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Using just two digits for all your counting has amazing consequences. Computers only use these two digits, even when they appear to be doing complex things like displaying text, moving pictures or playing music. Yet all this complexity is based entirely on storing and shuffling around millions of sets of zeroes and ones.

Think of a simple light switch and how it jumps in one sudden click between off and on. If the switch is working properly, it doesn't hover somewhere between on or off - it is always one or the other.
This is very much how computers work - they use countless tiny switches, each one of which can be in only one of two states, on or off: these two states are used to represent values 0 or 1.

These simple concepts have other remarkable properties. Since all the information on a computer or digital device is stored purely as a stream of 0s and 1s, any copy we want to make is just a matter of copying these numbers. If you have a long stream of digits such as 110100101000111.... and so on, you can copy them without any loss of information simply because of the redundancy of the digital system -  we don’t know and don’t care what the precise value of each 1 or 0 is in our computer as long as it can separate them.

Compare this with the earlier analogue example. In analogue photography, the values of colours and shades are not stored as numbers but as chemical reactions. The photograph, however good, is flawed. But it gets worse if we try to re-photograph the photograph.
Not only will we have the original photograph's faults, but our copy will have faults of its own added. Repeat this process and you end up with a badly degraded picture. Repeat enough times and the image will disappear altogether. (Technically, we would describe this as the signal being swamped by noise.)

Digital copies, on the other hand, can be duplicated down through many generations of copies without degradation. (Of course, even in the digital world, devices can fail and the signal may eventually become corrupted, but the problems are as nothing compared to those in the analogue world.)

Which leaves the question: why does it matter whether or not we can copy media almost perfectly?

First, as an animator, you should realise that your craft has absolutely no existence other than in the reproductive media. That is a pompous way of saying that animation can only be passed on from animator to viewer by using some medium such as video or film or internet connection etc. You can’t actually pick up and hold animation – it only exists in those media. Every medium we use requires audio-visual information to be copied and transferred, so that is why doing it well is important.

Another reason is that every picture or sound process that involves editing or layering, (for instance in mixing a record down from 64 tracks), involves copying signals, sometimes many times over. As we have seen above, neither analogue nor digital processes can ever copy perfectly, but only digital allows us to keep copying generation after generation without losing the signal under a blanket of noise.

On the subject of noise - as a postscript we'll see how exactly the same principles that describe digital imagery are used in digital sound...

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