The Penguin Class example illustrates the use of Interfaces to implement multiple inheritance.
In this case, the Penguin Class derives from Animal but additionally supports the BirdBehaviour and FishBehaviour Interfaces, thereby inheriting members from both.
Pingo←⎕NEW Penguin ⎕CLASS Pingo #.Penguin #.FishBehaviour #.BirdBehaviour #.Animal (FishBehaviour ⎕CLASS Pingo).Swim I can dive and swim like a fish (BirdBehaviour ⎕CLASS Pingo).Fly Although I am a bird, I cannot fly (BirdBehaviour ⎕CLASS Pingo).Lay I lay one egg every year (BirdBehaviour ⎕CLASS Pingo).Sing Croak, Croak!