Simple: Because you add zero to the memory address of an array to access the first element.
The array indexer was syntactic sugar for pointer arithmetic.
Why do arrays start at 0?
161–170 of 702 posts
Re: Why do arrays start at 0?
#162Looking at my own coding experience, I certainly favor 0 over 1. When I examine why, I can't help but see my aversion to & distaste of Visual Basic as a driver.
VB is the only 1-indexed language I have used. VB is bad. Therefore 1-indexed languages must be bad.
Re: Why do arrays start at 0?
#163The article this one points to has had a few threads: The origin of zero-based array indexing - https://news.ycombinator.com/item?id=6879478 - Dec 2013 (107 comments) Zero-based arrays and the mythology of programming - https://news.ycombinator.com/item?id=6708409 - Nov 2013 (1 comment) Citation Needed - https://news.ycombinator.com/item?id=6595521 - Oct 2013 (2 comments) Threads about the EWD mentioned by jaapsen01:…
Perhaps also worth adding that the linked article (the one titled "Citation Needed") itself originally had hundreds of comments beneath it, many quite argumentative, which seem to be now missing - I guess lost in a site update. It was a very contentious article.
I'm sympathetic to its author's approach - we talk about indexing and it's a strangely fascinating topic but the history of it hasn't been all that well dug out. We do indeed tend to respond to articles like this by going "well obviously [x]-based is good because" - you can see that at work in this discussion here - but those are not necessarily the true historical reasons. But I think the author made a leap too far, the article was a bit too brittle, and it landed in a slightly too argumentative spot.
Re: Why do arrays start at 0?
#164Actually in not all languages do arrays start at 0. In ColdFusion for example arrays start at 1. I've never been able to receive a reason as to why CF's original author, J.J. Allaire, did it that way.
Re: Why do arrays start at 0?
#165Other advantages of zero based indexing, beyond being 'closer to the machine': It works better with the modulo operator: `array[i%length]` vs `array[(i+length-1)%length+1]`. Or you would have to define a modulo-like operator that maps ℕ to [1..n]. It works better if you have a multi-dimensional index, for example the pixels in an image. With 0 based indexing, pixel `(x,y)` is at `array[x+width y]`. With 1 based index…
A disadvantage comes to mind. While the following loop works as expected: for (size_t i = 0; i The following causes an unsigned integer underflow and is an infinite loop: for (size_t i = length - 1; i >= 0; i--) ...
As Jens Gustedt points out[1], the following intentional unsigned overflow works perfectly for downwards iteration (even when length is 0 or SIZE_MAX), though it looks a bit confusing at first:
for (size_t i = length - 1; i [1] https://gustedt.wordpress.com/2013/07/15/a-praise-of-size_t-...
Re: Why do arrays start at 0?
#166Earlier quoted context omitted.
> when we count, we start at 1, we talk about the "1st" Although often with an implicit zero. Under typical North American culture, your 1st birthday, for example, is more accurately the first anniversary of your birthday. Your birth is zero indexed.
That's why I prefer the Superior(TM) Korean age counting. You are one year old when you're born (it's your first year!). You are two year old on the next New Year's day. (Congratulations, it's your second your now!) So, if you're born on December 31st, you're two years old the next day. (I see no problem, but apparently some people are hung up on such minor details. I can't fathom why.)
> You are one year old when you're born (it's your first year!)
That makes no sense to me. It's also your first century. Does that make you one century old? Of course not! The moment you're born, you're not even one hour old, let alone one day.
Re: Why do arrays start at 0?
#167Dijkstra's answer (linked in the article) is best: "When dealing with a sequence of length N, the elements of which we wish to distinguish by subscript, the next vexing question is what subscript value to assign to its starting element. Adhering to convention a) yields, when starting with subscript 1, the subscript range 1 ≤ i https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E...
I don't understand why 0 ≤ i ≤ N wouldn't have worked instead, since you already have a less than or equal operator at 0.
Re: Why do arrays start at 0?
#168If you ask people which floor of building they're on, it's going to depend on which country they're in. In North America, at least, the first floor you walk into (in a sane city: I understand there are some which do not qualify in this respect due to hills or historic disaster recovery) is the first floor. On other continents, you enter the ground floor and need to take stairs or an elevating device to get to the first floor.
"Natural" zero-based counting at its best.
Re: Why do arrays start at 0?
#169Edsger Dijkstra wrote an interesting article titled 'why numbering should start at 0'. Perhaps not answering the question directly but an interesting read nonetheless. https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E...
I've never understood the first half of Dijkstra's argument. Unless we are programming a theoretical Turing machine, there will also be a maximum number that can be represented, so the argument about using inclusive bounds for the lower end also applies to the the upper end. So you can't represent all numbers with a single range style. You either end up excluding the smallest number, the largest number, or the empty set. Or you need special notation to handle one of those three cases.
I suppose the 0,1,infinity principle argues that including the empty set and smallest number is more important that including the largest number, so that notation should be preferred by default. And when writing using A<=i<B it is clear enough, but once you remove those symbols and start using them in indexing or function call syntax, like [A:B] or range(A,B), the inconsistency of bounds really breaks my brain, and having to pass a number larger than the largest array index as an upper index range bound gives me nervous ticks. I'd rather use inclusive bounds everywhere and have special syntax for empty set.
Re: Why do arrays start at 0?
#170Worst than 0 and 1 is to have the choice. In Visual Basic 6 you have the option between the base 0 or 1 for each module. It make debugging a nightmare and you can create bug just by copy/pasting code from one program to other with a different base index.