Billy contains many responses, which are programmed to be said if the user types in certain sequences of words.
Daisy contains no built-in responses.
She starts with no knowledge of anything, but then is able to gain knowledge as she observes what humans say. From this, she is able to remember patterns of words, and the probability of these patterns occurring. Using this data, Daisy is able to actually generate her own, original, sentences. She also figures out how to respond to user s input by analyzing what she has seen before she weeds out the unimportant words, and builds her response on the important ones. Since she has no pre-programmed responses, she can seem quite dumb when you talk to her after creating an empty memory file.