685: Mainline

Thus, you can divide the box and cylinder class definitions into two files: a header file and a source-code file:

// containers class definitions (h extension) 
  
  
// box class definition: 
  
class box { 
  public: double height, width, length; 
    // Prototypes: 
    box ( ) 
    box (double, double, double) 
    double volume ( ) 
}; 
   
  
// cylinder class definition 
  
class cylinder { 
  public: double radius, length; 
    // Prototypes: 
    cylinder ( ) 
    cylinder (double, double) 
    double volume ( ) 
}; 
// Containers source-code file (cxx extension) 
  
#include "containers.h" 
const double pi = 3.14159; 
  
box::box ( ) { } 
box::box (double h, double w, double l) { 
  height = h; width = w; length = l; 
} 
double box::volume ( ) { 
  return height * width * length; 
} 
  
cylinder::cylinder ( ) { } 
cylinder::cylinder (double r, double l) { 
  radius = r; length = l; 
} 
double cylinder::volume ( ) { 
  return pi * radius * radius * length; 
} 

You can, of course, divide the railroad-car class definitions into header and function files as well.