What for & is used, how is it used in this code above?

Question

I don't quite get this, here is a simple program I picked from the internet written in C.

EXAMPLE 1.

int main(void) {

        char * b;

        memmove((char *)&b, "saaaa", 6);
        puts((char *)&b);

        return 0;
}

and here is my own code, EXAMPLE 2.

int main(void) {


    char b[10];

    memmove(b, "baaaa", 6);
    printf("%s\n", b);

    return 0;

}

Why is it using & in EXAMPLE 1 ? I have mostly used & sign when I want to assign a value to the variable like in scanf(). But in EXAMPLE 1, I am not assigning it. The only thing I do is I move the string saaaato the variable b.

And why using (char *) method is required any way?

The cast was included most likely to silence a diagnostic from the compiler. The first example is very broken. — FatalError, Oct 06 '15 at 15:43
@ameyCU: `puts()` takes a `const char *`. You'll get an error if you try passing a `char **`. — FatalError, Oct 06 '15 at 15:46
@FatalError Is it me, or the example doesn't even make sense. It is taking the address in memory of the pointer, instead of passing the pointer itself. — Corb3nik, Oct 06 '15 at 15:47
@FatalError Yeah , in `puts` but it will unnecessary in `memmove` . — ameyCU, Oct 06 '15 at 15:48
@Cubia: BLUEPIXY said it well. You could cram a string into the value of the pointer and treat it as if it were a `char[sizeof(char*)]`. But, I don't think I need to elaborate on why this is a questionable idea :) other than for entertainment purposes. — FatalError, Oct 06 '15 at 15:49

score 1 · Answer 1 · edited May 23 '17 at 11:44

The ampersand operator (&) is used in front of a variable to obtain the address of that variable. Doing &b will get the address in memory of b.

Here is a great SO post on when to use the ampersand : Pointers in C: when to use the ampersand and the asterisk?

Hope this helps.

EDIT : As FatalError has noted in the comments, your example seems broken. The best I can do is point you in the right direction on understanding these operators.

What for & is used, how is it used in this code above?

1 Answers1