error message, what does it mean?

I keep getting this error message every time I compile my program. I compile my program like this: CC filename.cc filename.cpp because I'm dealing with classes and I keep getting this error message:
Id: warning: file rectangle.o: attempted multiple inclusion of fil
Undefined first referenced
symbol in file
main /opt/SUNWspro/SC5.0/lib/crt1.o
Id: fatal: Symbol referencing errors. No output written to a.out

looks like you tried to use something without it being defined. Post some code. Could just be a spelling error.

I got the same error message with two of my programs. Here's the first program:
//header file

#ifndef LAB8_H
#define LAB8_H

//creates class
class RaceCar {
private:
int car_num;
double tank_size;
int max_speed;
static int CarCount;
public:
void display();
RaceCar();
void input(int, double, int);
static void ShowCarCount();
};

#endif


//member functions definitions

#include <iostream>

using std :: cout;
using std :: endl;
using std :: cin;

#include "lab8.h"

void RaceCar :: display () {

cout << "Car number: " << car_num << endl;
cout << "Tank size: " << tank_size << endl;
cout << "Max speed: " << max_speed << endl;
}
int RaceCar :: CarCount = 0;

RaceCar :: RaceCar () { ++CarCount; }

void RaceCar :: ShowCarCount () {

cout << "Car Count: " << CarCount << endl;
}
void input (int num, double size, int speed) {

cin >> num >> size >> speed;

}


#include <iostream>

using std :: cout;
using std :: cin;
using std :: endl;

#include "lab8.h"

int main ()
{

RaceCar r;

r.input(2, 20, 200);
r.display();
r.ShowCarCount();

return 0;
}

Here's my second program:
#ifndef RECTANGLE_H
#define RECTANGLE_H

class Rectangle {
private:
double length;
double width;
double length2;
double width2;
public:
Rectangle(double = 0.0, double = 0.0, double = 0.0, double = 0.0);
double perimeter (double, double);
double area (double, double);
void set_rectangle (double, double, double, double);
double get_length();
double get_width();
double square (double, double, double, double);
};

#endif

//member function definitions for Rectangle class

#include "rectangle.h"

Rectangle::Rectangle(double l, double w, double ll, double ww) {

set_rectangle(l, w, ll, ww);

}
void Rectangle::set_rectangle (double l, double w, double ll, double ww) {

length = (l >= 0.0 && l <= 20.0) ? l : 0.0;
length2 = (ll >= 0.0 && ll <= 20.0) ? ll : 0.0;
width = (w >= 0.0 && w <= 20.0) ? w : 0.0;
width2 = (ww >= 0.0 && ww <= 20.0) ? ww : 0.0;

square(l, w, ll, ww);
}
double Rectangle::get_length() { return length; }

double Rectangle::get_width() { return width; }

double Rectangle::perimeter (double l, double w) {

length = l;
width = w;

return ((2 * 1) + (2 * w));
}
double Rectangle::area (double l, double w) {

length = l;
width = w;

return (l * w);
}
double Rectangle::square (double l, double w, double ll, double ww) {

length = l;
length2 = ll;
width = w;
width2 = ww;

if (((l != w) && (ll != ww)) && ((l == w) && (ll == ww)))
return 0;
else
return 1;

}

//main function

#include <iostream>

using std :: cout;
using std :: endl;

#include "rectangle.h"
int main () {

Rectangle r;

if((r.square (8.0, 2.4, 8.0, 2.4)) == 0) {
cout << "Perimeter is: " << r.perimeter (8.0, 2.4) << endl;
cout << "Area is: " << r.area (8.0, 2.4) << endl;
}else {
cout << "It's not a rectangle" << endl;
}

return 0;
}

In your first program you forgot to scope the input function in the definition of it.

should be
void RaceCar::input( blah blah blah)
{
// more code
}


I'm working on the second now

second one compiled just fine for me.
Sorry.