I was recently reading about the usage of
Never usein a function prototype for a parameter passed by
value. It has no meaning and is hence just 'noise'.
pass by value
pass by reference
The statement you quote is a bit misleading, because in C, all arguments are passed by value.* I suppose it is trying to distinguish between the arguments themselves and, for the special case of arguments that are pointers, their referents.
In any event, the point is that
const-qualifying a function parameter in the function declaration conveys no information whatever to callers. Regardless of such qualification, the function cannot modify the caller's copy of any argument anyway, because arguments are passed by value.
*Note, however, that arrays are never passed at all. In function call expressions, as in most contexts, array values "decay" to pointers, and those pointers are passed by value. This produces an effect similar, but not identical, to what you would have if arrays were passed by reference.