Natural data type ?

["Peter I. Hansen" <pih@oek.dk>]

Hello

I'm new to Ada and I'm reading a book by Feldman & Koffman.
Now I see that the datatype 'Natural' is the integers {0,1,2,3,4,...}, 
and type Positive is {1,2,3,4,5,....}. I know this is all akademic, but 
why this definition.
We learn in mathematics that the natural numbers are positive integers 
not including zero..., So to me the 'Natural' way of defining these 
datatypes would be :

Natural :  {1,2,3,4,5, ... }
Positive : {0,1,2,3,4, ... }

Am I all wrong here or have I stumbled across a misprint ???

/Peter