I’m not parent, but for me the question is not literally why did they choose 1-based indexing. That’s easy to answer. The question is really: why haven’t they realized by now that the disadvantages of 1-based indexing far outweigh the benefits when it comes to programming, and changed it? Backward compatibility is a valid reason, but lots of other people have tried 1-based arrays and reverted to 0-based once it becomes clear that 1-based arrays causes more problems than it solves. Even humans who count starting from one will soon want to use 0-based the moment they need to add two array indexes together; we don’t want to have to start from 2 in that case, right? Early versions of the famous Numerical Recipes in C started with 1-based arrays, but removed them, and got slightly better. :P