Due "Keyboard" problem

I have a project that I have set up using a Mega for LEDs and a Leonardo for keyboard and mouse control. The sketches compile and work as they should. But I decided to simplify things by using a Due for both.
The combined sketch compiles when I select Leonardo on the Board menu , but not when I select Duemilanove . It asks if #include <Keyboard.h> is there , which it is - with Leonardo selected it compiles fine .
When I attached the Due to my computer using the Native port rather than the Programming port it asked me to download and install some things, so I did that , but the problem persists. I now have SAM Boards installed.
There is a USB Host Library for Due that I think I must need, it is not in my library , but I can only find USB Host Shield in the librarys offered online.
Is it possible/OK to use this?
Thanks.

Due is not the same as Duemilanove.

If I'm not mistaken, you'll have to install an additional board package to get support for the Due; see https://www.arduino.cc/en/Guide/ArduinoDue. Next select the Due as the board.

Hi , abject apologies , I assumed Due was an abbreviation. I had not seen the two Due port references at the bottom of board manager.