[By analogy with the toyboxes on theatre organs].Features added to a program or system to make it more flavourful from a hacker' s point of view, without necessarily adding to its utility for its primary function.Distinguished from chrome, which is intended to attract users."Now that we' ve got the basic program working, let' s go back and add some bells and whistles."No one seems to know what distinguishes a bell from a whistle.[Jargon File]