First element in array

Question

Why do indexes in arrays always start with 0? Does it have something to do with binary? For example:

var myArray = [5,6,7,8];

To access the number 5, you would have to say

myArray[0]

But why?

No, I don't have a real problem. As you can evidently tell I'm new to this stuff.

Answer 1

I'm sure this has been asked an answered a hundred times, but I'll bite.

One way of looking at the "index" or "key" is as an "offset".

myArray essentially acts as a pointer to the first item in a series of items. Specifically, it points to the number "5" in memory. So when you say myArray[1] it's like saying "the location of the first element in myArray plus 1 item over", thus you would be jumping over the first element.

In C, when you write *myArray (pointer dereference) it actually gives you back the first element.

#include <stdio.h>

int main(void) {
    int myArray[] = {5,6,7,8};
    printf("%d",*myArray); // prints "5", equivalent to myArray[0]
    printf("%d",*(myArray+1)); // prints "6", equivalent to myArray[1]
    return 0;
}

There are more practical reasons than "that's the way computers work" too.

Answer 2

nice blog about the historical reasons: http://developeronline.blogspot.fi/2008/04/why-array-index-should-start-from-0.html