Find functions' actual code?

Is there a way (or a place) where i could find the code that is executed when a function is called? I want to see what code is executed when i call the UnitAddAbilityBJ function, specifically. Or are these functions not actually defined in JASS, but some lower-level language?

If you use UnitAddAbilityBJ you can indeed find its code however its very lackluster:
function UnitAddAbilityBJ is found inside Blizzard.j
But it calls the native UnitAddAbility. Natives are functions whose code bodies are not exposed anywhere in script and are part of the warcraft III game engine.

sad... :(

sad... :( (eep! double post! sorry, it was an accident....)