Why array index start with zero?why not from 1?

Answer 1

Two reasons:

1) Starting from 0 saves 1 bit, meaning you can represent a larger number with less bits.

2) In C++ the arrays decay to pointers, which is just a pointer to the first element, which would be array + 0.

Answer 2

because it is the distance from first character. this helps computer to access these locations faster

Answer 3

Since it's C++ explicit, that's the format that is designed when the language was made. However, the starting index for an array variable being 0 or 1 is all dependent on the language. Here is a somewhat comprehensive list of languages and whether their array indeces start with [0] or [1]. Cheers.

https://en.wikipedia.org/wiki/Comparison_of_programming_languages_%28array%29#Array_system_cross-reference_list