ld: symbol(s) not found
<p>I'm now studying <em>Fundamentals Of Data Structures in C++</em> written by <em>Ellis Horowitz</em>, trying to implement the example on the page 77. However, after I build the project, Eclipse Console shows up some warning.</p>

<p>Here's my header file:</p>

<pre><code>#ifndef RECTANGLE_H_
#define RECTANGLE_H_

class Rectangle{
public:
Rectangle();
~Rectangle();
int GetHeight();
int GetWidth();
private:
int xLow, yLow, height, width;
} ;

#endif
</code></pre>

<p>And here's my source file:</p>

<pre><code>#include &lt;iostream&gt;
#include "Rectangle.h"
using namespace std;

int main(){
    Rectangle r, s;
    Rectangle *t = &amp;s;

    if(r.GetHeight()*r.GetWidth() &gt; t-&gt;GetHeight()*t-&gt;GetWidth())
        cout &lt;&lt; "r";
    else
        cout &lt;&lt; "s";
    cout &lt;&lt; "has the greater area" &lt;&lt; endl;

    return 0;
}
</code></pre>

<p>And the CDT Build Console shows:</p>

<pre><code>Building target: rectangle
Invoking: MacOS X C++ Linker
g++  -o "rectangle"  ./main.o   
Undefined symbols:
  "Rectangle::Rectangle()", referenced from:
      _main in main.o
      _main in main.o
  "Rectangle::GetWidth()", referenced from:
      _main in main.o
      _main in main.o
  "Rectangle::GetHeight()", referenced from:
      _main in main.o
      _main in main.o
  "Rectangle::~Rectangle()", referenced from:
      _main in main.o
      _main in main.o
      _main in main.o
      _main in main.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make: *** [rectangle] Error 1

**** Build Finished ****
</code></pre>

<p>Besides, will binary files automatically created after building the project?</p>
