A Mathematical Theory of Communication

Before Shannon, 'communication' was treated as an engineering problem specific to each medium — telephone static was a phone problem, radio noise was a radio problem. Shannon showed that any message, whether text, sound, or image, could be broken down into a stream of bits (his paper popularized the term, suggested to him by colleague John Tukey), and that the real question was always the same underlying math problem: how much information can you reliably squeeze through a channel that has some amount of noise, and how do you protect a message from that noise. He proved there's a hard ceiling (channel capacity) on how much information can pass through reliably, but that below that ceiling, clever encoding can make the error rate as close to zero as you want.