making and including header files in c++ on linux machine from terminal - c++

Question

To start, I'm very new to c++ and Linux, so if you could keep that in mind when you respond that would be great :)
I am trying to create a class in one file, that I will implement in the header of another file when I make an instance of that class.
My class file is
#include <iostream>
int main(){
class Box
{
public:
int _width;
int _length;
int _height;
};
}
I saved this as boxclass.h, but I did NOT compile it. I read somewhere that when I add this to my header file, I should just save it as a text file.
My other file, which I tried to include my box class in, is this:
#include <iostream>
#include "/home/cole/cpp/boxclass.h"
using namespace std;
int main()
{
Box outer{3,4,5};
Box inner{1,2,3};
Box newB = outer-inner;
cout << newB << endl;
}
When I try to compile this, I get these errors repeated many times with many different values
/home/cole/cpp/Boxclass.h:442:864: warning: null character(s) ignored
/home/cole/cpp/Boxclass.h:442:1: error: stray ‘\1’ in program
Can anyone explain to me whats going on?

Answer 1

You have two definitions for the main() {} function. That's not compliant for any c++ compiled code.
Further you have a local declaration of your class here:
int main(){
class Box
{
public:
int _width;
int _length;
int _height;
};
}
You don't want this, but an out of scope declaration of class Box appearing in a separate header file.
I'd suppose what yo want is
#include <iostream>
class Box {
public:
int _width;
int _length;
int _height;
};
int main(){
}