c++ - can we make global variables by defining a class variable outside of the class with "dot" operator?

Question

class abc
{
    public:
    int x;
};

abc b1;

b1.x=10;

int main()
{

}

why can't we write this b1.x=10; outside of the main function? it shows error if we write b1.x=10; outside of the main function, why?

Answer 1

Because, b1.x=10; is an assignment statement which cannot be present at file scope.

You can, however, use initialzation to provide the initial values. Something like

abc b1 = {10};