Why does the indexing start with zero in 'C'?

Question

Why does the indexing in an array start with zero in C and not with 1?

Answer 1

The most elegant explanation I've read for zero-based numbering is an observation that values aren't stored at the marked places on the number line, but rather in the spaces between them. The first item is stored between zero and one, the next between one and two, etc. The Nth item is stored between N-1 and N. A range of items may be described using the numbers on either side. Individual items are by convention described using the numbers below it. If one is given a range (X,Y), identifying individual numbers using the number below means that one can identify the first item without using any arithmetic (it's item X) but one must subtract one from Y to identify the last item (Y-1). Identifying items using the number above would make it easier to identify the last item in a range (it would be item Y), but harder to identify the first (X+1).

Although it wouldn't be horrible to identify items based upon the number above them, defining the first item in the range (X,Y) as being the one above X generally works out more nicely than defining it as the one below (X+1).