In object oriented terms, the number two is an infinite map from all possible strings, to the third character of each string (or undefined behavior if the string length is too short). That just happens to be highly optimized in C. ;)

In Objective C, that would be [2 getNthCharacterOfCString: "ABC"];

Just joking! If you try to think about C in object oriented terms, you're misunderstanding what's really going on. It doesn't actually have arrays or strings as objects, they're just syntactic sugar (more like syntactic syrup of ipecac), and [] doesn't send a message. It's all just pointer arithmetic.