class

 1 #include <iostream>
 2 using namespace std;
 3 class  Box{
 4     private:
 5         double length;
 6         double width;
 7     public:
 8         void setLength(double length);
 9         void setWidth(double width);
10         double getLength();
11         double getWidth();
12         double getArea();
13 };
14 void Box::setLength(double length){
15     this->length = length;
16 }
17 void Box::setWidth(double width){
18     this->width =width;
19 }
20 double Box::getArea(){
21     return length*width;
22 }
23 double Box::getLength(){
24     return length;
25 }
26 double Box::getWidth(){
27     return width;
28 }
29 int main(){
30     Box box;
31     box.setLength(6.0);
32     box.setWidth(7.0);
33     cout<<box.getArea()<<endl;
34     return 0;
35 }