29.【c++全局变量的定义和引用】

#include

using namespace std;

int a = 10;

int main()

{

 int a = 3;

 cout << "局部变量a的值是:" << a << endl;

 ::a;

 cout << "全局变量a的值是:" << ::a << endl;

 int c;

 c=(a += a);

 cout << "局部变量a的和为:" << c << endl;

 int d;

 d = (a += ::a);

 cout << "改变后的局部变量a（即做了加法后）与全局变量a的和为:" << d << endl;

 return 0;

}