Auto is the implicit default right? As in function scoped, stack allocated, and lives until the function is returned?
K&R (Second Ed). Makes no mention of the auto keyword in Section 1.10, but it does say,
> Each local variable in a function comes into existence only when the function is called, and disappears when the function is exited. This is why such variables are usually known as automatic [sic] variables[...]
yes, exactly. That's why there is no need for it in modern c. This compiler however is different: The type is optional (and assumed to be int). Say you have a variable declaration "auto int i;". Back then you could omit int, now you can omit auto.
"auto" probably is the storage class, it tells what kind of variable this is. Automatic as opposed to "register" which would force the variable to be a register, or "static" or "extern".
The type is not given at all, I think by default it would be "int".
One of the unusual things in this early version of C is that "int" can be used for any word-sized value, including pointers. The type system was very loose.
Even back then this was considered poor practice, however. The first edition of K&R had a subsection entitled "Pointers are Not Integers" (I don't know if that's still in modern editions).
It looks to me like that section was removed in the 2nd edition. Some sections moved around, so maybe I'm just looking in the wrong place, but it's not nestled between "5.5 Character Pointers and Functions" and "5.7 Multi-Dimensional Arrays" like it is in the 1st edition.
The interesting thing for me is that a variable without a type annotation could potentially store anything. It kind of explains why the language used "int" as the default type of variables declared without a type annotation.
No. "auto" is not a type but a storage class that means automatically allocated instead of being allocated to a register, extern-al to the file, or in the static code segment.
