定义一个类,计算长方体的体积

#include <iostream>
using namespace std;
class box
{
private:
 float length;
 float width;
 float height;
public:
 box(float a,float b,float c);
 void volume();
};
box::box(float a,float b,float c)
{
 length=a;
 width=b;
 height=c;
}
void box::volume()
{ 
 cout<<"长方体的体积是："<<length*width*height<<endl;
}
void main()
{
 
 float a,b,c;
 cout<<"请输入长方体的长：";
 cin>>a;
 cout<<"请输入长方体的宽：";
 cin>>b;