Why declare a struct that only contains an array in C?
It allows you to pass the array to a function by value, or get it returned by value from a function.
Structs can be passed by value, unlike arrays which decay to a pointer in these contexts.
Another advantage is that it abstracts away the size so you don't have to use [MAX] all over your code wherever you declare such an object. This could also be achieved with
typedef char ABC[MAX];but then you have a much bigger problem: you have to be aware that ABC is an array type (even though you can't see this when you declare variables of type ABC) or else you'll get stung by the fact that ABC will mean something different in a function argument list versus in a variable declaration/definition.
One more advantage is that the struct allows you to later add more elements if you need to, without having to rewrite lots of code.
You can copy a struct and return a struct from a function.
You cannot do that with an array - unless it is part of a struct!