[qorrect]

It acts as a terminator or terminal, see https://news.ycombinator.com/item?id=34391483.

[layer8]

If 0 would act as a terminator, then 1.203 would be equal to 1.2.

The thing that is actually special about the digit 0 is that it is implied for all positions for which no digit is given. That is, when we write

          1.2

we really mean

  …00000001.20000000…