learn c++ 变量作用域

#include <iostream>

int a{ 100 };
int main()
{

    int a{160};
    {
        std::cout << a << std::endl;

        char a = 'a';
        std::cout << a << std::endl;

        std::cout << ::a << std::endl;
    
    }
    std::cout << a << std::endl;


}