Build Error when Compiling - how to compile!

Hi,
I am a newbie!
I want to create a DevC++ project that will compile a few classes with their header files in the correct order!

Now I would like to understand something. Should all my class declarations be in a .h file and my class definitions be in a .cpp file?
example:

class Cat
{
private:
int age;
public:
Cat();
~Cat();
}

Now should I include the top class declaration in Cat.h?

how about the functions and methods for Cat class, do they go in my Cat.cpp?

example:

Cat::Cat()
{
cout<<Cat constructed!"<<endl;
}

Cat::~Cat()
{
cout<<Cat destructed!"<<endl;
}

does this code go in my Cat.cpp

do I include "Cat.h" in my Cat.cpp file?

now if i have a few more classes like this, how do i compile them all?

say iw ant to run everything from a main class, which only has my main method

please help.

thank you.

Yes to all your questions that can be answered with yes.