why index of arrays start from 0

Answer 1

It makes compilation easier.

Quoting from here
http://stackoverflow.com/questions/7320686/why-does-the-indexing-start-with-zero-in-c

Answer 2

Because.

Answer 3

It makes looping them easier. You can simply use:
for(int i =0; i < arr.length; i++)

If it started from 1 you would had to use this

for(int i=1; i < arr.length+1; i++)