Huh? I thought digital was meaningless unless there is an agreement between sender and receiver? Analog gives information regardless of a receiver's understanding, and so is not a "coding format." Did I miss something?
This is a common misperception. In both cases you have to know the format. You have a carrier, which is the medium that you write your signal on. In electronics, this is frequently an electronic signal. Note that "analog" is used to mean different things. Information is encoded onto the signal any one of a hundred ways. Some methods are "digital", which serialize a piece of data as "bits", and some methods are "analog", which use various transforms on the carrier and similar to encode data. While it sounds like analog should carry more information ("instantaneous" values and all that), in practice they often carry much less. The reason is that analog systems are much more sensitive to noise, which causes the average information transmission rate to drop below that of digital formats in the real world. Not only that, but the faster you push the data, the worse analog systems perform. Still, at low data rates analog works pretty well.