#include <iostream> using namespace std; // 变量声明 extern int a, b; extern int c; extern float f; int main () { // 变量定义 int a, b; int c; float f; // 实际初始化 a = 10; b = 20; c = a + b; cout << c << endl ; f = 70.0/3.0; cout << f << endl ; return 0; }