C++与C语言最大的不同

C++与C语言最大的不同在于：

C++的数据和函数封装在一起，因此无需参数传递数据！

下面看一个计算圆形面积的程序：

#include <iostream>
using namespace std;
class Circle {
public:
  double radius;
  Circle() 
   {
   	 radius = 1;
	} 
  Circle(double newRadius)
  {
    radius = newRadius;
  }
  double getArea() {//无形参，直接访问成员，与C语言最大的不同 
    return radius * radius * 3.14159;
  }
};

int main() {
  Circle circle1;
  Circle circle2(5.0);

  cout << "The area of the circle of radius " << 
          circle1.radius << " is " << circle1.getArea() << endl;
  cout << "The area of the circle of radius " << 
          circle2.radius << " is " << circle2.getArea() << endl;

  // Modify circle radius
  circle2.radius = 100.0;
  cout << "The area of the circle of radius " <<
          circle2.radius << " is " << circle2.getArea() << endl;

  return 0;
}