1. how they are structured or visually represented
Analog audio used to come in vinyl disc form, generally surrounded by a thin cardboard sleeve.
Digital audio most commonly comes in aluminium disc form, with a plastic coating with a label on one side and surrounded by a plastic or cardboard case.
2. specific featured of each format
Analog audio could be scratched, bent, broken, heat & pressure damaged but had fantastic sound quality for the first few playings. It came in tube form, 33rpm disc, 45rpm disc and the older one which I can't remember if it was 72 or 83rpm.
Digital audio is read by laser and I'm not sure what speed it spins at.
3. process of converting analog to digital audio.
Simple - microwave. Same as the old non-foil chip packets made great keyrings. You can shrink any vinyl disc down to fit in a CD player.
And now for something completely different -
http://www.google.com.au/search?sourceid...vs+analog+audio