VIOS Manual

VIOS Manual

VIOS is a small, malleable operating system for the Agon Light 2, built around a resident Forth. You type Forth at a console on the VGA screen or drive the same system from a Mac; you browse, edit and replace running code in Smalltalk-style windows; and you keep what you build as checked source modules on the SD card.

The VIOS desktop right after boot: the Console window on the dithered Smalltalk desktop
The VIOS desktop right after boot: the Console window on the dithered Smalltalk desktop

This manual covers building VIOS from source, installing it, setting it up and using it: the console, the Forth language as VIOS implements it, modules, tasks, files and devices, the GUI and its tools, sound, and the host tools. It ends with example programs and a reference of every word.

Edition: VIOS 0.8.0, October 2026 (the version is in the VERSION file; what changed is in CHANGELOG.md). All screenshots are rendered on a host computer by the real VIOS display server and GUI code (see Images in this manual); the board draws the same pixels.

Contents

  1. Introduction
  2. Architecture
  3. Hardware and Wiring
  4. Building
  5. Installing
  6. First Boot and Setup
  7. The Console and REPL
  8. The Forth Language
  9. Display and Graphics
  10. Modules and Persistence
  11. Tasks and Preemption
  12. Handles, Pipes and Devices
  13. Files and the SD Card
  14. The GUI
  15. The GUI Tools
  16. Audio
  17. The Host Harness and MCP Tools
  18. Troubleshooting
  19. Example Programs
  20. Word Reference
  21. Appendix: Limits and Numbers