I've never heard of D-code, or P-code, for that matter. That's not to say it might not exist, but if so, it's rare. Most the code that runs CNC machines is called "G-code". You can write it by hand for simple projects, but it's a lot easier to feed your models or drawings to a CAM program and let it do that. I don't think that control box has a keypad capable of writing code (of any type). The buttons on it will move the axes, or start and stop the spindle; that's about it. Your programs are written elsewhere, and loaded using the control software that came (or should have come) with the machine.