[HaBo]

# g++ -o FooMain FooMain.cpp
/tmp/ccSYd552.o: In function `main':
FooMain.cpp:(.text+0x8b): undefined reference to `Foo::Foo()'
FooMain.cpp:(.text+0x96): undefined reference to `Foo::get()'
FooMain.cpp:(.text+0xc9): undefined reference to `Foo::set(int)'
FooMain.cpp:(.text+0xd4): undefined reference to `Foo::get()'
FooMain.cpp:(.text+0x104): undefined reference to `Foo::~Foo()'
FooMain.cpp:(.text+0x11a): undefined reference to `Foo::~Foo()'
collect2: ld gab 1 als Ende-Status zurück

// FooMain.cpp
#include <iostream>

using namespace std;

#include "Foo.hpp"

int main()
{
	Foo f;
	
	cout << f.get() << endl;
	
	f.set( 5 );
	
	cout << f.get() << endl;
	
	return 0;
}

// Foo.hpp
class Foo
{
	private:
		int foo;
	
	public:
		Foo();
		~Foo();
		
		void set( int );
		int get();
};

// Foo.cpp
#include "Foo.hpp"

Foo::Foo()
{
	foo = 1;
}

Foo::~Foo()
{

}

int Foo::get()
{
	return foo;
}

void Foo::set( int i )
{
	foo = i;
}

g++ -o FooMain Foo.cpp FooMain.cpp