I have a program that has 3 global variables, 2 functions f() and g() and a main.

It looks like this:

int a, b, c;
int f(int x)
{
    return a * x;
}
int g()
{
    int c;
    c = a;
    a = b;
    b = c;
    return c;
}
int main()
{
    int x, y;
    a = 2;
    b = 3;
    c = 4;
    x = f(a);
    y = g();
    printf("%d %d %d %d %d\n", x, y, a, b, c);
    return 0;
}

I know that in the g function since a c variable is declared then the c used inside of it is the new c and not the global variable.

But what I do not understand is why g() was able to modify the global variables.

Can't we only modify variables using pointers in these situations?

I don't really understand why a and b were swapped, my printf gives me: 4 2 3 2 4

Thanks

CodePudding user response：

Global variables can be accessed directly, there is no need to use pointers.

As for why a and b were swapped, look at your g function:

    local_c = a // this is equal to 2;
    a = b // this is equal to 3;
    b = c // this is eqaul to 2, originally a;

CodePudding user response：

Global variables have a global scope, meaning they can be accessed and modified anywhere throughout the program. And in this case there is no need to use pointer .

And to see why a and b where swapped you should check out your g function :

 c = a // now c = 2 ;
 a = b // now a = 3 ; a get the amount of b ; 
 b = c // now b = 2 ; now b get the first amount of a and it is clear a & b are exchanged ;