ExDOS is developed by Omar, “almost 14 years old”
Regarding learning assembly, I'm beginning to come to the view that it's in fact the best way to teach the first course in programming to kids. They don't come with any preconceived notions of what programming should look like and given an explicit, visual model of the computer, they quickly learn the small number of operations to write programs. More over, once they learn to do   LDA A
   ADD TWO
   STA A

   DAT TWO 2 <-- initializing variable TWO 


 then, this line of code

    A = A + 2

in C or a higher level language makes soooo much more sense. That awkward phase of internalizing that '=' is an assignment operator and is different from another operator meant to test equality gets a lot shorter for a beginner.Btw, this is the best online CPU simulator I've found for that use http://peterhigginson.co.uk/LMC/  I'm shocked at how all the code academies and hour of code's haven't created a polished version of LMC (Little Man Computer... look it up).