3 ms·

I don't get it. CD is digital isn't zero always zero and one is always one? Are there no checksum or some other methods that ensure that the data is read in cor

• ColonelBlimp 4y ago
  I suggest you read adql's response below. Also copied here just in case: "There is no "digital data" in physical reality. There is "analog data that is within a threshold of the bit that we decided". Hard drive or CD doesn't read "1" or "0", it reads say (after normalization) 0.823V. Or 0.654V. Or 0.983V. The way circuit is designed decides that above some value its "1", below that is "0", but physical deterioration and material variance will change that value and it will differ bit by bit too. It's all good when signal is strong and say all the 1's are > 0.8, all the 0's are < 0.2 but when it starts to blur (again, bad media, degradation etc.) you get bits that can be 1 one read, 0 another. And having "tri state" input that can say "ok, it's between 0.4-0.6, we can't tell whetehr that's 0 or 1" is generally rare."