Linking problems

I'm doing a little test project. A simple interface for handling keyboard input in Windows, however I was getting a little problems for it to link. I made a simple program as follows:

Code:

#include <iostream>
#include "Input.h"

int main() {
    Input::vkeys[1] = true;
    if (Input::vkeys[1])
       std::cout<<Input::vkeys[1];
}

vkeys is a static bool array inside class Input in Input.h.
However, no matter what type of project it is, it says
[Linker error] undefined reference to `Input::vkeys'
Don't you usually get the when linking to libraries. There are no libraries as this is a header defined by me. What do I do to get it to link?
If you need Input.h and .cpp(for function declarations), just say so.

You need to define vkeys in your Input.cpp file.

Is Input.cpp being compiled/linked with the rest of your project or have you just been compiling the source file with your main function in it.

Input.cpp is in the project.

You need to define vkeys in your Input.cpp file.

I have vkeys defined in the header file, does it need to be defined in Input.cpp as well?

Yes... it is declared in the header file and defined in the source file. Something like this:

bool Input::vkeys[];