Zero is neither positive nor negative because positive and negative is defined with respect to the position of the number from zero i.e. Left of zero on the number line is negative... and right of zero is positive...
Therefore... If the question says Positive Integer, it does not include zero! But if the question says "NON NEGATIVE INTEGER" then zero is included!
"Wherever you go, go with all your heart" - Confucius
1. How to Review and Analyze your Mistakes (Post by BB at GMAT Club)
2. 4 Steps to Get the Most out out of your CATs (Manhattan GMAT Blog)
My Experience With GMAT
1. From 650 to 710 to 750 - My Tryst With GMAT
2. Quest to do my Best - My GMAT Journey Log