An array “decays” into a pointer to its first element, so scanf(“%s”, string) is equivalent to scanf(“%s”, &string[0]). On the other hand, scanf(“%s”, &string) passes a pointer-to-char[256], but it points to the same place.
Then scanf, when processing the tail of its argument list, will try to pull out a char *. That’s the Right Thing when you’ve passed in string or &string[0], but when you’ve passed in &string you’re depending on something that the language standard doesn’t guarantee, namely that the pointers &string and &string[0] — pointers to objects of different types and sizes that start at the same place — are represented the same way.
I don’t believe I’ve ever encountered a system on which that doesn’t work, and in practice you’re probably safe. None the less, it’s wrong, and it could fail on some platforms. (Hypothetical example: a “debugging” implementation that includes type information with every pointer. I think the C implementation on the Symbolics “Lisp Machines” did something like this.)
I think that this below is accurate and it may help.
Feel free to correct it if you find any errors. I’m new at C.
char str[]
array of values of type char, with its own address in memory
array of values of type char, with its own address in memory
as many consecutive addresses as elements in the array
including termination null character ‘