graphical user interface · blind users · off-screen model · text-to-speech · GUI accessibility · IBM