user created libraries

[Nobody/Anonymous]

I'm new to using user created libraries on dev-cpp, and I've been getting some errors, so I would like to make sure I'm doing things right. first...
.h file-
#ifndef mylibrary_h
function declarations
#define mylibrary_h
#endif

right?
now standard protocol is for the mylibrary.cpp file to include the mylibrary.h file, and for the driver to include the mylibrary.cpp file. I try this, but I get linking errors. Also, I put my files in the "include" folder. Is this correct?

[Nobody/Anonymous]

Once I include my .h file, it says I have an unterminating #if statement and garbage at the end of my #ifndef statement.

[Nobody/Anonymous]

This is not mine. Just wanted to give something to go by.
Hope it helps.

#ifndef BOX_H
#define BOX_H

class Box
{
  public:
    // Constructor
    Box(double lengthValue = 1.0, double breadthValue = 1.0, double heightValue = 1.0);

    // Function to calculate the volume of a box
    double volume();

  private:
    double length;
    double breadth;
    double height;
};

#endif

    Larry

[Nobody/Anonymous]

Note:

// Constructor
Box(double lengthValue = 1.0, double breadthValue = 1.0, double heightValue = 1.0);

and -

// Function to calculate the volume of a box
double volume();

These two are defined in another file.  'Box.cpp'.

  Larry

[Nobody/Anonymous]

Here is the other file that has the definitions.

#include <iostream>
#include "Box.h"

using namespace std;

// Constructor definition using an initializer list
Box::Box(double lvalue, double bvalue, double hvalue) : length(lvalue),
                                                        breadth(bvalue),
                                                        height(hvalue)
{
  cout << "Box constructor called" << endl;

  // Ensure positive dimensions
  if(length <= 0.0)
    length = 1.0;
  if(breadth <= 0.0)
    breadth = 1.0;
  if(height <= 0.0)
    height = 1.0;
}

// Function to calculate the volume of a box
double Box::volume()
{
  return length * breadth * height;
}

  Larry