legOS · brickOS

A community replacement firmware for the RCX that runs native C/C++ on its Hitachi H8 (instead of LEGO's bytecode VM) — far more speed, memory and hardware control. Originally legOS (Markus Noga), later maintained as brickOS.

• Flashed in place of LEGO firmware; toolchain = an H8 GCC cross-compiler + a downloader over the IR tower.
• Ben Jackson's "VLL Transmit for legOS" shows an RCX emitting VLL under legOS to a Micro Scout / Code Pilot.
• Sibling alt-runtimes: pbForth (Forth), leJOS (Java).