leJOS

A tiny Java virtual machine as RCX replacement firmware (grew out of TinyVM) — write robot code in Java (threads, objects) and download the classes over the IR tower.

• One of the three classic alt-runtimes alongside legOS · brickOS (C) and pbForth (Forth).
• leJOS later became the major NXT (leJOS NXJ) and EV3 Java platform; "leJOS RCX" is the original generation.